Emulsão VAE de alta viscosidade GW-706

GW‑706 High‑Viscosity VAE Emulsion is an internally plasticized, surfactant‑stabilized vinyl acetate–ethylene (VAE) copolymer dispersion supplied at 63 ± 1 % solids (ISO 3251) with a Brookfield RVT viscosity of 12 000–18 000 mPa·s at 25 °C (spindle 6, 20 rpm, ASTM D2196). The emulsion is free of external plasticizers and alkylphenol ethoxylates; film formation occurs via ethylene‑induced internal plasticization at a minimum film‑forming temperature of 0 °C (MFFT, ISO 2115) and a glass transition temperature of approximately −5 °C (DSC, ISO 11357‑2). The pH resides between 4.5 and 5.5 (ISO 976), and the average particle diameter spans 0.5–0.8 µm (laser diffraction, ISO 13320). Designed as a high‑tack, high‑rheology binder, GW‑706 is deployed in D3/D4 wood flooring adhesives, polymer‑modified cementitious waterproofing slurries, and single‑coat parquet adhesives where sag resistance and filler‑holding capacity are mandatory. In these domains, the product differs from low‑viscosity VAE grades such as GW‑406 (solids 55 %, viscosity 1500–3000 mPa·s) by enabling filler loading up to 400 phr of calcium carbonate without sedimentation and by delivering wet film thicknesses exceeding 800 µm in a single trowel pass without slump. Compared with typical styrene‑acrylic emulsions, GW‑706 provides superior adhesion to unprepared beech and oak substrates without chlorinated‑solvent primers, a consequence of the high vinyl acetate content that forms multiple hydrogen bonds with cellulose hydroxyl groups. The emulsion carries no hazard classification under CLP Regulation (EC) No 1272/2008 and complies with the low‑VOC criteria of the German AgBB scheme (< 0.3 % residual monomer).

What distinguishes high‑viscosity VAE from conventional emulsion polymers?

The defining rheological feature of GW‑706 is its pronounced pseudoplasticity: the low‑shear viscosity of 12 000–18 000 mPa·s drops to 3 000–5 000 mPa·s under the shear rates generated by a notched trowel (10–50 s⁻¹), as measured on a controlled‑stress rheometer (cone‑plate, 40 mm, 1 °). This shear‑thinning behaviour allows a high static yield stress that arrests filler settling, yet permits easy spreading without the addition of associative thickeners. Acrylic emulsions of equivalent solids (63 %) typically exhibit near‑Newtonian flow and require post‑thickening with polyurethane‑based HEUR rheology modifiers, which can compromise wet adhesion and retard film formation in high‑humidity conditions (RH > 80 %). Styrene‑butadiene latexes can achieve similar shear‑thinning but often require higher coalescent dosages and contribute to higher VOC profiles. GW‑706 also supports exceptionally high filler loads: trials on a planetary dissolver (Netzsch MasterMix, 7.5 kW) have demonstrated that 400 phr of fine calcite (D₅₀ 2 µm) can be incorporated without exceeding a Hegman grind of 4 NS, whereas analogous low‑viscosity VAE emulsions exhibit phase separation at 250 phr. The following table summarizes the compositional and rheological contrast.

The absence of external coalescents in GW‑706 reduces the occupational exposure risk during application in confined spaces; total VOC content remains below 0.5 % (ISO 11890‑2). Because the ethylene comonomer provides permanent flexibility, the film does not embrittle over time due to plasticizer migration, a documented failure mode in PVAc homopolymer adhesives after 5‑year indoor ageing at 40 °C (EN 14292).

