First, we need to know that PPA is the abbreviation of Polymer Processing Aid. In addition, we often see another kind of PPA, Polyphthalamide, which is a high temperature resistant nylon. Although the abbreviations of the two PPAs are the same, they should not be confused in use because they have different purposes and functions.

Special plastic manufacturers

Processing aids are the general name of several kinds of materials used to improve the processing and processing properties of high molecular weight polymers. It mainly plays a role in the melting state of polymer matrix, and can play the same role as lubricant in reducing the viscosity of polymer melt. However, compared with traditional lubricants, the processing aids have the advantages of high efficiency and less addition. In addition, processing aids also have the functions of eliminating melt fracture, reducing material deposition, reducing gel formation, etc. Therefore, they are separated from the concept of lubricants and listed as a new type of additives. At present, the processing aids on the market mainly include fluororubber aids, silicone aids, dendrimers and polyethylene glycol.

In recent years, with the expansion of the application field of polyolefin and engineering thermoplastic resin, the research and products of processing aids for polyolefin and engineering thermoplastic resin are increasing, which promotes the rapid development of novel and efficient additives. Fluoropolymer processing aid is a new generation of processing aid, which is improved from fluoropolymer elastomer. It has excellent ability to improve processing performance, and is a new type of efficient, excellent and practical aid under development.

1. What is fluoropolymer processing aid (PPA)

Zui In recent years, a large number of technologies applied for fluoropolymer processing aids (PPA) have emerged at home and abroad. The product components of each company are different. In general, it is a copolymer of one or more fluoroolefins or a copolymer of fluoroolefins and other olefins. Such as the binary copolymer or ternary copolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, and the copolymer of vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene and ethylene or propylene. There are also compounds with other polymers, such as polyoxyethylene, inorganic substances, etc., to form polymers with more diverse components.

Mechanism of PPA in Mouth Mold

Fluoropolymer processing aids make use of the extremely low surface energy of fluorine compounds, which can reduce the internal friction within the processing resin molecules in plastic processing, increase the melting rate and melt deformation, reduce the apparent viscosity of the melt, and improve the overall plasticizing effect. At the same time, it has low solubility and incompatibility in the processing resin. During the processing, it seeps from the melt to the melt surface, forming an isolation layer on the metal surface, reducing the adhesion between the melt and the metal surface of the machine body and the die mouth, reducing the friction between the melt and the device wall during the movement, and improving the uneven state of the melt movement during the processing. Therefore, fluoropolymer processing aids refer to a kind of fluoroolefin containing copolymer compound used to improve resin processing performance and product quality.

2. Functions of fluoropolymer processing aids

(1) Improve the processing rheology of low melt index resin. When processing low melt index resin, due to the high viscosity of the melt, the screw torque increases and the pressure in the barrel increases, forcing the plastic processing to increase the processing temperature, which increases the processing difficulty. The use of fluoropolymer processing aids can properly solve a series of problems.

Special plastic manufacturers

(2) It can eliminate melt fracture during blow molding, reduce bubble chatter, improve processing stability, and eliminate the "shark skin" phenomenon on the film surface.

Eliminate shark skin melt fracture

(3) Reduce the material accumulation at the die mouth, and reduce the phenomenon of uneven film thickness. The quality of the film is improved by reducing the generation of gel and crystal point in the melt.

(4) During LLDPE processing, the die opening clearance will not be intentionally expanded due to the high melt viscosity. After reducing the die gap, the molecules in the film have better orientation and improve the quality of the film.

(5) In processing LDPE/LLDPE blend films, the addition ratio of LLDPE can be increased, the tensile strength of the films can be improved and the production cost can be reduced.

(6) Reduce the extrusion pressure during plastic processing, reduce energy consumption, reduce mechanical wear, and reduce the comprehensive cost of film processing. Under the same product quality and energy consumption conditions, the production efficiency can be improved by 30-60%.

(7) Improve the surface finish of the film, without affecting the transparency, transmittance and haze of the product, improve the tensile strength of the product, and improve the product quality.

(8) It is helpful to improve processing conditions for resins that need to reduce processing temperature or are sensitive to temperature.

