How to melt and reshape plastic?

1, Types and selection of plastics
Firstly, understanding the type of plastic is the foundation of the melting and reshaping process. Plastics are mainly divided into two categories: thermoplastic plastics and thermosetting plastics.
Thermoplastic: This type of plastic can soften and reshape after heating, and return to a solid state after cooling. Common thermoplastic materials include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). They are widely used in fields such as packaging, construction, automotive, and electronic products.
Thermosetting plastics: Unlike thermoplastic plastics, thermosetting plastics undergo chemical reactions upon heating, forming cross-linked structures. Once cured, they cannot be reshaped by heating. Common thermosetting plastics include phenolic resin, epoxy resin, and unsaturated polyester. This type of plastic is mainly used to manufacture products that require high strength and heat resistance, such as electrical insulation materials, automotive components, and molds.
When melting and reshaping, thermoplastic should be chosen because thermosetting plastics cannot be reshaped once cured.
2, Methods for melting plastics
There are various methods for melting plastic, mainly depending on the type of plastic and the desired reshaping shape. Here are several common melting methods:
Extrusion method: This is one of the most commonly used plastic melting methods. By feeding plastic particles or powder into an extruder, under the action of heating and shear force, the plastic is melted and extruded into continuous profiles, such as pipes, wire sheaths, etc.
Injection molding method: The injection molding machine heats and melts plastic particles, then injects them into the mold under high pressure, and after cooling, forms the desired shape of plastic products. This method is suitable for manufacturing components with complex shapes and precise dimensions.
Blow molding method: Melt plastic is squeezed into a blow molding mold, and then air is blown into the mold to cause the plastic to expand and adhere to the inner wall of the mold. After cooling, hollow plastic products such as bottles, barrels, etc. are obtained.
Hot pressing method: Heat a plastic sheet or film to a softened state, then place it on a mold, apply pressure to make it adhere to the mold and cure. This method is commonly used for manufacturing boards, sheets, and films.
3, Steps to Reshape Plastic
The process of reshaping plastics includes steps such as preparing materials, melting plastics, forming, and cooling and solidifying. Here is a basic process for reshaping plastics:
Preparation materials: Select thermoplastic suitable for reshaping and ensure that it is clean and free of impurities. If the plastic particles are large, they can be crushed into smaller particles for easier melting.
Melting plastic: Heat the plastic to a molten state according to the selected melting method. During the heating process, it is necessary to control the heating temperature and time to avoid plastic decomposition or the production of harmful substances.
Molding: Injecting melted plastic into a mold, applying pressure or blowing air to make it adhere to the inner wall of the mold and solidify. During the molding process, it is necessary to ensure the accuracy and temperature control of the mold to obtain the desired shape and size.
Cooling and solidification: After the plastic has cooled and solidified in the mold, remove it from the mold. During the removal process, be careful to avoid damaging the plastic products.
4, Precautions and safety measures
During the process of melting and reshaping plastics, the following safety precautions should be taken into account:
Control heating temperature: The heating temperature should be controlled above the melting point of the plastic, but avoid excessive temperature that may cause plastic decomposition.
Fire prevention: Due to the possibility of combustible gases being generated during the heating process of plastics, fire extinguishing equipment should be equipped in the work area and open flames and high-temperature sources should be avoided.
Good ventilation: When melting plastic, harmful gases and smoke are generated, so it is necessary to maintain good ventilation in the work area to reduce the harm to operators.
Personal protection: Operators should wear appropriate personal protective equipment, such as goggles, masks, gloves, and fire-resistant clothing, to reduce harm to the skin and respiratory system.
Waste disposal: The waste generated during the melting and reshaping process should be properly disposed of to avoid polluting the environment.