Microcellular Foaming Of Liquid-Induced Crystallized PC Sheets And Their Properties

Crystal polycarbonate (PC) film was successfully prepared by employing acetone to induced PC crystallization. Based on the principle of liquid induced crystallization, the morphology, structure and properties of crystals were investigated. The mechanisms of liquid induced crystallization were explained.The microcellular foaming of crystal PC sheets were prepared using azodicarbonamide (AC) as foaming agent and crystal PC sheet as foaming material by compression moulding. The effects of processing parameters on the cell structure and mechanical properties of foaming crystal PC sheets were investigated.FTIR spectrum confirmed that the acetone induced crystallization have no effects on the structure of PC sheets, and the small peak shift was found at1289,1308and1460cm"1. The morphology and structure of crystal PC sheet were studied by optical microscope, Scanning Electron Microscope (SEM) and Wide Angle x-ray Diffraction (WAXD) respectively. The results showed that the crystal prepared by liquid induced crystallization was spherulite. The crystal size was calculated by the position of diffraction peak at2θ=17.1°, which located in the face of (020),(201). Dynamic mechanics viscoelastic spectrum analyzer (DMA) was employed to discuss the glass transition temperature, which helped explaining the mechanism of acetone induced crystallization. The glass transition temperature was decreased by32℃, and the peak of tand decreased as well. Mechanical test of the crystal PC sheets showed that the mechanical properties of crystal PC sheet were influenced by plasticization as well as crystallization. The tensile strength of crystal PC sheets increased with the extending of crystallization time before reaching a balance after60min.The cell structure and mechanical properties of crystal PC sheets were investigated, And the results showed that the size of cell decreased with the increase of saturated pressure, crystallization time and blowing agent content, while increased with the increase of foaming temperature; The cell density increased with the increase of saturated pressure, crystallization time and blowing agent content, and increased firstly and then decreased with the increase of foaming temperature; Tensile strength and tensile modulus both increased with the increase of crystallization time, while decreased with the increase of saturated pressure and foaming temperature.