The particle size distribution of blown film masterbatch has a crucial impact on the uniformity of the film in the film blowing process. In-depth exploration of the relationship between the two will help improve the quality of blown film products.
First, the particle size distribution directly affects the dispersibility of the masterbatch in the plastic matrix. If the masterbatch particle size distribution is narrow and uniform, the masterbatch can be more evenly dispersed in the plastic melt during the film blowing process. For example, masterbatches of similar sizes are more likely to form a stable dispersion system under the shearing and mixing action of the screw, so that the performance of the film in the thickness direction and plane direction is more consistent. On the contrary, masterbatches with large particle size differences are prone to large particles agglomerating and small particles over-dispersing, resulting in uneven local properties of the film, such as thickness deviation or mechanical property fluctuations.
Second, uniform particle size distribution helps stabilize the melt flow during the film blowing process. Masterbatches are incorporated into the plastic melt as an additive. When their particle size is uniform, the viscosity and fluidity of the melt are easier to control. During extrusion blown film, the melt can pass through the die head evenly to form a film bubble with uniform thickness. Uneven particle size distribution may cause differences in the flow rate of the melt at the die head, resulting in uneven film bubble thickness, and even cause film bubble rupture in severe cases, affecting the continuity of the blown film and the product qualification rate.
Furthermore, the appropriate particle size distribution can optimize the optical properties of the film. For some films with high transparency requirements, masterbatches with uniform particle sizes can reduce the scattering and refraction of light. Because the microstructure formed by the uniformly distributed masterbatch in the film is relatively regular, light can pass through the film more smoothly, thereby improving the transparency and gloss of the film. On the contrary, masterbatches with uneven particle sizes will destroy the optical uniformity inside the film, causing the film to show an increase in haze and a decrease in gloss.
In addition, from the perspective of the uniformity of the mechanical properties of the film, the blown film masterbatch with a narrow particle size distribution has obvious advantages. In mechanical property tests such as stretching and tearing, masterbatches with uniform dispersion and stable particle size can make the force on all parts of the film uniform. Since the interaction between the masterbatch and the plastic matrix is relatively consistent throughout the film, there will be no local weak points in the mechanical properties of the film, thereby improving the reliability and stability of the film as a whole and meeting the requirements of the mechanical properties of the film in different application scenarios.
Then, in the multi-layer composite blown film structure, the particle size distribution of each layer of blown film masterbatch synergistically affects the overall uniformity of the composite film. If the particle sizes of the masterbatches of different layers can be reasonably matched, they can fit better during the composite process and reduce interlayer stress and defects. For example, the good matching of the particle sizes of the surface and inner layer masterbatches can ensure that the composite film shows excellent uniformity in terms of appearance, barrier properties, and mechanical properties, expanding the application range and functional characteristics of the film.
Finally, in order to obtain the ideal particle size distribution to ensure the uniformity of the film, the screening, grinding, and grading of raw materials need to be strictly controlled during the production process of the blown film masterbatch. At the same time, in the film blowing process, it is also necessary to reasonably adjust the processing parameters such as temperature, screw speed, traction speed, etc. according to the particle size characteristics of the masterbatch, so as to achieve a perfect match between the masterbatch particle size distribution and the film blowing process, and produce high-quality and uniform film blowing products.
