A Guide To Plastics
What Are Plastics?
Plastics are a type of versatile material that can be moulded into shape by applying heat.
All plastics are made up of a combination of chemicals which form a polymer, attributing similar but slightly different characteristics to each type of plastic.
For the most part, plastics are strong and durable. They are excellent insulators which means that they do not conduct heat or electricity.
As a result, many types of plastic are used to make precision engineering components that can be equal to, if not better than, metal for many applications.
What Is The Difference Between Thermoset and Thermoplastic?
During the curing process of a plastic, Thermosets and Thermoplastics will behave in different ways.
The primary difference between Thermoset and Thermoplastic can be identified by the materials ability to remould.
Thermosets, for example, create a chemical bond when they are cured. This reaction will set the material in place and make the plastic stronger.
As a one way reaction Thermosets cannot be remoulded or heated once they have formed.
Alternatively, for Thermoplastics a chemical bond does not form during the curing process; once set, these plastics can be remoulded again when necessary.
One benefit of Thermoset plastic is that it has a high melting point. This means that when exposed to fire, the plastic will burn rather than melt. For this reason, Thermosets are used as a protective measure in plug sockets over Thermoplastics which have a lower melting point.
When To Use Plastic Components
Due to its high machinability, durability and strength, metal is the most common material used in the manufacture of precision engineering components.
Nevertheless, plastic components can have a range of high-performance properties that make them great for specific applications.
In comparison to some metal components, plastic components are the more cost-effective option whilst still having an excellent strength-to-weight ratio.
Where metal fasteners may begin to rust with time, plastic components are not prone to the same degree of degradation and, as a result, may be better suited to some marine or moisture rich applications.
Alongside metal fasteners, plastic components such as Shoulder Washers can be used as insulating implements. This helps to break the electrical connection between metals and thereby reducing the risk of galvanic corrosion occurring.
More information on this can be found in our article looking at What Causes Galvanic Corrosion And Ways You Can Prevent It.
How Many Types Of Plastics Are There?
Whilst the total number of different plastics is enormous, broadly speaking, they can be filtered into 7 categories. These are defined by the materials characteristics, recyclability and their ability to be reused.
1. Polyethylene Terephthalate (PET)
2. High Density Polyethylene (HDPE)
3. Polyvinyl Chloride (PVC)
4. Low Density Polyethylene (LDPE)
5. Polypropylene (PP)
6. Polystyrene (PS)
7. Other Plastics or Miscellaneous Plastics
Nevertheless, there is no exact answer for how many individual types of plastics there are in the world. Plastics are created by combining modern engineering and chemistry, and new plastics are discovered all of the time.
There are so many types of plastics, all with their own characteristics and composition and many plastics are specifically designed to solve unique problems in engineering.
From Nitrile O Rings to Nylon Grommet Nuts, plastic components bring copious potential to the industry. Within Accu’s range alone, there are over 20 types of plastic all with their own distinct features making them great for specific projects. Learning the features of different plastics is crucial to be certain you are choosing the material that is best suited to your project requirements.
Let’s take a look at each type of plastic, what they are and their individual characteristics.
High Density Polyethylene (HDPE)
HDPE is a highly recyclable, long lasting and versatile plastic that is made from petroleum.
Being highly abrasion resistant and tough, HDPE can be used to make items that will be regularly exposed to substantial impact or that need to resist wear, such as cutting boards, longboard sliders and even armour for lightweight combat robots.
HDPE is lightweight with an excellent tensile strength, it also has a high corrosion and chemical resistance. These features, together with the fact it is very cost effective, makes this plastic a great alternative to heavier materials, such as metals.
For example, in an application where weight is a concern, Accu’s HDPE Retaining Washers would be a great option over metal components.
On a wider scale, HDPE can be used for underground piping and for marine applications due to its chemical and corrosion resistance, and it is also a popular material for 3D printing.
HDPE Temperature Range (°C)
0°c to 65°c
NBR UL Flame Rating
Not Rated
Polyvinyl Chloride (PVC)
PVC (Polyvinyl Chloride) is a form of thermoplastic polymer, known for its flexibility, durability and strength.
PVC can be used in both a rigid state and a soft state, making it incredibly versatile and great for many applications.
In its solid, brittle state, PVC can be used in many ways and is often used in the manufacturing industry for wire and cable insulation, piping and door and window profiles.
This thermoplastic polymer can also be used to manufacture components, such as spacers, and is widely used within signage and certain types of clothing.
PVC Temperature Range (°C)
0°c to 50°c
PVC UL Flame Rating
V-0
Low Density Polyethylene (LDPE)
Made from the monomer, ethylene, LDPE is a soft and flexible plastic that is more malleable than the higher density, HDPE.
