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27 Nov
0 15 Post by

WHAT IS CREEP?

Creep in polymers, also known as cold flow, it is the tendency of a material to slowly undergo deformation when constant mechanical stresses are applied. These stresses include tensile, compressive, shear or flexural loading. If a plastic is under constant stress, a constant change in strain will occur.1 Thus the stressed polymer will continue to deform over time. It will occur even if the stress is below the yield strength of the material.

Materials will experience greater creep if they are exposed to heat for long periods of time. So the rate of creep depends on the stress applied, temperature and the material involved. Glass, metals, polymers, ice etc. all experience creep but at different rates and temperatures. The ice in glaciers flows slowly down a slope because of creep. There is slippage between and within the ice crystals. It is important to note that high temperatures are not required. Materials also creep under ambient temperatures.

VISCOELASTICITY

Polymers are viscoelastic. That is they have the properties of both fluids and elastic solids. This is because plastics are made up of long molecules that get entangled with each other. Also the polymer chains are mobile and can slide past each other.

PLASTIC FLOW

Creep is not the same thing as plastic flow. It is the deformation of a polymer under a small constant load. Plastic flow occurs when there is fast deformation of a polymer under a high constant load.

POLYMERS THAT RESIST CREEP

Crystalline polymers are more creep resistant when compared to amorphous polymers. This is because they have a higher degree of secondary bonding. Polymers with more chain entanglement are also more resistant. Additionally glass fibers added to a polymer will increase entanglement and this will lower creep.

EXAMPLES OF POLYMERS THAT EXHIBIT LOW CREEP

Vespel®: Excellent strength and impact resistance. It has low rates of wear and friction. Vespel® is thermally resistant and maintains its mechanical properties in temperatures as high as 260°C (500°F.) It has exceptional creep resistance.

PAI: (Polyamide-imide) Also known as Torlon® it is an extremely strong, stiff and dimensionally stable polymer. It is often used in high temperature applications as it can perform in continuous temperatures up to 260°C (500°F.) It is used when a tight tolerance plastic is needed as its has extremely low thermal expansion and excellent creep resistance.

PEEK: (Polyetheretherketone) An engineering plastic known for its mechanical strength and dimensional stability. It performs well in harsh chemicals. PEEK has a continuous service temperature of 170°C (338°F.)

ECTFE: (Halar®) has greater strength, abrasion resistance, and creep resistance than other fluoropolymers that are softer such as PTFE (Teflon®.) Additionally it has excellent mechanical properties, dimensional stability and is fire resistant. The surface of ECTFE is exceptionally smooth making it ideal for high purity applications.

1 Stress is the force applied to a material, divided by the material’s cross-sectional area. Strain is the deformation or displacement of material that results from an applied stress.

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Categories: Fasteners, Material, Plastic Material
tpu Isoplast®-plastic
15 Nov
0 48 Post by

by Barbara Gerard

Thermoplastic Polyurethane (TPU)

Thermoplastic Polyurethane plastic is used to make parts including TPU Isoplast® screws, hex bolts, hex nuts and many custom components. Because of its high strength and impact resistance thermoplastic polyurethane TPU Isoplast® is used when a rigid polymer is needed due to its high strength and impact resistance. Technically thermoplastic polyurethane is a thermoplastic elastomer made up of block copolymers which have hard and soft segments. Basically a TPU resin consists of linear polymeric chains in block-structures. Such chains contain rather long (called soft segment) chains alternating with shorter ones (called hard segments). Thus TPU is a bridge between rubber and thermoplastic resins.

Isoplast® 

TPU parts were originally used for medical purposes. It is sold under the brand name Isoplast® among others. The resin with 40% glass filled compares well with some metals. This product adds together the toughness and dimensional stability of amorphous resins with the chemical resistance of crystalline materials. Thermoplastic polyurethane (TPU) properties include elasticity and resistance to oil, grease, and wear. Additionally, it is resistant to sea water and ultra violet rays making it an excellent plastic for use in the oceans.

