Sulfur-Curable Adhesive for Crash-Resistant Bonding
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Solution Overview
Problem
Current crash-resistant adhesives used in the automotive sector, particularly at low temperatures, suffer from brittleness and lack of impact resistance, and often contain harmful compounds like bisphenol A.
Innovation Solution
A sulfur-curable rubber-based composition comprising anhydride and/or acid modified rubber, aromatic rubber, non-anhydride/acid modified rubber copolymer, and a sulfur-based crosslinking agent, which improves impact resistance and lap shear strength over a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If sulfur-curable rubber-based compositions are used as adhesives, then they avoid harmful epoxy compounds, but they become brittle at low temperatures and lose impact resistance
Solution Approach 1:
The invention uses a composite rubber formulation combining multiple rubber types (polybutadiene, polyisoprene, nitrile butadiene copolymer) with specific glass transition temperatures and saturation levels. This composite approach allows the adhesive to maintain flexibility and impact resistance at low temperatures while remaining sulfur-curable and free from harmful epoxy compounds.
Solution Approach 2:
The invention carefully controls specific parameters including glass transition temperature (Tg) within -100°C to -50°C range, saturation level between 30-70%, and unsaturation level between 30-70%. By optimizing these parameters, the adhesive maintains both low-temperature flexibility and proper cure characteristics without requiring harmful epoxy compounds.
2Strength
If current crash-resistant adhesives are used, then they provide high impact strength at low temperatures, but they contain harmful compounds like bisphenol A
Solution Approach 1:
The invention converts the traditionally harmful aspect of sulfur-curable rubbers (brittleness at low temperature) into a benefit by using it as the base material, then compensating for the brittleness through carefully selected rubber combinations and controlled saturation/unsaturation levels. This eliminates the need for harmful epoxy compounds while maintaining low-temperature impact strength.
Solution Approach 2:
The adhesive uses a composite formulation of multiple rubber types with complementary properties. The combination of polybutadiene, polyisoprene, and nitrile butadiene copolymer creates a material that provides both the flexibility needed for low-temperature impact resistance and the cure characteristics needed for structural bonding, replacing harmful epoxy-based solutions.
3Object-affected harmful factors
If sulfur-curable rubber-based compositions are used, then they are free from epoxy compounds, but they exhibit brittleness and poor lap shear properties at low temperatures
Solution Approach 1:
The invention optimizes specific parameters including acid number (40-160 mg KOH/g), anhydride content (1-50%), and the ratio of saturated to unsaturated rubber components. These parameter adjustments ensure the adhesive maintains proper flexibility and bonding characteristics at low temperatures without requiring epoxy compounds, achieving both lap shear strength and impact resistance.
Solution Approach 2:
The use of a composite rubber system with multiple polymer types provides the flexibility and adhesion needed for strong lap shear bonding at low temperatures. The specific combination of rubber types creates a material that cures well with sulfur while maintaining elastomeric properties necessary for structural adhesive performance without harmful epoxy additives.
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 sulfur-curable composition achieves enhanced impact resistance at 23°C and lower temperatures, such as -35°C, while maintaining good lap shear strength, thus addressing the limitations of existing adhesives.
Implementation Method 1
a sulfur-based crosslinking agent
Implementation Method 2
anhydride and/or acid modified rubber
Data Source
AI summary
The invention relates to a sulfur-curable composition comprising: - an anhydride and/or acid modified rubber, - an aromatic rubber, - a non-anhydride/acid modified rubber copolymer, and - a sulfur-based crosslinking agent. Furthermore, the invention relates to a method for bonding substrates comprising the steps of: - coating, on at least one surface of the substrates, of the sulfur-curable composition according to the invention, then - contacting the substrates. The invention also relates to an article comprising the sulfur-curable composition according to the invention, said composition bonding at least two substrates of said article. Finally, the invention relates to the use of the sulfur-curable composition according to the invention as an adhesive, in particular a crash-resistant adhesive.