Application of coupling agent modified powder fill

2022-08-09
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Improve the effect of coupling agent modified powder fillers in plastic processing and application

the common improvement of powder fillers helps to promote the development of China's plastic industry. The modification of fillers by coupling agents has been experienced in China's plastic industry for 20 years. While the modification effect has been achieved, there are also some reflections that the modification has not achieved the desired effect. After investigation and analysis, the plastic modification effect has been achieved, It must be well coordinated with all technical links in plastic processing. Now we put forward our views for reference. 1 the role of non-metallic minerals (powder materials) in the plastic industry in plastic processing, adding appropriate powder fillers can achieve the effect of incremental cost reduction, improve or improve the physical and mechanical properties, wear resistance, thermal properties, aging resistance of plastic products, and overcome the shortcomings of plastic, such as low temperature resistance, low stiffness, easy expansion, easy creep and so on. Therefore, the filler has both incremental effect and modification effect; Some fillers are active and can also play a reinforcing role. The increaser can improve the density, elastic modulus, compressive strength and flexural strength of plastic products, reduce the shrinkage, have good dimensional stability, weaken the dependence of mechanical properties of materials on temperature, and reduce the cost of products; The function of the reinforcing agent is to increase the tensile strength, elongation at break, compressive strength, shear strength, elastic modulus and thermal deformation temperature of the product, reduce the shrinkage of the product, improve its creep, improve the bending and creep modulus, reduce the viscoelastic yield of the load, and improve the tensile strength. Common powder fillers include calcium carbonate (light calcium, heavy calcium, colloidal calcium carbonate). In recent years, with the development of plastic industry, fillers have also developed to functional requirements, and to ultra-fine and ultra-fine. The active calcium carbonate formed by the interfacial modification of fillers can no longer meet the requirements of the development of plastic industry. A broad consensus has been formed on the interfacial modification of fillers with coupling agents. Other fillers, such as talc powder, mica powder, kaolin, silicon dioxide, titanium dioxide, red mud, fly ash, diatomite, glass beads, barium sulfate (calcium), quartz powder, tremolite, alumina, wollastonite, carbon black, silicon aluminum carbon black, brucite, etc., have produced positive effects in plastic processing. Non metallic mineral filler has become an indispensable raw material for the plastic industry. With the progress of modification technology, the type and quantity of non-metallic mineral filler used in plastics will expand rapidly. According to its advantages of low price, unique performance and remarkable modification effect, it plays an important role in the plastic industry. 2 Application of coupling agent modified filler in plastic industry in order to make the composite material achieve the expected performance, the surface of the filler needs to be modified to enhance its compatibility and adhesion with the basic resin. The effects of coupling agent on the interface modification of fillers are: ① improving the quality of plastic products; ② Improve the added value of plastic products; ③ Promote the development of new plastic products and the application of new technologies. In the late 1970s, China digested and absorbed foreign technology to research and produce silane coupling agents and titanate coupling agents, and formed small-scale production in the early 1980s, which played a positive role in the development of China's plastic industry. Subsequently, aluminate coupling agents and rare earth coupling agents were developed and produced in China. At present, there are many types and varieties of coupling agents in China, and their quality and performance should be studied more when applied. The modification of fillers by coupling agents has both physical changes and chemical reactions, and is also related to other technological links in plastic processing. Otherwise, no matter how good the modification effect is, the modification effect may not be reflected on the finished products. 2.1 the combination of modified fillers and other technological links. Plastic processing is the synthesis of various technical conditions. The designers and operators of plastic processing complement each other in processing, rather than competing against each other; Abnormal phenomena in processing or the quality and performance of products do not meet the requirements should be analyzed realistically, which is related to the quality, specifications, formula design, mixing operation of raw and auxiliary materials, equipment, molds, finalization devices, as well as the setting of various process technical parameters and process conditions, which can affect the application effect of modified fillers. Therefore, while improving the quality of filler modification, plastic modification workers should also be familiar with the process and technical requirements of the whole process of plastic processing, and timely eliminate various factors that affect the effect of filler modification, so as to make products achieve good quality performance. 2.2 different types of coupling agents should be selected for different resins, fillers and applications. Most of the fillers are inorganic, and their compatibility with the matrix resin must be considered. The molecular structure and physical morphology of organic polymers are different from those of inorganic substances (powder fillers), and the two materials with different structures cannot be combined together. A coupling agent with amphoteric groups is selected to tightly and firmly combine the fillers with the resin through chemical chain or winding. Table 1 common coupling agent product brand for plastic modification foreign corresponding product brand main chemical composition chemical structure formula applicable polymer system composite monoalkoxy phosphoroxy titanate PVC polyolefin monoalkoxy phosphoroxy titanate unsaturated resin monoalkoxy carboxyloxy titanate PVC polyolefin monoalkoxy pyrophosphoroxy dioctyl titanate melamine resin, epoxy resin chelate ethylene pyrophosphoroxy titanate oxygen resin, Unsaturated resin chelate ethylene pyrophosphoryloxy alcohol amine titanate coordination phosphidoxy titanate. phenolic aldehyde. Epoxy. The surface shape of melamine, amino silicone oil phenolic, melamine Ester Epoxy polyolefin, phenolic, nylon amino silicone oil fillers is very complex. During the crushing process, its surface physical structure is designed to improve the overall performance of various transportation and industrial departments, and changes occur, such as local cracking layer, rough surface after damage, and the increase of surface concave convex points, resulting in the difference between the surface