Multiphase Acrylic Adhesive Toughness at Low Temperatures
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Solution Overview
Problem
Acrylic adhesives often produce brittle polymers, requiring toughness enhancement for structural adhesive bonds, especially at sub-ambient temperatures, which existing methods fail to adequately address.
Innovation Solution
A cured (meth)acrylate-based adhesive composition with co-continuous phases and polymeric inclusions, comprising a polymer or copolymer of acrylic or methacrylic acid monomers and carboxylated butadiene acrylonitrile rubber, along with core-shell particles, to achieve improved fracture toughness at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If acrylic adhesives are used for fast room temperature cure and good adhesion, then curing speed and adhesion are improved, but the polymer becomes brittle and toughness is reduced
Solution Approach 1:
The invention creates a composite adhesive system comprising a (meth)acrylate-based polymer matrix combined with polyurethane oligomers containing methacrylic functionality. This composite structure allows the (meth)acrylate component to provide fast curing and adhesion while the polyurethane component contributes flexibility and toughness, resolving the contradiction between curing speed and toughness.
Solution Approach 2:
The invention modifies the chemical composition parameters of the adhesive by incorporating polyurethane oligomers with specific methacrylic functionality into the (meth)acrylate system. This parameter change transforms the polymer properties, enabling simultaneous achievement of fast cure (from (meth)acrylate) and enhanced toughness (from polyurethane)
2Strength
If impact modifiers are added to enhance toughness, then structural adhesive bonds are achieved, but the adhesive formulation complexity increases
Solution Approach 1:
The invention merges the functions of the impact modifier and the adhesive matrix by using polyurethane oligomers with methacrylic functionality. These oligomers simultaneously serve as toughness-enhancing agents and as polymerizable components that integrate into the (meth)acrylate network, eliminating the need for separate impact modifier additions and simplifying the formulation.
3Reliability
If conventional acrylic adhesives are used at sub-ambient temperatures, then adhesion is maintained, but fracture toughness deteriorates significantly
Solution Approach 1:
The invention changes the thermal and mechanical parameters of the adhesive system by incorporating polyurethane oligomers, which have lower glass transition temperatures and greater chain flexibility compared to conventional (meth)acrylate polymers. This parameter modification enables the adhesive to maintain both adhesion and fracture toughness at sub-ambient temperatures where conventional adhesives would become too brittle.
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 composition exhibits enhanced toughness, particularly at -40 °C, with significant improvements in fracture toughness and notched Izod impact strength, providing stronger adhesives at lower temperatures compared to ambient conditions.
Implementation Method 1
Acrylic adhesives cure by free-radical polymerisation of unsaturated compounds, most often esters of methacrylic acid.
Data Source
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AI summary
The invention relates to an uncured, polymerizable composition comprising (A) 1 - 25 % b.w. of the total composition of a rubber, (B) 25 - 75 % b.w. of the total composition of a monomer or monomer blend comprising acrylic or methacrylic acid or a derivative thereof (C) 1 - 50 % b.w. of the total composition of a meth(acrylated) polyurethane and (D) at least one type of core shell particle. Upon cure these compositions exhibit better facture toughness, especially at low temperatures.