The Study On Structure And Property Of High Performances PP/EVA/fiber Reinforced Composites

To explore more applications in the field of engineering plastics of polypropylene(PP),fibers including the reed fibers(RW),basalt fibers,wollastonite fibers,brucite fibers and carbon fibers were selected to be as reinforcing agents,the blending of PP and EVA as a matrix resin to improve the impact resistance at low temperature,PP/EVA/fiber reinforcement composites were prepared in this paper.Firstly,the ratio of EVA toughening PP was explored.Considering the cost of raw materials and composites properties,the mass ratio of PP and EVA was 4:1.While the mass ratio was 4:1,the impact strength of PP and EVA blends upped 52.8KJ/m2,which was two times more than that of PP.However,the tensile and flexural strength of PP/EVA composites dropped to 76.2% and 70.7% of PP,respectively.Secondly,the most suitable amount of fibers and the kinds of inorganic fibers added in PP/EVA matrices were studied.The amount of fibers were 30 phr,and the types of inorganic fibers were basalt and carbon fibers optimizied by mechanical properties.Compared with PP/EVA composites,the growth rates of tensile and flexural strength of the composites only adding basalt and carbon fibers in PP/EVA composites were more than 49.2% and 57.1%,respectively.Finally,the surfaces modification of reed fibers adopting alkali treatment to PP/EVA blends(AW),the process conditions of alkali treatment optimized by the orthogonal experiments as follows: reaction temperature was 100?,alkali treatment time was 3h and alkali concentration was 10%.The compatibility between fibers and PP/EVA blends was improved due to the alkali treatment on reed fibers.Compared to PP/EVA/RW composites,the tensile and impact strength of PP/EVA composites adding alkali modified reed fibers increased by 15.5% and 45.7%,respectively.Taking coupling modification and first etching by then coupling treatment onto the surfaces of basalt and carbon fibers,the effects of two treatments methods on mechanical properties of composites were carried out.The results showed that adding the modification of basalt and carbon fibers treated by first etching then coupling treatment(SSi X and SSi C),the tensile strength of composites increased by 5.32 MPa and 5.04 MPa,and the flexural strength of composites increased by 6.36 MPa and 4.44 MPa compared with adding only coupling modification on basalt and carbon fibers.All these demonstrated that first etching then coupling treatment was beneficial to the improvement of mechanical strength of PP/EVA composites.The composites of PP/EVA/AW/SSi X,PP/EVA/AW/SSi C and PP/EVA/SSi X/SSi C were prepared.Experimental results revealed that when the compounding ratio of SSi Xand SSi C was 1:3,the tensile strength,flexural strength and impact strength of PP/EVA/SSi X/SSi C composites reached maximum values 33.69 MPa,52.57 MPa and 10.1 KJ/m2,respectively.The results of thermodynamic analysis declared that the maximum decomposition temperatures of three kinds of composites moved 4-6?backward,and the amount of carbon residue exceeded 23.5%.Of which,the carbon residue amount of PP/EVA/AW/SSi X reached 26.4%.The thermodynamic analysis based of by FOW and Kissinger equations indicated that the highest activation energy reached up to 152 KJ/mol for the PP/EVA/SSi X/SSi C composites,showing that the thermal stability of PP/EVA/SSi X/SSi C composites was enhanced.The results of non-isothermal crystallization analysis showed the compounding fibers not only shorten the crystallization time and increased the rate of crystallization,but also played the heterogeneous nucleation roles in the PP/EVA matrices.When AW and SSi X,or AW and SSi C were added to PP/EVA composites,the Avrami exponents n of PP/EVA/AW/SSi X and PP/EVA/AW/SSi C composites had the larger floating ranges,which were closed to that of PP/EVA composites.But the n of PP/EVA/SSi X/SSi C composites had the stable floating ranges,and the crystallization rate of composites attained the maximum value of 1.26.These indicated that the growth of crystals was changed owing to the heterogeneous nucleation of compounding fibers and the crystals forms steady,which was gainful in improving mechanical properties of composites.When AW,SSi X and SSi C were added to PP/EVA blends,the compounding ratios of these three kinds of fibers were 5:5:20,5:12.5:12.5 and 5:17:8,respectively.Wherein,when the compounding ratio was 5:12.5:12.5,the tensile and impact strength of PP/EVA/AW/SSi X/SSi C composites were best among them,which could reached 29.61 MPa and 8.02 KJ/m2 respectively.The results of thermodynamic analysis indicated that the maximum decomposition temperatures of these three composites in different compounding ratios moved backward 3-4?.And the increasing rates of carbon residue of these three kinds composites gone beyond 22%.The thermodynamic analysis accroding to the Kissinger equation illuminated that there were little differences between the PP/EVA/two kinds of fibers composites and PP/EVA/three kinds of fibers composites in thermodynamic.when the compounding ratios was 5:17:8,PP/EVA/AW/SSi X/SSi C composites had the good thermal stability.Through the non-isothermal crystallization analysis,compared with the PP/EVA/ two kinds of fibers,there were small floating ranges of the n in different compounding ratios of PP/EVA/AW/SSi X/SSi C composites.And the values of the n were far from those of PP and EVA composites.All these illustrated that compounding ratio had little influences on the n,and the mechanism of nucleation and growth dimension of crystals in matrices were also changed by adding three kinds of compounding fibers.The comparisons of composites adding different fibers to PP/EVA blends,indicating that PP/EVA/SSi X/SSi C composites possessed the best performances in mechanical properties,thermal properties and crystallization performance.