Rubbers are prone to aging under impact. Rubber products care and storage

16.07.2019

Engine

Tires play important role in the handling and safety of the car, however, with age, they lose their qualities and must be replaced with new ones. Therefore, every driver should be able to determine the age of tires and produce them. timely replacement. About why it is necessary to change old tires, how to determine their age and replacement time, read in this article.

Tire Life Standards

Tires are one of the few car components that not only undergoes wear and tear during operation, but is also subject to natural aging. Therefore, tires are replaced not only due to their critical wear or damage, but also when the service life exceeds the allowable. Too old tires lose their qualities, elasticity and strength, and therefore become too dangerous for the car.

Today in Russia there is a contradictory situation with the service life of tires. On the one hand, the so-called warranty period of service (service life) of automobile tires is established by law in our country, equal to 5 years from the date of their production. During this period, the tire must provide the declared performance characteristics, while the manufacturer is responsible for his product during the entire period of operation. The term of 5 years is established by two standards - GOST 4754-97 and 5513-97.

On the other hand, there are no such laws in Western countries, and manufacturers car tires They claim that their products have a lifespan of 10 years. At the same time, there are no legislative acts in the world and in Russia that would oblige drivers and owners Vehicle produce mandatory replacement tires at the end of the warranty period. Although in Russian traffic rules there is a rule residual height tread, and, as practice shows, tire wear usually occurs faster than their service life expires.

There is also such a thing as the shelf life of car tires, however Russian legislation does not set a time limit. Therefore, manufacturers and sellers usually rely on the warranty period, and say that the tire, subject to right conditions can lie for 5 years, and after that it can be used like new. However, in a number of countries in Europe and Asia, the maximum shelf life is 3 years, and after this period the tire can no longer be considered new.

So, how long can you use the tires installed on the car? Five, ten years or more? After all, all these figures are recommended, but no one obliges the driver to replace tires, even after fifteen years, the main thing is that they are not worn out. However, manufacturers themselves recommend replacing tires at the age of 10 years, and in most cases, tires become unusable after 6-8 years of operation.

What are the indicated periods of operation and storage of car tires related to? It's all about the rubber itself, from which tires are made - this material, with all its advantages, is subject to natural aging, which leads to a loss of basic qualities. As a result of aging, rubber can lose elasticity and strength, microscopic damage appears in it, eventually turning into noticeable cracks, etc.

Tire aging is primarily a chemical process. Under the influence of light, temperature differences, gases contained in the air, oils and other substances, the elastomer molecules that make up rubber are destroyed, and the bonds between these molecules are also destroyed - all this leads to a loss of elasticity and strength of rubber. As a result of rubber aging, tires resist wear worse, they literally crumble and can no longer provide the necessary performance characteristics.

It is because of the aging processes of rubber that manufacturers and domestic GOST establish a warranty period for the operation of tires. domestic standard establishes the period after which the aging of rubber does not yet have a negative effect, and tire manufacturers set the actual service life at which aging is already noticeable. Therefore, you should be very careful with tires over 6-8 years old, and tires that have celebrated their 10-year "anniversary" must be changed without fail.

To replace a tire, you need to determine its age - this is quite simple.

Ways to check the age of tires

On car tires, as well as on any other product, the date of production must be indicated - it is by this date that one can judge the age of the tires bought or installed on the car. To date, the marking of the date of manufacture of tires is made according to the standard approved in 2000 by the US Department of Transportation (U.S. Department Of Transportation) standard.

On any tire there is an oval-pressure, in front of which is the abbreviation DOT and an alphanumeric index. Numbers and letters are also pressed into the oval - they are the ones that indicate the date of production of the tire. More precisely, the date is encrypted in the last four digits, which mean the following:

The first two digits are the week of the year;
The last two digits are the year.

So, if the last four digits in the crimping oval are 4908, then the tire was produced on the 48th week of 2008. By Russian standards, such a tire has already exhausted its resource, and by world standards it should already be replaced.

However, on tires you can find other designations of the time of production. In particular, in the oval crimping there may be not four, but three numbers, and there is also a small triangle - this means that this tire was produced between 1990 and 2000. It is clear that now such tires can no longer be used, even if they were in storage or installed on a car that has stood in the garage for many years.

Thus, one glance is enough to determine the age of a tire. However, not all car owners know this, which is used by dishonest sellers who pass off old tires as new ones. Therefore, when buying rubber, you need to be careful and be sure to check the production date.

Determining when to change tires

When is it time to change tires? There are several cases when it is necessary to buy new tires:

Age 10 years or more - even if this tire looks good on the outside, it has no visible damage and its wear is low, it should be removed and sent for recycling;
The age of the tire is 6-8 years, while its wear is approaching critical;
critical or uneven wear, large punctures and tears regardless of the age of the tire.

As practice shows, tires, especially in Russia with its road features, rarely "survive" to the age of ten. Therefore, tires are most often replaced due to wear or damage. However, in our country, not quite new tires often go on sale, so every driver should be able to determine their age - only in this case you can protect yourself and your car.

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Rubbers based on perfluoroelastomers do not have significant advantages at temperatures below 250 ˚С, and below 150 ˚С they are significantly inferior to rubbers made from rubbers of the SKF-26 type. However, at temperatures above 250 ˚С their heat resistance in compression is high.

The resistance to thermal aging in compression of rubbers from Viton GLT and VT-R-4590 rubbers depends on the content of organic peroxide and TAIC. The ODS value of rubber from Viton GLT rubber containing 4 wt. hours of calcium hydroxide, peroxide and TAIC after aging for 70 hours at 200 and 232˚C is 30 and 53%, respectively, which is much worse than that of Viton E-60C rubber. However, the replacement of carbon black N990 with finely ground bituminous coal can reduce the ODR to 21% and 36%, respectively.

The vulcanization of FA-based rubbers is usually carried out in two stages. Carrying out the second stage (temperature control) can significantly reduce the NDR and the rate of stress relaxation at elevated temperature. Typically, the temperature of the second stage of vulcanization is equal to or higher than the operating temperature. Temperature control of amine vulcanizates is carried out at 200-260 °C for 24 hours.

Rubbers based on organosilicon rubbers

The compressive heat resistance of rubbers based on KK significantly decreases with aging in conditions of limited air access. Thus, the RDR (280°C, 4 h) near the open surface and in the center of a 50 mm diameter cylindrical specimen made of rubber based on SKTV-1, sandwiched between two parallel metal plates, is 65 and 95–100%, respectively.

Depending on the purpose of ODS (177 ° C, 22 hours) for rubbers from KK can be: conventional - 20-25%, sealing - 15%; increased frost resistance-50%; increased strength - 30-40%, oil and petrol resistant - 30%. Increased thermal stability of CR rubbers in air can be achieved by creating siloxane cross-links in the vulcanizate, the stability of which is equal to the stability of rubber macromolecules, for example, during oxidation of the polymer followed by heating in vacuum. The stress relaxation rate of such vulcanizates in oxygen is much lower than that of peroxide and radiation vulcanizates SKTV-1. However, the value τ (300 °C, 80%) for rubbers made from the most heat-resistant rubbers SKTFV-2101 and SKTFV-2103 is only 10-14 hours.

The value of ODS and the rate of chemical stress relaxation of rubbers from CC at an elevated temperature decreases with an increase in the degree of vulcanization. This is achieved by increasing the content of vinyl units in rubber up to a certain limit, increasing the content of organic peroxide, heat treatment of the carved mixture (200-225 C, 6-7 hours) before vulcanization.

