Epoxy Hybrid Structural Adhesive with IPN for Low Modulus Bonding

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current structural adhesives do not effectively address the need for low modulus, high elongation characteristics for bonding similar and dissimilar substrates, particularly in applications requiring energy absorption during distortion and thermal expansion.

Innovation Solution

The development of a unique epoxy hybrid structural heat curable adhesive formulated with epoxy-modified dimerized fatty acids combined with an epoxy terminated polyurethane interpenetrating network (IPN) and a standard liquid diglycidylether of bisphenol-A, which provides superior mechanical properties for OEM bonding applications.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional structural adhesives are used, then bonding strength is achieved, but modulus remains high and elongation remains low, preventing effective energy absorption during distortion

Engineering Contradiction:

Improvebonding strengthVSAvoidmodulus

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The patent employs an interpenetrating polymer network (IPN) comprising two distinct polymer networks: a rigid epoxy network providing high bonding strength and a flexible polyurethane network providing low modulus and high elongation. These networks are interpenetrated at the molecular level, creating a composite material that simultaneously exhibits both high strength and high elasticity, resolving the contradiction between bonding strength and modulus.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the chemical composition and crosslink density parameters of the adhesive system by incorporating flexible polyurethane segments with specific molecular weights and flexibility characteristics. By adjusting the ratio and structure of the polyurethane component within the IPN, the adhesive achieves optimized modulus and elongation parameters while maintaining bonding strength.

Inventive Principle:

Principle #35Parameter changes

2Strength

If conventional structural adhesives are used, then bonding strength is achieved, but elongation remains low, limiting energy absorption capability

Engineering Contradiction:

Improvebonding strengthVSAvoidelongation

Core Design Contradiction:

StrengthVSLength of moving object

Solution Approach 1:

The IPN structure combines a rigid epoxy network for strength with a flexible polyurethane network for elongation. The polyurethane chains can stretch and deform significantly, allowing the adhesive to undergo large elongations ( exceeding 100%) while the epoxy network maintains structural integrity and bonding strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the adhesive exhibit different mechanical properties: the epoxy-rich regions provide bonding strength and structural stability, while the polyurethane-rich regions provide elasticity and elongation. This local differentiation of properties within the homogeneous IPN structure enables simultaneous achievement of high strength and high elongation.

Inventive Principle:

Principle #3Local quality

3Strength

If rigid adhesives are used, then bonding strength is maintained, but ability to absorb thermal expansion and distortion energy is reduced

Engineering Contradiction:

Improvebonding strengthVSAvoidenergy absorption

Core Design Contradiction:

StrengthVSUse of energy by moving object

Solution Approach 1:

The IPN adhesive acts as a energy absorption system where the flexible polyurethane network dissipates mechanical and thermal energy through chain deformation and molecular motion. During thermal expansion or impact events, the polyurethane component absorbs energy elastically and viscoelastically, preventing stress concentration and bond failure while the epoxy network maintains bonding strength.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The flexible polyurethane network in the IPN structure provides pre-configured energy absorption capability that cushions against thermal expansion and distortion forces before they can cause damage to the bonded substrates or the bond itself.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 the lowest modulus and highest elongation seen heretofore, effectively absorbing bonded substrates' movement during cure and dynamic climate conditions, minimizing thermal alignment issues and enhancing coefficient of linear thermal expansion.

Implementation Method 1

Due to the extremely low modulus and high elongation, the adhesive absorbs energy produced during distortion of similar or dissimilar or softer metal

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

the adhesive absorbs energy produced during distortion of similar or dissimilar or softer metal which occurs, for example, during an e-coat oven curing process and/or any dynamic climate condition

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20220041898A1Low modulus, high elongation structural adhesives and associated bonded substrates

Publication Date: 2022.02.10 UNISEAL

AI summary

A substrate assembly, including: (a) a first substrate; (b) a second substrate; and (c) a thermosetting adhesive associated with at least a portion of the first and second substrates, wherein the thermosetting adhesive includes a curing agent, and an epoxy-modified dimerized fatty acid combined with an epoxy terminated polyurethane interpenetrating network.