Aging and Heat Resistance

CR M-type vulcanizates, especially those that contain optimized antioxidants and crosslinking systems and low volatility plasticizers, display good heat resistance. 

They neither soften nor harden over a long period of stress remaining serviceable and elastic. 

In the ASTM D 2000 and SAE J 200 systems, CR is positioned with respect to thermal aging between NR and CSM. 

The continuous service temperature in accordance with VDE 0304, Part 2 (25,000 h), is 80°C. Optimized vulcanizates for automotive application can perform for 1000 h at 100°C-110°C and wdl survive short- or medium-term exposure up to 120°C. 

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ISO 188, Rubber, vulcanized or thermoplastic - Accelerated ageing and heat resistance tests (available in English only), 1998. 

Currently, the polyisoprene vulcanized offers many attributes of great interest at a technological perspective, included damping, mechanical, age and heat resistance. 

ISO 188 2011 Rubber, Vulcanized or Thermoplastic. Accelerated Ageing and Heat Resistance Tests. 

The inherent properties of polymers of the poly isobutylene family, particularly the chemical inertness, age and heat resistance, long-lasting tack, flexibility at low temperatures, and the favorable FDA position on selected grades, make these products commercially attractive in a variety of pressure-sensitive and other adhesives, in automotive and architectural sealants, and in coatings. An added dimension is achieved in the blendability of the polyisobutylene polymers with each other and with other adhesive polymers such as natural rubber, styrene-butadiene rubber, EVA, low molecular weight polyethylene, and amorphous polypropylene to achieve specific properties. They can, for example, be blended with the highly unsaturated elastomers to enhance age and chemical resistance. A description of poly isobutylene polymer family use in adhesive and sealant applications follows. 

The polyester-esters were especially developed for their combination of heat ageing and UV resistances but performances can be lower versus low temperatures and hydrolysis. COPEs are in the Shore D hardness range. 

ASTM A561 Hot rolled and cold finished age hardening stainless and heat resisting steel bars, wire and shapes G4303 G4309... 

Accelerated aging or heat resistance tests Heat resistance and accelerated air aging test... 

As discussed previously, fluorocarbon elastomers are chemically very stable. They exhibit a unique combination of properties, such as resistance to heat, aggressive chemicals, solvents, ozone, and light in which they excel over other elastomeric materials. Moreover, they have a very good high-temperature compression set and flexibility at low temperatures. A comparison of heat aging and oil resistance of typical FKM and several other elastomeric materials is in Table 5.7.41... 

Styrene-butadiene rubber (SBR) is a random polymer made from butadiene and styrene monomers. It possesses good mechanical property, processing behavior, and can be used like natural rubber. Moreover, some properties such as wear and heat resistance, aging, and curing property are even better than in natural rubber. Styrene-butadiene rubber was the first major synthetic rubber to be produced commercially. Now it has become the most common rubber with the largest production and consumption in the synthetic rubber industry. It can be widely used in tire, adhesive tape, cables, medical instruments, and all kinds of rubberware. 

Important properties of these raw materials are the elasticity behavior given over a wide temperature range in cold and heat and the excellent aging and weathering resistance. Thus, various applications, above all outdoors, are possible. They are applied in nearly all fields of industry, for which special formulations are available according to the requirements and the material combinations to be sealed. The manufacturers show partly very detailed information on these products, which has to be referred to at this point. 

The use of ACECs as modifiers for CECs makes it possible to preserve the desirable processing characteristics of epoxy resins and to improve the mechanical strength, elongation under load and heat resistance. The thermal stability of the crosslinked materials does not depend on the type of modifier. This statement concerns both the thermo oxidative aging in the isothermal and the dynamic conditions. 

Chloroprene rubber (CR) is perhaps the most natural rubberlike of all synthetic plastics or elastomers, particularly with regard to its dynamic response. CRs are a family of elastomers with a property profile that approaches that of natural rubber (NR) but that has better resistance to oils, ozone, oxidation, flame, aging, and heat. CRs are about 25% heavier than NR and do not have the low temperature flexibiUty of NRs. See dynamic elongation polychloroprene rubber/elastomer rabber. 

Advantages Most stable synthetic rubber adhesive, excellent oil resistance, easily modified by addition of thermosetting resins Good heat aging and water resistance uniform appearance, non-staining light color, disperses easily in hydrocarbon solvents low cost Excellent adhesion at cryogenic temperatures and excellent retention of elasticity and shock resistance at these temperatures... 

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