Injection molding is one of the most common manufacturing methods used to produce parts; this also means that there is a large selection of materials available for molding. These materials are engineered and include common materials such as PC-ABS, as well as specialty materials such as injection molded PEEK. For every part you make, the material you choose should be intentional. In this case, the utility, efficiency and cost of the part should be carefully considered. Your material selection will always be directly related to the application of the part.
Injection Material Selection
You can refer to the following criteria, which can help you understand the priorities for the selected materials:
1. Location
You have to think about where your parts will be placed, whether it's outside, inside, under the hood, in a dark, wet environment, or somewhere else?
2. Temperature
Consider temperature when choosing materials. Will the product end up in the refrigerator, or somewhere very warm or hot?
3. Life cycle
How long do you expect the part to last? 5 years, 25 years, or longer?
4. Warranty
Consider the warranty. Especially for the automotive industry, you have to consider that after a few years the part might break, how much will the warranty cost?
5. Cost constraints
There are two different types of materials. You can get a commodity plastic (like HDPE or PP) which are usually high density, low heat, readily available and relatively cheap.
The second category is engineering plastics, including materials such as PEEK and PEI. They are very expensive and harder to find, but they are heat resistant and tough.
6. Appearance requirements
Does the part need to be completely transparent, or a certain color? Color matching may be required if your part needs to match other parts in the assembly.
7. Design features
Consider the mechanical engineering aspects of the part. Does it need to be flexible, compressible, bondable, etc.? Does it need to be tensile strength (meaning it can't be pulled apart)?
8. Compliance
Adding certain compliances can quickly add to the cost of a part, which is why it is important to evaluate what is needed and what might be redundant.
Does your part need to be food safe and FDA compliant? Or does it require medical grade, ISO, electrical compliance, etc.?
How do I choose the best plastic for injection molding?
To select the right medical injection molding material, there are several aspects to consider. Let's see how to choose the right plastic material for injection molding by examining the various materials and their properties:
1. ABS
It is a synthetic plastic of acrylonitrile, butadiene, and styrene. It is a resin with high strength, good toughness, and excellent comprehensive properties. It has a wide range of uses and is often used as engineering plastics. ABS resin can be processed into plastics by molding methods such as injection molding, extrusion, vacuum, blow molding, and roll pressing, and can also be processed secondaryly by machinery, bonding, coating, and vacuum evaporation. It can also be used for household appliances. Because of its good performance in oil resistance, acid resistance, alkali resistance, salt and chemical reagents, and electroplatability, it has the advantages of good luster, light specific gravity and low price after being plated with a metal layer, and can be used to replace some metals.
Advantages: hard, easy to extrude, easy to dye, flame retardant, impact resistance, good surface
Disadvantages: poor solvent resistance, low dielectric strength, low elongation. Uses: The largest application fields of ABS are automobiles, electronic appliances, and building materials.
Uses: automotive field (automotive instrument panels, body panels, interior trim panels, steering wheels, sound insulation panels, door locks, bumpers, ventilation pipes, etc.) electrical appliances (all kinds of household appliances and electronic appliances for office appliances) building materials ( ABS pipes, ABS sanitary ware, ABS decorative panels, etc.). In addition, plastic products are also widely used in industries such as packaging, furniture, sports and entertainment products, machinery and instrumentation industries.
2. PE
Polyethylene is widely used in the manufacture of plastic bags, plastic films, and milk barrels. Polyethylene is resistant to various organic solvents and various acids and bases, but not to oxidizing acids such as nitric acid. Polyethylene will be oxidized in an oxidizing environment. Polyethylene can be considered transparent in the film state, but is opaque when present in bulk.
Advantages: soft, non-toxic, easy to dye, impact resistance, moisture resistance, chemical resistance, low temperature resistance (-70 ° C ~ 100 ° C), good electrical insulation
Disadvantages: difficult to extrude, high coefficient of thermal expansion, difficult to fit, poor temperature resistance
Uses: Mainly used to make films, packaging materials, containers, plastic pipes, tapes, monofilaments, wires and cables, daily necessities, etc. Types and characteristics of plastics (classification and application of common plastic products)
3. PVC
Polyvinyl chloride is the most widely used plastic in construction. With high mechanical strength and good chemical stability, the biggest feature of PVC is flame retardancy, so it is widely used in fire protection applications. However, polyvinyl chloride will release hydrochloric acid and other toxic gases during combustion. PVC products are divided into two categories: hard and soft. Hard products do not add plasticizers, on the contrary, they are soft products.