Strength

With a yield strength of 27,000 psi (186 MPa), TPU Isoplast® 40% added glass fiber has the strength of aluminum.  Also it has water and chemical resistance, low creep and UV resistance. Thus TPU 40% glass fiber is an ideal material for plastic parts such as custom parts, hex bolts, hex nuts and TPU Isoplast® screws. Additionally it is used in applications such as internal scaffolding products such as beam clamps, pipe hangers, post bases, pipe clamps, clevis hangers, channel nuts, U-bolts, and more.

Uses

TPU 40% glass filled Isoplast® has a wide variety of uses. For example, it is used to make medical devices such as healthcare mattresses, dental materials, medical device cables, and wound dressings. Also it is used in power tools, sporting goods, parts for cars, fire hoses, and drive belts as well as inflatable rafts and footwear. Additionally TPU Isoplast® is also a popular material for use in keyboard protectors and in the cases of mobile phones. TPU phone cases are flexible because the material has a high elasticity rate and absorbs shock. It is also an excellent material for this purpose because it can be dyed to a wide variety of colors.

Pros of TPU Isoplast®40% Glass-filled

  • high abrasion resistance
  • high mechanical properties
  • high chemical resistance
  • high shear strength
  • high elasticity
  • oil and grease resistance
  • good injectability
  • good adhesion strength
  • good low-temperature flexibility
  • TPU scrap can be ground and reused.
  • lighter in weight than metals
  • minimal creep
  • good in UV radiation
  • non-conductive

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Categories: Fasteners, Material, Plastic Material
TPU-Isoplast-plastics
09 Nov
0 69 Post by

Plastic parts are generally not known for their strength. Consumers often choose plastic parts for their good chemical and acid resistance. And also the fact they do not conduct electricity, and can perform well in the presence of water. However, despite this reputation, there are plastic materials that have all of the better known characteristics of plastics and yet rival the strength of metals. Plastics such as TPU Isoplast®, FR4/G10, and Polyarylamide or PARA are exceptionally strong plastics.

Does your application require strength as well as non-corrosive and non-conductive properties?   Check out the top three strong plastics for fasteners and custom parts.

1.      Thermoplastics Polyurethane TPU Isoplast®

Thermoplastic Polyurethane is an impact modified amorphous polymer*** with the chemical resistance of crystalline resins.  TPU has a low uniform shrink rate which allows minimal creep*.  TPU 40% glass filled plastic fasteners are significantly lighter than the same metal parts.  With an ultimate tensile strength of 27,000 psi (186 MPa), TPU 40% glass-filled is like aluminum.   Also it has strength, water and chemical resistance, low creep and UV resistance. Thus TPU 40% glass fiber is an ideal material for plastic fasteners such as hex bolts, hex nuts and TPU screws. It is also used in applications such as internal scaffolding products, beam clamps, pipe hangers, post bases, pipe clamps, clevis hangers, channel nuts, U-bolts, and more.

TPU 40% glass filled is sold under the brand name Isoplast®, among others.

2.       FR-4/G10

FR-4/G10  is a composite material made up of woven fiberglass cloth and an epoxy resin.  This combination gives the laminate good strength to weight ratios.  Typical physical and electrical properties of FR-4 are expressed by LW (length wise, wrap yarn direction), and CW (cross wise, fill yarn direction).   LW and CW refer to fiber orientations that are perpendicular to each other. With a tensile strength of 45,000 psi  (310MPa), FR-4 plastic parts compare well to brass and aluminum.  Aluminum (Grade 6463-T6) has an ultimate tensile strength of 35,000 psi (241 MPA). While the number for free machining brass (Grade C3600)  is 50,000 psi (345 MPA). 

Also FR-4 plastic parts are flame resistant.  Flame resistant means that the parts are self-extinguishing according to the UL 94 test.  G10 plastic parts are not flame resistant. Thus they are no longer commonly used, although they are still used in applications where thermal destruction of the material is desired.  FR-4 epoxy resin often uses bromine, a halogen, to give the material a UL 94 V-0 flammability rating.  With flame retardant and near zero water absorption, FR-4 plastic fasteners retain their high mechanical strength and electrical insulating qualities in both dry and humid conditions.  FR-4 is not available in an injection molding grade but rather in sheets, plates and rods.

FR-4 is the insulating backbone of printed circuit boards (PCBs). Also it is also used for screws, bolts, nuts, switches, standoffs, threaded rod, transformers other parts that require strong plastics.

