Effects of annealing on the hierarchical crystalline structures and mechanical properties of injection‐molded bars of high‐density polyethylene |
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Authors: | Long Wang Quan‐Ping Zhang Jia‐Hui Wang Bin Yang Ming‐Bo Yang Jian‐Ming Feng |
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Affiliation: | 1. College of Polymer Science and Engineering, and State Key Laboratory of Polymer Materials Engineering, Sichuan University, , Chengdu, 610065 PR China;2. College of Chemistry and Chemical Engineering, and Key Laboratory of Environment Friendly Polymeric Materials of Anhui Province, Anhui University, , Hefei, 230601 PR China |
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Abstract: | The effect of annealing on the microstructural evolution and mechanical properties of high‐density polyethylene parts molded via gas‐assisted injection molding was investigated using scanning electron microscopy, differential scanning calorimetry, two‐dimensional wide‐angle X‐ray diffraction and tensile testing. The results indicated that a variety of annealing temperatures could induce considerable variations in the hierarchical structures, crystallinity, lamellar thickness and yield stress of the molded bars. According to these results, the annealing temperatures could be divided into three regions. In the low‐temperature region of annealing at 80 °C, the spatial variation of the superstructure developed along the thickness direction and mechanical properties of the annealed sample were mainly unchanged and similar to those of the original specimen. At 100 and 120 °C, the intermediate temperature region of annealing, the thickness of the crystals, degree of orientation and yield stress of annealed samples were greatly improved. Finally, at 127 °C, the degree of orientation decreased and yield stress slightly improved, an indication of the high‐temperature annealing region being characterized by increasing melting/recrystallization and causing relaxation of oriented molecular chains. A model is proposed to interpret the mechanism of the annealing treatment of the samples at various temperatures. © 2013 Society of Chemical Industry |
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Keywords: | annealing hierarchical structures mechanical properties high‐density polyethylene |
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