Injection molding materials are rich in variety and play a crucial role in plastic products. I am often asked by customers about how to choose injection molding materials for plastic enclosures. Therefore, at the request of customers, we will introduce a selection guide for injection molding materials from two aspects: material types and selection principles for your reference.
Polyethylene (PE): Divided into high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE). It has good low-temperature resistance, chemical stability, and electrical insulation. It has good processing performance and low cost. It is often used in the manufacture of plastic films, pipes, containers, etc., such as plastic bags and plastic bottles in supermarkets.
Polypropylene (PP): It is a crystalline plastic, colorless, odorless, and non-toxic. It has high heat resistance and can be boiled and sterilized at 100°C. It has good fluidity, excellent molding performance, high yield strength, and good electrical performance, but it has poor fire safety and poor weather resistance. It is widely used in automotive parts, home appliance casings, daily necessities, etc., such as automotive interior parts and plastic tableware.
Polystyrene (PS): It is an amorphous polymer, a colorless and transparent granular material with high light transmittance, strong coloring power, and high hardness. However, the product is brittle, prone to internal stress cracking, and has poor heat resistance. It is mainly used in the manufacture of packaging products, disposable medical supplies, toys, electrical components, etc., such as electrical enclosures and foam plastics.
Polyvinyl chloride (PVC): It has good chemical corrosion resistance, flame retardancy, and electrical insulation, but its thermal stability is poor, and stabilizers need to be added during the processing. It can be divided into rigid PVC and soft PVC. Rigid PVC is often used in the manufacture of pipes, door and window profiles, etc., and soft PVC is often used in the manufacture of wire and cable sheaths, films, artificial leather, etc.
Nylon (PA), also known as polyamide, has a high degree of crystallinity. It has high mechanical strength and good toughness. It has high tensile and compressive strength. Its fatigue resistance is outstanding. It is wear-resistant, corrosion-resistant, heat-resistant, non-toxic, and has excellent electrical performance. However, it has poor light resistance, is easy to absorb water, and is not resistant to acids. It is widely used in fields such as automobiles, machinery, and electronics, such as automotive engine parts, gears, bearings, etc.
Polycarbonate (PC), commonly known as "bulletproof glass", is non-toxic, odorless, tasteless, transparent, and flammable, but can self-extinguish after being removed from the fire. It has special toughness and hardness. Among all thermoplastic materials, it has the best impact strength, excellent creep resistance, good dimensional stability, high molding precision, and good heat resistance. It is often used in the manufacture of automotive lamp covers, building doors and windows, optical lenses, electronic and electrical enclosures, etc.
Polyoxymethylene (POM), also known as acetal resin, has a highly crystalline structure and excellent mechanical properties. It has a high elastic modulus, high rigidity and surface hardness, a small friction coefficient, and excellent wear resistance and self-lubricating properties. It is second only to nylon but cheaper than nylon. It has good solvent resistance but is not resistant to strong acids, strong alkalis and oxidants. It is often used in the manufacture of mechanical parts such as gears, bearings, sliders, and valves.
Acrylonitrile-butadiene-styrene copolymer (ABS) is synthesized from three monomers of acrylonitrile, butadiene and styrene. It has high mechanical strength and good comprehensive properties of "firmness, toughness and rigidity". It is easy to process and has stable dimensions. It has good comprehensive physical and mechanical properties. It is widely used in industries such as automobiles, small household appliance enclosure injection molded parts, electronics, and toys, such as automotive shells, household appliance enclosures, toys, etc.
Polyetheretherketone (PEEK): It has extremely high heat resistance, chemical corrosion resistance, mechanical strength and wear resistance. The long-term service temperature can reach 260°C and can be used in harsh environments. It is often used in fields such as aerospace, medical devices, and electronics, such as aircraft parts, artificial joints, and electronic connectors.
Polyphenylene sulfide (PPS): It has excellent high temperature resistance, chemical corrosion resistance, flame retardancy and mechanical properties, and can be used for a long time in high temperature environments above 200°C. It is mainly used in the manufacture of automotive engine parts, electronic and electrical components, chemical pipelines, etc.
Polytetrafluoroethylene (PTFE), commonly known as "the king of plastics", has an extremely low friction coefficient, excellent chemical corrosion resistance, high temperature resistance and electrical insulation, and is almost insoluble in all solvents. It is often used in the manufacture of seals, bearings, pipes, valves, etc., such as the coating of non-stick pans and the lining of chemical pipelines.
