FUMED METAL OXIDES

APPLICATION GUIDE CAB-O-SIL® FUMED SILICA IN ONE-COMPONENT POLYURETHANE

Application Description

One-component, moisturing-curing polyurethane adhesives used for elastic bonding in construction, industrial assembly and automotive applications require strength and flexibility. Cabot’s treated fumed silicas impart thixotropy in adhesives, enabling the adhesives to shear-thin for easy dispensing and application, yet be non-sagging and have stable bond lines until cured. Treated fumed silica can enhance mechanical properties of the cured , resulting in greater tensile strength, elongation and shear strength.

CABOT PRODUCT OFFERING

CAB-O-SIL Fumed Base Silica Treatment Silica Products Surface Area (m2/g) Agent Selection Guidelines

DiMeDi Promotes reinforcement with no significant increase in viscosity, TS-610 130 Dimethyldichlorosilane suitable for adhesives not requiring sag resistance.

PDMS Widely used by formulators to create sag-resistant adhesives TS-720 200 with shear-thinning behavior.

PDMS One of the best commercially available additives to promote sag ULTRABOND™ 200 Polydimethylsiloxane resistance.

The base silica surface areas in the chart above are typical values only and not product specifications. Product specifications are available from your Cabot representative.

Untreated fumed silica is hydrophilic, adsorbing undesirable Water Adsorption of Fumed Silicas amounts of water in ambient conditions. For this reason, at a Range of Relative Humidities hydrophobic, surface treated fumed silica is suggested for 9 the formulation of moisture-curing polyurethane adhesives CAB-O-SIL Fumed Silica: TS-720 TS-610 to promote good stability and shelf-life. 8

7

Unreated Fumed Silica Treated Fumed Silicas 6 Treatment of fumed

CH3 CH3 silica with PDMS and

CH3 CH3 CH3 CH3 5 DiMeDi can significantly Si Si Untreated Silicas increase hydrophobicity, 2 O O 200 m /g CH3 CH3 CH CH CH CH 4 reducing the amount of H CH3 O CH3 3 Si 3 3 Si 3 H H H Si Si m n 150 m2/g H O water adsorbed on the

O O (% change in weight) OO O O O O H 3 O O O OO O O H Adsorption Water silica surface. O Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si Si 2

CAB-O-SIL M-5 CAB-O-SIL TS-610 CAB-O-SIL TS-720 1 Treating agent: Treating agent: Dimethyldichorosilane Polydimethylsiloxane 0 0 20 40 60 80 100 Hydrophilic Hydrophobic Relative Humidity at 25 ºC (%) CAB-O-SIL® FUMED SILICA IN ONE COMPONENT POLYURETHANE ADHESIVES APPLICATION GUIDE PRODUCT PERFORMANCE – REINFORCEMENT

Treated fumed silica used in formulation of one-component polyurethane (1K PU) adhesives enhances: ◆ Tensile Strength ◆ Shear Strength ◆ Elongation

Effect of Fumed Silica on Tensile Strength Effect of Fumed Silica on Elongation (in 1K PU Adhesive) (in 1K PU Adhesive)

CAB-O-SIL Fumed Silicas: CAB-O-SIL Fumed Silicas: 2.0% ULTRABOND 2.0% ULTRABOND TS-720 TS-720 TS-610 TS-610

3.8% 3.8%

5.6% 5.6% Loading (wgt. %) (wgt. Loading %) (wgt. Loading

7.4% 7.4%

Base Formulation without Fumed Silica Base Formulation without Fumed Silica 10.7% 10.7%

0 0.5 1 1.5 2 2.5 3 0 100 200 300 400 500 600 700 800 Tensile Strength (MPa) Elongation at Break (%)

The addition of even low loadings of fumed silica will increase The addition of fumed silica increases elongation. the tensile strength. At higher loading levels, CAB-O-SIL TS-610 DiMeDi treated silica provides greater reinforcement than the PDMS treated silicas.

Effect of Fumed Silica and Coated Precipitated Performance Comparison of Coated Precipitated Calcium Carbonate (PCC) on Lap Shear Strength Calcium Carbonate (PCC) with PDMS–treated Silicas (in 1K PU Adhesive) (in 1K PU Adhesive)

1.4 1000 900 3.8% by wt. Silica or Coated PCC 800 1.3 1800 700 600 1.2 TS-610 1600 500 PCC 2* 400 1.1 300 1400 200 1.0 100

1200 (kPa) Strength Adhesion Lap Shear 0 PCC/No ULTRABOND TS-720 TS-610 0.9 1000 Silica 0.8 800 ULTRABOND TS-720 0.7 600 PCC 1* Tesnsile Strength (MPa) Strength Tesnsile 0.6 PCC 2* 400

200 0.5 0 2% 4% 6% 8% 10%12% 14% 16% 18% 20%

Lap Shear Adhesion Strength (kPa) Strength Adhesion Lap Shear 0 5% 10% 15% 20% Silica or Coated PPC Loading (wt. %) Silica or Coated PPC Loading (wt. %)

Coated Precipitated Calcium Carbonate (PCC) has only a While both coated Precipitated Calcium Carbonate (PCC) modest effect on Lap Shear Adhesion Strength, while fumed and treated fumed silica can provide thixotropy, enabling silica significantly increases this strength. formulation of sag-resistant adhesives, coated PCC has only a modest impact on mechanical properties.

