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nylon-plastic-material-craftech
27 Sep
0 14 Post by

by Katie Gerard

Oh, nylon…the material of choice for so many.  It was invented in the early 1930’s by the chemical giant DuPont. This trusty polymer is an excellent material for a wide variety of applications.  For many first-time customers new to the vast world of plastics it tends to be the default choice. Nylon may seem like a safe multipurpose material pick. However, one must always carefully consider the requirements of a project when considering a material for plastic fasteners.

WHEN NOT TO CHOOSE NYLON

Even the popular nylon has weaknesses. The polymer cannot withstand extreme high temperatures and long-term contact with water and many organic solvents.  Nylon fasteners also do not perform well in applications that require low out-gassing, ultra-high strength, or clean and easy machining.  The polymer also does not cut crisply without the need for extensive cleaning.  As a condensation polymer, nylon fasteners cannot be left in water. The parts are highly absorbent even from just moisture in the air.

SO WHY NYLON?

With all these drawbacks, where did Nylon’s reputation as a top all-around plastic material come from?  Well, for one thing, it’s cheap!  Consider PEEK, a plastic that is much more chemical and heat resistant than nylon.  PEEK fasteners can tolerate temperatures almost as high as 500° F. However Nylon fasteners can only handle only around 300°F for short periods of time.  PEEK costs around $60 per pound while nylon only costs around $2.30.  Polyphenylsulfide (PPS) can also withstand high temperatures and only costs $10 per pound but is extremely brittle, even when reinforced.  For projects that do not require high levels of temperature and chemical resistance, nylon fasteners are the cost effective choice.

CHEMICAL PROPERTIES

Nylon also has certain useful chemical properties.  Fasteners made from this polymer are relatively easy to glue and can be colored almost any hue simply by using fabric dyes dissolved in hot water.  It can be permanently immersed in gasoline or motor oil without fear of corrosion, as it is excellent in and around many petroleum-based materials.   

There are also many special-use nylons which use a wide variety of processes and additives to alter and improve nylon’s natural properties.  For example,  fasteners made from this plastic can be made fire-resistant to the extent that they get a UL rating of 94-V0.  Its can also be modified to extend its continuous use temperature range.

ADDED FIBERS

Also, nylon is fairly strong. And with the addition of fibers such as carbon, glass and metal it can be made even stronger .  These fibers add strength and dimensional stability.

EASY TO MOLD

Nylon is also very easy to mold and becomes water-like when heated in a plastics extruder or injection molding machine.  This melting property has the benefit of letting the material be pushed into very small spaces.  The minimum annular distance between two plates for Delrin is forty thousandths. However the minimum distance for nylon is only fifteen thousandths.

All of these properties make nylon an alluring and cost-effective choice for the novice engineer.  Even when a few of the comparative factors are examined, there are still unique properties which make nylon fasteners competitive with respect to fasteners made out of other plastics.  Yet it is important to always pick your material to fit your project.   No single plastic can fit all applications.

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Categories: Fasteners, Material, Plastic Material
acetal-plastic-screws-nuts
22 Sep
0 33 Post by

POLYOXYMETHYLENE

Acetal is an engineering thermoplastic. It is also known as polyoxymethylene or POM. POM is used in precision parts that require high stiffness, low friction, and dimensional stability. POM is known for its high strength from -40 degrees C to 80 degrees C. Natural POM is an opaque white material. However, it can easily be dyed to almost any color. It has a high crystalline composition. And is available as a homopolymer and a copolymer. Different chemical companies sell POM under different names, including Delrin®by DuPont and Celcon® by Celanese. However, it is not UV resistant and additives are required to make it useful in the sun’s 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, while acetal copolymers have chains made of two different monomers. For many applications, either will perform well as most properties are within 10% of each other. However, there are important differences.

CHARACTERISTICS OF POM (ACETAL)

Both homopolymer and copolymer POM has the following characteristics:

  • 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
  • Does not perform well in Chlorine and thus is not for swimming pool use.


    Acetal 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.

ACETAL 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. 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® (Acetal 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 copolymers exhibit some of these characteristics, it is the unique combination of properties that makes the acetal 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 screws, hex nuts, and washers, hex bolts and many other parts are made of. Also, it is used to make consumer products such as eyeglass frames, ski bindings, guns, and knife handles. Additionally, Delrin® is used widely in the consumer electronics industry. And it is preferred by the automotive industry for use on car interiors because of its impact strength.

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

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Categories: Fasteners, Material, Plastic Material
09 Aug
0 178 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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Categories: Material, Plastic Industry
29 Jun
0 174 Post by

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.

Meaning Of Resin Identification Codes

The resin numbers 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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Categories: Material, Plastic Industry
07 Jan
0 140 Post by
PEEK or polyetheretherketone is a high-performance, engineered plastic. It is one of the materials of choice medical implants such as spinal replacement disks as well as trauma fixation. Trauma fixation is the repair of broken bones or any bodily injury that can result from force or violence applied to the human body.
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Categories: Fasteners, Material, Medical Industry
carbon-fiber-plastic
11 Mar
0 265 Post by
The use of carbon reinforced fibers in plastic materials has a long history.  As early as 1879, Thomas Edison was experimenting with carbon fibers made from cotton threads and bamboo slivers.  In fact, the first incandescent light bulb heated by electricity contained carbon fibers.
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Categories: Material, Plastic Material, Plastic News
01 Feb
0 208 Post by
Carbon Fiber Reinforced Plastics (CFRP) have long been used in high-performance race cars. However, the cost, as well as the manufacturing time of components, has made CFRP prohibitive for consumer applications. But that is changing.
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Categories: Material
06 Jul
0 212 Post by
Ultem® PEI is a semi-transparent high-temperature plastic. It is used to make custom parts as well as fasteners such as screws, hex nuts, washers, threaded studs, and spacers. It can be both molded and machined.
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Categories: Fasteners, Material
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