The basic function of PVC processing AIDS is to improve the processing performance of PVC and promote the plasticization of PVC mixture, so as to obtain good plasticizing materials at the lowest possible temperature and improve product quality. According to the needs of different products, we have developed the following five types of processing AIDS.
1, universal type: promote the plasticization of materials.
2. Lubrication type: it can not only promote the plasticization of materials, but also strip metal, prevent the melt from sticking to the metal surface and prolong the start-up period.
3. Bright type: In addition to promoting the plasticization of materials, it can also significantly improve the surface brightness of products, which is suitable for products with high surface finish.
4. Super-plasticizing type: the ability to promote the plasticization of materials is higher than other types, and it is suitable for materials that are difficult to plasticize, such as materials with high calcium carbonate content and large amount of lubricants or additives, such as carbon black and fibers.
5. Super melt strength type: In addition to promoting the plasticization of materials, it can also greatly increase the melt strength of materials, improve the stability of production, extend the production cycle and improve the mechanical properties of products, especially for products with high calcium carbonate content (greater than wt30%).
Mechanism of promoting plasticization
No matter which processing form of PVC is used, it is necessary to plasticize the PVC mixture evenly. Only plasticized materials can have good appearance and mechanical properties.
However, compared with other common plastics, unplasticized PVC can only be plasticized under high temperature and shear conditions, but it is easy to decompose at high temperature. In order to ensure uniform plasticization and improve the quality of hard PVC products, materials should be plasticized at the lowest possible processing temperature and the greatest possible shear force. Generally speaking, PVC processing AIDS must have the following characteristics to promote plasticization.
1, the melting temperature is lower than that of PVC, and it melts before PVC during processing.
2. Because of its good compatibility with PVC, it can adhere to PVC particles after melting in the processing process, increasing internal friction, improving shear torque and generating internal heat, so that the temperature distribution in the material is uniform and the plasticization degree is uniform, thus promoting the uniform plasticization of PVC materials.
3. The processing aid has a large enough molecular weight, which increases the viscosity (or strength) of the melt during processing, improves the melt pressure and prevents the material from slipping, thus increasing the shear torque, greatly increasing the friction heat between the melt and the metal surface, and promoting the mixing uniformity and plasticization degree of the PVC mixture.
Application mode
The essence of processing aid ACR is solid plasticizer. If the melting point and molecular weight of ACR are further reduced, it will eventually become a plasticizer. It is found that processing AIDS (including plasticizers) with low melting point have fast plasticizing speed and good melt fluidity, but low melt viscosity, low melt strength and low melt pressure. Processing AIDS with high melting point have slow plasticizing speed and poor melt fluidity, but they have high melt viscosity, high melt pressure, high melt strength and strong later plasticizing ability. The former reduces the mechanical properties and weather resistance of PVC materials, while the latter hardly affects the mechanical properties of PVC materials and improves the weather resistance.
A certain processing ACR with good plasticizing effect will greatly increase the current and torque of the extruder for one PVC formula and improve the plasticizing degree of PVC, but for another PVC formula, the color of PVC products may become darker and appear chromatic aberration. Sometimes processing ACR is suitable for fast extruder, but not necessarily for slow extruder, and vice versa. Therefore, it is almost impossible for a processing ACR to meet the requirements of different formulations, different products and different processing equipment. Similarly, the traditional processing aid ACR can not meet the processing requirements of rapid plasticization, high melt strength and pressure. In order to meet the personalized requirements of customers, we have developed a series of brand-new processing AIDS with different plasticizing properties and other characteristics to meet the requirements of users, some of which can completely replace some imported products. We have studied the properties and uses of these processing AIDS in detail. As long as customers put forward their own specific requirements, the company's new materials research center can recommend the applicable product model, dosage and usage to you.