*Precipitated CaCO3 (PCC 1); stearic acid coated, average particle size 0.07 microns. Precipitated CaCO3 (PCC 2); fatty acid coated, mean particle diameter 40 -130 nm. CAB-O-SIL® FUMED SILICA IN ONE COMPONENT POLYURETHANE ADHESIVES APPLICATION GUIDE PRODUCT PERFORMANCE – CONTROL

Treated Fumed Silica can provide the following performance enhancements for one-component polyurethane adhesives: ◆ Non-slumping, sag-resistance ◆ Anti-settling of fillers ◆ Shear-thinning for easy application ◆ Increased viscosity ◆ Fast recovery/rebuild of viscosity

Effect of Silica Surface Chemistry on Rheology Cabot PDMS Treated Silicas for Rheology Control (in 1K PU Adhesive) (in 1K PU Adhesive)

TS-720 (7.4%) TS-610 (7.4%) 120 10,000 fumed silica fumed silica 10,000 100 80 TS-720 (2.0%) TS-610 (2.0%) 60 fumed silica fumed silica 40 20 Base Formulation (Pa) Stress Yield 0 1,000 1,000 ULTRABOND TS-720 fumed silica fumed silica ULTRABOND fumed silica 100 100 TS-720 Silica Loading fumed silica 5.6% by weight Viscosity (Pa-sec) Viscosity (Pa-sec) Viscosity

10 10 0.01 0.1 1 10 0.01 0.1 1 10 Shear Rate (sec1) Shear Rate (sec1)

Silica surface treatment strongly influences rheological Cabot offers a range of highly hydrophobic, PDMS-treated performance. Selecting a highly hydrophobic silica, such silicas for rheology control of 1K PU adhesives. Of these, as CAB-O-SIL TS-720 fumed silica, imparts thixotropic or CAB-O-SIL ULTRABOND fumed silica provides the greatest shear-thinning behavior in one-component polyurethane increase in viscocity and sag resistance as predicted by adhesives. In contrast, a moderately hydrophobic silica, yield stress. such as CAB-O-SIL TS-610 fumed silica, imparts small increases in viscosity without thixotropy or shear-thinning behavior, even at increased loadings.

Performance Comparison of Coated Precipitated Performance Comparison of Cabot Calcium Carbonate with PDMS Treated Silica and Competitive PDMS Treated Silica (in 1K PU Adhesive) (in 1K PU Adhesive) 10,000 120 9,000 ULTRABOND TS-720 5.6% 5.6% 5.6% 8,000 PCC 1 100

(Pa-sec) 7,000 PCC 2 -1 6,000 80 5.6% 5.0% 5,000 5.6% 4.8% 4,000 60 3,000 5.6% 4.1% Yield Stress (Pa) Stress Yield 2,000 40 1,000 Viscosity at 0.01 sec Viscosity 0 20 0% 2% 4% 6% 8% 10% 12% 14% 16% 18% 20% ULTRABOND A* Competitor ULTRABOND ULTRABOND B* Competitor ULTRABOND ULTRABOND C* Competitor ULTRABOND Loading (wt.%) 0

While coated Precipitated Calcium Carbonates (PCC) do ULTRABOND fumed silica is one of the best thixotropes on increase viscosity and impart thixotropy in 1K PU adhesives, the market for 1K PU adhesives. With ULTRABOND fumed PDMS-treated fumed silicas are more efficient. Using a silica, significantly lower loadings are required to achieve PDMS-treated fumed silica can provide sag resistance and excellent sag resistance when compared with competitive rheology control without the significant weight (specific PDMS-treated silica. gravity) increase encountered with use of coated PCCs. *Competitive A, B and C; polydimethylsiloxane surface modified fumed silicas CAB-O-SIL® FUMED SILICA IN ONE COMPONENT POLYURETHANE ADHESIVES APPLICATION GUIDE PRODUCT PERFORMANCE

Cabot’s portfolio of treated CAB-O-SIL® TS-610 fumed silicas for use in 1K fumed silica PU adhesives enables the Highest formulator to readily optimize:

◆ Sag-Resistance ® ULTRABOND™ CAB-O-SIL TS-720 ◆ Reinforcement fumed silica fumed silica Medium CAB-O-SIL ULTRABOND

Reinforcement fumed silica offers superior performance with respect to Coated PCC sag resistance. Lowest

Lowest Medium Highest Sag Resistance

MODEL FORMULATION

Base Formulation Raw Materials

Prepolymer...... 100 phr ◆ Polyurethane prepolymer; NCO content < 2.0%, viscosity ~22,000 cps DIDP Plasticizer...... 50 phr ◆ Diisodecyl Phthalate Calcium Carbonate...... 100 phr ◆ Ground Calcium Carbonate; median particle size 20 microns Tin Catalyst...... 1 phr ◆ Dibutyltin Dilaurate

Thixotropes

5 phr 10 phr 15 phr 20 phr 30 phr Treated Fumed Silica 2.0% 3.8% 5.6% 7.4% 10.7% 15 phr 30 phr 45 phr 60 phr Coated Precipitated Calcium Carbonate 5.6% 10.7% 15.2% 19.3%

Compounding Uncured Property Testing Cured Property Testing

◆ Silica and ground CaCO3 dried under ◆ Controlled stress rheometer using ◆ All test specimens cured 14 days at

vacuum at 200 °C 20 mm parallel plates with dry N2 gas 25 °C/50% RH purge around Peltier plate ◆ Coated PCC dried under vacuum ◆ Tensile Strength and Elongation per at 100 °C ◆ Yield Stress determined using ASTM D412 Herschel-Bulkley Model: = + K n ◆ Mixed in centrifugal orbital mixer τ τ° γ ◆ Lap Shear Adhesion per ASTM D1002 where is shear stress, is yield τ τ° on silane treated aluminum substrate, ◆ Vacuum applied to remove stress, γ is shear rate and K and n entrained air 1" x 1" bond area, 1.7 mm bond are model factors thickness ◆ Moisture scavenger, p-Toluenesulfonyl

Isocyanate (PTSI), used to adjust H2O content of adhesive to < 500 ppm

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