Study On The Injection Moulding Of Polyethylene Single Polymer Composites

Single polymer composites (SPCs) overcome the disadvantages of traditionalthermoplastic composites. Compared with the traditional composites, SPCs have lowerdensity, better interfacial bonding and easier recyclability. Polyethylene (PE) SPCs wereprepared by injection moulding technology. Low density polyethylene (LDPE) andultra-high molecular weight polyethylene (UHMWPE) fiber were selected as the matrix andreinforcement respectively. The mechanical properties of PE SPCs were significantlyhigher than those of pure PE products.The effect of different process conditions on the crystallization structure of fiber/matrix interface was compared. The transcrystalline was found when the temperature was125℃or135℃. It was unfavorable to generate transcrystalline when the temperature washigher than135℃or lower than125℃. Besides, it was found that the shearing wasconducive to the formation of transcrystalline. Two filaments were introduced to the matrixfilm statically, the transcrystalline appeared in the interface between one fiber and matrix,but did not appear in the other interface.PE SPCs were prepared by injection moulding technology. The bend strength andimpact strength of PE SPCs could reach12.66MPa and94.83kJ/m2, which correspond to38.21%and63.95%improvement respectively compared to those of nonreinforced PEproducts under the same conditions. The impact of injection temperature, injection pressure,injection time and holding time on the bend strength and impact strength of PE SPCs weredifferent.The injection moulding processes were simulated by Moldflow. The effect of differentprocess conditions on the volume shrinkage and buckling deformation of products werestudied. Besides, distributions of temperature in the cavity were obtained. The resultsshowed that, with the rise of injection temperature, both of the volume shrinkage andbuckling deformation of products increased gradually. With the extension of injection time,the volume shrinkage decreased and the buckling deformation increased. With theextension of holding time, the volume shrinkage decreased first and then kept constant, thebuckling deformation kept decreasing. The temperature of the location farther from thecavity wall was higher. The temperature of the melt in the cavity center was little higherthan the injection temperature.