The Synthesis And Modification Of Carboxyl Acrylic Rubber

Acrylate rubber(ACM)is a kind of special rubber with saturated main chains,and has good resistance to heat,oil,and weather.In addition,the raw materials for ACM are cheap.Therefore,ACM is widely applied in automotive industry.At present,only a few types of ACM rubber are produced in China,among which the yield of chlorinated ACM is the largest.However,chlorinated ACM will bring not only pollution for environment,but also corrosion for the metal parts.Based on this,carboxyl ACM was prepared via emulsion polymerization method.the structure and properties of carboxyl ACM were characterized,and the vulcanization mechanism was discussed.Next,hexafluorobutyl acrylate(HFBA)was introduced into the ACM molecular chain as copolymerization monomer,and the effects of HFBA contents on the oil resistance,hydrophobicity and mechanical properties of ACM were investigated.Furthermore,ACM was reinforced with reduced graphene oxide(RGO)to prepare ACM/RGO composites.The effects of RGO on the heat resistance and mechanical properties of ACM were studied.The main research contents and results of this paper are listed as follows:Firstly,using acrylic acid(AA),butyl acrylate(BA)and ethyl acrylate(EA)as monomers,carboxyl ACM was synthesized via semi-continuous seed emulsion polymerization.taking 1# vulcanizing agent(HMDC,hexamethylenediamine carbamate)and accelerator DPG(diphenyl guanidine)as vulcanizing systems,carboxyl ACM was vulcanized to make its molecular chain crosslinking.The effects of different monomer contents on the monomer conversion rate,particle size and distribution of ACM rubber polymerization systems were investigated.The chemical structure of carboxyl ACM was confirmed by Fourier transform infrared spectroscopy(FTIR).The glass transition temperature(Tg)of ACM rubber with different monomer contents was analyzed by DSC,and the oil resistance and mechanical properties were tested.It was found that the tensile strength of ACM was gradually increased,and the elongation at break was decreased with the increase of AA contents.When the content of AA was 8%,the tensile strength of the ACM was improved to 7.40 MPa from 3 MPa of the blank sample,and the Tg was raised to-15 °C from-22.40 °C.Secondly,in order to improve the hydrophobicity of the carboxyl ACM,hexafluorobutyl acrylate(HFBA)was used as functional monomer to modify ACM to synthesize fluorinated acrylate rubber(FACM),and the structure was confirmed by FTIR and energy dispersive X-ray spectroscopy(EDS).The surface hydrophobicity of FACM was characterized by contact angle meter.The oil resistance and mechanical properties of FACM with different HFBA contents were tested.The results showed that the surface contact angle of FACM was gradually increased with the increase of HFBA contents.When the content of HFBA was 8%,the surface contact angle was increased to 90°,which was approximately twice of pure ACM.Meanwhile,due to the encapsulation of fluorine-containing side groups,the oil absorption rate and elongation at break of FACM with 8% HFBA were decreased to 9.32% and 244% from 11.47% and 606%,respectively.Finally,in order to improve the mechanical properties of the carboxyl ACM,the ACM emulsion was first mixed with the graphene oxide(GO)solution via emulsion blending,and then the GO in situ was reduced by hydrazine hydrate to prepare the ACM/RGO rubber composites.The transformation of GO to RGO was confirmed by FTIR,X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and Raman spectroscopy(Raman).Transmission electron microscopy(TEM)and scanning electron microscopy(SEM)showed that RGO was uniformly dispersed in ACM.The effects of RGO contents on water resistance,heat resistance and mechanical properties of ACM were investigated.The results showed that the tensile strength,tear strength and hardness of ACM/RGO composite was gradually increased with the increase of RGO contents,and the elongation at break was decreased.When the content of RGO loaded was 2%,the tensile strength of ACM/RGO-2 reached 18.80 MPa,which was approximately 5.5 times of unmodified ACM.Meanwhile,the change of the elongation at break was not obvious.Additionally,water absorption rate of ACM/RGO-2 was decreased to 18.40% from 54.60% for the barrier of RGO.