The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles.Poly(vinyl chloride...The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles.Poly(vinyl chloride) (PVC) samples were prepared by freeze-extracting the solutions in various solvents and with varying concentrations.The results of FTIR analysis showed that when the concentrations of the solutions were lower than the overlap concentration c*,the PVC samples prepared from the good solvent had more ordered structure due to much fewer interchain entanglements.While the concentrations of the solutions were higher than c*,the PVC samples prepared from the bad solvents had more ordered structure.展开更多
Ultra-high molar mass polyethylene(UHPE) or HDPE was melted at various temperatures or at a constant temperature for various time, and then crystallization from the melt was investigated. The crystallization behavior ...Ultra-high molar mass polyethylene(UHPE) or HDPE was melted at various temperatures or at a constant temperature for various time, and then crystallization from the melt was investigated. The crystallization behavior of UHPE was found to be different from those of HDPE. It was found that the crystallization temperature decreased as the heating time or heating temperature increased. During the melting process, thermal motion of the chains leads to a change of chain conformation from parallel-extended chains to interpenetrated random coils, accompanied by the occurrence of entanglements. As a result, the crystallization temperature shifts to a lower temperature. In addition, the samples of UHPE with less entanglement were prepared by a freeze-drying procedure from dilute solution was proved the effect of entanglements on crystallization behavior of macromolecules. A preliminary study on the crystallization of the samples indicates that entanglements have a pronounced effect on the crystallization behavior of macromolecules.展开更多
文摘The partially disentangled polymer samples prepared are expected to crystallize easier than bulk polymers,which can be attributed to much fewer interchain entanglements within and between particles.Poly(vinyl chloride) (PVC) samples were prepared by freeze-extracting the solutions in various solvents and with varying concentrations.The results of FTIR analysis showed that when the concentrations of the solutions were lower than the overlap concentration c*,the PVC samples prepared from the good solvent had more ordered structure due to much fewer interchain entanglements.While the concentrations of the solutions were higher than c*,the PVC samples prepared from the bad solvents had more ordered structure.
文摘Ultra-high molar mass polyethylene(UHPE) or HDPE was melted at various temperatures or at a constant temperature for various time, and then crystallization from the melt was investigated. The crystallization behavior of UHPE was found to be different from those of HDPE. It was found that the crystallization temperature decreased as the heating time or heating temperature increased. During the melting process, thermal motion of the chains leads to a change of chain conformation from parallel-extended chains to interpenetrated random coils, accompanied by the occurrence of entanglements. As a result, the crystallization temperature shifts to a lower temperature. In addition, the samples of UHPE with less entanglement were prepared by a freeze-drying procedure from dilute solution was proved the effect of entanglements on crystallization behavior of macromolecules. A preliminary study on the crystallization of the samples indicates that entanglements have a pronounced effect on the crystallization behavior of macromolecules.