Preparation And Properties Of Propylene/1-Butylene Copolymer Foaming Materials

In this thesis,the preparation and the properties of the propylene/1-butene copolymer?PPB?were studied.The PPB foaming materials were successfully prepared by the batch foaming process using supercritical CO₂ fluid as a physical foaming agent.The effects of the material's physical properties and processing conditions on foam's cell structure and foaming properties were investigated.And the foam's feasibility of being used as a buffer energy absorbing material was also been studied.As an energy buffer energy absorbing material,the PPB foam has poor repeated compression performance.And in order to enhance this property,the EPDM was introduced into the PPB foam as a plastic phase to form thermoplastic vulcanizate?TPV?by irradiation crosslinking.The influence of EPDM content and irradiation dose on the properties of these materials were studied.Finally,a SiO₂ aerogel/PPB composite foam was prepared to investigate the hydrophobic property of the cutting section surface,also the functional application of these foams was discussed.Comparing the PPB with different 1-butene content,the high content materials have high impact strength,toughness and lower thermal properties.However,the lower thermal properties have benefits on foaming,like lower melting point,smaller crystallinity and wider melting temperature range.The increasing of saturation temperature and pressure during foaming can enlarge the cell size and increase expansion ratio.When the temperature shortly exceeds,the expansion ratio continues to increase and shrinkage occurs.The high temperature can also lower the melt strength,once the melt strength cannot hold the cells in position,the expansion ratio will decrease and the shape of the foam cannot be controlled.PPB foam can be used as a buffer energy absorbing material in anti-collision packaging,and its energy absorption effect is related to the density and 1-butene content of PPB.The low density,high 1-butene content PPB foam has better energy absorption capacity and lower allowable stress,whereas,the high density,low 1-butene content PPB foam has lower energy absorption capacity and higher allowable stress.Therefore,as a buffer energy absorbing material,the density and1-butene content of PPB need to be amended according to the using conditions.PPB and EPDM were blended to prepare a TPV material by radiation crosslinking.The highly crosslinked EPDM provides the TPV's resilience as rubber phase.Whereas,the less crosslinked PPB provides the TPV's tensile properties and multiple-processing performance as plastic phase.The TPV foams were prepared using these TPVs.And it was found that the higher PPB content in the TPV leads to the larger the cell size and higher the expansion ratio during foaming,and the greater the energy loss during compressing.Proper cross-linking can increase the cell size and expansion ratio of the foam by enhancing the melt strength of the TPV during foaming.However,excessive cross-link increases the resistance of the cell growth and reduces the cell size and expansion ratio.The higher EPDM content in the TPV leads to the less change in hysteresis loss during compressing.Therefore,in the composition system of the TPV foaming material,the PPB component provides foaming properties and energy absorption properties during preparation?good buffering energy absorption effect?,and the crosslinked EPDM component provides good resilience and resistant to repeated compression properties?reliability as a cushioning material?.The TPV foaming material can be used as a cushioning packaging material for repeated compression resistance,and the blending ratio of the rubber and plastic can be amended according to the requirements of the buffering capacity and the durability of the material.A kind of composite foam was prepared by microcellular foaming method with PPB and SiO₂ aerogel mixture.A special structure can be obtained on foam's cutting section surface and can be used as hydrophobic material.The SiO₂ aerogel component can increases micron-scale and nanoscale roughness of foam's cutting section surface simultaneously by reducing the cell size and increasing the number of nanoparticle structure on cell walls.As the SiO₂ aerogel content increases,the hydrophobic properties of the cutting section surface increase significantly.However,when the SiO₂ aerogel content exceeds 40 phr,the material can hardly form foams,and the hydrophobic property disappeared as the micron-scale roughness structure cannot be obtained on the cutting section surface.In addition,the increasing of SiO₂ aerogel content can reduce the composite's heat sensitivity.Which improves the composite's thermal stability and expands the application temperature range of the final product.The material can improve the durability of the hydrophobic surface.Although the hydrophobic property of the hydrophobic surface also decreases with usage time,a new hydrophobic surface can be obtained easily by cutting off the old surface.Comparing with the self-peeling hydrophobic coatings,the hydrophobic surface of this material can be renewed several times by cutting of old surface.Hence,the material has better repeatability.