Biodegradable poly(butylene terephthalate/succinate/adipate) (PBTSA) pellet, an ideal random copolymer characterized by 1H solution NMR, was melt-spun into fibers. The crystal structure and physical properties of the as-spun fibers were investigated by WAXD, solid-state 13C NMR, DSC and tensile test measurements. Only poly(butylene terephthalate) (PBT)-like diffraction pattern was observed in WAXD; however, two different 13C spin-lattice relaxation time (T1C) components were observed for aliphatic units, in which the longer and the shorter T1C components correspond to the crystalline and the amorphous domains, respectively. Therefore the crystal structure of PBTSA was concluded to be formed by mixed crystallization of its comonomers. Such crystallization behavior enabled the PBTSA fibers to have well developed PBT-like crystal structure despite of its ideal randomness. Furthermore, due to the introduction of soft segments (BA and BS) into BT crystal lattice, melting temperature of PBTSA fibers (115 °C) was over 100 °C lower than that of PBT. 相似文献
PBS is partially crosslinked by using DCP as an initiator. A low gel fraction (<30 wt%) and low crosslink density of the partially crosslinked PBS are obtained at a DCP content of <0.5 wt%. Consequently, the partially crosslinked PBS retains both its processability and its crystallinity. The overall crystallization rate of the PBS is enhanced by partial crosslinking as evidenced by a considerable increase in crystallization temperature (Tc). Meanwhile, the mechanical properties of PBS are significantly improved by the partial crosslinking. The structure/property relationships of the partially crosslinked PBS are explored.
A synergistic effect of simultaneous plasticization and destructurization of soy protein in melt extrusion is studied using soy meal, glycerol, and urea. The combined effect of plasticization and destructurization yields thermoplastic soy meal (TSM) that is capable of chemical interactions with biodegradable polyesters. Melt‐compounded blends of TSM with biodegradable polyesters give new ductile bioplastics. The observed improvement in the properties of these blends might be due to two reason; the high elasticity of the destructured soy meal and the compatibility between the polyesters used. The synergistic effect of unfolding and destructurization of the protein by urea leads to high mobility in the protein chains of the soy meal.
The spherulitic morphology and growth, overall isothermal crystallization kinetics and hydrophilicity of PBSU were investigated by POM, DSC and WCA measurements in its miscible blends with PEO. The Hoffman‐Lauritzen equation was employed to analyze the spherulitic growth rates of neat and blended PBSU, which show a crystallization regime transition between regime II and III. The overall crystallization rates of PBSU decreased with increasing crystallization temperature, regardless of blend composition, while the crystallization mechanism does not change. A significant improvement in the hydrophilicity of PBSU can be achieved by blending with different weight fractions of PEO, which may be essential for the practical application of PBSU/PEO blends.
The fractional crystallization kinetics and phase behavior of PEO with different molecular weights (MWs) in its miscible crystalline/crystalline blends with PBS are studied. Both fractional crystallization kinetics and phase segregation of PEO in PBS/PEO blends are dramatically influenced by its MW. PEO with a medium MW (20 kDa) shows a significant fractional crystallization in the blends with PBS crystallized at a high TIC,PBS, which, however, is dramatically depressed in the blends with a very low or high MW of PEO. This indicates that the PEO component with a medium MW is more ready to segregate into the interlamellar region of PBS crystals than those with a very low or high MW. The MW‐dependent fractional crystallization kinetics and phase segregation of PEO component in the PBS/PEO blends are discussed.
The effects of crystallization temperature of PBS (TIC,PBS) on the fractional crystallization, phase segregation, and crystalline morphology of PEO in their miscible crystalline/crystalline blends are investigated. The crystallization kinetics and phase segregation of PEO are considerably influenced by TIC,PBS. A higher TIC,PBS results in the crystallization of PEO at an extremely large degree of supercooling and may facilitate the segregation of PEO within the interlamellar regions of PBS. At a high TIC,PBS (e.g., 95 °C), the long period, thickness of amorphous and crystalline layers of PBS increase upon blending with PEO. The TIC,PBS dependence of phase segregation of the PEO component is discussed from a thermodynamic as well as a kinetic perspective.
