SG-01 Emulsão ecológica de VAE de fixação de areia para estabilização do solo

A vinyl acetate-ethylene (VAE) copolymer dispersion with a glass transition temperature (T_g) of approximately 7 °C (DSC, 10 K/min heating rate), SG-01 is formulated as a surfactant-stabilised aqueous emulsion that functions as a cold-applied soil binder for wind-erosion suppression, dust palliation, and surface crust reinforcement on cohesionless substrates. The polymer phase, comprising internally plasticised ethylene segments, requires no external coalescing solvents; its minimum film-forming temperature (MFFT) remains below 2 °C, permitting application at near-freezing ambient conditions without compromising particle coalescence. Upon water loss, the dispersion transitions into a continuous film that mechanically bridges discrete sand grains, fines, and aggregates while retaining a microporous architecture that permits vapour transmission and limits pore-pressure build-up during wetting cycles. Biocide preservation complies with ISO 11930:2019 challenge-test criteria, and the product is free of intentionally added per- and polyfluoroalkyl substances (PFAS), alkylphenol ethoxylates (APEOs), and chlorinated paraffins. Free formaldehyde content, determined by the acetylacetone method (EN 717-3:1996), is consistently below 5 mg/kg, which meets the most stringent European E1 classification benchmarks for indoor air quality even though the intended use is outdoor geotechnical stabilisation. The anionically stabilised latex carries a pH of 4.5–6.0 at 25 °C and a Brookfield viscosity (LVF, spindle #3, 60 rpm) in the range 1500–4000 mPa·s, enabling pumping through diaphragm or progressive-cavity equipment without the shear-induced coagulation that plagues low-shear-stable poly(vinyl acetate) homopolymer dispersions.

What differentiates SG-01 from conventional PVA homopolymer soil binders?

Poly(vinyl acetate) homopolymer emulsions—often mislabelled simply as “PVA glues” in field instructions—rely on a hydrolysed or partially hydrolysed poly(vinyl alcohol) protective colloid that confers initial shear stability but introduces a permanent hydrophilic pathway. After repeated wet-dry cycling, homopolymer-bound crusts absorb water, swell, and lose structural competence because the poly(vinyl alcohol) phase re-dissolves or re-emulsifies at the inter-particle necks. SG-01 substitutes the water-sensitive protective colloid with a purely anionic surfactant package and incorporates ethylene as a randomly distributed comonomer. The ethylene units depress the T_g below that of pure PVAc, eliminate the need for fugitive plasticisers, and introduce backbone hydrophobicity. Consequently, a cured SG-01 film exhibits a water absorption at equilibrium (23 °C, 95 % RH) that is typically 40–60 % lower than that of a comparable PVAc homopolymer film when both are measured on free films according to ISO 62:2008 gravimetric procedures. Published data for specific sand-polymer composite water uptake under full immersion remains limited, but the free-film trend correlates with significantly higher retained penetrometer resistance after 48 h of simulated rainfall (ISO 22476-9 cone penetration test analogue). A second critical difference concerns low-temperature film integrity and film cracking. PVAc homopolymer films stored below 5 °C during overnight curing often exhibit micro-crazing because the rigid homopolymer cannot accommodate the tensile stress generated during capillary-pressure-driven film compaction. SG-01’s ethylene segments impart viscoelastic compliance; specimens cured in a climate chamber at +2 °C and 50 % RH develop continuous crusts without developing the star-shaped fissures observed in homopolymer controls. This property expands the operational season for dune fixation projects in arid high-altitude environments where night-time temperatures persistently approach freezing.

Comparative performance profile: VAE emulsion SG-01 versus other water-based soil binders

Property (test basis)	SG-01 (VAE)	PVAc homopolymer	Styrene-acrylate copolymer	Polyurethane dispersion
Wet-crust strength retention after 24 h immersion (proxy penetrometer index)	Medium–high; gradual softening without slaking	Low; rapid slaking observed	Medium; surface softening with substrate intact	High; highly hydrophobic crust
Film re-emulsification risk (ISO 2812-3 water spot test)	Negligible; no tackiness after 4 h	High; tacky surface recovery	None; irreversible film	None
Minimum film-forming temperature (MFFT, ASTM D2354)	<2 °C	Typically 10–15 °C unless plasticised	<5 °C (self-film-forming grades)	>0 °C (substrate-dependent)
Need for external coalescent (VOC contribution)	None	Often required below 10 °C	Common; 2–5 % on formulation	Common; high-boiling NMP or glycol ethers
Biodegradability of cured film (OECD 301F, manometric respirometry)	Not inherently biodegradable; inert solid	Not inherently biodegradable	Not biodegradable	Not biodegradable; some grades contain ester linkages
Substrate pH tolerance range	5.0–9.5	5.0–8.0 (alkaline hydrolysis risk)	4.0–10.0	3.0–12.0

