Research On The Formation Mechanism Of β-Crystalin Ippfiber During Melting-Recrystallizing Process

This paper work goes through introducing iPP fiber into amorphous HIPSmatrix to obtain iPP fiber/HIPS matrix composite. Polarizing microscope,scanning electron microscope, Fourier transform infrared spectroscopy anddifferential scanning calorimetry were applied to research the influence ofdifferent temperature and time to partial melting of iPP fiber and molecularchain orientation during melting process, and the crystal morphology structurereceived by recrystallization. And the main results are as follows.1. POM results shows that at the same melting time, with introducingtemperature increasing, the content of β-crystal increased first and thendecreased slightly. While at the same introducing temperature, the content ofβ-crystal appeared the similar change rules. This means, molten iPP fiberintroducing the formation of β-crystal was related to the molten degree of fiber,also was related to molecular chain orientation of iPP fiber, but only a certaindegree of molecular chain orientation was able to induce the growth ofβ-crystal. The experiment of melting samples containing β-crystal obtained bymelting and recrystallizing futher proved that the β-crystal induced by fiber melting was different from that of shear induction sample which β point nucleiwas induced by α row nuclei. There would be large continues β-crystal regionas long as the orientation is suitable.2. FTIR spectra research indicated that with melting time increasing,840cm-1band orientation factor of iPP fiber decreased evidently,973cm-1bandorientation factor decreased slightly and1153cm-1band orientation factorincreased first and decreased later. This means that along with melting timerising, crystal phase oriented degree of iPP fiber declined sharply, partialordered structure in amorphous phase increased at the very beginning and laterdecreased while average oriented degree of molecular chain reduced. DSCprofiles showed that when melting to172oC, crystallization peak firstappeared in cooling process, and when melting temperature researched181oC,β-crystal first turned up in the corresponding cooling process. Thecrystallization peaks shifted to lower temperature region with meltingtemperature rising. And that’s because there was still large amount of partialordered structure in fibers at lower temperature which led to crystallization athigher temperature. And with melting temperature rising, molecular chainactivity increased and gradually approached to total disorder melt that causedcrystallization shifting to lower temperature region.