Formulation and Production Technology of Modified Low Density Polyethylene Foamed Materials

Formulation and Production Technology of Modified Low Density Polyethylene Foamed Materials Li Xuefeng, Peng Shaoxian 1, Wang Niina, Cao Huihui, Wu Hua 2 (1. Department of Chemical Engineering, Hu 4 North Engineering College, Wuhan 430068, China; 2. Shanghai No. 6 Plastics Factory, Shanghai 200200) 3 (/ 80) At 170*C moulding time 15 minutes, the impact resilience of the foam reached 22 2%, while the permanent deformation (202%) of the cells had a uniform cell size and good performance.

Chinese Library Classification No.: TQ325.12; TQ328: B 1 Introduction LDPE foam plastics have excellent physical, chemical and mechanical properties. Its toughness, good flexibility, wear resistance, excellent electrical insulation, heat insulation and chemical resistance are widely used in many fields such as packaging, chemical engineering, and construction. One of the improvement directions of LDPE is to develop grades of closed-cell foams that are soft, high in flexibility, uniform in cell density, and compact in size. At the same time, flame retardant plastic materials in various fields also require corresponding requirements. Halogen-free and low-smoke will be plastics. The development trend of flame retardant, in which hydrated aluminum hydroxide (ATH) is filled with flame retardant, has attracted widespread attention. In this paper, ethylene vinyl acetate (EVA) was used to modify LDPE, and ATH was selected and then foamed. The effects of components and process conditions on the properties of foams were mainly discussed.

2 Experimental 2.1 Production of raw materials Stearic acid (SA) Zinc oxide (ZnO) are commercially available industrial products.

2.2 Sample preparation 110C) After melting, add appropriate proportion of EVA (EPDM) and mix (5 min), then add DCP (1 part (3 parts), SA (1.5 parts)) and mix the parts (10 min). The pellets were added to a preheated mold, pressurized to 8 MPa at 170C on a plate vulcanizing press, and maintained at a pressure of 15 minutes to allow pressure foaming.

Evenly, add different amounts of ATH and other additives, mix the pieces, mold foaming.

2.3 Instruments and equipment Yongchun Light Industry Machinery Factory QLB-350X350X2 flat vulcanizer Wuxi First Rubber Machinery Equipment Factory XL-100A tensile testing machine Guangzhou Experimental Instrument Factory XS *B1 laboratory optical microscope Jiangnan Optical Instrument Factory LX accurate on the analytical balance The weight of the filter paper was weighed. The sample was cut into small strips of 5 mm in width and 1 mm in width. The strips were wrapped in filter paper. W2 was weighed in xylene as a solvent and placed in a three-necked flask. The mixture was boiled under reflux for 20 h and baked in a vacuum oven at 80C for 6 h. Weigh out W3 and calculate the gel rate as shown below. Of course, if the pressure is too low, the gas generated by the decomposition of AC will have a large diffusion coefficient in the melt and a small solubility, which will cause a large amount of gas to escape. Therefore, in the experiments in this paper, we use the molding temperature 170C pressure 8MPa pressure maintenance 15min process conditions for formula system research.

3.2 Influence of EVA modifiers on the performance of foams LDPE foams, which have good processing properties with LDPE, are less sensitive to changes in viscosity in the processing temperature range than LDPE, making them homogeneous over a wide temperature range. The preferred viscosity state suitable for foaming forms a stable cell structure. Experiments show that the NR modified LDPE can see from the middle, the impact of the foam rebound rate with the EVA content gradually increased at the beginning of the increase, to reach the maximum value of 30 parts of EVA, and then gradually decreased; permanent compression The deformation showed a similar pattern of variation, with a minimum at 30 parts of EVA. LDPE/EVAdOO/O) foaming material has good comprehensive performance. From the change trend of the gelation rate, it can be seen that the foam has a higher gel fraction when the EVA content is 30 parts. In the blending modification system, LDPE and EVA both undergo cross-linking reactions. As the content of EVA increases, the degree of cross-linking gradually increases to a maximum value. The introduction of excessive amounts of EVA consumes a large amount of cross-linked foamed cells. Yes, but the color of the foam becomes darker. The LDPE/BR system is unstable in foaming, and can easily form large bubbles with unequal cell structure and communication, which deteriorates the quality of the foam. The foams of EVA and EPDM modified LDPE have a uniform, fine and smooth appearance and are good modifiers for LDPE foams. , EVA and EPDM content on the modified LPDE density and tear strength, LDPE/EVA showed greater foaming times, higher tear strength; At the same time, LDPE/EVA has a strong intermolecular force This foaming material is more suitable for bonding in the application.

With the gradual increase of the content of EVA, the apparent density of the foam gradually increases, which in turn reduces the degree of crosslinking of the system. The main factors influencing the performance of foam plastics are the cell structure, including the open or closed cells of the foam, the size of the cells and the degree of densification of the cells. Liu Ying, Wu Daming, Long Wenbao et al. Chemical Crosslinked Polyethylene Gel Ratio and Its Measurement of Bubbles . Plastics Industry, 1990 (1), 19