The presence of moisture and traces of alkali in the rubber compound reduces the heat resistance in compression. The rate of stress relaxation increases with increasing humidity in an inert environment or in air.

The value of ODS increases with the use of active silicon dioxide.

PROTECTION OF RUBBERS FROM RADIATION AGING

Most effective way Prevention of undesirable changes in the structure and properties of rubber under the action of ionizing radiation is the introduction of special protective anti-rad additives into the rubber mixture. An ideal protective system should "work" simultaneously through various mechanisms, providing consistent "interception" of unwanted reactions at all stages of the radiation-chemical process. Below is an exemplary scheme for protecting polymers using

various additives at different stages of the radiation-chemical process:

Stage	The action of the protective additive
Absorption of radiation energy. Intra- and Intermolecular Energy Transfer of Electronic Excitation	Dissipation of the energy of electronic excitation received by them in the form of heat or long-wave electromagnetic radiation without significant changes.
Ionization of a polymer molecule followed by recombination of an electron and a parent ion. Formation of superexcited states and dissociation of a polymer molecule.	Transfer of an electron to a polymer ion without subsequent excitation. Electron acceptance and decrease in the probability of neutralization reactions with the formation of excited molecules.
C ¾ H bond rupture, hydrogen atom abstraction, formation of a polymer radical. Elimination of the second hydrogen atom with the formation of H 2 and the second macroradical or double bond	Transfer of a hydrogen atom to a polymer radical. Acceptance of the hydrogen atom and prevention of its subsequent reactions.
Disproportionation or recombination of polymer radicals with the formation of an intermolecular chemical bond	Interaction with polymer radicals to form a stable molecule.

As antirads for unsaturated rubbers, secondary amines are most widely used, which provide a significant reduction in the rates of crosslinking and destruction of NC vulcanizates in air, in nitrogen and vacuum. However, a decrease in the stress relaxation rate in NR rubbers containing N-phenyl-N"-cyclohexyl-p-phenylenediamine antioxidant (4010) and N, N`-diphenyl-n-phenylenediamine was not observed. It is possible that the protective effect of these compounds is due to the presence of Aromatic amines, quinones and quinone imines, which are effective antirads of undeformed rubbers based on SKN, SKD and NK, have practically no effect on the rate of stress relaxation of these rubbers under the action of ionizing radiation in a gaseous nitrogen medium.

Since the action of antirads in rubber is due to various mechanisms, the most effective protection can be provided with the simultaneous use of various antirads. The use of a protective group containing a combination of aldol-alpha-naphthylamine, N-phenyl-N "-isopropyl-n-phenylenediamine (diaphene FP), dioctyl-n-phenylenediamine and monoisopropyldiphenyl ensured the preservation of a sufficiently high εp rubber based on BNR up to a dose of 5∙10 6 Gy in air.

Saturated elastomers are much more difficult to protect. Hydroquinone, FCPD, and DOPD are effective antirads for rubbers based on a copolymer of ethyl acrylate and 2-chloroethyl vinyl ether, as well as fluoroelastomer. For rubbers based on CSPE, zinc dibutyldithiocarbamate and polymerized 2,2,4-trimethyl-1,2-dihydroquinoline (acetonanil) are recommended. The rate of destruction of sulfur vulcanizates BC is reduced by adding zinc dibutyldithiocarbamate or naphthalene to the rubber mixture; MMBF is effective in resin vulcanizates.

Many aromatic compounds (anthracene, di - tret - butyl- n-cresol), as well as substances interacting with macroradicals (iodine, disulfides, quinones) or containing labile hydrogen atoms (benzophenone, mercaptans, disulfides, sulfur), protecting unfilled polysiloxanes have not found practical application in the development of radiation-resistant organosilicon rubbers.

Action efficiency various types ionizing radiation on elastomers depends on the magnitude of linear energy losses. In most cases, an increase in linear energy losses significantly reduces the intensity of radiation-chemical reactions, which is due to an increase in the contribution of intratrack reactions and a decrease in the probability of intermediate active particles leaving the track. If the reactions in the track are insignificant, which may be due to the rapid migration of electronic excitation or charge from the track, for example, before free radicals have time to form within it, then the effect of the type of radiation on the change in properties is not observed. Therefore, under the action of radiation with a high linear energy loss, the effectiveness of protective additives sharply decreases, which do not have time to prevent the occurrence of intratrack processes and reactions involving oxygen. Indeed, secondary amines and other effective antirads do not have a protective effect when polymers are irradiated with heavy charged particles.

Bibliography:

1. D.L. Fedyukin, F.A. Mahlis "Technical and technological properties of rubbers". M., "Chemistry", 1985.

2. Sat. Art. "Achievements of science and technology in the field of rubber". M., "Chemistry", 1969.

3. V.A. Lepetov "Rubber technical products", M., "Chemistry"

4. Sobolev V.M., Borodina I.V. "Industrial Synthetic Rubbers". M., "Chemistry", 1977

1. LITERARY REVIEW.
1.1. INTRODUCTION
1.2. AGING OF RUBBER.
1.2.1. Types of aging.
1.2.2. Thermal aging.
1.2.3. Ozone aging.
1.3. ANTI-AGING AND ANTIOZONANTS.
1.4. POLYVINYL CHLORIDE.
1.4.1. PVC plastisols.

2. CHOOSING THE DIRECTION OF RESEARCH.
3. TECHNICAL CONDITIONS FOR THE PRODUCT.
3.1. TECHNICAL REQUIREMENTS.
3.2. SAFETY REQUIREMENTS.
3.3. TEST METHODS.
3.4. MANUFACTURER WARRANTY.
4. EXPERIMENTAL
5. RESULTS AND DISCUSSION.
CONCLUSIONS.
LIST OF USED LITERATURE:

Annotation.

Antioxidants used in the form of high-molecular pastes are widely used in the domestic and foreign industries for the production of tires and rubber goods.
In this work, we study the possibility of obtaining an anti-aging paste based on combinations of two anti-aging agents, diaphene FP and diaphene FF, with polyvinyl chloride as a dispersion medium.
By changing the content of PVC and antioxidants, it is possible to obtain pastes suitable for protecting rubber from thermo-oxidative and ozone aging.
The work is done on the pages.
20 literary sources were used.
There are 6 tables in the work.

Introduction.

The most widely used in the Fatherland industry were two antioxidants diafen FP and acetanyl R.
The small assortment presented by two antioxidants is explained by a number of reasons. The production of some antioxidants has ceased to exist, for example, neozone D, while others do not meet modern requirements applied to them, for example, diafen FF, it fades on the surface of rubber compounds.
Due to the lack of domestic antioxidants and the high cost of foreign analogues, in this paper, we investigate the possibility of using the composition of the antioxidants diaphene FP and diaphene FF in the form of a highly concentrated paste, a dispersion medium in which PVC is.

1. Literary review.
1.1. Introduction.

Protecting rubber from thermal and ozone aging is the main goal of this work. As ingredients that protect rubber from aging, a composition of diaphene FP with diaphene FF and polyvinyl poride (dispersion medium) is used. The manufacturing process of anti-aging paste is described in the experimental part.
Anti-aging paste is used in rubbers based on SKI-3 isoprene rubber. Rubbers based on this rubber are resistant to the action of water, acetone, ethyl alcohol and are not resistant to the action of gasoline, mineral and animal oils, etc.
During the storage of rubber and the operation of rubber products, an inevitable aging process occurs, leading to a deterioration in their properties. To improve the properties of rubbers, diafen FF is used in combination with diafen FP and polyvinyl chloride, which also allow to some extent to solve the problem of rubber fading.

