SELVOL Álcool Polivinílico 103

SELVOL Polyvinyl Alcohol 103 is a low-viscosity, fully hydrolysed polyvinyl alcohol grade supplied by Sekisui Specialty Chemicals as a white to off-white granular solid. Manufacturer specification data place the degree of hydrolysis between 98.0 mol% and 98.8 mol%, corresponding to a residual vinyl acetate content below approximately 2 mol%. The viscosity of a 4 wt% aqueous solution at 20 °C is specified as 3.5–4.5 mPa·s. This low viscosity distinguishes the grade from medium- and high-viscosity fully hydrolysed types in the same SELVOL range. The low molecular weight reduces chain entanglement and solution viscosity but also lowers tensile strength and film toughness relative to grades such as SELVOL 107. The product is typically specified where high-solids, low-viscosity processing is required: paper surface sizing, textile warp sizing, emulsion polymerisation as a protective colloid, aqueous adhesive modification, ceramic green-tape binder systems, and water-soluble release films for unsaturated polyester moulding.

Because the grade is fully hydrolysed, cold-water solubility is limited. Aqueous dissolution normally requires a two-stage sequence. The granules are first dispersed in cold demineralised water at 15–25 °C under mechanical agitation, then heated to 90–95 °C and held for 30–60 min. Direct addition to hot water causes rapid surface hydration and gel-block formation, which reduces yield and increases filter pressure in downstream coating lines. In storage areas above 60% relative humidity, the product must be stored sealed or pre-dried before use because equilibrium moisture content can exceed the specified maximum volatile content of 5.0 wt% and alter loss-in-weight feeder performance.

The aqueous solution viscosity of SELVOL 103 is strongly temperature-dependent, and this affects in-line viscometer calibration on continuous coating systems. Process temperature variation of ±5 °C in the service tank can shift coat weight when metering is based on volumetric flow alone. Coating lines therefore use gravimetric or mass-flow feed systems rather than fixed-speed metering pumps when tight coat-weight tolerance is required. The low viscosity also reduces the maximum foam stability in high-shear mixing, but misting and air entrainment become more visible at machine speeds above 800 m/min in low-solids formulations.

What Distinguishes Grade 103 from Partially Hydrolysed SELVOL 205 and Higher-Viscosity SELVOL 107?

The primary molecular difference is residual acetate concentration. SELVOL 103 and SELVOL 107 are both fully hydrolysed, but grade 107 is produced with a higher molecular weight and a specified 4 wt% aqueous viscosity of 5.5–7.5 mPa·s. The higher chain length of SELVOL 107 increases hydrogen-bonded crystallite formation after drying, improving water resistance and tensile strength, but reduces the maximum solids content that can be pumped and coated without excessive viscosity. SELVOL 103 therefore operates in paper coating and sizing systems at higher solids than SELVOL 107 while accepting lower film toughness.

Partially hydrolysed grades such as SELVOL 205 and SELVOL 502 have hydrolysis values of 87.0–89.0 mol%. The residual acetate groups disrupt crystallite packing, improve cold-water solubility, and increase surface activity at the vinyl acetate monomer–water interface. SELVOL 205 has a 4 wt% aqueous viscosity of 5.2–6.2 mPa·s; SELVOL 502 has a 4 wt% aqueous viscosity of 3.0–3.7 mPa·s. The partial acetate content makes these grades easier to dissolve and more effective stabilisers for fine latex particles, but dried films are more sensitive to water and organic solvents than films from SELVOL 103.

In vinyl acetate homopolymer and ethylene-vinyl acetate copolymer emulsion polymerisation, SELVOL 103 is evaluated as a primary protective colloid in jacketed stirred-tank reactors fitted with pitched-blade or anchor agitators. The low aqueous viscosity allows preparation of an 8–10 wt% colloid premix in demineralised water at 20–25 °C without exceeding agitator torque limits on production-scale equipment. Fully hydrolysed PVOH with 98.0–98.8 mol% vinyl alcohol units has been reported to generate broader latex particle-size distributions and higher freeze-thaw sensitivity than partially hydrolysed protective colloids because the fully hydrolysed polymer grafts less readily to the polyvinyl acetate particle surface. This is a critical process boundary. Vinyl acetate emulsion plants demanding fine nucleation and low coagulum frequently select partially hydrolysed SELVOL 502 or SELVOL 205 and accept the reduction in dried-adhesive water resistance. When SELVOL 103 is used for water-resistant adhesive or sizing applications, addition levels are typically kept below 2.5 wt% on total monomer, but published data for this specific configuration are limited.

