All About Plastic: Definition, Types and Applications

Properties of Plastic

Plastics can have a wide range of physical and chemical properties, depending on their chemical structures and how they are processed. However, some general physical and chemical properties are common to most plastics. These properties are given below:

Physical Properties of Plastic

1. Density: Plastics come in many different densities, from as low as 0.9 g/cm³ for foamed plastics to as high as 1.5 g/cm³ for some engineering plastics.
2. Melting Point: The melting points of plastics vary widely depending on the type of polymer. Some plastics have low melting points and can be easily molded while others have high melting points and require specialized processing techniques.
3. Hardness: Plastics can range from soft and flexible to hard and rigid, depending on the specific polymer and its processing.
4. Transparency: Some plastics are optically transparent while others are opaque and block light. Many transparent plastics can accept dye if you need them to be opaque.
5. Permeability: Plastics can be permeable to gasses and liquids, which can be an advantage in some applications (such as food packaging) and a disadvantage in others (such as chemical storage).

Chemical Properties of Plastic

1. Resistance to Chemicals: Many types of plastic are resistant to industrial chemicals, acids, and other corrosive substances. This makes them useful in a variety of industrial applications.
2. Stability: Some plastics are sensitive to heat, light, and radiation, which can cause them to degrade over time. UV stabilizers and antioxidants are often added to plastics to improve their stability
3. Flammability: Plastics can be highly flammable, and many of them release toxic gasses when burned. Flame retardants are often added to plastics to improve their fire resistance.
4. Degradation: The rate at which plastics degrade depends on a variety of factors, including the type of plastic, the conditions to which they are exposed, and the specific environmental factors they encounter. Some plastics, such as polyethylene (PE) and polypropylene (PP), degrade very slowly so they will persist in the environment for hundreds of years. Other plastics, such as polylactic acid (PLA), are designed to be biodegradable and can break down much more quickly when exposed to moisture, heat, or microorganisms. Some plastics can undergo physical degradation, such as cracking or fragmentation, even if they do not break down chemically. This can be caused by sunlight, temperature changes, or mechanical stress, and can lead to the release of hazardous plastic particles called microplastics into the environment.
5. Solubility: Each plastic has unique solubility characteristics. Plastics that are amorphous (not crystalline), like polystyrene and polycarbonate, are more soluble in typical organic solvents than crystalline ones. Certain highly crystalline polymers, including nylon and polyolefin, resist dissolution while others like polyvinyl acetate (PVA) are highly soluble in water.
6. Reactivity: Plastics can be reactive in different ways, depending on their chemical composition. For example, polyethylene reacts with oxygen to form carbon dioxide and water while polypropylene is relatively unreactive and stable in most chemical environments.
7. Biodegradability: Some plastics, such as polyethylene, are not biodegradable and can persist in the environment for hundreds of years. Others, such as polycaprolactone (PCL), are biodegradable and can be broken down by bacteria and fungi over time.
8. Recyclability:  Plastics can be difficult to recycle since they each have different chemical compositions and properties. Some types of plastics are easier to recycle than others, and recycling methods vary depending on the type of plastic.

Applications of Plastic: Key Industries That Use It

Plastic has many different applications and we see engineers from many industries quoting plastic parts with Xometry. Some of the most common uses of plastic we have seen are listed below: 

1. Toys

Plastics are often used in the production of toys because they can be molded into various shapes and colors. Plastic toys are durable and lightweight, so they withstand wear and tear.

2. Electronics

Plastics are non-conductive, meaning they can protect electronic components and allow for easy assembly. This is why you find plastic in computer and phone cases and as the insulation on wires.

3. Automotive

Plastics are used in various parts of automobiles, including dashboards, bumpers, engine parts, and interior panels. Since they’re both lightweight and durable, they reduce the vehicle’s weight and improve fuel efficiency.

4. Packaging

Plastic is an ideal material to use for product packaging. Plastics are adaptable, hygienic, light, flexible, and durable. Packaging is thus responsible for the majority of the plastics used globally, coming in the form of vending packaging, baby products, protective packaging, containers, bottles, drums, trays, boxes, cups, and much more.

5. Medical Devices

Plastics are used extensively in the medical industry, including, but not limited to, disposable syringes, IV and blood bags, prosthetic limbs, implantable devices, dialysis machines, heart valves, tubing, and wound dressing. Medical-grade plastics are sterile and biocompatible and can be easily molded into complex shapes. Plus, they’re often less expensive than traditional medical materials.

Advantages of Plastics in Manufactured Parts

1. Versatility: Plastics can be molded into various shapes and sizes.
2. Durability: Plastics are strong and can withstand wear and tear, making them long-lasting and, in some cases, suitable for reuse.
3. Lightweight: Plastics are generally lightweight. This makes them great when weight is an important consideration, such as in the automotive and aerospace industries.
4. Cost-effectiveness: Plastics are often less expensive than other materials such as metals, making them a more cost-effective option for many applications.
5. Easy to Manufacture: Plastics are easy to manufacture in large quantities, so they’re perfect for the sort of mass production that cuts per-unit costs. 
6. Low Energy Consumption: The production of some types of plastics requires less energy compared to the production of other materials. That, in turn, helps reduce the environmental impact of manufacturing.
7. Safety: Plastics can be designed to be non-toxic and safe for use in the medical and food industries.

Disadvantages of Plastics

1. Environmental Impact: Most plastics are not biodegradable and can persist for hundreds of years. All that discarded plastic builds up as pollution, which can harm wildlife and ecosystems.
2. Difficulty With Recycling: Not all types of plastic are easily recyclable, which can make proper disposal challenging. Additionally, even recycling processes can have negative environmental impacts since they require significant energy and resources. 
3. Petroleum-Based: Many types of plastic are petroleum-based materials, meaning they’re non-renewable by nature. This can contribute to resource depletion and dependency on fossil fuels.

Xometry provides a wide range of manufacturing capabilities including plastic 3D printing, laser cutting, and injection molding for all of your prototyping and production needs. Start your instant quote today.

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The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.