Plastic Materials and their Applications

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Plastic product design process

The most important properties of plastics you should know:

1- density:

Density measures the?mass per unit volume. It is denoted by the Greek word?ρ?(rho). The formula of density is:

ρ = m/V

where?ρ?is the density,?m?is the mass, and?V?is the volume.

follow this link and you will find the most common plastics densities'

Density of Plastics Material

2- Coefficient of Linear Thermal Expansion(CLTE)

The coefficient of linear thermal expansion is a material property that:

• Characterizes the ability of a plastic to expand when the temperature increases.
• Estimate the dimensional stability of a developed part when temperature varies.

α = ΔL/(L0 * ΔT)

where

• α is the coefficient of linear thermal expansion per degree Celsius.
• xn--l-4lb is the change in length of the test specimen due to heating or to c
• ooling.L0 is the original length of the specimen at room tempe
• rature.xn--t-4lb is the temperature change in °C, du

ring the test.

CLTE is important for the economics of production. It is also necessary for the quality and functioning of products. It determines the:

• Design to predict shrinkage in injection molded parts.
• Dimensional behavior of structures subject to temperature changes.
• Thermal stresses that can occur and cause the failure of a solid artifact composed of different materials. This failure is subjected to a temperature excursion. For example, to predict?efficient material bonding?or while using plastics with metals.

Follow this link and you will find most common plastics (CLTE) Coefficient of Linear Thermal Expansion (CLTE)

3- Ductile / Brittle Transition Temperature

It is the transition temperature below which a ductile plastic specimen becomes brittle. This is not a specific temperature. It is rather a temperature spreading over the 10°C range. DBTT is expressed in °C.

In the stress-strain curve, brittle materials follow a straight path. Here we can see little or no plastic deformation. Whereas for ductile materials there is a significant plastic deformation under load.

The graph below depicts the area covered by brittle and ductile materials. Brittle materials cover less area as they absorb low energy during fracture. While ductile materials cover a larger area and absorb high energy during fracture.

Follow this link and you will find the most common plastics' Ductile / Brittle Transition Temperature values

4- the elongation at break

? = (ΔL/L) x 100

Where:

• ? is the elongation
• ΔL is the difference between the final length and the initial length
• L is the initial length

Elongation at Break is measured in %, The maximum elongation at the break (Emax) is also called “strain to failure”.

What factors affect the elongation at break?

• Velocity of Testing: Slow testing allows for polymer relaxation and higher elongation at break values.
• Orientation Level: Fibers that are less oriented tend to exhibit greater degrees of elongation at break.
• Temperature: In general, the elongation at break increases with an increase in temperature.
• Filler Content: The elongation at the break of composites decreases with an increase in the filler content.

Follow this link and you will find the most common plastics' Elongation at Break or Fracture Strain values

5-Elongation at Yield

Elongation at Yield is the ratio between increased length and initial length at the yield point.

it has the same formula to the elongation at break but here we calculate the difference in length at the yield point

? = (ΔL/L) x 100

Where:

• ? is the elongation
• ΔL is the difference between the final length and the initial length
• L is the initial length

follow this link and you will find the most common plastics' Elongation at Yield (tensile) values

6- Shrinkage

one of the most important values you need to be aware of it while designing a mold for plastics product or when you will deal with plastic product, is the shrinkage value of your plastic material

Most of the shrinkage occurs in the mold while cooling. A small amount of shrinkage occurs after ejection as the molded part continues to cool. After that, the part may continue to shrink very slightly until the temperature and moisture content stabilize.

Follow this link and you will find the most common Shrinkage Value of Plastics Material & Injection Molding

7- Continuous Service Temperature of Plastics

a parameter that helps define the temperature limit for use of that polymer is required.

follow this link and you will find the most common plastics Continuous Service Temperature of Plastics values

common plastics' properties

you can reach a high-quality photo from this link Plastic Properties

comparison chart:

Plastics are classified into three categories according to their physical properties:

1. Thermoplastics
2. Thermosets
3. ?Elastomers

1-???Thermoplastic

Thermoplastic material that can be deformed by heating in a certain temperature range. Thermoplastic materials can withstand very high temperatures so the heat required for melting must be even higher.

Unlike thermosets, thermoplastic materials can be molded as often as is desired by cooling and reheating them, as long as the material is not overheated. Overheating causes the material to decompose.

They can be easily injected molded, cast, extruded and thermoformed, which reduces processing costs and speeds up production. Examples of thermoplastics are polyethylene, polypropylene and polyvinyl chloride (PVC).