Thermoplastic polyurethane (TPU): It has good elasticity, wear resistance, oil resistance and weather resistance, and can be used in the temperature range of -40°C to 120°C. It is widely used in fields such as shoe materials, pipes, films, and automotive parts, such as the soles of sports shoes and automotive fuel pipes.
Styrene-butadiene-styrene block copolymer (SBS): It has good elasticity and processability and can be blended and modified with various plastics. It is often used in the manufacture of rubber products, adhesives, waterproof materials, etc.
Thermoplastic vulcanizate (TPV): It is a dynamically vulcanized thermoplastic elastomer with excellent elasticity, wear resistance, aging resistance and oil resistance, and can be recycled. It is often used in fields such as automotive parts, building seals, wires and cables, etc.
Strength: According to the product's usage scenario and stress conditions, choose materials with sufficient tensile strength, bending strength, compressive strength, etc. For example, for structural parts that bear large external forces, such as automotive parts and mechanical parts, high-strength materials such as nylon (PA) and polycarbonate (PC) need to be selected; while for some daily necessities with low strength requirements, such as plastic containers, ordinary materials such as polyethylene (PE) and polypropylene (PP) can meet the needs.
Toughness: If the product may be subjected to external forces such as impact and collision during use, then the toughness of the material is very important. Materials with good toughness can absorb energy and reduce product breakage and damage. For example, acrylonitrile-butadiene-styrene copolymer (ABS) material has good toughness and is often used in the manufacture of products such as electrical enclosures and toys.
Hardness: For some products that require wear resistance and scratch resistance, such as gears and guide rails, the hardness of the material is a key factor. Polyoxymethylene (POM) has high hardness and good wear resistance and is often used to manufacture these parts.
Heat resistance: If the product is used in a high-temperature environment or needs to undergo high-temperature treatment (such as thermoforming, welding, etc.) during the production process, then the material must have good heat resistance. For example, for parts around the automotive engine, materials that can withstand high temperatures, such as polyphenylene sulfide (PPS) and polyetheretherketone (PEEK), need to be selected; while for products used in low-temperature environments, such as parts of refrigeration equipment, materials with good low-temperature resistance such as polyethylene need to be selected.
Heat deflection temperature: The temperature at which a material deforms under a certain load is also an important indicator for material selection. The higher the heat deflection temperature, the better the dimensional stability of the material at high temperatures. For some products with high dimensional accuracy requirements, such as the enclosures of precision instruments, materials with a higher heat deflection temperature need to be selected.
If the product is used in the electrical and electronic fields, then the electrical properties such as electrical insulation and conductivity of the material need to be considered. For example, for materials used to manufacture the insulation layer of wires and cables, extremely high electrical insulation is required. Commonly used materials include polyvinyl chloride (PVC), polyethylene, etc.; while for some parts that need to conduct electricity, such as grounding plugs for electronic equipment, materials with good conductivity need to be selected, such as carbon fiber reinforced plastics.
1.If the product will come into contact with various chemical substances such as acids, alkalis, organic solvents, etc., then the material must have good chemical corrosion resistance. For example, for products such as pipes and valves used in the chemical industry, materials with strong corrosion resistance such as polytetrafluoroethylene (PTFE) need to be selected.
Surface gloss: Some products have high requirements for surface gloss, such as high-end cosmetic injection packaging and electronic product enclosures. The surface gloss of a material is related to factors such as its molecular structure and additives. When choosing, it needs to be considered according to the product's requirements.
(1)Polymethyl methacrylate (PMMA): Commonly known as plexiglass, it has extremely high transparency, good optical properties, high hardness, and high surface gloss. It can be used to manufacture products such as optical lenses, transparent covers, and display stands.
(2)Polystyrene (PS): It is a transparent plastic with high light transmittance, strong coloring power, and high hardness. However, the product is brittle and prone to internal stress cracking. It is often used in the manufacture of disposable tableware, packaging containers, toys, etc.
(3) PET material, that is, polyethylene terephthalate, is a thermoplastic polyester material that belongs to recyclable materials. The pollution to the environment can be reduced by recycling and reusing. The subsidiary company of our Shibang Group, Chengbang, uses this material for export to Europe and America. Because of its environmental protection and transparency and other characteristics, it is deeply loved by everyone and is widely used in the cosmetics packaging industry.
(1)ABS: Various colors can be adjusted by adding pigments, and it has good color stability and is not easy to fade. It is suitable for products with high color requirements, such as home appliance casings and toys.
(2) Polypropylene (PP): It can also be dyed, but the vividness and stability of the color are relatively poor. However, its cost is low and it can be used for products with not particularly high color requirements.
