Dibenzocyclooctane Thermosets for Zero CTE
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Solution Overview
Problem
Bulk polymers exhibit high positive coefficients of thermal expansion, leading to issues like cracking and delamination due to CTE mismatch with underlying components, and existing solutions using fillers introduce brittleness or stiffness, necessitating the development of filler-less thermosets with tunable CTE near zero ppm/°C.
Innovation Solution
The synthesis of divinyl- and diepoxy-substituted dibenzocyclooctanes, which are incorporated into thermosetting resins to manipulate the coefficient of thermal expansion through thermally contractile units, specifically the dibenzocyclooctane (DBCO) moiety, allowing for reversible twist-boat to chair isomerization and net contraction upon heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fillers such as mica or alumina are added to reduce CTE, then the CTE value decreases, but the material becomes brittle or stiff
Solution Approach 1:
The invention extracts and eliminates the filler components from the polymer system while retaining the desired low CTE property through molecular design of the polymer backbone itself, specifically using rigid aromatic structures that inherently provide thermal expansion control without requiring particulate fillers
Solution Approach 2:
The invention changes the fundamental parameter of the polymer structure by incorporating rigid aromatic moieties and specific crosslinking densities to achieve low CTE values through the polymer's intrinsic molecular architecture rather than through additive fillers, thereby avoiding the brittleness associated with filled systems
2Ease of manufacture
If bulk polymers are used, then the material is easy to manufacture, but the CTE is high leading to cracking and delamination
Solution Approach 1:
The invention modifies the polymer's molecular parameters by incorporating rigid aromatic structures and optimizing crosslinking density to achieve low CTE values, thereby resolving the thermal expansion issues that lead to cracking and delamination while maintaining the ease of manufacture through direct polymer synthesis rather than filler incorporation
Solution Approach 2:
The invention creates a composite-like structure at the molecular level by combining rigid aromatic moieties with flexible aliphatic segments in the polymer backbone, achieving a balanced material that provides both low CTE and manufacturing ease without requiring physical fillers
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 approach effectively reduces the coefficient of thermal expansion to near zero ppm/°C, providing a reversible and tunable thermal expansion behavior in thermoset materials without the need for fillers, thus mitigating cracking and delamination issues while maintaining material integrity.
Implementation Method 1
thermally contractile units, specifically the dibenzocyclooctane (DBCO) moiety, allowing for reversible twist-boat to chair isomerization and net contraction upon heating
Data Source
AI summary
The invention describes a method to synthesize a divinyl- and diepoxy-substituted dibenzocyclooctanes, thereby providing a curative that can undergo a twist-boat to chair isomerization at elevated temperatures. The synthetic approach can be applied to a variety of thermosetting resins that can be crosslinked with the curative to form a polymer having a tunable coefficient of thermal expansion.