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PVA application in the adhesive

PVA application in the adhesive

Polyvinyl alcohol resin has been used as a modifier of polyvinyl acetate emulsion adhesives for more than 40 years due to its many outstanding characteristics.

The adhesion of Polyvinyl alcohol to cellulose substrates (such as paper and wood) is particularly good. Adding it to the polyvinyl acetate emulsion will increase the efficiency and the tensile strength of the resulting adhesive. Polyvinyl alcohol as an additive or modifier in polyvinyl acetate emulsion-based adhesives and solid fiber lamination and spiral tube winding adhesives can provide unparalleled effects.

This passage is going to talk about the followings of Polyvinyl alcohol application:

(1) What is PVA?

(2) Use and performance of PVA adhesive

(3) Precautions for PVA and absorbent surface

 

(1) What is PVA?

Polyvinyl alcohol, also known as PVOH, PVA or PVAL, is a synthetic polymer that is soluble in water. It is effective in film formation and emulsification, and has adhesive quality. It has no odor, is non-toxic, and is resistant to grease, grease and solvents. It is malleable, but has high strength, good flexibility, and has a high oxygen and aroma barrier function.

Although other vinyl polymers are prepared by polymerization of their corresponding monomers, PVA will partially or completely hydrolyze polyvinyl acetate to remove acetate groups. In order to ensure lubricity and adhesion to protect the fibers and aid processing, sizing is a processing mechanism applied to rovings and yarns.

The organic sizing agent composed of PVA and additives (such as plasticizers, lubricants, etc.) is designed to facilitate removal by thermal cleaning. The key raw material to produce PVA is vinyl acetate monomer. The monomer is produced by the polymerization of vinyl acetate. Then it undergoes partial hydrolysis, which consists of partial substitution of the ester group in the vinyl acetate in the presence of an aqueous sodium hydroxide solution by the hydroxyl group. After the gradual addition of the aqueous saponifier, the PVA precipitated, washed and dried.

 

(2) Use and performance of PVA adhesive

The simplest form is PVA or polyvinyl acetate, which is a glue used to stick paper sheets together. Climb up and be stronger, it becomes an excellent wood glue for DIY enthusiasts and carpenters.

PVA can be added to the cement mortar mixture to make the mixture

a) Slightly improved waterproof performance

b) Advanced adhesion to the applied surface

Applying a layer of PVA coating on the surface before applying cement mortar can even further improve this adhesion.

PVA can be used to seal wood to improve its waterproof performance, although if the wood surface is susceptible to abrasion or transportation, PVA (as an emulsifier) will eventually fail. Similarly, we do not recommend using PVA as a sealant on walls that will be overpainted with latex paint. PVA can also be used to allow tiles to stick to wood (bathroom panels, etc.). At least three layers of undiluted PVA must be applied, and each layer must be thoroughly dried before applying the next layer.

To be used in sand and cement, a mixture of 2 parts PVA and 1 part water is usually required. Pour the PVA into the water and mix as usual. PVA dries to a colorless finish and will not react with any other surface treatments or finishes.

Before applying the mortar, apply a layer of PVA on the surface. It can be used undiluted to achieve maximum sealing and/or adhesion, or diluted as described above. When the PVA is slightly sticky, it is best to use mortar or plaster. This gives it the best adhesion, and since it has not yet dried and is completely waterproof, it will still give the surface a natural porosity to help dry the mixture used. If the PVA is dry, the surface will not be able to "absorb" any moisture in the mixture and will require a longer drying time.

 

(3) Precautions for PVA and absorbent surface

PVA is used to apply a very absorbent surface before finishing the topcoat. If it is applied directly, the PVA will dry quickly and cannot be processed. For example, when plastering the existing artex-painted ceiling, the moisture in the plaster will be quickly absorbed, so that the plaster will harden within a few minutes and a smooth surface effect cannot be obtained. Sealing the surface with PVA will slow down the absorption of this moisture and allow the plaster to remain usable for a long time.

PVA adhesive can be simply applied to any surface, but since it is water-based and needs to be absorbed, it will not stick two non-absorbent surfaces together.

One thing to note is that if the surface to be treated is an external surface, it may be washed by rain frequently, weakening the PVA function.

 

 

 


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