Ultimate Tensile Strength

MaterialMpaPSI
FR-4/G-1031044,960
PARA (50% glass-filled)23033,358
TPU (40% glass-filled)18629,977
Magnesium (Grade HK31A-T6)22532,633
Brass (Grade C3600)34550,000
Zinc Alloy28040,610
Aluminum (Grade 6463-T6)24135,000
Steel33047,862

3 .     Polyarylamide (PARA)

Polyarylamide (PARA) contains a base resin that has lower and slower water absorption than typical polyamides.  This resistance to water absorption is found in PARA’s semi-aromtic structure.  Polyarylamide compounds containing glass fiber result in plastic fasteners that have very high rigidity, excellent surface quality, extremely low creep* and high dimensionally stability.  Also PARA material containing 50% glass can stand up to a variety of chemicals including those used in the automotive industry.

PARA 50% glass-filled plastic parts have an ultimate tensile strength of 34,000 psi (230MPa). These parts made of strong plastics are often used to replace metal. It is available in a wide variety of colors. Thus PARA is often used in covers for cell phones and other electronic devices. Also it is used in aircraft and automotive applications as well as in furniture, small appliances, power tools, camera parts, gears, handles, hinges and knobs.

PARA 50% glass-filled is sold under the brand name of IXEF®, among others. 

*Creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses.

**An impact modified polymer is one whose impact resistance and toughness has been increased by the incorporation of the phase microdomains of a rubbery material.

*** An amorphous polymer has a molecular structure that lacks a definite repeating form.

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Categories: Fasteners, Plastic Material
Peek Fasteners
30 Oct
0 74 Post by

Chemical resistant plastics are often called for in many engineering applications such as custom parts and fasteners. These include screws, bolts and hex nuts.  Not all plastics will hold up well in extreme environments.  You should always do testing to ensure that you make the right material for your specific application. But there are certain plastics that tend to hold up well in chemically harsh environments.

When considering a chemical resistant plastic, check which industries commonly use the material.  Certain industries have a high demand for chemically inert materials. These include the semi-conductor processing equipment, medical, food processing, and chemical processing industries   We would like to to guide you in the right direction. Thus we’ve put together a list of the top four commonly used chemically resistant plastics.  And the winners are…

1.) Kynar® (PVDF)

PVDF resins have excellent resistance to temperature, harsh chemicals and nuclear radiation. They are used in the power, renewable energies, and chemical processing industries.  Also it is used in the pharmaceutical, medical, food & beverage and semi-conductor industries for its high purity. And PVDF is available in multiple forms.  PVDF is also one of the most popular chemical resistant plastics in the mining, plating and metal preparation industries.  This popularity is due to PVDF’s resistance to hot acids in a wide range of acid strengths.  PVDF is also used in the auto and architectural markets for its chemical resistance and excellent resistance to UV degradation and extreme weather conditions.

2.) PEEK

PEEK has superior strength and chemical inertness. Thus it is one of the best chemically resistant plastics for medical implants and orthopedic surgery.  PEEK exhibits excellent mechanical and thermal properties, as well as creep resistance at high temperatures, very low flammability, hydrolysis resistance, and radiation resistance. These properties make PEEK a preferred product in the aerospace, automotive, telephonic, and chemical processing industries. PEEK is used for wear and load bearing applications such as valve seats, pump gears, and compressor valve plates.

3.) PVC

Due to its wide use as indoor and in-ground wastewater piping, thousands and thousands of tons of PVC are produced every year, making PVC the third most produced plastic.  PVC is  used in construction as it’s more effective than traditional materials such as copper, iron, or wood.

PVC can be made softer and more pliable with the addition of plasticizers.  In this form, it is used in clothing, rugs and furniture.  PVC’s status as a chemical resistant plastic makes it an ideal material for window and door frames, insulating electric cables, outdoor signs, sports equipment, medical tubing, for floors, green houses, and outdoor playgrounds.

For those of you with an eye for trivia, a fun fact is that one of PVC’s early uses was in vinyl records.  PVC has good flexibility, is flame retardant, and has good thermal stability, a high gloss, and low (to no) lead content.  Polyvinylchloride molding materials can be extruded, injection molded, compression molded, and blow molded to form a huge variety of products.