Thermoplastic polymers have several properties that make them widely used in various applications:

• Melting and Re-Shaping:?They can be melted and molded into any desired shape, and re-melted and reshaped as many times as needed without undergoing chemical changes.
• Density:?Their density varies from light to heavy, depending on the type of polymer and its application.
• Impact Resistance:?They have good impact resistance, making them ideal for products that are subjected to stress and impact.
• Chemical Resistance:?Some thermoplastic polymers are highly resistant to chemicals, such as?acids and bases, making them suitable for use in harsh chemical environments.
• Electrical Conductivity:?The electrical conductivity of thermoplastic polymers varies depending on the type of polymer and the presence of additives. Some are electrically insulating, while others are electrically conductive.
• Thermal Stability:?Thermoplastic polymers have a high thermal stability, meaning that they can withstand high?temperatures?without breaking down.
• Processability:?They are easy to process, making them a popular choice for mass production of consumer goods and other products.
• Recyclability:?Many thermoplastic polymers are recyclable, which makes them environmentally friendly and reduces waste.
• Cost-effective:?They are relatively inexpensive compared to other types of polymers, making them a cost-effective choice for many applications.
• weldability: thermoplastics can be welded.?Thermoplastics can be welded by heating them until they are soft and malleable and then pressing the parts to be joined together. In the process, the molecules mix at the cut surfaces and join together when they cool and solidify. This process is called thermoplastic welding and is a simple and inexpensive method?of joining parts made of thermoplastics. There are different types of thermoplastic welding, e.g. ultrasonic welding, resistance welding and hot air welding.

Thermoplastic Polymers Applications:

• packaging:?Thermoplastic polymers are widely used in packaging, such as plastic bags, film, and containers, due to their low cost and ability to be molded into various shapes.
• Consumer Goods:?They are commonly used in the production of consumer goods, such as toys, electronics, and appliances, due to their ease of processing and low cost.
• Construction:?They are used in construction applications, such as pipes, gutters, and roofing, due to their durability, chemical resistance, and ability to withstand harsh environmental conditions.
• Automotive:?They are used in the automotive industry for parts such as bumpers, fuel tanks, and wiring insulation due to their low weight and ability to withstand impact.
• Medical:?They are used in medical applications, such as prosthetics, implants, and surgical instruments, due to their biocompatibility, sterilizability, and ability to withstand harsh?environments.
• Textile:?They are used in the textile industry, such as synthetic fabrics and fibers, due to their flexibility, strength, and durability.
• Industrial:?They are used in industrial applications, such as?electrical insulators, seals, and gears, due to their electrical insulation and heat?resistance.
• Agriculture:?They are used in agriculture applications, such as greenhouse coverings and irrigation pipes, due to their durability and ability to withstand harsh environmental conditions.

Some of thermoplastic materials

• Polyethylene (PE)

you can reach a full guide for PE material by following this link:

Polyethylene (PE) - Properties, Uses & Application

• Polypropylene (PP)

you can reach a full guide for PP material by following this link:

Polypropylene (PP) - Types, Properties, Uses & Structure

• Polyvinyl Chloride (PVC)

you can reach a full guide for PVC material by following this link:

Polyvinyl Chloride (PVC) Plastic: Uses, Properties, Benefits & Toxicity

• Polyethylene Terephthalate (PET)

you can reach a full guide for PET material by following this link:

Polyethylene Terephthalate (PET) - Uses, Properties & Structure

• Acrylonitrile Butadiene Styrene (ABS)

Products made with ABS use recycling number 9

you can reach a full guide for ABS material by following this link:

Acrylonitrile Butadiene Styrene (ABS Plastic): Uses, Properties

• Polycarbonate (PC)

you can reach a full guide for PC material by following this link:

Polycarbonate (PC) - Properties, Uses, & Structure - Guide

2- Thermosets

Thermosets are plastics that retain their condition and shape after curing due to spatial crosslinking. Once cured, their polymers can no longer be dissolved. This type of plastic is popular in electrical installations due to its mechanical and chemical resistance, even at high temperatures. Popular thermosets include phenoplastics, virtually all synthetic resins (such as epoxy resins), polyurethane resins for paints and surface coatings and polyester.

Comparison between thermoplastics and thermoset

Thermoplastic Polymers Applications:

• Most polyurethanes are thermosetting plastics. They are abrasion-resistant, flexible and tough offering excellent protection against grease and oil. Polyurethane plastics are found in a massive range of everyday products, including sports footwear soles, automotive parts, computer components, goggles and other PPE, gaskets, bearings, and mobile phone cases.
• Fiberglass?is used to make swimming pools and spas, doors, water-sports equipment, such as surfboards and boat hulls, and automotive parts. Its lightweight and attractive finish also makes fiberglass popular in-home interior design and electronic applications, e.g., circuit boards.

• Melamine resin is a nitrogen-rich, organic thermoset plastic that is used to manufacture kitchen utensils, such as plates, cooking tools, trays and more. Once cured, melamine is flame resistant and extremely tough, making it ideal for the kitchen environment and virtually unbreakable. It can also be used to make children’s toys, picnic sets and other plastic houseware.

