Another feature of polycarbonate is that it is very pliable. It can typically be formed at room temperature without cracking or breaking, similar to aluminum sheet metal. Although deformation may be simpler with the application of heat, even small angle bends are possible without it. This characteristic makes polycarbonate sheet stock particularly useful in prototyping applications where sheet metal lacks viability (e.g. when transparency is required or when a non-conductive material with good electrical insulation properties is required).
Now that we know what it is used for, let’s examine some of the key properties of Polycarbonate. PC is classified as a “thermoplastic” (as opposed to “thermoset”), and the name has to do with the way the plastic responds to heat. Thermoplastic materials become liquid at their melting point (155 degrees Celsius in the case of Polycarbonat). A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. Instead of burning, thermoplastics like Polycarbonate liquefy, which allows them to be easily injection molded and then subsequently recycled.
By contrast, thermoset plastics can only be heated once (typically during the injection molding process). The first heating causes thermoset materials to set (similar to a 2-part epoxy) resulting in a chemical change that cannot be reversed. If you tried to heat a thermoset plastic to a high temperature a second time it would simply burn. This characteristic makes thermoset materials poor candidates for recycling.
Polycarbonate is also an amorphous material, meaning that it does not exhibit the ordered characteristics of crystalline solids. Typically amorphous plastics demonstrate a tendency to gradually soften (i.e. they have a wider range between their glass transition temperature and their melting point) rather than to exhibit a sharp transition from solid to liquid as is the case in crystalline polymers.Lastly, Polycarbonate is a copolymer in that it is composed of several different monomer types in combination with one another.
EVA Feature: Soft, flexible plastic with low-temperature toughness and stress-crack resistance
Flexible EVA (ethylene vinyl acetate) is the copolymer of ethylene and vinyl acetate. It’s an extremely elastic material that can be processed like other thermoplastics. The material has low-temperature toughness, stress-crack and UV radiation resistance.
EVA IS WIDELY USED FOR:
Soft inner liners for rigid socket frames
Inner boots for pediatric AFOs
Orthotics for hand and wrist
Upper and lower extremity prostheses
FLEXIBLE (EVA) MATERIAL OPTIONS - OP-TEK® Flex, Duraflex®, Proflex, Orfitrans™ Excel
OP-TEK® Flex– is a soft, flexible EVA copolymer that provides for outstanding patient comfort (helmet) when used as a liner for rigid socket frames. OP-TEK® Flex is specially formulated to maintain more consistent walls during forming compared with many other flexible plastics.
OP-TEK® Flex Comfort– is a soft, flexible EVA copolymer with a proprietary additive that gives the material a softer feel. This enhanced surface provides superior patient comfort when used as a liner for rigid socket frames. The additive greatly reduces friction when patients don and doff prosthetic devices. Unlike EVAs with silicone, OP-TEK® Flex Comfort exhibits excellent seaming characteristics during drape forming and more consistent walls during blister/bubble forming compared with many other EVA copolymer materials.
OP-TEK® Flex BiLam– provides added comfort and improves aesthetics for patients wearing carbon socket frames. The inner layer contains a hypoallergenic, FDA compliant additive that reduces friction, and the outer layer helps hide trim lines and window cut-outs of carbon socket frames.
Duraflex®– is a soft, flexible EVA copolymer that provides patient comfort when used as a liner for rigid socket frames. Duraflex® is harder and a little more rigid than OP-TEK® Flex and Proflex. It is available in natural (semi-transparent) and black.
Proflex– is a soft, flexible EVA copolymer that provides a superior level of patient comfort when used as a liner for rigid socket frames.
Proflex with Silicone (Proflex-S)– is a soft, flexible EVA copolymer with a silicone lubricant. Like Proflex it provides a superior level of patient comfort when used as a liner for rigid socket frames. The silicone reduces friction when patients don and doff prosthetic devices.
Orfitrans™ Excel– is available in semi-transparent and black. The material pulls very easily and offers outstanding comfort for the patient.
Tech Tip– Be aware that certain solvents can cause cracks to propagate with EVA materials.
Q5. WHAT IS EPP?
EPP( Expanded Polypropylene) is an advanced protective system that's significantly lighter than the traditional foam inside most batters helmets. In fact. EPP is one of the lightest protective materials on the market. Yet, it doesn't sacrifice performance. Our EPP impact absorption liner is part of a three layer protection system in the helmets. It distributes the load and energy of impacts across the entirety of the helmet shell, effectively dissipating that energy away from the play The EPP impact absorption liner is uniquely formed and ventilated to maximize performance and air flow throughout the helmet.
Expanded polypropylene (EPP) is an engineered plastic foam material. By combining polypropylene resin with magic dust, and applying heat, pressure and CO2 in an autoclave, the material is formed into small plastic beads. These small, closed-cell foam beads are injected into a steam chest to create parts custom molded into complex shapes using steam heat & pressure.
EPP materials provide competitive advantages for designers and engineers looking to enhance custom molded parts.
• A variety of specialty grades & density ranging from 1.25lb. to 5.6lb. per cubic foot
• Available in a range of colors
• Unsurpassed quality / Material properties that outperform other comparable foam materials
• Lightweight with very high strength to weight ratio / highly durable
• Resistant to water, chemicals and most oils
• Resistant to temperature extremes from -35
EPP Helmet feature: Light; strong sturcture; Resistant to water; Resistant to temperature; Unsurpassed quality.