| In order to decrease the nonpenerative injury caused by back bulge of ultra-high molecular weight polyethylene fiber (UHMWPEF) bulletproof composites, carbon fiber (CF) can be combined with it and the structure of bulletproof armour can be designed into composite structure of UHMWPEF/CF. But because of its strong chemical inertness, UHMWPEF has selectivity to resin, layers of UHMWPEF/CF composite armor cannot be adhered well. To solve this problem, the composite interlayer adhesive and UHMWPEF surface treatment process was taken as objectives, and the influence factors of resin modification reaction, the reaction kinetics, curing of modified resin, fiber surface treatment process and adhesive performance of composite layers were all studied in this paper.The methyl acrylate epoxy resin was prepared by using the methacrylic acid (MAA) modifying the E-51 epoxy resin. The influences of catalyst kind and dosage, temperature and duration on the reaction extent which was represented by acid value of the system were researched. The result shows that, the catalytic efficiency of triethylamine (TEA) is better than that of N, N-dimethylpropylamine (DEBA), and the reaction rate can be increased by improve the catalyst dosage and reaction temperature within limits. Catalyzing by 0.6% TEA, the modification reaction kinetics was studied and the reaction rules of MAA modifying epoxy resin were received. The Resin modified process was carried out in accordance with the law of first-order reaction, its reaction activation energy E is 26.92 kJ/mol and frequency factor A is 1.786 s-1.In addition, the resin before and after the modification was analyzed by Fourier transform infrared spectroscopy (FTIR) spectrum and the reaction mechanism was verified by it. It can be proved that the modification reaction has high selectivity of main reaction under this process. The comparison of the appearance and viscosity between resins of different reaction degree shows that the conjugate action between isopropenyl and the ester group introduced by modification reaction makes the resin display color, and the color deepens with the reaction degree increasing. The viscosity of the modified resin increased because the molecular weight and polarity of resin increase after modified. With 1% benzoyl peroxide (BPO) as initiator, the gel performance of different modified resin was studied. The result shows that the gelation time of the modified resin decreases as the temperature increases but there is no evident regularity of the change rate. At the presence of the same catalyst, the lower the acid value of modified resin, the shorter the gelation time.The curing process of the modified resin was characterized by differential scanning calorimetry (DSC) withl% BPO as the initiator. The preparation process of composites with the modified resin as adhesive was 1% BPO as initiator,80℃/ 15min/0.5MPa→120℃/1h/1MPa. Compared with E-51, the curing temperature of modified resin was more compatible with the UHMWPEF composites molding temperature. In addition, the curing reaction kinetics model of the modified resin was received by studying the curing kinetics. Using the dynamic model to analyze the curing process under different heating rate, it can be found that, with the curing degree increases at different heating rate, the curing speed increases firstly and then decreases. Besides this, the maximum curing rate increases with the enlargement of the heating rate, and it moves toward the direction of the curing degree increased.The UHMWPEF/unidirectional CF composite layers were prepared according to the mentioned process above. Through testing its peel strength and the microstructure of the stripping surface with different modified resins as adhesive, it can be found that, when the acid value of modified resin achieve 24.1mgKOH/g, the adhesive strength increases the most, and increases by 20% than that of unmodified resin composites. According to the rules of reaction degree with the change of various influencing factors, and take the stability of the resin system, the main reaction selectivity and the adhesive strength of composite layers into account, the resin modified process was determined to be:reacting 2 hours at 110℃ with 0.6% TEA catalyzing.In order to further improve the adhesive strength between the two composite layers, the surface treatment of the UHMWPEF was conducted through the liquid phase oxidation method. Firstly, three kinds of surface treatment process were selected through the scanning electron microscope (SEM) analysis of the fiber surface morphology. Then the fibers were carried out on the surface treatment under these three processes. After the surface treatment, the degree of fiber surface etching 80℃/ 5min> 25℃/1h> 60℃/30min, the improvements of the surface chemical structure 60℃/30min> 25℃/1h> 80℃/5min and the intensity of monofilament 60℃/30 min> 80℃/5 min>25℃/1h.It can be seen that, the best fiber surface treatment process cannot be selected only from the contrast of the fiber surface physical structure and chemical structure. So the application performance of fibers under different treatment processes was studied. T-peel strength of the UHMWPEF/unidirectional CF composite layers was 80℃/5min> 60℃/30min> 25℃/1h, and T-peel strength of the UHMWPEF/CF woven fabric composite layers was 60℃/30min> 80℃/5min> 25℃/1h. Under the same surface treatment process of UHMWPEF, T peel strength of the UHMWPEF/CF woven fabric composite layers was significantly higher than using unidirectional CF. Through testing T-peel strength of the composites and the SEM analysis of stripping surface microstructure, it was be found that, after the surface treatment, T-peel strengths of the composite layers were more than doubled and the bonding strength between the layers were improved obviously. After comprehensive comparison, it can be seen that, the contribution of fiber surface treatment was greater than modifying the resin in improving the adhesive strength of UHMWPEF/CF composite layers. |
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