Firstly, let's introduce the meaning of flow film. Flow film is a non stretch, non oriented flat extruded film produced by rapid heating of molten saliva through a flow film machine. There are two methods: single-layer flow film and multi-layer co extrusion flow film. Compared with blown film, its characteristics are slow production speed, low yield, and excellent transparency, gloss, and thickness uniformity of the polymer. But do we know the importance of resin selection in the production of cast film when leaving ink marks? What kind of resin should we choose?
(1) The first step is the selection of resin varieties
The selection of resin varieties is basically based on whether the desired cast film can be produced. The resin should be selected from the variety with the closest performance to the modification purpose, in order to save the amount of additives added. For wear-resistant modification, the resin should first consider selecting three small wear-resistant resins PA, POM, and UHMWPE; Once again, for uniform modification, the resin should first consider selecting the three small uniform resins PS, PMMA, and PC.
(2) Next is the selection of resin grades
Many manufacturers do not attach great importance to this when making cast film. The grades of the same resin may vary, and their performance differences are also very small. Therefore, the grade with the closest performance to the modification purpose should be selected. If heat-resistant modified PP is used, it can be selected within the range of PP grades with a heat deformation temperature of 100-140 ℃. We should choose PP grades that are inherently resistant to 140 ℃, such as PP-4012 from Xiaohan Oil Chemical.
(3) Once again, it is the choice of resin fluidity
This step is relatively abstract and can only be experienced after trying, without a clear standard. The viscosity of various plasticizing materials in the formula should be close to ensure processing fluidity. For materials with significantly different viscosities, transition materials should be added to reduce the viscosity gradient. PA6 is often added as a transition material in PA66 toughening and flame retardant formulations, while HDPE is often added as a transition material in PA6 toughening and flame retardant formulations.
Different processing methods require varying levels of fluidity.
Different types of plastics have varying levels of fluidity. From now on, plastics are divided into low flowability plastics, high flowability plastics, and non flowability plastics, as follows:
Low liquidity plastics - PS, HIPS, ABS, PE, PP, PA, etc.
High liquidity plastics - PC, MPPO, PPS, etc.
Absolutely non liquid plastics - polytetrafluoroethylene, UHMWPE, PPO, etc.
The same type of plastic also has different flowability, mainly due to differences in molecular weight and molecular chain distribution. Therefore, the same raw material is divided into different grades. The flowability required for different processing methods varies, so the grades are divided into injection grade, extrusion grade, blow molding grade, rolling grade, etc.
Different modification purposes require different flowability, such as poor flowability for high filling requirements, such as magnetic plastics, filling materials, halogen-free flame-retardant cable materials, etc.
(4) Ultimately, it is the resin's selectivity towards additives
The literal meaning of the additive is as the name suggests, it is a catalyst that promotes the smooth shaping of the cast film. PPS must not contain lead and copper additives, and PC must not use antimony trioxide, both of which can lead to depolymerization. In addition, the acidity and alkalinity of the additives should be the same as that of the resin, otherwise there will be a reaction between the two, and the consequences will be very serious
Casting film machine can be used to produce plastic films such as PE, CPE, EVA, as well as transparent films, embossed films (patterns can be customized according to customer samples), optical films, etc.
Properties of cast film: It is not hard or brittle at low temperatures, and does not become sticky at high temperatures of 45 ℃. It has a poor hand feel, is lightweight, non-toxic, and has no irritating odor. After use, it has high environmental pollution.
The application of thin film is widespread: it can be used as a base film for hygiene products, such as sanitary napkins and diapers; Daily necessities such as disposable gloves, shoe covers, shower caps, sleeves, aprons, surgical gowns, cleaning gowns, tablecloths, umbrellas, shower curtains, etc. With lining film, packaging film, and usually perforated film bottom film and various film rolls.
