Thermoplastic Materials for Injection Molding
Thermoplastics are plastic polymers that soften when they are heated, allowing for molding, and solidify again as they are cooled. Because of their unique chemical properties, thermoplastic materials can be remolded and recycled without negatively affecting the material’s physical properties. This makes thermoplastics an ideal material for injection molding.
Thermoplastic materials are used for a wide range of applications from consumer goods to medical equipment, depending on the type of material. Commodity thermoplastics are the easiest to process and are used to manufacture products in high volumes. These materials are best for applications like packaging, clothing, food, and beverages. In contrast, engineered and specialized thermoplastics have been blended to enhance their characteristics. They are used for heavier-duty applications like military, aerospace, and medical industries.
Thermoplastic Materials Offered for Injection Molding
- ABS Thermoplastic
- Acrylic Thermoplastic Polymer
- Polybenzimidazole Thermoplastic Polymer
- Polyethylene Thermoplastic Polymers
- Homopolymer Thermoplastic
- Copolymer Thermoplastic
- Polyester Thermoplastic
- Polyurethane Thermoplastic Polymer
- Styrene Acrylonitrile Polymer
Properties of Thermoplastics
Thermoplastics are the only type of plastic that can be welded. When the plastic is heated, the material becomes a paste or a liquid that can then be molded into the desired shapes. Though each type of thermoplastic offers its own characteristics and properties, they can all withstand multiple re-shapings without any damage being done to the materials.
The Primary Benefits of Thermoplastic Materials:
- Can be remolded and recycled without damage
- Easy to mold and shape
- Offers high strength and lightweight
- Some can be used in place of metal
- Relatively low processing costs
- Easy to manufacture high volumes quickly
- Able to maintain high precision
- Chemically retardant and impact resistant
- Reduces waste and is more environmentally friendly
In the past, all rubber materials were thermoset, meaning they could no longer be changed once the injection molding process was complete. However, thermoplastic elastomers (TPEs or thermoplastic rubbers) make it possible for thermoset materials to behave similar to thermoplastics.
TPEs are a blend of rubber and plastic that, through a combination of both material’s characteristics, are ideal for a variety of applications. They are especially useful in the automobile industry, aerospace industry, and many consumer markets.
Thermoplastic elastomers are known as two-phase systems because they are created when a hard-thermoplastic phase is combined mechanically or chemically with a soft elastomer phase, taking characteristics from both phases to form the final product. From the hard phase, the TPEs get properties like processing and continuous temperatures, tear strength, and chemical and fluid resistance. From the soft phase, they get their hardness, flexibility, and compression set, among other properties.
Stack Plastics works with a wide range of thermoplastics in our injection molding processes. From standard to exotic to engineered, we have experience molding many materials for different applications. We can also blend thermoplastic materials with additives like PTFE for enhanced strength and durability.
The following thermoplastics can be used as an alternative to PVC or for any of your unique applications needs.
Acrylic is a thermoplastic polymer that exhibits many glass-like optical qualities but is hardier and more protective. It is often known as Lucite, Perspex, and Plexiglas. Acrylics are used in nearly every industry, and are used as a glass substitute for items such as:
- Motorcycle helmet visors
- Aircraft windows
- Viewing ports of submersibles
- Lenses of exterior lights of automobiles
Because of its impact resistance and strength, acrylic is also used to make googles and lenses.
ABS, or acrylonitrile butadiene styrene, is a synthesized plastic that combines styrene and acrylonitrile. This safe thermoplastic is used in many consumer products that humans come in direct contact with, such as cell phones, toys, microwaves, and other appliances. ABS thermoplastics are known for being strong, light, versatile, and tough.
ABS consists of three distinct monomers and by combining them, the thermoplastic becomes flexible and lightweight. Because of this, ABS flows smoothly and is perfect for injection molding.
Polybenzimidazole (PBI) is an artificial thermoplastic polymer with one of the highest melting points of any material that is applicable for use as a fiber. It is the most high-performance engineered thermoplastic material available. Because of this, PBI is used as a base for high demand equipment that is used by militaries throughout the world, as well as firefighting and police forces.
Because of its extreme hardness and durability, PBI can be difficult to machine, but Stack Plastics is experienced in engineering for demanding industries.
Polyethylene is not one specific material, but actually a group of thermoplastics characterized by the type, structure, and thickness of the polymer. Some common types include High-Density polyethylene (HDPE) that is used to make milk jugs and water pipes, and the softer, more flexible Low-Density polyethylene (LDPE) that is used to make squeeze bottles and bags.
In general, the higher the density, the higher the tensile and flexural strength, chemical and abrasion resistance, and surface hardness. Because these thermoplastics are highly resistant to temperature changes, they are often used in high stress environments, such as piping, oil transportation, and in the retail industry.
A homopolymer is one that is produced by the polymerization of a single monomer. They are known for being a tough and resistant thermoplastic material. They commonly used in the end consumer market for smaller goods, such as kitchenware.
There are several kinds of homopolymer thermoplastics including polypropylene, polycarbonate, and polyester. In general, all of these thermoplastics are great for injection molding.
A copolymer is a thermoplastic material produced by the copolymerization of two or more different monomers. They commonly are a glossy, cost effective material. Copolymer thermoplastics are used in a variety of applications, including industrial back end applications and smaller consumer items such as kitchenware.
Polyesters are extremely hardy materials that are fit for a large range of temperature and environmental demands. Polyester thermoplastics are among the most widely used injection molding polymers, seen most commonly in water bottles, but also have wide applications in the industrial sphere. They are known for their strength, stiffness, and toughness, as well as chemical resistance.
Polyurethane is a clear and flexible thermoplastic polymer that is most often used to produce shoe soles, gaskets, and wheels. It is extremely versatile and can be formulated to provide wide ranging characteristics. It exhibits excellent wear and abrasion resistance, and remains highly elastic and impact resistant, even at the hardest durometers or in extremely low temperatures. They are also resistant to oil and grease.
Styrene acrylonitrile is a copolymer and one of the toughest polymers in common use. It is known for its excellent toughness, rigidity, and dimensional stability. It is highly resistant to breaking and is often seen in kitchen applications. It is also used for applications such as:
- Computer components
- Packaging materials
- Autoclavable medical devices
- Battery cases
Thermoplastics Differ from Thermoset Materials
Thermoplastics are very different from thermoset materials. They are both used in the injection molding process, but thermosets can only be heated and molded once. They cannot be changed or melted back into their original shape. This makes them great for high-heat applications, but also makes thermoset plastics less versatile than thermoplastic materials.
During the thermoset plastic curing process, polymers are linked together and form a permanent chemical bond. In contrast, no chemical bonding takes place during the curing process of thermoplastics, making it completely reversible. Thermoplastics can be remelted and remolded whenever its necessary.
Contact Stack Plastics for Custom Thermoplastic Injection Molding
Stack Plastics is a custom plastic injection molding company that specializes in engineering thermoplastics, as well as other materials such as elastomers and exotic resins. We manufacture high quality molding for a variety of industries and applications, including medical devices and consumer products.
This list of thermoplastic materials is by no means exhaustive. To view examples of our products and injection molding, visit our work gallery. To discuss your unique material requirements, contact Stack Plastics today or request a quote.