On high-speed metered size presses running above 800 m/min, low-viscosity fully hydrolysed PVOH is often selected to maintain stable film transfer and to avoid misting at solids up to 10 wt%. The low molecular weight promotes penetration into the sheet rather than surface film build. Cobb water absorption values measured according to ISO 535 are typically higher for SELVOL 103-sized papers than for papers sized with SELVOL 107 at equal coat weight, but the lower viscosity permits a higher size-solution solids concentration, which partially compensates for the molecular-weight difference. Surface sizing formulations containing SELVOL 103 and an insolubiliser such as glyoxal or ammonium zirconium carbonate must maintain a tank pH above 6.0 to prevent premature gelation. Borax and boric acid additions must be made as diluted solutions with inline static mixing because diol complexation with the 1,3-diol structure of PVOH forms stiff gels within seconds at concentrations above 1 wt%.

Film Drying, Plasticiser Migration, and Thermal Processing Limits

Cast films produced from grade 103 are typically tested for tensile properties according to ASTM D638-14. Because the grade has low molecular weight, tensile strength at break is expected in the lower range of fully hydrolysed PVOH films, while elongation is similarly limited unless plasticiser is present. The high hydrolysis level raises glass transition temperature to approximately 75–80 °C for unplasticised film, which produces brittleness at room temperature. Addition of 10–20 wt% glycerol or sorbitol relative to dry PVOH reduces tensile strength and increases elongation, but also increases oxygen transmission rate. Published permeability data for plasticised low-viscosity fully hydrolysed PVOH are limited. For high-barrier packaging films, medium- or high-viscosity grades are generally preferred unless high coating efficiency at low viscosity is the controlling parameter.

Melt processing of SELVOL 103 without plasticiser is constrained by thermal degradation. Fully hydrolysed PVOH begins to decompose above 200 °C, releasing acetic acid and discolouring the melt. Processing at melt temperatures above 220 °C on twin-screw extruders with L/D ratios between 30:1 and 40:1 requires pre-compounded plasticiser, controlled residence time, and venting to remove water and volatiles. Failure to pre-dry the granules at 80–100 °C to below 0.5 wt% moisture can cause bubble formation and hydrolytic chain scission during extrusion. These boundaries restrict direct injection moulding of SELVOL 103 and favour solution-based application routes.

In textile warp sizing, the low viscosity of SELVOL 103 allows size-box solids up to 8–12 wt% in high-speed weaving preparation. The fully hydrolysed character provides a hard, crystalline size film after drying, improving resistance to organic solvents and oils but reducing cold-water desizing efficiency compared with partially hydrolysed grades. Desizing is therefore performed with hot water above 70 °C, often with oxidative or amylase-compatible scouring chemistry depending on fibre type. For cotton and cotton-blend warps, the low molecular weight limits abrasion resistance under high loom speeds, so the grade is more commonly blended with medium-viscosity PVOH or starch to balance film flexibility and weaving performance.

In aqueous ceramic green-tape formulations, SELVOL 103 functions as a temporary organic binder at 1–4 wt% based on ceramic powder. The low solution viscosity permits high solids loading and acceptable tape-casting flow. After lamination and burnout, the fully hydrolysed grade leaves low ash residue, but burnout cycles must include an air-oxidative stage above 450 °C to remove residual carbon. The ash specification of 0.5 wt% as Na₂O is relevant for dielectric applications; lower-ash specialty grades are available when sodium content influences electrical loss.

For indirect food-contact applications, compliance must be confirmed against FDA 21 CFR 176.170 and 21 CFR 175.300 where the coating or adhesive is not intended to migrate. European users must verify compliance under Regulation (EU) No 10/2011 for plastic materials in contact with food and under Regulation (EC) No 1907/2006 (REACH) for residual monomer and methanol content. Residual methanol in the product is specified at no more than 2.0 wt%, and the grade is supplied with a certificate of analysis covering viscosity, hydrolysis, pH, ash, volatiles, and methanol.