Microstructure, Mechanical Properties And Heat Transfer On The Moulding Of PP Tape

Cooling condition has a crucial role on the polypropylene (PP) film tape molding, should never be ignored. The variation of cooling temperatures result in the different thermal history progress on the procession of PP tapes, induce different microstructures, which affect the tensile properties of PP tapes.In this paper, an attempt, to formulate a new approach to the modeling of the temperature profile in the precursor cooling stage and the tape heating stage of the molding of the PP tape, was carried out. And it laid the groundwork for analysing the physics changes of PP tape during molding, optimizing the process conditions and making uniform PP tape manufactures. The crystallization, orientation and morphology of PP precursor and tape were investigated by wide angle X-ray diffraction (WAXD), different scanning calorimetry (DSC), fourier transform infrared (FTIR) and scanning electron microscopy (SEM). And their mechanical properties were also studied using tensile test.The mathematical simulation for heat tansfer processing during PP tape molding was performed through solution in C language program. The resulted showed that water bath temperature and the available heating temperature increased with the water cooling temperature, when the water cooling flow rate was ignored. So if the water bath temperature and the available heating temperature are controlled in a narrow fluctuating range, the water cooling flow rate should be more precise regulated with the change of the water cooling temperature.The tests of WAXD, DSC, FTIR, SEM and tensile showed that the crystallinity degree, microcrystal width, tensile strength, Young modulus and elongation at break of samples (precursor and tape) increase with the water bath temperature. But the orientation of samples decreased with the water bath temperature. If the water bath temperature fluctuate within a more wide range, the crystallinity degree, Herman orientation function, tensile strength, Young modulus and elongation at break of samples will have higher fluctuation deviation.These tests also showed that the crystallinity degree, the orientation functions of amorphous and crystalline increase significantly for PP tapes subjected to heat drawing. During the heat drawing stage of PP tape molding, the crystal not parallel to the tensile direction (111 and 041 crystalline planes) defonned and slipt along the tensile direction until all of them disappeared, and the crystal parallel to the tensile direction (110,040 and 130 crystalline planes) increased.