Papers by Keyword: Moulding Process

Abstract: Foaming moulding process, cellular structure and dielectric property of polyimide (PI) foam which has been prepared by esterification method were discussed. Research results showed that the cell of prepared PI foam was well-distributed and its pore volume and porosity were bigger by microwave heating when methanol was used as the foaming agent and its content in the polyester ammonium salt (PEAS) precursor powder was 13-15%; meanwhile, the dielectric constant and loss factor of PI foam were lower.

Abstract: The effect of molding temperature, pressure, packing time and cooling methods on the properties of ramie roving reinforced polypropylene composites was mainly investigated in this paper. We used moulding process to prepare the ramie fiber/PP (Polypropylene) composites with the ramie roving as the reinforcement which were loosed into a single fiber state in the case of without affecting the fiber’s longitudinal straightness, and then investigated the influence of processing conditions to the mechanical properties of composites. With the DSC (Differential Scanning Calorimetry), the effect of cooling conditions on the crystallization of composites was also discussed. The result shows that taking ramie roving as the reinforcement will improve the infiltration properties of the PP matrix to ramie fibers, the reason is that ramie fibers have good orientation and it is loosely arranged in the ramie roving , all of these are benefit to form a good interfacial bonding between fibre and PP resin. Different processing conditions have great impact on the mechanical properties of composites. And the samples gained the best merchanical properties when the process conditions such as molding temperature, pressure, packing time are selected as 165°C, 8MPa, 10min. When the composites cooled together with the heating plate, its melting enthalpy is the highest and the crystallization properties is better than other cooling methods such as home temperature cooling and quickly water-cooling, and its tensile properties is the best.