Advantages: good dimensional stability, low cost, good weather resistance, adding different proportions of plasticizers, can easily adjust the hardness
Disadvantages: poor chemical resistance and temperature resistance, higher density than ordinary plastics, hydrogen chloride will be generated after thermal decomposition
Uses: Used to make doors and windows and energy-saving materials. PVC film (packaging bag, greenhouse film, shrink film, raincoat, tablecloth, curtain, inflatable toy, etc.) Storage tank air duct and container) PVC soft products (hose, wire and cable, plastic sandals, soles, slippers, toys, auto parts, etc.) PVC packaging materials (various containers, films, mineral water bottles, beverage bottles, cosmetic bottles, refined Oil packaging) PVC wall panels and floors, PVC daily necessities (all kinds of imitation leather, artificial leather, luggage bags, sports products such as basketballs, uniforms, ponchos, imitation leather jackets, rain boots, etc.).
4. PMMA
Polymethyl methacrylate is also called plexiglass. 92% light transmittance, thermal denaturation temperature between 74°C~102°C
Advantages: high optical transparency, good weather resistance, good rigidity, easy to dye, high mechanical strength, light weight, UV and aging resistance, good insulation
Disadvantages: poor chemical resistance, poor heat resistance, should stand in a concentrated place, relatively fragile, insufficient surface hardness, low impact strength,
Uses: optical instruments (various optical lenses, glasses, magnifying glasses, various lenses, etc.) stationery and daily necessities (various drawing utensils, teaching models, lampshades, pen holders, buttons, legalists, candy boxes, soap boxes, etc. ) architectural aspects (indoor and outdoor lighting displays, ceiling photo equipment, sculptures, furniture, solar collector covers, bathtubs, washbasins, etc.) other aspects (medical equipment, prosthetics, dentures, hard contact lenses, inorganic silicon glass substitutes, signs, windshields, etc.).
5. PS
Polystyrene Polystyrene is a colorless and transparent plastic similar to glass. It is a colorless and transparent plastic material. It has a glass transition temperature higher than 100 degrees Celsius, so it is often used to make various disposable containers that need to withstand the temperature of boiling water, and disposable foam lunch boxes. Need professional PS glue bonding. After adding butadiene, the impact toughness can be improved, and mechanical parts with excellent performance can be manufactured
Advantages: good high-frequency insulation, light transmission second only to plexiglass, low cost, transparent and dyeable, dimensional stability, high rigidity
Disadvantages: high fragmentation, poor solvent resistance, poor temperature resistance, no resistance to benzene, gasoline and other organic solvents, low impact strength
Uses: Electronic appliances (housing and electrical instrument parts of televisions and tape recorders, high-frequency capacitors, etc. Construction fields (transparent components of buildings, optical instruments and transparent models, lampshades, instrument covers, packaging containers, etc.) Daily necessities (combs, boxes, toothbrushes, etc.) Handles, ballpoint pen holders, school utensils, toys, etc.) Other aspects (used for foam manufacturing shockproof, sound insulation, heat preservation, sandwich structural materials, life buoys, Styrofoam tableware, etc.)
6. PP
Polypropylene The density of polypropylene is the smallest among all plastics. It is often used to produce construction products such as pipes and sanitary ware. It has high impact resistance, strong mechanical properties, and resistance to various organic solvents and acid and alkali corrosion. Hardness, strength, stiffness and heat resistance are stronger than PE
Advantages: easy to dye, good moisture resistance, good chemical resistance, high hinge characteristics, impact resistance, good high frequency insulation
Disadvantages: It is not easy to extrude complex special-shaped, easy to be decomposed by ultraviolet rays, difficult to join, easy to oxidize, and not wear-resistant
Uses: injection molding products (automotive: leading materials for auto parts, such as bumpers, wheel housings, instrument panels, steering wheels, handles, battery cases, etc.; daily necessities: injection molding hangers, stools, washbasins, buckets, toys, stationery, office supplies , fixtures, turnover boxes, etc. Electrical appliances: washing machine barrel, TV casing, electric fan blades, refrigerator lining, small home appliance casing) film products (moisture-proof packaging materials, high-end clothing, cigarettes, etc. packaging, softness is not good, durable Good thermal and electrical insulation, can be used to make packaging for frozen and fresh food, insulation materials for various electrical appliances, typewriter belts, etc.) fiber products (monofilament: rope, fishing net; Used in tents and rainproof cloths; fibers: carpets, blankets, clothing materials, mosquito nets, artificial turf, artificial fur, diapers, filter cloths, non-woven fabrics, curtains) extrusion products (folders, name-brand folders, albums, disposable water cups, etc. There are also rods, plates, etc.)
