Plastics engineering

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Plastics engineering encompasses the processing, design, development, and manufacture of plastics products. A plastic is a polymeric material that is in a semi-liquid state, having the property of plasticity and exhibiting flow. Plastics engineering encompasses plastics material and plastic machinery. Plastic machinery is the general term for all types of machinery and devices used in the plastics processing industry. [1] The nature of plastic materials poses unique challenges to an engineer. Mechanical properties of plastics are often difficult to quantify, and the plastics engineer has to design a product that meets certain specifications while keeping costs to a minimum. Other properties that the plastics engineer has to address include: outdoor weatherability, thermal properties such as upper use temperature, electrical properties, barrier properties, and resistance to chemical attack.

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In plastics engineering, as in most engineering disciplines, the economics of a product plays an important role. The cost of plastic materials ranges from the cheapest commodity plastics used in mass-produced consumer products to very expensive, specialty plastics. The cost of a plastic product is measured in different ways, and the absolute cost of a plastic material is difficult to ascertain. Cost is often measured in price per pound of material, or price per unit volume of material. In many cases, however, it is important for a product to meet certain specifications, and cost could then be measured in price per unit of a property. Price with respect to processibility is often important, as some materials need to be processed at very high temperatures, increasing the amount of cooling time a part needs. In a large production run, cooling time is very expensive.

Some plastics are manufactured from recycled materials but their use in engineering tends to be limited because the consistency of formulation and their physical properties tend to be less consistent. Electrical, electronic equipment, and motor vehicle markets together accounted for 58 percent of engineered plastics demand in 2003. [2] Engineered plastics demand in the US was estimated at $9,702 million in 2007.

A big challenge for plastics engineers is the reduction of the ecological footprints of their products. First attempts like the Vinyloop process can guarantee that a product's primary energy demand is 46 percent lower than conventionally produced PVC. The global warming potential is 39 percent lower. [3]

Plastics engineering specialties

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<span class="mw-page-title-main">Thermoplastic</span> Plastic that softens with heat and hardens on cooling

A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.

<span class="mw-page-title-main">Polypropylene</span> Thermoplastic polymer

Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.

<span class="mw-page-title-main">Acrylonitrile butadiene styrene</span> Thermoplastic polymer

Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x·​(C4H6)y·​(C3H3N)z is a common thermoplastic polymer. Its glass transition temperature is approximately 105 °C (221 °F). ABS is amorphous and therefore has no true melting point.

<span class="mw-page-title-main">Polyethylene terephthalate</span> Polymer

Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins.

<span class="mw-page-title-main">Thermosetting polymer</span> Polymer obtained by irreversibly hardening (curing) a resin

In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst. Heat is not necessarily applied externally, but is often generated by the reaction of the resin with a curing agent. Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.

<span class="mw-page-title-main">Injection moulding</span> Manufacturing process for producing parts by injecting molten material into a mould, or mold

Injection moulding is a manufacturing process for producing parts by injecting molten material into a mould, or mold. Injection moulding can be performed with a host of materials mainly including metals, glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and injected into a mould cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould-maker from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers that do not melt during the injection moulding of some lower-temperature thermoplastics, can be used for some simple injection moulds.

<span class="mw-page-title-main">Wood-plastic composite</span> Composite materials made of wood fiber and thermoplastics

Wood-plastic composites (WPCs) are composite materials made of wood fiber/wood flour and thermoplastic(s) such as polythene (PE), polypropylene (PP), polyvinyl chloride (PVC), or polylactic acid (PLA).

<span class="mw-page-title-main">Plastic recycling</span> Processes which convert waste plastic into new items

Plastic recycling is the reprocessing of plastic waste into new products. When performed correctly, this can reduce dependence on landfill, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions. Although recycling rates are increasing, they lag behind those of other recoverable materials, such as aluminium, glass and paper. Since the beginning of plastic production in the 20th century, until 2015, the world has produced some 6.3 billion tonnes of plastic waste, only 9% of which has been recycled, and only ~1% has been recycled more than once. Additionally, 12% was incinerated and the remaining 79% disposed of to landfill or to the environment including the sea.

