| Geopolymer is a kind of three dimensional structure aluminum silicate inorganic polymer composed by the [AlO4] and [SiO4] tetrahedron, which was mainly preparared by aluminum silicate or industrial waste. Geopolymer has high strength, corrosion resistance, water resistance, high temperature resistance, enclosed metal ion, and many other advantages, but its typical defect is "brittle", so toughening modification of geopolymer is more active.Polyvinyl chloride (PVC) is one of the five biggest common thermoplastic resins, because it has flexible molecular chain, excellent comprehensive performance, the application of PVC material has related to various fields. If the high toughness PVC resin is compounded with brittle geopolymer materials, which will greatly improve toughness of geopolymer material, simultaneously geopolymer will also improve high temperature performanceresin of PVC. Based on the above ideas, this dissertation systematically studied thepreparation technology at high temperature of geopolymer/polyvinyl chloride (PVC) composites, and the performances of the composites were characterized and explored.In the dissertation, pure geopolymer was prepared with metakaolin, sodium silicate, sheet alkali and water, and the preparation technology parameters of geopolymer were also optimized. Moreover, geopolymer matrix materials with high mechanics performance were prepared. geopolymer was toughened by polyvinyl chloride (PVC) with organic polymer flexible molecular chain characteristics, through the plasticate pressing method. In addition, with the characteristic of inorganic rigid particles and high temperature resistance for the geopolymer, PVC was modified by the blending method and in situ polymerization, and the research results were used in the preparation of PVC sheets. The research results are as follows:(1) In the pure geopolymer preparation process, the rheological properties, curing time, microstructure and mechanical properties of geopolymer under the high temperature condition were studied. The results showed that, according to the strength of the geopolymer as the basis, the optimum proportion and technological parameters of geopolymer was determined as:the molar ratio of (SiO2)/(Al2O3) was3.3, the molar ratio of (Na2O)/(SiO2) was0.27, the molar ratio of (H2O)/(Na2O) was11, and the aging time of sodium silicate was24h, the curing temperature was60℃, the curing time was48h. So the strength of geopolymer reached to the highest,28d compressive strength and folding strength of geopolymer reached to89.63MPa,13.87MPa, respectively. High temperature moulding results showed that170℃,the initial setting time and final setting time of geopolymer slurry were11and16minutes, respectively. After the water sodium ratio of geopolymer was increased (14), the condensation time of geopolymer slurry extended. The reaction heat of geopolymer reflected that the increase of curing temperature could improve polymerization reaction rate and shorten the slurry setting time. Rheological properties showed that exerting shear force in polymer processing during the high temperature moulding process was helpful for flow moulding of geopolymer materials.(2)Toughening modification of geopolymer was used PVC during the network structure process of geopolymer, because molten PVC molecular chain and polymerization of geopolymer worked together, which formed interpenetrating network of geopolymer composites. Through the high temperature rheology test, it was found that when PVC content was less than50wt%, the modulus of composites was bigger and bigger and the whole composites were characteristic of solid features of geopolymer because the contribution of the viscous features of PVC have been covered by the contribution of the elastic response. Its processing parameters were as follows: plastification temperature of PVC was175℃, plastification time of PVC was6minutes, heat preservation time was10minutes after plasticated under170℃,15MPa. The mechanical strength results of geopolymer toughened by showed that the28d bending strength reached to55.87MPa when the addition of PVC was40wt%, which was improved by3.1times compared with that of the pure geopolymer.(3) The toughening modification of PVC was joined the geopolymer slury into PVC resin under coagulation stage of geopolymer, whose network structure was bonded by winding PVC molecular chain, resulting in enhancing the geopolymer and matrix PVC interface effect. Mechanics performance test results showed that, the geopolymer composites had good mechanical properties when geopolymer content was less then10wt%compared with pure PVC, of which4wt%content geopolymer was the optimum, and the impact strength of the PVC based composites reached to9.13KJ·m-2, which increased by40%compared with that of pure PVC. Vicat softening, thermogravimetric analysis, differential scanning calorimetry characterization results of PVC based composites showed that, vicat softening temperature increased by2-6℃compared with that of pure PVC. After geopolymer was joined into PVC, thermal stability of the Geolymer/PVC composites was enhanced because geopolymer inhibited and absorbed the releases of the HCl from PVC resulting from the molecular chain defect structure of PVC.(4) In situ polymerization of Geolymer/PVC composites was prepared with geopolymer modfied by silane coupling agent organic and vinyl chloride monomer through the fall loading process by in situ polymerization, and then by plasticated pressing.The temperature, pressure, conversion, stirring electric current of suspension polymerization system were studied. Mechanical properties testing results showed that the impact strength of Geolymer/PVC composites increased by59.4%, the tensile strength of Geolymer/PVC composites increased by13.8%, the elongation at break of Geolymer/PVC composites increased by7.65%compared with that of pure PVC when the geopolymer content was3wt%. The thermal decomposition activation energy calculated by Kissinger method showed that apparent activation energy of PVC/polymer composite by in situ polymerization and pure PVC material were274.78J·mol-1and152.06J·mol-1, respectively. The thermal decomposition activation energy of Geolymer/PVC was obviously higher than that of the PVC,which proved that the introduction of geopolymer improved the decomposition activation energy of PVC matrix resin and showed that its thermal stability was improved.(5) According to the above research conclusion, different amount of geopolymer were mixing fully with PVC and applied in PVC sheet production process, the mechanical properties of PVC composites were higher than that of the pure PVC sheets. In addition, aging resistance of PVC composite was greatly increased and significantly improved the durability of PVC sheets composites. |
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