4)      CPVC

CPVC resin is made by the chlorination of PVC resin and is used mostly to produce piping. CPVC shares many properties with PVC, including low conductivity and excellent corrosion resistance at room temperatures.  The extra chlorine in its structure also makes it more resistant to corrosion than PVC.  Whereas PVC begins to soften at temperatures over 140°F, CPVC is useful to temperatures of 180°F. Like PVC, CPVC is fire-retardant.  CPVC can be easily worked. It can be used in hot water pipes, chlorine pipes, sulfuric acid pipes, and high-pressure electric cable sheaths.

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Categories: Fasteners, Material, Plastic Material
Plastic Threaded Rod
04 Oct
0 117 Post by

What is Plastic Threaded Rod?

Plastic threaded rod is a bar of round plastic material threaded in a helical structure. It is used to convert between rotational and linear movement or force. Thus, it creates a strong resistance to pressure and tension. The direction of the rotation the rod creates depends on whether it has a right hand thread or a left hand thread.

What is Plastic Threaded Rod Used For?

It is used to align support systems. Plastic threaded rod can be embedded in materials such as concrete, wood or metal to create a steady structure during construction as the threads provide good resistance. It is used in support systems in the construction industry, However it is also used in plumbing, manufacturing, medical implants, marine, agricultural, oil extraction, stone cladding and contractor work.

Threaded rod is also used when the structures that need to be held together are further apart then even the longest bolt or screw. Sometimes coupling nuts are used to connect long lengths of plastic threaded rod. It is also used to make bushings, seals, set screws and other plastic parts. And it is used in construction projects and conveyor systems. Additionally, plastic threaded rod can be used to make gear wheels, cams, bearings and rollers.

Materials

Threaded rod is often made from metals. However, in some applications plastic threaded rod is a better choice. Some of these polymers include PEEK, Nylon, Vinyl Ester, Acetal/Delrin, and PTFE (Teflon.)

PEEK

PEEK is often used for medical implants in the human body. In medicine it is seen as an advanced bio material. Unfilled PEEK can be more easily removed than metal implants.

PEEK also is radiolucent. This is the ability of a material to allow a large amount of x-rays to pass through it thus producing darkened images on x-ray films. Radiolucency permits a surgeon to better monitor the healing progress following a surgical procedure. Also, it is MRI compatible.

Nylon

Nylon plastic threaded rods made are used in electronics as it is both nonmagnetic and noncorrosive. It has high tensile strength and can bear hundreds of kgms of weight. Additionally, it is resistant to flame, sparking and many chemicals. And relative to many other types of plastics, it has a high melting point. Nylon rod is used in refrigerator installations. It is also light weight. This makes it ideal for use in furniture. Nylon rods are sturdy and less expensive.

PTFE (Teflon)

Threaded rod made from PTFE is notably less strong than other plastic rods. Like most plastics it is an excellent electrical insulator. And nothing sticks to PTFE plastic rod. Even a gecko cannot hold on. It is inert to most acids and bases as well as most organics. Additionally, it performs well in mixed chemicals and hydrofluoric acid. Hydrofluoric acid is used in the photo-resist process in semi-conductor manufacturing. When compared to other plastics, PTFE threaded rod performs better in corrosive environments at high temperatures.

Vinyl Ester

Threaded rods made from vinyl ester are both water and chemical resistant. They are light weight and do not conduct electricity. Vinyl ether is higher in strength and more durable than nylon. It can even be stronger than some metal threaded rod.

Acetal Homopolymer and Copolymer

Acetal threaded rods are good for wet environments. Nylon absorbs water as does fiberglass rod. It is a relatively low cost material. Also it resists alcohol, many solvents and gasoline.

Plaastic threaded rod made from Delrin® acetal homopolymer is commonly used for gear wheels, cams, bearings, and rollers. The good electrical insulating and dielectric properties of Delrin® make it an excellent choice for electrically insulating components.

Ultem®

Plastic threaded rod made from Ultem® is not as commonly used as the others named above. However, it is microwave clear. If that is a requirement of your application then this material is the answer.

