Polyamide blocks, chemical structure

FIGURE S.1 Chemical structure of block copolymeric thermoplastic elastomers (TPEs) (a) styrenic, (b) COPE, (c) thermoplastic pol)oirethane, and (d) thermoplastic polyamide. 

Figure 13.2 Chemical structures of (a) polyamide and (b) polyether blocks polyamide block could be PA6 (x = 5) or PA12 (x = 11) and polyether block could be polyfethylene oxide) (PEO, y = 2) or polyftetramethylene oxide) (PTMO, y = 4)...

One initial response of scientists to this challenge was to design new polymers for packaging applications with chemical structures as close as possible to nature s building blocks namely derivatives of carbohydrates, polyamides and polyesters. Examples of this approach are discussed elsewhere in this book... 

Early hot melt adhesives were based on ethyl cellulose and animal or hide glues. These were later replaced by synthetic resins such as polyamides and ethylene-vinyl acetate copolymers. More recently a new class of compounds, referred to as block copolymers because of their unique chemical structure, have emerged. These latter compounds are copolymers of styrene and butadiene, isoprene, or ethylene-butylene which tend to widen the flexibility property range of hot melt adhesives. They probably represent the fastest growing segment of the hot melt adhesives market at the present time. Their primary application is in hot melt pressure sensitive adhesives. Polymers based on other than polyolefin resins are discussed in other chapters in this handbook. 

As indicated in the literature [4,6], although the (3 peak shows only little variation with the PA/PE ratio, the a peak decreases in temperature for lower PA/PE ratios and a shorter polyamide block length as observed in Figure 10. Such a lowering of the a peak is attributed to an internal plasticization coming from oligoether miscible components inside the polyamide-rich regions. Another possible interpretation could be that, since the immiscible polyamide and polyether components are linked by chemical bonds, the structure and mobility of each block affect the others [15]. 

PEBA exhibit a two-phase (crystalline and amorphous) structure and can be classified as a flexible nylon. Physical, chemical, and thermal properties can be modified by appropriate combination of different amounts of polyamide and polyether blocks [149], Hydrophilic PEBAs can be prepared which can have specific applications in medical devices. Similarly to other thermoplastic elastomers, the poiyamide-based ones find applications in automotive components, sporting goods conveyor belting, adhesives, and coatings [150]. In recent years the world consumption was approximately 6400 tons per year with about 80% in Western Europe and the rest equally split between the United States and Japan [143],... 

Thermoplastic elastomers are most commonly formulated from elastomeric polyurethane or block copolymers of polystyrene-elastomer, polyamide-elastomer, or polyether-elastomer bases. Thermoplastic elastomers are provided as a raw material in pelletized form for subsequent compounding. The internal domain structure that is required for thermoplastic-elastomeric performance has been established by specific considerations of blending and structural-chemical interactions. In compounding operations, specific temperature ranges are required to assure that phase separation does not occur in the TPE base polymer. 

Floors ana walls of structures are obvious areas where epoxy systems may be utilized to prevent deterioration from abrasion and chemical attack. Such systems are now to be found in original specifications. VTall surfaces may be coated viith epoxy systems based on solid resins dissolved in solvents and hardened with polyamines and/or polyamides. Porous surfaces, such as concrete blocks, are first prepared viith fillers to provide a smooth surface for application of coatings. 

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