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 that delivers more pronounced physical layer separation than fine-particle grades — making it the premier choice for heavy-gauge PE blown sacks, thick BOPP and CPP extrusion runs, agricultural films, and demanding high-stress winding applications.
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.
Key Features
- Optimized Dynamic Topography (d50 4.0–5.0 µm): Deeper surface protrusion for medium-to-thick film webs (gauge 25–60+ µm) creates stronger micro-separation between film contact layers; avoids the under-performance of fine-particle grades in thick-gauge applications.
- Surface-Treated — Direct Extrusion Feed: Agglomeration-resistant surface modification enables reliable incorporation into direct extrusion or masterbatch feeds without secondary milling or wetting agent addition.
- Exceptional Slip Enhancement: Reduces static and dynamic coefficient of friction in demanding high-tension winding environments; enables smooth winding behavior on heavy-duty blown film and cast sheet lines.
- Heavy-Duty Anti-Blocking: Effective at the elevated block pressures encountered in heavy-gauge PE sack rolls, pallet-stacked agricultural film, and industrial shrink packaging stored under load.
- Structural Reinforcement: Contributes to localized surface hardness and resists scuffing during dynamic pulling and transport cycles on automatic packaging equipment.
Technical Specifications
| Parameter | Value | Unit |
|---|---|---|
| SiO₂ Content (dry basis) | ≥99 | % |
| Particle Size d50 (laser diffraction) | 4.0–5.0 | µm |
| pH (5% aqueous dispersion) | 6.0–8.0 | — |
| Oil Absorption | 20–50 | g/100g |
| Loss on Drying (2h @ 105°C) | ≤3.0 | % |
| Loss on Ignition (2h @ 1000°C) | ≤3.0 | % |
| Surface Treatment | Organo-functional | — |
| Packaging | 25 kg PE-lined kraft bags | — |
| Equivalent Grade | Evonik SYLOID® FP246 | — |
Typical values per SEMITECH QC release. Full CoA (d50, pH, LOD, oil absorption) issued per batch.
Applications
- Thick BOPP / CPP Extrusion Lines: 0.15–0.35 wt% masterbatch loading for heavy-gauge BOPP (≥25 µm) and cast sheet configurations; deeper particle protrusion eliminates blocking under compression in roll storage and pallet stacking.
- Heavy-Duty PE Blown Sacks (LDPE/LLDPE): 0.10–0.30 wt% in the blown film compound for agricultural bags, FIBCs, and industrial sacks subject to elevated winding tensions and block pressures in outdoor storage.
- Agricultural Films: Coarser particle profile provides durable blocking resistance in LDPE and LLDPE mulch and greenhouse film rolls stored outdoors under temperature fluctuation and UV exposure.
- Shrink Packaging (LDPE/LLDPE): Reduces COF and blocking tendency in shrink film structures that must unwind and convey reliably through high-speed heat-tunnel packaging lines.
- PET Industrial-Grade Sheets: Provides inter-layer slip and blocking resistance in PET industrial and optical protection films where film-to-film adhesion during sheet stacking is a production risk.
- PVC Plastisols and Rigid/Semi-Flexible Sheets: Compatible in PVC plastisol and calendered rigid/semi-flexible sheet applications requiring blocking resistance under elevated stacking pressures.
When to Choose SA-25 vs SA-23
SA-25 is the correct specification for film gauge above ~25 µm or wherever blocking pressure is elevated (heavy rolls, stacked pallets, outdoor storage). The 4.0–5.0 µm d50 delivers proportionally deeper protrusion geometry, providing stronger anti-blocking efficiency in thicker structures. For thin-gauge films (below 25 µm) or clarity-critical BOPP and OPP applications where optical haze is measured, SA-23 (d50 3.0–4.0 µm) is the appropriate grade; its finer particles minimize light scattering while still providing effective blocking resistance at lower film gauges. Against Evonik SYLOID® FP246 or equivalent imported medium-grade anti-blocking silica, SA-25 delivers the same d50 specification at 30–45% lower landed cost on FCL volumes direct from SEMITECH.