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Categories: Fasteners, Plastic Material
acetal-plastic-screws-nuts
22 Sep
0 144 Post by

ACETAL POLYOXYMETHYLENE

Acetal plastic is an engineering thermoplastic. It is often used to make a variety of custom parts as well as acetal plastic screws, hex bolts, hex nuts as well as other parts. Polyoxymethylene or POM is another name for Acetal. POM is used in precision parts that require high stiffness, low friction, and dimensional stability. POM is known for its high strength when exposed to temperatures from -40 degrees C to 80 degrees C. Natural POM is an opaque white material. However, it is easy to dye it to any color.

It has a high crystalline composition. And Acetal Plastic is available as a homopolymer and a copolymer. Different chemical companies sell POM under different names. These include Delrin®by DuPont and Celcon® by Celanese. However, it is not UV resistant. POM does not perform well in the rays of the sun. Additives are required when the material is exposed to UV rays.

ACETAL COPOLYMER VERSUS ACETAL HOMOPOLYMER

Acetal copolymer and homopolymer are two types of POM. Although these are very similar, they are not exactly the same material. The difference is in the structure of each. Acetal homopolymers have chains made of one monomer. However acetal plastic copolymers have chains made of two different monomers. For many applications, either will perform well. This is because most properties of the two materials are within 10% of each other. However, there are important differences.

CHARACTERISTICS OF ACETAL POM 

Both homopolymer and copolymer POM has the following characteristics:

Pros

  • Creep resistant
  • Excellent mechanical stability
  • Good electrical insulating and dielectric properties
  • Strong, rigid, and tough
  • Excellent moisture resistance, low water absorption
  • Low coefficient of friction, high lubricity
  • Chemically resistant. Mostly unaffected by solvents and fuels.
  • Low thermal expansion
  • High stiffness and hardness, therefore a good alternative to metals
  • FDA approved
  • Easily machined and molded
  • Easy to color

Negatives

  • Acetal cannot be painted.
  • Flammable and heat sensitive
  • Does not adhere well to other objects due to high lubricity
  • Acetal copolymer is a semi-crystalline thermoplastic. Importantly, the copolymer has the advantage of reduced centerline porosity. In addition,  the copolymer has better chemical properties. It has good pH resistance from pH 4-9. It is hydrolysis resistant up to 60 degrees Celsius. The continuous service temperature in the air is 90 degrees Celsius. And the acetal copolymer exhibits higher out-gassing. It is available in natural and black. In addition, the copolymer is a little cheaper.

Copolymer

Acetal copolymer is a semi-crystalline thermoplastic. Importantly, the copolymer has the advantage of reduced centerline porosity. In addition,  the copolymer has better chemical properties. It has good pH resistance from pH 4-9. It is hydrolysis resistant up to 60 degrees Celsius. The continuous service temperature in the air is 90 degrees Celsius. And the acetal copolymer exhibits higher out-gassing. It is available in natural and black. In addition, the copolymer is a little cheaper.

Homopolymer

Acetal homopolymer is a crystalline thermoplastic. Thus, it is the ideal material to replace metal parts. However, the negative side of the homopolymer is that it exhibits centerline porosity. However, generally the homopolymer has better mechanical properties:

  • 15% higher stiffness and strength.
  • 10% better creep resistance
  • Higher Rockwell hardness rating
  • Natural grade is FDA, NSF, and USDA compliant
  • Higher tensile strength
  • Significant impact resistance

Why Use Delrin® (Homopolymer) To Replace Metals

Delrin® has high tensile strength as well as low friction, and high wear resistance. In addition, it has low creep, is resistant to warping, and is overall tough and durable. Delrin® has low moisture absorption and is chemically resistant to hydrocarbons, solvents, and neutral chemicals.

While acetal plastic copolymers exhibit some of these characteristics, it is the unique combination of properties that makes the acetal plastic homopolymer the right plastic to replace metals in some applications.

This is not to say that Delrin® is as strong as metals. It is not. However, Delrin keeps on performing in applications such as pump and valve components where parts are exposed to moist or wet environments. Metals may fail while Delrin® keeps on performing.

