Preparation Of Hyperbranched Polymer Grafted Carbon Black And Their Application Research In Natural Rubber

Natural rubber(NR)is an important material obtained from the Brazilian rubber tree.Among the existing various rubbers,natural rubber has many useful properties that synthetic rubber lacks,such as excellent toughness and strength.It is widely used in industry and agricultural products.In medical products and consumer goods,such as conveyor belts,medical gloves,shoes,etc.Natural rubber is still considered as a sustainable polymer considering the depletion of global petroleum resources.However,NR tends to become soft and sticky at high temperature,and becomes brittle and hard at low temperature.Therefore,it is necessary to add reinforcing materials to increase its internal cross-linking density,limit the movement of macromolecular chains,and improve its performance under different temperature conditions.Carbon black(CB)is a commonly used reinforcing material in the production of rubber products.The addition of CB in the rubber processing process can not only greatly improve the tensile strength,tear strength and other properties of the vulcanized rubber,but also greatly reduce the manufacturing cost.However,due to its high surface energy,CB is not uniformly dispersed in the rubber matrix,which leads to a significant decrease in the mechanical properties of the vulcanizate.In addition,dry mixing has the disadvantages of high energy consumption,high pollution and poor working environment.In order to cope with this challenge,in recent years,many researchers have tried to use latex blending method to achieve good dispersion of fillers in the rubber matrix instead of traditional dry mixing to solve the problem that dry mixing CB cannot be uniformly dispersed.However,the highly hydrophobic nature of the CB surface severely limits its application in the field of latex blending.Therefore,it is crucial to develop an effective method to prepare hydrophilic CB and achieve good mixing between CB and latex.In the past ten years,polymer modification on the surface of CB may be an effective technique to improve the dispersibility in water,which has been reported by many scholars.Although the method of polymer graft modification has a certain effect on improving the dispersibility of CB,the molecular chain structure characteristics of linear polymers lead to the entanglement of molecular chains,which may cause the CB particles to re-aggregate and form new of aggregates.Hyperbranched polymers have good solubility,low viscosity,a large number of active functional groups,molecular chains that are not easy to entangle,and easy synthesis methods,etc.,which have attracted wide attention from many researchers.Therefore,they are widely used in inks,coatings and drug carriers and has a relatively broad application prospect.In recent years,hyperbranched polymers have been used for surface modification of carbon materials including carbon nanotubes and carbon fibers in order to obtain composite materials with excellent comprehensive properties.These studies indicate that grafting hyperbranched polymers onto the surface of carbon materials to improve the dispersion of fillers and thus enhance the strengthening effect of carbon materials on composites is indeed an effective and desirable technology.This paper focuses on the preparation of hyperbranched polymer grafted CB and its effect on the mechanical properties of natural rubber.The hyperbranched polymer grafted CB and NR were blended by using dry mechanical blending method to prepare vulcanized rubber,then,Water dispersed hyperbranched polymer grafted CB and NR latex were blended by using latex blending method to prepare vulcanized rubber,and the properties of the two kinds of vulcanized rubber and the unmodified CB filled vulcanized rubber were compared.The main contents of the research are as follows:1.Synthesis and characterization of hydroxyl-terminated hyperbranched esters and amino-terminated hyperbranched esters(1)Different hydroxyl terminated hyperbranched polyesters HTHBP-G2,HTHBP-G3 and amino terminated hyperbranched polyester ATHBP-G2,ATHBP-G3 and ATHBP-G4 of different algebras were prepared.(2)The synthesized different generations of hydroxyl-terminated hyperbranched polyesters and amino-terminated hyperbranched polyesters were analyzed.The molecular structure of the two polymers is similar to the expected structure,which indicates that has successfully synthesized relatively regular hydroxyl-terminated and amino-terminated hyperbranched polyesters.2.Preparation and characterization of amino-terminated hyperbranched polyester grafted CB(1)First,CB was oxidized to carboxylated carbon black(CB-COOH),and then the third generation of amino-terminated hyperbranched polyester was grafted onto the surface of CB by EDC/HOBt dehydration system,Thus,amino-terminated hyperbranched polyester grafted CB was prepared(CB-g-ATHBP).The effects of the feeding ratio and reaction time of CB and amino-terminal hyperbranched polyester on the grafting rate were investigated and the optimum reaction conditions were determined.(2)The structure of CB-g-ATHBP was characterized.The results showed that the amino-terminated hyperbranched polyester was successfully grafted on the surface of CB.According to the analysis of dispersion stability of CB-g-ATHBP,the number of aggregates decreased to a certain extent after grafting amino-terminated hyperbranched polyester on the surface of CB,CB-g-ATHBP could disperse more stably in organic solvents(DMF).3.The application of CB-g-ATHBP in natural rubber and its properties(1)CB and CB-g-ATHBP were used as the reinforcing materials to fill natural rubber to prepare NR/CB vulcanizates And NR/CB-g-ATHBP vulcanizates.(2)The performance test results show that that the compatibility between CB and rubber is improved after amino-terminated hyperbranched polyester was grafted on the CB surface,CB-g-ATHBP can also be more evenly dispersed,and has better interaction with rubber matrix in rubber.4.Preparation and characterization of grafted CB by carboxy-terminated hyperbranched polyester(1)Carboxylated CB(CB-COOH)was prepared,then 2-hydroxy propane-1,2,3-tric-arboxylic acid is grown layer by layer on CB surface to prepare Carboxy-terminated hyperbranched polyester grafted CB(CB-g-CTHBP).(2)The results of CB-g-CTHBP structural characterization show that that the surface of CB was grafted with polyester successfully.The results of dispersion stability show that CB-g-CTHBP can spread more stably in water.5.Application and properties of CB-g-CTHBP in natural rubber latex(1)CB-g-CTHBP was prepared into a water-based dispersion,which was mechanically blended with natural rubber latex to prepare wet-masterbatch.NR/CB-g-CTHBP vulcanized rubber was prepared by drying,mixing and vulcanization,and NR/CB vulcanized rubber was prepared by dry mixing.(2)The performance test results show that show that the surface grafting of CB with hyperbranched polymers is beneficial to improve the dispersion of CB in rubber,and the CB-g-CTHBP can be more evenly dispersed in rubber.The further improvement of the wettability of rubber by CB makes the interaction between the grafted CB and rubber matrix stronger.