1.2. Rubber aging.

During the storage of rubbers, as well as during the storage and operation of rubber products, an inevitable aging process occurs, leading to a deterioration in their properties. As a result of aging, tensile strength, elasticity and relative elongation decrease, hysteresis losses and hardness increase, abrasion resistance decreases, plasticity, viscosity and solubility of unvulcanized rubber change. In addition, as a result of aging, the service life of rubber products is significantly reduced. Therefore, increasing the resistance of rubber to aging is of great importance for increasing the reliability and performance of rubber products.
Aging is the result of exposure of rubber to oxygen, heat, light, and especially ozone.
In addition, the aging of rubbers and rubbers is accelerated in the presence of polyvalent metal compounds and under repeated deformations.
The resistance of vulcanizates to aging depends on a number of factors, the most important of which are:
- nature of rubber;
- properties of antioxidants, fillers and plasticizers (oils) contained in rubber;
- the nature of vulcanizing agents and vulcanization accelerators (the structure and stability of sulfide bonds arising during vulcanization depend on them);
- degree of vulcanization;
- solubility and diffusion rate of oxygen in rubber;
- the ratio between the volume and surface of the rubber product (with an increase in the surface, the amount of oxygen penetrating into the rubber increases).
The greatest resistance to aging and oxidation is characterized by polar rubbers - butadiene-nitrile, chloroprene, etc. Non-polar rubbers are less resistant to aging. Their resistance to aging is determined mainly by the features of the molecular structure, the position of double bonds and their number in the main chain. To increase the resistance of rubbers to aging, antioxidants are introduced into them, which slow down oxidation and aging.

1.2.1. Types of aging.

Due to the fact that the role of factors activating oxidation varies depending on the nature and composition of the polymer material, the following types of aging are distinguished in accordance with the predominant influence of one of the factors:
1) thermal (thermal, thermal-oxidative) aging as a result of heat-activated oxidation;
2) fatigue - aging as a result of fatigue caused by the action of mechanical stresses and oxidative processes activated by mechanical action;
3) oxidation activated by metals of variable valence;
4) light aging - as a result of oxidation activated by ultraviolet radiation;
5) ozone aging;
6) radiation aging under the action of ionizing radiation.
In this paper, we study the effect of anti-aging PVC dispersion on the thermal-oxidative and ozone resistance of rubbers based on non-polar rubbers. Therefore, thermal-oxidative and ozone aging are considered in more detail below.

1.2.2. Thermal aging.

Thermal aging is the result of simultaneous exposure to heat and oxygen. Oxidative processes are main reason thermal aging in air.
Most of the ingredients in one way or another affect these processes. Carbon black and other fillers adsorb antioxidants on their surface, reduce their concentration in rubber and, therefore, accelerate aging. Highly oxidized carbon blacks can be catalysts for the oxidation of rubbers. Slightly oxidized (furnace, thermal) soot, as a rule, slows down the oxidation of rubbers.
During the thermal aging of rubber, which occurs during elevated temperatures, almost all basic physical and mechanical properties change irreversibly. The change in these properties depends on the ratio of the processes of structuring and destruction. During thermal aging of most rubbers based on synthetic rubbers, structuring occurs predominantly, which is accompanied by a decrease in elasticity and an increase in rigidity. During thermal aging of rubbers from natural and synthetic isopropene rubber and butyl rubber, destructive processes develop to a greater extent, leading to a decrease in conditional stresses at given elongations and an increase in residual deformations.
The ratio of filler to oxidation will depend on its nature, on the type of inhibitors introduced into the rubber, and on the nature of the vulcanization bonds.
Vulcanization accelerators, as well as products, their transformations remaining in rubbers (mercaptans, carbonates, etc.) can participate in oxidative processes. They can cause degradation of hydroperoxides by a molecular mechanism and thus contribute to the protection of rubbers from aging.
The nature of the vulcanization mesh has a significant effect on thermal aging. At moderate temperatures (up to 70o) free sulfur and polysulfide cross-links retard oxidation. However, with an increase in temperature, the rearrangement of polysulfide bonds, in which free sulfur can also be involved, leads to accelerated oxidation of vulcanizates, which turn out to be unstable under these conditions. Therefore, it is necessary to select a vulcanization group that provides the formation of resistant to rearrangement and oxidation of cross-links.
To protect rubber from thermal aging, antioxidants are used that increase the resistance of rubbers and rubbers to oxygen, i.e. substances with antioxidant properties - primarily secondary aromatic amines, phenols, bisfinols, etc.

1.2.3. Ozone aging.

Ozone has a strong influence on the aging of rubber even in low concentrations. This is sometimes found already in the process of storage and transportation of rubber products. If at the same time the rubber is in a stretched state, then cracks appear on its surface, the growth of which can lead to rupture of the material.
Ozone apparently adds to the rubber via double bonds to form ozonides, the decomposition of which leads to the rupture of macromolecules and is accompanied by the formation of cracks on the surface of stretched rubbers. In addition, ozonation simultaneously develops oxidative processes that promote the growth of cracks. The rate of ozone aging increases with increasing ozone concentration, strain value, temperature increase and exposure to light.
Lowering the temperature leads to a sharp slowdown of this aging. Under test conditions at a constant value of deformations; at temperatures exceeding the glass transition temperature of the polymer by 15-20 degrees Celsius, aging almost completely stops.
The resistance of rubber to ozone depends mainly on the chemical nature of the rubber.
Rubbers based on various rubbers can be divided into 4 groups according to ozone resistance:
1) highly resistant rubbers (fluororubbers, SKEP, HSPE);
2) resistant rubber (butyl rubber, pearite);
3) moderately resistant rubbers that do not crack under the action of atmospheric ozone concentrations for several months and are resistant to an ozone concentration of about 0.001% for more than 1 hour, based on chloroprene rubber without protective additives and rubbers based on unsaturated rubbers (NK, SKS, SKN, SKI -3) with protective additives;
4) unstable rubber.
The most effective in protecting against ozone aging is the combined use of antiozontics and waxy substances.
Chemical antiozonants include N-substituted aromatic amines and dihydroquinoline derivatives. Antiozonants react with ozone on rubber surfaces at a high rate, much faster than the rate at which ozone interacts with rubber. As a result of this, the ozone aging process slows down.
Secondary aromatic diamines are the most effective antiaging and antiozontic agents for protecting rubber from thermal and ozone aging.

1.3. Antioxidants and antiozonants.

The most effective antioxidants and antiozonants are secondary aromatic amines.
They are not oxidized by molecular oxygen either in dry form or in solutions, but are oxidized by rubber peroxides during thermal aging and during dynamic work causing chain break. So diphenylamine; N, N'-diphenyl-n-phenylenediamine is consumed by almost 90% during dynamic fatigue or thermal aging of rubber. In this case, only the content of NH groups changes, while the nitrogen content in the rubber remains unchanged, which indicates the addition of an antioxidant to the rubber hydrocarbon.
Antioxidants of this class have a very high protective effect against thermal and ozone aging.
One of the widely used representatives of this group of antioxidants is N,N'-diphenyl-n-phenylenedialin (Diafen FF).

