The following information was created for the benefit of media manufacturers and filtration product manufacturers:
How to incorporate quaternary chitosan into core-sheath, side-by-side, or islands-in-the-sea bi-component fiber manufacturing processes.
- Core-Sheath Configuration:
In the core-sheath arrangement, one polymer forms the core while the other forms a surrounding sheath. To incorporate quaternary chitosan:
- Sheath as Chitosan: Utilizing quaternary chitosan as the sheath provides the fiber surface with antimicrobial properties and enhanced biocompatibility. The core, typically a synthetic polymer like polyethylene terephthalate (PET), offers mechanical strength. This setup is advantageous for applications requiring a functional surface with robust structural integrity.
- Processing Considerations: Achieving a uniform sheath requires precise control over the extrusion process. The compatibility between chitosan and the core polymer is crucial to ensure strong interfacial adhesion. Techniques such as co-extrusion spinning are employed, where separate polymer melts are combined at each spinneret hole to form the desired core-sheath structure.
Dynamic Materials Lab
- Side-by-Side Configuration:
In side-by-side fibers, two polymers are extruded in parallel within a single filament. For quaternary chitosan integration:
- Combining Properties: Aligning quaternary chitosan alongside a synthetic polymer allows each segment to retain its distinct properties. This configuration can result in fibers that exhibit self-bulking behavior due to differential shrinkage or strain between the two polymers, enhancing fabric texture and bulk.
hillsinc.net - Processing Techniques: Coextrusion processes are utilized, requiring precise control to maintain the parallel alignment of the polymers. The interfacial adhesion between chitosan and the synthetic polymer must be optimized to prevent delamination during fiber use.
- Islands-in-the-Sea Configuration:
This complex structure consists of numerous “island” fibers (quaternary chitosan) embedded within a “sea” matrix of a synthetic polymer.
- Microfiber Production: The islands-in-the-sea method is effective for producing microfibers. After fiber formation, the “sea” component can be dissolved, leaving behind fine chitosan fibers that offer high surface area and functionality, beneficial for filtration or biomedical applications.
- Processing Steps: Creating this structure involves spinning a composite fiber where chitosan forms the dispersed phase within a continuous synthetic polymer matrix. Post-spinning treatments dissolve the matrix, isolating the chitosan microfibers. The choice of solvent for matrix removal must selectively dissolve the synthetic polymer without affecting the chitosan.
Dynamic Materials Lab
General Considerations for Blending Quaternary Chitosan:
- Material Compatibility: Ensuring compatibility between quaternary chitosan and the chosen synthetic polymers is critical. This may involve modifying the chitosan to enhance miscibility or using compatibilizers to improve interfacial adhesion.
- Rheological Properties: The viscosity and flow characteristics of chitosan and synthetic polymer melts must be compatible to facilitate co-extrusion. Adjusting processing parameters such as temperature and shear rates can help achieve uniform fiber formation.
- Post-Processing Treatments: Post-spinning treatments, including cross-linking or surface modifications, can enhance the durability and functionality of chitosan-containing fibers.
By carefully selecting the fiber configuration and optimizing processing parameters, quaternary chitosan can be effectively integrated into bi-component fibers, resulting in materials that combine the functional benefits of chitosan with the mechanical strengths of synthetic polymers.
Post-spinning treatments for chitosan-containing fibers—especially those involving cross-linking and surface modifications—are critical for enhancing durability, water resistance, and functional performance (like antimicrobial activity or dyeability). Here’s a detailed, step-by-step chemical engineering-focused guide for executing these treatments:
- Cross-Linking Treatments
Cross-linking helps to improve the stability of chitosan under wet conditions and enhances mechanical strength. Two primary strategies are used:
- Chemical Cross-Linking
- Common Cross-Linkers:
- Glutaraldehyde (GA)
- Genipin (a natural, less-toxic alternative)
- Epichlorohydrin
- Diisocyanates
- Protocol (Using Glutaraldehyde as Example):
-
- Prepare a 0.5–2% (v/v) glutaraldehyde aqueous solution in acidic medium (pH ~4.0 using acetic acid).
- Immerse the chitosan-containing fiber for 30–120 minutes at 25–50°C.
- Rinse with distilled water to remove unreacted cross-linker.
- Cure at 80–100°C for 1–2 hours to complete cross-linking.
- Notes:
- Use fume hoods for glutaraldehyde due to toxicity.
