Plastics

View A Video on Plastics - A Quick Introduction

There is an extensive variety of plastic materials on the market today. Polyethylene is the most commonly used member of the plastics family. It is being used to produce a plethora of products, from artificial knees to shampoo bottles and milk cartons. Polystyrene is also ever present in modern life, though more frequently referred to as the trade marked extruded foam, StyroFoam. Delrin is another common plastic, often used as a metal substitute and therefore very popular in the automotive and construction industries. PVC, acrylic, polycarbonate and polypropylene are just a few of the other predominate plastics producing products currently in circulation in the medical field, hardware stores, electronics and food and beverage industries as well as many more industries. So named for their plastic or mold-able qualities, thermoplastics such as these can be molded and remolded any number of times, allowing for continuous transformations of materials and easy distribution. Highly diversified, plastic materials can be purchased in supply stock forms such as plastic rods, plastic sheets and plastic films. While these items may be used as the finished product, they easily comply with secondary processing such as plastic fabrication and precision plastic machining.

Plastics made of synthetic, natural and organic monomers are divided into two categories: thermoplastics and thermosetting plastics. While the names are very similar, it is important to distinguish between the two when selecting the proper material for a given application. The former, thermoplastic, is more commonly used because it can be melted and remolded numerous times. The composition is formulated to become pliable when heated and rigid when cooled. The pitfall of thermoplastics is that they may become glass-like and fracture at extremely cold temperatures. Thermosetting plastics are more adept to cold applications but chemically deteriorate when subjected to high heat. While thermoplastics can be purchased as pellets or any number of stock shapes for secondary processing, thermosets are available only in two-part liquid resins or non-flowing mass premixed blends. Far more limited in their possibilities, thermosets cannot be remolded after curing and must therefore be supplied in raw form or finished products. Cure technology is as diverse as plastic itself and includes air setting, film drying, anaerobic, hot melt, cross-linking, room temperature curing, and vulcanizing. The cure technology and type of polymer used depends largely on the manufacturing processes and final purpose of the product.

The processes required to form specific compounds vary significantly. Suspension, emulsion/dispersion, solution and mass methods are commonly used to produce the resins, liquids, gels and powders that manufacturers distribute. While this raw form is used for thermosetting plastics that undergo only one manufacturing process, most plastic suppliers provide thermoplastics in stock shapes that have undergone some initial processing. The shapes and performs provided are more easily handled and in some instances may be used as the final product. Plastic sheets, pipes, profiles and rods, which are the most common stock shapes, are usually produced through some form of injection molding or extrusion. Films are made using blown film extrusion, in which an extruded tube of plastic is inflated to stretch the material to the desired length and thickness. Some films are available as thin as .0004inch. Additional processes include foam extrusion, precision plastic machining, vacuum forming, pressure forming, thermoforming, casting, pultrusion, welding and grinding. Each method uses heat and pressure to combine the resins before cooling to create the final form. While these processes may use pure resins, manufacturers can combine the raw plastic materials with a number of additives such as heat stabilizers, lubricants, fillers and plasticizers as needed for specific applications. These can have a significant impact on the color, strength, density, working temperature range, structural integrity and corrosion and heat resistance of a polymer.

The unique properties of each specific plastic must be carefully understood with regards to the final product. There are limitless industrial, commercial and residential applications for plastic. Virtually every industry utilizes some form of it. Food and chemical processing, water treatment, gas and oil, medical, pharmaceutical, aerospace, automotive, building and construction industries are among those that utilize the common applications for plastic parts and products. From toothbrushes to windows to aircraft panels, it is nearly impossible to go a day without encountering plastic materials. The pervasiveness of plastics, however, has led to great concerns over their potentially harmful impact on the environment. Because plastics are manufactured to be durable and long-lasting, they are rarely biodegradable. More recently, however, concern for the environment has led to research into bioplastics made from synthesizing polyethylene from ethanol obtained from sugarcane. There could soon be a present where all plastic products are biodegradable. However, until bioplastics are developed enough to be mainstream, it is the responsibility of each consumer to diligently recycle the thermoplastics used on a daily basis so they might be reused. The essence of plastics allows them to be melted down and reformed, which greatly reduces the negative impact they have on our planet.
 

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Plastic Types

• ABS (Acrylonitrile-Butadiene-Styrene) is a popular family of resins that is strong and resistant to most chemicals and stains. ABS is created by the polymerizing of acrylonitrile and styrene (liquids) and butadiene (a gas).
  
• Acetal is a plastic that is able to replace metal in many mechanical and structural applications. It has good tensile strength and excellent machinability.
  
• Acrylic is made of clear, thermoplastic resins that are found in acrylic acid and natural sources like petroleum.  
  
• Corrugated plastic sheeting is a highly versatile, extruded twin-wall plastic sheet that is durable and able to be cut to produce collapsible signage. Corrugated plastic is an outstanding replacement for poster board in interior applications, since its surface is resistant to most solvents, oils and water and is easily cleaned.
  
