Semicrystalline polymers melting

Semicrystalline partial aromatic polyamides, 139 Semicrystalline polyesters, 45 Semicrystalline polymers, melting temperatures of, 33 Semirigid foams, 203 tests for, 244 Sensitization, 246... 

There is a near-step increase in specific volume when the crystals in a semicrystalline polymer melt. In the pressure-volume-temperature (p-V-T) data for polyethylene (Fig. 6.10a), the crystalline phase finishes melting at 130 °C... 

For semicrystalline polymers, melting temperature (Tu) is correlated to the thickness of crystalline lamellae. If all other variables are held constant, thinner lamellae will melt at lower temperatures than thicker ones. Thus, the melting temperature Tu, defined as the maximum temperature within a melting regime M, can be used to approximate the lamellar thickness. Within the first DSC run curves of polypropylenes prepared by 9a, typically several melting transitions. Mi, M2, and M3, with maxima 7mi, Tm2, and Tu, can be seen (Figure 9.13). 

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. 

Aliphatic polyesters are low-melting (40-80°C) semicrystalline polymers or viscous fluids and present inferior mechanical properties. Notable exceptions are poly (a-hydroxy acid)s and poly (ft -hydroxy acid)s. 

Wholly aromatic polyesters, in which both R1 and R2 are aromatic, are either high-7 amorphous polymers or veiy high melting semicrystalline polymers that often exhibit liquid crystalline properties. 

Crystalline polyimide powders, 304 Crystalline transition temperature. See Melting temperature (Tm) Crystallization rate, for processing semicrystalline polymers, 44 CTE. See Coefficient of thermal expansion (CTE)... 

The nature of the heat of fusion AHu deserves particular attention, for it represents the heat required to melt one mole of crystalline units it does not refer to the latent heat AJT required to melt such crystallinity as may occur in a given semicrystalline polymer. The depression of the melting point Tm, already defined as the maximum temperature at which crystalline regions may coexist with amorphous poly-... 

In contrast to the mature instrumental techniques discussed above, a hitherto nonexistent class of techniques will require substantial development effort. The new instruments will be capable of measuring the thermal (e.g., glass transition temperatures for amorphous or semicrystalline polymers and melting temperatures for materials in the crystalline phase), chemical, and mechanical (e.g., viscoelastic) properties of nanoscale films in confined geometries, and their creation will require rethinking of conventional methods that are used for bulk measurements. 

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... 

PTT is a semicrystalline polymer with a DSC peak melting point of 228 °C (Figure 11.5). The equilibrium melting points, 7m°, obtained from the... 

Based on the results obtained to date, which have been summarized above for several different semicrystalline polymers— linear and low density (branched) polyethylene, polytrimethylene oxide, polyethylene oxide and cis polyisoprene—it is concluded that the relatively fast segmental motions, as manifested in Tq, are independent of all aspects of the crystallinity and are the same as the completely amorphous polymer at the same temperature. Furthermore, it has previously been shown that for polyethylene, the motions in the non-crystalline regions are essentially the same as those in the melts of low molecular weight ii-alkanes. (17)... 

The results discussed above indicate that the further study of the spin relaxation parameters possess the potential to develop our understanding of the structure of the non-crystalline regions of semicrystalline polymers. Significant progress has already been made in relating the spin-lattice relaxation parameters with that of the pure melt. The linewidths, or spin-spin relaxation parameters, of semicrystalline polymers have been... 

A novel approach is used to compatibilise a blend without addition of premade copolymers or functionalisation of polymers lacking functional groups. Solid-state shear pulverisation (S3P) processes polymers at temperatures below the melt transition (for semicrystalline polymers) or the glass transition (for amorphous polymers). The polymer, introduced as pellets or flakes into the pulveriser. 

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