Dissertation
Dissertation > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Foam > Soft foam

Study on the Preparation and Properties of Polyethylene Blend Foam

Author ZhangWenHua
Tutor ZhaoZuoNian
School Tianjin University of Science and Technology
Course Materials Processing Engineering
Keywords LDPE rubber powder wood flour open-celled foam extrusion foam NaCl
CLC TQ328.1
Type Master's thesis
Year 2011
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By press molding and single screw extruder, the blend foams of LDPE with rubber powder or wood flour were prepared. In this paper, mainly focused on the effect of the amount of exothermic blowing agent AC, heat-absorbing foam agent NaHCO3, rubber powder and wood flour, cross-linking agent, nucleating agent CaCO3, EVA, and pore-forming agent NaCl on the mechanical properties, apparent density, expansion ratio, open porosity and water absorption of blend foam materials, meanwhile, it was also discussed that the influence of single screw head temperature, hot press temperature on the properties of blend foam materials. And the sections of the blend foams were observed by scanning electron microscopy (SEM).The results showed that:In the LDPE/rubber powder blends, adding0.2phr ZnO into1phr AC, the decomposition temperature of AC dropped to181.5℃~186.5℃, which suitable to foam forming. When the AC dosage was lphr, the blend foams forming was better, overall performance were good. The optimum amount of rubber powder was50phr, when the tensile strength, elongation rate were better, and apparent density was lower, open porosity reached the top value. When the amount of crosslinker was0.3phr, the blend foams in physical properties, elastic modulus, open porosity and water absorption were achieved the peak value. By using the extrusion process, when the die temperature of extrusion machine was185℃, the open porosity reached maximum. While using the hot press molding method, the better temperature was around190℃, the blend foams was fine and homogeneous, the bubble connectivity was better, open porosity achieved the best value. As the amount of pore-forming agent NaCl increased, tensile strength, elongation at break decreased, but the water absorption and open porosity rise, when the NaCl dosage was30phr, the overall performance of blend foams were better, foam had higher connectivity.In the LDPE/wood flour blends, with the amount of wood flour increaseing, tensile strength, elongation at break of blend foams decreased, water absorption and open porosity rise. When the amount of wood flour was30phr, the water absorption and open porosity achieved the best value, and the finer particle size of wood flour, the better wood flour compatibility with LDPE, the cell of blend foams was fine and uniform. With the amount of pore-forming agent NaCl increaseing, the tensile strength, elongation at break were decreased, but the water absorption and open porosity enhanced.

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