It is an effective antioxidant that increases the resistance of rubbers based on SDK, SKI-3 and natural rubber to the action of repeated deformations. Diafen FF colors rubber.
The best antioxidant to protect rubber from thermal and ozone aging, as well as from fatigue, is diafen FP, however, it is relatively highly volatile and is easily extracted from rubber with water.
N-Phenyl-N'-isopropyl-n-phenylenediamine (Diafen FP, 4010 NA, Santoflex IP) has the following formula:

With an increase in the size of the alkyl group of the substituent, the solubility of secondary aromatic diamines in polymers increases; increased resistance to water washout, reduced volatility and toxicity.
Comparative characteristics diaphene FF and diaphene FP are given because in this work, studies are carried out that are caused by the fact that the use of diaphene FF as an individual product leads to its “fading” on the surface of rubber compounds and vulcanizates. In addition, it is somewhat inferior to diaphene FP in terms of protective action; has in comparison with the latter more high temperature melting, which adversely affects its distribution in rubber.
PVC is used as a binder (dispersion medium) to obtain a paste based on combinations of antioxidants diaphene FF and diaphene FP.

1.4. Polyvinyl chloride.

Polyvinyl chloride is a polymerization product of vinyl chloride (CH2=CHCl).
PVC is produced in the form of a powder with a particle size of 100-200 microns. PVC is an amorphous polymer with a density of 1380-1400 kg/m3 and a glass transition temperature of 70-80°C. It is one of the most polar polymers with high intermolecular interaction. It combines well with most commercially available plasticizers.
The high content of chlorine in PVC makes it a self-extinguishing material. PVC is a general purpose polymer. In practice, they deal with plastisols.

1.4.1. PVC plastisols.

Plastisols are PVC dispersions in liquid plasticizers. The amount of plasticizers (dibutyl phthalates, dialkyl phthalates, etc.) ranges from 30 to 80%.
At ordinary temperatures, PVC particles practically do not swell in these plasticizers, which makes plastisols stable. When heated to 35-40 ° C, as a result of the acceleration of the swelling process (gelatinization), plastisols turn into highly bound masses, which, after cooling, turn into elastic materials.

1.4.2. The mechanism of gelatinization of plastisols.

The mechanism of gelatinization is as follows. As the temperature rises, the plasticizer slowly penetrates into the polymer particles, which increase in size. Agglomerates disintegrate into primary particles. Depending on the strength of the agglomerates, decomposition may begin at room temperature. As the temperature rises to 80-100°C, the viscosity of the plastosol increases strongly, the free plasticizer disappears, and the swollen polymer grains come into contact. At this stage, called pre-gelatinization, the material looks completely homogeneous, but the products made from it do not have sufficient physical and mechanical characteristics. Gelatinization is completed only when the plasticizers are evenly distributed in polyvinyl chloride, and the plastisol turns into a homogeneous body. In this case, the surface of the swollen primary polymer particles fuses and plasticized polyvinyl chloride is formed.

2. Choice of research direction.

Currently, in the domestic industry, the main ingredients that protect rubber from aging are diaphene FP and acetyl R.
The too small assortment presented by two antioxidants is explained by the fact that, firstly, some production of antioxidants ceased to exist (neozone D), and secondly, other antioxidants do not meet modern requirements (diafen FF).
Most antioxidants fade on the surface of rubbers. Antioxidant mixtures having either synergistic or additive properties can be used to reduce fading of antioxidants. This, in turn, makes it possible to save a scarce antioxidant. The use of a combination of antioxidants is proposed to be carried out by individual dosing of each antioxidant, but it is most advisable to use antioxidants in the form of a mixture or in the form of paste-forming compositions.
The dispersion medium in the pastes are low-molecular substances, such as oils of petroleum origin, as well as polymers - rubbers, resins, thermoplastics.
In this work, we study the possibility of using polyvinyl chloride as a binder (dispersion medium) to obtain a paste based on combinations of antioxidants diaphene FF and diaphene FP.
Conducting research is due to the fact that the use of diafen FF as an individual product leads to its “fading” on the surface of rubber compounds and vulcanizates. In addition, the protective effect of diafen FF is somewhat inferior to diafen FP; has a higher melting point in comparison with the latter, which adversely affects the distribution of diaphene FF in rubbers.

3. Specifications for the product.

This technical condition applies to the PD-9 dispersion, which is a composition of polyvinyl chloride with an amine-type antioxidant.
The PD-9 dispersion is intended for use as an ingredient in rubber compounds to improve the ozone resistance of vulcanizates.

3.1. Technical requirements.

3.1.1. Dispersion PD-9 must be made in accordance with the requirements of these specifications according to the technological regulations in the prescribed manner.

3.1.2. In terms of physical indicators, the dispersion of PD-9 must comply with the standards indicated in the table.
Table.
Name of indicator Norm* Test method
1. Appearance. Crumb dispersion from gray to dark gray According to clause 3.3.2.
2. Linear size of the crumb, mm, no more. 40 According to paragraph 3.3.3.
3. Mass of the dispersion in a plastic bag, kg, no more. 20 According to clause 3.3.4.
4. Mooney viscosity, units Mooney 9-25 According to paragraph 3.3.5.
*) the norms are specified after the release of an experimental batch and statistical processing of the results.

3.2. Safety requirements.

3.2.1. Dispersion PD-9 is a combustible substance. The flash point is not lower than 150°C. Self-ignition temperature 500oC.
The extinguishing agent in case of fire is water mist and chemical foam.
means personal protection- gas mask poppies "M".

3.2.2. Dispersion PD-9 is a low-toxic substance. In case of contact with eyes, rinse them with water. Remove product on skin by washing with soap and water.

3.2.3. All workrooms in which work with PD-9 dispersion is carried out must be equipped with supply and exhaust ventilation.
The dispersion of PD-9 does not require the establishment of a hygienic regulation for it (maximum concentration limit and SHEE).

3.3. Test methods.

3.3.1. At least three point samples are taken, then they are combined, thoroughly mixed and an average sample is taken by quartering.

3.3.2. Appearance definition. Appearance is determined visually during sampling.

3.3.3. Determination of crumb size. To determine the size of the PD-9 dispersion crumb, a metric ruler is used.

3.3.4. Determination of the mass of the PD-9 dispersion in a plastic bag. To determine the mass of the PD-9 dispersion in a plastic bag, a scale of the RN-10Ts 13M type is used.

3.3.5. Determination of Mooney viscosity. The determination of Mooney viscosity is based on the presence of a certain amount of the polymer component in the PD-9 dispersion.

3.4. Manufacturer's warranty.

3.4.1. The manufacturer guarantees the compliance of the PD-9 dispersion with the requirements of these specifications.
3.4.2. Guarantee period storage dispersion PD-9 6 months from the date of manufacture.

4. Experimental part.

In this work, we study the possibility of using polyvinyl chloride (PVC) as a binder (dispersion medium) to obtain a paste based on combinations of antioxidants diaphene FF and diaphene FP. The effect of this anti-aging dispersion on the thermal-oxidative and ozone resistance of rubbers based on SKI-3 rubber is also being studied.

Preparation of anti-aging paste.

On fig. 1. A plant for preparing an anti-aging paste is shown.
Preparation was carried out in a glass flask (6) with a volume of 500 cm3. The flask with the ingredients was heated on an electric stove (1). The flask is placed in the bath (2). The temperature in the flask was controlled using a contact thermometer (13). Stirring is carried out at a temperature of 70±5°C and using a paddle mixer (5).

Fig.1. Installation for the preparation of anti-aging paste.
1 - electric stove with a closed spiral (220 V);
2 - bath;
3 - contact thermometer;
4 – contact thermometer relay;
5 - paddle mixer;
6 - glass flask.

The order of loading the ingredients.

