Copolymer thermal glass transition

For all runs, thermal analysis of the resulting polymers showed that only one glass transition temperature could be found. This corresponded to the Tg of the VAc/VEOVA copolymer. Lower glass transition temperatures were found for the semibatch runs, perhaps due to slightly improved VEOVA incorporation. 

Thermal analysis are widely used for polymers and copolymers analysis. Glass transitions, melting, and decomposition processes are analyzed. Since the glass transition temperature Tg is marked by changes in the thermal capacity, expansion coefficient, and rigidity, TMA technique as well as DSC may be used. Tg increases with molecular mass up to certain values. Plasticizers and water depress this temperature. Thermal stability and influence of antioxidants and fillers may be analyzed by TG or DSC, under oxygen. 

The properties of SAN resins depend on their acrylonittile content. Both melt viscosity and hardness increase with increasing acrylonittile level. Unnotched impact and flexural strengths depict dramatic maxima at ca 87.5 mol % (78 wt %) acrylonitrile (8). With increasing acrylonitrile content, copolymers show continuous improvements in barrier properties and chemical and uv resistance, but thermal stabiUty deteriorates (9). The glass-transition... 

Bowmer and Tonelli [161] have also observed that the magnitude of the glass transition (ACp) increases with the ethylene content of the copolymer, goes through a maximum at about 30 mol%, and then continually decreases until no glass transition is observed at more than 80 mol% of ethylene. This may constitute further evidence in favor of the explanations put forward by Naqvi for the thermal stability behavior of similar copolymers reported by Braun et al. [159]. Initially, with increasing content of nonpolar ethylene units in the co-... 

The thermal properties of block copolymers are similar to physical blends of the same polymer segments. Each distinct phase of the copolymer displays unique thermal transitions, such as a glass transition and/or a crystalline melting point. The thermal transitions of the different phases are affected by the degree of intermixing between the phases. 

The most commonly used siloxane modifiers are those having phenyl, trifluoro-propyl and cyanopropyl substituents. Introduction of phenyl units into the polydimethylsiloxane backbone either in the form of methylphenylsiloxane or diphenyl-siloxane increases the thermal and oxidative stability, glass transition temperature and the organic solubility characteristics of the resulting copolymers. At low levels (5-10 percent by weight) of incorporation, bulky phenyl groups also break up the regularity of polydimethylsiloxane chains and inhibit the crystallization (Tc... 

Preparation and thermal crosslinking reactions of oc, -vinylbenzyl terminated polysulfone-b-polydimethylsiloxane, ABA type block copolymers have been discussed 282,313) However, relatively little characterization was reported. Molecular weights of polysulfone and PDMS segments in the copolymers were varied between 800-8,000 and 500-11,000 g/mole, respectively. After thermal curing, the networks obtained showed two phase morphologies as indicated by the detection of two glass transition temperatures (—123 °C and +200 °C) corresponding to PDMS and polysulfone phases, respectively. No mechanical characterization data were provided. 

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