SEMITECH® SA-25 — Medium-Particle Anti-Blocking & Slip Agent for Medium-to-Thick Films
SEMITECH SA-25 is a surface-treated synthetic amorphous silica engineered for anti-blocking and slip performance in medium-to-thick flexible packaging and industrial films. With a d50 of 4.0–5.0 µm and an intricate porous microstructure, SA-25 creates a robust micro-rough surface profile on film boundaries — delivering more pronounced physical layer separation than fine-particle grades and making it the preferred specification for heavy-gauge PE blown sacks, thick BOPP and CPP extrusion runs, agricultural films, and PVC plastisols.
The coarser particle geometry ensures deeper protrusion from the film surface relative to film thickness, translating to more effective contact-area reduction and COF control under the elevated winding tensions and block pressures typical of heavy-duty industrial packaging operations. SA-25 is the functional equivalent of Evonik SYLOID® FP246.
Technical Specifications
| Properties and Test Methods | Unit | Specification | Standardization |
|---|---|---|---|
| SiO₂ Content (dry basis) | % | ≥99 | — |
| Particle Size d50 (laser diffraction) | µm | 4.0–5.0 | — |
| pH Value (5% aqueous dispersion) | — | 6.0–8.0 | GB/T 1717 |
| Oil Absorption | g/100g | 20–50 | GB/T 5211.15 |
| Loss on Drying (2h @ 105°C) | % | ≤3.0 | — |
| Loss on Ignition (2h @ 1000°C) | % | ≤3.0 | — |
| Surface Treatment | — | Organo-functional | — |
| Equivalent Grade | — | Evonik SYLOID® FP246 | — |
Application Suggestions
Thick BOPP / CPP Extrusion Lines
SA-25 is the standard anti-blocking specification for BOPP films above 25 µm gauge and for cast polypropylene (CPP) and cast sheet configurations. At 0.15–0.35 wt% masterbatch loading, the 4.0–5.0 µm particles provide deeper surface protrusion geometry than fine-particle grades, eliminating blocking under the compression loads encountered in heavy-gauge film roll storage and pallet stacking during transport.
Heavy-Duty PE Blown Sacks (LDPE / LLDPE)
For agricultural bags, flexible intermediate bulk containers (FIBCs), and heavy industrial sacks, SA-25 is added at 0.10–0.30 wt% in the blown film compound. The coarser particle profile is proportionate to the thicker gauge of these structures and provides blocking resistance under the elevated winding tensions and outdoor storage conditions — including temperature fluctuation and moisture exposure — typical of agricultural packaging supply chains.
Agricultural Films
SA-25 provides durable blocking resistance in LDPE and LLDPE mulch film and greenhouse film rolls stored outdoors. The robust micro-rough topography created by the 4.0–5.0 µm particles maintains inter-layer separation under the sustained compression of full-season roll storage in agricultural environments.
Shrink Packaging Film (LDPE / LLDPE)
SA-25 reduces COF and blocking tendency in shrink film structures that must unwind and convey reliably through high-speed heat-tunnel packaging lines. The deeper surface protrusion prevents film-to-film fusion at the elevated temperatures encountered during temporary storage near heat-tunnel equipment.
PET Industrial-Grade Sheets and Optical Protection Films
In PET industrial sheets and optical protection films subject to stacking under compression, SA-25 provides inter-layer slip and blocking resistance without the adhesion promoter treatments that could compromise surface cleanliness requirements in optical applications.
PVC Plastisols and Rigid / Semi-Flexible Sheets
SA-25 is compatible in PVC plastisol formulations and calendered rigid and semi-flexible sheet applications requiring blocking resistance under elevated stacking pressures and at the elevated temperatures typical of PVC processing.
Technical Support & FAQ: SEMITECH SA-25
+Q1: When should SA-25 be chosen over SA-23?
SA-25 (d50 4.0–5.0 µm) is the correct specification when film gauge exceeds ~25 µm or when blocking pressure is elevated (heavy rolls, pallet stacking, outdoor agricultural storage). The coarser particle provides proportionally deeper protrusion in thicker structures. SA-23 (d50 3.0–4.0 µm) is the correct choice for thin-gauge films below 25 µm and clarity-critical applications where the coarser SA-25 particles would increase haze or produce visible surface defects.
+Q2: What masterbatch loading is recommended for heavy-duty PE sack applications?
For heavy-duty LDPE/LLDPE blown sacks (gauge 80–200 µm), SA-25 is compounded into a PE carrier masterbatch at 10–20 wt% active content, let-down into the film compound at ratios delivering approximately 0.15–0.30 wt% finished-film loading. Higher loadings (up to 0.5 wt%) may be required for applications subject to extreme compression or elevated storage temperatures.
+Q3: How does SA-25 compare to Evonik SYLOID FP246?
SA-25 is engineered to the same d50 range (4.0–5.0 µm) and equivalent purity (SiO₂ ≥99%) as SYLOID FP246. Performance in BOPP thick-gauge and heavy-duty PE anti-blocking applications is equivalent. SA-25 offers a 30–45% lower landed cost on FCL volumes direct from SEMITECH on FOB Shanghai terms.
+Q4: What are typical lead times and packaging?
Standard lead time is 7–14 days from order confirmation. SA-25 is packed in 25 kg PE-lined multi-wall kraft bags; 500 kg jumbo bags available for high-volume masterbatch operations. Free samples (200 g–1 kg) for trial compounding available on request. Contact info@semitechnm.com for quotation.
Packing & Storage Information
20′ FCL Container Approximately 18–20 MT of SA-25 in 25 kg PE-lined multi-wall kraft bags. Palletized or floor-loaded options available.
40′ HQ Container Approximately 20–22 MT in 25 kg bags or 500 kg jumbo bags.
Storage Conditions Store in a cool, dry warehouse away from moisture sources. SA-25 is mildly hygroscopic — opened bags should be resealed and consumed promptly. Recommended storage temperature: below 35°C. Shelf life: 24 months in original sealed packaging.