Silane-Terminated Polyurethane Adhesives for High Tensile Shear Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional silane-crosslinking adhesives typically achieve only moderate lap shear strengths of 1-4 MPa, with exceptional formulations reaching up to 5 MPa but not exceeding 6.5 MPa in tensile strength, limiting their application in high-strength requirements, and often come with high raw material costs and viscosity issues due to high silane content and urethane/urea group concentrations.
Innovation Solution
A mixture containing silane-terminated polyurethanes with a high percentage of urea groups as end groups, specifically formulated to achieve high tensile shear strengths, utilizing a specific ratio of polyols, di- and polyisocyanates, and aminosilanes to optimize crosslinking density and reduce viscosity, while minimizing isocyanate content for safety and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silane content and urethane/urea group concentration are increased to achieve high tensile shear strength, then adhesive strength is improved, but raw material costs and viscosity increase
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating aminosilane compounds with specific structural characteristics (aliphatic amino groups, controlled alkoxysilane content) to achieve high strength without proportionally increasing viscosity and cost. The specific parameter changes include using aminosilanes with 1-10 carbon atoms in the alkyl chain and controlled ratios of NCO-reactive groups
Solution Approach 2:
The patent creates a composite adhesive system combining polyol, diisocyanate/polyisocyanate, and aminosilane compounds in specific ratios. This composite approach allows the synergistic interaction of different components to achieve high tensile shear strength (exceeding 5 MPa) while maintaining manageable viscosity and reducing reliance on单一 expensive high-silane-content polymers
2Strength
If isocyanate content is increased to accelerate curing and improve strength, then curing rate and adhesive strength are improved, but health safety and storage stability deteriorate
Solution Approach 1:
The patent changes the isocyanate content parameter to a controlled range (0.1-5 wt%, preferably 0.5-2 wt%) rather than using high concentrations. This parameter optimization maintains sufficient curing rate and adhesive strength while significantly reducing the sensitizing and toxic effects associated with high isocyanate content
Solution Approach 2:
The patent introduces aminosilane compounds as intermediary substances that facilitate crosslinking and adhesion. These aminosilanes act as mediators between the isocyanate and substrate, providing bonding functionality while reducing the amount of free isocyanate needed, thereby improving storage stability and reducing health hazards
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves tensile shear strengths exceeding 5 MPa, providing improved mechanical properties and processing ease while maintaining safety and reducing material costs, making the adhesives suitable for high-strength applications.
Implementation Method 1
alkoxysilane-terminated polymers first hydrolyze upon contact with atmospheric moisture
Implementation Method 2
then cure through a condensation reaction
Data Source
AI summary
The invention relates to cross-linkable masses on the basis of silane-terminated polyurethanes, containing at least two different compounds of the formula Y- [NH-C (=0) -NR3- (CR12)b SiRa (OR2) 3.a] x (I), wherein the groups and indices have the meaning specified in claim 1, with the stipulations that some of the groups Y contain at least one urethane group and/or urea group and at least one polyether group and/or polyester group and that more than 50% of all urethane groups and urea groups contained in the compounds of formula (I) of the mixture (A) are urea groups that are part of a terminal group of the formula -NH-C(=0) -NR3- (CR1 2)b-SiRa(OR2) 3-a (II). The invention further relates to methods for the production of said cross-linkable masses and to the use thereof as adhesives and sealants, in particular as adhesives having high tensile shear strength.