Glossiness refers to the ability of the surface of plastic film to reflect incident light specularly;
Transparency refers to the scattering or absorption loss of plastic film to incident light. High transparency means that the scattering or absorption loss of incident light is small;
Haze is the percentage of the transmitted light intensity which deviates from the incident light by more than 2.5 ° to the total transmitted light intensity. The higher the haze, the lower the gloss and transparency of the film, especially the imaging degree
Since the advent of plastic film, optical properties such as surface gloss and transparency are an important aspect of its performance, especially in the packaging field where plastic film is most widely used. High surface gloss and high transparency are its important indicators. Therefore, how to reduce or eliminate the haze of plastic film has been widely concerned since the advent of plastic film. However, with the change of people's aesthetic concept, the surface characteristics of packaging materials show a variety of requirements, surface matte (dull) packaging (with high haze and low gloss) also began to be popular With the capacity saturation of BOPP (biaxially oriented polypropylene) and other high gloss and high transparent packaging products and the intensified market competition, the development of Matt film has become a new profit growth point and investment hot spot of this kind of film manufacturing enterprises. Therefore, the influencing factors and mechanism of plastic film haze are further concerned.
There are two main factors affecting the haze of plastic film: one is raw materials, such as resin category, resin parameters and additives; the other is processing conditions, such as different processing technology, different processing conditions under the same processing technology, etc
Influence of raw materials on haze
Resin factors include the type of resin, melt index (MI), the relative molecular weight (MT) and its distribution (MWD), the regularity and branching of the main chain, etc., which affect the crystallinity or melt elasticity of the resin, and finally affect the haze of the film.
When the MI of LDPE is 1-5 g / 10 min, the haze is the best, and the extinction (haze) effect is the best when the MI of LDPE is 0.2-0.5
Good. For HDPE, LLDPE and LDPE, the haze of HDPE is the highest under the same processing conditions and the resin MI is about 1.0. MWD can also affect the haze property of the film, and the width of MWD will lead to the thin resin
The reason is that the surface of the material is not regular. The more regular the main chain and the less or shorter the branched chain, the higher the crystallinity and the greater the haze.
2 Effect of additives
The haze of the film increases with the addition of anti adhesion agent SiO2, which is due to the small particle size of SiO2 uniformly dispersed in the resin, which improves the dispersion of visible light.
Nucleating agent and nucleating agent are easy to disperse evenly in the resin. The crystallization process gives full play to the heterogeneous crystallization effect, effectively increases the density of the crystal nucleus, promotes the uniform distribution of the crystal nucleus, resulting in the refinement of the grain size, and the reduction of the light scattering and light reflection effect of the film surface. As a result, the haze is reduced and the transparency is improved significantly.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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