Studies On Preparation And Performance Of SEPS And ABS Based Foam Materials

With the development of science and technology,non-renewable energy sources such as petroleum are becoming increasingly scarce,and material lightweight is becoming increasingly important.Among them,microcellular foam materials have rapidly developed due to their unique cellular structure and excellent performance.The autoclave foaming method due to the characteristics of green environmental protection and high production efficiency,which had widely used in the preparation of microcellular foaming materials.Hydro-styrene-isoprene styrene（SEPS）and acrylonitrile-butadiene-styrene terpolymer（ABS）are widely used because of their excellent properties.Therefore,this paper mainly blends and modifies SEPS and ABS respectively,and uses autoclave foaming process to prepare microcellular SEPS and ABS based foam beads.After steam pressure molding,foam boards are further prepared.The tensile,compression and thermal conductivity properties are investigated to provide a theoretical basis for practical applications.It is expected to be applied in fields such as sole material and transportation.The detail researches of this thesis as follows:（1）In the process of preparing SEPS foam material,the rise of temperature caused its melt to break and can not wrap CO₂ gas,resulting its poor foaming behavior.However,polypropylene（PP）with high melt strength was successful application in microcellular foam materials because of its low price and good performance.In this subject,PP was used as the melt reinforcement material to prepare SEPS/PP composites by melt blending method.The SEPS/PP foam beads and foam boards are respectively,with CO₂ as the physical foaming agent,steam as the heating medium,using autoclave foaming process and steam pressure molding technology.The influence of the PP content on the properties of the composite and the influence of foaming process conditions on the foaming behavior of SEPS/PP were investigated.The melt flow rate,mechanical properties,crystallization behavior,phase morphology distribution and cell morphology of SEPS/PP composite materials were characterized and tested.When the PP content is 5 wt%,the cell size of the prepared SEPS/PP foam beads is 104μm,the expansion ratio is 6.7 and the cell density is 8.4×10⁶ cells/cm³ with uniform morphology.By changing the foaming temperature,saturation pressure,and saturation time,the SEPS/PP foam beads can be adjusted within the range of cell size of 61-131μm,the expansion ratio of 3.7-10 and the cell density of 7.6×10⁵-3.9×10⁷ cells/cm³.When the steam pressure is 2.0 bar and the expansion ratio is 10,the highest tensile strength and elongation at break of foam board can reach 715 k Pa and 63%,respectively,and the lowest thermal conductivity is 0.038 W/（m·k）.When the expansion ratio is 7,the highest recovery rate of foam board can reach 88%,that meet the use of cushion and other fields.（2）In the process of preparing ABS foam materials,it is difficult to prepare high-performance ABS foam materials.ABS as a random copolymer has the fast gas escape speed,although its melt strength is high.Three different types of heterogeneous nucleating agents,silica（Si O₂）,talc（Talc）,and polytetrafluoroethylene（PTFE）,were selected to prepare ABS based composites and foam beads using melt blending and autoclave foaming techniques.The effects of heterogeneous nucleating agent types on the melt flow rate,mechanical properties,and foaming behavior of ABS were studied.The results show that PTFE has the best foaming effect among heterogeneous nucleating agents,which can prepare foam beads with a size of 72μm,expansion ratio of 17 and the cell density of 7.1×10⁷ cells/cm³.When the amount of PTFE was 0.1 wt%,ABS/PTFE foam beads with uniform cell morphology can be prepared.By controlling the foaming temperature,saturation pressure and saturation time,ABS/PTFE foam beads can be adjustable within the range of cell size of 35-100μm,expansion ratio of 5-25 and cell density of 1.0×10⁷-3.0×10⁸ cells/cm³.When the expansion ratio was 10 and the steam pressure was 0.8 bar,the maximum tensile strength of foam sheet can reach 401 k Pa,the maximum compression elastic modulus and 85%compression strength are 58 MPa and 50 MPa respectively,and the minimum thermal conductivity can reach 0.0518 W/（m·k）,which was expected to be used in transportation and other fields.