Preparation Of Multilayered Polymer Foams And Study On Relationship Between Structures And Properties

Multilayer polymer foam can be prepared by layer-by-layer assembly technologies and batch foaming process.In this paper,two different systems were used and two different methods were studied: multilayered PS/PMMA materials were prepared by hot pressing and spin-coating,and multilayered PS/PMMA foam was prepared by batch foaming method.Multilayered PS/PS & nano-silica material was prepared by multi-layer co-extrusion method,and multilayered PS/PS & nano-silica foam was prepared by the batch foaming method.The unique bi-modal distribution of multi-layer polymer foam is studied.The effects of layer-by-layer preparation conditions and foaming conditions on the cellular structure of foam samples are studied.The regulation of experimental conditions on the structure of foamed samples is realized.The mechanism of the formation of different foams is analyzed,which provides a new idea for preparing high-performance multi-layer polymer foam materials.The results show that it is feasible to use PS/PMMA system and PS/PS & nano silica to prepare multi-layer foams with bi-modal distribution.Moreover,it proves that most polymer/polymer and nanoparticles blends can be used to prepare multilayered polymer foams.Multilayered PS/PMMA foam was prepared by hot pressing,spin coating and batch foaming.It was proved that PS and PMMA had the same foaming windows and different foaming characteristics under the same foaming conditions,and showed different cell structure after foaming.The results show that the blends of PS and PMMA can effectively enhance the interfacial adhesion and compatibilize the incompatible interface of PS/PMMA.What's more,the foaming behavior of PS/PMMA is improved and the foaming window of PS/PMMA is enlarged.The thickness of selected coating can be precisely controlled by spin-coating.The concentration of spin-coating solution and foaming temperature are the main factors affecting the cell structure of multilayered PS/PMMA foam.From 50g/L to 200g/L,the bubble size of PS layer increased continuously while that of PMMA layer remained unchanged.With the increase of foaming temperature,the bubble size of PS layer first increased and then decreased,while that of PMMA layer remained the same.The multilayered PS/PS&Nano-silica foam was prepared by multi-layer coextrusion method and batch foaming method.It was proved that PS/PS&Nano-silica had overlapping foaming windows and different foaming characteristics under the same foaming condition,and showed pore structure after foaming.The results show that PS/PS&Nano-silica does not have an incompatible interface and the viscosity coefficient is almost the same,so the interlaminar structure of the multi-layer polymer composite prepared by multi-layer coextrusion is complete,the thickness of each layer is same,and the number of layers can be superposed.The number of layers,saturation pressure and foaming temperature are the main factors that affect the cellular structure of multilayered PS/PMMA foam.After foaming,with the increase of the number of layers,the cell in the bullous layer disappear over 32 layers.The expansion rate of the foam is very low at the 2 level,increase and then keeps stable at the 4-16 level,and then decreases suddenly after 32 drops.High expansion ratio(up to 30 times)and continuous pore size structure result in excellent insulation performance of multilayered PS/PS&Nano-silica foams.