Fluidity: The fluidity of the material directly affects the filling effect and molding quality of the injection molding process. Materials with good fluidity can more easily fill the mold cavity and reduce the occurrence of injection molding defects. For example, polypropylene (PP) has good fluidity and is often used to manufacture products with complex shapes and thin walls; while the fluidity of polycarbonate is relatively poor, and higher pressure and temperature are required during injection molding.
Shrinkage rate: Materials will shrink after injection molding. The size of the shrinkage rate directly affects the dimensional accuracy of the product. When choosing a material, it is necessary to select a material with an appropriate shrinkage rate according to the dimensional accuracy requirements of the product. Generally speaking, crystalline plastics have a large shrinkage rate, such as polyethylene and polypropylene; while amorphous plastics have a small shrinkage rate, such as ABS and PC.
Drying property: Some materials need to be dried before injection molding to remove moisture and volatiles, otherwise it will affect the quality of the product. When choosing a material, it is necessary to consider the drying conditions and drying time of the material, as well as factors such as the cost of drying equipment.
Molding cycle: The molding cycle refers to the time required to inject mold a product. It directly affects production efficiency and cost. Choosing a material with a short molding cycle can improve production efficiency and reduce production costs. For example, some thermoplastic elastomer (TPE) materials have a short molding cycle and are suitable for products with large production batches.
Material price: The prices of different injection molding materials vary greatly. When choosing a material, it is necessary to select a material with an appropriate price according to the product's budget and market positioning. Generally speaking, the prices of general plastics are low, such as polyethylene and polypropylene; while the prices of engineering plastics and special plastics are high, such as polycarbonate and polyetheretherketone.
Processing cost: The processing cost of materials includes the energy consumption of injection molding equipment, the wear of molds, labor costs, etc. Some materials may require higher injection molding pressure and temperature, or special mold structures, which will increase processing costs. When choosing a material, it is necessary to comprehensively consider the price and processing cost of the material to select the material with the lowest total cost.
Mold cost: Different materials have different requirements for molds. Some materials may require the use of special mold steels or surface treatment processes to improve the wear resistance and corrosion resistance of the mold. This will increase the cost of the mold. When choosing a material, it is necessary to consider the impact of mold cost on the total cost.
Environmental friendliness: With the improvement of environmental awareness, more and more enterprises and consumers are beginning to pay attention to the environmental performance of products. When choosing injection molding materials, it is necessary to choose environmentally friendly materials, such as degradable plastics and recycled plastics, to reduce the impact on the environment.
Renewability: Some materials are made from renewable resources, such as bio-based plastics. These materials have renewability and sustainability and are in line with future development trends. When choosing materials, renewable materials can be considered to improve the environmental performance and sustainability of products.
Product service life: If the product needs to be used for a long time, then materials with good durability and stability need to be selected to ensure that the performance and quality of the product will not decline during the service life.
Product safety: For some products that are in direct contact with the human body, such as food packaging and medical devices, the safety of materials is crucial. Materials that meet relevant safety standards and regulations, such as food-grade plastics and medical-grade plastics, need to be selected.
Supply stability of materials: When choosing a material, it is necessary to consider the supply stability and reliability of the material to ensure the continuity of production. Choosing materials with a wide supply channel and stable supply can avoid affecting production due to material shortages.
If you still have questions about material selection after reading the above content, you can contact us. Our Shibang injection molding mold factory has been established for more than 20 years. We have a professional engineering team to formulate injection molding solutions one-on-one according to your project.
Worldbound Group takes intelligent manufacturing and precision manufacturing as its core and is an intelligent manufacturing enterprise group integrating design, mold opening, injection molding, electronics, assembly and service. Under Worldbound Group, there are eight manufacturing factories located in Dongguan, Guangzhou, Shenzhen and Vietnam; two R & D centers are distributed in Shanghai and Hong Kong. It has a precision mold manufacturing workshop, an injection molding production workshop and a dust-free surface treatment workshop. It has hundreds of advanced manufacturing equipment such as CNC, mirror spark workshops, various large and medium-sized injection molding production lines, die-casting and precision blow molding production lines, environmentally friendly vacuum aluminum sputtering coating production lines, fully automatic spraying production lines, bonding, SMT patch, and intelligent COB chip bonding production lines. The main products are molds, toys, electrical accessories, medical device accessories, home appliance accessories, electronic products, small household appliances, and pet supplies. It provides high-end brands with a complete set of solutions integrating product design, precision mold manufacturing, injection molding and assembly, and after-sales service.
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