FAQ
Acrylic & Clear Plastic
No, pricing on standard stock acrylic is typically 25% less expensive than the same sized piece of polycarbonate. Pricing can fluctuate based on availability to material and required size.
Extruded acrylic is less expensive than cast acrylic. Extruded acrylic will tend to have a grain in the direction of the extrusion which will affect the properties. Cast is acrylic is cast between glass plates and has better optical properties and surface quality. Thickness tolerance is tighter with extruded and extruded acrylic cements easier. There is greater strength and weather resistance with cast acrylic.
Extruded acrylic typically costs less, has a higher gloss finish, better scratch resistance and is more transparent than polycarbonate. Polycarbonate is virtually indestructible. Both are much lighter in weight than glass and more impact resistant (acrylic 17 times more and polycarbonate is 250 times more). Neither acrylic nor polycarbonate will shatter. Both can come in bullet-resistant grade, however, the polycarbonate can handle higher caliber.
No, there are no grades of clear plastic sheet that are considered “bullet proof.” There are laminated grades of both polycarbonate and acrylic that are UL-approved to withstand ballistic assault based on caliber of weapon and grade of ammunition. These materials would be considered bullet resistant or ballistic-grade.
It is not recommended to use household glass cleaners on plastic materials is it typically contains ammonia and other chemical additives which harm and slowly deteriorate the material (commonly called crazing). Ammonia specifically will damage the surface and compromise the transparency of an acrylic sheet. Mild soapy water applied with soft cloth and rinsed with plain water is the safest and most effective method of cleaning acrylic.
Clear face shield parts are commonly made from a .020 to .040 inch thick piece of polycarbonate, PETG, acetate or acrylic. The material is often die-cut or routed into shape. Thinner, disposable face shields are available.
Acrylic is inherently UV resistant, blocking approximately 93% of UV light. There are grades of acrylic with UV additives allowing the material to block as much as 99% of UV light.
A standard size sheet of acrylic is 48 x 96 inches (4 x 8 feet) and cost will depend on the thickness of the sheet. An approximate price for a quarter-inch thick sheet of clear extruded acrylic is $100. Price will vary based on exact product, color, quantity ordered, shipping and other common factors.
Display cases are typically made from 5 clear acrylic panels and sit on a metal, colored plastic or wood base. Acrylic can be cut with standard wood-working equipment. Thinner gauges can be scored with a knife. A solvent-based cement specific for acrylic should be used to bond the panels together. Acrylic panels can also be bent by heating the material to approximately 200 degree F.
Thin gauge acrylic can be scored with a knife. Thicker gauge acrylic can be cut with standard wood-working tooling, both hand-held and electric. Carbide blades are recommended.
Multi-wall material, also called twin wall or corrugated, in either acrylic or polycarbonate is a popular material for greenhouse manufacturing due to its light weight, impact strength, relative low cost and formability. The sheets can be connected using H channels, tape, nails or screws.
A light diffusing panel is commonly made from acrylic and used as light fixture covers, dispersing the light transmission evenly from the source, reducing or eliminating hot spots of light. These are needed more than ever since the advent of LED lighting. Eggcrate-pattern polystyrene is also commonly used in lighting applications.
Most acrylics will allow light of wavelength greater than 375nm to pass through. However, UV wavelengths are lower (e.g. UV-C is 100-290 nm) and will not pass through acrylic. HDPE products can include a UV inhibitator, making it ideal for outdoor application such as patio furniture and in boats.
Plexiglas is a brand of acrylic and a term commonly used to describe a clear plastic sheet. There are many brands of acrylic products including Lucite, Optix, Chemcast, Polycast and ACYRLITE.
Clear acrylic sheets are a common product and available through hardware stores, online merchants and plastic material distributors. Most major cities have several plastic distributors in the region that shock 48×96 inch sheets of clear acrylic and typically offer cut-to-size and pick-up services. Plastic distributors typically sell to the general public.
FAQ
Plastic Used in Specific Applications
Many plastics are FDA grade, meaning they can be used in food handling and processing applications. Virgin polyolefins like HDPE, LDPE, polypropylene and UHMW include FDA grades. There are food grades of Nylon and Acetal; however, these materials are subject to degradation due to chemical washdowns. PET is also approved and commonly used in food contact applications.
For a material to be approved for use in aerospace applications, it must be tested against and meet FAA and industry regulations for flame, smoke, toxicity and performance when exposed to temperature, pressure and chemicals. Polycarbonate, PVC/acrylic polymer blends, acrylic, phenolic, PTFE and PEEK are just a few thermoplastics commonly utilized for aerospace applications.
The two most common materials for aquarium construction are cast acrylic and glass. Cast acrylic, while typically more expensive than glass, is lighter in weight and more impact resistant than glass. Aquarium manufacturers prefer cast acrylic because it can be more easily formed into shapes. PVC is commonly used for aquarium bottoms.
Thickness of the acrylic depends on the size of the aquarium being made, as well as the method of construction. An aquarium thickness calculator should be used. In general, in water applications which expose acrylic to continuous stress, 750 psi the maximum stress recommended.