• Delrin is the trade mark name of a specific polyoxymethylene, an excellent general purpose mechanical engineering plastic that is highly versatile.
  
• Fluoroplastics, such as Teflon, are heat, moisture and wear resistant, and thus are used for many different valve, gasket and bearing applications. Fluoroplastics are flexible thermoplastics.
  
• Phenolic plastic is in the categories of polyester and vinyl ester. It is comprised of phenol and formaldehyde, has the same strength as iso-polyester and is the best material for fire safety.
  
• Plastic film is simply plastic material that has been produced in a thin, flat continuous sheet to a precise thickness.
  
• Plastic manufacturers fabricate goods and components out of plastic.
• Plastic materials are made from polymer resin and derive their name from its plastic or moldable quality. Plastic materials can be formed into any desired shape when heat and pressure are applied, and continue to retain this shape when cooled.
  
• Plastic piping is material designed to transport various liquids, such as water, chemicals, oil and fuels. Plastic piping is also used in drainage applications.
  
• Plastic rods are extruded in much the same way plastic tubing and plastic profiles are, except that plastic rods are solid instead of hollow.
• Plastic sheeting is created from continual-phase plastic in a form in which the thickness is very low in proportion to the length and width.
  
• Plastic sheets are large, flat pieces of plastic used in manufacturing.
• Plastics are made from polymer resin and are used to make components for almost every industry.
• Polycarbonate has good light transmission and stability and the highest rating of all transparent thermoplastics. Some applications for polycarbonate include electronic housings, machine guards and aircraft panels.
  
• Polyethylene is a the most common and most versatile polymer available in a range of molecular weights and structures specially configured for its use in a number of industrial, commercial and residential settings.
  
• Polypropylene (PP) is a kind of plastic that is very flexible at low temperatures and resistant to chemicals. PP is frequently used for banner materials.
  
• Polystyrene is used for such things as packaging, automotive and lighting because of its very good electrical properties and machinability.
  
• Polyurethane is used for bumpers, gears, gaskets and roll covers. Polyurethane is a tough and durable plastic that has good abrasion resistance and a high flex-life.
  
• PVC (Polyvinyl Chloride) is a very strong thermoplastic that is resistant to acids, water and abrasion.
• Thermoplastics encompass all of those plastic materials which soften and may even return to a liquid state when heated but solidify and become rigid when cooled.

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Plastic Terms

Additive - A substance that is added to a resin to enrich particular characteristics.
 
Aging - The chemical and physical changes a material undergoes over time, due to environmental forces that will deteriorate or improve the material.
 
Alloys - Combinations of polymers or copolymers with other elastomers or polymers.
 
Binder - A resin or other substance that unites particles. Binders supply mechanical strength and guarantee solidification, consistent uniformity or adhesion to a surface coating.
 
Clarity - The lack of cloudiness in a plastic material.
 
Composite - A plastic structural substance that is comprised of a blending of materials.
 
Compressive Strength - The capacity of a plastic material to withstand crushing forces.
 
Copolymer - Different monomers that chemically react with one another, resulting in a compound.
 
Cure - The process of altering properties of polymers into a state of greater stability and usability. Curing is achieved through radiation, heat or reaction with chemical additives.
 
Cure Cycle - The period of time at set conditions in which a reacting thermosetting material is cured.
 
Discoloration - A change in the original color of a plastic material due to environmental conditions, such as light exposure and chemical attack.
 
Forming - The procedure in which an existing plastic shape is changed into another one.
 
Hygroscopic - The tendency of certain plastic materials to absorb water.
 
Masterbatch - A concentration of material in a base polymer, such as pigments, additives and fillers.
 
Opaque - Plastic materials that will not transmit light.
 
Plasticizer - A high-boil organic or liquid low-melt solid, the addition of which gives flexibility to hard plastics. Plasticizers differ in their solvating capabilities and softening actions, due to the reduction of intermolecular pressures in the polymer.
 
Plastisol - A blend of resins and plasticizers that can be transformed into continuous films through the application of heat.
 
Polymer - A synthetic or natural compound of high molecular weight, which is comprised of long chains of repeating units, each relatively light and simple, including polyethylene and elastomer.
 
Reinforced Plastics - Plastic materials with increased mechanical properties, resulting from the embedding of high strength fillers in the composition.
 
Resin - A solid or pseudosolid organic material that typically has a high molecular weight with a propensity to flow when stress is applied and generally has a melting or softening range.
 
Surfactants - Chemicals that permit the formation of a close mixture or emulsion of usually mismatched substances by the alteration of the surface characteristics and the manipulation of the flowing and wetting characteristics of liquids.
 
Thermosets - Plastic compounds or resins that in their last stage are insolvable and infusible. After curing is complete, thermosets cannot be softened through heat.
 
Virgin Material - Plastic material, such as granules, pellets, floc or liquid, that has not had any processing applied to it other than what is needed for initial manufacturing.

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