APPLICATIONS

Typical applications for POM include high-performance parts such as gears, safety restraints, bearings, bushings rollers, fittings, and electrical insulator parts. Many parts such as acetal screws, hex nuts, and washers, hex bolts and many other custom parts are made from this plastic. Also, it is used to make consumer products such as eyeglass frames, ski bindings, guns, and knife handles. Additionally, the consumer electronic industry uses Delrin® widely. And it is preferred by the automotive industry for use on car interiors. POM has high impact strength.

Parts, Prints, or Problems. Contact us at Craftech Industries, Inc.

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Categories: Fasteners, Material, Plastic Material
What Plastic Are Legos Made From
06 Sep
0 228 Post by

HOW IT ALL STARTED

Legos first entered our house about 4 years ago. It started with a present for the first birthday party that my son was invited too.  Afterwards it was only a matter of time before I gave in to my son’s pleas for a Lego set of his very own.  So I admit that, over the years, I have enabled my son’s Lego addiction.  Yes, you read that right, addiction.  A set of Legos with a remote control train set was my most recent enabling gift this past Christmas. 

SO WHAT POLYMER ARE LEGOS MADE FROM?

Eventually during one of my many attempts to tidy the “Lego Room,” I made a note to myself to find out which plastic material the Lego company uses.  Since I work in the plastics industry, I was naturally curious.  There are so many different sized bricks and colors, supporting parts, doors, windows, and figures in a variety of themes-a myriad of pieces beyond belief.  So I thought the design and manufacturing process must be impressive to say the least.  Here’s a brief rundown on the history of Legos and how they’re made. 

THE HISTORY OF LEGOS

A carpenter from Billund, Denmark named Ole Kirk Christiansen started making wooden toys in his workshop in 1932.  His company came to be called “Lego” in 1934 from the Danish phrase “leg godt.” This means “play well.” In 1947, the company expanded to producing plastic toys.  An early version of the now famous interlocking bricks started to be produced in 1949. 

By 1954, Christiansen’s son, Godtfred saw the immense potential in Lego bricks to become a system for creative play.  (I’d say hit a home run on that one. )  The modern brick design was developed in 1958. It addresses some limited locking ability and versatility.  But it took another 5 years to find the right material which was ABS.  In 1958, the modern Lego brick was patented.

ACRYLONITRILE BUTADIENE STYRENE OR ABS

Basically ABS or acrylonitrile butadiene styrene is the plastic used in the most modern Lego elements.  This is just one of the materials we are familiar with at Craftech, since we machine parts out of ABS bar stock and injection mold the resin form.  The butadiene component (a derivative of natural rubber) is largely responsible for the strength and impact resistance of this plastic. 

The modern formula for ABS was developed as part of the war effort in the mid-1940s.  Bayer AG, a German chemical company, had long been the exclusive supplier to the LEGO group.  It spun off most of its plastics business in 2004 into the newly-formed Lanxess AG.  Virtually all plastic used by LEGO is a proprietary version of Lanxess’ Novodur ABS, Makrolon polycarbonate (for transparent elements) and Macrolex dyes for coloring.   Variants of Delrin or nylon are used to make cloth and string elements.

HOW LEGOS ARE MADE

Legos are made by injection molding.  Basically silos of material are available with pipes that feed plastic granules to the molding machines.  Each silo holds up to 33 tons of granules.  The molding process is almost completely automated. The molding machines heat up the granules to a temperature of about 450°F (230°C).  The plastic is then fed into molds.  The machine applies hundreds of tons of pressure to make sure the bricks are shaped with perfect accuracy.  Then they are cooled and ejected. This takes about 10 seconds.  Finished pieces go down conveyor belts into boxes. 

PACKAGING

When the boxes are full, a radio signal is sent by the molding machine to robot trucks that patrol the hall.  The robot trucks are guided by grooves in the floor.  After that the boxes are brought to an assembly hall where a giant printer stamps decorative details on faces, control panels, numbers, and words.  Finally the last step is to put the right components together to make a LEGO set.  Boxes, called “cassettes,” roll on conveyor belts underneath the bins that hold each type of piece.  And the right number of pieces is automatically released into each cassette.  Afterwards the package operators close the boxes and add additional pieces and building instructions. 

CONCLUSION

So now I feel a little more enlightened about this product and what it takes to get it on the shelf.  After all I may have this product in my house for a few more years, since son #2 has already been hard at work adding to his brothers’ masterpieces.

