Study On Extruding Ultrahigh Molecular Polyethylene/Polypropylene Assisted By Ultrasonic/Supercritical CO₂

Processing ultrasonic and supercritical CO₂ were introduced during processing of ultrasonic molecular weight polyethylene(UHMWPE) with a general twin-screw extruder. The mechanism of the conveying,melting,plasticating in the extruder was proposed.The effect of rheology behavior and structure,performance during the extrusion was studied.The difficulty of polymer unmanaged with high-density and macromolecular melt viscosity is solved.And this paper discuss the extrusion processability and mechanical properties of the bending system consisting of ultrahigh molecular weight polyethylene and polypropylene under the action of ultrasonic.Results show that the ultrasonic can improve the processing of UHMWPE/PP through decreasing the die pressure and apparent viscosity.Ultrasonic also can enhance die tempreture and make the appearance quality better.The ultrasonic can reduce crystal dimension and crystallinity.With appropriate dose of ultrasonic treatment,the mechanical properties are improved.The phenomenon of macromolecule degradation occurs in case the ultrasonic intensity is overhigh,thereby the mechanical properties of the UHMWPE/PP blend decrease.DSC and Xrd show that the crystallinity and crystal dimension decreased after the ultrasonic injected.And the SEM show that the ultrasonic can improve toughness of the polymer.The addition of supercritical CO₂ can improve fluidity of polymer melt obviously, increase the flow rate of extension,extend the process range and be useful of macromolecule extrusion.And the mechanical properties results show that the tensile strength and elongation at break is lower what is not effected by supercritical CO₂,but the toughness of UHMWPE/PP blend enhance obviously.And the SEM shows that supercritical CO₂ made the micro morphology in the copolymer,the micro morphology play a role of Stress concentration.At the same time,the dispersibility of polymer and the foam will be better when the ultrasonic is injected.