Study On Environmental Stress Cracking Behavior Of Hdpe Injection Molded Parts

High Density Polyethylene (High Density Polyethylene, short for "HDPE") is a crystalline thermoplastic resin. It is widely used in military, automobile manufacturing, electronic and electrical appliances, cable, pipeline etc. For HDPE, ESCR is a very important performance requirement. Study the ESC behavior of the HDPE injection molded parts,can be to predict and improve the environmental stress cracking resistance of parts provide theoretical guidance and experimental basis, has an important academic significance and application value.This study mainly researches on the environmental stress cracking behavior of HDPE injection molded parts of solvent, around the polymer processing condition-microstructure-ESC behavior relationship, mainly studies Melt temperature, holding pressure, cooling time, injection speed, etc Plastic injection molding process effect on the properties of HDPE products ESCR; The HDPE injection molded parts of ESC behavior under different experimental methods are preliminary discussed; Main work include:1Using bending test method to research the ESC of HDPE injection molded parts of OP-10, obtain the cracking time of the different molding process of HDPE injection molded products, Forming microstructure analysis, studies the influence of processing conditions on product ESCR. By DSC characterization of crystallinity, the preliminary discussion on the relationship between crystallinity and ESCR, Combined with other micro-molding process on the structure of orientation, and analyzes the ESCR of HDPE parts change rule under different molded processing conditions, among them, the longer the cooling time and low pressure stress is conducive to enhance ESCR performance of products. In addition, by observing the sample crack location and shape shows that crack area is located in the middle of specimen. This is because in bending specimen method, sample into180°, specimen deformation near central area has even more than the yield point; Rupture surface smooth, no cold drawn phenomenon that ESC for brittle cracking of HDPE parts, and the sample split between mesh the more, its cracking the longer. 2, Using Solvent immersion method and constant strain four-point bending method research the ESC behavior of HDPE injection molded parts. Found direct immersion in a solvent environment, although organic solvent cyclohexane and surfactant OP-10for HDPE are relatively strong solvent, but there was no cracking in the experimental setting time, this may be due to (i) the residual stress inside the HDPE plastic injection products is small,(ii) HDPE is a semicrystalline material, crystallization area of parts resist the ESC, under lower stress cracking may need time longer, therefore, It also poses challenges for in the laboratory simulation of real use environment to evaluate HDPE ESC behavior; In addition, under the condition of the self-made constant strain four-point bending test, samples did not crack, this is because the HDPE as a flexible material of high modulus, it needed for the ESC strain is larger, the sample shape variables would not be enough to reach the critical strain of ESC.