Overview of Plastics
The global plastic market size was valued at USD 568.9 billion in 2019 and is expected to grow at a compound annual growth rate (CAGR) of 3.2% from 2020 to 2027. Increasing plastic consumption in the construction, automotive, and electrical and electronics industries is projected to drive the market for plastic over the forecast period (source: https://www.grandviewresearch.com/industry-analysis/global-plastics-market). Although the terms 'plastics' and 'polymers' are used interchangeably, there is a difference between the two. Polymers are made of macromolecules, which are large molecules made by joining together many smaller ones called monomers. They comprise of molecules with repeated patterns or chains. These chains can be linear or branched. Each molecule is called a ‘mer’, so the entire cluster of joined molecules is called ‘polymer’. The process of transformation of monomer molecules to a polymer molecule is known as polymerization. Ethylene for example, forms chains of molecules under the right condition, and is called polyethylene; the polymer of ethylene. While polymers have repeated units of carbon and hydrogen, they can also contain other elements like oxygen, nitrogen, sulphur, silicon, etc. Polymers can therefore be organic or synthetic. Cellulose or proteins are examples of naturally occurring polymers. Plastics are a subset of polymers, and are manufactured by additives that impart the required quality to the end material. Simply put, all plastics are polymers, but all polymers are not plastic.
It won’t be an overstatement to say that the world as we know it today has been made possible by the advent of plastic. Plastics are present everywhere today – carrying bags, bottles, wrappers of all part, fabrics, paints, insulating material, computer hardware, electronics, automobile parts, medical devices, and even parts of space rockets are made of plastic. And the utility of plastics keep growing unabated, aided by advanced technology that has made it possible to impart various qualities that are needed of the finished product.
Plastic Manufacturing Processes
Plastic materials are the result of the combination of carbon elements reacting with oxygen, hydrogen, nitrogen, and other organic and inorganic elements. These polymers have the ability to change into a liquid (melt), and are capable of being formed into shapes by the application of heat and pressure. Plastics are a family of materials, not a single kind of material. They can be manufactured by many processes like blow moulding, polymer casting, plastic injection moulding, rotational moulding, plastic extrusion, vacuum moulding and 3D printing; however, the choice of process ultimately depends on the kind of plastic that is being used. For the purpose of choosing a manufacturing process, plastics can be classified as thermoplastics or thermosetting.
Thermoplastics are plastics that consist of a long chain of molecules, either linear or branched, having side chains or unattached groups to other polymer molecules. The most important advantage of thermoplastic is that they can be melted repeatedly by applying heat under pressure. The melt can then be cooled and hardened into the final desired shape. Chemical changes do not take place during the transformation process. A few examples of thermoplastics include polyethylenes like HDPE, LDPE and LLDPE.
Thermosetting plastics are synthesized by condensation polymerization. Unlike thermoplastics, these plastics harden irreversibly upon heating or with chemical addition. Thermoplastics are generally liquids at room temperature. When heated, the thermosetting resin solidifies into the shape of the mould, but this solidification process includes the formation of certain bonds, called cross-links, that hold the molecules in place and change the basic nature of the material, preventing it from melting. This process is irreversible. A few examples of thermosetting plastics include epoxy resin, melamine, vulcanized rubber and polyurethane.
Benefits of Plastic Injection Moulding
Injection moulded plastics impart shape to the material by heating the molding material. It is cost effective, offers resistance to corrosive chemicals and physical impacts. Using injection molding also ensures the parts manufactured hardly require any work after the production. This is because the parts have more or less a finished appearance after they are ejected from the injection molds. A few benefits that have made plastic injection popular include:
The plastic injection moulding process is versatile. It can be used to manufacture many products like plastic bottles, electronic items, children’s toys, automobile parts like dashboards, acrylic films, wipers, bumpers, cup holders, healthcare industry products like disposable injections, IV bottles, drips, etc. The list of products that is manufactured using the plastic moulding process is almost endless.
There is one more thing in favour of it – today’s plastic injection moulding process is environment friendly. The scrap plastic generated during the production process is reground and re-used. Hence, the process generates very little waste.
Plastic Injection Moulding Simulation Software
Plastic injection moulding can be used to manufacture everything from microelectronic components to very large automobile, aerospace or building construction parts. Advances in raw plastic material and injection moulding process have propelled its growth. Despite its popularity though, the process is not without its share of challenges. Even experienced design engineers find it difficult to cope up with complex part geometries. The introduction of newer plastic raw material is another challenge. Each new material has its own physical properties like viscosity, melting point, dimensional stability, etc. If the injection moulding process is not set properly, it can result in burning, deformities, surface imperfections and brittle parts. Surface imperfections and deformities can occur when the surface temperature of the mould is uneven, or if the melting temperature is too high. Brittle pieces are formed when not enough liquefied resin is injected into the mold or if the plastic hardens before the mould can be filled.
In the era before Industry 4.0, most of the injection moulded parts were the result of trial and error with different combinations of raw material, temperatures, and other parameters critical to the process. Simulation software, like that from 3D Timon™, has come to the rescue of plastic injection moulding designers and engineers. The simulation software, which is parametric in nature, allows the design team to minimize the margin of error. The better class of plastic simulation software in fact even suggests various options to analysts. Since the introduction of simulation software, plastic manufacturers have been able to improve product aesthetics, shorten moulding cycles, reduce wastage and be eco friendly, produce thinner yet sturdier parts and minimize development time.
To Summarize
The plastic industry is growing, and environment friendly processes like plastic injection moulding is taking the lead in popularity for manufacturing plastic products. While plastic moulding is one of the most popular choices of manufacturing plastic products, the procedure is tedious and challenging. Plastic moulding simulation software is playing a greater role in manufacturing, as it mitigates the time needed to perfect a process. Moulding simulation software also reduces waste, and is thus eco friendly.