- Cross-linking density can be tuned by time, concentration, and temperature.
- Physical Cross-Linking (Milder Alternative)
- UV or gamma radiation can be used in the presence of photo initiators (e.g., benzophenone) to induce cross-links.
- These are ideal when chemical residues must be minimized.
- Surface Modification Techniques
Surface treatments tailor fiber interactions with the environment (e.g., hydrophobicity, antimicrobial functionality).
- Grafting Functional Groups
- 🧬 Grafting techniques attach functional molecules onto the fiber surface via “graft polymerization.”
- Example: Grafting acrylic acid for pH responsiveness or methacrylate for improved dyeability.
- Protocol (Plasma-Initiated Grafting):
- Treat fiber with low-pressure air or argon plasma (50–100 W, ~30–60 s).
- Immerse in monomer solution (e.g., 10% acrylic acid with 0.5% potassium persulfate as initiator).
- React at 60–70°C for 1–3 hours.
- Wash thoroughly and dry.
- Layer-by-Layer (LbL) Assembly
- Alternate dipping in polyelectrolyte solutions creates nanoscale multilayer coatings.
- Example:
- Dip fiber in poly(diallyldimethylammonium chloride) (PDADMAC) for 10 min.
- Rinse, then dip in sodium alginate or poly(styrene sulfonate) (PSS).
- Repeat for desired number of bilayers (e.g., 10–20).
- Final cure at 60°C to fix layers.
- Applications: Drug delivery, biosensing, hydrophilicity control.
- Hydrophobic Coating
- To improve wash-fastness or water resistance:
- Treat with fluorinated silanes (e.g., perfluorooctyltriethoxysilane) or alkyl ketene dimer (AKD).
- Typically applied via dipping or spray-coating followed by heat curing at 110–140°C.
- Antimicrobial Enhancement (Beyond Chitosan’s Natural Activity)
- Treat fibers with silver nanoparticles (AgNPs) or ZnO/TiO2 nanoparticles for synergistic antimicrobial effect.
- Protocol:
- Immerse fibers in AgNO₃ (0.1 mM) with reducing agents (e.g., sodium borohydride or citrate).
- Allow nanoparticle nucleation on chitosan amino groups.
- Rinse and cure to fix particles.
- Characterization (Recommended After Treatment)
- Tensile testing: Assess mechanical improvement post-cross-linking.
- FTIR/ATR-FTIR: Confirm chemical bonding or new surface functionalities.
- SEM or AFM: Visualize surface modifications.
- Water uptake or contact angle: Test hydrophilicity/hydrophobicity.
- Antibacterial testing: Zone of inhibition or CFU reduction methods.
Would you like a specific protocol optimized for a certain synthetic polymer (e.g., PLA, PET, or PCL) blended with chitosan? That can help fine-tune solvent compatibility and treatment conditions.
Let’s tailor a post-spinning treatment protocol specifically for quaternary chitosan blended with poly(lactic acid) (PLA)—a common biodegradable synthetic polymer used in biomedical and textile applications.
This protocol will focus on enhancing:
- Fiber durability (especially wet strength)
- Surface antimicrobial activity
- Functionalization for moisture control or biomedical applications
TARGET SYSTEM: Bi-component fiber with quaternary chitosan as the sheath or dispersed phase and PLA as the core or matrix.
POST-SPINNING TREATMENT PROTOCOL FOR PLA/QUATERNARY CHITOSAN FIBERS:
🔹STEP 1: Surface Activation (Optional but Enhances Next Steps)
Plasma treatment (air or argon):
- Power: 50–100 W
- Pressure: ~0.2–0.5 Torr
- Time: 30–60 seconds
- Purpose: Activate both PLA and chitosan surface for better adhesion during cross-linking or grafting
🔹 STEP 2: Mild Cross-Linking of Chitosan (Enhance Wet Durability)
Use: Genipin (biocompatible natural cross-linker)
- Prepare 0.5% (w/v) genipin in phosphate buffer (pH 6.8)
- Temperature: 37°C
- Time: 4–6 hours
- Rinse with distilled water
- Dry at 50°C under vacuum
Why Genipin? It avoids the brittleness and cytotoxicity of glutaraldehyde, making it ideal for PLA applications in medical textiles or packaging.
