A new family of terephthalate-based copolyesters has been found to exhibit high impact resistance combined with good thermal properties, ultraviolet stability, optical clarity, and low color. These engineering thermoplastic compositions were prepared using conformationally rigid cis/trans-2,2,4,4tetramethyl-1,3-cyclobutanediol [CBDO] and flexible C 2-C4 aliphatic glycols. The copolymers were amorphous when the CBDO (∼50/50 cis/trans) content was about 40 to 90 mol % of total diol. Glass transition temperatures were 80-168 °C, depending on the proportion of rigid CBDO units. Impact resistance was inversely proportional to CBDO content, and notched Izod values as high as 1000 J/m were obtained. Both high Tg (>100 °C) and high impact (250-750 J/m) can be realized simultaneously for compositions containing about 50-80 mol % CBDO. Accelerated weathering indicated good inherent resistance of 1,3-propanediol/CBDO copolyterephthalate to yellowing under ultraviolet radiation. Dibutyltin oxide was more effective for transesterification of CBDO with dimethyl terephthalate than other typical catalysts. Better color and higher molecular weights were obtained with this catalyst when the flexible diol was 1,3-propanediol or 1,4-butanediol rather than ethylene glycol.
The thermodynamic properties of isotactic polypropylene in the fully crystalline, glassy, and molten state are established from 0 to 500 K based on data bank heat capacities and the vibrational frequency spectrum. The seven skeletal vibrations are described by θ3 and θ1 of 91 and 714 K for crystalline polypropylene. For the calculation of Cp − Cv, a Lindemann A0 value of 1.5 × 10−3 K mol/J was found. Calculated and experimental heat capacity data show agreement within an average error of −0.3 ± 1.6%. Glassy polypropylene was similarly treated up to the glass transition temperature at 260 K (θ3 = 78 K, θ1 = 633 K, average heat capacity error −0.6 ± 2.8%). The residual 0 K entropy of glassy polypropylene is 1.9 J/K mol. Partially crystalline polypropylene is shown through high‐sensitivity DSC measurements to have a glass transition range from 260 to 380 K. Similarly, high‐sensitivity DSC has been used to characterize the condis phase of polypropylene (conformationally disordered polypropylene) which was prior called “smectic mesophase” or “paracrystalline.” Its heat of transformation to the stable crystal phase is 600 J/mol.
Heat capacity data of semicrystalline poly(oxymethylene) samples. Delrin and Celcon, are analysed in order to discuss the glass transition behaviour of this polymer. There are two types of non‐crystalline poly(oxymetheylene). the mobile and rigid amorphous parts. The glass transition of the former occurs in a rather wider range of temperature: it starts at 180 K and could end at 265 K. The latter, under restraint due to the crystallites, remains frozen up to the melting temperature.
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