Pure non-modified PDMS, 1,000–5,000 cP, hydrophobic silica nucleator; lowest-cost silicone defoamer.

MeFoam-S is the universal alkyl-silicone defoamer compound built on a non-modified polydimethylsiloxane (PDMS) backbone — no polyether modification, no specialty side-chain chemistry. The compound is a blend of medium-viscosity PDMS fluid (typically 350–1,000 cP virgin viscosity) at 80–85%, hydrophobic silica nucleator at 5–8% (treated with HMDS or DDS to render the silica surface hydrophobic), and a small amount of dispersing aid at 0.5–2%. The final compound viscosity at 25°C is 1,000–5,000 cP depending on silica loading — the silica creates a structured suspension that provides both nucleation activity and storage stability against creaming.

Compared to polyether-modified MeFoam-PE counterparts, MeFoam-S has two operational characteristics that determine the application fit: (1) lower cost per kg active — typically 35–45% cheaper than equivalent polyether-modified grades thanks to the simpler chemistry; (2) shorter shelf-life persistence in waterborne formulations — pure PDMS phase-separates from waterborne paint over 4–8 weeks vs the 12+ months of polyether-modified counterparts. The combination makes MeFoam-S the right choice for industrial applications where the formulation is consumed within 1–8 weeks of manufacture (industrial coil coating, factory-applied paint, fast-turnover adhesive lines) and where the cost saving justifies the shorter shelf-life window.

Non-modified PDMS provides strong surface-tension differential; spreads aggressively but hydrophobic in waterborne.

MeFoam-S operates by the same fundamental spreading-rupture mechanism as polyether-modified defoamers, but with a more aggressive surface-tension differential (PDMS surface tension 20–22 mN/m vs polyether-PDMS at 22–25 mN/m). The non-modified PDMS spreads more aggressively across foam bubble films, displacing surfactant more effectively, and giving fast initial defoaming kinetics (10–30 seconds in standard 0.5% aqueous SDS test). The drawback is hydrophobic incompatibility with waterborne formulations — without polyether modification, the PDMS phase-separates from the aqueous bulk over time, requiring agitation to redisperse and limiting shelf-life persistence.

• Loading 0.05–0.20% — solvent-borne coatings (alkyd, polyurethane, epoxy)
• Loading 0.10–0.30% — industrial waterborne coatings (factory-applied, ≤8 wk shelf life)
• Loading 0.10–0.50% — adhesive emulsions and binder formulations (fast-turnover)
• Loading 0.05–0.30% — oil-water separation, hydraulic fluid de-aeration

In solvent-borne coatings (alkyd, polyurethane, epoxy systems) MeFoam-S is the standard choice — the solvent matrix already provides the carrier compatibility that polyether modification provides in waterborne, eliminating the rationale for the more expensive polyether-modified grades. In waterborne formulations, MeFoam-S provides cost-effective foam control for industrial-channel coatings where the manufacturing-to-application timeline is short. Avoid for retail-channel waterborne paint with 12+ month shelf life — the phase-separation behaviour will produce surface defects on application after 4–6 months of storage; specify MeFoam-PE Low + High dual-grade pairing for that segment.

Solvent-borne coatings (largest), industrial waterborne, adhesive emulsions, oil-water separation, hydraulic.

Solvent-borne coatings are the largest single application — alkyd industrial enamels, polyurethane wood finishes, two-pack epoxy industrial floor coatings, and chlorinated rubber marine paints. MeFoam-S at 0.05–0.20% on total formulation provides foam knockdown during high-shear let-down mixing without the cost premium of polyether-modified grades. In solvent-borne systems, the carrier solvent provides the dispersion medium that polyether modification would provide in waterborne — the simpler MeFoam-S chemistry is fully adequate.

Industrial waterborne coatings with short manufacturing-to-application timeline (factory-applied coil coating, OEM industrial primer dosed within 4 weeks) use MeFoam-S at 0.10–0.30% as the cost-rational choice over polyether-modified grades. Adhesive emulsions and waterborne binder formulations for fast-turnover production (PVAc wood adhesive, EVA emulsion for tile adhesive, vinyl-acrylic for coated paper) use MeFoam-S at 0.10–0.50% during emulsion polymerisation and let-down. Oil-water separation systems in petrochemical and food-processing facilities use MeFoam-S at 50–500 ppm to suppress foam in clarification stages. Hydraulic fluid and lubricant de-aeration uses MeFoam-S at 0.005–0.050% (typically pre-formulated by the lubricant blender) to suppress entrained air that would impair pump performance.

CoA per shipment; 25 kg HDPE pail; 12-month sealed shelf life; non-flammable; compatibility testing required.

SEMITECH issues a CoA on every batch with: viscosity at 25°C (Brookfield, target 1,000–5,000 cP), active silicone content (FT-IR or solvent extraction, target ≥92%), hydrophobic silica content (ash analysis, target 5–8%), water content (Karl Fischer, target ≤0.5%), and visual appearance. Standard packing 25 kg HDPE pails for active compound; 200 kg HDPE drums for bulk industrial coatings plants; 50% emulsion form available in 25 kg HDPE jerrycans on request. MOQ 25 kg per grade. Lead time 1–2 weeks ex-Zhejiang to Asia ports, 4–6 weeks to Europe and North America after sea freight.

Storage: stable under ambient conditions; non-flammable; no nitrogen blanket required. Recommended: store sealed below 30°C; the high silica content can settle over time — re-homogenise drums before dosing if stored beyond 6 months. Shelf life 12 months sealed; 6 months for emulsion form. Compatibility testing is mandatory — pure PDMS defoamers are more prone to surface-defect issues (fish-eyes, crawling, gloss reduction) on certain substrates than polyether-modified counterparts. Run a small-scale draw-down test on the actual customer substrate before scaling. REACH and regulatory: REACH-registered for industrial use; FDA 21 CFR 175.300 listed for indirect food-contact in printing-ink and packaging-coating applications; not for direct food-contact (specify MeFoam-FG for food-contact). SDS in EU/GHS format issued with every shipment.

MeFoam-S is the cost-rational universal silicone defoamer — non-modified PDMS chemistry, ~40% cheaper than polyether-modified MeFoam-PE, optimised for solvent-borne coatings and short-shelf-life industrial waterborne applications. Avoid retail-channel waterborne paint (phase-separation in 4–8 wk) — specify MeFoam-PE Low+High pairing for that segment.

SEMITECH stocked grade; CoA per batch.