Acrylic Block Copolymer Toughens Epoxy Resin
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Solution Overview
Problem
Epoxy resin compositions face challenges in achieving a balance between fracture toughness, heat resistance, elastic modulus, and adhesive strength, with conventional methods often degrading heat resistance and elastic modulus when attempting to improve toughness, and typically compromising shear adhesive strength with peel adhesive strength.
Innovation Solution
A curable epoxy resin composition is developed by blending a bisphenol A epoxy resin with a phenol novolac resin curing agent and an acrylic block copolymer having specific molecular weight and molecular weight distribution, forming a microphase separation structure that enhances fracture toughness, peel adhesive strength, and shear adhesive strength while maintaining heat resistance and elastic modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reactive rubber or polymer particles are added to improve fracture toughness, then toughness is improved, but heat resistance and elastic modulus are degraded
Solution Approach 1:
The invention changes the chemical structure parameters of the polymer particles by specifying they must be composed of (meth)acrylate units with particular glass transition temperatures (Tg). The hard segments have Tg of 80°C or higher while soft segments have Tg of -50°C to 0°C, creating a controlled microphase separation structure that maintains heat resistance while improving toughness
Solution Approach 2:
The invention creates a composite structure within the polymer particles themselves, consisting of hard segments and soft segments in a microphase separated arrangement. This internal composite structure allows the particles to simultaneously provide toughness enhancement while maintaining the heat resistance and elastic modulus of the epoxy resin matrix
2Strength
If block copolymer containing polybutadiene is added to improve toughness, then fracture toughness is improved, but weather resistance is degraded
Solution Approach 1:
The invention changes the chemical composition parameters by selecting (meth)acrylate units instead of polybutadiene. The specific glass transition temperature ranges of the (meth)acrylate-based segments provide the necessary toughness while the saturated (meth)acrylate structure ensures excellent weather resistance by eliminating unsaturated double bonds that would otherwise degrade under UV exposure
3Strength
If epoxy resin composition with thermoplastic resin is prepared to improve impact resistance, then impact resistance is improved, but viscosity increases and handling properties deteriorate
Solution Approach 1:
The invention changes the molecular weight parameters of the polymer particles, specifying weight average molecular weight of 30,000 to 300,000 and number average molecular weight of 10,000 to 100,000. This controlled molecular weight range, combined with the specific (meth)acrylate composition, optimizes the balance between impact resistance and viscosity, maintaining good handling properties while achieving excellent impact resistance
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 resulting cured resin exhibits excellent fracture toughness, high peel and shear adhesive strengths, and retains heat resistance and elastic modulus, making it suitable for various applications including electronic materials, printed circuit boards, and composite materials.
Implementation Method 1
forming a microphase separation structure that enhances fracture toughness, peel adhesive strength, and shear adhesive strength while maintaining heat resistance and elastic modulus
Data Source
AI summary
A curable resin composition, which contains, with respect to 100 parts of an epoxy resin, 1 to 70 parts of an epoxy resin curing agent and 1 to 50 parts of an acrylic block copolymer, and the acrylic block copolymer contains (α) at least one polymer block A composed of a structural unit derived from an alkyl methacrylate and at least one polymer block B composed of a structural unit derived from an alkyl acrylate, has a weight average molecular weight (Mw) of 30,000 to 300,000 and a molecular weight distribution (Mw/Mn) of 1.5 or less, and contains 3 to 60 percent by mass of the polymer block A. In addition, a cured resin is formed from the above curable resin composition.