The calculated amount of diaphene FF, diaphene FP, stearin and a portion (10% wt.) of dibutylphthalan (DBP) were loaded into the flask. After that, mixing was carried out for 10-15 minutes until a homogeneous mass was obtained.
The mixture was then cooled to room temperature.
After that, polyvinyl chloride and the rest of DBP (9% wt.) were loaded into the mixture. The resulting product was discharged into a porcelain glass. Next, the product was thermostated at temperatures of 100, 110, 120, 130, 140°C.
The composition of the resulting composition is shown in table 1.
Table 1
The composition of the anti-aging paste P-9.
Ingredients % wt. Loading into the reactor, g
PVC 50.00 500.00
Diafen FF 15.00 150.00
Diafen FP (4010 NA) 15.00 150.00
DBF 19.00 190.00
Stearin 1.00 10.00
Total 100.00 1000.00

To study the effect of anti-aging paste on the properties of vulcanizates, a rubber mixture based on SKI-3 was used.
The resulting anti-aging paste was introduced into the rubber compound based on SKI-3.
The compositions of rubber compounds with anti-aging paste are shown in Table 2.
The physical and mechanical properties of the vulcanizates were determined in accordance with GOST and TU, shown in Table 3.
table 2
The composition of the rubber compound.
Ingredients Bookmark numbers
I II
Mix codes
1-9 2-9 3-9 4-9 1-25 2-25 3-25 4-25
Rubber SKI-3 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00
Sulfur 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Altax 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60
Guanide F 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00
Zinc white 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00
Stearin 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
Carbon black P-324 20.00 20.00 20.00 20.00 20.00 20.00 20.00 20.00
Diafen FP 1.00 - - - 1.00 - - -
Anti-aging paste (P-9) - 2.3 3.3 4.3 - - - -
Anti-aging paste P-9 (100оС*) - - - - - 2.00 - -
P-9 (120оС*) - - - - - - 2.00 -
P-9 (140оС*) - - - - - - - 2.00
Note: (оС*) – temperature of pre-gelatinization of the paste (P-9) is indicated in brackets.

Table 3
No. p.p. Name of GOST indicator
1 Conditional tensile strength, % GOST 270-75
2 Nominal stress at 300%, % GOST 270-75
3 Elongation at break, % GOST 270-75
4 Permanent elongation, % GOST 270-75
5 Change in the above indicators after aging, air, 100°C * 72 h, % GOST 9.024-75
6 Dynamic tensile strength, thousand cycles, Е?=100% GOST 10952-64
7 Shore hardness, conventional unit GOST 263-75

Determination of the rheological properties of anti-aging paste.

1. Determination of Mooney viscosity.
The determination of the Mooney viscosity was carried out on a Mooney viscometer (GDR).
The manufacture of samples for testing and directly testing are carried out according to the methodology set forth in the technical specifications.
2. Determination of the cohesive strength of pasty compositions.
Paste samples after gelatinization and cooling to room temperature were passed through a gap of 2.5 mm thick rollers. Then, from these sheets in a vulcanizing press, plates were made with a size of 13.6 * 11.6 mm and a thickness of 2 ± 0.3 mm.
After curing the plates for a day, the spatulas were cut out with a punching knife in accordance with GOST 265-72 and further, on a RMI-60 tensile machine at a speed of 500 mm/min, the breaking load was determined.
The specific load was taken as the cohesive strength.

5. Obtained results and their discussion.

When studying the possibility of using PVC, as well as the composition of polar plasticizers as a binder (dispersion medium) to obtain pastes based on combinations of antioxidants diaphene FF and diaphene FP, it was found that the alloy of diaphene FF with diaphene FP in a mass ratio of 1: 1 is characterized by a low speed crystallization and a melting point of about 90°C.
Low speed crystallization plays a positive role in the manufacturing process of PVC plastisol filled with a mixture of antioxidants. In this case, the energy consumption for obtaining a homogeneous composition that does not delaminate in time is significantly reduced.
The melt viscosity of diaphene FF and diaphene FP is close to the viscosity of PVC plastisol. This makes it possible to mix the melt and plastisol in reactors with anchor-type mixers. On fig. 1 shows a diagram of the installation for the production of pastes. The pastes drain satisfactorily from the reactor before their pre-gelatinization.
It is known that the gelatinization process proceeds at 150°C and above. However, under these conditions, the elimination of hydrogen chloride is possible, which, in turn, is able to block the mobile hydrogen atom in the molecules of secondary amines, which in this case are antioxidants. This process proceeds according to the following scheme.
1. Formation of polymeric hydroperoxide during the oxidation of isoprene rubber.
RH+O2 ROOH,
2. One of the directions of decomposition of polymeric hydroperoxide.
ROOH RO°+O°H
3. Having formed the oxidation stages due to the antioxidant molecule.
AnH+RO° ROH+An°,
Where An is the antioxidant radical, for example,
4.
5. Properties of amines, including secondary ones (diaphene FF) to form alkyl-substituted ones with mineral acids according to the scheme:
H
R-°N°-R+HCl + Cl-
H

This reduces the reactivity of the hydrogen atom.

Carrying out the process of gelatinization (pre-gelatinization) at relatively low temperatures (100-140°C) it is possible to avoid the phenomena mentioned above, i.e. reduce the chance of splitting off hydrogen chloride.
The final gelling process results in pastes with a Mooney viscosity lower than that of the filled rubber compound and low cohesive strength (see figure 2.3).
Pastes with low Mooney viscosity, firstly, are well distributed in the mixture, and secondly, insignificant parts of the components that make up the paste are able to migrate quite easily into the surface layers of vulcanizates, thereby protecting rubber from aging.
In particular, in the issue of "crushing" paste-forming compositions, great importance is attached to explaining the reasons for the deterioration of the properties of some compositions under the action of ozone.
In this case, the initial low viscosity of the pastes, which, moreover, does not change during storage (Table 4), allows for a more uniform distribution of the paste, and makes it possible for its components to migrate to the surface of the vulcanizate.

Table 4
Viscosity indicators according to Mooney paste (P-9)
Initial indicators Indicators after storing the paste for 2 months
10 8
13 14
14 18
14 15
17 25

By changing the content of PVC and antioxidants, it is possible to obtain pastes suitable for protecting rubber from thermal-oxidative and ozone aging, both based on non-polar and polar rubbers. In the first case, the PVC content is 40-50% wt. (paste P-9), in the second - 80-90% wt.
In this work, we study vulcanizates based on SKI-3 isoprene rubber. Physical and mechanical properties of vulcanizates using paste (P-9) are presented in tables 5 and 6.
The resistance of the studied vulcanizates to thermal-oxidative aging increases with an increase in the content of the anti-aging paste in the mixture, as can be seen from Table 5.
The indicators of change in the conditional strength of the regular composition (1-9) is (-22%), while for the composition (4-9) - (-18%).
It should also be noted that with the introduction of a paste that promotes an increase in the resistance of vulcanizates to thermal-oxidative aging, a more significant dynamic endurance is imparted. Moreover, explaining the increase in dynamic endurance, it is impossible, apparently, to limit ourselves only to the factor of increasing the dose of the antioxidant in the rubber matrix. Not the last role is probably played by PVC. In this case, it can be assumed that the presence of PVC can cause the effect of the formation of continuous chain structures, which are evenly distributed in the rubber and prevent the growth of microcracks that occur during cracking.
By reducing the content of anti-aging paste and thus the proportion of PVC (Table 6), the effect of increasing dynamic endurance is practically canceled. In this case, the positive effect of the paste is manifested only under conditions of thermal-oxidative and ozone aging.
It should be noted that the best physical and mechanical properties are observed when using an anti-aging paste obtained under milder conditions (pre-gelatinization temperature 100°C).
Such conditions for obtaining a paste provide more high level stability, compared with the paste obtained by thermostating for an hour at 140°C.
An increase in the viscosity of PVC in a paste obtained at a given temperature also does not contribute to the preservation of the dynamic endurance of vulcanizates. And as follows from Table 6, dynamic endurance is greatly reduced in pastes thermostated at 140°C.
The use of diaphene FF in composition with diaphene FP and PVC makes it possible to solve the problem of fading to some extent.