(9) It is easy to remove impurities in the screw and barrel, shorten the effective time of color switching, and can be used as screw cleaning material.

(10) Fluoropolymer processing aids exist in polymer materials as dispersed spherical small particles. The size of small particles is related to the dispersion effect during processing. The better the dispersion effect is, the better the application effect is. The better the particle diameter of zui is 1-2 um.

After processing, the fluoropolymer will not stay on the surface of the extrusion, will not spray frost on the film surface, will not affect the printing performance of the film surface, and will not affect other properties of the film surface (thermal viscosity, heat sealing, surface tension, static friction coefficient, dynamic friction coefficient).

3. Action mechanism of fluoropolymer

Fluoropolymer processing aids take advantage of the low surface energy of fluoropolymer compounds. During processing, the fluoropolymer moves toward the melt surface and attaches to the metal surface of the screw and barrel, forming a layer of "lubricating" coating. The polymer "lubricating" coating is dynamically balanced. It takes a certain time for the coating to form and reach a stable state, about one hour. After reaching the balance, it can obviously show the changes of plastic processing parameters such as the back pressure of the extruder, torque and the decline of the apparent viscosity of the melt. The amount of polymer processing aids used is 200-1000mg/kg. If a higher concentration of additives is used in the initial stage of processing, the processing state can be stabilized faster.

4. Current situation of fluoropolymer processing aids abroad

Dynamar PPA is a kind of additive based on fluoropolymer produced by American companies. It can improve the processing performance of polymers. It has been widely used in the plastic processing industry and is suitable for the extrusion process of a variety of resins.

Dynamar PPA is a series of polymer processing aids with different brands to meet the processing needs of a variety of polyolefin resins. It is used in processing processes such as blown film, coating, tape casting extrusion, pipe extrusion, sheet extrusion, wire drawing, cable coating extrusion, bottle blowing, etc. It can be used to improve the processing of polyethylene, such as: mLLDPE, LLDPE, MDPE, HDPE, HMW-HDPE, LDPE, VLDPE, EVA, PP, PVC and other polyolefins; It can also be used for the processing of PS, PA, PET, ABS and other engineering plastics. At the same time, Dynamar PPA polymer processing aids can also be used for the processing of PS, PA, PET, ABS and other engineering plastics. At the same time, Dynamar PPA polymer processing aids can also be used for masterbatch manufacturing and raw material blending processes. The proper addition of fluoropolymer can improve the performance of plastic products. The use of fluoropolymer Dynamar PPA in plastic extrusion processing can improve the production capacity of equipment, reduce energy consumption, improve quality, and broaden the range of raw materials selection. Dynamar PPA meets the requirements of the Food and Drug Administration for polyolefin application of food contact products (the high dosage of zui is 2000mg/kg). The general dosage of processing aids for Dynamar PPA is 400-1000mg/kg, Usually, 2-5% masterbatch containing Dynamar PPA processing aids is added to the resin.

There are many kinds and brands of fluoropolymer processing aids. 3M Company of the United States provides several brands of Dynamar PPA. Although they are based on similar mechanisms, each of them is specially designed for different coordination systems. The brands of the additives produced and the types of resins applicable to them are shown in Table 1.

Dynamar PPA can be used in the production of polypropylene, including BOPP and CPP film, to improve the quality of film products, improve the transparency of film products, make the thickness more uniform, and also improve the glossiness of BOPP film.

For polypropylene, FX-5911 and FX9613 can be selected to eliminate die buildup, and FX5911 can be selected to facilitate pigment dispersion. FX-5911 can be selected for BOPP film and PP wire drawing, BOPP film, CPP film, PP-R and PP-B pipes. FX5911 is a 100% fluoropolymer with good thermal stability and does not decompose during extrusion processing. Fluoropolymer additives can reduce or eliminate die buildup and reduce downtime. Die buildup can occur in film blowing, casting film, wire and cable and profile extrusion. FX-5911 can avoid material retention and accumulation in the die mouth. If FX-5911 is used for PP fiber, the waste rate can be reduced from 5% to 1%.

Special plastic manufacturers