| In recent years,with the increase of automobile demand,rigid polyurethane foam has a broad application prospect in automobile lightweight.More and more enterprises are increasing the research on preparation technology of rigid polyurethane foam.Based on SRIM and LFI-PUR long fiber reinforced production lines of polyurethane foaming process in Yangtze Automobile Interior Trim Co.,LTD.,this paper prepared polyurethane foam materials and glass fiber reinforced polyurethane composite materials from different manufacturers,studied their main properties,and analyzed the problems existing in Yangtze Automobile Interior Trim Co.,LTD.For example,there are defects in automotive interior parts,cracking of PMMA/ABS panels for RV,warping deformation of flat door parts,etc.,systematic technical analysis,process improvement and quality control:(1)According to the test and production results of the polyurethane A materials of three manufacturers in the workshop of Yangzi Automobile Interior Decoration Co.,LTD.,and combined with the characterization methods of viscosity,process,material properties,bubble structure and so on to detect the polyurethane A materials of three manufacturers,the evaluation standards for the quality inspection of polyurethane raw materials are formulated.For the polyurethane A material in storage,the following requirements must be met:at 20℃,the viscosity of A material should be below 400 mpa·s;Polyurethane AB material at 30℃free foaming,milky time in 40-50 seconds,rise time in 90 seconds;The bending strength and compressive strength of foam should reach about 7.5MPa and 3.7MPa respectively.The pore size distribution should be relatively uniform.Under nitrogen atmosphere,the residual carbon rate of 800℃ should be more than 20%.(2)Due to the cracking phenomenon of PMMA/ABS material on RV forehead in the process of use,in order to analyze the cracking cause and solve the cracking problem of PMMA/ABS.In this paper,by simulating the actual production process,the mechanical properties of PMMA/ABS under different chemical media were studied.It was found that both A material and B material would lead to the decrease of the toughness of PMMA/ABS material,among which,the influence of B material was the most obvious at 50-70℃.The elongation at break of PMMA/ABS material is reduced to less than 10%.Infrared,scanning electron microscopy and 3D analysis show that the influence of material A is mainly due to its composite solvent or non-solvent components,which will reduce the connection between rubber polymer and SAN phase,resulting in the reduction of compatibility and adhesion between them,and the structure and performance of the interface will be damaged.And solvent erosion,resulting in the surface of ABS plastic pits and roughness.The influence of B material is mainly because its isocyanate group reacts with hydroxyl and carboxyl groups on the surface of PMMA/ABS material,and B material has swelling phenomenon on the surface of ABS.In order to prevent the influence of residual polyurethane raw materials on PMMA/ABS materials,a suitable water-based coating polyvinyl alcohol was found through the comparison of different water-based coatings,and the mechanical properties of PMMA/ABS materials were tested by infrared spectroscopy,scanning electron microscopy and other methods.The results show that the polyvinyl alcohol coating can effectively block the influence of residual polyurethane material on PMMA/ABS material.(3)In the production process of polyurethane foam flat doors,the phenomenon of warping deformation often occurs,which greatly increases the cost of enterprises.In order to reduce the amount of deformation,this paper studies the influence of different contents and types of glass fibers on glass fiber reinforced polyurethane foam composites.The mechanical properties(flexural properties,compressive strength)and density of the composites increased with the increase of glass fiber,while the coefficient of linear expansion decreased significantly with the addition of 7.5-15 wt%glass fiber.In addition,the addition of glass fiber will also affect the bubble structure of the foam,resulting in the deformation of the hole structure at the joint of glass fiber and polyurethane foam,especially the deformation of the bubble structure of the edge felt at the gathering place of polyurethane foam.3B glass fiber and long glass fiber can disperse well in the matrix and bond well with the matrix interface.When preparing fiber-reinforced plastic parts,different distribution of glass fiber in polyurethane foam matrix will cause different contraction degree of fiber row arrangement direction and other directions,which leads to warping deformation of flat plate door parts.The 15%3B glass fiber reinforced composites under S-RIM process and the 15%long glass fiber reinforced composites under LFI process are the best.Considering the cost and performance,7.5%3B glass fiber and 7.5%stitched felt can be selected as co-reinforced composite materials. |
