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Thermoforming — Factors Affecting Transparency of Polypropylene Thermoformed Products

In the PP polypropylene extrusion sheet, thermoforming and plastic products production process, often customers have found that the production of products is not transparent, no other people do the translucent. Thermoforming is a very complex molding process for plastic products. There are many factors that affect the transparency of the product.

Simply list some of the factors affecting the transparency of PP thermoformed products, hoping to provide more help to the quality improvement and quality management of the product manufacturers, but also to provide some guidance to the product manufacturers in product design and equipment selection.

Ingredients and Formulations:

PP material  pp sheet  pp Blister material

1. Effect of homopolypropylene raw materials

Raw materials for polypropylene sheets and thermoformed articles are generally low-melting, homogenized PP raw materials, including commonly used T30S (T03H), L5E89, S1003 and the like. However, different manufacturers of drawing PP raw material isothereal control is not the same, resulting in raw materials, transparency and rigidity is not the same, thus affecting the transparency of the product. Equivalent low PP raw materials are usually more transparent, but at the same time will be softer.

2. Random copolymer high transparent PP raw materials

Random copolymer High transparent PP raw materials due to a certain degree of ethylene copolymerization, so itself has a very high transparency and gloss, a certain customer will mix in the formula homopolymer PP raw materials and high transparent PP raw materials to improve product transparency Sex and gloss, to prepare high transparent cups. Different manufacturers of random copolymer high transparent PP raw material itself ethylene content and the type and content of transparent agents are different, so with different high transparent PP raw materials and homopolymer PP mixed product transparency and gloss will also be affected.

3. Effect of toughening agent

In PP thermoforming and blistering products, more customers will add toughening agents to reduce the rate of broken cups, or to improve the low temperature storage performance, currently applicable to PP low temperature toughening toughening agents are many (PE / ICP US / POE), but there are quite a number of toughening agents that affect transparency. Especially in the high temperature requirements of high, toughening agent added a relatively high situation, then you need to select the appropriate toughening products, in order to avoid the transparency of the product have a negative impact.

4. Selection of transparent and transparent masterbatch

There are a lot of polypropylene transparency on the market, each of the transparency and the effect of the price difference, including the ease of dispersion and the appropriate amount of added, as well as the effect of increasing the difference. At the same time because the extrusion sheet machine is usually a single screw extruder, so the shear and dispersion capacity is not strong, the use of powder transparent agent, may not be dispersed. Affect the ultimate transparency of the product. In the preparation of high transparency and high gloss of the thermoformed products, the need to select the appropriate transparent agent and transparent masterbatch.

The impact of the production process:

1. Extrusion temperature effect

The temperature setting of the sheet extrusion will have an effect on the crystallization behavior of the PP product and the surface defects of the sheet and also affect the dispersion of the toughening agent, the transparency agent and other components in the sheet, The transparency of the material and the transparency of the final product.

2. The effect of extrusion speed

The effect of the extrusion speed on the sheet and the product is similar to the effect of the extrusion temperature, which also affects the dispersibility of the other components and the crystallization behavior and surface defects of the PP sheet, thereby affecting the transparency of the final product. Extrusion rate is too high, then the three-roll cooling can not keep up, resulting in increased crystallinity of PP sheet, sheet transparency decreased. At the same time, the extrusion rate is too high will easily appear on the surface of the PP sheet pits, these pitting will continue to remain on the surface of the product, thus affecting the transparency of the product.

3. Three roller cooling effect

The temperature setting of the three rolls mainly affects the crystallization behavior of the PP sheet, thus affecting the transparency of the product. The high temperature of the three rolls is high, and the PP sheet has high crystallinity and easy to form large crystals, thus reducing the transparency.

4. The effect of hot forming temperature

The thermoforming temperature will also have a certain effect on the transparency of the final PP thermoformed product. It is necessary to achieve a fogging, product transparency and glossiness in a reasonable range. The temperature is too low leading to product formation dissatisfaction. PP molding temperature range is very narrow, only a few degrees range.

Impact of mold and tension head:

Blister mold   High frequency mold   Thermoforming molds  

1. The effect of the head

The drawing head material has a very important role in the thermoformed article. The material selection of the drawing head, the design of the shape and the surface finish will have an effect on the distribution of the wall thickness of the product, the height and depth of the drawn pattern, The transparency of the impact.

2. The effect of mold

The design, polishing and cooling of the mold will affect the finish of the PP product surface, as well as the crystallization of the PP material, thereby affecting the transparency and brightness of the end product.

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