Preparation And Evaluation Of Evironmental Friendly Fibers/Styrene-free Soybean Oil Resin Composites

In recent years,it is increasingly attractive for using environmental friendly fibers to replace traditional glass fibers and synthesized fibers as reinforcements for thermoset composites preparation.However,the widely used of petroleum-based matrices and the emission of carcinogenic styrene which was used as reactive diluents during resins and composites processing has dramatically limited their industrial applications.In this study,acrylated epoxidized soybean oil(AESO)has been selected to replace traditional petroleum-based resins such as unsaturated polyester in formulating novel green thermosets because of their similar curing behavior and performance.Meanwhile,a variety of low volatility and high reactivity comonomers were chosen to participate in free-radical polymerization of AESO resins instead of styrene and fabricate environmental friendly fiber reinforced composites.Besides,a high reactive monomer was synthesized using methacrylic anhydride and glycerol as raw materials,and blended with AESO for making soybean-oil-based thermosets as matrices in composites.The rheological behavior and curing mechanism of resins were analyzed,and the static and dynamic mechanical properties and thermal properties of composites were evaluated.The main work is detailed as follow:(1)Two methacrylate monomers,i.e.,1,4-butanediol dimethacrylate(BDDMA)and trimethylolpropane trimethacrylate(TMPTMA)were respectively used as reactive diluents(RDs)for replacing anticipatory carcinogenic styrene.Then,styrene-free soybean-oil-based resins and its composites reinforced with bamboo fibers were fabricated.According to Hansen’s theory,the miscibility of BDDMA and TMPTMA with AESO was predicted.The processibility of resins was determined by the relationship between viscosity and temperature.An excess of double bonds on methacrylate monomers contributed to higher crosslinking desity of resins,presenting better curing behavior.Meanwhile,the low emission of methacrylate monomers reduced the release of volatile organic compounds during resins and composites processing.The resulting composites have competitive static mechanical properties and superior thermomechanical performance and thermal resistance in comparison to styrene-mixed resins compsites.(2)Two high reactive bifunctional monomer,isocyanatoethyl methacrylate(IEM)and 3-isopropenyldimethylbenzyl isocyanate(TMI),were also seleted for replacing St to formulate styrene-free AESO resin.The viscosity and emission of volatile organic compounds of the resulting AESO resins decreased dramatically,while their crosslinking efficiency rised up.Because the isocyanate groups on comonomers can concurrently bond with hydroxyl groups on fibers and AESO,the obtained hemp fiber/AESO composites have competent tensile strength and tensile modulus,flexural strength and flexural modulus,and impact strength with styrene-mixed resin composites with a lower dosage of reactive diluents.Besides,the improved composites interfacial adhesion contributes to preferable composites dynamic mechanical properties and water resistance.(3)A novel RD,glyceryl trimethacrylate(GTMA),was synthesized from glycerol that is a byproduct of biodiesel and methacrylic anhydride.This RD was blended with AESO to formulate styrene-free AESO resin.Then,recycled polyethylene terephthalate hybrid fibers(RPHFs)were used as reinforcements in preparing composites.The chemical structure of synthesized GTMA was confirmed via Fourier Transform Infrared Spectrosope(FTIR)and Nuclear Magnetic Resonance(NMR)analyses.This monomer was well miscible with AESO resin and had low volatility,enabling it to replace styrene as RD in resins.Besides,the excessive unsaturated sites on GTMA contributed to higher cure degree and thus fabricated RPHFs/GTMA-AESO composites with competent mechanical properties and thermal resistance.