High elasticity and stability for long lasting solutions
Sealants (low modulus)
A low modulus sealant is defined as an elastomeric material with a modulus at 100 % elongation of up to 0.4 MPa. This property can be obtained simply by the addition of an appropriate plasticizer. However, being non-reactive and not chemically anchored into the formulation, the plasticizer product can in turn have negative effects on properties like the elastic recovery.
Increasing the plasticizer content lowers the crosslinking density of the cured formulation and therefore tends to shift the visco-elastic properties to the more viscous side. Since a Class 25 LM low-modulus sealant according to ISO 11600 is also required to display a minimum of 70 % of elastic recovery, a formulation highly loaded in plasticizer is unlikely to fill this requirement.
The formulation of low modulus sealants requires on the one hand a polymer that forms an excellently cross-linked network for high recovery, but on the other hand a lower density of cross-linking points for high elongation at the same time.
Furthermore, it is absolutely important to have acceptable skin formation time to ensure fast processing and at the same time dry and non-tacky surfaces to avoid dirt pick up. The ability to formulate products with high stability against climate changes and UV light and at an attractive cost-performance-ratio by allowing the addition of higher filler contents (up to 60%) is completing the picture of requested product features.
The products described here are needed for low modulus construction, transport, or assembly applications. All these features can be covered using Polymer ST or TEGOPAC®.
Suitable products for applications in low modulus sealants can be found in the product listing.
- Polymer ST 77
Polymer ST 77 is free of phthalates and is highly recommended for demanding applications where a balanced stress-strain behavior is re-quired as in transport and assembly applica-tions. Examples for the use of Polymer ST 77-based formulations are the assembly of superstructural parts, bumpers, etc. Mechanical fastening is often avoided as it could cause damage to the materials used. In addition, it could negatively affect the design.
- TEGOPAC® Bond 170
TEGOPAC® Bond 170 is a silylated polymer that is used for production of neutral curing adhesives and sealants. The polymer is based on a unique polymer technology with lateral crosslinking groups. TEGOPAC® Bond 170 shows excellent through cure properties, improved water & thermal resistance and excellent elastic recovery properties. The low polymer viscosity allows quick & easy handling.
- TEGOPAC® RD I
TEGOPAC® Reactive Diluents (RD) are silanemodified polymers which can be used to reduce viscosities of adhesives & sealant formulations. TEGOPAC® RD I is used for viscosity reduction, to avoid migration effects and can improve through cure properties. *Not yet available in the Americas*
- TEGOPAC® RD II
TEGOPAC® Reactive Diluents (RD) are silanemodified polymers which can be used to reduce viscosities of adhesives & sealant formulations. TEGOPAC® RD I is used for viscosity reduction, to avoid migration effects and can improve through cure properties. TEGOPAC® RD II in addition can increase hardness & tensile strength. *Not yet available in the Americas*