Crystallinity, and glass transition temperature

FIGURE 7.21 The effect of vinyl acetate content on the crystallinity and glass transition temperature of PEVAc. [Graph reconstructed from Johnson and Nachtrab, Ange. Macrom. Chem., 7, 134 (1969) and Reding et al., J. Polym. Sci., 57, 483 (1962).]... 

Relationship Between Molecular Structure and Composition of Poly(ethylene-co-p-MS) Copolymers. From above discussion, we have shown that poly(ethylene-co-p-MS) copolymers with a wide range of compositions can be achieved by varying the p-MS monomer concentration in the feed. To fully understand the properties of this new class of materials, it is very important to know the correlation between the copolymer compositions and their molecular structures. In this section, we focus on the effect of p-MS concentration on molecular weight, molecular weight distribution, melting point (Tm), crystallinity and glass transition temperature (Tg) of the copolymer. A series of copolymers with various p-MS concentrations were analyzed by GPC and DSC. 

Hydrogenation of the aminonitrile with a Raney catalyst leads to a family of branched diamines. Because of the branching, most of the aminonitriles and diamines are liquids at low temperature and have low freezing points. They have found markets as comonomers or curatives, since they lower polymer viscosity, crystallinity, and glass transition temperature. Catalytic hydrogenation of MGN with a Raney catalyst gives the branched-amine methylpentamethylenediamine, MPMD, and 3-methylpiperidine (3MP) shown in equation 3. The product is dependent on conditions and choice of catalyst. The MPMD was initially isolated from plant streams to develop the market. Many applications were found as a polymer additive in... 

Degree of Crystallinity and Glass Transition Temperature of the Rubber... 

Figure 5.12 The effect of degree of crystallinity and glass transition temperature on development of knotty tearing energy as a function of tear rate at 23 °C. (Reproduced from ref. 8).

Crystallinity and glass transition temperature of epoxy were increased with increase in multiwall carbon nanotnbe, MWCNT, concentration. MWCNT acted as nucleating agent, initiating formation of new crystallites. ... 

The degradation rate of bioresorbable polymers depends on their intrinsic properties such as reactivity, hydrophilicity, molecular weight, degree of crystallinity, and glass transition temperature. However, other external factors such as the degradation media, sterilisation and sample size also play a role in the degree of degradation. 

In cases where the copol5uners have substantially lower glass-transition temperatures, the modulus decreases with increasing comonomer content. This results from a drop in crystallinity and glass-transition temperature. The loss in modulus in these systems is therefore accompanied by an improvement in low temperature performance. However, at low acrylate levels (< 10 wt%), Tg increases with comonomer content. The brittle points in this range may therefore be higher than that of PVDC. 

The three polymers have different properties. 1,2-Polybutadiene is a hard and rough crystalline compound 1,4-polybutadiene is not. The crystalline and glass transition temperatures for cis- and rrans-1,4-polybutadiene are markedly different Tg is — 108 C for cis and 18°C for trans T, is 1°C for cis and 141°C for trans. The glass transition temperature Tg is the temperature below which an amorphous polymer can be considered to be a hard glass and above which the material is soft or rubbery Tm is the crystalline melting point where the crystallinity completely disappears. 

Other factors that affect the stress relaxation behavior of polymer fibers include, but are not limited to molecular weight, molecular orientation, molecular polarity, crystalhnity, and moisture or other additives. In general, the stress relaxation of polymer fibers decreases with increases in molecular weight, molecular orientation, molecular polarity, crystallinity, and glass transition temperature. However, the introduction of moisture or other small molecules into polymer fibers can facilitate faster stress relaxation since these small molecules can improve the molecular mobility of polymer chains. 

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