PVC (Polyvinyl Chloride)
Introduction to PVC
Polyvinyl chloride or PVC is a widely used synthetic plastic polymer or resins and are broadly classified into (a) thermoplastic resins and (b) thermosetting resins. Thermoplastic resins can be re-softened thermally and the thermosetting resins are thermally hardened and cannot be re-softened.
Thermoplastics already have additives (antioxidants) blended into the material and are usually supplied as pelletised compounds. PVC resin is usually in powder form and since it is resistant to degradation and oxidation, it can be stored for long periods.
Properties of PVC
PVC is light weight, very cost effective and with an added value of durability and low maintenance, it has been a very popular material for construction applications for decades.
● Chemical Stability PVC has an amorphous structure with polar chlorine atoms in the molecular structure whilst olefin plastics have only carbon and hydrogen atoms in their molecular structures. So in terms of performance and functions, it is more chemically stable when compared to other general purpose plastics.
● Safe material It is non-toxic and is a safe material that has been the most widely used thermoplastic material in medical devices. Since there is a high degree of biocompatibility between PVC and the patient’s blood/tissue, it is very useful because the contact time between the plastic and the tissue/blood may be quite lengthy.
● Fire Resistant
PVC products have fire resistant properties because of its high chlorine component. It’s a material with minimum risk to fire since its ignition temperature is as high as 455°C so it’s difficult to ignite. Although PVC products will burn but they will self-extinguish once the fire source is removed and there is less possibility of the fire spreading to nearby materials. Furthermore, the heat production is comparatively lower and they tend to char rather than produce flaming droplets.
● Durability The durability of PVC is seen from its resistance to weathering, to corrosion, to chemical rotting, to abrasion and to shock. Its chemical structure allows it to be highly resistant to oxidation and is very durable.
● Oil/Chemical resistance PVC is resistant to acid, alkali and almost all inorganic chemicals and also does not easily dissolve in other organic solvents. It is thus best used in exhaust gas ducts, sheets used in construction, bottles, tubes and hoses.
● Mechanical stability PVC has a stable mechanical strength. Although it is a viscoelastic material, its creep deformation is very low compared with other plastics. PVC products have excellent strength. ● Versatility PVC mixes well with various other substances. The desired physical properties of end products such as resistance to microbial growth, elasticity, fire-retardation, flexibility, impact resistance can be customised by adding additives, plasticisers, colouring agents and modifiers. This flexibility is also extremely beneficial for recycling. PVC allows for ease of adhesion, colouring and printing and since pre-treatment is not required, it is used in various decorative applications. The physical properties of this material ensures that designers are given a free reign when designing new products and developing solutions where it is used as a replacement or refurbishment material.
Applications in real world
PVC's relatively low cost, biological and chemical resistance and workability have resulted in it being used for a wide variety of applications. PVC or Polyvinyl chloride is fast replacing traditional building materials such as wood, metal, concrete, rubber, glass and clay in many applications as a modern alternative. It is used in building and construction, flooring and roofing foils, wall coverings, window frames and doors and many other applications.
Rigid PVC is suitable for pipe construction especially sewage pipes, drainpipes, gutters and downspouts and for fresh and waste water systems and has almost entirely replaced the use of cast iron for drainage and plumbing; non-food packaging; bottles and bank or membership cards. Flexible PVC is suitable for applications where it replaces rubber such as in electrical cable insulation since PVC is a good insulator; inflatable products; as imitation leather and clothing. PVC fabric is used in coats, shoes, jackets, skiing equipment and bags because of its water resistant property. In its use for signage or scaffolding billboards, PVC is manufactured in flat sheets in a variety of thicknesses.
In the health industry, PVC accounts for almost one third of medical plastics currently in use. PVC’s durability and strength give it the flexibility necessary for applications such as blood bags and IV containers. In medical product applications where it is critical to eliminate sources of infection, PVC products can be easily sterilized using steam, radiation or ethylene oxide and with its excellent water and chemical resistance, solutions can be kept sterile. It is most suitable for use as flooring in operating theatres which is easy to clean. PVC’s versatility ensures that it can easily be extruded to make IV tubing, thermoformed to make 'blister' packaging or blow moulding to make hollow rigid containers for a variety of medical purposes.
Video explains about Polyvinyl Chloride.Courtesy of Danial Shafe