Polymer Substrate Surface Modification Using Densified CO2
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Solution Overview
Problem
Existing methods for modifying polymer substrates, such as catheter tubing, often require organic solvents and cumbersome techniques, which can lead to residual solvent issues and unintended migration of surface modifying agents, limiting their effectiveness and biocompatibility.
Innovation Solution
Exposing the polymer substrates to densified CO2 under controlled subcritical and supercritical conditions to impregnate them with silicone and fluorine-containing surface modifying agents, which reduces surface tension and enhances lubricity and biocompatibility without using organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic solvents are used to impregnate surface modifying agents into polymer substrates, then the surface tension is reduced and lubricity is enhanced, but residual solvent remains in the product and organic solvents may cause unintended migration of surface modifying agents
Solution Approach 1:
The patent changes the physical state parameters of the fluid from conventional liquid or gaseous state to supercritical state (temperature and pressure above critical point). This parameter change allows CO2 to achieve liquid-like solvation power while maintaining gas-like mass transfer properties, enabling effective impregnation of surface modifying agents without leaving residual solvent in the final product.
Solution Approach 2:
The patent utilizes the phase transition properties of CO2 between subcritical, supercritical, and gaseous states. By controlling temperature and pressure, CO2 transitions to a supercritical state for impregnation, then returns to gaseous state for easy removal, leaving no residual solvent. This phase transition mechanism solves the residual solvent problem while maintaining effective surface modification.
2Object-generated harmful factors
If densified CO2 is used as a solvent for impregnation, then residual solvent concerns are eliminated and mass transfer is improved, but the process requires controlled temperature and pressure conditions
Solution Approach 1:
The patent uses CO2 as a disposable solvent that can be easily introduced and removed from the system. CO2 is inexpensive, environmentally benign, and can be rapidly expanded from supercritical to gaseous state for complete removal from the product. This approach eliminates residual solvent concerns while the simplicity of CO2 handling offsets the added temperature and pressure control requirements.
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 effectively increases the contact angle of water droplets on the substrate surface, reducing surface tension and thrombogenicity, while minimizing agent migration and residual solvent concerns, making it suitable for medical applications.
Implementation Method 1
Due to their liquid-like solvation power and gas-like mass transfer properties, these fluids are unique solvents for uses such as synthesis, extraction and separation
Implementation Method 2
the polymer is modified by incorporation of an agent capable of enhancing the surface properties of the polymer into the polymer matrix of the polymer substrate, including at least those portions of the polymer matrix that bound the surface of the substrate
Implementation Method 3
The surface modifying agent is a silicone and/or fluorine-containing compound and serves to reduce the surface tension of a surface of the substrate, by causing a significant increase in the contact angle of a water droplet received on the surface
Data Source
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AI summary
Described are methods for modifying the surface properties of a polymer substrate by exposing the substrate to a densified fluid and a surface modifying agent. The densified fluid may be densified carbon dioxide and the surface modifying agent may be one which reduces the surface tension of the polymer substrate, for example as incorporated into a medical device such as a catheter.