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Study on NR/LLDPE Thermoplastic Elastomer Foams

Author: WangChao
Tutor: LiZhiJun
School: Hainan University
Course: Materials Science
Keywords: thermoplastic elastomer azodicarbonamide macthing of the rate of vulcanization with that of foaming foams structure and properties
CLC: TB383.4
Type: Master's thesis
Year: 2011
Downloads: 67
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Abstract


In this paper, the dynamic and thermodynamic decomposition characters of NaHCO3 and AC blowing agent were studied by differential scanning calorimetry （DSC） and gas evolution test device made by self, and suitable foaming agent was selected. Suitable foaming compound system for NR/LLDPE thermoplastic elastmoer foam was choosed by the research of the influence of different foaming additives and usage on the dynamic and thermodynamic decomposition characters of AC foaming agent. The effect of AC foaming agent、ZnCO3 and AC/ZnCO3 compound system on the vulcanizing properties of thermoplastic elastomer were studied by vulcameter.Under similar analytical conditions （same composition and temperature）,the vulcanization properties and dynamic decomposition characters were determined by vulcameter and gas evolution test device, on the basis of that and the thermosplastic elastomer foaming material’s mechanical properties and microscopic shape structure, the matching of the rate of vulcanization and foaming was Investigated. Using the orthogonal experimental technique, we studied the molding foaming process（molding time、temperature、pressure） of the whole system. On the basis of this, the influence of different molding pressure and different usage of AC、ZnCO3 and Sulphur on the relative density and mechanical properties were studied, and the microscopic shape structure was characterized by fluorescence microscope.NR/LLDPE thermoplastic elastomer foams were prepared by means of chemical cross-linking and one-step compression molding in this paper. The result showed that, compared with NaHCO3, AC foaming agent showed higher decomposition temperature and stronger sudden, but higher gas evolution. The temperature and sudden of decomposition would be lowered when it was compound with suitable active agent. That would match with the molding process. The temperature and bursty of the main reaction of AC decomposition would be lowered down when AC/ZnCO3 compound foaming system in use. The system mentioned above also showed other characters such as lower usage of ZnCO3、no pollution to light colour products and so on. Under the influence of molding process、blending ratio of NR/LLDPE、dosage of sulfur and blending ratio of AC/ZnCO3,the matching of the rate of vulcanization and foaming did more influence to the relative density、the properties and microstructure. under the compression molding process （temperature、pressure and time） of 165℃、1Mpa and 14minutes, the low relative density, good rebound resilience and comprehensive mechanical properties of NR/LLDPE foams were obtained when blending ratio of NR/LLDPE was 70/30, dosage of sulfur was 1.5 phr, compound ratio of AC/ZnCO3 was 10/8. In this case, the matching of the rate of vulcanization that of foaming showed better, and the foams had uniform cellular structure and were mainly made up of closed-cells.

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