It is a robust plastic that is great for protection. As it is lightweight and often transparent, LDPE is regularly used for plastic shopping bags, films for food packaging, containers and bottles.
Within precision engineering, LDPE can be used for tubing, laboratory equipment and plastic components such as Inserts, Screw Caps or Barrel Plugs.
LDPE has a low temperature corrosion resistance, however, it is not suitable for high temperature applications or for applications where strength is a priority.
As it is a lightweight and flexible material, LDPE can also be an excellent choice for some prosthetic procedures.
LDPE Temperature Range (°C)
- 30°c to 50-60°c
NBR UL Flame Rating
HB
Polypropylene (PP)
Polypropylene (PP) is a type of thermoplastic that is made by combining propylene monomers.
PP is resistant to many chemicals and can be easily welded to other Polypropylene components providing further versatility in application.
Due to its chemical resistant properties, PP is often used for chemical packaging such as those for cleaning products and bleach or for medical supplies and equipment like a syringe.
Polypropylene can be found in a range of components, such as Accu’s Adjustable Feet. It is often used in precision engineering as it is easy to mould into specific shapes for projects that have a distinct criteria.
PP Temperature Range (°C)
0°c to 65°c
PP UL Flame Rating
V-2
Polystyrene (PS)
Polystyrene (PS) is a thermoplastic made from the monomer styrene.
It is naturally transparent and can be formed into a solid plastic, a film or a foam material.
Polystyrene components, such as Spacers are also popular for many engineering applications due to their thermal and electrical insulating properties.
In its more brittle form, Polystyrene is widely used in the medical industry for test tubes and petri dishes.
As an expanded foam, sometimes referred to as styrofoam, PS is widely used in packaging. It can often be seen in the form of packing peanuts, which are used to protect appliances and whitegoods when they are packed into boxes and transported.
Biodegradable packing peanuts can be made by combining cellulose and Polystyrene.
PS UL Flame Rating
HB
Polyoxymethylene (POM)
Polyoxymethylene (POM)Polyoxymethylene (POM), often referred to as Acetal or Polyacetal is a type of thermoplastic regularly used to make fasteners, spacers and washers.
With very similar characteristics to Nylon, these two types of plastics can generally be interchangeable both in applications and for visual appeal.
For example, both Nylon and POM can be used for components which require a higher level of stiffness and can also withstand moderate loads.
Though they have similarities, these plastics do have strengths and weaknesses in different areas which can impact material selection.
Nylon typically offers superior tensile strength and bending stiffness in comparison to Polyoxymethylene. Nylon can also handle higher loads and higher temperatures.
POM, by comparison, can be ideal where intense force and cold temperatures are concerned; meaning that components made from this material have a higher impact resistance and cold resistance.
However, without the incorporation of special additives, Nylon can be susceptible to damage from UV radiation. It can also swell when exposed to certain levels of humidity resulting in a loss of tensile strength.
POM Temperature Range °C
- 50°c to 100°c
POM UL Flame Rating
HB
Polyetheretherketone (PEEK)
Polyetheretherketone is a semicrystalline engineering thermoplastic that is commonly referred to as PEEK.
This type of plastic is renowned for its exceptional ability to keep its original shape and size even when operating at extreme and high temperatures.
In moving and volatile applications, PEEK fasteners offer a high tensile strength and flame resistance and can continuously operate at temperatures of up to 180°c.
In fact, PEEK is twice as strong as Nylon and also has a higher chemical resistance in comparison to Polypropylene (PP).
Where other, similar plastics may expand and contract when exposed to harsh conditions, PEEK is able to remain thermally stable and, as a result, is ideal for many high-performance applications.
For example, being electrically insulating, PEEK is a great material for EV applications where fasteners will be exposed to high temperatures and electrical currents.
As a result of its chemical resistance, PEEK Cap Head Screws are often used within the food industry; they will not react, corrode or chemically compromise the food whilst also being resistant to the chemicals that are used during cleaning.
In accompaniment with its range of robust characteristics, PEEK is also a biocompatible material which makes it excellent for use in medical applications, such as dental implants.
PEEK Temperature Range (°C)
- 50°c to 180°c
PEEK UL Flame Rating
V-0
Polyvinylidene Fluoride (PVDF)
PVDF, abbreviated from Polyvinylidene Fluoride, is a tough engineered fluoro-thermoplastic that offers a unique balance of excellent chemical resistance and strength.
With high temperature stability, heat and flame resistance, PVDF nuts and fasteners are ideal for use in working electrical applications or electrical cabinets.