Table 5

1-9 2-9 3-9 4-9
1 2 3 4 5
Conditional tensile strength, MPa 19.8 19.7 18.7 19.6
Nominal stress at 300%, MPa 2.8 2.8 2.3 2.7

1 2 3 4 5
Elongation at break, % 660 670 680 650
Permanent elongation, % 12 12 16 16
Hardness, Shore A, arb. 40 43 40 40
Conditional tensile strength, MPa -22 -26 -41 -18
Nominal stress at 300%, MPa 6 -5 8 28
Relative elongation at break, % -2 -4 -8 -4
Permanent elongation, % 13 33 -15 25

Dynamic endurance, Eg=100%, thousand cycles. 121 132 137 145

Table 6
Physical and mechanical properties of vulcanizates containing anti-aging paste (P-9).
Name of the index Code of the mixture
1-25 2-25 3-25 4-25
1 2 3 4 5
Conditional tensile strength, MPa 22 23 23 23
Nominal stress at 300%, MPa 3.5 3.5 3.3 3.5

1 2 3 4 5
Elongation at break, % 650 654 640 670
Permanent elongation, % 12 16 18 17
Hardness, Shore A, arb. 37 36 37 38
Change in index after aging, air, 100°C*72 h
Conditional tensile strength, MPa -10.5 -7 -13 -23
Nominal stress at 300%, MPa 30 -2 21 14
Elongation at break, % -8 -5 -7 -8
Residual elongation, % -25 -6 -22 -4
Ozone resistance, E=10%, hour 8 8 8 8
Dynamic endurance, Eg=100%, thousand cycles. 140 116 130 110

List of symbols.

PVC - polyvinyl chloride
Diaphen FF - N,N' - Diphenyl - n - phenylenediamine
Diaphen FP - N - Phenyl - N ' - isopropyl - n - phenylenediamine
DBP - dibutyl phthalate
SKI-3 - isoprene rubber
P-9 - anti-aging paste

1. Research for the composition of diaphene FP and diaphene FF plastisol based on PVC allows to obtain pastes that do not delaminate in time, with stable rheological properties and a Mooney viscosity higher than the viscosity of the used rubber compound.
2. When the content of the combination of diaphene FP and diaphene FF in the paste is 30% and PVC plastisol 50%, the optimal dosage for protecting rubber from thermal-oxidative and ozone aging can be a dosage equal to 2.00 parts by weight per, 100 parts by weight of rubber rubber mixtures.
3. An increase in the dosage of antioxidants over 100 parts by weight of rubber leads to an increase in the dynamic endurance of rubber.
4. For rubbers based on isoprene rubber, operating in a static mode, it is possible to replace diafen FP with anti-aging paste P-9 in the amount of 2.00 wt h per 100 wt h of rubber.
5. For rubbers operating under dynamic conditions, the replacement of diaphene FP is possible with an antioxidant content of 8-9 wt h per 100 wt h of rubber.
6.
List of used literature:

– Tarasov Z.N. Aging and stabilization of synthetic rubbers. - M.: Chemistry, 1980. - 264 p.
– Garmonov I.V. Synthetic rubber. - L.: Chemistry, 1976. - 450 p.
– Aging and stabilization of polymers. / Ed. Kozminsky A.S. - M.: Chemistry, 1966. - 212 p.
– Sobolev V.M., Borodina I.V. Industrial synthetic rubbers. – M.: Chemistry, 1977. – 520 p.
- Belozerov N.V. Rubber Technology: 3rd ed. Revised. and additional - M.: Chemistry, 1979. - 472 p.
– Koshelev F.F., Kornev A.E., Klimov N.S. General rubber technology: 3rd ed. Revised. and additional - M.: Chemistry, 1968. - 560 p.
– Technology of plastics. / Ed. Korshak V.V. Ed. 2nd, revised. and additional - M.: Chemistry, 1976. - 608 p.
– Kirpichnikov P.A., Averko-Antonovich L.A. Chemistry and technology of synthetic rubber. - L .: Chemistry, 1970. - 527 p.
– Dogadkin B.A., Dontsov A.A., Shertnov V.A. Chemistry of elastomers. - M.: Chemistry, 1981. - 372 p.
– Zuev Yu.S. Destruction of polymers under the action of aggressive media: 2nd ed. and additional - M.: Chemistry, 1972. - 232 p.
– Zuev Yu.S., Degtyareva T.G. Durability of elastomers under operating conditions. - M.: Chemistry, 1980. - 264 p.
– Ognevskaya T.E., Boguslavskaya K.V. Increasing the weather resistance of rubber through the introduction of ozone-resistant polymers. - M.: Chemistry, 1969. - 72 p.
– Kudinova G.D., Prokopchuk N.R., Prokopovich V.P., Klimovtsova I.A. // Raw materials for the rubber industry: present and future: Abstracts of the fifth anniversary Russian scientific and practical conference of rubber workers. - M.: Chemistry, 1998. - 482 p.
– Khrulev M.V. Polyvinyl chloride. - M.: Chemistry, 1964. - 325 p.
- Obtaining and properties of PVC / Ed. Zilberman E.N. - M.: Chemistry, 1968. - 440 p.
– Rakhman M.Z., Izkovsky N.N., Antonova M.A. //Rubber and rubber. - M., 1967, No. 6. - With. 17-19
– Abram S.W. // Rubb. age. 1962. V. 91. No. 2. P. 255-262
- Encyclopedia of polymers / Ed. Kabanova V.A. and others: In 3 vols., Vol. 2. - M .: Soviet Encyclopedia, 1972. - 1032 p.
- Handbook rubber. Materials of rubber production / Ed. Zakharchenko P.I. and others - M.: Chemistry, 1971. - 430 p.
– Tager A.A. Physicochemistry of polymers. Ed. 3rd, revised. and additional - M.: Chemistry, 1978. - 544 p.

Rubbers and their vulcanizates, like any unsaturated compounds, are capable of various kinds of chemical transformations. The most important reaction that continuously occurs during the storage and operation of rubber products is the oxidation of rubber, leading to a change in its chemical, physical and mechanical properties. Only ebonite, which turns into a fully saturated compound by adding the maximum possible amount of sulfur to the rubber macromolecules, is a chemically inert material. The totality of all the changes that occur in rubber during long-term oxidation is called it aging.

Aging belongs to the category of complex multi-stage transformations, at certain stages of which the elasticity, wear resistance and, to some extent, strength of rubber are significantly reduced. In other words, over time, the performance of rubber products, and consequently, the reliability of the car is reduced. The category of the most unfavorable changes in rubber resulting from aging includes an irreversible decrease in its elasticity. As a result, the increased brittleness of rubber, primarily its surface layers, causes the appearance of cracks in the deformable parts, which gradually deepen and eventually lead to the destruction of the product.

The effects of rubber aging are similar to those of a decrease in temperature, with the only difference that the latter are temporary in nature and partially or completely removable by heating, while the former cannot be weakened by any means, let alone eliminated.

The fight against aging is underway various methods. The supplement is very effective. antioxidants(inhibitors), 1 ... 2% of which, in relation to the rubber contained in rubber, slows down the oxidation process by hundreds and thousands of times. For the same purpose, some rubber products are produced from factories in sealed packaging (in polyethylene cases).

