Plastic products are the most widely used category in current society, and they cannot be separated from the participation of plastics in public consumption, industry, agriculture, household appliances, public service construction, and military industry. Designers often spend a lot of time choosing the right plastic materials. In order to save designers' time, based on my years of experience in plastic product design, I summarize how to quickly select product materials. I hope it will be helpful for personnel engaged in certain industries.

1、 Select based on the main purpose of the product

1. Based on the environment

The usage environment refers to the temperature, humidity, medium, etc. that a material or product undergoes when used. The temperature and humidity conditions are determined by the surrounding contact medium. In addition, natural exposure is also influenced by factors such as exposure to sunlight and the presence of chemical substances, in addition to wind, rain, and fog. Therefore, it is necessary to consider the environmental adaptation of plastics.

2. According to the stress type and Mode of action of plastic products

Under the action of force, products inevitably undergo deformation, mainly manifested as stretching, compression, bending, twisting, shearing, impact, or a combination of several forces. In addition, if the external force is an impact force and there is additional work for the production, plastic with high impact strength must be selected; If it is static, materials with low creep should be selected; If it is the repeated deformation force of plastic, only materials with good fatigue strength can be selected.

3. Based on the object of use

There are differences in quality standards, environmental directives, aesthetic concepts, and interests among different regions, countries, and races. When selecting plastic, it should comply with the requirements of the product sales area.

2、 Select materials based on the usage situation of plastic products

1. Production of plastic products for shells, boxes, covers, and pipes

This type of plastic product should not bear large external forces, and has excellent impact strength, hardness, suitable tensile strength, dimensional stability, and product suitability for external environment acidity and alkalinity. In situations where some metals cannot be used, plastic can be used as an optimal choice. The following situations are more suitable for using plastic.

a. It is necessary to prevent resonance and require low sound transmission;

b. Require elastic deformation to prevent dents caused by accidental collisions;

c. The shape of the product is complex, and it is difficult to produce using metal processing technology;

d. The product does not want to be processed afterwards;

e. Require overall electrical insulation (or partial insulation) and insulation of the product, or overall coloring or transparency or translucency;

f. Require corrosion resistance, moisture resistance, and non rusting;

Based on the above application situations, sometimes only one material cannot meet all the requirements, plastic and other materials can be considered for composite processing, such as embedding threaded metal inserts into plastic parts, which is a typical application; If the product shell is required to withstand collision situations, it is necessary to consider using metal and plastic composite plates, or plastic composite plates can be used on the metal surface.

2. Plastic Selection for Low Friction Coefficient Applications

The materials used in this type of application require a low coefficient of friction, even when there is no external lubrication, the coefficient of friction is quite low, the wear and corrosion resistance is good, and it also has good shape stability, heat resistance, and corrosion resistance. In the past, copper antimony tin alloy, bronze, cast iron, pre lubricated wood, graphite, etc. were commonly used. It is better to use plastic in the following situations.

a. Places with corrosion and wear;

b. Lubricating oil can contaminate the product during production;

c. No maintenance operations required;

d. Using plastic materials can avoid complex lubrication systems;

e. The quality requirements are very light;

f. When the electrical insulation is high;

g. Do not make abnormal noises while working;

h. There should be no scratches or scratches;

i. When the slippery viscosity is not suitable.

3. Selection of plastic materials for heavy stress Machine element

This type of component requires high mechanical strength, strong bending resistance, high tensile and impact strength, and still has good fatigue resistance and stability at higher temperatures; In the past, materials such as cast iron and brass were generally used. When encountering the following situations and requirements, it is more appropriate to consider using plastic.

a. Light quality requirements;

b. Workplace environments with high levels of dust, wear and corrosion;

c. There should be no abnormal noise or vibration;

d. Good overall efficiency.

4. Selection of Plastic Parts Materials for Chemical Equipment

This type of situation requires materials to be resistant to chemical corrosion and have mechanical strength. Previously, stainless steel metal was used. If there are the following situations and requirements, plastic may be considered more suitable.

a. Special requirements for corrosion resistance, and stainless steel cannot meet the requirements;

b. Resistant to both corrosion and wear;

d. Less maintenance, easy to repair;

e. Require thermal insulation, insulation, and resistance to instantaneous high temperatures or erosion;

5. Selection of Plastic Materials for Electrical Parts

This type of application requires materials to have excellent electrical insulation at intermediate frequencies, high strength and impact resistance, good fatigue and heat resistance, and good dimensional stability at elevated temperatures. In the past, ceramics, glass, or mica were used, but when encountering the following situations and requirements, it is more appropriate to consider using plastic.

a. There is an impact load present;

b. Low quality requirements;

c. High dimensional accuracy is required, and the processing of inorganic insulation materials such as ceramics and glass cannot meet the required time requirements;

d. A product or component composed of conductors and insulators with complex shapes that form a whole;

To sum up, polyester, fluoroplastics, polyphenylene ether, polysulfone, polyimide, polyamide Imide Phenol ether resin (xylok new phenol ether resin and Parylene are better insulation materials. If it is a general insulation material, polyethylene, polypropylene, polystyrene and polyvinyl chloride can also be used to manufacture general wire and cable insulation. The wire wrapping material of composite electrical components can be used with silicone rubber and epoxy composite seal to obtain better performance; melamine formaldehyde plastic can be used for parts with higher hardness; silicone polymer can be used for high temperature resistance The occasion; Amino plastics can be used in low-priced situations; Phenolic laminated materials are used for punching and die stamping parts.

6. Materials used as transparent parts

Lamina lucida and model parts shall have good light transmittance, excellent secondary formability and molding processability, not easy to crush, and good tensile strength. In the past, glass was mostly used, but it has some drawbacks, especially the inability to meet the following usage requirements:

a. The product requires resistance to impact, vibration, and not easily broken;

b. Having flexibility;

c. Higher specific strength;

d. The material must be semi transparent and should not be achieved through surface treatment;

e. Require products with complex shapes that are easy to shape;

Based on the above description, acrylic plastics are recommended for general applications, especially for optical, decorative, and outdoor applications. The cast acrylic cheese sheet material has high strength and transparency, and can be used to manufacture medium and low precision lenses. The acrylic plastic used for extrusion molding has a lower price and good secondary formability; Polycarbonate has high strength in transparent plastic and can be used to make transparent masks, protective glasses, or protective plates. Acetate butyrate fiber has good impact resistance and deep drawing formability; Transparent polyvinyl chloride has excellent secondary formability and printing adaptability; Acetic acid fiber plastic can be used as flexible Lamina lucida and protective board; Polystyrene and rigid polyvinyl chloride plastics with moderate impact resistance are low-cost transparent materials; Low cost molded transparent components made of polystyrene. Allyl group Diethylene glycol ester resin is the main thermosetting plastic used in optics at present. Its transparency, abrasion resistance, impact resistance and chemical resistance are quite good. If the surface is coated with organic silicone film, the plastic surface hardness and abrasion resistance can be improved. It can work at about 100 ℃, and the short-term working temperature can reach 150 ℃. At present, it is mainly used to make lenses. If the product is required to have good chemical resistance and adapt to high working temperatures, or if there is wear under working conditions, and good dimensional stability is required over a large temperature range, surface treatment of the plastic must be carried out.