In the production process of plastic film, the dispersibility of blown film masterbatch is one of the key factors that determine the quality of film products. Good dispersibility can ensure that all kinds of functional additives in the masterbatch are evenly distributed in the film matrix, giving full play to the performance advantages of the masterbatch. Otherwise, it will lead to uneven performance and appearance defects in the film. Therefore, it is of great significance to improve the dispersibility of blown film masterbatch.
First, the selection and processing of raw materials are crucial. If the particle size of the inorganic powder filled in the masterbatch is too large, the particle size distribution is uneven, or the surface is not properly modified, the compatibility of the powder with the resin matrix will be poor, and it will be difficult to disperse evenly. Secondly, the production process parameters have a significant impact on dispersibility. For example, insufficient stirring speed and too short time during mixing will prevent the components from being fully mixed; improper temperature control and unreasonable screw speed during extrusion will affect the plasticization and dispersion effect of the material. In addition, unreasonable masterbatch formula design, such as inappropriate ratio of resin carrier and additive, will also reduce dispersibility.
Surface modification of filled powder is an important means to improve dispersibility. By treating the surface of the powder with coupling agents, surfactants, etc., the surface energy of the powder can be reduced and its affinity with the resin matrix can be enhanced. For example, the use of silane coupling agents to treat calcium carbonate powder can form a layer of organic molecular film on the surface of the powder, making it easier to disperse in the resin. At the same time, strictly screening raw materials, controlling the particle size and particle size distribution of the powder, and selecting raw materials with small particle size and narrow distribution can increase the contact area between the powder and the resin and promote dispersion. In addition, pretreatment of the resin carrier, such as drying to remove moisture, can also help improve the mixing and dispersion effect.
In the mixing process, use efficient mixing equipment, such as high-speed mixers, twin-screw mixers, etc., and set the stirring speed and time reasonably. High-speed mixers can generate strong shear forces to fully mix the materials in a short time; twin-screw mixers can achieve continuous mixing and plasticization of materials through the rotation and shearing of the screw. During the extrusion process, accurately control the temperature and screw speed. Properly increasing the processing temperature can reduce the viscosity of the material, making it easier to flow and disperse; reasonably adjusting the screw speed can not only ensure the full plasticization of the material, but also avoid the degradation of the material due to excessive speed. At the same time, optimizing the screw structure of the extruder, adding shear blocks, mixing elements, etc., can further enhance the dispersion effect of the material.
Selecting a suitable resin carrier is the key. The resin carrier should have good compatibility with the film matrix resin and moderate fluidity. For example, in the production of polyethylene film, choosing low-density polyethylene (LDPE) with good compatibility with polyethylene as the carrier resin can help improve the dispersibility of the masterbatch. In addition, reasonably adjusting the type and amount of additives to avoid excessive additives causing an increase in system viscosity and affecting dispersion. Dispersants and other additives can also be added to reduce the surface tension of the material and improve the dispersibility between the components.
When the dispersibility of the blown film masterbatch is improved, the various properties of the film will be significantly improved. In terms of mechanical properties, uniform dispersion of additives can make the strength, toughness and other indicators of the film more stable, and reduce the problem of film rupture caused by local stress concentration. In terms of optical properties, the surface of the film with good dispersion is flatter and smoother, with higher light transmittance, lower haze, and improved appearance quality. In addition, for films with special functions, such as antistatic film, antibacterial film, etc., the improvement of masterbatch dispersion can ensure that the functional additives can fully play their role, making the functionality of the film more durable and effective.
By optimizing raw material processing, production process and formula design, the dispersion of blown film masterbatch can be effectively improved, thereby improving the quality and performance of film products. In actual production, according to different film requirements and masterbatch characteristics, a variety of methods should be used in combination, and continuous exploration and improvement should be made to achieve the best dispersion effect and film performance.