However, technological means are not enough, therefore, a number of operational measures have to be additionally applied. With increasing temperature, aging intensifies, and from heating for every 10 ° C, the aging rate doubles. It is also noticed that the oxidation of rubber is more intense in those areas that experience greater stress. Therefore, it is necessary to keep the rubber products as undeformed as possible.

Wheels and tires

Automobile wheels are distinguished by their purpose, the type of tires used, design and manufacturing technology.

The main parameters of the wheels of some domestic cars are given in Table. 11.2.

Pneumatic tires passenger cars are divided according to the method of sealing the internal volume, the location of the cord threads in the frame, the ratio of height to profile width, the type of tread and a number of other specific features caused by their purpose and operating conditions.

According to the method of sealing the internal volume, they distinguish chamber And tubeless tires.

Tube tires consist of a tire, a tube with a valve, and a rim tape that fits over the rim. The size of the chamber is always slightly smaller than the inner cavity of the tire in order to avoid wrinkling when inflated. The valve is check valve, which allows air to be forced into the tire and prevents it from escaping. The rim tape protects the tube from damage and friction against the wheel and tire bead.

Table 11.2

The main parameters of the wheels of some domestic passenger cars

Cars

Rice. 11.9. Tubeless car tire:

1 - protector; 2 - sealing airtight rubber layer; 3 - frame; 4 - valve; 5 - deep rim

Tubeless tires (Fig. 11.9) are distinguished by the presence of an airtight rubber layer superimposed on the first layer of the carcass (instead of the tube), and have the following advantages (compared to chambered ones):

less weight and better heat exchange with the wheels;

increased safety when driving the car, since when punctured, air escapes only at the puncture site (with a small puncture, rather slowly);

Simplified repair in the event of a puncture (no need for disassembly).

At the same time, the mounting and dismounting of tubeless tires is complicated and requires more skill, and is often only possible on a special tire changer.

Tubeless tires are used for wheels with rims of a special profile and high precision manufacturing.

Chamber and tubeless tires according to the location of the cord threads in the carcass, the tires can be either diagonal or radial.

Tire marking

Bias and radial tires differ not only in design, but also in marking.

For example, in the designation bias tire 6,15-13/155-13:

6.15 - conditional tire profile width (IN) in inches;

13 - landing diameter (d) tires (and wheels) in inches;

155 - conditional tire profile width in mm.

Instead of the last number 13, the bore diameter in mm (330) can be indicated.

Radial tires have a single mixed millimeter-inch designation. For example, in the marking 165/70R13 78S Steel Radial Tubeless:

165 - conditional tire profile width (IN) in mm;

70 - the ratio of the height of the tire profile (R) to its width (IN) in percentages;

R - radial;

13 - landing diameter in inches;

78 - conditional tire load capacity index;

8 - tire speed index (maximum allowable vehicle speed) in km/h.

For everyday driving By Russian roads appropriate to confine N/A not lower than 0.65, and this applies to quite big tires, i.e. tires for cars of the GAZ-3110 Volga type. On VAZ models, it is better not to use tires with N/A below 0.70, and on a VAZ-111 Oka car, it is completely inappropriate to install any other tires other than the factory size 135R12.

Modern high-speed ultra-low profile tires with N/V== 0.30...0.60 are suitable for work only on smooth highways with good surface quality, which are practically non-existent in our country.

Each Russian tire manufacturer has its own company logo or, as for example, the Moscow Tire Plant, the sign of the TAGANKA model.

The tire marking includes a letter (or letters) encoding the manufacturer (for example, K - Kirov Tire Plant; Ya - Yaroslavl Tire Plant, etc.) and numbers (numbers) of the internal factory index of this tire.

On the sidewall of the tire, its serial number is placed and other, quite useful (in case of a complaint) information is encoded (Table 11.3).

Content

Annotation.

Antioxidants used in the form of high-molecular pastes are widely used in the domestic and foreign industries for the production of tires and rubber goods.
In this work, we study the possibility of obtaining an anti-aging paste based on combinations of two anti-aging agents, diaphene FP and diaphene FF, with polyvinyl chloride as a dispersion medium.
By changing the content of PVC and antioxidants, it is possible to obtain pastes suitable for protecting rubber from thermal-oxidative and ozone aging.
The work is done on the pages.
20 literary sources were used.
There are 6 tables in the work.

Introduction.

The most widely used in the Fatherland industry were two antioxidants diafen FP and acetanyl R.
The small assortment presented by two antioxidants is explained by a number of reasons. The production of some antioxidants has ceased to exist, for example, neozone D, while others do not meet modern requirements for them, for example, diafen FF, it fades on the surface of rubber compounds.
Due to the lack of domestic antioxidants and the high cost of foreign analogues, in this paper, we investigate the possibility of using the composition of the antioxidants diaphene FP and diaphene FF in the form of a highly concentrated paste, a dispersion medium in which PVC is.

1. Literary review.
1.1. Introduction.

1.2. Rubber aging.

1.2.1. Types of aging.

1.2.2. Thermal aging.

Thermal aging is the result of simultaneous exposure to heat and oxygen. Oxidative processes are the main cause of thermal aging in air.
Most of the ingredients in one way or another affect these processes. Carbon black and other fillers adsorb antioxidants on their surface, reduce their concentration in rubber and, therefore, accelerate aging. Highly oxidized carbon blacks can be catalysts for the oxidation of rubbers. Slightly oxidized (furnace, thermal) soot, as a rule, slows down the oxidation of rubbers.
During thermal aging of rubber, which occurs at elevated temperatures, almost all the main physical and mechanical properties change irreversibly. The change in these properties depends on the ratio of the processes of structuring and destruction. During thermal aging of most rubbers based on synthetic rubbers, structuring occurs predominantly, which is accompanied by a decrease in elasticity and an increase in rigidity. During thermal aging of rubbers from natural and synthetic isopropene rubber and butyl rubber, destructive processes develop to a greater extent, leading to a decrease in conditional stresses at given elongations and an increase in residual deformations.
The ratio of filler to oxidation will depend on its nature, on the type of inhibitors introduced into the rubber, and on the nature of the vulcanization bonds.
Vulcanization accelerators, as well as products, their transformations remaining in rubbers (mercaptans, carbonates, etc.) can participate in oxidative processes. They can cause degradation of hydroperoxides by a molecular mechanism and thus contribute to the protection of rubbers from aging.
The nature of the vulcanization mesh has a significant effect on thermal aging. At moderate temperatures (up to 70o) free sulfur and polysulfide cross-links retard oxidation. However, with an increase in temperature, the rearrangement of polysulfide bonds, in which free sulfur can also be involved, leads to accelerated oxidation of vulcanizates, which turn out to be unstable under these conditions. Therefore, it is necessary to select a vulcanization group that provides the formation of resistant to rearrangement and oxidation of cross-links.
To protect rubber from thermal aging, antioxidants are used that increase the resistance of rubbers and rubbers to oxygen, i.e. substances with antioxidant properties - primarily secondary aromatic amines, phenols, bisfinols, etc.

1.2.3. Ozone aging.

1.3. Antioxidants and antiozonants.

The most effective antioxidants and antiozonants are secondary aromatic amines.
They are not oxidized by molecular oxygen either in dry form or in solutions, but are oxidized by rubber peroxides during thermal aging and during dynamic operation, causing chain separation. So diphenylamine; N, N^-diphenyl-n-phenylenediamine is consumed by almost 90% during dynamic fatigue or thermal aging of rubber. In this case, only the content of NH groups changes, while the nitrogen content in the rubber remains unchanged, which indicates the addition of an antioxidant to the rubber hydrocarbon.
Antioxidants of this class have a very high protective effect against thermal and ozone aging.
One of the widely used representatives of this group of antioxidants is N,N^-diphenyl-n-phenylenedialin (diafen FF).

