Frecuently Asked Questions
- How many types of plastics resins are there?
- Where do plastics come from?
- Could the plastic be combined with metallic materials?
- How are the plastics made?
- How does plastic become objects?
- Glossary of Plastic Industry
How many types of plastics are there?
At the present time there are marketed around 30 families of plastics with their corresponding formulas. Among those most used we can find the Polyvinylidene Chloride (PVC), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Polypropylene (PP) and the Polystyrene (PS), among others.
Where do the plastics come from?
The most important ingredient of plastics is petroleum. Naphtha is distilled and starting from this fraction the matters prevails is obtained. It is important to know that 4% of the world production of petroleum is only dedicated to manufacture plastics, 6% goes to other industries and 90 remaining% is used to fuel for heating and locomotion.
Can the plastic be combined with metallic materials?
Plastic materials are innocuous and completely adaptive to metallic constructions.
How are plastics made?
The production of plastics is a process called polymerization: chemical reaction with small molecules called monomers combine to each other to form other much bigger molecules to form chains which are called polymers, in those it repeats the structure of the original ones. The monomer is the matters prevails that are manufactured starting from the petroleum. They are presented in diverse forms but, usually, in way of granules -screening -, powder, pastures, among others.
How does plastic become an objects?
Once created, plastic polymers can be transformed in different products for the use in various applications .That transformation is carried out through processes like extrusion, injection or compression molding in which it takes advantage of the "plasticity of resin". Plastic resins are molded by using high temperature, pressure and molds to make the final products, for domestic, medical and industrial use to name a few.
GLOSSARY OF PLASTIC INDUSTRY |
Additive: A substance compounded into a resin to enhance or improve certain characteristics.
Adhesive Assembly: The process of joining two or more plastic parts by means of an adhesive.
Aging: The process of, or the results of, exposure of plastics to natural or artificial environmental conditions for a prolonged period of time.
Ambient Temperature: The temperature of a medium surrounding an object. The term is often used to denote prevailing room temperature.
Antioxidant: Additive used to reduce degradation from oxygen attack at normal or elevated temperatures. Sources such as heat, age, chemicals, and/or stress may accelerate oxygen attack.
Assembly: The process of joining parts by any of several methods.
Barrel: The section of a molding machine that contains the feed screw, also the section where resin heating and mixing occurs.
Blow Molding: A widely used process for the production of hollow thermoplastic shapes. The process is divided into two general categories: extrusion blow molding and injection blow molding. These processes are typically used to manufacture plastic bottles and containers.
Extrusion Blow Molding: A parison or tube of plastic material is dropped or lowered from an extruder. Mold halves close around the parison, which is then expanded against the cavity wall by the injection of air. (Modern Plastics Encyclopedia 1995)
Injection Blow Molding: A two-stage process where plastic is first injection molded into a preform. The preform is then transferred to a blow mold where it is expanded.
Bubbles: Air or gas pockets that have formed in the material of the component. Bubbles may vary in size.
Bulk Density: A measurement of mass per unit volume of materials (such as powders) that pressure.
Co-Injection: Simultaneous or near simultaneous injection of multiple materials.
Cold Molding: The process of compression molding involving shaping an unheated compound in a mold under pressure then heating the article to cure it.
Compression Molding: A method of molding in which the molding material, generally preheated, is placed in an open heated mold cavity, the mold is closed with a top force pressure is applied to force the material into contact with all mold areas.
Copolymer: The chemical reaction of two different monomers with each other, result in a unique new polymer.
Density – Weight per unit volume of a substance. Density is expressed in grams per cubic centimeter, pounds per cubic foot, etc..
Drying: The removal of moisture from the resin pellets by exposure to certain time and temperature. All Hydroscopic Material must be dried prior to molding.
Ejection Pin: A rod, pin or sleeve that pushes a molded part off of a core or out of a cavity of a mold.
Ejector Rod: A bar that actuates the ejector assembly when the mold opens.
Elastomer: A rubber-like material which at room temperature can be stretched repeatedly to at least twice its original length and, upon immediate release of the stress, will return with force to its approximate original length.
Extrusion: The process of forming continuous shapes by forcing a molten plastic material through a die. One of the most common plastics processing techniques covering a vast range of applications in which resins are melted, heated and pumped for processing. Extrusion machines accomplish these tasks by means of one or more internal screws. In extrusion, the material to be processed is sheared between the root of the screw and the wall of the barrel that surround it. This process produces frictional energy that heats and melts the substance as it is conveyed down the barrel. Melted extrudate from the machine is further processed after the extrusion phase, which typically produces pellets, sheet, cast film, blown film, fibers, coatings, pipes, profiles or molded parts
Fabricating: The manufacture of plastic products by appropriate operations. This includes plastics formed into molded parts, rods, tubes, sheeting, extrusion and other forms by methods including punching, cutting, drilling, tapping, fastening or by using other mechanical devices.
