Analysis On The Relationship Between The Interface Performance And Filling Effect Of EVOH Modified Bagasse/Common Polyolefin

In order to explore the reasons for the different modification effects of EVOH(ethylene-vinyl alcohol copolymer)on wood-plastic composites,the relationship between the interface performance and filling effect of bagasse modified by glycerol solution of different varieties of EVOH with common polyolefin was studied in this paper.There is listing the experimental materials and reagents,the instruments and equipment,and the preparation methods of related drugs in the first chapter of this article.In the second chapter,by means of measuring the contact angles of bagasse before and after modification with different polar test fluids,and calculating the surface tension of bagasse before and after modification,we respectively studied the effect of process conditions,including modification temperature,washing and placing time,the mass ratio of EVOH to glycerol,EVOH dosage and variety on modified bagasse.The results show that the modification temperature has little effect on the modified bagasse,washing and placing days can further reduce the polarity of modified bagasse.With the decrease of the amount of glycerol,the polarity of the modified bagasse also decreased.When the mass ratio of EVOH to glycerol rised to 1:0.8,EVOH had the best modification effect on bagasse.EVOH,containing ethylene structural unit with 24,35,48,and 93.3 mol%respectively(hereinafter abbreviated as E24,E35,E48,and E93),was used to modify the bagasse,when the modification effect was the best,the optimum amount of EVOH was 3,7.5,9 and 9 wt%of bagasse,respectively.In the third chapter,based on the optimum modification process conditions,the corresponding composite materials were prepared to test the filling effect of bagasse modified with EVOH in common polyolefins.The results show that although the interfacial tension between the modified bagasse and the polyolefin is lower than that of the unmodified bagasse,and the adhesion work(except PVC base)is also higher than that of the unmodified one,the filling effect on the polyolefin is very different.Compared with the unmodified system,only the mechanical properties of the E93 modified PP/bagasse composite slightly improved,while the mechanical properties of the PP(or HDPE)composite filled with bagasse modified with other EVOH were generally decreased,while the performance of the PVC-based composites was better than that of the untreated system,the effect of modification with E35 was best among them,and the tensile strength and bending strength of the material were increased by 25.0 and 29.2%respectively,which compared with the unmodified ones.In view of the above results,from the analysis of whether the molecular structure of EVOH can be entangled with the matrix or form a strong hydrogen bond,a reasonable explanation is given for the above phenomenon,and the existing surface and interface theory is revised.According to the above findings,the entanglement ability between the modifier and the matrix has an important influence on the modification effect.In the fourth chapter,E35 and E93 were selected and degraded.It is hoped that the degradation can make EVOH expose more free and long ethylene segments in its structure,thereby increasing their ability to entangle with the matrix;and the degradation will also improve the melt flow of EVOH,which is beneficial to the modification of bagasse.The experimental results are in line with expectations.The mechanical properties of composites modified by degraded EVOH are higher than undegraded and even higher than unmodified.Especially the tensile properties of the material,the tensile strength of the composite modified with degraded E93 was increased by 14.09%compared with the unmodified one,and SEM also shows that the interface of modified composites has been effectively improved,which indicating that EVOH can expose more free ethylene segments after degradation,but the degradation effect is even more prominent of EVOH with high ethylene structural unit content.Although the degradation of EVOH can improve its entanglement ability with the polyolefin matrix,the improvement is limited.In order to have more entanglement ability,PP was chose to thermally degradation in chapter 5.As PP degradation will introduce polar functional groups and can form hydrogen bonds with bagasse,the degraded PP has a certain degree of modification on bagasse.The results showed that the mechanical properties of composites filled with bagasse modified by degraded PP were best in all PP-based modification systems.The coefficient of linear expansion of the modified system is lower than that of the unmodified one,indicating that the interface integration of the composite material is improved.The thermal stability and crystallinity of the composites modified by degraded PP are both improved.SEM shows interfacial properties of degradated PP-modified PP matrix composites has been improved.These results further demonstrate that the length of the molecular chain entanglement between the modifier and the matrix can promote the interface integration of the composite material to be closer.Summarizing the results of the third,fourth and fifth chapters,the following conclusions can be drawn about the modification effect of EVOH:under the condition that both the surface properties and interfacial properties between the phases of the composite material are satisfied,the interaction between the EVOH and the matrix is an important factor in determining the modification effect.This intermolecular force can be provided by the molecular chain entanglement between the EVOH and the polyolefin,and can also be obtained by hydrogen bonding.However,the current adhesion work theory,which is used to judge the interface combines strong and weak,is based on the data of surface tension and interfacial tension,it has certain limitations.