Poly equilibrium melting temperature

Melting process and the equilibrium melting temperature of poly-chlorotrifluoroethylene. J. Research Natl. Bur. Standards 66 A, 13—28 (1962). 

Figure 2. Equilibrium melting temperatures T° plotted as a function of optical purity for poly(a-methyl-a-ethyl 3-propiolactone). 

The equilibrium melting temperature of the stereocomplex remains the same over the whole range of composition, except at high poly-R excesses where it decreases slightly. 

Figure 5, Equilibrium melting temperature T of a racemate of poly-(a-methyl-a-ethyl 3-propiolactone) (circles) and melting temperature of the polymer in excess (triangles). A filled symbol indicates that poly-S is in excess, whereas an open symbol indicates that poly-R is in excess.

For polymer blends in which one component is crystalline the melting behaviour depends on circumstances. For immiscible blends, where the components are phase separated (prior to crystallisation) and act independently, the crystal melting temperature will be that of the homopolymer. In miscible blends, where the amorphous phase contains both components, the melting temperature will be lower than the equilibrium melting temperature for the crystallisable homopolymer, i.e. the crystalline polymer exhibits a melting point depression as discussed above. The Nishi and Wang approach (Sect 3.2) has been used to estimate the magnitude of the interaction parameters in a niunber of blends (Sect. 7). Poly(e-caprolactone) blends are often semi-crystalline and the above considerations, therefore, apply to many PCL blends. 

Fig. 6. A graph of the variation in growth rate with temperature for poly(hydroxybutjrrate), showing the tjrpically observed bell-shaped temperature dependence, with the crystallization rate reducing to zero well before the equilibrium melting temperature ( 198°C for this poljrmer) and, after passing through a maximum, again reducing to zero before the glass-transition temperature ( 0 = C). (Unpublished data of the author.)...

Calculations based on Eq. (2.35) for the exponential molecular weight distribution indicate that the equilibrium melting temperatures of the poly(ethylene oxides), and presumably other polymers as well, are sensitive to the width of the distribution. Significant changes in the equilibrium melting temperature can occur. For example. 

Fig. 4.6 Equilibrium melting temperature of poly( 1,4-butylene adipate) in its blends with poly(vinylidene fluoride). The curves are calculated according to theory assuming that...

It has been found that using the modification proposed by Baur gives better agreement than the ideal Flory theory. For example, using extrapolated equilibrium melting temperatures gives excellent agreement with experimental results for copolymers of poly(L-lactide-meso lactide).(67a)... 

Fig. 5.10 Plots of extrapolated equilibrium melting temperature of syndiotactic poly-(propylene)-l-octene copolymers as a function of comonomer concentration. Solid line calculated according to Eq. (5.42). (From Thomann, Kressler and Miilhaupt (71))...

Qualitatively similar melting point depressions are observed in long chain branched poly(ethylene terephthalate)(152) and poly(phenylene sulhde).(153) The extrapolated equilibrium melting temperatures of poly(phenylene sulhde) decrease by 11 °C with a modest concentration of long chain branches. Coincidentally, the extrapolated equilibrium melting temperatures of poly(ethylene terephthalate) also decrease by 11 °C for the range of branch concentrations studied. 

Fig. 6.6 Plot of observed melting temperatures and extrapolated equilibrium melting temperatures O of poly(aryl ether ketones) as a function of mole fraction of ketone linkage.

Fig. 7.2 The extrapolated equilibrium melting temperature of poly(tetrahydrofuran) networks as a function of molecular weight between cross-links. Filled and open circles represent unimodal and bimodal networks respectively. Solid curve calculated from Eq. 7.10. (From Roland and Buckley (21))...

Fig. 8.6 Comparison of experimental extrapolated equilibrium melting temperatures of poly(chloroprene) at various elongation ratios with those predicted. O experimental results ...

Fig. 8.8 Plot of reciprocal of extrapolated equilibrium melting temperature against f( ) according to Eq. (8.47) for cis-poly(isoprene).(39)...

There are a few polymers, such as polyfbutylene terephthalate) [178], poly-(trimethylene terephthelate) [179], poly(pivalolactone) [180,181], poly(methylene oxide) [182], linear polyethylene over an extended temperature range [183-185], and isotactic poly(propylene) [186-190], that crystallize in a temperature interval well removed from T, for which III-II regime transitions have been reported but without a maximum in the rate. There are many problems associated with the proper assignment of this transition. A major problem is the correct selection of the equilibrium melting temperature. This turns out to be a cmcial matter. 

Li and co-workers [63] studied the crystallisation and melting behaviour of poly(]3-hydroxybutyrate (P-HB)-co-P-hydroxyvalerate (P-HV)) and a blend of poly(P-HB-co-P-HV)/polypropylene carbonate (30/70 w/w) using DSC and FT-IR spectroscopy. Transesterification occurred between poly(P-HB-co-P-HV) and polypropylene carbonate during the melt blending process. During crystallisation from the melt, the crystallisation temperature of the blend decreased by 8 °C compared with that of neat poly(P-HB-co-P-HV) and the melting temperature decreased by 4 °C. This indicated that the presence of polypropylene carbonate reduced the perfection of the poly(P-HB-co-P-HV) crystals, inhibited by the crystallisation of poly(p-HB-co-P-HV) and weakened its crystallisation ability. The equilibrium melting temperatures of... 

The melting temperature of a sample of poly(decamethylene adipate) with a number-average degree of polymerization (x ) of 3 was found to be 65°C. was found to be 75°C for a sample of the same polymer with x = 10. Estimate the equilibrium melting temperature for poly(deca-methylene adipate)... 

Blending with a miscible component usually alters the thermodynamic and kinetic environments and thus affects the crystalline structure of polymorphic polymers. For example, formation of the s-PS p-form crystals is favored in blends of s-PS with miscible components such as a-PS, poly(2,6-dimethyl-p-phenylene oxide), and poly(styrene-co-a-methyl styrene) [125]. This is attributed to the lowered equilibrium melting temperature (T ) and decreased crystallization rate of s-PS upon blending. 

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