What is PVB plastic

Polyvinyl Butyral Resin (PVB) is a solvent-based resin synthesized by the acetal reaction of polyvinyl alcohol (PVA) and butyraldehyde under the action of a catalyst.

Because PVB resin contains a large proportion of hydroxyl groups, it can bridge with some thermosetting resins to improve chemical resistance and hardness of the coating film.


Because of these excellent properties, PVB resins are widely used in interlayer films for glued safety glass in automobiles and buildings, rust inhibiting primers, baking lacquers, wood lacquers, printing inks, adhesives for electronic ceramics and printed circuit boards, adhesives between metal and metal, metal and plastic, modifiers for hot melt adhesives, and waterproofing for textiles. New applications in various industries are continuously being developed and applied.

The general properties of PVB are as follows.

The appearance of polyvinyl butyral (PVB) resin is white spherical porous particles or powder, and its specific gravity is 1:1; however, the filling density is only 0.20~0.35g/ml.

Thermal Properties

The glass transfer temperature (Tg) of polyvinyl butyral (PVB) resin ranges from 50°C for low recombination to 90°C for high recombination; this glass transfer temperature can also be adjusted to below 10°C by adding the appropriate amount of plasticizer.

Mechanical Properties

The coating film of polyvinyl butyral (PVB) resin has good water resistance, resistance and oil resistance (resistant to aliphatic, mineral, animal and vegetable oils, but not to grated sesame oil). PVB is widely used in printing inks and coatings because it contains high hydroxyl groups and has good dispersion of pigments.

In addition, its chemical structure contains both hydrophobic acetal and acetate groups and hydrophilic hydroxyl groups, so PVB has good adhesion to glass, metal, plastic, leather and wood.

Chemical Reaction

Any chemical that can react with secondary alcohols will also react with PVB. Therefore, in many applications, PVB is often combined with thermosetting resins to bridge the hydroxyl groups of PVB to achieve chemical resistance, solvent resistance and water resistance.

Of course, depending on the type of thermosetting resin and the mixing ratio with PVB, different properties (such as hardness, toughness, impact resistance, etc.) of the coating film can be formulated.

Safety Properties

Pure PVB is non-toxic and harmless to human body, and it can be used as a solvent with ethyl acetate or alcohol, so PVB is widely used as printing ink for food containers and plastic packaging in Europe and America.

Storage Safety Properties

PVB can be stored for two years without affecting its quality as long as it does not come into direct contact with water; PVB should be stored in a dry and cool place and protected from direct sunlight.

Solubility

PVB is soluble in alcohols, ketones, esters and other solvents. The solubility of various solvents varies depending on the composition of the functional groups of PVB. Generally speaking, alcohols are soluble, but methanol is more insoluble in high acetal groups; the higher the acetal group, the more soluble it is in ketone and ester solvents.

PVB is soluble in alcohol ether (Cellosolve) solvents; PVB is only partially soluble in aromatic solvents such as xylene and toluene; PVB is insoluble in hydrocarbon solvents.

Viscosity characteristics of PVB solutions

In general, if alcohols are used as solvents, the higher the molecular weight of the alcohol, the higher the viscosity of the PVB solution.

Aromatic solvents such as xylene and toluene and hydrocarbon solvents can be used as diluents to reduce the viscosity of PVB solutions. The effect of the chemical composition of PVB on viscosity is summarized as follows: the higher the degree of polymerization, the higher the viscosity of the solution with the same solvent and the same content of each group; the higher the acetal group or acetate group, the lower the viscosity of the solution with the same solvent and the same degree of polymerization.

Dissolution method of PVB

When mixed solvents are used, the dissolution procedure is to put aromatic solvents (e.g. xylene, toluene, etc.) or ester solvents (e.g. n-butyl acetate, ethyl acetate, etc.) into PVB slowly with stirring, and then add alcohol solvents (e.g. n-butanol, ethanol, etc.) after PVB is dispersed and swollen.

In this case, the dissolution time can be shortened by increasing the temperature; by using this dissolution method, the lump-like PVB can be avoided (because the dissolution time will be several times longer after the formation of lump-like PVB), and thus the dissolution speed can be accelerated. General aromatic and alcohol solvent ratio 60/40 to 40/60 (weight ratio), can be mixed with a lower viscosity PVB solution.

The solvent composition contains 2~3wt% of water, which can improve the hydrogen bonding of alcohol solvent and help the solubility of PVB.

Processing Properties

Although PVB resin is a thermoplastic, it has almost no processability before the addition of plasticizer, but once plasticizer is added, its processability is very easy.

For general coating and adhesive applications, plasticizers are added to change the resin properties to meet the application requirements, such as film softness, lowering the Tg point of the resin, lowering the heat sealing temperature, and maintaining low temperature softness.

Compatability

PVB is compatible with a variety of resins such as phenolic resins, epoxy resins, alkyd resins and melamine resins.

PVB and alkyd resins are partially compatible. General type PVB and low molecular weight epoxy resin can be compatible, while high molecular weight epoxy resin needs to choose high acetal degree PVB to be mutually compatible.