The Study On Preparation,structure And Properties Of Natural Rubber Latex/Chitin Nanocrystal Composite Films

Natural rubber latex(NRL),which comes from natural rubber tree,is a kind of renewable biomass material,but its application is limited because of the poor mechanical properties of solid natural rubber(NR).Therefore,the enhancement of NRL has been attracted significant attention all over the word for a long time.The most common nanoparticles such as carbon black and montmorillonite are non-renewable and have poor compatibility with NRL.Carbon nanotubes and graphene are two up-to-date fillers,however,the preparation process of both carbon nanotubes and graphene are high energy consumption,high cost and are not easy to be produced on a large scale.Chitin is mainly derived from shrimp shell and crab shell.Especially,its derivatives,chitin nanocrystals(ChNFs),are characterized by high crystallinity,high tensile strength,high elastic modulus and biodegradability.In this paper,chitin nanocrystals(ChNFs)as a biomass material,are selected to study its reinforcing effect on NRL.The variety of the surface groups of ChNFs may lead to different interaction force,and then affect their dispersion in NRL.In addition,nano-fillers with high content can significantly improve the mechanical properties of polymers,but always lead to the aggregation of nanoparticles and poor dispersion.The method to prepare high content ChNFs/NRL used now is usually divided couple steps as follow,first,prepare the dispersion of ChNFs,and then combine it with NRL,and finally prepare the composite by casting molding.This method was not only time-consuming,but also too complex for processing.Therefore,it is necessary to find a simple way to prepare NRL with the high content ChNFs.This paper is mainly focus on the influence factors of dispersion of surface groups of ChNFs in NRL and how to realize the high content filling of NRL with ChNFs.Both the strategies of surface modification and in-situ ultrasonic dispersion were used in this paper.The effects of the different ChNFs surface groups on the dispersion of ChNFs in NRL and high content ChNFs on the properties of ChNFs/NR composites were studied,respectively.It was found that the dispersion of carbonylated chitin nanocrystals(CChNFs)was better than that of zwitterionic chitin nanocrystals(NC-ChNFs)in NRL and C-ChNFs/NR had higher Young's modulus and lower percolation threshold than NCChNFs/NR.It was also found that filling with high content ChNFs in NR not only significantly increased the stress at constant strain and storage modulus of NR composites,but also endowed them multi-stimulus response.The improvement of the stress at constant strain and storage modulus of ChNFs/NR composites were realized by adjusting the surface groups of ChNFs to change the dispersion of ChNFs in NRL and filling with high content ChNFs.This work provides an idea of how to improve the dispersion of ChNFs in NRL and a method of how to fill with high content ChNFs in NRL,and also broadens the application field of ChNFs/NRL composites.At the same time,this work can be used for reference to realize the uniform dispersion of nano-materials in polymer and how to fill nano-particles with high content in polymer.