Application via hydroseeding cannons, tractor-mounted spray booms, or backpack sprayers proceeds after dilution with clean water at volumetric ratios between 1:4 and 1:12, the exact ratio being dictated by target penetration depth and substrate fines content. Sands with a uniformity coefficient (C_U) below 2.0, classified as poorly graded (SP per ASTM D2487), require the higher-concentration end of the range to generate a crust thickness of at least 8–15 mm. The diluted emulsion must be maintained under intermittent recirculation; a minimum loop velocity of 0.5 m/s in the supply line prevents settlement of minor coagulum that may form through mechanical shear at throttling valves. Coarse-nozzle fan patterns (80–110° spray angle) operated at 1.5–3.0 bar fluid pressure are preferred because air-atomisation nozzles can over-dry the spray droplets mid-flight, yielding premature skinning that hampers inter-layer adhesion when multiple passes are required. Coverage rates, expressed as neat emulsion per square metre of substrate, are typically specified between 0.15 L/m² (dust suppression on gravelled access roads) and 0.6 L/m² (dune crest stabilisation in high-erosion zones). Because the emulsion is non-flammable and water-based, equipment cleaning uses only water, eliminating the flammable solvent handling protocols required for solvent-borne polyurethane binders.

Rheological demands in high-shear spraying equipment

Pump selection for SG-01 is dictated by its pronounced shear-thinning character. At 25 °C, the apparent viscosity drops from approximately 3500 mPa·s at 1 s⁻¹ to below 300 mPa·s at 1000 s⁻¹, as measured by cone-and-plate geometry (ISO 3219). This pseudoplasticity is beneficial during pressurised transfer, but it imposes a lower-bound shear limit during recirculation: if the bulk fluid remains below approximately 10 s⁻¹ for periods exceeding 30 minutes, weak flocculation of the latex particles can elevate the pre-spray viscosity and cause pressure fluctuations at the nozzle manifold. In hydroseeding rigs where the emulsion is combined with a fibre mulch and agitated in a tank, low-speed paddle mixers (20–40 rpm) should operate on an intermittent timer circuit—5 minutes on, 15 minutes off—to balance suspension stability against excessive air entrainment, which can generate micro-voids in the applied crust.

When moisture ingress threatens cured sand crust integrity

WAter exposure after curing does not immediately destroy a VAE-bonded crust, yet prolonged saturation reduces the modulus of the polymeric bridges and permits microscale slippage of the sand grains. The resulting loss in surface bearing capacity is a function of the polymer’s wet glass-transition behaviour and the tortuosity of the pore network. Dynamic mechanical analysis (DMA) on isolated SG-01 films (tension mode, 1 Hz, 3 K/min ramp) shows that the storage modulus (E′) drops approximately 60 % upon immersion in deionised water at 23 °C for 72 h, stabilising thereafter. This modulus softening is reversible upon re-drying, provided the crust has not been subjected to mechanical traffic while saturated. For high-moisture environments—such as coastal dune faces exposed to sea spray or irrigation overspray on roadside embankments—SG-01 can be co-applied with a 0.5–1.5 wt % addition of a water-dispersible polyisocyanate (WDP) crosslinker. The isocyanate groups react with residual hydroxyl species on the sand surface and with the small fraction of hydroxyl-functional comonomer intentionally polymerised into the VAE backbone. This creates a lightly crosslinked interpenetrating network that limits equilibrium swell to 8–12 % (gravimetric, 24 h immersion) versus 25–35 % for the unmodified VAE matrix. The pot life of the catalysed emulsion is approximately 4–6 h at 25 °C; beyond this window, viscosity climb accelerates due to progressive crosslinking in the liquid phase, rendering the mixture unsprayable. Personnel must flush all equipment with water before the end of the pot life to avoid irreversible gel formation in pump cavities. Evaluations against the German Federal Highway Research Institute (BASt) specification TL Geok E-StB 05 for earthworks stabilisation have been conducted in a third-party geotechnical laboratory on a silty sand (SM, AASHTO A-2-4) dosed at 3 wt % of neat emulsion per dry soil weight. Unconfined compressive strength (UCS) after 7 days of curing at 20 °C and 65 % RH increased by a factor of 4.8 relative to the untreated control, while the California Bearing Ratio (CBR, ASTM D1883) at 95 % modified Proctor density rose from 12 % to 48 %. These results were obtained without the alkali-activation step required by some slag-based pozzolanic stabilisers, simplifying logistical demands on remote sites where controlled curing water supply is unreliable. It must be emphasised that the quoted UCS and CBR figures are specific to the tested soil gradation and cure regime; variation in mineralogy, organic content above 1.5 %, or the presence of soluble salts can shift these values. A site-specific pre-construction jar test and a small-scale plot trial are therefore essential. Transport and storage of SG-01 require protection from freezing (product freezes near 0 °C and, although some freeze-thaw recovery is possible with VAE dispersions, repeated cycles lead to irreversible grit formation) and from sustained temperatures exceeding 40 °C. Containers must be sealed when not in use to prevent skin-over from surface evaporation; any surface skin should be removed and not re-dispersed, as it will not fully coalesce during application. Shelf life in unopened original containers stored between +5 °C and +30 °C is 12 months from the production date. The emulsion carries a water-endangering class (WGK) 1 (slightly hazardous to water) classification per German Federal Water Act (WHG) and does not require labelling as a hazardous substance under the Globally Harmonized System (GHS) for transport, which simplifies cross-border logistics for international erosion-control projects.