Rubber compound ageing

Uncured rubber compounds, aged in the laboratory or external atmosphere, exposed to ozone or UV radiation including sunlight, suffer a reduction in their subsequent cured... 

Amines Ketone-amines Acetone-diphenylainine and acetone-aniline (I) Yes Main use in rubber compounds for good heat aging. 

Benzofuran derivatives and enolethers are offered as chemical antiozonants for light coloured rubber compounds. Benzofuran derivatives are used in CR and its blends with other rubbers and give ageing protection in addition to ozone protection. 

If natural rubber compounds are subjected to thermal aging plus fatigue, the conventional systems perform no better than EV systems. The compromise obtained by using semi-EV systems involves the balance between heat aging and flex life. 

Types of Latex Compounds. For comparison with dry-rubber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural rubber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also listed. The effects of curing ingredients, accelerator, and antioxidant are also listed. Table 24 also includes similar data for an SBR latex compound. A phenolic antioxidant was used in all cases. 

HAF (high-abrasion furnace black) highly reinforcing furnace carbon black increasing resistance of a rubber compound to abrasion, heat aging exposure of polymeric materials under specified conditions (temperature, time, presence or absence of air or oxygen, etc.) then testing them... 

The commercial significance of the ingredients used in rubber compounding to improve resistance to ageing accelerated work on the discovery, development, use and manufacture of new products. The development efforts were competitive in nature, each manufacturer claiming superiority of their products over the others. Some of the age retardants are listed below. 

Age resistor - Also known as an antioxidant, a chemical that when added to a rubber compound will retard deterioration due to heat, light, oxygen, alone or in combination thereof. 

Embrittlement - A rubber compound becoming brittle during a low or high temperature exposure or as a result of ageing. 

Raman and IR spectroscopic studies dealing with the qualitative and/or quantitative determination of rubber compounding ingredients, i.e., the elastomer itself [22, 26-31], fillers [32, 33], vulcanisation chemicals and other additives [34-37], are not included here. The same applies to studies dealing with the crosslinking of elastomers by means of chemicals other than sulfur or peroxide [38-41], self-crosslinking of elastomers blends [42-44], crystallisation (strain-induced) [45-48] and oxidation/ageing [49-53]. 

PVCA is a copolymer of vinyl chloride and vinyl acetate. It is a colorless thermoplastic solid with good resistance to water as well as concentrated acids and alkalis. It is obtainable in the form of granules, solutions, and emulsions. Compounded with plasticizers, it yields a flexible material superior to rubber in aging properties. It is widely used for cable and wire coverings, in chemical plants, and in protective garments. 

Rostler, K. S., Rubber Age 82, 678-88 (1958). Rubber compounding information sources, indexing, retrieving. 

Inorganic additives for rubber compounds also include materials that enhance performance under various accelerated stress conditions. Zinc oxide is an effective heat stabilizer for some types of elastomers. Iron oxide, lead compounds, barium salts, and specially treated clays, such as kaolinite, add performance margin in wet aging conditions. 

Wire coats good adhesion to brass coated steel wire and to adjoining rubber compounds, tear, fatigue, and age resistance... 

Anecdotal evidence suggests that rubber outsoles change over time leading to consumer perceptions of decreased performance. The purpose of this ageing study was two fold. First, the physical properties of a standard rubber compound were evaluated over time to quantify changes. Second, simple formula and process adjustments were made to see if it was possible to produce a rubber product that 1) exhibited... 

From previous accelerated and real time ageing studies, it is known that rubber compounds exhibit complex property changes over time (1,2). Oftentimes, this can lead to less than desirable characteristics in the rubber, such as increased stiffness, embrittlement, poor abrasion characteristics, and others. In thin latex rubber products, it is common practice to under cure the rubber. As the product ages, certain properties will tend to improve for a while before starting a decline. For example, latex rubber condoms are stored in hermetically sealed packages, which limit exposure to oxygen, ozone and UV therefore, their ageing characteristics are more predictable and less pronounced than tires or footwear outsoles, since they can establish a three to five year shelf-life (3). 

It is hypothesized that improved ageing characteristics of rubber compounds could be facilitated by reducing the amount of sulfur and/or under curing the... 

The final properties after one year of ageing in an ideal storage condition show how much a rubber compound changes. These changes indicate that rubber is a very dynamic system with many factors influencing its properties over time. 

A long-term natural ageing programme was started in 1958 when 19 rubber compounds were exposed at 3 locations. The final sets of test pieces were withdrawn in 1998 giving a total of 40 years of natural ageing. The results of the physical tests carried out at intervals over the 40 years have been published [1]. 

An accelerated heat ageing programme involving a total of 39 rubber compounds has been successfully completed. 

Compound F (styrene butadiene rubber - good ageing) ... 

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