Low Viscosity Silicone Elastomer for 3D Printing via Segmentation
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Solution Overview
Problem
Current silicone elastomer compositions face challenges in achieving low viscosity for printable materials while maintaining desirable mechanical properties, as high elongation and toughness typically require high molecular weight polymers, leading to high uncured viscosities, and low molecular weight materials result in poor mechanical properties.
Innovation Solution
A composition comprising a linear organopolysiloxane with silicon-bonded ethylenically unsaturated groups, a linear organohydrogensiloxane, a cross-linker with different reactivity, and a hydrosilylation catalyst, allowing for controlled chain extension and cross-linking to achieve low viscosity in the uncured state with high mechanical properties in the cured state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight polymers are used to achieve high elongation and toughness, then mechanical properties are improved, but viscosity in the uncured state increases
Solution Approach 1:
The invention divides the polymer system into two distinct components: a low molecular weight organopolysiloxane (providing low viscosity) and a separate crosslinker component (providing mechanical properties). This segmentation allows each component to be optimized independently - the base polymer remains low viscosity for printability, while the crosslinker adds the necessary mechanical strength and elongation when combined.
Solution Approach 2:
The invention performs preliminary chain extension by incorporating ethylenically unsaturated groups into the low molecular weight organopolysiloxane before the final crosslinking step. This preliminary action prepares the polymer chains for subsequent crosslinking, ensuring that when the crosslinker is added, the network formation occurs efficiently to achieve the desired mechanical properties without requiring high initial molecular weight.
2Force
If low molecular weight materials are used to minimize viscosity, then printability is improved, but mechanical properties deteriorate
Solution Approach 1:
The crosslinker acts as an intermediary that bridges the gap between low molecular weight materials and high mechanical properties. The crosslinker contains multiple reactive silicon-bonded ethylenically unsaturated groups that form crosslinks between polymer chains, transforming the weak van der Waals interactions in low molecular weight materials into strong covalent bonds, thereby achieving high mechanical properties from low viscosity starting materials.
Solution Approach 2:
The invention creates a composite system combining low molecular weight organopolysiloxane with a specially designed crosslinker. This composite approach allows the base polymer to provide low viscosity and flow characteristics, while the crosslinker component provides the mechanical strength, elongation, and toughness typically associated with high molecular weight polymers.
3Strength
If high viscosity compositions are used to achieve good mechanical properties, then cured article properties are improved, but printability deteriorates
Solution Approach 1:
The invention creates a dynamic system where the viscosity and reactivity of the composition change during the printing and curing process. The low molecular weight organopolysiloxane with ethylenically unsaturated groups maintains low viscosity during printing for excellent printability, while the subsequent addition of crosslinker and curing process dynamically transforms the material into a high strength elastomer, achieving both good printability and mechanical properties.
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 solution enables the formation of silicone elastomers with low initial viscosity suitable for 3D printing while maintaining high elongation and toughness, similar to those from higher molecular weight polymers, by leveraging differential reactivity of unsaturated species in hydrosilylation reactions.
Implementation Method 1
a) a linear organopolysiloxane having at least two silicon-bonded ethylenically unsaturated groups per molecule; b) a linear organohydrogensiloxane having at least two silicon-bonded hydrogen atoms per molecule; c) at least one cross-linker; and d) a hydrosilylation catalyst
Data Source
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AI summary
A composition for forming a silicone elastomer is disclosed. The composition comprises: A) a linear organopolysiloxane having at least two silicon-bonded ethylenically unsaturated groups per molecule; B) a linear organohydrogensiloxane having at least two silicon-bonded hydrogen atoms per molecule; C) at least one cross-linker; and D) a hydrosilylation catalyst. The cross-linker C) is selected from the group consisting of: C1) an organopolysiloxane having at least three silicon-bonded ethylenically unsaturated groups per molecule; and C2) an organopolysiloxane having at least three silicon-bonded hydrogen atoms per molecule. At least one of the silicon-bonded ethylenically unsaturated groups of component C1) has a lower reactivity relative to the silicon-bonded ethylenically unsaturated groups of component A). Moreover, at least one of the silicon-bonded hydrogen atoms of component C2) has a lower reactivity relative to the silicon-bonded hydrogen atoms of component B). Methods of forming three-dimensional (3D) articles utilizing the compositions are also disclosed.