The role of fumed silica in the formulation of adhesives and sealants
2017/1/11
Particles
are often used in product formulations for adhesives and sealants for
polymer substrates to enhance product functionality. The
generic term "fumed silica" refers to a wide range of particulate
products having different surface chemistry, from hydrophilic to
hydrophobic. Fumed
silica is commonly used as a rheology control additive; provides sag
resistance, prevents filler settling, and shear thinning viscosity. This series of products in different polymer systems show different
compatibility, making the formula in the rheological properties can be
achieved fine-tuning.
At the same time, the formulation system enhances the viscoelastic response of the liquid system by controlling the interaction of the particles with the particles and the adhesion of the particle-matrix interface, which can produce the desired viscoelasticity and also a hard-to-bond hard A material that extends the fracture path and dissipates part of the energy at the interface junction 1, these properties make the material properties significantly higher. In this paper, the results of the development of fumed silica in recent years are introduced. It is shown that these interactions can help researchers and engineers develop new adhesives and sealants.
Fumed silica not only proves its effectiveness in rheological control, but also enhances the strength of the cured adhesive. The three examples herein describe the reinforcement of the polymer by fumed silica to obtain a higher performance adhesive or sealant.
Transparent silane-terminated polymers
High-definition STP type adhesives and sealants are preferred by consumers in the "DIY" market. In Europe, the production of these products has been switched to transparent packaging to highlight this advantage. Product formulations such as wax, clay and calcium carbonate as additives to achieve rheological control and STP adhesives and sealants reinforcement, these auxiliaries due to refractive index and the polymer matrix does not match the product opaque, fumed silica In contrast, the refractive index is very close to that of the polymer matrix without significantly affecting the clarity of the product. Fumed silica is therefore widely used as a reinforcing agent in transparent STP adhesives and sealants.
The use of hydrophilic fumed silica in the curing system using moisture, such as STP or polyurethane, may result in premature curing of the product due to the fast water adsorption capacity of the hydrophilic silica. There are several options for solving this problem, including the addition of process steps (pre-drying of hydrophilic silica, or removal of water during mixing by heat and vacuum); or the addition of additional components (chemical desiccant); a better Of the choice is to use hydrophobic rather than hydrophilic type fumed silica, can greatly reduce or even eliminate these additional processing steps.
Two hydrophobic fumed silica additives, CAB-O-SIL® TS-610 or CAB-O-SIL® TS-720, were blended in a mixture containing MS Polymer ™ SAX400 silyl terminated polyether, Nonyl esters and organotin catalysts, the rheological effects conferred by the surface chemistry of fumed silica in the system can be clearly observed. Fumed silica CAB-
The weaker hydrophobicity of O-SIL® TS-610 enhances the particle-matrix interaction and provides rheological properties near Newtonian fluids. In contrast, CAB-O-SIL® TS-720 has strong hydrophobic properties, weakening the particle-matrix interaction and enhancing the particle-particle interaction, resulting in thixotropic behavior. The system has a certain yield stress, Sag resistance, and shear-thinning viscosity as shown in Fig.
At the same time, the formulation system enhances the viscoelastic response of the liquid system by controlling the interaction of the particles with the particles and the adhesion of the particle-matrix interface, which can produce the desired viscoelasticity and also a hard-to-bond hard A material that extends the fracture path and dissipates part of the energy at the interface junction 1, these properties make the material properties significantly higher. In this paper, the results of the development of fumed silica in recent years are introduced. It is shown that these interactions can help researchers and engineers develop new adhesives and sealants.
Fumed silica not only proves its effectiveness in rheological control, but also enhances the strength of the cured adhesive. The three examples herein describe the reinforcement of the polymer by fumed silica to obtain a higher performance adhesive or sealant.
Transparent silane-terminated polymers
High-definition STP type adhesives and sealants are preferred by consumers in the "DIY" market. In Europe, the production of these products has been switched to transparent packaging to highlight this advantage. Product formulations such as wax, clay and calcium carbonate as additives to achieve rheological control and STP adhesives and sealants reinforcement, these auxiliaries due to refractive index and the polymer matrix does not match the product opaque, fumed silica In contrast, the refractive index is very close to that of the polymer matrix without significantly affecting the clarity of the product. Fumed silica is therefore widely used as a reinforcing agent in transparent STP adhesives and sealants.
The use of hydrophilic fumed silica in the curing system using moisture, such as STP or polyurethane, may result in premature curing of the product due to the fast water adsorption capacity of the hydrophilic silica. There are several options for solving this problem, including the addition of process steps (pre-drying of hydrophilic silica, or removal of water during mixing by heat and vacuum); or the addition of additional components (chemical desiccant); a better Of the choice is to use hydrophobic rather than hydrophilic type fumed silica, can greatly reduce or even eliminate these additional processing steps.
Two hydrophobic fumed silica additives, CAB-O-SIL® TS-610 or CAB-O-SIL® TS-720, were blended in a mixture containing MS Polymer ™ SAX400 silyl terminated polyether, Nonyl esters and organotin catalysts, the rheological effects conferred by the surface chemistry of fumed silica in the system can be clearly observed. Fumed silica CAB-
The weaker hydrophobicity of O-SIL® TS-610 enhances the particle-matrix interaction and provides rheological properties near Newtonian fluids. In contrast, CAB-O-SIL® TS-720 has strong hydrophobic properties, weakening the particle-matrix interaction and enhancing the particle-particle interaction, resulting in thixotropic behavior. The system has a certain yield stress, Sag resistance, and shear-thinning viscosity as shown in Fig.
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