Preliminary Study On The Functional Application Of Epoxidized Natural Rubber/Natural Polymer Composites

With the continuous development of society and economy,the people's requirements for the functions of rubber products continue to increase.Therefore,it is very urgent and practical to process and modify rubber products,expand new functions and applications of rubber,and meet the requirements of more emerging fields.Among them,epoxidized natural rubber(ENR)is widely used in military,automotive,biomedical and other fields because of its excellent wet skid resistance,adhesion,air tightness and oil resistance.In this paper,nano-chitin(CNCs)and carboxymethyl chitosan(CMCS)extracted from crustacean such as shrimp and crabs are compounded with ENR,and their structure and properties are studied.Meanwhile,their new functional applications are explored.The specific research content and result are as follows:(1)The ENR/CNCs composite was obtained by blending CNCs and ENR.Parts of hydroxyl groups of CNCs reacted with the epoxy group of ENR and hydrogen bonds were developed between CNCs and ENR.Meanwhile,CNCs achieve excellent dispersion in rubber matrix,effectively improving the mechanical properties of rubber.Due to the low degree of covalent grafting,there is mainly a reversible hydrogen bond cross-linking network in the composites.Therefore,the rubber molecular chain maintains good mobility,endowing composites with self-healing properties.The ENR/CNCs composite with a filler loading of20wt% exhibits impressive self-healing efficiency of 83% of its original strength and 95% of the original extensibility without any external stimulus at room temperature.Meanwhlie,it was found that the self-healing efficiency of composites is also related to the healing time,healing temperature,healing times and CNCs fillers content.(2)The soluble CMCS is dissolved in water,and then mixed with ENR latex.ENR/CMCS composite is obtained through filming process.During the film-forming process,CMCS was regenerated and fixed in the interstitial space between the ENR latex particles.So the distribution of isolated frame structure was formed in the composites.When the CMCS content reaches 20 wt%,the tensile strength of unvulcanized composites is 1.52 MPa,which is about2.6 times that of pure ENR.Moreover,due to the rich hydrogen bond interaction formed between CMCS and ENR in the matrix,composites could be welded together to restore its original performance at high temperatures after the composites are broken into two parts.The soluble CMCS in the composites can be removed by soaking in deionized water,thereby recovering pure ENR.The composites have potential applications in the field of humidity sensor materials.In addition,different from the filming process,CMCS in solut ion can regenerate irregular shaped fillers and uniformly dispersed in the rubber matrix under the training and hot pressing process,which promoted the contact between the groups of CMCs and ENR to form hydrogen bonding cross-linked network.This not only endows the composite with self-healing properties,but also further improves the mechanical properties of rubber.(3)The conductive fillers of CNT were first mixed with soluble CMCS,and then selectively dispersed between the epoxidized natural rubber(ENR)latexes through the emulsion blending technology.Finally,the ENR/CMCS-10/CNT composite was obtained by hot pressing.Based on the distribution of the framework structure of CMCS in the rubber matrix,CNT also realize special dispersion,which enhances ENR while endows it with conductivity.The tensile strength of nanocomposites is 2 times that of pure ENR while elongation at break remains above 650%.Meanwhile,composite exhibits a percolation threshold as low as 0.83wt%,which has potential applications in strain sensors.What's more,under the action of reversible hydrogen bonding interactions formed by CMCS and ENR,the healing efficiency of the composites can reach 85% after healing at 50 ? for 12 h.(4)In order to build a richer hydrogen bond cross-linking network in the rubber matrix that can endow the composite with self-healing property at room temperature and further improve the mechanical properties.On the basis of the above,CNCs,CMCS and CNT were selectively dispersed among the rubber latex particles by using ultrasonic assisted film laying technology to obtain composites with filler frame structure.When the addition amount of CNCs and CMCS was 10 wt%,and the CNT content reaches 5 wt%,the tensile strength and Young's modulus of composites are 3.46 and 4.6 MPa,which is 5.7 times and 3.8 times of pure ENR respectively.Meanwhile,composites show more excellent electrical conductivity.When the CNT content is 5 wt%,the electrical conductivity of the composites is increased by 7 orders of magnitude.In addition,under the action of the hydrogen bond cross-linking network,composite exhibits excellent self-healing properties at room temperature.With addition of 1 wt% CNT,composite exhibited a self-healing efficiency of 91% after healing at room temperature for 24 h.