| The interface is the essential ingredient of the resin matrix composite. The properties of the composite are directly dependent on the properties and structures of the interface. Fibers can not chemically bond with the matrix due to the lack of functional reaction groups in the matrix. Accordingly, interface is prone to be the weakness of composite and easy to get broken under the interfacial stresses, which leads to the frature of composite. The sizing agent for glass fiber is composed of coupling agent、film former and other auxiliaries, which can effectively protect glass fiber surface and improve the interfacial adhesion between the reinforcing materials and matrix resin. However, the present sizing agents for glass fiber are lack of the functional groups which can chemically react with the fiber and resin, respectively. Herein, the interfacial adhesion strength can not meet the need of the requirements of the composites. Moreover, the present sizing agents that possess short molecular chains are not able to obtain an entanglement action.It has been proved that reaction-type macromolecular coupling agent possess two kinds of polar chains which are located in the fiber/matrix resin interface. The polar chains of the macromolecular coupling agent are able to react with the fiber while the nonpolar ones can react with the matrix resin. Accordingly, glass fiber and matrix resin are bonded together through the chemical reaction, which improves the interfacial compatibility between them. The reaction-type coupling agent of excellent properties can be prepared through the reaction between two kinds of monomers according to the molecular design of the sizing agent for glass fiber. However, the current molecular design is restricted to the micromolecule design as well as adding the interfacial modifiers into composite during the preparation process. There have not been reports about coupling moleculars design in the previous works. The molecular design method was applied to synthetize a macromolecular coupling agent in this study. Poly alkylene glycol allyl glycidyl ether (AEPH) which has C=C bonds in one end and epoxy group in other end was reacted with y-aminopropyltriethoxysilane (KH-550) to synthetize the macromolecular coupling agent through addition polymerization. Alkoxy groups of KH-550and the C=C bonds of AEPH were still existent after the reaction. The residual C=C bonds could participate the subsequent cured reaction. The hydrolytic alkoxy groups could react with the glass fiber surface. By adding the nano-SiO2particles into the emulsion, several sizing agents could be obtained. Numbers of characterizations were carried out to evaluate the properties of the sized glass fibers and glass fiber composites. The main researches in the thesis are as follows:(1) Design of macromolecular coupling agent. By referring to relevant literatures, macromolecular coupling agent was designed through the reaction between poly alkylene glycol allyl glycidyl ether (AEPH) andγ-aminopropyltriethoxysilane (KH-550). The coupling agent which possesses alkoxy group at one end and C=C bond at other end could chemically react with the fiber and resin, respectively. Furthermore, the interfacial adhesion strength of the composite obtained an improvement due to the physical entangling action of the long molecular chain of the macromolecular coupling agent.(2) The technological conditions of the macromolecular coupling agent preparation were studied. Then the technological conditions were optimized. The optimum technology parameters were as follows:the mass ratio of AEPH to KH-550was1.95:1, reaction temperature was80℃, reaction time was3h. FITR analysis indicates that the reaction between AEPH and KH-550was carried out according to the design. C=C bonds and alkoxy groups existed in coupling agent and the macromolecules were formed. The macromolecular coupling agent was obtained as the designed structure.(3) By using the nano-SiO2particles as the stabilizer, vinyl ester resin (VE) type film former emulsion was prepared through the phase inversion emulsification method. The optimum preparation conditions were as follows:the emulsifiers cetyltrimethylammonium bromide (CTAB) and castor oil polyoxyethylene ether (EL-40) were mixed at a mass ratio of1:3, the mass ratio of emulsifiers to VE was 4:100, the mass ratio of nano-SiO2modified by KH-550to VE was2:100, the stirring rate was8000r/min. The emulsion could maintain no creaming on the condition of80℃, pH ranged from1to13. Nano-SiO2particles were uniformly distributed on the glass fiber surface after sizing. Accordingly, the roughness of glass fiber surface was changed. The abrasion resistance of sized glass fiber and the adhesion strength of glass fiber composite were improved.(4) The influences of the macromolecular coupling agent on the properties of glass fiber were carried out. The macromolecular protecting film on the glass fiber surface could improve the fracture strength, cluster and the abrasion resistance of fibers. On the alkali liquor condition, the weight loss ratios of desized fiber, commercial fiber and the fiber szied with four kinds of formulas were different. The glass fiber sized with2.0%macromolecular coupling agent percentage of the sizing agent possessed the lowest weight loss ratio of different formulas and it was also lower than that of the commercial glass fiber (CTG).The macromolecular coupling agent type sizing agent with the nano-SiO2particles possessed a good stability due to the uniform particle size distribution (mainly in nano scale). The cluster and abrasion resistance of the fiber were greatly improved after the glass fibers were sized with the above sizing agnet. There was not only a polymer layer but also a particles layer uniformly distributed on the glass fiber surface after sizing. A rugged surface of glass fiber made the composite properties a great improvement.(5) The interfacial properties of composite can be evaluated by interlaminar shear strength (ILSS)、fracture microstructure surface and absorptivity of composite. Composites based on glass fiber sized with nano-SiO2particles could obtain different degrees of improvement in flexural strength and ILSS. When the nano-SiO2particles was2.0%percentage of the film former emulsion, the composite could reach the maximum value. With the increase of macromolecular coupling agent of the sizing agent, the size of the fracture appearance turned smaller and the interfacial adhesion between the glass fiber and matrix resin got tighter. Composite based on glass fiber sized with sizing agent formular3possessed the best interfacial adhesion. Water absorption of the composites after sized indicates differences. When the nano-SiO2particles was2.0%percentage of the szing agent, the composite possessed the lowest water absorption.This work is supported by the Natural Science Foundation of Shandong Province of China (No.ZR2011EL032) and Science and Technology Develop Project of University of Jinan (No. XKY1001). |
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