chemical structure and the internal chemical structure; In particular, the existence of surface functional groups can react with water or oxygen in the air, and oh exists along the direction of the surface layer and at the cross section perpendicular to the surface layer; The surface of SI2 is usually coated with silanol =si Oh, and esh>si silicone ether group; The influence of surface adsorbed water is great; There are many forms of hoh groups on the surface of al23 filler, and its surface structure is more complex than SI2; Hoh also exists on the surface of Ti2. There is a great difference between the surface structure of inorganic fillers and the molecular structure of polymers, which makes it difficult to form a good adhesion at the interface of the composite system. Therefore, the surface modification of inorganic fillers is an important way to improve and improve the properties of composite plastics. See Table 1 for the commonly used coupling agents for plastic modification at home and abroad See Table 2 for the comparison of mechanical properties between the modified filler and the unmodified filler with coupling agent for pp/cac3 system Table 2 Comparison of mechanical properties. The coupling agent in the eye lens is unbroken, so that the longitudinal line of the 10 character scribed line in the eye lens is tangent to the left and right side edges of the wear spot, and the elongation at break/% impact strength of the simply supported beam/melt flow index/g/mil. The impact strength and elongation at break of the No. 2 sample decrease rapidly with the increase of cac3 content. This is the filler hydrophobic organic matter, which has poor adhesion with the resin. The addition of powder filler is equal to embedding stress concentration in the system, and it is easy to crack under the action of external force, Therefore, the impact strength increases from 71 The elongation at break decreased from 616% to 13% When the filler is modified with titanate coupling agent, because there is chemical binding water in the filler, the monoalkoxy group of titanate coupling agent reacts with the hydroxyl group on the surface of calcium carbonate to form a chemical bond, so a layer of coupling agent monolayer is covered on the surface of the filler, which is easy to disperse in the resin, and the coupling benefit is improved; The three long-chain structural units at the other end of the titanate coupling agent are miscible with the polymer, so that the filler is well combined with pp. under the action of external force, the long-chain molecules of the filler can stretch and contract well, so that the product has good elasticity and impact resistance. With the addition of coupling agent, the melt viscosity and shear stress of sample 3 and 4 are smaller than that of sample 2, and the fluidity is improved. As the content of coupling agent increases, the melt viscosity and shear stress decrease. This is because the coupling agent changes the surface energy of the filler, improves its dispersion in PP, and plays a lubricating role, which reduces the melt viscosity of pp/cac3 system. This not only increases the amount of filler, but also reduces the cost, improves some properties of the composite, reduces mechanical wear, and makes the composite have good molding and processing properties. Different coupling agents should be selected for different fillers. Salt and clay have significant effects, but have little effect on calcium carbonate, graphite, calcium sulfate, carbon black, etc. For example, the impact strength, tensile strength and bending strength of silica treated with silane coupling agent and filled with PVC plastic can be greatly improved. And Al (OH) and other fillers. For example, using titanate coupling agent to treat mica and then fill PP composite system can reduce the melt viscosity and improve the processability and mechanical properties of thermoplastic. Azide silane coupling agent can react with any hydrocarbon bond. It has the unique performance of covalent bond connection, so it has a wide range of applications. It is especially effective for nylon, polyester, polystyrene, polycarbonate, polyethylene, polypropylene and polyolefin. It has the advantages of good thermal stability and simple process. In addition to being used for composites, it is also suitable for the modification of plastics and rubber. At present, there is no production of such coupling agent in China. 23 effect of particle size of filler on modification effect the larger the particle size of filler and the smaller the specific surface area, the smaller the contact area with resin, and the worse the physicochemical properties of plastic products. The micronization of particles can increase the specific surface area of the powder. When filled in the resin, the total interfacial force between the powder and the resin increases correspondingly. The more obvious the reinforcement effect is, the wider the application range is. The particle size of 01 ~ fine cac3 is used as rubber filler, with half reinforcement for 0 01~0. Super fine cac3 can play a reinforcing role. At present, both at home and abroad are investing in the development, application and research of nano (nm) particles. The quality and performance of coupling agents are directly related to the modification effect. At present, there are many kinds of coupling agents in China, including silane, titanate, aluminate, aluminum titanium composite, rare earth, etc., forming market competition. For the evaluation of coupling agents, a research unit is selected to compare the modification effects of four different coupling agents on brucite. The results are as follows. The change of particle size (m) of the sample modified by 1% coupling agent: unmodified, 19.9; Coupling agent ① modified sample, 18.5; Coupling agent ② modified sample, 11.1 coupling agent ③ modified sample, 19.1; Coupling agent ④ modified sample, 231 See Table 3 for the comparison of water absorption of 325 mesh brucite modified by coupling agent Table 3 water absorption (GOOG filler) comparison of the proportion of coupling agent in the modified sample * * day 10 day 20 unmodified coupling agent ① coupling agent ② coupling agent ③ coupling agent ④ analysis of the action intensity of the four coupling agents on brucite: ① and ② have the same central atom Ti, and the difference between the two is mainly the difference between the groups connected on the right side, ① is dioctyl pyrophosphate, ② is isohard ester acyl. Comparing ① and ②, it can be seen that the electronegativity (2.1) of P in ① is less than that of C in ② (25), and the binding force between ① and the filler surface is less than ②; ① There is hydrophilic polar group -oh in ②, but not in ②, so the hydrophobicity of ② is better than ①; ① The molecular weight of ① (1189) is greater than that of ② (955). ① has many branched chains and large steric hindrance, and its surface covering capacity to the filler exceeds ②. 2. Compared with ③, other parts are similar, and the central atom is different. Their central atom electronegativity is ti1.32al1.17 respectively Comparison between the two: the metallicity of titanium is stronger than that of aluminum

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