Research On Preparation And Performance Of Polyarylene Ether Nitrile Microcellular Foams

Polymer foam materials play an important role in the lightweight and functional aspects of today’s equipment manufacturing.At present,most of the plastic foam products researched and industrialized are still concentrated on general plastics.The general foam material foam obtained based on the traditional foaming method has a large cell size,which results in a substantial decrease in the mechanical strength,toughness and fatigue resistance of the product,and it is difficult to meet the demand for use under harsh conditions.Therefore,the application of high-performance plastic foams such as high impact resistance,high temperature resistance,low moisture absorption,corrosion resistance and radiation resistance will become the future research and development trend.Special engineering plastics have attracted people’s attention due to their excellent high temperature resistance,high strength,high modulus and other characteristics,and they are also ideal substrates for preparing high-performance foams.Due to the high processing temperature and poor solubility of special engineering plastics,the foaming methods that can match its processability are extremely limited,resulting in less research on special engineering plastic foams.The apperance of supercritical fluid microcellular foaming technology provides a feasible processing method for the preparation of special engineering plastic foam.The supercritical microcellular foaming method can produce a large number of uniform cells of micrometer level inside the polymer matrix,which can effectively reduce the polymer density and obtain a strong and tough microcellular foam material.The supercritical microcellular foaming method lays the technical foundation for the preparation of high-performance polymer microcellular foam materials.In this dissertation,a special engineering plastic-polyarylene ether nitrile was used as the research object,and a new processing technology supercritical carbon dioxide foaming method was used to prepare polyarylene ether nitrile foam materials with different cell morphologies.The influence of the molecular structure,adsorption time,adsorption pressure,foaming time,and foaming temperature of polyarylene ether nitrile on the cell morphology of the polyarylene ether nitrile foam was studied.At the same time,combined with homogeneous nucleation and heterogeneous nucleation mechanisms,the effects of different nucleation points such as interface and functional nanofillers on the cell structure and properties of polyarylene ether nitrile foam were systematically studied.（1）Explore the process of preparing polyarylene ether nitrile foam by supercritical carbon dioxide foaming.By controlling the foaming process conditions such as adsorption time,adsorption temperature,adsorption pressure,foaming temperature,and foaming time,the influence of different foaming conditions on the cell morphology of polyarylene ether nitrile foam was studied.The optimal foaming temperature range is determined by the glass transition temperature of polyarylene ether nitrile,so as to realize the control of the polyarylene ether nitrile cell morphology and foam density.There is a direct relationship between the structure of polyarylene ether nitrile and the amount of supercritical carbon dioxide adsorption.Therefore,the influence of polyarylene ether nitrile with different molecular structures on the cell morphology of the polyarylene ether nitrile foam was also explored,and the adjustment of the polyarylene ether nitrile cell size was realized by adjusting the foaming conditions.（2）On the basis of studying the foaming process and foaming mechanism of polyarylene ether nitrile,two different structures of polyarylene ether nitrile were selected to prepare polyarylene ether nitrile alloy foam.In the foaming process,the phase interface of the two phases provides heterogeneous nucleation points.Under the same foaming conditions,compared with pure polyarylene ether nitrile foam,the cell structure of polyarylene ether nitrile alloy foam is more uniform and the cells size is smaller.The dielectric constant of the polyarylene ether nitrile alloy foam with uniform cell size can be reduced to 2.0,and it has excellent thermal stability.（3）Introducing nano-fillers of different dimensions to provide heterogeneous nucleation points during the preparation of polyarylene ether nitrile nanocomposite foams to prepare polyarylene ether nitrile nanocomposite foams with different cell structures.The effects of nano-fillers of different dimensions on the cell morphology and foam properties of polyarylene ether nitrile nanocomposite foams were studied.The PEN/Si O₂foam obtained by introducing zero-dimensional silicon dioxide（Si O₂）has a bimodal cell structure.The dielectric constant and dielectric loss of the PEN/Si O₂ foam containing 5.0wt%Si O₂ are reduced to 1.71 and 0.0047,respectively.The PEN/CNT and PEN/GNP nanocomposite foams obtained by introducing one-dimensional carbon nanotubes（CNT）and two-dimensional graphene nanoplates（GNP）have different cell morphologies.The multilayer polyarylene ether nitrile nanocomposite film obtained by multi-layer hot pressing of two polyarylene ether nitrile nanocomposite films.The foamed multilayer polyarylene ether nitrile nanocomposite foam has good electromagnetic shielding performance,and the electromagnetic shielding efficiency reaches 30 d B,the specific shielding effectiveness of the multilayer polyarylene ether nitrile foam is better than that of the multilayer polyarylene ether nitrile composite film.At the same time,in order to obtain ultra-low dielectric constant fluorine-containing polyaryl ether nitrile（FPEN）foam,the rosette-like cell structure FPEN/C₆₀ nanocomposite foam was designed,and the dielectric constant and dielectric loss of the FPEN/C₆₀ foam were reduced 1.45 and 0.002.（4）By changing the supercritical carbon dioxide adsorption time to control the supercritical carbon dioxide adsorption capacity of the PEN sample,a partially foamed polyarylene ether nitrile foam with a skin-core structure is prepared under an unsaturated adsorption state.The foam of this structure can not only reduce the density,but also does not lose the strength,and has a good application prospect.Because the thickness of the polyarylene ether nitrile sample is very large,when the supercritical gas adsorption time is lower than the saturation time,the sample cannot reach the saturated adsorption state,and the part of the sample that does not adsorb the supercritical gas cannot form cells,thus obtaining a skin-core structure of polyarylene ether nitrile foam.The polyarylene ether nitrile foam with an adsorption time of 4 h,due to the mutual interaction between the foam and the solid structure,the skin-core structure PEN foam has excellent mechanical properties,with an impact strength of 190 k J/m²,which is a high strength,high toughness and light weight PEN foam.