Transparent thermoplastics are amorphous, but not all amorphous thermoplastics are transparent, as is the case with amorphous plastics that have been tinted and modified. Due to the orderly arrangement of molecular chains, partially crystalline thermoplastics are no longer transparent, and their degree of transparency will differ depending on the degree of crystallinity.

In practical production, if all these factors are taken into account, the following problems will occur: The sheet will not be produced because the vacuum forming machine cannot reach the required vacuum forming temperature (when passing the machine Can not get a smooth and flat surface), or the material's melt strength is too low, it will produce too much collapse, or because the material and the die bond too tight.

The single-layer or multi-layer composite sheet used for molding processing must have the following properties:

1, hot stretching, that is, the sheet can be stretched when heated, this feature has a great influence on the shape and quality of the product. Some can stretch 15% to 20%, and some can even stretch to 500% to 600%.

2. The heat strength, ie the sheet that is heated and softened, will form a clear outline on the mold as long as it is under slight pressure. Conversely, if too much pressure is needed to shape, the difference in pour pressure provided by vacuum forming is limited, and it is difficult to show certain subtle patterns.

3, plastic memory, that is when stretching the softened sheet, both the tendency to tighten the resistance to pull, but also the tendency to stretch as uniform as possible. This feature allows the molded article to revert to its original plate shape if it is reheated to the original molding temperature. This characteristic has an important influence on the stretching of the forming process.

4, molding temperature, that is, the forming sheet must have a suitable range of processing temperature. It is easy to mold at its heat-softening temperature, and has a certain distance from its melting temperature. The molding temperature range is wider; it can not be formed only in a relatively small specific temperature range. When the temperature is high or low, the molding is easy to tear. , Collapse and other phenomena.