PVC and PET
Polyvinyl chloride also known as polyvinyl or vinyl, commonly abbreviated PVC, is the world's third-most widely produced synthetic plastic polymer, after polyethylene and polypropylene.
PVC comes in two basic forms: rigid (sometimes abbreviated as RPVC) and flexible. The rigid form of PVC is used in construction for pipe and in profile applications such as doors and windows. It is also used in making bottles, non-food packaging, and cards (such as bank or membership cards). It can be made softer and more flexible by the addition of plasticizers, the most widely used being phthalates. In this form, it is also used in plumbing, electrical cable insulation, imitation leather, signage, phonograph records, inflatable products, and many applications where it replaces rubber. Pure polyvinyl chloride is a white, brittle solid. It is insoluble in alcohol but slightly soluble in tetrahydrofuran.
Roughly half of the world's polyvinyl chloride resin manufactured annually is used for producing pipes for municipal and industrial applications. In the water distribution market, it accounts for 66% of the market
in the U.S., and in sanitary sewer pipe applications, it accounts for 75%. Buried PVC pipes in both water and sanitary sewer applications that are 4 inches (100 mm) in diameter and larger are typically joined by means of a gasket-sealed joint. The most common type of gasket utilized in North America is a metal reinforced elastomer, commonly referred to as a Rieber sealing system. Its light weight, low cost, and low maintenance make it attractive. However, it must be carefully installed and bedded to ensure longitudinal cracking and over belling does not occur. Additionally, PVC pipes can be fused together using various solvent cements, or heat-fused (butt-fusion process, similar to joining high-density polyethylene (HDPE) pipe), creating permanent joints that are virtually impervious to leakage. In February 2007 the California Building Standards Code was updated to approve the use of chlorinated polyvinyl chloride (CPVC) pipe for use in residential water supply piping systems. CPVC has been a nationally accepted material in the U.S. since 1982; California, however, has permitted only limited use since 2001. The Department of Housing and Community Development prepared and certified an environmental impact statement resulting in a recommendation that the commission adopt and approve the use of CPVC. The commission's vote was unanimous, and CPVC has been placed in the 2007 California Plumbing Code.
- ELECTRIC CABLES
PVC is commonly used as the insulation on electrical cables such as teck; PVC used for this purpose needs to be plasticized. Flexible PVC coated wire and cable for electrical use has traditionally been stabilized with lead, but these are being replaced with calcium-based systems. In a fire, PVC-coated wires can form hydrogen chloride fumes; the chlorine serves to scavenge free radicals and is the source of the material's fire retardance. While hydrogen chloride fumes can also pose a health hazard in their own right, it dissolves in moisture and breaks down onto surfaces, particularly in areas where the air is cool enough to breathe, and is not available for inhalation. Frequently in applications where smoke is a major hazard (notably in tunnels and communal areas), PVC-free cable insulation is preferred, such as low smoke zero halogen (LSZH) insulation.
PVC is a common, strong but lightweight plastic used in construction. It is made softer and more flexible by the addition of plasticizers. If no plasticizers are added, it is known as uPVC (UN plasticized polyvinyl chloride) or rigid PVC.
UPVC is extensively used in the building industry as a low maintenance material, particularly in Ireland, the United Kingdom, in the United States and Canada. In the U.S. and Canada it is known as vinyl or vinyl siding. The material comes in a range of colors and finishes, including a photo-effect wood finish, and is used as a substitute for painted wood, mostly for window frames as it does not decompose and is weather-resistant and sills when installing insulated glazing in new buildings, or to replace older single-glazed windows. Other uses include fascia, and siding or weatherboarding. This material has almost entirely replaced the use of cast iron for plumbing and drainage, being used for waste pipes, drainpipes, gutters and downspouts. UPVC is known as having strong resistance against chemicals, sunlight, and oxidation from water.
Polyvinyl chloride is formed in flat sheets in a variety of thicknesses and colors. As flat sheets, PVC is often expanded to create voids in the interior of the material, providing additional thickness without additional weight and minimal extra cost (see Closed-cell PVC foam board). Sheets are cut using saws and rotary cutting equipment. Plasticized PVC is also used to produce thin, colored, or clear, adhesive-backed films referred to simply as vinyl. These films are typically cut on a computer-controlled plotter (see Vinyl cutter) or printed in a wide-format printer. These sheets and films are used to produce a wide variety of commercial signage products, including car body stripes and stickers.
The two main application areas for single-use medically approved PVC compounds are flexible containers and tubing: containers used for blood and blood components, for urine collection or for ostomy products and tubing used for blood taking and blood giving sets, catheters, heart-lung bypass sets, hemodialysis sets etc. In Europe the consumption of PVC for medical devices is approximately 85,000 tons each year. Almost one third of plastic-based medical devices are made from PVC. The reasons for using flexible PVC in these applications for over 50 years are numerous and based on cost effectiveness linked to transparency, light weight, softness, tear strength, kink resistance, suitability for sterilization and biocompatibility.
Flexible PVC flooring is inexpensive and used in a variety of buildings, including homes, hospitals, offices, and schools. Complex and 3Ddesigns are possible, which are then protected by a clear wear layer. A middle vinyl foam layer also gives a comfortable and safe feel. The smooth, tough surface of the upper wear layer prevents the build-up of dirt, which prevents microbes from breeding in areas that need to be kept sterile, such as hospitals and clinics.
- WIRE ROPE
PVC may be extruded under pressure to encase wire rope and aircraft cable used for general purpose applications. PVC coated wire rope is easier to handle, resists corrosion and abrasion, and may be colorcoded for increased visibility. It is found in a variety of industries and environments both indoor and out.
- OTHER APPLICATIONS
PVC has been used for a host of consumer products. One of its earliest mass-market consumer applications was vinyl record production. More recent examples include wallcovering, greenhouses, home playgrounds, foam and other toys, custom truck toppers (tarpaulins), ceiling tiles and other kinds of interior cladding.
PVC piping is cheaper than metals used in musical instrument making; it is therefore a common alternative when making instruments, often for leisure or for rarer instruments such as the contrabass flute.
Polyethylene terephthalate (sometimes written poly(ethylene terephthalate)), commonly
abbreviated PET, PETE, or the obsolete PETP or PET-P, is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and
foods, thermoforming for manufacturing, and in combination with glass fiber for engineering resins.
It may also be referred to by the brand name Dacron; in Britain, Terylene; or, in Russia and the former Soviet Union, Lavsan.
The majority of the world's PET production is for synthetic fibers (in excess of 60%), with bottle production accounting for about 30% of global demand. In the context of textile applications, PET is referred to by its common name, polyester, whereas the acronym PET is generally used in relation to packaging. Polyester makes up about 18% of world polymer production and is the fourth-most-produced polymer; polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) are first, second and third, respectively.
PET consists of polymerized units of the monomer ethylene terephthalate, with repeating (C10H8O4) units. PET is commonly recycled, and has the number "1" as its resin identification code (RIC).
Depending on its processing and thermal history, polyethylene terephthalate may exist both as an
amorphous (transparent) and as a semi-crystalline polymer. The semi crystalline material might appear transparent (particle size less than 500 nm) or opaque and white (particle size up to a few micrometers) depending on its crystal structure and particle size.
The monomer bis (2-hydroxyethyl) terephthalate can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct, or by transesterification reaction between ethylene glycol and dimethyl terephthalate (DMT) with methanol as a by product. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with water as the by product.