High Density Polyethylene (HDPE): HDPE refers to a plastic used to make bottles for milk, juice, water and laundry products. Unpigmented HDPE bottles are translucent and have good barrier properties and stiffness. They are well suited to packaging products with short shelf lives such as milk. Pigmented HDPE bottles generally have better stress crack and chemical resistance than bottles made with unpigmented HDPE. These properties are needed for packaging such items as household chemicals and detergents, which have a longer shelf life. Injection-molded HDPE is resistant to warpage and distortion. It is used for products such as margarine tubs and yogurt containers
Hygroscopic: readily absorbs moisture.
Injection Blow Molding: Blow molding process by which the plastic parison to be blown is formed by injection molding.
Injection Molding Pressure: The pressure applied to the cross-sectional area of the molding cylinder.
Injection Molding: The method of forming objects from granular or powdered plastics, most often of the thermoplastic type, in which the materials is fed from a hopper to a heated chamber in which it is softened, after which a ram or screw forces the material into a mold. Pressure is maintained until the mass has hardened sufficiently for removal from the mold
Injection Pressure: The pressure on the face of the injection screw or ram when injecting material into the mold, usually expressed in PSI.
Insert Molding: Insert molding is the process of molding plastic around preformed metal inserts. This process is compatible with both thermoplastic and thermoset materials.
Liquid Injection Molding (LIM): The process that involves an integrated system for proportioning, mixing, and dispensing two component liquid resin formulations and directly injecting the resultant mix into a mold which is clamped under pressure.
Low Density Polyethylene (LDPE): A plastic used predominantly in film applications due to its toughness, flexibility and relative transparency. LDPE has a low melting point, making it popular for use in applications where heat sealing is necessary. Typically, LDPE is used to manufacture flexible films such as those used for plastic retail bags and garment dry cleaning and grocery bags. LDPE is also used to manufacture some flexible lids and bottles, and it is widely used in wire and cable applications for its stable electrical properties and processing characteristics
Melt Flow Rate: A measure of the molten viscosity of a polymer determined by the weight of polymer extruded through an orifice under specified conditions of pressure and temperature. Particular conditions are dependent upon the type of polymer being tested.
Mold (v): To impart shape to a plastic mass by means of a confining cavity or matrix.
Monomer: A relatively simple molecular structure, usually containing carbon and of low molecular weight, which can react to form a polymer by combination with itself or with other molecules and energy.
Over Molding: A process in which a mold cavity is first partially filled with one plastic and then a second shot is injected to encapsulate the first shot.
Pellets: Tablets or granules of uniform size, consisting of resins or mixtures of resins with compounding additives which have been prepared for molding operations by extrusion and chopping into short segments.
Plastic: A material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight, is solid in its finished state, and, at some stage in its manufacture or processing into finished articles, can be shaped by flow.
Polymer: High-molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the mer: e.g. polyethylene, rubber, cellulose. If two or more monomers are involved, a copolymer is obtained.
Polyethylene: A thermoplastic material composed of polymers of ethylene. It is normally a translucent, tough, waxy solid unaffected by water and a large range of chemicals.
Polypropylene: A tough, light-weight rigid plastic made by the polymerization of high-purity propylene gas in the presence of an organometallic catalyst at relatively low pressures and temperatures.
Polystyrene: A water-white thermoplastic produced by the polymerization of styrene (vinyl benzene).
Polyvinyl Chloride (PVC): A thermoplstic material composed of polymers of vinyl chloride. PVC is a colorless solid with outstanding resistance to water, alcohols, and concentrated acids and alkalies
Polypropylene (PP): Polypropylene has excellent chemical resistance is strong and has the lowest density of the plastics used in packaging. It has a high melting point, making it ideal for hot-fill liquids. In film form it may or may not be oriented (stretched). PP is found in everything from flexible and rigid packaging to fibers and large molded parts for automotive and consumer products
Resin: Any class of solid or semi-solid organic products of natural or synthetic origin, generally of high molecular weight, with no definite melting point. Most resins are Polymers
Solvents: Substances with the ability to dissolve other substances.
Thermoplastic Elastomers: The families of polymers that resemble elastomers in that they can be repeatedly stretched without distortion of the unstressed part shape, but are true thermoplastics and thus do not require curing.
Thermoplastic: material that will repeatedly soften when heated and harden when cooled.