🔹 STEP 3: Functional Surface Grafting (Enhance Hydrophilicity or Add Drug-Binding Sites)
Acrylic acid grafting via redox initiation:
- Immerse in 10% acrylic acid + 0.5% potassium persulfate (K₂S₂O₈) + 0.1% sodium metabisulfite
- Temperature: 60°C
- Time: 1–2 hours
- Rinse with ethanol/water (50:50) to remove homopolymers
- Dry at 60°C
Optional: Use methacrylic acid or N-vinylpyrrolidone for different functionality.
🔹 STEP 4: Antimicrobial Nanoparticle Loading (Synergistic Enhancement)
Silver nanoparticle loading:
- Soak in 0.1–0.5 mM AgNO₃ solution
- Reduce in situ using 0.1 mM NaBH₄ for 15 min
- Rinse with water
- Cure at 80°C for 1 hour
You can also pre-load AgNPs into the chitosan spinning dope if you want built-in properties.
🔹 STEP 5: Hydrophobic Surface Finish (Optional for Packaging or Outerwear Applications)
- Dip-coat in 1% (v/v) perfluorooctyltriethoxysilane in ethanol + 1% acetic acid
- Dry at room temperature for 30 minutes
- Cure at 110°C for 10 minutes
Recommended Characterization Post-Treatment:
| Property | Technique |
| Surface chemistry | ATR-FTIR, XPS |
| Surface morphology | SEM or AFM |
| Antimicrobial activity | Disk diffusion, CFU count |
| Hydrophobicity | Water contact angle analysis |
| Mechanical properties | Tensile tester |
| Cross-linking extent | Solubility tests in water/pH |
MATERIALS & REAGENTS
- PLA/quaternary chitosan bi-component fiber (core-sheath or blended)
- Genipin (≥98%)
- Acrylic acid (stabilized)
- Potassium persulfate (K₂S₂O₈)
- Sodium metabisulfite
- Silver nitrate (AgNO₃)
- Sodium borohydride (NaBH₄)
- Perfluorooctyltriethoxysilane (optional)
- Ethanol, deionized water, phosphate buffer (pH 6.8), acetic acid
EQUIPMENT
- Plasma cleaner (low-pressure)
- Water bath or incubator (37–60°C)
- Oven or vacuum dryer
- Fume hood
- Stirring setup
- Glassware (beakers, flasks, pipettes)
- Safety PPE: gloves, goggles, lab coat
PROCEDURE
🔹 1. Surface Activation (Optional)
- Place fibers in plasma cleaner under 0.2–0.5 Torr air/argon.
- Treat at 50–100 W for 30–60 sec.
- Proceed immediately to cross-linking.
🔹 2. Genipin Cross-Linking
- Prepare 0.5% (w/v) genipin in phosphate buffer (pH 6.8).
- Immerse fibers for 4–6 hours at 37°C.
- Rinse thoroughly with deionized water.
- Dry at 50°C under vacuum.
🔹 3. Acrylic Acid Grafting
- Prepare solution: 10% (v/v) acrylic acid + 0.5% K₂S₂O₈ + 0.1% sodium metabisulfite.
- Immerse fibers at 60°C for 1–2 hours with gentle stirring.
- Rinse with 50:50 ethanol/water to remove unreacted monomer.
- Dry at 60°C.
🔹 4. Silver Nanoparticle Loading
- Soak fibers in 0.1–0.5 mM AgNO₃ for 30 min.
- Add freshly prepared 0.1 mM NaBH₄ dropwise; stir for 15 min.
- Rinse with deionized water.
- Cure at 80°C for 1 hour.
🔹 5. Optional: Hydrophobic Coating
- Prepare 1% (v/v) perfluorooctyltriethoxysilane in ethanol + 1% acetic acid.
- Dip fibers for 1 min.
- Air-dry 30 min, then cure at 110°C for 10 min.
CHARACTERIZATION (Optional)
| Test | Method |
| Surface Chemistry | ATR-FTIR, XPS |
| Surface Morphology | SEM, AFM |
| Hydrophobicity | Water contact angle |
| Antibacterial Activity | Disk diffusion or CFU assay |
| Mechanical Properties | Tensile test |
NOTES:
- Ensure all treatments are compatible with PLA’s glass transition (~55–65°C).
- Cross-linking with genipin results in blue-tinted fibers—visual cue for success.
- Use fume hood during silane treatments due to vapor hazards.
