Plastic Products Manufacturing Materials

Acrylic or polymethyl methacrylate has been used by a wide variety of different companies and individuals over the years. Many times acrylic is used as a substitute for glass. Acrylic is easily painted and fabricated and is available in many different stocked sizes, shapes and colors. Acrylic is generally used to produce things such as: signs, product displays, light diffusers, fake fingernails, car light lenses, aquariums.

Advantages - inherent UV stability, formability, easily fabricated, stiffness, clarity, able to be used as a UV stable cap layer on other substrates, able to be rigidized with fiberglass, scuff/mar resistance

Disadvantages - impact strength, cost, chemical resistance and density

ABS by itself is not a naturally UV stable material. ABS requires the introduction of a UV stabilizer into the resin mixture or requires a UV stable material to be adhered to the top of the ABS sheet. Acrylic is generally the material of choice by most thermoformers to cap their ABS sheet with to make it UV stable. The acrylic cap layer can be produced in a thin film called Korad® that is laminated on the ABS or in a thicker sheet called Solarkote® that is coextruded with the ABS. Korad® capped ABS will provide an inexpensive layer of UV protection and will also help with scuff resistance. Korad® is available in clear as well as many different standard colors. Solarkote® is a thick layer of acrylic that adds more UV protection to the substrate than is offered by Korad®. Solarkote® offers more scuff resistance and also adds more sheen or a deeper, richer look to the part it is capped with. Other materials such as ASA (Acrylonirtrile Styrene Acrylic Ester) are also available to cap ABS with to make the finished part UV stable.

Some would consider ABS the workhorse of engineering grade plastics. Although pricing is still quite high for ABS, ABS tends to be one of the cheaper engineering grade plastics and gives decent physical properties at its price point. ABS is extremely easy to form and readily available in stocked sheet. Products typically made from ABS include: dashboards, instrument clusters, machine covers, pipe, children's toys, luggage, panels for refrigerators.

Advantages - good heat deflection temperatures, good chemical resistance, good impact resistance, easy to thermoform and fabricate, good stiffness, can be combined with other materials to increase properties such as flame resistance and heat deflection

Disadvantages - cost (currently high), UV stability, susceptible to extreme degradation with additional heat histories, moisture absorption

Many products fall into this category. Their costs range in price from very reasonable (TPO) to extremely expensive (Polysulfone). These plastics are chosen when a very specific physical requirement(s) of the plastic must be present. Engineering grades of polymers are generally found in airplane components, train components, electrical components and other applications where certain governmental regulations or ASTM specifications must be met.

In some applications, Fire Retardancy is important. FR or Fire Retardant additives are available as modifiers for many different types of thermoplastics. The level of fire retardancy is usually specified by a customer and generally correlates to a specific UL94 FR rating. Ratings can vary from UL945VA (highest level of fire retardancy) all the way down to UL94HB (least fire retardant). Some thermoplastics are limited in the amount of fire retardancy that can be obtained. Typical thermoplastics that are available in fire retardant versions are: ABS (FRABS), HIPS (FRHIPS), TPO, Polycarbonate, Acrylic/PVC blends (Kydex®) and many others. Fire retardant versions of material are generally more expensive than standard versions and often times require minimum purchase amounts.

This plastic is one of the most common thermoplastics used by vacuum formers. HIPS is easy to paint and available in an infinite array of colors. Primary products that HIPS is used to make: drinking cups, point of purchase displays, retail packaging, toys, cd cases, various consumer products.

Advantages - good heat deflection temperature (180F), good stiffness and easy formability

Disadvantages - low impact resistance, cost (compared to other commodity polymers), low solvent and chemical resistance

Polycarbonate typically goes by the more familiar trade name of Lexan ©. Polycarbonate is available in many different stocked shapes, sizes and colors. PC is also available in clear. Polycarbonate is used in many different industries; from medical to automotive and many in between. Polycarbonate is used to make such products as: skylights, bulletproof windows, industrial guards, eyeglasses, game housings and hockey rink partitions.

Advantages - extremely tough, available in clear, available in many different grades, high flexural modulus, high heat deflection temperature

Disadvantages - moisture absorption, stressful on tools, poor chemical resistance, formability, requires good tooling to ensure good cosmetics.

Polyethylene is one of the most common inexpensive commodity plastics in use today. There are various grades of PE available and their use depends on the product requirements. Typical grades available:

• High Density Polyethylene: HDPE
• High Molecular Weight Polyethylene: HMWPE
• Linear Low Density Polyethylene: LLDPE
• Ultra High Molecular Weight Polyethylene: UHMWPE

PE is usually used where chemical resistance and toughness are required. PE is generally used for high volume products that are price sensitive. Typical applications include: dunnage trays, milk jugs, food packaging, blister packs, gas cans, outdoor playground equipment.

Advantages - cost, chemical and solvent resistance, impact strength, ability to compound with additives such as talc (for increased stiffness) to modify material's properties

Disadvantages - low flex modulus (stiffness), high CLTE (moves a lot when exposed to hot or cold temperatures), low heat deflection temperature, formability, longer program development times, requires expensive tooling to ensure part consistency

PETG is generally chosen due to its availability as a clear thermoplastic. PETG is more impact resistant that Acrylic yet not as tough as Polycarbonate. Typical products made from PETG include: electronic devices, covers, machine guards, medical braces, point of purchase displays, trays, signs.

Advantages - formability, cost, resistance to stress whitening, stiffness, toughness, decent resistance to some chemicals, available in FDA compliant grades

Disadvantages - density, minimum quantities to obtain reasonable pricing, susceptibility to UV degradation, adhesive bonding, lack of mar resistance

Polypropylene is an olefin that is similar to polyethylene. Many people prefer that the plastic is copolymerized with ethylene. This results in a product called Polypropylene co-polymer. Copolymerizing helps in the formability of the material and allows it to compete with some higher end plastics such as ABS. Polypropylene can have various fillers such as glass fibers added to it in order to modify its properties. Polypropylene is also used in the production of other plastics such as TPO (thermoplastic olefin). Some typical products made from Polypropylene include: food containers, RF capacitors, living hinges, plastic bags and chairs.

Advantages - chemical resistance, stiffness (better than PE), fatigue resistance, cold weather impact and cost

Disadvantages - formability, high CLTE (moves a lot with temperature changes), tooling costs, UV stability

TPO is becoming a very sought after plastic by many different companies in many different industries. Part of this is due to good marketing on behalf of some of the first companies to introduce the TPO thermoplastic to the market, and a lot of it is due to the physical characteristics of the plastic itself. TPO is basically a blend of Polypropylene and EPDM rubber. These two materials together result in some interesting properties that make TPO an attractive substitute to more traditional weatherable materials such as acrylic capped ABS. Products typically made from TPO include: car bumpers, rocker panels, machine covers, chemical shields, roofing membranes, engine covers, golf car bodies.

**Arrowhead was one of the first companies in the USA to start thermoforming TPO successfully. Arrowhead has alot of experience with TPO and we continues to thermoform the plastic on a regular basis.

Advantages - great chemical resistance, good heat deflection temperature (240°F), great cold weather impact properties, great UV stability, dimensionally stable (low CLTE ~ half that of ABS), good stiffness, price

Disadvantages - difficult to thermoform, difficult for some sheet suppliers to extrude, aluminum tooling required for higher volume parts (although Arrowhead has developed an Eco-Tool to get around this need), high minimum quantities, not stocked by distributors, difficult to paint, difficult to bond to