March 12, 2025 | UR Gate
Polyvinyl Alcohol (PVA) – [-CH2-CH(OH)-]ₙ
PVOH; Poly(Ethenol), Ethenol, homopolymer; PVA; Polyviol; Vinol; Alvyl; Alcotex; Covol; Gelvatol; Lemol; Mowiol; Mowiflex, Alcotex, Elvanol, Gelvatol, Lemol, Nelfilcon A, Polyviol und Rhodoviol
Introduction
Polyvinyl Alcohol (PVA) is a water-soluble synthetic polymer with
unique physical and chemical properties, making it widely used in
various fields, from pharmaceuticals and food industries to industrial
and environmental applications. PVA is biodegradable, making it an
environmentally friendly option.
Chemical Composition and Preparation
Polyvinyl Alcohol consists of repeated vinyl alcohol units, but it is
not synthesized directly from vinyl alcohol due to its instability.
Instead, PVA is produced through the hydrolysis of polyvinyl acetate
(PVAc) using an alkaline solution such as sodium hydroxide (NaOH). This
process replaces acetate groups with hydroxyl groups (-OH), which are
responsible for the polymer’s water solubility and unique chemical
reactions.
Chemical Structure:
Molecular Formula:
(C₂H₄O)ₙ
Structural Formula:
[-CH₂-CH(OH)-]ₙ
General Equation for Hydrolysis:
Physical and Chemical Properties
- Water Solubility: PVA dissolves easily in hot water, depending on the degree of hydrolysis.
- Flexibility and Viscosity: It has film-forming properties, making it ideal for industrial applications.
- Chemical Reactivity: It interacts with borax to form a gel (Slime) due to hydrogen bonding between polymer chains.
- Biodegradability: It has a high degradation capacity in the environment, making it suitable for eco-friendly applications.
Practical Applications
- Paper and Textile Industries: Used as an adhesive and color stabilizer.
- Pharmaceutical Industry: Used in the composition of drug capsules and water-soluble coatings.
- Adhesives and Coatings: A key component in many industrial adhesives.
- Biodegradable Plastic Films: Used in the production of food packaging materials.
- Chemical Applications: Used in the preparation of gels like slime when reacting with borax.
PVA Reaction with Borax to Form Slime
When a sodium borate (Na₂B₄O₇) solution is added to a PVA solution,
cross-links form between polymer chains via the borate ion (B(OH)₄⁻),
creating a rubbery gel known as slime. This reaction is widely used in
chemical research and educational experiments.
Reaction Equation:
Sustainability and Environmental Impact
PVA is biodegradable but requires specific conditions, such as the
presence of microbes capable of breaking it down. Current research is
focused on improving its efficiency in environmental applications, such
as water purification and the development of biodegradable
materials.
Conclusion
Polyvinyl Alcohol (PVA) remains a versatile material due to its unique
solubility, flexibility, and chemical reactivity. From industrial
applications to educational chemistry, PVA continues to be significant
in various fields, making it an essential topic for study and
sustainable use.