<span class="mw-page-title-main">Microcellular plastic</span>

Microcellular plastics, otherwise known as microcellular foam, is a form of manufactured plastic fabricated to contain billions of tiny bubbles less than 50 microns wide. It is formed by dissolving gas under high pressure into various polymers, relying on the phenomenon of thermodynamic instability to cause the uniform arrangement of the gas bubbles, otherwise known as nucleation. Its main purpose was to reduce material usage while maintaining valuable mechanical properties. the density of the finished product is determined by the gas used. Depending on the gas, the foam's density can be between 5% and 99% of the pre-processed plastic. Design parameters, focused on the foam's final form and the molding process afterward, include the type of die or mold to be used, as well as the dimensions of the bubbles, or cells, that classify the material as a foam. Since the cells' size is close to the wavelength of light, to the casual observer the foam retains the appearance of a solid, light-colored plastic.

<span class="mw-page-title-main">Rotational molding</span> Making hollow plastic objects in a heated mold

Rotational molding involves a heated mold which is filled with a charge or shot weight of material. It is then slowly rotated, causing the softened material to disperse and stick to the walls of the mold forming a hollow part. In order to form an even thickness throughout the part, the mold rotates at all times during the heating phase, and then continues to rotate during the cooling phase to avoid sagging or deformation. The process was applied to plastics in the 1950s but in the early years was little used because it was a slow process restricted to a small number of plastics. Over time, improvements in process control and developments with plastic powders have resulted in increased use.

Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers that consist of materials with both thermoplastic and elastomeric properties. While most elastomers are thermosets, thermoplastics are in contrast relatively easy to use in manufacturing, for example, by injection moulding. Thermoplastic elastomers show advantages typical of both rubbery materials and plastic materials. The benefit of using thermoplastic elastomers is the ability to stretch to moderate elongations and return to its near original shape creating a longer life and better physical range than other materials. The principal difference between thermoset elastomers and thermoplastic elastomers is the type of cross-linking bond in their structures. In fact, crosslinking is a critical structural factor which imparts high elastic properties.

The NORYL family of modified resins consists of amorphous blends of polyphenylene oxides (PPO) or polyphenylene ether (PPE) resins with polystyrene. They combine the inherent benefits of PPE resin, with excellent dimensional stability, good processability and low density.

The plastics industry manufactures polymer materials—commonly called plastics—and offers services in plastics important to a range of industries, including packaging, building and construction, electronics, aerospace,Manufacturing and transportation.

<span class="mw-page-title-main">Filler (materials)</span>

Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. Particulates and fibers are the main subgroups of filler materials. Particulates are small particles of filler which are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.

Polymer engineering is generally an engineering field that designs, analyses, and modifies polymer materials. Polymer engineering covers aspects of the petrochemical industry, polymerization, structure and characterization of polymers, properties of polymers, compounding and processing of polymers and description of major polymers, structure property relations and applications.

<span class="mw-page-title-main">Plastic</span> Material of a wide range of synthetic or semi-synthetic organic solids

Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.

Recycling can be carried out on various raw materials. Recycling is an important part of creating more sustainable economies, reducing the cost and environmental impact of raw materials. Not all materials are easily recycled, and processing recyclable into the correct waste stream requires considerable energy. Some particular manufactured goods are not easily separated, unless specially process therefore have unique product-based recycling processes.

Masterbatch (MB) is a solid additive used for coloring or imparting other properties to plastic. Masterbatch is a concentrated mixture of pigments and/or additives which is manufactured by encapsulation during a heat process or twin screw extrusion into a carrier matrix resin, which is then cooled and further cut into a granular shape. Masterbatch allows the processor to color raw polymer economically.

<span class="mw-page-title-main">Economics of plastics processing</span>


The economics of plastics processing is determined by the type of process. Plastics can be processed with the following methods: machining, compression molding, transfer molding, injection molding, extrusion, rotational molding, blow molding, thermoforming, casting, forging, and foam molding. Processing methods are selected based on equipment cost, production rate, tooling cost, and build volume. High equipment and tooling cost methods are typically used for large production volumes whereas low - medium equipment cost and tooling cost methods are used for low production volumes. Compression molding, transfer molding, injection molding, forging, and foam molding have high equipment and tooling cost. Lower cost processes are machining, extruding, rotational molding, blow molding, thermoforming, and casting. A summary of each process and its cost is displayed in figure 1.

References

  1. "Introduction of Plastics Engineering". Qingdao Haoteng Machinery Manufacture Co. Archived from the original on 2013-05-20. .
  2. "Engineered Plastics :: Advanced Materials". mdmr.net. April 2004. Archived from the original on 2008-02-11. Retrieved 2022-07-21.
  3. "The VinyLoop Eco-Footprint Study" (PDF). solvayplastics.com. Archived from the original (PDF) on 2016-05-16. Retrieved 2012-06-10.