• Bakelite is another commonly found thermosetting plastic in household goods and applications. For example, it is used to make light switches and other electrical switches due to its poor ability to conduct electricity and heat. This also makes it a good choice for saucepan handles and other appliances that are regularly exposed to heat.

• Vulcanized rubber, despite its name, is a thermoset plastic made from altered rubber in a process using heat and Sulphur. It is also known as ebonite or hard rubber. It has an opaque finish and is typically manufactured in black or red. Vulcanized rubber is an ideal match for fountain pens, imitation jet jewellery, pipe stems and combs.

• Epoxy resin is often applied to floors and other surfaces to add a tough, anti-slip coating. It is a commonly used thermoset plastic, due to its strength and rigidity, created by a high degree of polymer cross-linking during the curing process. Epoxy resins are often used in structural composite applications in the construction, heavy industry, aerospace and commercial sectors.

you can learn more also about thermosets by following this link Epoxy Resin / Silicone Rubber

Elastomers

Elastomers are polymers that have viscosity and elasticity and therefore are known as viscoelasticity.?The molecules of elastomers are held together by weak intermolecular forces and generally exhibit low?Young’s modulus?and high yield strength or high failure strain. They inherit the unique property of regaining their original shape and size after being significantly stretched.

The properties of elastomers:

• Temperature:?The specific working temperature of elastomers vary depending on the factors like media compatibility, seal design, and dynamic and static operation.
• Low-temperature flexibility:?The rate of recovery of elastomeric material can be studied by subjecting the material to low-temperature retraction.
• Hardness:?The measurement of the material’s resistance towards the deforming force for a defined length of time is done by measuring the hardness. It differs from material to material. The soft compounds deform easily and have high friction, while the harder compounds have high resistance and low friction.
• Aging:?This property helps to understand the behavior of a material when exposed to heat. If the elastomers are pushed beyond their aging resistance, they will suffer from hardening, cracking, and splitting.
• Color:?Colouring is used mainly to differentiate between the compound grades based on their usage.
• Elongation at break:?This property is used for testing the moment of rupture when the material is under?tensile stress.

Examples of Elastomers:

1. Natural rubber:?These are used in the automotive industry and in the manufacture of medical tubes, balloons, and adhesives.
2. Polyurethanes:?These are used in the textile industry for manufacturing elastic clothing like lycra.
3. Polybutadiene:?These are used for providing wear resistance in the wheels of vehicles.
4. Silicone:?These are used in the manufacture of medical prostheses and lubricants as they have excellent chemical and thermal resistance.
5. Neoprene:?These are used in the manufacture of wet suits and in industrial belts.

Some of their applications :

• Motor vehicles:?Some elastomers like thermosets don’t melt easily, making them efficient in building seals, tires various components throughout the automobile design. Especially those components which will be exposed to heat during the functioning. The material of the type polybutadiene offers extraordinary wear resistance hence they are preferable in building tyres.
• Consumer products:?This comprises the widest range of products starting from shoe soles to baby pacifiers and many more miscellaneous.
• Constructions:?Adhesives and sealant materials enfolded under elastomers, which are an unavoidable part of any construction. Especially for filling the gaps.
• Industrial products:?Elastomers are hugely used in making industrial tools, appliances, belts, molds, lubricants, etc.
• Wire and cable:?The material needed to build wires should have high resistance to heat, be easily reshaped(elongated), and provide insulation. Elastomers like neoprene are perfect for this.
• Medical products:?Medical field needs a wide range of products like prosthetics, lubricants, and molds with superior class of chemical and thermal resistance. Elastomers like silicon have widely used the material to build them and many other goods.

Commercial plastics

There are 7 types of plastics called traditional plastics

1 – PET

Plastics that belong to group number one are made out of?polyethylene terephthalate or PET. It holds the number one spot because of its widespread utility. ?It is mostly used for food and drink packaging purposes due to its strong ability to prevent oxygen from getting in and spoiling the product inside.

It’s usually picked up through most curbside recycling programs and has a tremendously positive track record! In fact, PET bottles are?the most widely?recycled plastic?in the world!

• Clear PET is almost transparent.
• Shatterproof, recyclable & eco-friendly
• Can be used in fibers for clothing.
• Safe for packaging food and drinks
• Lightweight yet still offers high strength barrier.
• Suitable for packaging almost all kinds of products

2 – HDPE

Technical name - High-Density Polyethylene – it’s an incredibly resistant resin used for grocery bags, milk jugs, recycling bins, agricultural pipe, but also playground equipment, lids, and shampoo bottles among others. ?Because it’s made with long unbranched polymer chains it’s much stronger and thicker than PET. Also, it is relatively hard and resistant to impact and can be subjected to temperatures of up to 120 °C ?without being affected. As far as its disposal is concerned, HDPE?is accepted at most?recycling?centers in the world, as it is one of the easiest plastic polymers to?recycle.?

