Study On Structure And Properties Of Polymer By In-situ Tensile Technology

In recent years, to make polymers self-reinforce by the polymer morphology controltechnology has become a hot research topic. In-situ tensile reinforcement technology isthat shish-kebab structure orderly or fiber structure as the reinforcing phase formed insidepolymers of processing，Then mechanical properties are improved, and it reaches effect ofstrength. In this paper, self-designed situ fiber-reinforced polymer sheet is prepared inconvergence divergence extrusion which installs in the torque rheometer. in the experiment,we makes a research on the structure and properties of high density polyethylene (HDPE)，polypropylene (PP), the liquid crystal reinforced polypropylene (PP/LCP),PP/LCP/PP-g-MAH, The performance of materials is strengthened.The mechanical properties and heat resistance of polymer near-melting extrusionmolding sheet have been markedly improved. The tensile strength of HDPE and PP sheetare increased by47.49%and20.46%respectively. Lamellar structure having a reinforcingeffect and orderly arrangement in the direction of melt flow is generated in thenear-melting extrusion sheet. In addition, the near-melting extrusion sheet melting peakdrift to the high temperature, which improves the crystallinity degree, smaller thecrystallite size, and refines the crystal grains.Extrusion temperature and draw ratio are two important factors that affect the polymermaterial in situ fiber self-reinforced. As the extrusion temperature decreases, the spherulitein the PP sheet gets smaller and occurs plastic deformation. Then mechanical properties areimproved. In the extrusion molding temperature of160°C, the maximum tensile strengthof the PP sheet is34.39MPa, and the temperature of the Vicat softening point is101.5°C.larger draw ratio forming polymer sheet has better performances. Comparing with thepolymer sheet under the draw ratio is2, the tensile strength of HDPE and PP sheet areincreased by56.44%and46.65%, and the temperature of the Vicat softening point isimproved by19.8°C and15.4°C respectively, when the draw ratio is11. Moreover, whenthe draw ratio is2, the crystal structure of the polymer sheet is spherulite. Draw ratio is11,the spherulite in the PP sheet gets smaller, and the macromolecular chain of HDPE sheethas has a higher degree of orientation at the melt flow direction, and forms the lamellarstructure.By adding10parts of a liquid crystal polymer, the PP/LCP composite hold the best mechanical properties. Compared with pure PP, the flow properties, tensile strength andVicat softening temperature of the PP/LCP (100/10) composite material are increased by25.72%,25.22%and21.1°C. With the LCP added,"fibers" having a reinforcing effect areformed in the PP matrix. In addition, with the smaller crystallite size, the grains get refined.After adding LCP, the melting peak of the PP beta crystal form disappears. The fracturecharacteristic of the PP/LCP composite has changed from ductile fracture to brittle fracture.PP-g-MAH has bad modification effect on the PP/LCP composite. With the addition ofPP-g-MAH, the flow and tensile properties of the PP/LCP/PP-g-MAH composite materialare declined rapidly. It has little effect on the heat resistance. Also, PP-g-MAH makes thefiber-forming ability of the PP/LCP composite system decreased.