PVDF Temperature Range (°C)
-35°c to 150°c
PVDF UL Flame Rating
V-0
Polytetrafluoroethylene (PTFE)
Polytetrafluoroethylene, commonly referred to as PTFE, is a fluoropolymer that is known for its exceptional corrosion resistance and ability to be chemically inert at elevated temperatures.
Often known by its brand name, Teflon. PTFE can be used in a range of applications anywhere from cookware to surgical equipment.
Fasteners that are made from this material are not reactive when operating within most chemical environments. This includes organics, acids, bases, mixed chemicals and hydrofluoric acid.
Due to the fluorine within its molecular structure, PTFE repels and will not bond to other materials which also makes it low-friction. This is one of the reasons that Teflon is used to create the ‘non-stick’ feature of a non-stick pan.
Being bio-inert, PTFE will also not leach into or contaminate things that it comes into contact with. This makes it ideal for applications where these features are essential, such as for surgical wrapping materials or for food based products.
In the engineering industry, PTFE can be mixed with other plastics to reduce the surface friction of the component. Such can be seen in Accu’s PTFE and Black Polyamide Slide Bearings.
PTFE Temperature Range (°C)
- 40°c to 135°c
PTFE UL Flame Rating
V-0
Polycarbonate (PC)
Polycarbonate (PC) is a popular material within precision engineering often chosen as a result of its strength and uniquely transparent appearance.
Due to its impact resistance and excellent optical clarity, PC is commonly used in assemblies which need to be tough without any visual hindrance, such as display signage, face shields or skylights.
Components that are made from PC, such as Accu’s Polycarbonate Pan Head Machine Screws, are often referred to as ‘see-through’ or ‘invisible’ screws.
PC Temperature Range (°C)
- 40°c to 115°c
PC UL Flame Rating
HB
Polyphenylene Sulfide (PPS)
Polyphenylene Sulfide is a high performance thermoplastic with an exceptionally high temperature resistance.
It has great mechanical strength, dimensional stability and chemical resistance as well as a high melting point and flame resistance.
As a result of these characteristics PPS can be used as a more economical alternative to PEEK in applications that are exposed to extreme conditions.
For example, in the automotive industry PPS can be a substitute for metal components in areas that are prone to significant heat, such as fuel injection systems or brakes. For the same reason, PPS Screws are often used in electronic enclosures or inside industrial machinery.
They can also be found in many household appliances, such as heating and air conditioning, pan handles and kitchen appliances like a toaster or a microwave oven.
PPS Temperature Range (°C)
- 40°c to 220°c
PPS UL Flame Rating
V-0
Polyamide / Nylon (PA)
Polyamide (PA), also known as Nylon, is a type of semicrystalline polymer that is a popular material for plastic components, such as Accu’s Nylon Grommet Nuts or Push Clips.
PA is a low density, tough plastic with a high thermal stability and, for the most part, it also has a great chemical resistance. Though, some especially strong acids and alkalis can have adverse effects.
The most common forms of PA are PA 6 (Nylon 6) and PA 66 (Nylon 66) and they share very similar qualities.
They are both strong, with great machinability and have an excellent resistance to wear and tear.
For this reason, Polyamide can be used as a metal alternative in many applications where a high strength-to-weight ratio is essential.
PA 6, in particular, provides a great balance between mechanical strength and chemical and abrasion resistance making it ideal for use in a wide range of industrial applications.
PA 6 also has a lower mould shrinkage in comparison to PA 66. This means that it is less susceptible to shape changes and can offer more consistency and reliability in the long term dimensions of a component.
Nylon 66, on the other hand, is more likely to shrink when exposed to cool air. Though, Nylon 66 does have added resistance properties such as a higher melting point and a better resistance to acids.
PA Temperature Range (°C)
- 40°c to 75°c
PA UL Flame Rating
V-2
As mentioned earlier, new plastics are often made in response to a gap in the industry to solve engineering problems.
Where an existing type of plastic has specialised features, some plastics - such as Polyamide - can be treated or combined with other materials to create a plastic with higher performance characteristics.
In the case of Polyamide (PA), we have Glass Fibre Reinforced Polyamide, Heat Stabilised Polyamide and Reny.
Glass Fibre Reinforced Polyamide
As its name suggests, Glass Fibre Reinforced Polyamide (PA 6+25% GF) is a type of Polyamide that is combined with glass fibre.
Reinforcing Polyamide with Glass Fibre improves the strength, rigidity and wear of the plastic whilst also giving it a better thermal resistance.
For this reason, Glass Fibre Reinforced Polyamide is a popular choice when making power tools as it can create a tool that is lightweight with a high tensile strength. PA 6+25% GF also has a high resistance to fracturing which can protect power tools against any damage that they may incur from being dropped.
PA 6+25% GF is rated to UL 94 HB.
