SA-23 for Thin-Gauge BOPP and CPP
SEMITECH SA-23 (d50 3.0–4.0 µm, organo-functional treated) is engineered for biaxially oriented PP (BOPP) and cast PP (CPP) film below 25 µm gauge — the dominant thin-film packaging substrate in flexible packaging. At 0.10–0.25 wt% masterbatch loading, SA-23 particles protrude proportionally from the film surface, creating micro-spacers that eliminate film-to-film contact on high-speed industrial winding lines. Optical clarity is preserved: the low oil absorption (20–50 g/100g) minimises forward light scattering, maintaining haze values compatible with clarity-grade BOPP specifications.
SA-25 for Heavy-Gauge PE and Agricultural Film
SEMITECH SA-25 (d50 4.0–5.0 µm) provides the deeper particle protrusion geometry required for medium-to-thick film structures. In heavy-duty LLDPE blown sacks (gauge 80–200 µm), agricultural mulch film, and thick BOPP above 25 µm, the coarser d50 delivers stronger physical layer separation under the elevated winding tensions and block pressures typical of outdoor film roll storage. SA-25 is the specification when SA-23's finer geometry under-performs in heavy-gauge applications.
PET Film and Specialty Substrates
For biaxially oriented PET (BOPET) — used in capacitor film, optical film, and premium packaging laminates — SA-23 is added to the co-extruded skin layer at 0.05–0.15 wt% to control inter-film COF without introducing pin defects in sub-15 µm gauge film. SA-23's ≥99% SiO₂ purity is compatible with PET process requirements.
Supply for Film Converter Operations
SEMITECH ships SA-23 and SA-25 in 25 kg PE-lined multi-wall bags, FCL (18–20 MT, 20′) and HCL (20–22 MT, 40′ HQ). Full batch CoA — d50 particle size (laser diffraction), pH, LOD, oil absorption — is issued per production batch. Private-label masterbatch compounding supply available for converter operations requiring pre-compounded anti-blocking concentrate.
When to Use SA-23 vs SA-25
| Film Type | Gauge | Recommended Grade | Loading Range |
|---|---|---|---|
| BOPP clarity / OPP | 10–25 µm | SA-23 | 0.10–0.25 wt% |
| CPP laminating film | 20–40 µm | SA-23 | 0.10–0.20 wt% |
| CPP retort / thick cast | 40–80 µm | SA-25 | 0.15–0.30 wt% |
| LLDPE stretch wrap | 15–25 µm | SA-23 | 0.08–0.15 wt% |
| LLDPE / HDPE blown sack | 80–200 µm | SA-25 | 0.15–0.50 wt% |
| Agricultural mulch / greenhouse | 80–150 µm | SA-25 | 0.20–0.40 wt% |
| BOPET skin layer | 2–5 µm skin | SA-23 | 0.05–0.15 wt% |
| PVC wrap | 30–100 µm | SA-25 | 0.15–0.35 wt% |
Technical FAQ
+Which grade — SA-23 or SA-25 — should I use for BOPP thin film?
SA-23 (d50 3.0–4.0 µm) is the correct choice for BOPP thin film below 25 µm gauge. The finer particle size keeps protrusion proportional to film thickness, avoiding haze increase and visible surface defects. SA-25 (d50 4.0–5.0 µm) is for medium-to-thick film (≥25 µm) where deeper protrusion is needed.
+What loading level is recommended for anti-blocking silica in blown LLDPE film?
For blown LLDPE stretch wrap and light industrial film, SA-25 is added at 0.10–0.20 wt% in the film compound. For heavy-duty blown sacks under high winding tension or outdoor storage, loading can reach 0.25–0.50 wt%. Always compound via masterbatch carrier (5–20% active in LLDPE) for uniform distribution.
+Can anti-blocking silica affect heat-seal performance in CPP or LLDPE sealant layers?
At standard loadings (0.05–0.20 wt%), impact on heat-seal strength is typically negligible. At higher loadings or when silica is added directly to the sealant layer, some reduction in seal strength initiation temperature is possible. Best practice: restrict silica to the non-seal skin layer in multilayer structures where possible.
+Is SA-23/SA-25 approved for food-contact film applications?
Synthetic amorphous silica is approved as food additive E551 and listed under FDA 21 CFR 172.480 for food-contact applications. SA-23/SA-25 with ≥99% SiO₂ purity are suitable for food-contact film; full CoA and regulatory documentation available on request.
+How do anti-blocking silica grades compare to organic slip agents like erucamide?
Silica anti-blocking agents provide permanent, migration-free anti-blocking via physical micro-spacer geometry. Organic slip agents (erucamide, oleamide) migrate to the surface over time and can bloom, contaminate inks, or fail at elevated temperatures. Silica is preferred for packaging with print or lamination, high-temperature storage, or food contact where organic bloom is a risk.
Recommended Solution
For flexible packaging converters requiring blocking-free film on automatic winding and bag-making lines, specify SEMITECH SA-23 (thin gauge) or SA-25 (heavy gauge) — organo-functional treated synthetic amorphous silica with full batch CoA and FCL supply from Shanghai.