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Categories: Plastic Material
that plastic part is made of what material?
09 Aug
0 400 Post by

You have a plastic part in your hand. How do you determine what plastic it is made of? Here are four good places to start:

  • Plastic Resin Identification Codes
  • Burn Test
  • Floats or Sinks in Water
  • Unique Appearance

PLASTIC RESIN IDENTIFICATION CODES

The plastics identification codes were developed in 1988 by the SPI Society of Plastic Industries. These codes are intended to be recycling codes. #1 is polyethylene terephthalate (PETE, PET), and #2 is high-density polyethylene (HDPE). #3 polyvinyl chloride (PVC), #4 low-density polyethylene (LDPE), #5 Polypropylene (PP) #6 Polystyrene (PS) while #7 Misc. includes polycarbonate (PC), nylon, ABS, acrylic, and polylactic acid (PLA).

Indeed knowing what object you have is an important clue to knowing what plastic it is made from. For example, if you are holding a milk jug the material is probably high-density polyethylene. But a plastic container that once held laundry soap and most colored containers are also made of HDPE. Often trash bags are made from low-density polyethylene.

However if the object has a code molded into it or written on its label, you will know what plastic it is made of for sure. For example, the objects below are coded number five, so we know they are made from polypropylene. And of course, a Styrofoam cup will usually have a 6 on the bottom of it.

THE BURN TEST

The burn test is another way to get information about what plastic a part is made of. It is important however that this test be performed in an industrial setting with the correct equipment as some burning plastics can release carcinogens. Also, molten plastics are very hot, and some will drip. Heat the plastic with a lighter until it burns using the proper ventilation equipment.

MaterialOdorColor of
Flame		DipsFloats in Water
ABSacrid. black
smoke w soot		orangenono
PETE, (PET)light smokeyellowyesyes
PTFEburnt hair——-nono
Nylonburnt wool or
hair		blue, yellow
tipped		yesno
Polycarbonatefaint, sweet
aroma, black
smoke w soot		orangeyesno
Polyethylenecandle waxblue, yellow
tipped		yesyes
Polypropylenesweet odorblue, yellow
tipped		noyes
Polystyrenegas odor,
(naptha)		yellow, black
smoke		yesno
PVChydrochloric
acid		yellow w green
spurts		nono
Polyestershydrochloric
acid		yellownono

FLOATS OR SINKS IN WATER

Plastics all have a particular density. Not all plastics float on water. If the density of the material is greater than water, it will sink. If it is less dense, it will float. We have all read about the amount of plastic waste floating in the earth’s oceans. The Great Pacific Garbage Patch in the north-central Pacific Ocean is the largest accumulation in the world. So it must be made of plastics that float on water. Sadly, not one square mile of the surface ocean is free from plastic waste.

PLASTICS THAT FLOAT

There are three plastics that float on water. And all have a density of less than that of water. These are HDPE, LDPE, and PP. See the chart below. Since plastics can vary in density when they are manufactured, there is a range of values indicated for each plastic.

Density Table (G/mL)

Water 1.00
(1) PETE (PET) 1.38-1.39
(2) HDPE 0.95-0.96
(3) PVC 1.16-1.35
(4) LDPE 0.92-0.94
(5) PP 0.90-0.91
(6) PS 1.05-1.07
(7) Others. Nylon 1.14, polycarbonate 1.2, acrylic 1.15, etc.

PLASTICS THAT SINK

To understand what plastic the object you are holding is made from knowing if it will sink in water is auseful. So higher-density plastics such as PET (polyethylene terephthalate), PVC (polyvinyl chloride), and PS (polystyrene), do sink. PETE (or PET) is used to make single-use plastic drink bottles. Since the density of PETE is 1.38-1.39 many of those bottles we use and do not recycle may wind up sinking to the bottom of the oceans.

PVC is made into sheeting, rope, blood bags, and medical tubing as well as siding and flooring to name just a few of its uses. After polyethylene, PVC is the most widely used plastic in the world. And PVC also sinks. Finally, polystyrene is made into hot cups and clam shells for hamburgers and other food we eat on the go. With a density of 1.05 to 1.07, PS will also sink.

