PVC (Polyvinyl Chloride) - Discoveries and Uses

PVC (Polyvinyl Chloride)

• PVC is an economical and versatile thermoplastic polymer.
• It is the world's third largest thermoplastic material, used in building and construction, medical devices, pipes, wire insulation, etc.
• Available in powder or granules form.
• It's lightweight, durable, and inexpensive, replacing traditional building materials like wood, metal, concrete, etc.

Discovery of PVC

• Accidentally discovered in 1872 by German chemist Eugen Baumann.
• The polymer appeared as a white solid inside a vinyl chloride flask exposed to sunlight.
• In the early 20th century, various attempts to utilize PVC in commercial products were made by Russian, German chemists but difficulties in processing the rigid, brittle polymer hindered their efforts.
• Waldo Semon and B.F. Goodrich in 1926 developed a method to plasticize PVC, creating a more flexible and workable material. This material achieved widespread commercial use.

First Use of PVC

• Initially used as a water-resistant fabric coating.
• Demand for PVC, as an insulator for wiring on military ships, rose during World War II.
• PVC tube production skyrocketed in the 1950s.
• New applications in construction, inflatable structures, and fabric coatings followed.

Properties of PVC

• Rigid PVC: High hardness and mechanical properties. Mechanical properties increase with molecular weight but decrease with temperature increase. Elastic modulus can reach 1500-3000 MPa.
• Flexible PVC: Lower mechanical properties. Elastic modulus is 1.5-15 MPa. Elongation at break 200%-450%. Static friction factor 0.4-0.5, dynamic friction factor 0.23.
• Thermal properties: Poor heat stability. Decomposes above 140°C. Melting temperature 160°C. Low linear expansion coefficient. Flame retardant.
• Electrical properties: Good insulation but inferior to non-polar polymers. High dielectric constant, dielectric loss tangent, and volume resistivity. Suitable for medium and low voltage, low frequency insulation.

Basic Forms of PVC

• Flexible/Plasticized PVC: Made by adding plasticizers to PVC, lowering crystallinity for more flexibility and clarity, sometimes called PVC-P).
• Rigid/Unplasticized PVC: (UPVC, PVC-U, or uPVC): Stiff, cost-effective, and resistant to impact, water, weather, chemicals, and corrosion.
• Chlorinated Polyvinyl Chloride (CPVC): High chlorine content provides durability, chemical stability, and flame retardancy; withstands various temperatures.
• Molecular Oriented PVC (PVC-O): Reorganizes the PVC-U amorphous structure into a layered form; improves stiffness, fatigue resistance, and lightweight.
• Modified PVC (PVC-M): An alloy of PVC with modifying agents for increased toughness and impact resistance.

Manufacturing of PVC

• Extraction of salt and hydrocarbons.
• Production of ethylene and chlorine from salt and hydrocarbons.
• Mixing of chlorine and ethylene to produce vinyl chloride monomer.
• Polymerization of vinyl chloride monomer to produce PVC.
• Blending of PVC polymers with other materials (e.g., plasticizers).

Applications of PVC

• Medical: Blood bags, blood vessels, artificial skin, storage bags, medical devices, blood transfusion sets.
• Building & Construction: Flooring, roofing, pipes, windows, doors, frames, cables, gutters, shower curtains, fascia, and weatherboarding.
• Electrical: Wires, cables, insulation, switchboards, sockets, fan boxes, casing, and miscellaneous items.
• Transport: Automotive parts, pipes, and miscellaneous items.
• Sports: Surfaces, sports equipment, furniture and seating.

Advantages of PVC

• Lighter weight
• Heat resistant
• Non-conductive
• Wide variety of shapes and designs
• Recyclable
• Easily transported
• Affordable

Disadvantages of PVC

• Not the most environmentally friendly
• Harmful by-products during creation and decomposition
• Not recommended above 343K (though it can tolerate 353K for short periods)
• Sensitive to UV and oxidative degradation
• Emits HCl when decomposed
• Production causes pollution

Applications in Architecture

• PVC coated polyester fabrics are robust, translucent, and waterproof, suitable for tensile fabric and membrane structures.

Applications in London Olympics

• PVC was extensively utilized, especially in temporary structures. Some structures were subsequently recycled and re-used in Brazil.

Wuhan Train Station

• The roof's design is noteworthy, integrating sweeping lines and symbolism.
• Incorporates flexible PVC or a similar material in the structure.

PVC in the Market

• Provides various products based on multiple uses (Water supply & plumbing, Construction, etc.)

PVC in Electronics

• Used in various components of electrical equipment.

PVC Pipes and Fittings

• Highly durable and resistant to bacteria, taste, and smells in transferred water.
• Good insulation properties affecting temperature of the water.
• Fittings include tees, elbows, caps, and more.

PVC Windows, Doors, and Frames

• Rust and rot proof, termite proof, and water proof.
• Unaffected by climate and other factors.
• Require minimal maintenance, with occasional cleaning.

PVC Cables and Gutters

• Cables used as replacements for rubber, in telecommunications, and electric blankets are recyclable.
• Gutters are easy to install and durable and unaffected by rust, though can get damaged by tree branches, UV rays, and shattering.

PVC as a Composite Material

• PVC mixed with natural fibers offers an alternative material for reinforcing and strengthening it.
• Adding natural fibers can improve stiffness while reducing density.

Wood PVC Composite, Sugarcane Bagasse Reinforced PVC Composite, and Banana Particulate Reinforced PVC Composite

• Compositions include wood flour, PVC resin, compatibilities, and/or various reinforcements which improve strength and durability.

PVC Advancements

• Improvements in PVC technology are being made for pipes, construction, and other applications due to factors like improved durability, longevity, and energy efficiency.

References

• Various websites (e.g., omnexus, slide share, Wikipedia)
• Books (e.g., Engineering Materials by Rangwala)