Precipitated Silica BET 165 m²/g

What Is BET 165 m²/g Precipitated Silica?

Precipitated silica with BET surface area of 165 m²/g occupies the mid-range position in the commercial precipitated silica product spectrum. It offers meaningfully higher reinforcement potential than BET 115 m²/g grades while remaining more processable than the ultra-high surface area 200–220 m²/g grades used in premium green tire applications.

BET 165 m²/g is the workhouse grade for truck and bus tire tread compounds, passenger car replacement tires with moderate rolling resistance targets, and higher-performance shoe soles where white coloration and improved wet traction are specified. It represents the practical compromise grade where good mechanical properties and acceptable processing conditions coexist without demanding the specialized mixing protocols required by highly dispersible grades.

BET Surface Area and Performance Implications

At 165 m²/g, this silica delivers the following compound characteristics:

Tensile strength: 16–22 MPa in NR/SBR compounds at 50 phr loading, exceeding the BET 115 performance tier. The higher surface area creates a denser filler-polymer interface network after silane coupling.

Tear resistance: Improved versus BET 115 grades, making the 165 grade suitable for truck tire tread edges and sidewall compounds where tear resistance under flex is important.

Compound viscosity: DBP absorption of 210–240 mL/100g creates a moderate viscosity increase. Mooney viscosity increase from 50 phr silica addition is approximately 25–40 ML(1+4) units above base, requiring appropriate oil or plasticizer balance.

Dispersion: BET 165 m²/g disperses adequately with two-pass mixing in most rubber systems. Conventional powder grade can form some agglomerates; for critical applications, a granule form is preferred.

Silane demand: Si-69 at 8–10 phr is the standard dosage for full silanization. The higher surface area compared to BET 115 requires proportionally more silane to achieve complete coverage.

Performance in Rubber Compounding

Truck tire tread (NR/SBR 70/30 blend, 50 phr silica): BET 165 m²/g in natural rubber-dominant compounds delivers tread wear index 15–25% higher than carbon black grades at equivalent loading, with moderate rolling resistance improvement. The NR-rich compound system provides the cut and chip resistance needed for commercial vehicle off-highway applications.

Passenger car tire (SSBR/BR blend, 60 phr silica): At BET 165 m²/g with Si-69 coupling, this formulation reaches EU label B–C rolling resistance performance. Wet grip is improved versus carbon black compounds. For label A-rated tires, BET 175 or higher with HD grades is required.

Shoe sole (NR, 50 phr silica): BET 165 m²/g delivers better abrasion resistance than the 115 grade. DIN abrasion volume loss reaches 100–140 mm³ in properly formulated NR compounds. The increased surface area also improves tear strength and flex fatigue life.

Recommended Compound Systems

Truck tire tread — NR/SBR blend:

• NR (Pale Crepe or RSS): 70 phr
• SBR 1502: 30 phr
• Precipitated silica BET 165: 50 phr
• Si-69 silane: 7 phr
• Carbon black N330: 10 phr (hybrid reinforcement)
• Aromatic oil: 10 phr
• ZnO: 4 phr, Stearic acid: 2 phr
• Sulfur: 1.5 phr, CBS: 1.8 phr, DPG: 0.5 phr

PCR tire tread — SSBR/BR blend:

• SSBR (solution SBR, 23.5% vinyl): 80 phr
• BR (cis-polybutadiene): 20 phr
• Precipitated silica BET 165 (granule): 60 phr
• Si-69 silane: 8 phr
• Process oil (TDAE): 15 phr
• ZnO: 2.5 phr, Stearic acid: 2 phr
• Sulfur: 1.5 phr, CBS: 2 phr, DPG: 1.5 phr

Processing Tips

Two-pass mixing: For BET 165 m²/g, a two-pass Banbury mixing sequence is strongly recommended. First pass: add silica and silane at the first drop (90–100°C), dump at 150–160°C for 3–4 minutes silanization time. Second pass: add curatives at lower temperature (70–80°C initial), dump at 110–120°C.

Silanization temperature control: Si-69 silanization requires sustained temperatures of 150–165°C. Below 145°C, the coupling reaction is slow and incomplete; above 170°C, pre-mature crosslinking (scorch) can occur. Monitor dump temperature carefully.

DPG (diphenylguanidine): Using 1.5–2 phr DPG as secondary accelerator in silica compounds improves bound rubber formation and helps deactivate surface silanols that could retard vulcanization.

FAQ

Q: Is BET 165 m²/g the right choice for green tire treads? A: It can meet B–C grade label targets but not A-grade. For A-grade rolling resistance, BET 175–220 m²/g with HD dispersibility is required. BET 165 is the practical choice for cost-conscious tire formulations, truck tires, and markets where label A is not targeted.

Q: Can I use powder or must I use granule form? A: Both work. Powder disperses slightly faster due to initial surface exposure but creates more dust in handling. Granule is preferred from a health and safety standpoint and typically gives equivalent dispersion quality in properly designed two-pass mixing.

Q: What is the COA parameter I should focus on for incoming QC? A: BET surface area (within ±10 m²/g of nominal), CTAB surface area (closer correlation to rubber performance), DBP (affects compound viscosity planning), and pH (6.0–8.0, critical for cure system compatibility). Also check SiO₂ content (≥98%) and moisture (≤7.0%).