NYLON

Most nylon produced is used to make clothing and carpet although all clothing and carpet are not necessarily made of nylon. But with a density of 1.14, it will sink. Additionally, if the smell the material gives off in the burn test is that of burnt wool, if the flame is blue with a yellow tip, if the molten plastic drips, and it does not continue to burn when the flame source is removed, what you have is pretty sure to be nylon.

TEFLON (PTFE)

Teflon (PTFE) is a polymer known for its chemical resistance and ability to withstand high heat applications. It also has a characteristic appearance. It is generally very white in color and has a waxy feel. Additionally Teflon is notably soft, so much so that you can use your thumbnail to make an indent in it.

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resin Identification codes
29 Jun
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Resin Identification Codes or RIC were first introduced in 1988 as the “Voluntary Plastic Container Coding System” by The Society of the Plastics Industry (now called the Plastics Industry Association). The intent was to make it easier to identify what plastic objects were made of. Thus the codes made it easier to know whether to either recycle or dispose of them.

However, since 2008 the codes have been administered by ASTM International, an international organization of standards. After that the original coding system became ASTM D7611-Standard Practise for Coding Plastic Manufactured Articles for Resin Identification. In 2013 the graphic for the various codes was changed from a number surrounded by a triangle of three chasing arrows to a number surrounded by a triangle.

Resin Identification Codes Numbers

The numbers for resin identification codes go from 1-7 with 1 being the easiest to recycle and 7 the least. So 1 and 2 can usually be recycled while 6 and 7 are usually disposed of. And for 3, 4 and 5… well that depends. Thus while an RIC code on a plastic object may mean it can be recycled, it does not necessarily means that nor does the absence of the code indicate it cannot be recycled.

Meaning of Resin Manufacturing Codes

The uses in this paragraph are original manufacture uses.

  1. Polyethylene terephthalate (PETE, PET): Soft drink bottles, tote bags, polyester fibers, thermoformed sheet, carpets, and furniture. Additionally, cold drink cups, peanut butter and salad dressing containers, and water bottles.
  2. High density polyethylene (HDPE, PE-HD): Juice and clear bottles, grocery bags, milk jugs, playground equipment, plastic lumber, trash can liners, butter and yogurt containers.
  3. Polyvinyl chloride (PVC): Pipes, siding, fencing, non-food bottles such as detergent containers. Also cooking oil bottles, toys, plastic floors, lawn chairs, clear wrap for food, bottles for window cleaner.
  4. Low density polyethylene (LDPE, PE-LD): Six pack rings, tubing, plastic bags, containers, and squeeze bottles as well as bread and frozen food bags.
  5. Polypropylene (PP): Auto parts and industrial fibers. Plates, bowls and cutlery, food containers. Also syrup and catsup bottles.
  6. Polystyrene (PS): Coffee cups and lids, as well as clamshell containers, egg cartons as well as packaging peanuts and other packaging materials.
  7. Other or O: Includes acrylic, nylon, polycarbonate, polylactic acid (PLA), and multiple combinations of different plastics. Bottles, safety glasses, food packaging, plastic lumber, headlight lenses.

Recycling

According to the United Nations Environment Program less than 10% of the plastic waste generated worldwide has ever been recycled.

  1. PET, PETE: These are recyclable and should be washed and dried before being put in your recycling bin. This plastic is turned into flakes and used to spin carpet fiber, fiberfill and tote bags.
  2. HDPE is very resistant to deterioration. These items should also be rinsed and dried before disposal. It is recycled into among other things plastic fencing, picnic tables and lawn chairs.
  3. PVC can break down into dangerous chemicals like vinyl chloride. It is reprocessed into items like traffic cones, garden hoses and floor mats.
  4. LDPE is considered a safe plastic for human food use and does not leach any chemicals. It is reprocessed into trash can liners, composite lumber and piping.
  5. PP is safe to be reused. All items should be rinsed and dried before putting them in your recycling bin. PP can be re-manufactured into brooms, bike racks, ice scrapers and bins.
  6. PS is lightweight and does not break down easily. Because of its light weight it takes a very large amount to recycle the plastic. Thus it is not economical for reprocessors to accept.
  7. As described above this is a group of plastics that are less used and therefore are not generally recycled.
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