The properties of pva
Polyvinyl alcohol (PVA) is a water-soluble, nontoxic and odourless synthetic polymer. It is made using a vinyl acetate monomer by subjecting it to polymerisation and partial hydrolysis. PVA is granular and white, and only dissolves in hot water.
It is usually prepared by dissolving it in water, and letting the water evaporate to form transparent films with exceptional strength and resistance to tearing. PVA is commonly used in making adhesive, paper coatings, textiles, films, sponges and building products such as ceramics and cements.
Adhesive, Emulsifying and Film-forming Properties
PVA has excellent adhesive, emulsifying and film-forming properties. Because of its excellent adhesive property, it is commonly used in binding papers, solid fiberboards and corrugated boxes. Textiles also benefit from PVA, providing flexibility and abrasion resistance. A PVA sponge is also available, and this particular sponge can absorb water up to 12 times its dry weight. It can also withstand 90 degrees Celsius without experiencing any deformation.
As a film, PVA becomes transparent and resistant to tearing and punctures. It is commonly used in laundry bags and dissolvable packages. A biodegradable PVA polymer has also been developed, and is mostly used as a replacement to non-biodegradable plastic bags.
Resistance to Impurities
PVA is inherently resistant to organic solvents, oil and grease. It is used as a greaseproof coating and unit packages for medical equipment and tools to ensure they are free from any impurities. It is also an impermeable material to most natural gases, ensuring materials packed in PVA will not be contaminated.
Physical and Chemical Properties
PVA's flash point is 79 degrees Celsius, while its melting point is less than or equal to 200 degrees Celsius. Its density ranges from 1.19 to 1.31g/cm3. It can also release toxic fumes when burnt, and reacts with strong acids and oxidants. In large amounts, it can be hazardous to the environment, especially if it's mixed with water and comes in contact with fish.
It is essentially nontoxic for human beings as long as it is not burnt or melted with fire. There is also no proof that PVA posts any inhalation risk and physical dangers to humans.