What exactly is thermoplastic resin and why is it an important material in the injection molding process? Find the answers below.
The use of plastic materials throughout the world has significantly increased over the last few decades. There are presently over 100 million tons of such materials used per time. The most significant tonnage is thermoplastics, as they make up approximately 80 percent of all plastics used globally today.
Thermoplastic Materials
Thermoplastic materials are just one of several types of plastics used extensively for their application versatility and recyclability. They are primarily created when monomers – i.e., repeating units – link into chains or branches.
Thermoplastic resins are unique materials that soften to liquid form in very high heat but solidify as soon as they cool. Due to these characteristics, manufacturers can mold thermoplastic materials into a wide variety of structures and shapes. This makes plastic resins widely applicable to several industries. But in most cases, they are used in injection molding processes.
Types of Thermoplastic Materials
Thermoplastic materials generally used in manufacturing processes include:
- PVC (polyvinyl chloride)
- PS (polystyrene)
- PE (polyethylene)
These are frequently used in packaging. Other well-known thermoplastic materials used in manufacturing industries include:
- Acetal Homopolymer Polyoxymethylene
- Acrylic
- Polycarbonate
- Acetal Copolymer Polyoxymethylene
- Nylon
- Teflon
- Polypropylene
Every thermoplastic material has unique applications. For instance, acrylic is widely used in making windows, aquariums, signs, and medicine. Nylon is used in making machine screws, rope, gear wheels, etc. This shows that nearly every industry has a thermoplastic they use.
Benefits of Thermoplastic Resins
- They Offer Recyclable Advantages Over Thermosetting Plastic
Thermosetting plastic and thermoplastic resins are not the same as they provide 2 unique classes of polymers with their respective characteristics. The primary differences between these 2 classes of polymers are their reaction to heat and their melting points.
Thermoplastics are generally helpful in injection molding since they possess repeatable melting processes without damaging the materials. This makes them have low melting points. For this reason, thermoplastics are widely employed in several applications, from mechanical parts to plastic bags, etc.
On the other hand, thermosetting plastic can withstand incredibly high temperatures. These polymers link together during the curing process to make up a permanent chemical bond.
This implies that these materials can no longer melt any time heat is applied, and for that reason, they cannot be remolded. This is just one of the major reasons why thermosetting plastics are utilized for appliances, electronics, as well as other high-heat applications.
- They Are Perfect for Plastics Molding
Thermoplastic resins form polymers – i.e., chemical bonds – when employed in the plastics molding process. The bonding of the numerous molecules included in the polymer chains establishes the characteristics the plastic will showcase.
The chemical/molecular bonding that makes up polymers weaken when molding machines heat the plastic resin. The outcome is a heavily viscous liquid, which you can inject into a molding tool.
As soon as the plastic cools, the chemical bonds solidify, giving you your desired or specified plastic part.
Other benefits of thermoplastic resins include:
- Dimensional stability.
- High resistance to chemical reactions.
- A vast number of finishing options.
- Ideal reshaping capabilities.
- Suitable for high-impact applications.
- Zero fumes, toxic smells, harmful discharges, etc. used in manufacturing.
Despite the numerous advantages that thermoplastic materials bring to the table, they are not without a few disadvantages, such as:
- Low melting point.
- It can be very expensive.
- It can be susceptible to organic solvents.
- It can fracture or crack under high-stress levels.
Despite these drawbacks, thermoplastic materials are still used globally in several industries, most especially for injection molding.
Thermoplastic Parts Used for Injection Molding
Thermoplastic injection molding is the most popular way of manufacturing parts. Thermoplastics are polymers that can be softened by softened or molten by heating and solidified via cooling. This is a physical change, not a chemical change, that occurs when thermoset materials are created.
Here are some of the standard thermoplastic parts used in injection molding:
- Acrylonitrile Butadiene Styrene (ABS)
When employed in injection molding, Acrylonitrile butadiene styrene provides high impact strength, stiffness, toughness, and tensile strength. It offers excellent machinability and equally maintains exceptional dimensional stability under heavy loads.
ABS is resistant to most oils, acids, alkalis, etc., and has remarkable creep resistance and excellent ductility.
- Thermoplastic Rubber (TPR)
Thermoplastic rubber (TPR) refers to a class of copolymer materials that readily combine specific physical characteristics of rubber and plastic. These materials exhibit high weathering, flexural fatigue, and chemical resistance.
TPR also exhibits excellent abrasion and tear resistance, high impact strength, and excellent dielectric properties.
- Polycarbonate (PCs)
Polycarbonates are uniquely rigid and strong thermoplastics that provide high impact strength and stiffness. They also offer excellent strength retention properties and thermal resistance at high temperatures.
PCs exhibit high shear, flexural, and tensile strengths, excellent dielectric properties, good creep resistance, etc.
- Liquid Crystal Polymer (LCP)
Liquid crystal polymer (LCP) is an exotic injection molding resin that maintains incredibly high temperatures and mechanical strength. It is an inherent flame retardant and exhibits exceptional chemical resistance.
Liquid crystal polymer – also known as Kevlar, Zenite, and Vectra – provides excellent weatherability, as well as incredibly high-stress resistance, cracking.
- Styrenics
Styrenics refers to a specific family of thermoplastic resins that exhibit high rigidity, dimensional stability, reliable mechanical characteristics, and excellent dielectric performance.
Styrenics are uniformly lightweight, water-resistant, with a high strength-to-weight ratio and excellent thermal insulation.
- Olefins
They are polymer-blend materials that feature a combination of thermoplastic, rubber or elastomer, and filler material. The different groups of materials exhibit several properties based primarily on their components.
However, olefins generally provide the following:
- High impact resistance
- UV resistance
- High stiffness
- Good flexibility
- Excellent dimensional stability
- Excellent weather resistance
Thermoplastic Elastomer (TPE)
This covers up to 6 classes of thermoplastic resins, and each one offers superior energy efficiency and consistency. Thermoplastic Elastomers require hardly any compounding and no reinforcing agents, stabilizers, or cure systems.
Conclusion
Thermoplastics remain one of the most used – and common – materials employed in a wide range of manufacturing processes. As you can see, there are various types of thermoplastic resins, and each one can be used based on your primary application.
This is why it is crucial to know the characteristics, advantages/disadvantages, etc., of thermoplastic materials before you start using them for your applications or processes.