Microfibrillated Lignocellulose Foam Structure Without Toxic Binders
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Solution Overview
Problem
Current building thermal insulation materials rely heavily on carbon-intensive, nonrenewable resources and pose health hazards, and existing lignocellulose-based foams lack mechanical robustness and scalability due to insufficient fiber interaction and the use of toxic chemical binders.
Innovation Solution
A method involving microfibrillated lignocellulose foams prepared using a surfactant like sodium dodecyl sulfate and air drying, with optional hydrophobic palm wax coating and fire retardants like kaolinite, to enhance structural integrity and scalability without chemical binders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If chemical binders (MDI, citric acid, borates) and crosslinkers (polyacrylamide, polyamidoamine epichlorohydrin) are used to strengthen the foam structure, then mechanical properties improve, but sustainability decreases and handling difficulty increases due to toxicity and poor water solubility
Solution Approach 1:
The lignocellulosic fibers themselves serve as the binding agent through enhanced physical entanglement and hydrogen bonding, eliminating the need for external chemical binders. The microfibrillated structure provides intrinsic binding capability through increased surface area and functional groups, allowing the material to strengthen itself without toxic additives.
Solution Approach 2:
The patent changes the physical parameters of the lignocellulose by applying mechanical treatment to create microfibrillation, which increases fiber surface area, hydroxyl group density, and hydrogen bonding capacity. This parameter change enables the fibers to self-bind effectively without chemical additives, resolving the contradiction between strength and sustainability.
2Productivity
If conventional lignocellulose foams are prepared using bubble templating/air drying, then production efficiency and scalability improve, but mechanical properties deteriorate due to insufficient fiber interaction
Solution Approach 1:
The patent applies mechanical treatment to the lignocellulose fibers before foam formation to pre-create the microfibrillated structure. This preliminary action enhances fiber interaction capability, ensuring that when the foam is formed through efficient bubble templating and air drying, the fibers are already prepared to interact strongly, thus maintaining both productivity and mechanical properties.
Solution Approach 2:
The patent creates a composite structure where microfibrillated lignocellulose fibers are densely entangled within the foam matrix. This composite approach combines the processing efficiency of conventional foam formation with enhanced mechanical properties through the microfibrillated fiber network, achieving both high productivity and strong structural integrity.
3Strength
If nanoscale cellulose (cellulose nanofibrils) is used to increase viscosity and suppress bubble collapse, then mechanical properties improve, but production cost and energy intensity increase due to expensive chemicals and energy-intensive mechanical processes
Solution Approach 1:
Instead of using expensive cellulose nanofibrils, the patent employs conventional lignocellulose fibers that are mechanically treated to create a microfibrillated structure. This approach uses readily available, low-cost biomass materials that can be processed with simpler, less energy-intensive equipment, achieving similar binding effects without the high cost and energy intensity of CNF production.
Solution Approach 2:
The patent achieves the desired fiber interaction and binding effects by changing the physical parameters of conventional lignocellulose through mechanical fibrillation, rather than using nanoscale materials. This parameter change (creating microfibrils from conventional fibers) provides sufficient viscosity and binding capability without the need for energy-intensive nanofiber production processes.
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 method produces mechanically robust, scalable, and sustainable thermal insulation foams with improved mechanical properties and fire resistance, reducing reliance on nonrenewable resources and minimizing health risks.
Implementation Method 1
a foaming agent like TweenTM-80 (Pöhler et al., 2017) or sodium dodecyl sulfate (SDS: Lohtander et al., 2022) can be used to hamper structure aging due to bubble collapse or coalescence
Implementation Method 2
This structure has been identified to restrict heat transfer, as the solid heat conduction and gas heat convection are hampered by the low solid fraction and structural tortuosity
Implementation Method 3
The ongoing water removal from the wet foam due to drainage and air drying drives the lignocellulosic fibers to aggregate and gradually assemble into porous, interconnected foam
Data Source
AI summary
The present disclosure includes lignocellulosic foams which may be used, for example, in insulation as well as methods for their preparation. For example, the methods of preparing a foam may comprise: foaming an aqueous suspension comprising microfibrillated lignocellulose and a foaming agent to obtain a wet foam; and drying the wet foam to obtain the foam.