Determining the dose‑response of creep resistance in parquet adhesives

When formulated as a filled wood adhesive, GW‑706 meets the requirements of durability classes D3 and D4 of EN 204/205 with the addition of an acidic metal salt catalyst. In a typical production‑scale twin‑planetary mixer (Ross PDM‑2, 20 L), a reference formulation comprising 100 pbw emulsion, 200 pbw calcite filler, 0.5 pbw defoamer (polyether siloxane), and 3 pbw aluminium chloride solution (50 % in water) yields a stable paste with a pot life exceeding 4 hours at 23 °C. The high initial viscosity prevents sag on vertical oak blocks, permitting one‑step installation without temporary pinning. After 7 days’ conditioning at 23 °C/50 % RH followed by 4 days’ immersion in cold water (20 ± 2 °C), the tensile shear strength measured on beech to EN 14256 reaches 2.8 MPa with cohesive failure in the wood substrate. In contrast, the same formulation prepared with a low‑viscosity VAE (GW‑406) fails to exceed 1.2 MPa under identical preparation conditions due to filler sedimentation and internal de‑wetting at the tile–adhesive interface.

The creep resistance under sustained load (EN 14257, 7.2 kg dead load, 23 °C, 7 days) remains below the 0.5 mm limit when the aluminium chloride catalyst is used; without catalyst, creep exceeds 2.0 mm and the formulation is acceptable only for D1/D2 service. It is critical to avoid accidental contamination with amines or ammonia vapour during storage and compounding, because amine‑catalysed transesterification of the vinyl acetate units leads to premature cross‑linking and spot‑gelation within the closed container—a phenomenon observed on a 500 kg IBC stirred batch when a residual monoethanolamine cleaning agent remained in the filling line.

When the emulsion meets Portland cement: compatibility envelope and set‑time window

GW‑706 can be integrated into Portland cement‑based mortars to produce flexible crack‑bridging slurries and repair systems. The high‑viscosity character reduces mixing‑water demand in a two‑component blend; at a polymer‑cement ratio (p/c) of 0.15, the water‑demand reduction compared with a standard VAE (GW‑406) is 12 %, allowing a lower water/cement ratio and compensating for the strength‑retarding effect of the latex. A mortar prepared with CEM I 42.5 R (EN 197‑1), silica sand (0.1–0.5 mm), emulsion, and a tributyl phosphate defoamer (0.3 % on emulsion) exhibits the following properties as a function of dosage. The data were obtained on a Collomix XM‑2 forced‑action mixer with 30 L batch size under laboratory conditions.

The emulsion tolerates the high‑pH environment of hydrating cement; however, the early release of calcium hydroxide can destabilise the colloidal dispersion if mixing is interrupted and the paste is left unstirred for more than 15 minutes. A continuous feed of dry mortar powder into the liquid emulsion under high‑shear disperser (rotor‑stator gap 0.5 mm) avoids flocculation. The maximum recommended p/c is 0.20; beyond this level, the initial set is retarded by more than 4 hours and shrinkage cracking may occur because the polymer film formation lags behind cement hydration. Additionally, mixing water must contain less than 2000 ppm calcium ions (as CaCO₃) to prevent instantaneous electrostatic coagulation—a limit routinely exceeded when using hard well‑water in certain Mediterranean production sites.

In high‑build, knife‑applied waterproofing membranes formulated with GW‑706 and 0.1–0.6 mm quartz sand, the crack‑bridging ability at 23 °C exceeds 0.8 mm (EN 14891, method with static crack) when the coating thickness reaches 2 mm. After 1 day’s dry curing followed by 7 days’ immersion in water, the adhesion to concrete substrate (EN 1542) remains at 1.2 N/mm², with failure occurring cohesively within the membrane. Such wet adhesion is not achievable with PVAc homopolymer emulsions, which undergo hydrolysis in alkaline cementitious environments and lose bond strength to less than 0.3 N/mm² after 48 hours’ water contact. This performance envelope, combined with film formation at 0 °C, allows the emulsion to be used in external waterproofing systems that must remain functional during spring and autumn temperature swings, provided the membrane is protected from direct UV radiation until top‑coated with a reflective layer conforming to EN 1504‑2.