Heat Stabilised Polyamide
Heat Stabilised Polyamide (PA 6) has most of the same characteristics as standard Polyamide, but has the added benefit of being usable in higher temperature applications.
To achieve this effect, the plastic is specially treated to develop better thermal properties whilst its mechanical properties remain intact.
Heat Stabilised Polyamide (PA6) can be used in environments where temperatures may reach 125°c and is rated to UL94 V-2.
For this reason, Heat Stabilised Polyamide can be a popular choice in the automotive industry, especially within EV applications, or in automotive plastics, such as air intakes.
Reny
Reny is a proprietary moulding compound made up of Polyamide MXD6 that has been reinforced with glass fibre, carbon fibre or special minerals.
Generally speaking, Reny has superior mechanical strength and modulus in comparison to other engineering plastics. As a result, Reny is a suitable substitute for metal in many applications. For example, Accu’s Reny Pan Head Machine Screws are a great metal alternative for assemblies within electronics, automotion, electrical appliances and machinery.
Reny Temperature Range (°C)
-40°c to 75°c
Reny UL Flame Rating
HB
Rubber
Rubber is a polymer that is both strong and flexible making it ideal for many components and applications.
There are numerous forms of rubber, including NBR (Nitrile Butadiene Rubber), TPE (Thermoplastic Elastomer), TPR (Thermoplastic Rubber) and FPM (Fluoroelastomer).
Nitrile Butadiene Rubber (NBR)
NBR (Nitrile Butadiene Rubber) is a type of synthetic rubber composed of acrylonitrile (ACN) and butadiene that is resistant to many chemicals, including oil and fuel.
As the concentration of Nitrile in this copolymer increases, the more resistant it becomes to chemicals. However, this does reduce the flexibility of the material.
NBR is often used for O Rings, seals and grommets in chemically exposed environments, such as those found in the automotive, marine and aircraft industries or in a chemical lab.
NBR Temperature Range (°C)
- 34°c to 95°c
NBR UL Flame Rating
Not Rated
Fluoroelastomer (FPM)
Fluoroelastomer (FPM) is a fluorinated polymer, or fluoropolymer, that is known for its resistance to extreme temperatures, chemicals and oil.
This type of plastic may also be referred to as FKM or Viton.
As a result, it is commonly used to make O Rings and Seals to be used in the automotive and aerospace industries and in industrial equipment.
To find out more about which material is best for O Rings head to our technical article, ‘What Is An O Ring’ where we explore the differences between NBR and FPM O-Rings.
FPM Temperature Range (°C)
Typically, FPM is considered to have a temperature range of between - 20°c to 205°c. However, for short working periods, it can withstand lower temperatures such as -30°c and -45°c and higher temperatures such as 230°c.
FPM UL Flame Rating
Not Rated
TPE And TPR
TPE and TPR are both types of thermoplastic elastomers sharing almost identical characteristics. In fact, upon first glance, you may not notice a difference at all.
TPE and TPR are recyclable materials that have high impact strength and both weather and chemical resistance. They also have the same temperature range, of between - 30°c to 140°c, and neither have been given a UL Flame Rating.
In order to identify the difference between TPE and TPR, you need to take a look at their base materials.
TPR is modified from SBS (Styrene Butadiene Styrene), a form of synthetic rubber that is often used as an element of design to add soft touch features to a product, such as on a drill or screwdriver.
It is also a great material for certain components, such as Accu’s TPR Flat Washers, due its excellent sealing and anti-vibrational properties.
In comparison, TPE is modified from SEBS, a hydrogenated form of SBS.
With added molecular hydrogen, SEBS has several features making its performance higher than that of SBS. For example, it has a higher heat and corrosion resistance, an improved weather and oil resistance and it is also more resistant to yellowing.
TPE components, such as Accu’s TPE Moss Plugs, would be ideal for industrial applications where heat, chemical or acid resistance is essential.
Temperature Range And UL Flame Rating For Each Type Of Plastic
This table demonstrates the recommended temperature range and UL Flame Rating for each plastic type discussed in this article.
Please note that these figures should be used as guidance only.
Solving problems everyday, plastics have brought the potential for new advancements in engineering to a new level.
From lightweight and flexible to dense and durable, there are so many types of plastic, each with their own distinct characteristics.
Whether you need a component with excellent electrical insulation, a component with great corrosion resistance or a more cost effective option for your project, within Accu’s selection alone there are plastic choices for countless application requirements.
Interested in learning more about applications using plastic? Head to our article ‘Polyfix Screws: Self Tapping Screws For Plastic’ where you can learn all about this fasteners’ trilobular shaped thread and why it is ideal for plastic assemblies.