Resistance aging and

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

EPDM is a terpolymer of ethylene, propylene, and a small amount (<10%) of an unsaturated diene third monomer to provide a cure site. Unlike the elastomers previously discussed, the unsaturation in EPDM is not in the main chain, but it is pendent to the chain. Peroxide cure gives superior aging resistance and low compression set. 

Compared with the major vinyls cellulose acetate plastics have a high water absorption, poor electrical insulation characteristics, limited aging resistance and... 

Transparent polyethylene is characterized by an enhanced freeze- and heat-aging resistance, and also by a... 

NR can be cross-linked by a blocked diphenyl methanes diisocyanate to produce urethane crosslinks. The cross-linking agent dissociates into two quinonedioxime molecules and one diphenyl methane diisocyanate. The quinone reacts with the rubber via a nitroso group and forms cross-links via diisocyanato group. The performance of this system in NR is characterized by excellent age resistance and outstanding reversion resistance. 

The other additives in the compound can also influence ageing as we can see in Table 3.12, which displays the effect of silica in combination with two different protective agents. In one case the silica degrades the ageing resistance and in the other silica enhances ageing behaviour. 

Table 4.111 Schematic comparison of ageing resistance and chemical behavionr of some TPEs...

SBS and SEBS have many common features but mainly differ in ageing resistance and chemical behaviour ... 

In 1931 Du Pont introduced the first synthetic elastomer, polychloroprene (Neoprene , Duprene ), and Thiokol Corporation introduced a polysulfide rubber called Thiokol . Polychloroprene, although veiy expensive compared to polyisoprene, has superior age resistance and chemical inertness. It is also nonflammable. 

This class of blends was introduced in 1989, as a lower cost alternative to EPDM/PP blend. Its heat-aging resistance and use temperature limits are, however, inferior to the EPDM/PP blends. 

For semi-efficient vulcanization systems, intermediate sulfur level of 1-2 phr and 2.5-1 phr of accelerator are often used. The vulcanizates have physical properties intermediate between those of conventional vulcanization and efficient vul-canizationvulcanizates. hi fact, they give some improvements in reversion, ageing resistance and compression set compared with conventional vulcanizationvulca-nizates, but resistance to fatigue and low temperature crystallization is impaired. However, they have higher scorch safely, particularly when sulfenamide accelerators are used in the system. 

Like halobutyl rubber (HHR), ethylene propylene rubber (EPR) has a fully saturated backbone and has only unsaturation points available for vulcanization crosslinking in very small percentages of the pendent diene modifier (EPDM). It has good aging resistance and resistance to fatigue even when heavily loaded with fillers and is utilized in passenger tire white sidewalls. 

Optimum properties Very excellent ageing resistance and medium strength Good environmental ageing resistance, some oil resistance, self-... 

It is commonly desirable to minimize autoxidation (as when it is desired to improve ageing resistance) and in principle there are two main methods of achieving this by chemical means. 

Among binders, styrene-butadiene latexes dominate beside modified starches. Styrene-acrylate dispersions are spedalties and of high importance for impressive prints. Additionally acrylate dispersions have an excellent brightness and ageing resistance and are less odorous. Future requirements of coating process conditions, on paper characteristics and printing technologies forced the production of tailor-made binders with very specific property profiles. 

Copolymers of ethylene and methyl acrylate, and ethylene acrylics, have a fully saturated backbone, providing heat-aging resistance and inherent ozone resistance. They are compounded in a Banbury mixer and fabricated by injection molding, compression molding, resin transfer molding, extrusion, and calendering. 

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