The Flame Retardancy And Moisture Absorption Of Fiber/Polypropylene Composites

Recently,the two major problems of petroleum resource shortage and environmental pollution have become increasingly prominent.Research and application of biodegradable polymer materials have become a hot topic.The renewable and biodegradable natural fiber reinforced composites has attracted more and more attention.Compared with the traditional chemical fiber,natural fiber has the advantages,such as low density,high specific strength and high specific modulus,good flexibility,low cost and abundance.Natural fiber will gradually replace the traditional application of chemical fiber in composite materials.Polypropylene is a kind of general plastic.It is odorless,non-toxic,heat resistant,and easy processing.To apply natural fiber to reinforce polypropylene can reduce the cost of polypropylene and improve the performance of composite materials.It can also help to solve the problem of resource shortage and environmental pollution.In order to improve the moisture absorption and mechanical properties of natural fiber reinforced polypropylene(PP)composites,three methods were compared:(I)N-[3-(trimethoxysilyl)propyl] ethylenediamine(AAPTS),(II)eighteen alkyl three methyl bromide(STAB),(III)N-[3-(trimethoprim based on silicon)propyl]-ethylenediamine eighteen alkyl three methyl bromide(AAPTS-STAB)synergistic modifications in aqueous solution.The Fourier Transform Infrared(FTIR)spectroscopy measurement showed that the three kinds of modification methods on the linen were successful,in the light that the alkyl hydrocarbon chain was grafted onto the fiber surface.The linen and PP composite were compounded by melt pressing.In order to improve the hygroscopicity of composite materials,the hygroscopicity of linen was improved first,and thereafter the interface adhesion between fiber and matrix and the mechanical properties of composite materials were also improved.The moisture absorption,mechanical properties and thermal stability of composite materials was characterized.It was found that the moisture absorption of STAB modified linen reinforced PP composite(PPF2)was lower than that of the untreated linen reinforced PP composite(PPF)and AAPTS modified linen reinforced composite materials(PPF1).The moisture absorption of PPF and PPF1 was reduced by 22.4% and 24.5%,respectively.The study showed that the moisture absorption and the mechanical properties of linen/PP composites were improved when the linen was modified with surfactant STAB.In addition,to improve the flame retardant of hemp fiber,it was in-situ modified with the mixed solution of sodium hydroxide and calcium chloride.Hemp-reinforced polypropylene(PP)composite with excellent flame retarding and mechanical properties was prepared with the melt blending method.Hemp fiber was first simply in-situ modified with inorganic salt solution,which was prepared by mixing 4.32% sodium hydrate(NaOH)and 6% calcium chloride(CaCl2)at room temperature for 0.5 h.The modified hemp(F1)was proved to be attached with calcium salt through Fourier-transform infrared and scanning electron microscopy(SEM)measurement,including calcium carbonate.The thermal stability,mechanical,and flame retarding properties of the composites were studied by thermogravimetric analysis,mechanical test,and the limiting oxygen index(LOI)measurement,respectively.The LOI of the composites with 50% of F1 and 15% poly(phosphoric acid amine)reached 25.5%,which was much higher than that of PP(18.5%).The tensile strength of the composite with 50% of F1 was 38% higher than that of PP(24 MPa).The composite interface between F1 and PP matrix was investigated by SEM,and was shown to be significantly improved.It showed that the in-situ inorganic modification with the mixture of NaOH and Ca Cl2 on hemp was a promising method to improve both the flame retarding and mechanical properties of the biocomposites.Thermal degradation analysis shows that the thermal degradation temperature of composite materials is higher than 250℃ with the majority of applications.