Thermal properties crystallization temperature

The effects of nano-structured carbon fillers [fuUerene C60, single wall carbon nanotube (SWCNT), carbon nanohom (CNH), carbon nanoballoon (CNB), and ketjenblack (KB) and conventional carbon fillers [conductive grade and graphi-tized carbon black (CB)]] on conductivity (resistance), thermal properties, crystallization, and proteinase K-catalyzed enzymatic degradation of PLA films were investigated by Tsuji et al. [70]. The researchers found that the addition of 1 wt% SWCNT effectively decreased the resistivity of PLA film compared with that of conventional CB. The crystallization of PLA further decreased the resistivity of films. The addition of carbon fillers, except for C60 and CNB at 5 wt%, lowered the glass transition temperature, whereas the addition of carbon fillers, excluding... 

Mechanical and Thermal Properties. The first member of the acrylate series, poly(methyl acrylate), has fltde or no tack at room temperature it is a tough, mbbery, and moderately hard polymer. Poly(ethyl acrylate) is more mbberflke, considerably softer, and more extensible. Poly(butyl acrylate) is softer stiU, and much tackier. This information is quantitatively summarized in Table 2 (41). In the alkyl acrylate series, the softness increases through n-octy acrylate. As the chain length is increased beyond n-octy side-chain crystallization occurs and the materials become brittle (42) poly( -hexadecyl acrylate) is hard and waxlike at room temperature but is soft and tacky above its softening point. 

Precursor Structure Effects. The precursor structure can impact a broad range of properties, including crystallization temperature, the formation of intermediate phases during thermal treatment and film density, among other properties. Table 2.4 reports some of the key precursor properties that may affect densification and crystallization behavior, as well as the final film microstructure. 

Thermal Properties. The DPP portion of block copolymers crystallizes on heating at 290°C and then melts at 480°C. The DMP portion of block copolymers does not crystallize thermally but can be caused to crystallize by treatment with a suitable solvent, such as a mixture of toluene and methanol the crystallized DMP then melts at 258°C. The glass-transition temperatures of the homopolymers are too close (221°C for DMP, 228° for DPP) to permit observation of separate transitions, either in block copolymers or blends of the homopolymers. 

Thermal Properties of 1 1 Copolymers. Random copolymers made from equimolar amounts of the two phenols have a glass transition temperature of T0 = 226°C. They are amorphous and will not crystallize either thermally or by solvent treatment (Figure 6). 

The thermophysical properties, such as glass transition, specific heat, melting point, and the crystallization temperature of virgin polymers are by-and-large available in the literature. However, the thermal conductivity or diffusivity, especially in the molten state, is not readily available, and values reported may differ due to experimental difficulties. The density of the polymer, or more generally, the pressure-volume-temperature (PVT) diagram, is also not readily available and the data are not easily convertible to simple analytical form. Thus, simplification or approximations have to be made to obtain a solution to the problem at hand. 

The thermal properties of the polymers reported in Table A.2 and Table A.3 were obtained by using a Perkin-Elmer Differential Scanning Calorimeter Model DSC-7 using a heating rate of 20°C/min. The specific heat was obtained using a heating rate of 10°C/min. For semicrystalline material, the heat of fusion was obtained from the measured specific heat curves. The crystallization temperature was obtained at 20°C/min cooling rate. 

As long as thermally induced crystallization (see above) is avoided, PCTFE exhibits excellent mechanical properties. It also has an excellent resistance to creep.83 The addition of glass fibers (typically 15%) improves high-temperature properties and increases hardness, but also increases brittleness.86... 

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