The Synthesis Of A New Coupling Agent For Preparing Natural Fiber Composites

Natural fiber reinforced composites is an emerging area in polymer science. Fibersderived from annual plants are considered a potential substitute for non-renewable syntheticfibers like glass and carbon fibers. The hydrophilic nature of natural fibers affects negativelyadhesion to hydrophobic polymeric matrices. To improve the compatibility between bothcomponents, a surface modification has been proposed. This study focus on synthesis of anovel Coupling agent which endow the hemp fiber with hydrophobicity and strength , so itcan improve the compatibility between the hemp fiber and unsaturated polyester, and thenenhance the properties of the composite materials.Frist We synthesised a unsaturated polyester through condensation polymerization ofmaleic anhydride and N-Methyldiethanolamine ,and then reactived with epichlorohydrin,through this we confered epoxy and quaternary ammonium salts cation into the unsaturatedpolyester chain unit .This process were studied by 1H NMR and Fourier Transform infraredspectroscopy (FTIR). Then we treat the hemp fiber with the synthsized new Coupling agent.After drying, we dig the fiber into another uansaturated polyester solution, then cure it byheating at 160℃on the hot-press. The hemp fiber reinforced unsaturated polyester compositematerial is just synthesied. Mechanical testings indicated that tensile strength , modulus andbending strength increased with the increase of the fiber content, while the bending moduiusdecreased. In addtion, the water absorption rate increased with the increase of the fibercontent. When the fiber content was 40%, we compared the composite material modifiedwith the adhensive for wood with unmodified one, finding that the tensile strength andbending strength of the modified hemp fiber increased 10% and 47.3% respectively, whiletensile modolus and bending modolus increased 46.5% and 27.5% respectively. Thewater absorption rate of the modified hemp fiber decreased evidently comparing with theunmodified hemo fiber. Finally electron microscopy was applied to evaluate the surfacechanges of fibers after modification process. The result proved that the compatibility betweenhemp fiber and unsaturated polyester improved effectively by treatment with the couplingagent.the flame retardant properties have also been evaluated by limiting oxygen index (LOI)test. The LOI values show the composite is more flame retardant than the pure unsaturatedpolyester,and the more the content of the fiber the higher the LOI ,also show the surfacemodifacation can not affect the flame retardent of the composites.We also synthesized another Coupling agent by first coupled reaction between thehalogen group and hydroxy group, and then the reaction with the epichlorohydrin. The synthesis process was studied , FTIR and 1H-NMR measurements were applied tocharacterize it. We prepared the hemp fiber and unsaturated polyester composite materialmodified by the adhensive for wood, and tested the mechnical property and waterresistance.