Thermally Expandable Foam Activator for Low Temperature Cure
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Solution Overview
Problem
Current thermally expandable compositions used in automotive manufacturing do not achieve stable foam formation and adhesion at ultra-low temperatures below 150°C, leading to poor performance at higher temperatures and limited expansion stability across a wide temperature range.
Innovation Solution
A thermally expandable composition comprising a cross-linkable polymer, peroxide, antioxidant, and chemical blowing agent, with an activator containing urea or urea derivatives, which enables uniform expansion and stable foam formation between 120°C and 200°C, particularly at ultra-low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermally expandable compositions are used, then stable foam formation occurs at high temperatures (180°C), but expansion stability and adhesion performance deteriorate at ultra-low temperatures (below 150°C)
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating specific urea derivatives (such as N,N-dimethylurea, N,N,N′,N′-tetramethylurea) as activators in controlled amounts (0.1-10 wt%, preferably 1-9 wt%). This parameter change enables the blowing agent to decompose and release gas at lower temperatures (120-150°C), achieving stable foam formation across an expanded temperature range while maintaining adhesion properties
Solution Approach 2:
The patent creates a composite material system combining cross-linkable polymers (ethylene-vinyl acetate, ethylene-methacrylate, or ethylene-acrylate copolymers), peroxide initiators, antioxidants, chemical blowing agents, and urea derivative activators. This composite formulation synergistically enables both low-temperature foam stability and high-temperature performance, resolving the temperature range adaptability contradiction
2Speed
If the blowing agent decomposes too fast at high temperatures, then volume expansion occurs rapidly, but foam stability deteriorates and small-cellular foam structure cannot be produced
Solution Approach 1:
The patent implements a two-stage decomposition process through periodic action: first, the peroxide initiator decomposes to generate radicals that initiate polymer cross-linking; subsequently, the chemical blowing agent decomposes to release gas for foam formation. This staged, periodic decomposition sequence controls the expansion speed and ensures foam stability by preventing premature or uncontrolled gas release
Solution Approach 2:
The peroxide initiator acts as an intermediary that mediates between the polymer matrix and the blowing agent. It first activates the polymer for cross-linking, creating a stable network structure, and then enables controlled blowing agent decomposition. This intermediary action ensures that gas release occurs at the appropriate time and rate, maintaining foam stability while achieving desired expansion
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 achieves controlled, uniform expansion and stable foam formation with excellent adhesion properties across a broad temperature range, including ultra-low temperatures, enhancing the sealing and reinforcement capabilities in automotive applications.
Implementation Method 1
polymers that can be cross-linked by peroxides, such as ethylene-vinyl acetate polymers
Implementation Method 2
Under activation conditions, such as elevated temperature, curing of the cross-linkable network takes place
Implementation Method 3
the blowing agent decomposes and releases gases. This leads to the above mentioned volume expansion and the formation of a stable foam
Implementation Method 4
expand its volume when heat or another physical or chemical form of energy is applied
Implementation Method 5
an activator A, wherein said activator A comprises at least one compound selected from formula (I)... enables uniform expansion and stable foam formation between 120°C and 200°C
Data Source
AI summary
A thermally expandable composition, including at least one polymer, cross-linkable by peroxide, at least one peroxide, preferably at least one antioxidant, at least one chemical blowing agent, and at least one activator, wherein the activator includes at least one compound selected from formula (I),wherein radicals R1 and R4 represent hydrogen atoms or monovalent alkyl radicals with 1 to 10 carbon atoms which optionally include oxygen atoms; R2 and R3 represent hydrogen atoms or monovalent alkyl radicals with 1 to 10 carbon atoms which optionally include oxygen atoms, nitrogen atoms, and/or aromatic moieties or R2 and R3 together form a divalent alkyl radical with 1 to 10 carbon atoms which optionally includes oxygen atoms, nitrogen atoms or aromatic moieties. The composition shows excellent properties in terms of expansion stability over a wide temperature range, can be expanded at temperatures below 150° C. and is suitable for baffle and/or reinforcement elements.