Rubber aging study aged properties

ROMP processes are unique in that they offer unsaturated polymer products with properties between those of saturated polyethylene and the highly unsaturated polybutadienes. These polyalkenamers have been the subject of intense study by companies dealing in speciality polymers. In the 1970 s the ROMP product of cyclopentene attracted attention as a replacement for natural rubber, due to its good strength and ageing properties. Although the elastomer was never commercialized, as its overall characteristics did not meet requirements, the work stimulated research into ROMP of other cyclic alkene... 

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). 

The thermal stability of NR and carboxylated styrene butadiene rubber (XSBR) lattices and their blends were studied by thermogravimetric methods by Stephen et The thermal degradation and ageing properties of these individual lattices and their blends were investigated with special reference to blend ratio and vulcanization techniques. As already described, as the XSBR content in the blends increased, their thermal stability was also found to increase. Among sulphur and radiation-vulcanized samples, radiation cured possessed higher thermal stability due to the higher thermal stability of carbon carbon crosslinks. 

The application of ionic liquids influenced on the cross-linking density of the vulcanizates, rheometric and mechanical properties of HNBR. We did not observed the influence of modification on curing time of EPR vulcanisates. The application of montmorillonites did not lead to a significant improvement in mechanical properties of EPR rubber. The ageing studies (thermal, atmospheric and under UV radiations) showed that the modification of montmorilonite with ammonium salts had strong effect on ageing properties of vulcanisates. 

E.M. Dannenberg. Primary structure and surface properties of carbon black— Part 1 a study of four ISAF type carbon blacks of varying structure. Rubber Age, 98,82-90,1966. 

Ostromyslensky [90] observed that rubber could be vulcanized in the absence of sulphur or its compounds if small quantities of aromatic nitro compounds, e.g. nitrobenzene, dinitro- or sym- trinitro-benzene, tetranitronaphthalene plus certain oxidizing compounds, such as benzoyl peroxide, were added to it. The resultant vulcanized rubber had mechanical properties not inferior to those of a product vulcanized by sulphur alone, and when free from accelerators it exhibited a greater resistance to ageing. Some metal oxides, such as PbO, CaO, BaO, promoted vulcanization by nitro compounds. Urea played the role of an accelerator of vulcanization. These observations have been confirmed in more recent studies by other workers. 

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... 

The temperature in the laboratory was fairly constant with an average temperature of 23.9°C and a standard deviation of 2.20°C. There were a few excursions below the lower 3a limit, but none above. For ageing studies in rubber systems, low temperatures would be less detrimental to properties than high temperatures and are considered of no significance in the present study. 

The ozone concentration in the troposphere during the daytime is typically about 1 pphm (parts per hundred million parts of air by volume) [20], Values up to 100 pphm were measured in some photochemical smog areas. The molecular mechanism of the ozone aging of diene based elastomers was studied in detail and is well understood [19,21], Products or intermediates different from those arising in autoxidation or photo-oxidation of polymers were identified ozonides (3), zwitterions (4), diperoxides (5), polyperoxides (6), polymeric ozonides (7) and terminal aldehydes (8). Reactivity of aminic antiozonants (AOZ) with these species accounts for the protection of rubbers against atmospheric 03. AOZ must also possess antioxidant properties, because the free radical processes are concerted with ozonation due to the permanent presence of oxygen. 

The efficacy of polyurethane and styrene butadiene rubber (SBR) as binders for ground rubber prepared from waste tires was compared to a formulation of a compound developed without binder. Without binder, the effect of both sulfur and accelerator content on tensile properties are studied, as well as the effect of ageing on these properties [29]. The suggested uses of the unbound product include rubber blocks, and ballast mats for railway applications. 

Ismail H, Mohamad Z, Bakar AA (2003) A comparative study of processing, mechanical properties, thermo-oxidative aging, water adsorption, and morphology of rice husk powdCT and silica fillers in polystyrene/styrene butadiene rubber blends. PolymCT Plast Tech Eng 42 (1) 81-103... 

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