With several advantages over other manufacturing techniques, plastic injection molding has become one of the most popular methods employed by manufacturers worldwide. This process involves the use of plastic resins, and its versatility is one of its most attractive features. However, with so many types of plastic resins available in the market, choosing the right one for a project can be challenging. When selecting a resin for plastic injection molding, it is essential to keep in mind the project’s requirements. With this factor in focus, making the right choice becomes far easier.

Keep reading as TLD Vietnam shares the key factors to consider when selecting a resin, along with the most commonly used plastic resins for injection molding.

What Are Plastic Resins Made Of?

Plastic resin is one of the byproducts obtained during crude oil refinement. Since crude oil contains different types of chemicals, isolating a specific one involves a distillation process, achieved by heating the oil.

The term “cracking” refers to the process used to modify these chemicals, known as monomers, encouraging them to form hydrocarbon chains with the help of a catalyst. These hydrocarbon chains, also called polymers, are the building blocks of plastic resins. To produce different resin types, manufacturers change the monomer used in the process.

What Is Injection Moulding?

Injection molding is a manufacturing process used to produce plastic parts in large volumes. It is one of the most common methods for mass-producing plastic components with high precision and consistency. The process involves:

• injecting molten plastic material into a mold cavity,
• allowing it to cool and solidify, and then
• ejecting the finished part from the mold.

Top Common Plastic Resins For Injection Molding

There are many plastic resins used for injection molding. These resins have special features that make them ideal for some manufacturing processes and less suited for others. Below are common plastic resin types used in the production of injection molding.

Polyethylene (PE)

Polyethylene is available in several forms, primarily low-density polyethylene (LDPE) and high-density polyethylene (HDPE). LDPE is flexible, impact-resistant, and offers excellent resistance to moisture and chemicals, making it suitable for computer parts, toys, compost bins, agricultural products, and certain medical components. It performs well at low temperatures but has limited high-temperature resistance. HDPE, on the other hand, is more rigid, with higher tensile strength and better heat resistance, making it ideal for food packaging, kitchenware, water bottles, and other applications where stiffness and durability are essential. Both types are valued for their low cost and strong chemical resistance.

Polypropylene (PP)

There are a lot of advantages to producing with this plastic resin. It has high chemical resistance, electrical insulation, elasticity, and an elevated melting point, which allows it to withstand high-temperature applications. It has excellent stress resistance and tensile strength, making it suitable for use in automotive components, construction materials, and electronic parts. Its safety for food contact also makes it a preferred choice in food and beverage packaging. PP’s dimensional stability under steam sterilization cycles further extends its suitability for medical applications such as syringes, connectors, and implant caddies.

Polyvinyl Chloride (PVC)

PVC is a chemically resistant thermoplastic that can be formulated into rigid or flexible forms. It withstands multiple sterilisation processes, including steam autoclaving and gamma irradiation. Transparent grades allow direct visual inspection of contained fluids, while their abrasion resistance supports applications with extended service life. PVC is employed extensively in medical devices such as IV bags, catheters, oxygen masks, and dialysis systems, as well as in building products including pipe and conduit systems.

Polystyrene (PS)

Polystyrene is a low-density, amorphous polymer with inherent transparency and good electrical insulating properties. Although it is stable under gamma, it is easy to degrade under ultraviolet light unless stabilisers are incorporated. In medical and laboratory environments, PS is used in Petri dishes, culture trays, diagnostic kit packaging, and other single-use laboratory articles. The processing is quite easy, and the ability to replicate fine detail makes it suitable for precision-molded laboratory consumables.

What Factors Matter In Plastic Resins Selection

When looking for plastic resin for plastic production, research is important. For better decision-making, below are some factors to consider when selecting a plastic resin.

Mechanical property requirement

Resin selection must consider hardness, flexibility, and tensile strength. Hardness, measured on the Shore scale, determines surface resistance to indentation and must correspond to operational stresses. Flexibility refers to the ability to withstand bending without fracture and is distinct from material softness. Tensile strength defines the maximum load a resin can endure before failure and may be enhanced through reinforcement with fillers such as glass fibre or carbon fibre.

Chemical compatibility

Chemical resistance is a critical parameter in applications where the resin will contact cleaning agents, solvents, or process chemicals. Compatibility data from the resin manufacturer should be reviewed to assess long-term stability in the intended chemical environment.

Environmental compatibility

Performance under varying environmental conditions must be evaluated. This includes resistance to temperature extremes, ultraviolet radiation, and humidity. Data regarding thermal deflection temperature, UV stability, and moisture absorption rates should be examined when the component will be used in demanding or outdoor environments.

Material Cost

Material cost is influenced by polymer availability, production complexity, and performance characteristics. While economic considerations are important, cost should be assessed in relation to the required mechanical performance, service life, and regulatory compliance of the final product.

Conclusion

Choosing the right plastic resin is key to ensuring product quality, performance, and cost-efficiency. By matching resin properties to project needs, manufacturers can achieve the best results.

As a global plastic resin distributor, TLD Vietnam provides a wide range of resins for diverse manufacturing needs. With a trusted supplier network and efficient logistics, we ensure competitive pricing, reliable quality, and on-time delivery.

For more information about TDS or any further support, feel free to contact TLD Vietnam