Differential scanning calorimetry was used to study the crystallization and melting of nylon 610. For nylon 610 crystallized from the melt state (260 degrees C), the overall rate of bulk crystallization can be describ...Differential scanning calorimetry was used to study the crystallization and melting of nylon 610. For nylon 610 crystallized from the melt state (260 degrees C), the overall rate of bulk crystallization can be described by a simple Avrami equation with Avrami exponent n approximate to 2, independent of crystallization temperature. With the experimentally obtained T-m(0) (235 degrees C similar to 255 degrees C) of nylon 610, the fold surface free energy a, was determined to be 35 similar to 38 erg/cm(2). The effects of annealing temperature and time on the melting of quenched nylon 610 were also investigated. For nylon 610 quenched at room temperature there is only one DSC endotherm peak DSC scans on annealed samples exhibited an endotherm peak at approximately 10 degrees C above the annealing temperature. The size and position of the endothermic peak is strongly related to annealing temperature and time. An additional third melting was observed when quenched nylon 610 was annealed at high temperature for a sufficiently long residence time. The existence of the third melting peak suggests that more than one kind of distribution of lamella thickness may occur when quenched nylon 610 is annealed. The implications of these results in terms of crystal thickening mechanism were discussed.展开更多
基金This work is sponsored by The National Natural Science Foundation of China.
文摘Differential scanning calorimetry was used to study the crystallization and melting of nylon 610. For nylon 610 crystallized from the melt state (260 degrees C), the overall rate of bulk crystallization can be described by a simple Avrami equation with Avrami exponent n approximate to 2, independent of crystallization temperature. With the experimentally obtained T-m(0) (235 degrees C similar to 255 degrees C) of nylon 610, the fold surface free energy a, was determined to be 35 similar to 38 erg/cm(2). The effects of annealing temperature and time on the melting of quenched nylon 610 were also investigated. For nylon 610 quenched at room temperature there is only one DSC endotherm peak DSC scans on annealed samples exhibited an endotherm peak at approximately 10 degrees C above the annealing temperature. The size and position of the endothermic peak is strongly related to annealing temperature and time. An additional third melting was observed when quenched nylon 610 was annealed at high temperature for a sufficiently long residence time. The existence of the third melting peak suggests that more than one kind of distribution of lamella thickness may occur when quenched nylon 610 is annealed. The implications of these results in terms of crystal thickening mechanism were discussed.
