Extrudable Pressure-Sensitive Adhesive Bonding
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Solution Overview
Problem
Bonding low-surface-energy substrates, particularly those with non-planar or porous surfaces, is challenging due to reduced 'wet out' of conventional pressure-sensitive adhesives, leading to weaker bonds and increased complexity and cost with the need for primers and surface treatments.
Innovation Solution
The use of a styrenic block copolymer composition with a hard segment block having a glass transition temperature of 90° C to 220° C, which is heated and masticated to form an adhesive melt composition that can be delivered at a temperature exceeding the glass transition temperature, allowing for bonding without primers and conforming to complex geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional pressure-sensitive adhesives are used on low-surface-energy substrates, then the bonding process is simple, but the bond strength is reduced due to poor wet out
Solution Approach 1:
The adhesive composition's chemical parameters are changed by incorporating specific functional groups (carboxylic acid, hydroxyl, amine) that enhance chemical interaction with low-surface-energy substrates, improving wet out and bond strength without requiring additional processing steps
Solution Approach 2:
The adhesive forms a composite interfacial structure where the modified polymer chains create a transition layer between the low-surface-energy substrate and the adhesive bulk, combining the low-energy substrate's structural properties with the adhesive's bonding properties
2Strength
If primers and surface treatments are applied to improve wet out, then bond strength improves, but process complexity and cost increase
Solution Approach 1:
The adhesive composition integrates multiple functions into a single material: it provides the adhesive matrix, the wetting agents, and the chemical interaction groups all in one application step, eliminating the need for separate primer and surface treatment steps
Solution Approach 2:
The adhesive composition self-adjusts to the substrate surface through its modified polymer chains that automatically orient and interact with the low-surface-energy substrate, eliminating the need for external surface modification processes
3Loss of substance
If conventional adhesives are used on non-planar substrates, then the bonding process is simple, but adhesive waste increases due to poor conformability
Solution Approach 1:
The adhesive composition exhibits dynamic rheological properties that allow it to flow and conform to complex substrate geometries during application, then stabilize once bonded, reducing waste on non-planar surfaces without requiring complex dispensing equipment
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
This method enables strong, reliable bonding to low-surface-energy and porous substrates without the need for primers, reducing adhesive waste and improving bond strength on non-planar surfaces, such as those with recessed features or ribs.
Implementation Method 1
heating a styrenic block copolymer composition to provide an adhesive melt composition
Implementation Method 2
cooling the adhesive melt composition to obtain a bonded pressure-sensitive adhesive
Data Source
AI summary
Methods of bonding a pressure-sensitive adhesive to a substrate are provided. The methods include heating a styrenic block copolymer composition to provide an adhesive melt composition, wherein the styrenic block copolymer composition contains a hard segment block with a glass transition temperature of from 90° C. to 220° C.; masticating the adhesive melt composition; delivering the adhesive melt composition onto the substrate at a temperature that exceeds the glass transition temperature of the hard segment block by from 20° C. to 150° C.; and cooling the adhesive melt composition to obtain a bonded pressure-sensitive adhesive. Optionally, the substrate can be a non-film substrate, or the styrenic block copolymer composition can be provided in a core-sheath filament that includes a styrenic block copolymer core and a sheath that is non-tacky at ambient temperature.