Takarada Wataru, Barique Mohammad A, Kunimitsu Tatsuma, Kameda Takao, Kikutani Takeshi
Department of Materials Science and Engineering, Tokyo Institute of Technology, Tokyo 152-8550, Japan.
Futuristic Technology Department, SANKO GOSEI Ltd., Toyama 939-1852, Japan.
Polymers (Basel). 2022 Aug 9;14(16):3238. doi: 10.3390/polym14163238.
A 'model' material of recycled polypropylene (PP) was prepared through the injection molding process, and the effect of processing history on the polymer characteristics was investigated through the high-speed melt spinning of virgin and recycled PP. On-line measurement of the thinning behavior of the spin-line revealed the downstream shift of solidification point for the recycled PP at the take-up velocity of 1.0 km/min, indicating the suppression of flow-induced crystallization. The difference was not clear at higher take-up velocities of up to 5 km/min. For any identical take-up velocity, no clear difference in the stress-strain curves and birefringence of the fibers from virgin and recycled PP could be observed, whereas the detailed investigation on the variation of relative amount of -axis and a*-axis oriented crystals in the fibers prepared at varied take-up velocities suggested the deterioration of flow-induced crystallization at 1.0 km/min. It was speculated that the processing history induced the lowering of the entanglement density, which affected the melt spinning and crystallization behavior. An undistinguishable difference between the virgin and recycled PP at increased take-up velocities suggested the existence of an optimum elongational strain rate for the detection of the different states of molecular entanglement.
通过注塑工艺制备了一种回收聚丙烯（PP）的“模型”材料，并通过对原始PP和回收PP进行高速熔体纺丝，研究了加工历史对聚合物特性的影响。对纺丝线细颈化行为的在线测量表明，在卷取速度为1.0 km/min时，回收PP的凝固点向下游移动，这表明流动诱导结晶受到抑制。在高达5 km/min的较高卷取速度下，这种差异并不明显。对于任何相同的卷取速度，原始PP和回收PP纤维的应力-应变曲线和双折射均未观察到明显差异，而对不同卷取速度下制备的纤维中β轴和a*轴取向晶体相对含量变化的详细研究表明，在1.0 km/min时流动诱导结晶恶化。据推测，加工历史导致缠结密度降低，从而影响熔体纺丝和结晶行为。在增加卷取速度时，原始PP和回收PP之间无法区分的差异表明，存在一个用于检测分子缠结不同状态的最佳拉伸应变速率。
