Appearance Transparent to pale yellow; no visible agglomerates
Stability Shelf‑life: 24 months at 4 °C – 25 °C (ambient). No significant change in particle size or concentration.
Packaging Sealed amber glass vial, screw cap; each vial labeled with lot number and expiry date.
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2. Storage & Handling
Condition Recommended Action Notes
Temperature Store at 4 °C – 25 °C (ambient). Avoid freezing or heating above 30 °C. Freezing may cause ice crystal growth that alters particle size; heating can agglomerate particles.
Light Exposure Keep vial in the dark or wrapped in foil to protect from UV radiation. UV can degrade polymer chains, affecting dispersion stability.
Mixing / Dispersion Gently swirl before use; avoid vigorous shaking which may introduce air bubbles. Bubbles may lead to inconsistent readings if used for optical measurements.
Storage Duration Use within 6 months of preparation for optimal stability. Over time, polymer chains can undergo chain scission or crosslinking affecting viscosity.
Handling Wear gloves; avoid contamination with oils or other solvents. Contaminants may alter surface tension and interfacial behavior.
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4. "What‑If" Analyses: Parameter Variations
4.1 Increasing Concentration of Polyvinyl Alcohol (PVA)
Hypothesis: Raising PVA concentration from 0.01 wt% to 0.05–0.1 wt% will increase the bulk viscosity and surface tension, potentially leading to a larger contact angle (more non‑wetting behavior) on PDMS or PS.
Predicted Effects:
- Higher viscosity may reduce spreading velocity but could also damp oscillations in droplet impact dynamics. - Increased interfacial tension may elevate the receding contact angle, altering wetting hysteresis.
Experimental Plan: Prepare a series of PVA solutions at 0.01, 0.05, and 0.1 wt% (keeping surfactant concentration constant). Measure contact angles on PDMS/PS surfaces. Perform droplet impact tests to observe changes in splash formation.
2. Substituting Surfactants
a) Replace Tween-20 with SDS (anionic surfactant)
Predicted Impact:
SDS has a lower critical micelle concentration (~8 mM) and stronger surface activity than Tween-20, potentially reducing interfacial tension more effectively.
The use of an ionic surfactant may alter the stability of emulsions: SDS can increase electrostatic repulsion between droplets, possibly leading to better dispersion but also potential interactions with charged surfaces (e.g., silica).
In droplet impact experiments, lower surface tension could reduce splash thresholds, promoting finer atomization.
Experimental Design:
Prepare aqueous solutions of SDS at concentrations 0.5× and 1× CMC (~4 mM and ~8 mM).
Mix with oil phase (same as before) under identical conditions.
Measure interfacial tension via pendant drop method.
Lower surface tension values relative to CTAB/CTAC mixtures (~25–30 mN/m).
Enhanced atomization; more secondary droplets; higher splashing intensity at given velocities.
6. Conclusions
The comparative study of CTAB, CTAC, and C12E8 surfactants in forming stable oil-in-water emulsions reveals that:
Charge Density: High ionic strength (CTAB/CTAC) provides stronger electrostatic repulsion between droplets than low ionic strength (C12E8), leading to superior stability.
Hydrophilic–Lipophilic Balance: C12E8’s high HLB (>15) may over-stabilize the oil–water interface, reducing droplet mobility and thereby lowering splashing propensity in air–droplet interactions.
Droplet Mobility: Surfactants that allow greater droplet movement (CTAB/AC) increase the likelihood of collision-induced coalescence upon impact with surfaces or other droplets.
The proposed experimental plan will systematically test these hypotheses by measuring droplet stability, mobility, and splashing behavior across surfactant types and concentrations. The outcomes will inform the design of microfluidic systems where controlled droplet–surface interactions are critical (e.g., in inkjet printing, lab‑on‑a‑chip devices, or aerosol deposition).
