Plastic injection molding principles, materials and applications

Ruiyi can help you choose the right plastic material for your application, whether your project involves plastic injection molding for medical use, molded plastic parts for the automotive industry, or other projects, we can help you go from design to production faster.

The principle of plastic injection molding mainly involves the following steps:

a.Add ingredients. The plastic particles enter the heating barrel through the feed port of the injection machine. 1

b.melt. In the heating cylinder, the plastic particles are heated above the melting point and become plastic molten plastic.

c.Pressure injection. The molten plastic is quickly injected into the cavity of the mold through the nozzle under the high pressure of the injection machine.

d.Cool and solidify. The molten plastic injected into the mold is cooled by the cooling system of the mold, gradually solidifying and stabilizing the molding.

e.Open the mold and take it out. The formed product is fixed by the mold. After cooling to a certain temperature, the mold is opened and taken out.

This process is mainly used for the molding of thermoplastics, but can also be used for the molding of thermoset plastics. Injection molding is an intermittent process that requires quantitative feeding to ensure stable operation and uniform plasticization, thereby obtaining high-quality plastic parts.

There are ten commonly used injection molding materials: (Ruiyi injection molding materials include but are not limited to the following materials, please consult for details)

● Acrylonitrile Butadiene Styrene (ABS)

● Nylon polyamide (PA)

● Polycarbonate (PC)

● Polyethylene (PE)

●Polyoxymethylene (POM)

● Polypropylene (PP)

● Polystyrene (PS)

● Thermoplastic elastomer (TPE)

● Thermoplastic polyurethane (TPU)

● Acrylic (PMMA)

1. Acrylonitrile-butadiene-styrene (ABS)

ABS is a rigid and lightweight material. This is a very popular material for plastic injection molding. Did you know that LEGO bricks are made of ABS? ABS is an engineering-grade thermoplastic with a relatively low melting point and is easy to mold. This opaque polymer supports the use of colorants and offers different textures and finishes. ABS is known for its strength and impact resistance.

ABS applications, Class

Injection-molded ABS is used in electronic components and keyboard keys, protective headgear, plastic siding for electrical outlets, and automotive components such as dashboards, wheel covers, and auto body parts. Other applications include consumer products, sports equipment and industrial accessories.

ABS can also be combined with glass fillers for added strength, or with polycarbonate for improved low-temperature impact resistance.

2. Polycarbonate (PC)

Polycarbonate is a clear thermoplastic. They are impact resistant and can withstand high levels of plastic deformation without breaking or cracking. Polycarbonate (PC)

Polycarbonate (PC) plastic is a strong, tough material that is naturally transparent. Their properties are similar to PMMA, but polycarbonate maintains its physical properties over a wider temperature range. Once tinted, PC retains its color and maintains its strength over time.

PC applications, Class

Polycarbonate is used in machine guards, clear or tinted windows, diffusers and light pipes for light-emitting diodes (LEDs), as well as transparent pipes. This material can also be used to produce clear molds for polyurethane and silicone castings.

Polycarbonate can be filled with glass and compounded with ABS to improve impact resistance. Some grades contain relatively small percentages of stainless steel fibers.

3. Nylon polyamide (PA)

Polyamides (PA) are a large family of materials that can be natural or synthetic. Nylon polyimide, however, is always synthetic. Nylon injection molding is challenging because this polyamide shrinks easily and is underfilled.

Nylon applications and Class

Nylon is often used in strong mechanical components such as bearings, bushings, gears and slides. It is also ideal for housings and snap closures, threaded inserts, power flaps, clamps and fixtures. Other applications range from toothbrushes and wheels to medical implants and electrical connectors.

There are four main grades of nylon: Nylon 66, 11, 12, and 46. Each grade has slightly different mechanical properties.

Nylon 66 has a higher melting point and greater acid resistance for use in chemical processing applications.

Nylon 11 has a higher resistance to dimensional changes because it is more resistant to moisture. It is used in outdoor applications.

Nylon 12 has the lowest melting point and relatively good resistance to water absorption.

Nylon 46 operates at higher temperatures than other grades of nylon. Applications include engines and transmissions

Nylon grades can be filled with glass to increase mechanical strength. From sports equipment to industrial components, you'll find a wide range of applications for this type of thermoplastic.

4.Polyoxymethylene (POM)

Polyoxymethylene (POM) is an engineering plastic also known as acetal. It can be injection molded into parts requiring low friction, high stiffness and excellent dimensional stability.

POM application, class

Due to its low coefficient of friction, injection molded POM is suitable for bearings, gears, conveyor belts and pulleys. Other applications include fasteners, eyeglass frames, knife and firearm parts, locking systems and high-performance engineered components.

POM comes in fiberglass or mineral-reinforced grades for increased strength and stiffness. Compounds reinforced with these two materials provide an excellent balance of mechanical properties.

5. Polypropylene (PP)

Polypropylene (PP) has similar properties to polyethylene (PE), but is harder and more heat-resistant. It is the second most commonly used plastic in the world. Although the density of polypropylene varies with fillers, pure PP is the lowest density commercial plastic. Polypro (as this plastic is sometimes called) can also be recycled up to four times. Additionally, recycled PP can be combined with other plastic materials.

Injection-molded polypropylene degrades under UV light and is highly flammable. At temperatures above 100° C (212° F), it dissolves into aromatic hydrocarbons such as benzene and toluene that are harmful to human health. Because it is difficult to bond, PP is difficult to color;

PP application, class

Injection molded polypropylene has a variety of consumer, commercial and industrial applications. Examples include children's toys, storage containers, sporting goods, packaging, appliances and power tool bodies.

PP plastic can be filled with fiberglass to increase dimensional stability, stiffness, strength and resistance to warping. Grades include highly crystalline polypropylene (HcPP), which has higher stiffness than regular polypropylene.

Polypropylene is a flexible material. It also has good chemical resistance and will not leach into food, making it an ideal choice if you want to make food containers or tableware.