The role and effect of talc in plastic modification

The most important use in plastics is a white finely pulverized product that can produce a thin sheet structure. Due to the special flaky structure of talcum powder, it is an effective reinforcing material in plastics, regardless of normal temperature and high temperature. Underneath, it can impart high rigidity and creep resistance to plastics, and the fine talc powder with white flake structure also has good solid luster. Mineral talc is a kind of hydrated magnesium silicate. The theoretical chemical formula is 3MgO·4SiO2·H2O. Depending on the place of production, the composition of the talc powder used in plastic modification may vary from 300 mesh to 3 depending on the application and the type of plastic. 000 items vary. ..

2 Effect of talcum powder on plastic properties

The addition of talc can change the properties of plastics such as molding shrinkage, surface hardness, flexural modulus, tensile strength, impact strength, thermal deformation temperature, molding process and product dimensional stability.

(1) The addition of talc to the plastic can effectively improve the molding shrinkage of the plastic product, thereby improving the surface properties of the product. Figure 1 shows the effect of the addition of talc on the shrinkage of the polypropylene plastic molding. It can be seen from the figure that as the content of talc increases, the shrinkage of polypropylene plastic molding decreases gradually. The addition of talc increases the viscosity and decreases the creep, thus reducing PP. Crystallinity; talc itself has no shrinkage, which reduces the overall material shrinkage; fine The talc powder can also act as a nucleating agent for PP, which acts to change the structure of PP, prevents the formation of PP large spherulites, and also reduces the crystallinity of PP.

(2) Surface hardness and surface scratch resistance are also requirements for the use of certain plastic products. The addition of talc to polyethylene and polypropylene plastics can effectively improve the surface hardness and surface scratch resistance of the product.
(3) Flexural modulus, which is the rigidity of the product we often say, is an important indicator of the use of plastic products, especially for engineering plastic products. The addition of a white flake structure of talc to any of the plastics can significantly increase the flexural modulus and can be multiplied. This is one of the most notable features of talc for general mineral filling. At this point Calcium Carbonate is not as good as talc. Figure 2 shows the effect of the addition of talc on the flexural modulus of polypropylene plastics. As can be seen from the figure, as the talc content increases, the flexural modulus of the polypropylene plastic increases exponentially.

(4) The talc powder has a limited improvement on the tensile strength of plastic materials. The talc powder content can increase the tensile strength within a certain range, the talc powder content continues to increase, and the tensile strength will decrease. For some plastics, the addition of talc will not only increase the tensile strength, but will decrease. Figure 3 is a graph showing the change in tensile strength of a material after adding 1500 mesh activated talc to polypropylene. It can be seen from the figure that the tensile strength of the talc powder is less than 20%. When the talc content is above 20%, the tensile strength of the material gradually decreases with the increase of the content, mainly talc powder. The increase has weakened the intermolecular attraction of polypropylene.

(5) The effect of talc on the impact strength of plastic materials is similar to the effect of talc on the tensile strength of plastic materials. Figure 4 shows the effect of several mineral additives on the toughness of polypropylene materials. It can be seen from the figure that various mineral additives have impact toughness when the content is less than 10 parts. Improve, greater than 10 At the time of impact, the impact performance began to decrease, and the performance of talc was better than that of CaCO3 and mica powder. It is also found in the experiment that the fineness of various mineral additives has a great influence on the impact toughness. The greater the fineness, the better the toughness of the material.

(6) The effect of talcum powder on the heat distortion temperature of plastic materials is obvious, which can effectively improve the heat distortion temperature of various plastics, thereby increasing the heat resistance of plastics. Fig. 5 is a graph showing changes in the heat distortion temperature of the material after the 800-mesh activated talc powder was added to the polypropylene.

(7) The influence of talcum powder on the molding process of plastic materials is mainly due to the fact that talc powder can effectively improve the fluidity and molding shrinkage of plastic materials, thereby improving the stability of product molding and improving product quality, especially for some melt strength. Low plastics, with the addition of talc, can effectively increase the melt strength, which is very effective in extrusion molding, such as polypropylene and nylon in extrusion molding. In addition, the addition of talc to the plastic material improves the molding shrinkage, thereby greatly improving the surface flatness of the plastic product and the dimensional stability of the product. ..

3 Application characteristics of talc in plastics

(1) Economics

It is well known that the price of talcum powder is 10% to 20% of plastics, especially the price of plastic raw materials is rising. Today, the addition of talc powder can effectively reduce the cost of materials and improve the economic benefits of enterprises. Of course, the addition of talc is not in Cost can be reduced at any time, and in some cases, product costs are increased due to restrictions on the amount of addition and high product quality requirements.

(2) Improvement of comprehensive performance

Since the addition of talcum powder can change the various properties of plastics, many effective properties are improved. For engineering plastics, it is not acceptable to add talc in many occasions, such as requiring heat resistance, requiring rigidity, and requiring hardness. The surface is required to be flat, requiring convenient molding, weight, and the like.

(3) In different plastic materials, the application characteristics of talc are also different. In addition to the economic benefits of adding talc to ABS and nylon, the performance is mainly heat resistance and molding shrinkage. The addition of talc to polyethylene is mainly due to rigidity, heat resistance, molding shrinkage and cost reduction. The addition of talc to polypropylene is the most widely used and has the greatest effect, such as an increase in overall strength, an increase in heat resistance, a decrease in mold shrinkage, an increase in rigidity, and, in addition, a high-order talc powder in polypropylene. It can act as a nucleating agent and can effectively improve the overall performance of polypropylene.
4 How to use talcum powder (1) Powder direct addition The talc powder is directly mixed with the plastic raw material and extruded into a modified plastic raw material by a twin-screw extruder, which is a commonly used method in plastic modification, and is also the most economical method.
(2) Carrierless masterbatch The talc is prepared into a carrier-free loose granule by a special process, and then the granule is mixed with a plastic raw material and granulated into a modified plastic raw material by a twin-screw extruder. There are two advantages to using this method. One is to reduce the dust pollution in the production process and improve the working environment. The second is to improve the delamination between the particles and the powder during the mixing process, and to improve the uniformity of the materials in the mixing process. Sex, thereby improving the quality of the product.
(3) Filled masterbatch The talc powder and the plastic carrier are mixed and granulated by an extruder to form a high content of the masterbatch. The masterbatch can be directly mixed with the plastic raw material, and the finished product is processed by extrusion and injection. This method is convenient to use, but the dispersion is not good. Some products with high quality requirements cannot be used.
5 Some considerations for the use of talcum powder (1) The talc powder must be surface-activated to activate the surface of the talc powder, mainly to improve the compatibility between the talc powder and the plastic raw material, and to increase the modification effect. Different surface treatment agents should be selected for different plastics.
(2) The dispersibility of talc in plastic raw materials. Under the same formulation conditions, the dispersion of talc in plastic raw materials has great influence on the final physical and chemical properties of the modified materials. It should be strictly controlled in the production process, affecting the talcum powder in plastics. The main factors of dispersibility in the raw materials are formulation, temperature, yield, process, and the like. In addition, when the amount of talc added is large, a stepwise addition method can be employed to achieve a good dispersion effect.
(3) For different plastics, different requirements should be chosen for different specifications of talcum powder to achieve the desired results. This is very particular, and poor choice may be counterproductive. Because different plastics, different products, different use conditions have different requirements for raw materials, so different choices must be made to achieve the desired results.