How to choose the plastic material suitable for injection molding of electronic equipment shell?
The selection of plastic materials suitable for injection molding of electronic equipment housings requires comprehensive consideration of many factors. The following are some key points:
mechanical character
Strength and toughness: electronic equipment may be subjected to external forces such as collision and extrusion in daily use, so the shell material needs to have sufficient strength and toughness to prevent cracking or damage. For example, ABS plastic has high mechanical strength and good toughness, can withstand a certain degree of impact, and is widely used in computer cases, TV housings and other products; Polycarbonate (PC) is also excellent in strength and toughness, and is often used in electronic equipment casings with high strength requirements, such as notebook computer casings.
Stiffness: If the shell of electronic equipment needs to maintain good shape stability, such as the shell of some precision instruments, you need to choose materials with good rigidity. For example, polystyrene (PS) has high rigidity but high brittleness, so its toughness can be improved by modification, and it can be used in some shell parts with high requirements for shape retention and less stress.
Abrasion resistance: The abrasion resistance of materials is particularly important for some electronic equipment shells that often rub against other objects, such as mice and keyboards. Polyoxymethylene (POM) has excellent wear resistance and self-lubricity, and is one of the ideal materials for manufacturing this kind of shell.
hot property
Heat resistance: Electronic equipment will generate heat in the working process, and the shell material needs to be able to maintain stable performance within a certain temperature range without deformation and softening. PC has good heat resistance, and its thermal deformation temperature can reach about 120℃, so it is suitable for some high-heat electronic equipment housings, such as power adapter housings. The heat resistance of polypropylene (PP) is relatively poor, but after modification, it can also meet the requirements of some electronic equipment with low heat resistance.
Thermal stability: In the process of injection molding, materials need to have good thermal stability to ensure that there will be no decomposition, discoloration and other problems at high temperature, which will affect the quality of products. For example, some high-performance engineering plastics, such as PEEK, have excellent thermal stability, but the cost is high. They are generally used in high-end electronic equipment or special parts that require high thermal stability.
Coefficient of thermal expansion: The coefficient of thermal expansion of the material should match other components inside the electronic equipment, otherwise there may be problems in the cooperation between the shell and the internal components when the temperature changes, such as gaps or stress concentration. Generally speaking, the thermal expansion coefficient of thermoplastics is relatively large, so it is necessary to consider this factor in the design, and reduce the influence of thermal expansion through reasonable structural design or selecting suitable material combination.
behaviour of electricity
Insulation performance: in order to ensure the safety of electronic equipment and prevent electric shock accidents, the shell material needs to have good insulation performance. Most plastic materials have certain insulating properties, but the insulating properties of different materials are different. For example, polyethylene (PE), polystyrene (PS) and other materials have excellent electrical insulation properties, and are often used to make insulation layers of wires and cables and some electronic equipment housings with high insulation requirements.
Electromagnetic shielding performance: For some electronic devices that need to be shielded from electromagnetic interference or external electromagnetic radiation, such as mobile phones and computers, the shell materials need to have certain electromagnetic shielding performance. You can choose plastic materials with conductive fillers, such as adding metal fibers and carbon fibers to ABS or PC, or using alloy materials with electromagnetic shielding function to make the shell.
chemical properties
Corrosion resistance: When electronic equipment is used in different environments, it may come into contact with various chemicals, such as sweat, detergents, organic solvents, etc., so the shell material needs to have certain corrosion resistance to prevent the material from being corroded and affecting its appearance and performance. Nylon (PA) has good corrosion resistance, and can be used in some electronic equipment casings that may come into contact with chemicals.
Weather resistance: If electronic equipment needs to be used outdoors or in harsh environmental conditions, the weather resistance of the shell material is very important. Some plastic materials, such as PP and PE, are prone to aging, discoloration and embrittlement under long-term exposure to ultraviolet rays, oxygen and other environmental factors, while materials such as PC and ABS have relatively good weather resistance, but their weather resistance can be further improved by adding additives such as antioxidants and light stabilizers.
presentation quality
Glossy: If the shell of electronic equipment needs to have high glossiness to achieve beautiful effect, then materials with good glossiness such as ABS and PC can be selected. After proper surface treatment, ABS material can obtain high gloss, and it is often used to manufacture some small household appliance shells and electronic product shells with high appearance requirements.
Color and dyeability: Different electronic devices may need different color housings to meet the needs of personalization or brand recognition. Some plastic materials, such as ABS and PP, have good dyeability, and various colors can be obtained by adding color masterbatch or surface spraying. The PC material itself has certain transparency, and the color effect can also be achieved by adding pigments.
Surface hardness: in order to prevent the surface of the shell from being scratched and worn, it is necessary to choose materials with higher surface hardness. The surface hardness of PC material is relatively high, but it is easy to scratch, while some hardened plastic materials or composite materials with wear-resistant fillers can provide better surface hardness and wear resistance.
processability
Liquidity: the fluidity of materials directly affects the difficulty of injection molding and the quality of products. Materials with good fluidity can easily fill the mold cavity and obtain a complete and compact product, but it may also lead to problems such as flash. PP has good fluidity and is suitable for manufacturing some complex and thin-walled electronic equipment shells. The fluidity of PC is relatively poor, so it needs high injection pressure and temperature to ensure its good filling effect.
Shrinkage rate: Plastic materials will shrink to some extent after injection molding, and the shrinkage rate of different materials is different. If the shrinkage rate is too large, it may lead to product size instability, deformation or warping and other defects. Therefore, the shrinkage rate should be considered when selecting materials, and the dimensional accuracy of products should be controlled through reasonable mold design and adjustment of injection process parameters. For example, the shrinkage of POM is large, so special attention should be paid to controlling its shrinkage deformation during injection molding.
Machinability: The material should be easy for injection molding, cutting, drilling, welding and other processing operations to meet different production process requirements. Some plastic materials, such as ABS and PP, have good machinability, can adapt to various processing methods and improve production efficiency and product quality.
Cost factor
Material cost: The prices of different plastic materials are quite different, so when selecting materials, it is necessary to comprehensively consider factors such as market positioning and cost budget of electronic equipment. Generally speaking, the prices of general plastics such as PP and PE are relatively low, while the prices of engineering plastics such as PC, PA and PBT are higher, but their performance is also more excellent. On the premise of meeting the product performance requirements, we should try to choose lower-cost materials to reduce production costs.
Processing cost: The processing cost of materials also needs to be taken into account, including the technological difficulty of injection molding, the service life of the mold, production efficiency and other factors. Some materials with good fluidity and simple molding process can reduce the difficulty and cost of injection molding and improve production efficiency; However, some high-performance materials may need special processing technology or equipment, which increases the processing cost. In addition, the recyclability of materials will also affect the cost. If materials can be recycled easily, the production cost and the impact on the environment can be reduced.