Hurricane storm panels made of polycarbonate, as well as multi-wall polycarbonate, are the most cost-effective protection. They can be stored conveniently and don’t require a lot of space when not being used. There are versions that meet stringent building and insurance codes in geographical areas prone to hurricanes.
Polycarbonate is virtually unbreakable and used to protect business storefronts and windows from possible debris caused by storms, vandalism and riots. Clear polycarbonate panels will not crack when impact an object such as a branch, brick or bat. Polycarbonate is lighter and stronger than plywood.
UV stabilized materials like high density polyethylene (HDPE) and acrylic are the most common. HDPE is very strong and weather resistant. Unlike wood, it will not absorb water which leads to rotting and delamination. Acrylic is used for table tops for patio furniture due to its excellent UV properties.
The most common plastic filaments used in 3D printers are ABS and PLA thermoplastics and both are similar in cost. ABS offers better mechanical properties while PLA is better in design application where finished appearance is vital.
The exterior shell of a standard American football helmet is made from injection-molded polycarbonate. The polycarbonate shell is lightweight and impact resistant. The interior padding is commonly polyurethane foam wrapped in a vinyl casing. Clear plastic visors are typically made from polycarbonate.
The two most common materials used to make panels on a transparent drum shield are acrylic and polycarbonate. Acrylic is typically less expensive, more scratch resistant, offers better transparency and a better gloss finish. Polycarbonate is virtually unbreakable and more common if the drum shield is being handled often. The panels are typically connected with a living or piano hinge.
Composite lumber is commonly comprised of recycled wood and plastic. From wood, it can come from saw dust, chips and other scrap. Post-consumer recycled plastic products, such as bottles and grocery bags, can be used in composite products.
The most common material used for golf cart windshields is impact modified acrylic. The material offers a high level of light transmission, impact resistance and formability. For enclosed golf carts, acrylic is also UV resistance with standard grades blocking approximately 93% of UV rays. Polycarbonate and hard-coated polycarbonate are also used.
UHMW liners are available through Quadrant, Polymer Ind and Rochling. Most of these manufacturers have their own brand, like Quick Silver, and also have their own divisions that will take business direct, so be careful. Disposable liners for dirt hauling can be PE, usually at least 6 mil thick. Urethane spray coats are available as well.
HDPE, PVC and expanded PVC have been utilized as plywood substitutes in boat construction and repair applications. HDPE in particular is ideal because it will not absorb water and can be infused with UV inhibitors. HDPE is commonly used instead of (or to replace) teak on boats.
The most common and inexpensive material is melamine, which is laminated to a wood substrate. Melamine is prone to ghosting and degrades quickly. Other dry erase boards are made from coated acrylic, porcelain, glass and metal.
Contact a local plastic distributor and fabricator with the windshield specifications. They can replicate the design, including bends and curves, of an existing boat windshield and provide a ready-to-install piece. Plastic distributors typically have the material on hand with machining capabilities to handle spot orders.
What does that triangle symbol on the bottom of a plastic milk jug or detergent container stand for?
It is a RIC (resin identification code) numbered 1-7 and each number has a specific category of plastic for recycling purposes. For example, 1 is for PET, used to make bottles and containers for soft drinks, beer, mouthwash, peanut butter, etc.
FAQ
High Performance Engineering Thermoplastics
Nylon 6 is cast nylon. Nylon 6/6 is extruded. Nylon 101 is a brand-name of Nylon 6/6 (sometimes typed Nylon 66). Nylon 6/6 has the best resistance to chemicals, like gasoline and oil, better for machining, has lower water absorption and higher melting point. Nylon 6 has high molecular weight and improved dimensional stability due to the cast process. However, tolerance in thickness and/or diameter is not as tight as the extruded product.
It is not recommended to use adhesives on polyethylene as the material is inherently resistant to glues and other adhesives. It is recommended that polyethylene be mechanically fastened or welded.
Carbide tooling is recommended for machining nylon. If sawing a wide tooth blade should be used. If turning on a CNC lathe use high speeds of 600 to 900 ft/min.
For the healthcare industry there are two heat sterilization methods used on plastic: steam autoclave and dry heat. Steam autoclave is the most common. Plastics with service temperatures above 270-degree F are required, but dry heat sterilizers can be considerable higher. There are a number of polymers suitable for steam autoclave sterilization including PEEK, PPSU PSU, some acetal copolymers, PEI, HSPP (heat stabilized polypropylene), and a few others. Service temperature is key, and it is always recommended to test the process before a final decision is made as to which plastic is most suitable.
Delrin is a trademarked name for acetal resins, which are semi-crystalline thermoplastic resins. Acetal is appropriate for high wear applications and excellent for moist or wet environments. Acetal products excel in pumps, valves, and food processing equipment.
Ultem is an amorphous thermoplastic that is characterized by its amber to transparent appearance. It exhibits excellent impact strength, heat, solvent and flame resistance, mechanical properties and machinability.
