Thermoforming is a plastic processing method developed in recent years. With the improvement of people’s living standards and the change of lifestyle, more and more thermoforming products appear in all aspects of people’s lives. Polypropylene (PP) sheet has the characteristics of low density, non-toxicity, easy processing, warping resistance and good insulation, especially suitable for processing methods such as thermoforming, and is widely used in packaging, automobiles, home appliances and other fields.
Basic principles and characteristics of thermoforming
Thermoforming is a special plastic processing method for processing thermoplastic sheets into various products. After heating the thermoplastic sheet to soften it, use pressure (vacuum or positive pressure) to make the thermoplastic sheet act on the surface of the mold to obtain a shape similar to the profile. After cooling and setting, the desired shape is obtained by trimming. Thermoforming is fast and uniform, with short molding cycle and low mold cost, suitable for automation and long-term production, and is considered to be the lowest and most efficient processing method in plastic molding methods. Thermoforming has developed rapidly since its emergence, especially with the continuous improvement of thermoforming technology and equipment and the intervention of computer simulation methods, thermoforming has become the main processing method that competes with injection and blow molding. In recent years, new progress has been made in thermoforming processing equipment.
The main types of thermoforming are: vacuum forming, pressure forming, plunger-assisted forming and their combinations. There are more and more thermoformed products on the market, such as cups, saucers, food trays, toys, helmets, as well as auto parts, architectural decorations, chemical equipment, etc. Compared with injection molding, thermoforming has the advantages of high production efficiency, low equipment investment and the ability to manufacture products with larger surface areas. The research and development of high-performance PP materials such as high transparency, high melt strength, and low warpage has promoted the application and development of PP sheets in the field of thermoforming.
Application fields of thermoformed PP sheet
- Food Packaging
Food thermoforming PP raw materials are mostly colored PP materials, such as lunch boxes, meat trays, tofu trays, etc. The main colors used are milky white, black, red, etc. Natural PP is mainly used in cups, lids and meat trays; transparent PP is mainly used in cups and lids.
- Non-food packaging
Mainly used in medical capsule blister, tool packaging (stationery, hardware supplies), electronics, cleaning supplies.
- Cut sheets
In the field of cutting sheets, the folding box part consumes the most sheets. PP sheets are used in folding boxes, window packaging and supermarket hanging bars. A small amount of transparent PP is used in high-end folding boxes.
PP sheet for thermoforming food packaging
Thermoforming cups are mainly disposable cups, such as milk tea cups, cold drink cups, fast food cups, etc., which are mainly used in fast food restaurants, milk tea shops, jelly product factories, etc. The raw materials are mainly PP sheets, and some cold drinks are made of PET.
- Heat-resistant lunch box
The general lunch box only holds food with low temperature. But consumers also need to store hot porridge, hot soup, or sterilize it under high-temperature steam. All of these put forward higher requirements for resin raw materials. PET, PS are not resistant to high temperature. PP has good heat resistance, low price and easy availability, so it has become the preferred raw material.
The main products include bowl lids, lunch box lids, cup lids, etc., which are mainly used in fast food restaurants, milk tea shops, cake shops, etc. The lids are mainly transparent, and PP lids are generally used in hot drinks.
- Food lining
The food lining is mainly used for the packaging of biscuits, potato chips, peanuts, and other snacks, and there will be a layer of packaging on the outside, which is mainly used in fast food factories. At present, the food lining is mainly transparent, and there are also milky white and so on. In order to make the packaged food more full and the food is not easy to be crushed, more and more snacks processing enterprises will use food linings.