Poly blends crystallization temperature

The compatibility of blends of poly (vinyl chloride) (PVC) and a terpolymer (TP) of ethylene, vinyl acetate, and carbon monoxide was investigated by dynamic mechanical, dielectric, and calorimetric studies. Each technique showed a single glass transition and that transition temperature, as defined by the initial rise in E" at 110 Hz, c" at 100 Hz, and Cp at 20°C/min, agreed to within 5°C. PVC acted as a polymeric diluent which lowered the crystallization temperature, Tc, of the terpolymer such that Tc decreased with increasing PVC content while Tg increased. In this manner, terpolymer crystallization is inhibited in blends whose value of (Tc — Tg) was negative. Thus, all blends which contained 60% or more PVC showed little or no crystallinity unless solvent was added. 

FIgyre 2.16 Variation of melting temperature with crystallization temperature for (O) poly(8-caprolactone) and ( ) poly(E-caprolactone) in a blend with poly(4-hydroxystyrene) (85% weight fraction of PCL). (From Ref. 15.)... 

Differential scanning calorimetry was used to study the non-isothermal crystallization behavior of blends of poly(phenylene sulfide) (PPS) with the thermotropic liquid-crystalline copoly(ester amide) Vectra-B950 (VB) [126], The PPS crystallization temperature and the crystallization rate coefficient increased significantly when 2-50% VB was added. The Ozawa equation was shown to be valid for neat PPS as well as for the blends. The values of the Avrami exponents matched well against those determined previously using isothermal analysis, and they are independent of the concentration of VB. 

Tsuji (2002) conducted an investigation into the hydrolysis of an amorphous form of PLA, to determine the effects of L-lactide content, tacticity and enantiomeric polymer blends. In this work four samples were prepared—poly(D,L-lactide), poly(L-lactide), poly(D-lactide) film and the blend sample of poly(L-lactide) and poly(D-lactide). The results are sununa-rized in Table 7.4, which also covers a complementary study that explored the effects of hydrolysis in terms of molecular weight and its distribution, glass transition temperature, crystallization temperature, melting temperature and mechanical properties. 

The effects of molecular orientation on the crystallization and polymorphic behavior of SPS and SPS/poly(2,6-dimethyl-l,4-phenylene oxide) (PPO) blends were studied with wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry [37]. The oriented amorphous films of SPS and SPS/ PPO blends were crystallized under constraint at crystallization temperatures ranging from 140 to 240 °C. The degree of crystallinity was lower in the cold-crystallized oriented film than in the cold-crystallized isotropic film. It was inferred that the oriented mesophase was obtained in drawn films of SPS and that the crystallization of SPS was suppressed in that phase. The WAXD measurements showed that the crystal phase was more ordered in SPS/PPO blend than in pure SPS under the same annealing conditions. It was principally due to the decrease in the mesophase content. The crystal forms were found to be dependent on the crystallization temperature, blend composition, and... 

Figure 5.6 Morphology-induced dependence of the crystallization temperature (Tf) of the EO block on total polybutadiene (PB) concentration in binary blends of a polybutadiene homopolymer and a B-EO diblock copol5uner. Data obtained from a poly(ethylene oxide) homopolymer are included (dashed line) for reference. (Reprinted with permission from Chen, H.-L., Hsiao, S.-C., Lin, T.-L., Yamauchi, K., Hasegawa, H. and Hashimoto, T. Macromolecules 34 671, (2001). Copyright 2001 American Chemical Society.)...

Fig. 11.1 Spherulite growth rate of poly(vinylidene fluoride) as a function of crystallization temperatures in blends with poly(methyl methacrylate) at indicated...

Fig. 11.4 Plot of spherulite growth rates of poly(pivalolactone) as a function of composition in blends with poly(vinylidene fluoride) (circles), pivalolactones and poly(3-hydroxybutyrate) in cellulose acetate butyrate (squares), at indicated crystallization temperatures. (Data from (2) and (5))...

Fig. 11.5 Plot of relative fraction transformed against log time for poly(e-caprolactone) in a 30/70 blend with poly(hydroxy ether) of bisphenol A phenoxy for a set of isothermal crystallization temperatures. (Data from (17))...

Two typical examples of the overall crystallization rate, expressed as either fo s or peak time, are given in Fig. 11.7 for poly(ethylene oxide)-poly(vinyl phenol) (18) and for poly(aryl ether ether ketone)-poly(ether imide) (19) in Fig. 11.8. The dependence of the crystallization rates on composition are similar to one another and are closely related to the results for other binary mixtures. The overall crystallization rates follow the pattern established for spherulite growth rates. At the higher crystallization temperatures only a modest decrease in the rate is observed with the addition of the noncrystallizing component However, with a decrease in the crystallization temperature the polymeric diluent becomes more effective in reducing the rate. Because of the retardation in the rate with dilution a much wider range in isothermal crystallization temperatures can be studied. Thus, for the more dilute blends a maximum in the rates with temperature can be observed. This is... 

Fig. 11.7 Plot of half-time, tq.s, for the crystallization of poly(ethylene oxide) against crystallization temperatures of blends of poly(ethylene oxide)-poly(p-vinyl phenol). Composition o 100/0 90/10 80/20 70/30 A 65/35. (From Pedrosa etal. (18))...

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