Teflon is a DuPont trade name for PTFE which stands for Polytetrafluoroethylene. PTFE is one of the best materials for applications in the electric industry. It is also a very slippery material and the reason why many frying pans have a PTFE coating.
Kevlar is a tradename of a synthetic fiber material created by DuPont. Kevlar is a plastic product with a chemical structure of poly-para-phenylene terephthalamide.
While it is difficult for plastics to achieve the strength of metals, some modified plastics actually have better strength when comparing weight ratios. The most common of these would be carbon-filled or reinforced plastics. A good example would be 60% woven carbon fiber filled PEEK, whose strength vs. its weight is greater than most metals. Many of us have seen prosthetical legs used by amputees, particularly athletes, with curve-shaped blades at the bottom to simulate the feet. These can be made of metal or a woven carbon-fiber filled polymer (PEEK or an epoxy are common). Both do very well, but because of the lightweight characteristics of the plastic, it is preferred over metal. Thin cross-sections of these reinforced polymers also exhibit great flexibility.
A standard tolerance is +/- .060. Many factors play a role in determining a true tolerance for a part including, and more importantly, the material being cut.
Both are in the olefin family and semi-crystalline. UHMW is an ultra-high molecular weight polyethylene and because of that it has the best coefficient of friction and wear properties of most standard plastics. HDPE can be heated and bent and heat formed and welded. UHMW can be heated and bent in some instances, but this is not standard due to the high molecular weight. UHMW has the best coefficient of friction and wear properties of most standard plastics due to its molecular weight. UHMW is a denser polyethylene and preferred for parts in sliding applications where overcoming friction is critical. UHMW is easier to machine but offers better wear and abrasion resistance and lower coefficient of friction.
Phenolics are thermoset materials, as opposed to thermoplastics, which means the only way to change its shape is to machine it. Thermoplastics shape can be changed by heat. Phenolic materials come in many different grades, like X, XX, XXX, XP, C, CE, L, LE and than all the glass filled grades G3, G5, G7, G9, G10, G11. All are thermoset and all have different properties. The green panel inside many of today’s electronics is a phenolic grade material known as G10.
Yes, most plastics are waterproof. There are some porous material made, but most are waterproof due to the way the polymer chains form together.
Do not cut fluorine- or chorine-based material in a laser cutter. It will damage the equipment and it will emit dangerous fumes into the air. Before cutting a material, consulted the manufacturers SDS sheet to confirm material makeup. Materials that are commonly cut with a laser cutter are acrylic, acetal, polyester and polypropylene.
Virgin plastic is the manufacture of product using direct resin that has never been used or processed before. Reprocessed (often called repro or regrind) is plastic made from either post-consumer or post-industrial recycled material and may contain higher levels of contaminants, which might yield imperfections.
Metal detectable PEEK, Nylon, UHMW, Acetal are produced in blue to differentiate them from their standard versions. This helps to avoid using a costlier product where it isn’t needed. The color also lends another layer of protection because it makes it easier to see shards that break off in food processing applications.
USP Class VI is a designation that determines the biocompatibility of a material for use in medical devices. In plastics, Class VI compliant materials are commonly referred to as implantable grade (long term and short term), such as PEEK.
Amorphous have no patterned order. Semi-crystalline have closer patterned and tighter packed molecules. Amorphous have lower melt points and heat resistance. Most see through plastics and formable plastics are amorphous. Semi-crystalline have higher heat resistance, are more opaque and have higher dimensional stability. Most engineering plastics fall into the semi-crystalline category.
A common way to identify a plastic material is through a flame test. The color of flame, odor, if it continues to burn after removal of heat source and whether it drips can all be used to identify the material. For instance, Nylon 6/6 burns blue, may smell like burnt hair and will drip. Acetate burns yellow, may smell like vinegar and will not drip. Also called a burn test, there are tables available online that break down the various burn characteristics.
Less than one and one is the specific gravity of water. PE and PP will float because they are lighter than water.
Tg stands for glass transition temperature. This is the temperature where the properties of the plastic start to degrade. For thermoplastics, the Tg is where the material starts to get soft and rubbery. When selecting a thermoplastic for a specific application it is important to consider its Tg, as well as heat deflection temperature.
High density polyurethane board (HDU) is a closed-cell foam board available in large blocks and sheet thicknesses and used for larger-scale prototypes, models and proof-of-concept designs of vehicles, furniture, boats, appliances and other equipment. The material can be machined to close tolerances, giving a design a light-weight, real size, low cost finished part. HDU is considered easier to work with than MDF (medium density fiberboard).
The use of nylon as a bearing and/or bushing means part does not need external lubricant. Nylon has a low co-efficient of friction as well.
Acetal homopolymer (Delrin) can have centerline porosity due to the material cooling while being manufactured. The outside cools first, creating a line or small voids in the center of the material. This can result in gas leakage in an application or creates an environment where bacteria can grow in food processing or medical applications. Acetal copolymer typically does not have centerline porosity.
