| Polyvinyl chloride (PVC) is one of the five major general plastics used worldwide, which accounts for about 30% of the total amount of synthetic resin. With its nonflammable and anti-erosive properties as well as good insulation and isolation effects, PVC has the second largest volume of resin production in the world only next to polyethylene, and has been regarded as one of the most widely applied plastic varieties. Along with the advances in science and technology, unplasticized PVC are mainly used in the production of pipes, sticks, building materials, interior flooring materials, furniture boards, toys, sports equipments, medical tube elements, packaging coatings and etc. The application of unplasticized PVC, however, has always been restricted due to its poor properties in terms of fragility, tenacity, heat resistance and thermal stability. Thus, how to improve its comprehensive performance and expand its application is the most urgent task we face right now.The performance of polymer material can be improved by inorganic rigid particle, because it can not only maintain the polymer material's excellent performance but also increase its toughness, so the composite material based on polymer will have high mechanical properties and electrical properties. However, different inorganic rigid particles have different impacts on the polymer's performance, and inorganic rigid particles will lead to the occurrence of agglomeration, so the appropriate filler, modifier and modification process will make the PVC material evenly dispersed in matrix, satisfy the production's performance and processing performance requirement, and also increase the filling volume.Micro-crystal muscovite is a new member to the family of micaceous minerals which was discovered in Western Sichuan of China in recent years. Compared with other common silicate minerals (e.g. kaolinite, montmorillonite, illite and bentonite), micro-crystal muscovite is more resistant to heat, acid or alkaline, weather, and ultraviolet with higher intensity and chemostability as well as better insulation and anti-aging effects. In addition, it is also more grindable and chemically active with a smaller grain size when compared with traditional muscovite minerals. This material is a high-quality inorganic rigid particle and it is expected to be widely applied in polymer.In this paper, micro-crystal muscovite/ACR/PVC composite material was prepared by melt blending, with micro-crystal muscovite as packing material, silane coupling agent KH-550 as surface modifier, core-shell type ACR resin as impact modifier and PVC resin as matrix. This paper also optimized the condition of silane coupling agent KH-550 as surface modifier, the chemical properties of composite material ,the thermal stability, the processing of complex, the microscopic appearance and so on .Furthermore ,this paper also studied the mechanism of combined modification of PVC with micro-crystal muscovite and ACR. Results mainly showed that:1. The effect of dry surface modification of micro-crystal muscovite is significantly influenced by the stirring speed, dose of surface modifier and duration of surface modification. Within the experimental range, a stirring speed at 25000 r/min, a duration of modification of 300 s, and a dose of silane coupling agent KH-550 at 1.2 % of the weight of micro-crystal muscovite are deemed to be the most appropriate.2. Surface modification of micro-crystal muscovite using silane coupling agent KH-550 can significantly improve the mechanical properties of the micro-crystal muscovite/PVC composite material. This is because the unmodified micro-crystal muscovite has very poor interfacial compatibility with PVC, which means that adding such micro-crystal muscovite may increase micro-cavities and defects inside the composite material and reduce its physical strength.3. After surface modification with silane coupling agent KH-550, micro-crystal muscovite can significantly improve the mechanical properties of the micro-crystal muscovite/PVC composite material. The tensile strength and impact strength of the composite material initially increase with the addition of micro-crystal muscovite, and then begin to decrease when the amount of micro-crystal muscovite becomes excessive. The peak values of its tensile strength and impact strength are identified when 35 ~ 40 portions of micro-crystal muscovite have been added, 24.2 %~26.8 % and 28 %~30 % higher than those of normal PVC, respectively. Besides, the Young's modulus, bending strength, bending modulus and hardness of the micro-crystal muscovite/PVC composite material gradually increase with the addition of micro- crystal muscovite. Within the experimental range, i.e. 5 ~ 45 portions of micro-crystal muscovite, the max of Young's modulus, bending strength, bending modulus and hardness of the micro-crystal muscovite/PVC composite material are enhanced by 65.5 %, 15.2 %, 71.6 % and 32.8 %, respectively. Based on comprehensive analysis, the most appropriate amount for micro-crystal muscovite addition in the micro-crystal muscovite/PVC composite material is determined to be 35 ~ 40 portions.4. Adding ACR with core-shell structure can significantly improve the toughness of the micro-crystal/ACR/PVC composite material. In the experiment, with the same addition of the micro-crystal muscovite (35 phr), the micro-crystal/ACR/PVC composite material has a impact strength of 11.5 KJ/m2, which is 167 % of the micro- crystal/ACR/PVC and 213 % of the pure PVC. However, this will make the tensile strength and Young's modulus decrease. Based on comprehensive analysis, the micro-crystal /ACR/PVC performance will be considered as the best when the ACR is 3 phr~9 phr.5. Adding micro-crystal muscovite using silane coupling agent KH-550 can also improve the thermal stability of PVC. The glass-transition temperature, Vicat softening temperature and thermal stability increase accordingly with more micro-crystal muscovite added into the micro-crystal/PVC composite material. When the micro-crystal muscovite is 35 phr ~ 40 phr, the PVC composite material's glass transition temperature increase 5.1℃~7.9℃, and the Vicat softening temperature increase 16.4℃~20.2℃, which significantly improve the thermal stability. Moreover, ACR can further increase the glass-transition temperature of the PVC, with same micro-crystal muscovite addition (35 phr) and ACR addition(3 phr~9 phr), the ACR addition does not significantly affect the Vicat softening temperature with an increase of 14.3℃~17.6℃compared with that of the pure PVC. As a result, micro-crystal muscovite and ACR can modify PVC, improve its thermal stability, slow down its aging and widen its application.6. Micro-crystal muscovite can affect the composite processing performance of PVC, increase the plant time and torque of the micro-crystal/PVC composite material, which is not conducive to processing. But adding ACR can reduce the plant time and facilitate the processing.7. By analyzing the composite material's impact on the fracture sections'SEM, the micro-crystal muscovite without surface modification disperses unevenly and has clear interstices with PVC matrix, so the bending in interface is wake. When the micro-crystal muscovite surface is modified by silane coupling agent KH-550, it will disperse evenly in PVC matrix and enfold by PVC matrix, which will improve the bending. With the addition of micro-crystal muscovite, the distance of micro-crystal muscovite in PVC matrix decreases, which will form the tension delivery point and improve the tensile strength. By adding ACR, the"porous structure"forms in the micro-crystal/ACR/PVC composite material with a size of 200 nm, which will significantly improve the composite material's impact strength.8. Adding ACR with core-shell structure can significantly improve the toughness of the micro-crystal/ ACR/PVC composite material. When ACR is melt blended with PVC, the PMMA in the surface has good compatibility with PVC and its molecular chains twine together; while the PBA of core does not melt, so the"porous structure"forms in the micro-crystal/ACR/PVC composite material. These microcellular structure can absorb the power of the impact and greatly increase the toughness of the composite material. The micro-crystal muscovite has good compatibility with PVC matrix when its surface is modified by silane coupling agent KH-550 and is dispersed in PVC matrix. Further more, some of the micro-crystal muscovite particles will contact with PVC molecular chain and obstruct the molecular chain movement, which will increase the glass-transition temperature.
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