Silane Polyurethane Sealant Resolving Strength Elongation Trade-off
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Solution Overview
Problem
Commercially available polyurethane-based sealant compositions for windows and insulating glass units exhibit low elongation and contain isocyanate monomers, necessitating a moisture curable sealant with improved tensile strength and elongation without isocyanate monomers.
Innovation Solution
A moisture curable hot melt sealant composition comprising a silane polyurethane polymer free of isocyanate groups, combined with rosin-based and other tackifying agents, ethylene vinyl acetate copolymers, and a butene component, along with a filler, to achieve enhanced tensile strength and elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyurethane-based sealant compositions are used, then tensile strength is achieved, but elongation is low
Solution Approach 1:
The patent uses a composite formulation combining silane polyurethane polymer with ethylene vinyl acetate copolymer, rosin-based tackifying agents, and other polymers. This composite approach allows the sealant to achieve both high tensile strength (from the polyurethane component) and high elongation (from the flexible EVA and tackifying agent components), resolving the contradiction between strength and elongation.
2Reliability
If isocyanate monomer is included in polyurethane sealants, then moisture curability is achieved, but health and environmental concerns arise
Solution Approach 1:
The patent extracts and eliminates the harmful isocyanate monomer from the sealant formulation while maintaining moisture curability through an alternative mechanism. The silane polyurethane polymer provides moisture curability through silane hydrolysis and condensation reactions instead of isocyanate-based chemistry, removing the harmful substance while preserving the desired function.
Solution Approach 2:
The patent introduces silane-modified polyurethane polymer as an intermediary substance that enables moisture curability without requiring isocyanate monomers. The silane groups on the polyurethane polymer react with moisture to form crosslinked structures, serving as a mediator that achieves the curing function while avoiding the harmful isocyanate pathway.
3Ease of operation
If commercially available polyurethane sealants are used, then ease of application is maintained, but elongation and tensile strength balance is poor
Solution Approach 1:
The patent changes the chemical composition parameters of the sealant by using silane polyurethane polymer with specific molecular weights and incorporating ethylene vinyl acetate copolymers with controlled vinyl acetate content. These parameter changes optimize both the processing characteristics (maintaining application ease) and the mechanical properties (improving tensile strength and elongation balance) of the cured sealant.
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 sealant composition demonstrates improved tensile strength, elongation, and shear adhesion, with a moisture vapor transmission rate and heat resistance, while being free of isocyanate monomers and phthalate plasticizers.
Implementation Method 1
a silane polyurethane polymer that is free of isocyanate groups and derived from polyether
Implementation Method 2
moisture curable hot melt sealant composition
Implementation Method 3
a first ethylene vinyl acetate copolymer, a butene component having a weight average molecular weight from 30,000 Oriole to 700,000 g/mote
Implementation Method 4
from 5% by weight to 30% by weight ethylene vinyl acetate
Implementation Method 5
a butene component having a weight average molecular weight from 30,000 Oriole to 700,000 g/mote, the butene component being selected from the group consisting of polyisobutylene, polyisobutene, polybutene, and combinations thereof
Implementation Method 6
from 1% by weight to no greater than 7% by weight of a butene component
Implementation Method 7
filler
Data Source
AI summary
A moisture curable hot melt sealant composition that includes a silane-modified polyurethane polymer that is free of isocyanate groups, a first rosin-based tackifying agent, a second tackifying agent different from the first rosin-based tackifying agent, a first ethylene vinyl acetate copolymer, a butene component having a weight average molecular weight from 30,000 g/mole to 700,000 g/mole and being selected from the group consisting of polyisobutylene, polyisobutene, polybutene, and combinations thereof; and filler.