Polyurethane Adhesives Using Poly(butylene Oxide) Prepolymers
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Solution Overview
Problem
Polyurethane adhesives are sensitive to water and humidity, leading to significant changes in modulus and elongation under varying temperature and moisture conditions, which affects their performance in applications exposed to outdoor or uncontrolled environments.
Innovation Solution
A two-component polyurethane adhesive composition comprising a polyol component with polyether polyols, diol chain extenders, aliphatic amines, urethane catalysts, and particulate fillers, and a polyisocyanate component with isocyanate-terminated poly(butylene oxide) prepolymers and polyisocyanate compounds, formulated to maintain stability and performance in humid and temperature-varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyurethane adhesives are used, then good adhesive properties and curing performance are achieved, but the adhesive loses desirable properties when exposed to liquid water and humid conditions, especially at elevated temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by using poly(butylene oxide) prepolymers with specific molecular weights (1000-6000 g/mol) and controlling the isocyanate index (1.05-1.30), along with specific ratios of polyether polyols (35-70 wt%) and polyester polyols (30-65 wt%), to achieve resistance to water and humidity while maintaining adhesive properties
Solution Approach 2:
The patent creates a composite adhesive system combining poly(butylene oxide) prepolymers with polyether polyols and polyester polyols in specific proportions, where each component contributes different properties: poly(butylene oxide) provides water resistance, polyether polyols provide flexibility and adhesion, and polyester polyols provide strength, achieving overall performance stability in humid conditions
2Stability of the object's composition
If polyurethane adhesive is exposed to elevated temperature and moisture, then the adhesive experiences a loss in modulus and a significant increase in elongation, but maintaining property stability requires resistance to these environmental conditions
Solution Approach 1:
The patent optimizes the molecular weight parameters of the poly(butylene oxide) prepolymer (1000-6000 g/mol) and controls the isocyanate index (1.05-1.30) to achieve a balance between crosslinking density and chain flexibility, resulting in modulus and elongation stability across a wide temperature range from -40°C to 100°C while resisting humidity effects
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 adhesive exhibits marked resistance to heat and humidity, with minimal changes in modulus and elongation, and demonstrates high modulus and tensile strength even after humid aging, ensuring consistent performance in challenging environmental conditions.
Implementation Method 1
the isocyanate equivalent weight of the polyisocyanate component and the equivalent weight per isocyanate-reactive group of the polyol component are such that when the polyisocyanate component and the polyol component are mixed at a 1:1 ratio by volume the isocyanate index is 1.1 to 1.8
Data Source
AI summary
Two-component polyurethane adhesives include a polyol component and a polyisocyanate component. The polyol component includes a polyether polyol and an aliphatic diol chain extender. The polyisocyanate component includes an isocyanate prepolymer made by reacting an aromatic polyisocyanate with a poly(butylene oxide) polyol. When cured, the adhesive is highly resistant to heat and humidity, and exhibits an unexpectedly high modulus and tensile strength.