When developing a new product, there are many different types of plastic available for use. The choice of the correct one depends on the specific criteria of each application.
In our experience, developers should consider whether the plastic material is food grade, impact resistant, flexible, engineering grade, fire retardant or biocompatible. The following are our recommendations on the most common plastics used for each product requirement.
Food plastics
Plastics used for food production, cooking and storage must meet certain criteria. They must be sterile and not transfer any flavor to the food. They should be non-biodegradable in most cases, non-absorbent and impervious to edible oils and acids.
PET (polyethylene terephthalate) is almost ideal in all these categories, which is why it is the most common plastic for food packaging. It is found everywhere for use in water and soft drink bottles and other food containers. It is strong and unbreakable, but also lightweight and easily recycled. PET, in fiber form, is called polyester and is the most common type of man-made fabric for clothing and insulation.
LDPE (low density polyethylene) is used to make food bags and cling film, while HDPE (high density polyethylene) is ideal for plastic cutting boards. PP (polypropylene) is also found in food packaging, such as yogurt cups.
It should also be noted that many engineering grade plastics are also considered food safe, but are only used in food processing equipment or other durable products due to their higher cost.
Impact resistant
Plastic in this category must withstand repeated shocks and return to its original shape without denting or cracking.
ABS (acrylonitrile butadiene styrene) and HIPS (high impact polystyrene) are used to manufacture power tool housings, tool boxes, luggage, sporting goods and other products that take a lot of abuse but remain rigid. These resin composites can be made even stronger with the addition of fiberglass or carbon fiber.
There is also a large market for transparent plastic as a replacement for glass. PC (polycarbonate) is ideal for motorcycle windshields, plastic eyeglass lenses and lightweight protective shields.
Flexible
All plastics have some degree of flexibility. Many products do not require high strength, but must be flexible without losing their shape completely.
PP (polypropylene) is the king of plastics for making living hinges such as those found in shampoo bottle caps or pill dispensers. This type of plastic can be bent thousands of times before it breaks within the life of the product.
HDPE is more durable for heavy use, so it is found in heavy-duty trash cans that are thrown away a lot. TPU (thermoplastic polyurethane) is a type of elastomer. It is elastic and rubbery, so it is used for wheels, sealing rings and gaskets, cable housings and sporting goods. The degree of softness and elasticity is controlled by varying the chemical composition.
Engineering degree
Engineering plastics are crystalline polymers with mechanical properties similar to metal. They are strong and durable like their metal counterparts, while being lightweight and less expensive to produce in large production volumes as we do at Protospain.
This category includes plastic materials such as ABS, Nylon (polyamide), PEEK (polyetheretheretherketone) and POM (polyoxymethylene). All are rigid, temperature resistant and low friction. In addition, PEEK, ABS and Nylon can be 3D printed for even more design options.
Some products made from engineering plastics include ball bearings, gears and shafts, knife handles, plastic gun bodies, switches and other weight-saving parts for automotive and aerospace applications.
Fire retardant
In the presence of a flame or other high heat source, any plastic will melt and some will catch fire. Concern for fire resistance is especially important when plastic is used in a confined space such as the interior of an automobile or the cabin of an airplane.
However, plastics vary in their response to fire. Some are self-extinguishing when the heat source is removed. Others may spread flames vertically or produce hazardous fumes.
The most naturally fire resistant plastic is PVC (polyvinyl chloride). The presence of chlorine helps to strip the fire of oxygen needed for combustion, but, of course, chlorine gas is another serious problem.
The secret to fire resistance is to coat the plastic material with a flame retardant chemical or add impurities to the compound that will help interrupt the combustion cycle. Some of these additives include boron, antimony, chlorine, bromine, aluminum and phosphorus. Because there are so many variables and formulations, it is best to check with the manufacturer to confirm what UL fire safety rating the material has. The highest rating is UL94-VO, which means that the material will not burn, is self-extinguishing and will not drip when melted on the ground.
Biocompatible
The use of plastic components for medical devices and equipment has increased considerably in recent years. To protect patients and regulate the industry, ISO-10993 helps to codify the various medical uses of plastic material.
Resins can be used to manufacture blood stents, artificial joints and bone replacements, catheters, prostheses, infusers, cardiac monitors, valves, tubing, pill dispensers and many more.
It is essential to use the right resin for each application. The ISO guidelines determine the assessment of “biohazard” based on the interaction with the body: permanently implanted, in temporary contact with the skin or for use in medical devices.
Based on these categories, we can suggest the following:
– Short-term contact and skin contact: PE, PS, nylon, PVC, Teflon, PEEK, PP, PPSU
– Long-term contact or internal medicine: PPSU, HDPE, PMMA, epoxy (for dental implants)
– Medical equipment and tools: PEEK, POM, PMMA, PC, PVC, HDPE