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Polyvinyl butyral - special polymer with useful properties
Polyvinyl butyral
Polyvinyl butyral (PVB for short) is a water-insoluble thermoplastic with excellent binding and film-forming properties.
It is characterised by its good solubility in organic solvents and compatibility with other polymers. Its excellent elastic properties and optical transparency make PVB suitable for a wide range of applications.
Depending on the application, high or low viscosity PVBs can be used, whose glass transition temperature is adapted to the target application. Increased stability can be achieved through cross-linking. PVB can therefore be used as a binder for paints, primers, adhesives, metal powders or ceramics, as well as an intermediate film for laminated safety glass products and is a polymer that has become indispensable in the industry.
Polyvinyl butyral is synthesized by the acetylation of polyvinyl alcohol with butyraldehyde (also known as butanal). The chemical belongs to the polyvinyl acetal family.
Polyvinyl alcohol itself is produced through the hydrolysis of polyvinyl acetate. Some of the acetyl groups remain intact after this reaction. These residual acetyl groups determine how well the substance dissolves in other chemicals. A low degree of acetylation will result in high water solubility, whereas a high degree of acetylation will promote the chemical's ability to dissolve in alcohol.
When it comes to polyvinyl butyral interlayers for laminated glass, complete functionalization (80 percent) is undesirable because unreacted hydroxyl (OH) groups facilitate adhesion to glass surfaces.
Polyvinyl butyral, CAS No. 63148-65-2, is a synthetic polymer that is part of the polyvinyl acetal family. It is manufactured and processed using thermoplastic methods. That is why it appears as a fine, free-flowing white powder. The properties of polyvinyl butyral resins vary according to their degree of acetylation and molecular weight.
Their strength and elasticity depend on their molecular weight, for example. In contrast, their water absorption capacity and solubility in non-polar solvents are determined by their degree of acetylation. Nevertheless, in general, polyvinyl butyral resins are highly compatible with organic solvents and other polymers.
All types of polyvinyl butyral have a few things in common: They can dissolve in almost all organic solvents and are compatible with plasticizers and other resins. Furthermore, they have good light resistance and are heat-sealable at temperatures in excess of 120 degrees Celsius.
The related benefits of polyvinyl butyral at a glance:
- Excellent adhesive and film-forming properties
- High water resistance
- Optical clarity
- High bond strength
- Good elasticity
- Exceptional processability
These properties make the chemical a popular binder and hot-melt adhesive in many applications.
Industries
Polyvinyl butyrals offer excellent properties in the following applications:
- Primers and coatings
- Printing inks for packaging
- Films for laminated safety glass
- Binder for ceramics and metal powder
- Adhesives
- Coatings for retro-reflective traffic signs and road markings
- Binder for many special applications
- Use in thermoplastic applications
One major application of polyvinyl butyral is as a hot-melt adhesive to bind glass panels together for use in windows and other applications. Due to its extremely high tensile strength and ability to bind glass splinters, polyvinyl butyral is commonly used as an interlayer film in laminated safety glass.
For instance, the polymer layer between the glass panels of a windshield is made of polyvinyl butyral most of the time.
Because this compound is able to adhere very well to glass, it is perfect for bonding glass panels together or to other materials. Polyvinyl butyral can be applied as a solution or in a molten state.
The manufacture of laminated glass involves bonding sheets of glass together using polyvinyl butyral resin, plasticizers and other substances. This process takes place under high heat and pressure.
Polyvinyl butyral resins are also commonly used as binders in inks, paints and primers. Regardless of the application, polyvinyl butyral is able to adhere exceptionally well to virtually any materials due to its excellent bonding properties.
Their optical clarity and excellent adhesive and film-forming properties make polyvinyl butyral resins a truly versatile ingredient in adhesion primers, anti-corrosion primers, stove enamel and glazes.
