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Bubble Problem In PVC Transparent Sheet And Its Solution
- Sep 09, 2018 -

    The problem of bubbles in PVC transparent sheets is believed to be a problem in many companies. Tongxiang juli plastic tells you how to solve it.

1. Brief description of the problem

   The test uses PVC QS-1000F resin to produce unidirectional heat shrinkable film. There are tiny bubble marks in the transparent film. These bubble marks reduce the thickness of the film, and the film will change abnormally in image color due to uneven application of ink. , affecting the quality of the film.

2, problem analysis

    After communicating with the company's technical staff, it was initially determined that bubbles appeared in the sheet due to more volatile components in the material. The company reported that this problem occurred in August. Due to the high amount of rain and the high humidity of the air, the resin or additives used in the company's production may be damp and the moisture content is high.

    At the site, 1 batch of material (about 100 kg) was mixed according to the production process provided by the company. When the mixing temperature was 80-100e, the amount of volatile materials increased significantly, and it was white mist and water vapor above the mixer. The blending material was again subjected to a blown film test on the extrusion blown film apparatus of the unit, and the produced film did have many small bubbles.

3 Solutions

    The mixing process adjustment test was carried out at the production site, and the mixing method of high and low speed mixing was adopted appropriately to prolong the mixing time and increase the discharge temperature to fully discharge the moisture in the material. The process conditions for the specific changes are shown in Table 1.

    After adjusting the mixing process, the volatile matter in the material is fully discharged due to the prolonged mixing time of the temperature range of 80 to 125 °C. After the film was blown on site, it was found that the small bubbles in the film were significantly reduced, which could meet the quality requirements of the product.

    When the water content of the raw material is high and cannot meet the production, the method of replacing the raw materials or prolonging the mixing time of the materials to discharge the volatile matter may be adopted; since some additives (such as lubricants) have poor quality and high volatile content, the production is in progress. The use of such raw materials should be avoided. It is recommended to use additives produced by large companies. Although the price is higher, the quality is stable.