It is an effective antioxidant that increases the resistance of rubbers based on SDK, SKI-3 and natural rubber to the action of repeated deformations. Diafen FF colors rubber.
The best antioxidant to protect rubber from thermal and ozone aging, as well as from fatigue, is diafen FP, however, it is relatively highly volatile and is easily extracted from rubber with water.
N-Phenyl-N^-isopropyl-n-phenylenediamine (diaphen FP, 4010 NA, Santoflex IP) has the following formula:

With an increase in the size of the alkyl group of the substituent, the solubility of secondary aromatic diamines in polymers increases; increased resistance to water washout, reduced volatility and toxicity.
The comparative characteristics of diaphene FF and diaphene FP are given because in this work, studies are carried out that are caused by the fact that the use of diaphene FF as an individual product leads to its “fading” on the surface of rubber compounds and vulcanizates. In addition, it is somewhat inferior to diaphene FP in terms of protective action; has a higher melting point in comparison with the latter, which adversely affects its distribution in rubbers.
PVC is used as a binder (dispersion medium) to obtain a paste based on combinations of antioxidants diaphene FF and diaphene FP.

1.4. Polyvinyl chloride.

1.4.1. PVC plastisols.

1.4.2. The mechanism of gelatinization of plastisols.

2. Choice of research direction.

3. Specifications for the product.

3.1. Technical requirements.

3.1.1. Dispersion PD-9 must be manufactured in accordance with the requirements of these technical specifications according to the technological regulations in the prescribed manner.

3.2. Safety requirements.

3.2.2. Dispersion PD-9 is a low-toxic substance. In case of contact with eyes, rinse them with water. Remove product on skin by washing with soap and water.

3.3. Test methods.

3.3.1. At least three point samples are taken, then they are combined, thoroughly mixed and an average sample is taken by quartering.

3.3.2. Appearance definition. Appearance is determined visually during sampling.

3.3.3. Determination of crumb size. To determine the size of the PD-9 dispersion crumb, a metric ruler is used.

3.3.4. Determination of the mass of the PD-9 dispersion in a plastic bag. To determine the mass of the PD-9 dispersion in a plastic bag, a scale of the RN-10Ts 13M type is used.

3.3.5. Determination of Mooney viscosity. The determination of Mooney viscosity is based on the presence of a certain amount of the polymer component in the PD-9 dispersion.

3.4. Manufacturer's warranty.

3.4.1. The manufacturer guarantees the compliance of the PD-9 dispersion with the requirements of these specifications.
3.4.2. Guaranteed shelf life of PD-9 dispersion is 6 months from the date of manufacture.

4. Experimental part.

Preparation of anti-aging paste.

The order of loading the ingredients.

Determination of the rheological properties of anti-aging paste.

5. Obtained results and their discussion.

When studying the possibility of using PVC, as well as the composition of polar plasticizers as a binder (dispersion medium) to obtain pastes based on combinations of antioxidants diaphene FF and diaphene FP, it was found that the alloy of diaphene FF with diaphene FP in a mass ratio of 1: 1 is characterized by a low speed crystallization and a melting point of about 90°C.
The low crystallization rate plays a positive role in the manufacturing process of PVC plastisol filled with a mixture of antioxidants. In this case, the energy consumption for obtaining a homogeneous composition that does not delaminate in time is significantly reduced.
The melt viscosity of diaphene FF and diaphene FP is close to the viscosity of PVC plastisol. This makes it possible to mix the melt and plastisol in reactors with anchor-type mixers. On fig. 1 shows a diagram of the installation for the production of pastes. The pastes drain satisfactorily from the reactor before their pre-gelatinization.
It is known that the gelatinization process proceeds at 150°C and above. However, under these conditions, the elimination of hydrogen chloride is possible, which, in turn, is able to block the mobile hydrogen atom in the molecules of secondary amines, which in this case are antioxidants. This process proceeds according to the following scheme.
1. Formation of polymeric hydroperoxide during the oxidation of isoprene rubber.
RH+O2 ROOH,
2. One of the directions of decomposition of polymeric hydroperoxide.
ROOH RO°+O°H
3. Having formed the oxidation stages due to the antioxidant molecule.
AnH+RO° ROH+An°,
Where An is the antioxidant radical, for example,
4.
5. Properties of amines, including secondary ones (diaphene FF) to form alkyl-substituted ones with mineral acids according to the scheme:
H
R-°N°-R+HCl + Cl-
H

This reduces the reactivity of the hydrogen atom.

Table 4
Viscosity indicators according to Mooney paste (P-9)
Initial indicators Indicators after storing the paste for 2 months
10 8
13 14
14 18
14 15
17 25

By changing the content of PVC and antioxidants, it is possible to obtain pastes suitable for protecting rubber from thermal-oxidative and ozone aging, both based on non-polar and polar rubbers. In the first case, the PVC content is 40-50% wt. (paste P-9), in the second - 80-90% wt.
In this work, we study vulcanizates based on SKI-3 isoprene rubber. Physical and mechanical properties of vulcanizates using paste (P-9) are presented in tables 5 and 6.
The resistance of the studied vulcanizates to thermal-oxidative aging increases with an increase in the content of the anti-aging paste in the mixture, as can be seen from Table 5.
The indicators of change in the conditional strength of the regular composition (1-9) is (-22%), while for the composition (4-9) - (-18%).
It should also be noted that with the introduction of a paste that promotes an increase in the resistance of vulcanizates to thermal-oxidative aging, a more significant dynamic endurance is imparted. Moreover, explaining the increase in dynamic endurance, it is impossible, apparently, to limit ourselves only to the factor of increasing the dose of the antioxidant in the rubber matrix. Not the last role is probably played by PVC. In this case, it can be assumed that the presence of PVC can cause the effect of the formation of continuous chain structures, which are evenly distributed in the rubber and prevent the growth of microcracks that occur during cracking.
By reducing the content of anti-aging paste and thus the proportion of PVC (Table 6), the effect of increasing dynamic endurance is practically canceled. In this case, the positive effect of the paste is manifested only under conditions of thermal-oxidative and ozone aging.
It should be noted that the best physical and mechanical properties are observed when using an anti-aging paste obtained under milder conditions (pre-gelatinization temperature 100°C).
These conditions for making the paste provide a higher level of stability than a paste obtained by incubating for an hour at 140°C.
An increase in the viscosity of PVC in a paste obtained at a given temperature also does not contribute to the preservation of the dynamic endurance of vulcanizates. And as follows from Table 6, dynamic endurance is greatly reduced in pastes thermostated at 140°C.
The use of diaphene FF in composition with diaphene FP and PVC makes it possible to solve the problem of fading to some extent.

Table 5

1-9 2-9 3-9 4-9
1 2 3 4 5
Conditional tensile strength, MPa 19.8 19.7 18.7 19.6
Nominal stress at 300%, MPa 2.8 2.8 2.3 2.7

List of symbols.

PVC - polyvinyl chloride
Diaphen FF – N,N^ – Diphenyl – n – phenylenediamine
Diaphen FP - N - Phenyl - N ^ - isopropyl - n - phenylenediamine
DBP - dibutyl phthalate
SKI-3 - isoprene rubber
P-9 - anti-aging paste

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