POLYVINYL CHLORIDE (PVC)
PVC is the second most widely used thermoplastic in the world, behind only polyethylene
. It is obtained from 57% of inputs from sea salt or land (rock salt), and only 43% from non-renewable sources such as oil and natural gas. Its polymerization is achieved by the reaction of free radicals of vinyl chloride, where the polymerization technique by suspension, emulsion, solution or by mass can be employed. PVC has its structure essentially linear, but there may be a low number of short chain branches.
The glass transition temperature varies according to the polymerization method employed, but always within the range of 140 to 176°F (60 to 80°C). Like polycarbonate
, PVC is naturally an anti-flame plastic, but due to another mechanism: the burning of the polymer causes the release of HCl (muriatic acid), which in the form of gas (hydrogen chloride), takes the place of air In the burning area because it is denser. PVC also has excellent chemical resistance to acids, alkalis, alcohols, oils and many other hydrocarbons, which makes it an option for application in parts that have contact with chemicals.
Most popular PVC application: tubes in building
The great differential of PVC compared to other thermoplastics is its versatility, the inclusion of low molecular weight plasticizers leaves the resin flexible or rubbery, this addition of plasticizer also lowers the glass transition temperature. Non-modified PVC has high rigidity. Other additives that are widely used with PVC are: stabilizers, pigments, lubricants and fillers. The fillers are generally used for cost reduction, and the main ones are talc, calcium carbonate and clay.
PVC is completely non-toxic and inert, which means that it can be applied to medical and hospital products, food and toy films; provided that the additives also possess these characteristics, obviously.
The major problem with PVC is its thermal sensitivity, for which a lot of control is required in order to avoid the decomposition of the polymer during processing. Added to this are the small amounts of HCl that are released from the resin and can cause corrosion of the equipment if its metal parts are not properly treated. For external applications, PVC requires UV stabilizer, otherwise HCl may also be released.
PVC can be processed by blowing, extrusion of various forms, injection, compression, calendering, thermoforming, among others, due to the wide range of grids between rigid and flexible PVC.
- Available in a wide range of properties, from flexible to rigid PVC
- High chemical resistance
- Nontoxic and inert
- Resistant to the action of fungi, bacteria, insects and rodents
- Good thermal, electrical and acoustic insulation
- Impermeable to gases and liquids
- Long service life
- Does not spread flames
pipes, ceilings, covers for mobile, gloves, windows, boots, shoes, clothes, cards etc.
HARPER, Charles A.; PETRIE, Edward M. Plastics Materials and Process: A Concise Encyclopedia. Hoboken: John Wiley & Sons, Inc., 2003.
CANEVAROLO JR., Sebastião V. Ciência dos Polímeros: Um texto básico para tecnólogos e engenheiros. 2.ed. São Paulo: Artliber Editora, 2002.
WIEBECK, Hélio; HARADA, Júlio. Plásticos de Engenharia: Tecnologia e Aplicações. São Paulo: Artliber Editora, 2005.
© 2010-2017 - Tudo sobre Plásticos.
All rights reserved.