ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Trans-1,5-polypentenamer (TPP) has some similarity to natural rubber partly because of properties that relate to crystallinity and to the position of the crystalline melting point. This similarity makes TPP a unique rubber among other synthetic hydrocarbon polymers. Requirements for attaining a good balance of physical properties include adjustment of both micro and macrostructure with processability. Natta, Dall'Asta, Haas and Pampus have described the preparation of polypentenamers based on tungsten or molybdenum catalysts. Since Eleuterio made his disclosure, there have been many important contributions disclosing special conditions for preparing TPP or variations in catalyst preparation including many catalyst activators. Natta and Dall'Asta vulcanized both the TPP and the amorphous cis-1,5-polypentenamer (CPP). They showed that TPP (melting point 23°C) gives good tensile properties even in pure gum vulcanizates characteristic of rubbers that crystallize on stretching. CPP gave better low-temperature characteristics than other hydrocarbon elastomers (SBR rubber, propylene oxide/allyl glycidyl ether copolymer, cis-1,4-polybutadiene). For example, the CPP vulcanizates were less brittle down to -90°C measured by 100 per cent moduli and, in a comparison of temperatures at which retraction occurred, CPP showed a superiority. With CPP from 25°C to -70°C, both tensile strengths and moduli increased without appreciable variation of elongation at break. Since the crystalline melting point at rest is near 20°C for TPP, the elastic behavior is governed by this transition rather than the glass transition point (-90°C).The rate of crystallization for TPP is more rapid compared to natural rubber. Although vulcanization is a factor on elastic behavior, we suggest that further compromise may be necessary to balance the desirable properties related to crystallinity while maintaining elasticity at lower temperatures. The summary of the Haas paper noted that TPP rubber is outstanding except that the abrasion, wet skid and heat build-up are inferior to existing tread rubber types. Our efforts suggest that TPP is not inferior.In our examination of TPP's having varied or lowered melting points, vulcanizates (tread recipes) with good low temperature flexibility were developed from TPP with Tm of 5°C. Since tack and green strength are dependent on both the micro and macrostructure, properties lost by decreasing the trans content or the Tm were offset by increasing the molecular weight. With higher molecular-weight TPP, other properties such as heat build-up and abrasion were improved or made equivalent to other tire rubbers. Thus, by optimizing molecular weight, oil level and processability with the microstructure, a good balance of properties may be produced for TPP rubber.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760150508
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