PVA(Polyvinyl Alcohol)

PVA advocates promote its EOL (end-of-life) performance, where its ability to be broken down by bacteria and its low toxicity provide a more sustainable alternative to other materials such as LDPE.

It should be noted that dissolving it in water does not mean the PVA has disappeared. Much like dissolving salt in water, you cannot see it but the salt is certainly still there. Studies have shown that solutions containing up to 5% PVA are non-toxic to fish.

While bacteria and fungi can biodegrade the material, this occurs slowly – One study indicates degradation of just 32% during wastewater treatment processing, with the remainder either released into the environment, landfilled, incinerated or used in agriculture together with other waste treatment endproducts. The effects of this remaining 68% are poorly understood as of writing, but biodegradation will continue to occur.

As a synthetic polymer manufactured from acetic acid and ethylene, PVA is usually derived from fossil fuels, though it is possible (although uncommon) to source ethylene made from renewable, bio-based sources.

Polyvinyl alcohol Resin is also called Poly Vinyl Alcohol Resin, PVOH, PVA. PVA Resin comes in various classifications, each serving specific purposes and industries. It is a soluble resin widely utilized in textile pulp, adhesives, construction, and other sectors. Moreover, PVA can be modified to create films, such as degradable mulch film and fresh-keeping film, making it eco-friendly due to its natural degradation.

Two essential indicators of PVA are the degree of polymerization and the degree of alcoholysis, with classifications like 17-99, 20-99, 23-99, and more. For instance, 17-99 signifies a polymerization degree of 1700 and an alcoholysis degree of 99%. Depending on the characteristics, PVA can be categorized into flocculent and flake (granular) types.

Higher polymerization degrees1 result in greater solution viscosity, while lower alcoholysis degrees2 enhance low-temperature solubility. PVA variants with lower polymerization and higher alcoholysis are commonly used in textile pulp, while others are employed as protective colloids for water-based adhesives or construction adhesives, like the well-known 107 and 801 construction glue.

Polyvinyl alcohol 17-88, also known as PVA 1788, exhibits interesting properties. Its aqueous solution viscosity gradually increases over time at room temperature, except when the concentration reaches 8%, at which point the viscosity remains stable. The unique characteristic of PVA is its excellent film-forming ability, making it highly resistant to most gases except water vapor and ammonia. Moreover, PVA possesses good light resistance, rendering it unaffected by light exposure. It can burn in an open fire, emitting a distinct smell. The aqueous solution of PVA may sometimes become toxic during storage, although it is non-irritating to human skin.

Polyvinyl alcohol 17-99, also referred to as sizing resin or PVA 1799, presents as a white or yellowish powder or floc solid. It has a glass transition temperature of 85°C and a saponification value ranging from 3 to 12 mgKOH/g. Soluble in hot water at 90-95°C, it is almost insoluble in cold water. Aqueous solutions with concentrations exceeding 10% gel and freeze at room temperature but regain fluidity at higher temperatures. To stabilize the viscosity, additives like sodium thiocyanate, calcium thiocyanate, phenol, and butanol can be incorporated into the solution. PVA17-99 exhibits higher sensitivity to borax-induced gelation compared to PVA17-88. A 0.1% borax concentration will cause a 5% PVA17-99 aqueous solution to gel, whereas a 1% borax concentration is required for the same effect in a PVA 17-88 solution. For PVA aqueous solutions with equal concentrations and alcoholysis degrees, borax is more prone to induce gelation than boric acid.

Polyvinyl alcohol 24-88, or PVA 2488, is characterized by its small particle polymer that readily disperses in cold water. This quality enables quick dispersion in water, leading to high-viscosity aqueous solutions with excellent stability and decorative effects. Consequently, it improves the characteristics of cement mortar, and PVA 2488 also exhibits capillary and adsorption functions.

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