Study On In-situ Interface Chemical Compatibilization Of High Density Polyethylene/Ground Tire Rubber Thermoplastic Vulcanizates

Since China's reform and opening-up,the domestic automobile industry has made remarkable progresswith the rapid development of economy in our country,meanwhile,promoting the fastgrowth of the tire industry.And the annual output of the waste tire reaches 300 million in 2015 year.As one kind of thermosets,the waste tire is difficult to degradate under natural conditions.And that a large pile of waste tireson the earth's surface,easily leads to a seriouspollution of atmosphere,soil and surface water,endangering human health and safety.Under the requiry of sustainable development strategy and simulation of economic interest,the treatment of waste tires changes from traditional approach—landfill disposal,used as fuel,thermal decomposition of scrap tire,etc.to green,environmental friendly and more valuable solutions.The themoplastic vulcanizates can be prepared via the melt blending of thermoplastic plastics and ground tire rubber(GTR)whose dosage is more than 50 wt%,which not only can realize environmental recycling of GTR,but also can realize the recycling of resources.However,the highly crosslinked GTR and thermoplastic plastics are incompatible.Therefore,the key to the preparation of the thermoplastic vulcanizates is to increase the interfacial strength of the blends,so as to promote the compatibility of the materials above.In order to achieve more valuable recycled of GTR,the high density polyethylene(HDPE)is chosen to prepare the HDPE/GTR thermoplastic vulcanizates due to its good chemical stability and electrical performance,more importantly,owing to its prominent processability.Based on the active chemical groups(including carbon-carbon double bond,carboxyl groups and hydroxyl groups)on the GTR surface,the in-situ interface chemically compatibilizing of HDPE/GTR blends has been realized through adding the different kinds of reactive compatibilizers into the blends.And the HDPE/GTR thermoplastic vulcanizates also has been successfully prepared,which is of low cost and optimum mechanical properties.Firstly,the dicumyl peroxide(DCP)and thermoplastic phenolic resin(HY-2045)were used to in-situ interface chemically compatibilize HDPE/GTR blends through chroman structures-formation reaction and free radical grafting reaction based on the carbon-carbon double bond on the GTR surface.Sceondly,the surface modification of GTR was achieved through the reaction between the epoxy groups on the GMA and carboxyl groups on the GTR surface,and then the in-situ interface chemical compatibilization of HDPE/GTR blends was realized via the free radical grafting reactioninitiated DCP.Finally,the maleic anhydride(MAH)and DCP were also used to in-situ interface chemically compatibilize HDPE/GTR blends according to the reactive hydroxyl groups on the GTR surface,and the compatibilizing mechanism is similar to the above with the difference being the modified reaction of GTR surface occurred between acid anhydride groups on the MAH and hydroxyl groups on the GTR.The compatibility of the blends was improved by the chemical bond connection at the interface which was summed up from the compatibilization methods above,so as to prepare the thermoplastic vulcanizate with excellent properties.The excellent compatibilizing results of three methods above were obtained via the analysis of the mechanical properties,crystalline performance,morphological properties,etc.of the thermoplastic vulcanizates above.It is found that the stable chemical bond connection resulted in prominent interfacial strength of the blends according to the morphology analysis,which led to a large number of fibrous materials distributed in the interface,connecting the HDPE matrix with GTR.After the analysis of the mechanical properties of the HDPE/GTR thermoplastic vulcanizates prepared by the three kinds of compatibilization methods above,it is found that the HDPE/GTR(40/60)thermoplastic vulcanizates with the addition of 0.40 phr DCP and 4.00 phr HY-2045 exhibites the prominent mechanical properties,the tensile strength,elongation at break and tear strength being 13.85 MPa,209.60%and 76.48 kN/m,respectively,which is increased by 74.65%,229.56%and 102.44%,and that HDPE/GTR/GMA/DCP(40/60/0.75/0.30)thermoplastic vulcanizates also exhibites the excellent mechanical properties,the tensile strength,elongation at break and tear strength being 10.22 MPa,206.58%and 61.76 kN/m,respectively,which is increased by 28.89%,224.81%and 63.47%.The thermoplastic vulcanizates with the prominent mechanical properties described above,not only has the practical use value,but also the production cost is low.Therefore,the way to prepare the HDPE/GTR thermoplastic vulcanizates above can provide a new approach to the more valuable recycling of the GTR.