Research On TPU Engineering Composites With Enhanced Flame Retardancy And Mechanical Properties Prepared By Microlayer Coextrusion Technology

High flame retardant TPU composite materials are widely used in high-rise buildings,automotive interiors,wires and cables,etc.With the rapid development of such fields,the requirements for the material’s own flame retardant properties and mechanical properties are constantly increasing.At present,it is still the mainstream of industrial production to prepare high flame retardant composite materials by adding flame retardant fillers using conventional blended technology,which improves the flame retardant performance of the composite materials to a certain extent,but its improvement is not very satisfactory.At the same time,a large amount of flame retardant fillers must be added in order to meet the high flame retardant standards in the market,which will not only cause serious damage to the mechanical strength of the composite materials,but also lead to a series of processing problems.Hence,how to meet the high flame retardant properties of composite materials while greatly improving their mechanical strength has become a difficult problem to be solved.In order to solve this problem,a new processing technology called microlayer coextrusion technology has been used to replace the conventional blended technology,and through the combination of different types of fillers,the TPU engineering composites with high strength and flame retardant properties are finally prepared.The main research contents are as follows:1.Exploring the feasibility of microlayer coextrusion technology.First,the effect of two different halogen-free flame retardant(expandable graphite and ammonium polyphosphate)added separately on the mechanical properties and flame retardancy of the overall TPU composites by microlayer coextrusion technology was investigated.The results showed that the conventional blended technology would make the flame retardant fillers easy to agglomerate and have poor dispersion in the TPU matrix,which makes the flame retardant performance improvement unsatisfactory.In addition,the flame retardant filler agglomerates in TPU matrix would make the mechanical property of the composites greatly weakened.The exfoliation and dispersion of the flame retardant fillers in TPU matrix could be greatly enhanced by microlayer coextrusion technology,which would greatly promote the formation of the carbonized layer of the composites during high temperature combustion,thereby significantly improving the flame retardant performance of the whole composites.At the same time,both the great dispersion of the flame retardant fillers in TPU matrix and the multilayer structure produced by microlayer coextrusion process would greatly enhance the mechanical property of the whole composites.2.Exploring the best flame retardant properties of composites by compounding flame retardant fillers.In order to further improve the flame retardant performance of the TPU composites,on the basis of the previous step,the microlayer coextrusion technology was used to explore the effect of different compounding ratios of expandable graphite(EG)and ammonium polyphosphate(APP)on the mechnical property and flame retardancy of the TPU composites,and the compounding ratio of the best flame retardancy was obtained finally.The results showed that under the condition that the total flame retardant filler content is 15%unchanged,all different compounding ratios would have a certain further effect on the flame retardancy of the composites.When the compounding ratio was 1:1,the flame retardancy was improved the most,while the mechanical property was almost unchanged.At the same time,compared to the conventional blended technology,the performance of TPU composites was improved a greater extent by microlayer coextrusion technology.3.Exploring the best reinforcement effect of composites on the basis of the best flame retardancy compounding ratio.On the basis of the best flame retardant formula in step two,the influence of adding nano titanium dioxide on the mechanical property and flame retardancy of the composites was investigated.The results showed that as the content of nano-titanium dioxide continues to increase,the flame retardancy of the TPU composites continue to increase,while the mechanical property tends to increase first and then decrease.Compared to conventional blended technology,both the flame retardancy and mechanical property were enhanced better by microlayer coextrusion technology.In this study,TPU engineering composites with enhanced mechnical property and high flame retardancy were successfully prepared,which broadened the application fields of TPU flame retardant composites and provided new ideas and new methods for improving the comprehensive performance of polymer matrix composites with filler loading.