1. HDPE is stiff, durable, and strong.
2. HDPE has good chemical resistance meaning it will not react with foods, beverages, or household chemicals being stored.
3. It’s lightweight and easily molded into any shape.
4. Although HDPE is not clear like PET, it can still be translucent, making it possible to see what’s inside.
5. HDPE plastic is hard-wearing and does not break down under exposure to sunlight.
6. It can withstand more extreme temperatures than PET, both hot and cold.
7. HDPE can be reused and recycled.

3 – PVC

Polyvinyl chloride?is the world's third-most widely produced synthetic?plastic?polymer. It comes in two basic forms: rigid and flexible.?In its rigid form, PVC is largely used in the building and construction industry to produce door and window profiles and pipes (drinking and wastewater).

When mixed with other substances, It can be made softer and more flexible and applied to plumbing, wiring, and electrical cable insulation and flooring.?

Thanks to its versatile properties, such as lightness, durability, and easiness of processability, PVC is now replacing traditional building materials like wood, metal, concrete, rubber, ceramics, etc. in various applications.

• Clear PVC has a light blue tint
• Durable & have great tensile strength
• Resistant to heat, chemicals & alkalis
• Can be manufactured into flexible or rigid form
• Not safe for storing food items (may break down over time)
• Mostly used in toys, blister wrap, cling wrap, detergent bottles, piping, plumbing, etc.

4 – LDPE

Contrary to HDPE, LDPE is characterized by low-density molecules, giving this resin a thinner and more flexible design. It has the simplest structure of all the plastics, making it easy and cheap to produce. Used in plastic bags,?six-pack rings, various containers, dispensing bottles, and most famously for plastic wraps, is not often recycled through curbside programs.

• It’s both durable and flexible.
• It does not release harmful chemicals, making it a safe choice for food storage.
• LDPE has good transparency.
• Doesn’t break easily.
• And it resists acids, bases, and oils.

5-PP

Polypropylene is the second-most widely produced?commodity plastic and its market is forecasted to grow even more in the following years. Hard and sturdy, it can withstand high temperatures and is found in Tupperware, car parts, thermal vests, yogurt containers, and even disposable diapers.

Fun fact: because it is VERY resistant to fatigue, PP is usually used for living hinges (the thin piece of?plastic that allows a part of a product to fold or bend from 1 to 180 degrees).

• Non-toxic, transparent
• Stronger than PE plastics
• Stable, flexible, tough & durable
• Impact resistant, wear-resistant & heat resistant
• Fit to make laboratory equipment, medical devices, plastic straws, hot food containers, etc.
• Safe for packaging food and drinks
• Not quite recyclable

6 – PS

Polystyrene is the sixth type of plastic on the list and it can be solid or foamed. It is a very inexpensive resin per unit weight and easy to create, for these reasons, it can be found everywhere: from beverage cups, insulation, and packing materials to egg cartons and disposable dinnerware. Perhaps better known by its commercial name – Styrofoam – it’s highly inflammable and dangerous as it can leach harmful chemicals, especially when heated (which often happens because, as it’s found in disposable take-out containers, people oftentimes microwave it to heat up the food inside it).?

Environmentally speaking it’s among the worst types of plastic: first, it is regarded as not?biodegradable. Second, polystyrene foam blows in the wind and floats on water, due to its low specific gravity. Animals do not recognize it as artificial and may mistake it for food causing serious effects on the health of birds or marine animals that might swallow it.

In addition, polystyrene is not accepted in?curbside collection?recycling programs and is not separated and recycled where it is accepted. To sum up, it’s a no-go.

?

7 – OTHER PLASTIC

If plastic cannot be identified in the six types above-mentioned, then it will be included in group number 7. The best-known plastics of this group are polycarbonates?(PC) used to build strong,?tough?products. Polycarbonates are commonly used for eye protection in the creation of lenses for sunglasses, sport, and safety goggles. But they can also be found on mobile phones and, more frequently, in compact discs (CDs).

In recent years, the use of these resins has been controversial: the basis of this controversy is their leaching that, occurring at high temperatures, releases?bisphenol A, a compound that is on the list of potential environmental hazardous chemicals. Moreover, the decomposition of BPA in landfills does not occur meaning that this chemical will be persistent in the ground and will eventually find its way into water bodies contributing to aquatic pollution.?On top of this, plastics number 7 is almost never recycled.

Plastics Identification Flow Chart

Also you can reach this page to get a high quality table and photo

How to Identify Plastics / Plastics Identification Flow Chart

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