Plastic extrusions can be produced in a number of different materials, shapes and designs. Keller offers the following different profiles in standard commodity-grade plastics:
- Polyethylene Profiles
- Polyproplyene Profiles
- Polystyrene Profiles
- PVC Profiles
- Thermoplastic Elastomers
Polyethylene is a fairly “old” material first developed in the 1930’s. Polyethylene is one of the lowest cost materials in Extruded Plastic Profiles and has some amazing properties. Polyethylene profiles have good impact strength from temperatures as low as -40° F and up to 176° F. Polyethylene profiles are considered to be fairly “flexible” and have excellent chemical resistance along with resistance to moisture absorption. Because of Polyethylene’s excellent chemical resistance, it is almost impossible to bond with adhesives. We do however have an Extruded Plastic Profile that we can recommend. Polyethylene profiles are easy to process and is a lightweight Extruded Plastic Profile (floats on water). Polyethylene plastic will tolerate some outdoor exposure but is not considered a weatherable material. Polyethylene can be coextruded with some thermoplastic Elastomers (TPEs). Polyethylene will burn quite readily (similar to a candle). Polyethylene profiles have an upper service temperature of about 180° F depending on the grade.
Low Density Polyethylene: Low Density Polyethylene (LDPE) is translucent or opaque, is quite flexible and fairly tough. When colored, LDPE profiles have a glossy finish.
High Density Polyethylene: High Density Polyethylene (HDPE) has increased tensile strength, is more rigid, has better chemical resistance, and can withstand higher temperatures than LDPE. When colored, HDPE profiles have an opaque and generally a fairly glossy finish.
Polypropylene was introduced in the 1950’s as an alternative to Polyethylene and is very popular today. Polypropylene profiles are very similar to Polyethylene profiles except this material is stiffer and its upper service temperature is about 200° to 220° F. Polypropylene is naturally translucent, and when colored produces plastic profiles with a glossy finish. Polypropylene profiles are easy to process, and have good chemical resistance along with fair impact strength. Polypropylene has very good resistance to repetitive stress so this material is often preferred in applications requiring hinging or bending motions. Polypropylene profiles do not like the cold — less than 32 ° F — though copolymers are available that will help with the impact strength at these temperatures. Polypropylene profiles or Extruded Plastic Profiles do not typically like the sun and the material is flammable.
Polystyrene is another veteran material developed in the 1930’s. It is an inexpensive, versatile plastic that can be rigid or foamed (Styrofoam™). Polystyrene profiles can be clear, hard, water resistant and lightweight, but have limited flexibility. This material is not good for outdoor use because it degrades with exposure to light. Polystyrene profiles are easy and inexpensive to produce. Because Polystyrene can be transparent, it offers excellent colorability in plastic profiles. Polystyrene or Extruded Plastic Profiles has outstanding electrical properties, good thermal and dimensional stability but poor resistance to solvents. Polystyrene does not like extreme temperatures, has a relatively low melting point, and will start to soften around 212 °F.
High Impact Polystyrene: A rubberized Polystyrene blend called High Impact Polystyrene or HIPS offers improved impact strength along with economical pricing.
PVC is one of the oldest thermoplastics and was first patented in the US in the late 1920’s. By itself, PVC is hard and brittle at room temperature, but PVC is compatible with many additives that lend it a wide range of performance characteristics that can meet diverse application needs. PVC can be made very rigid and strong for use in construction and pipes, or as flexible as needed for use in fabric and carpets. PVC is extremely versatile with a wide variety of resin types. It is relatively inexpensive and easy to process. PVC profiles have pretty good chemical resistance, water and weather resistance, offer fair thermal stability, have excellent electrical insulation properties, have fair heat resistance, and are inherently flame retardant because PVC is chlorinated. PVC profiles can be clear or colored and can have a high gloss or matte finish.
Flexible PVC is an excellent material for the use in latex-free profiles. Flexible PVC costs less by weight than rubber or TPEs and provides significantly greater clarity. Flexible PVC is readily solvent-bonded, more kink resistant (in tubing) and exhibits less neck-down (width/breadth narrows) when stretched. Flexible PVC is generally known to be the most cost-effective Extruded Plastic Profile, high-performance material used in Latex-free profiles.
While PVC is considered a very good overall plastic material in terms of price and properties, it is currently receiving some negative publicity due to the presence of chlorine in its chemical makeup. With today’s concerns for the environment, some of our customers are choosing other “greener” materials to meet their application needs. We have been working on alternatives to PVC for quite some time and have come up with a number of new materials that offer similar properties to PVC along with attractive pricing.
Introduced in the 1960’s, Thermoplastic Elastomers (TPE’s) are materials with rubberlike flexibility and extensibility — the ability to snap back quickly after being extended to twice their original length. Thermoplastic Elastomers have a wide range of hardnesses and can absorb vibrations (energy). There are many types of Thermoplastic Elastomers; we work mostly with the Styrenics, Thermoplastic Polyurethanes (TPUs) and Thermoplastic Olefins (TPOs).
Styrenic TPEs offer the lowest durometer along with the highest elongation. They have fair outdoor weatherability, good low temperature performance, low tension set and good “rubberlike” feel. They can be coextruded with a number of other materials. Styrenic TPEs are used in a number of “Grip” applications including handlebar grips, toothbrushes, razors, golf clubs, and power tools.
Thermoplastic Polyurethane (TPU)
Thermoplastic Polyurethane is an Elastomer that comes in a variety of formulations so it can provide a considerable number of physical properties combinations making it an extremely flexible material that is useful in many types of customer applications. Thermoplastic Polyurethane (TPU) offers high resilience, resistance to impacts, and abrasions, and has good weatherability. TPU’s offer flexibility with a broad range of hardnesses (65 Shore A to 80 Shore D Durometer) and high elasticity — up to 750% elongation. TPU’s have good load bearing capabilities; are easy to process, can be sterilized, welded, colored, painted, and printed. Thermoplastic Polyurethane has good low temperature flexibility. Specialty grades can be transparent, flame retardant, and anti-static.
Thermoplastic Olefin (TPO)
TPO is a Thermoplastic Elastomer used in glass sealing channels; garden and appliance hosing; tubing; electrical insulation, and roofing membranes. TPO’s are water resistant, have fair tensile strength, good elongation capabilities, excellent low temperature flexibility, good to excellent weathering capabilities and good colorability. UV resistant specialty grades are available making it an excellent material for outdoor use but be careful with solvents, and fuels — oils, gasoline, kerosene.