Toughness semicrystalline polymers

Polyamides (PAs) are the polymers containing the amide repeating linkage -CONH- in the polymer backbone. They are tough, semicrystalline polymers, characterized in their majority by moderate production cost and easily manipulated melt processing. The sequence of amide bonds along the polymer chain defines two polyamide categories (Scheme 2.1) AB and AABB. 

Polyamides, often also lefeiied to as nylons, are liigli polymers which contain the amide repeat linkage in the polymer backbone. They are generally characterized as tough, translucent, semicrystalline polymers that ate moderately low cost and easily manipulated commercially by melt processing. 

Poly(phenylene sulfide) (PPS) is another semicrystalline polymer used in the composites industry. PPS-based composites are generally processed at 330°C and subsequently cooled rapidly in order to avoid excessive crystallisation and reduced toughness. The superior fire-retardant characteristics of PPS-based composites result in appHcations where fire resistance is an important design consideration. Laminated composites based on this material have shown poor resistance to transverse impact as a result of the poor adhesion of the fibers to the semicrystalline matrix. A PPS material more recently developed by Phillips Petroleum, AVTEL, has improved fiber—matrix interfacial properties, and promises, therefore, an enhanced resistance to transverse impact (see PoLYAffiRS containing sulfur). 

The model has also been found to work well in describing the mechanics of the interface between the semicrystalline polymers polyamide 6 and polypropylene coupled by the in-situ formation of a diblock copolymer at the interface. The toughness in this system was found to vary as E- where E was measured after the sample was fractured (see Fig. 8). The model probably applied to this system because the failure occurred by the formation and breakdown of a primary craze in the polypropylene [14],... 

Semicrystalline polymers, 20 351, 352, 588 toughness of, 20 354 Semicrystalline resins, 19 537 Semicrystalline thermoplastics, melting temperature of, 19 538t Semiefficient (semi-EV) sulfur... 

The individual spherulite lamellae are bound together by tie molecules that are present in more than one spherulite. Sometimes these tie segments form intercrystalline links, which are threadlike structures, that are important in developing the characteristic good toughness found in semicrystalline polymers. They act to tie together the entire assembly of spherulites into a more or less coherent package. ... 

The simplest diene rubber for hydrogenation is BR. The structure of the hydrogenated BR (HBR) depends on the different microstructures present in BR. Hydrogenation of BR with high 1,4 structure converts this elastomeric polymer into a tough semicrystalline... 

For instance, the Tg of PP depends strongly on its tacticity. Atactic PP has a Tg—19 C and is used in bitumen and hot-melt adhesive formulations, while for isotactic PP, it is approximately -8°C. The latter is a tough, semicrystalline plastic used in packaging films. The Tg of syndiotactic form of PP can be as high as ISO C Sophisticated catalyst systems even aUow synthesis of polymers that have ordered blocks of atactic materials and isotactic materials on the polymer chains. 

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