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# Low Surface Energy PU Film With Small Contact Angle Hysteresis - PowerPoint PPT Presentation

Low Surface Energy PU Film With Small Contact Angle Hysteresis. Dou Qizheng 05-09-19. Beautiful lotus flowers. Water droplets. Self-cleaning. Surface roughness. Bar = 20 m. Introduction. lotus-effect. Barthlott, et al. Planta 1997 , 202 , 1.

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### Low Surface Energy PU Film With Small Contact Angle Hysteresis

Dou Qizheng

05-09-19

Beautiful lotus flowers Hysteresis

Water droplets

Self-cleaning

Surface roughness

Bar = 20 m

Introduction

lotus-effect

Barthlott, et al. Planta1997, 202, 1

Wenzel eq.

Cassie-Baxter eq.

: contact angle on a rough surface

0: contact angle on a projected ‘smooth’ surface

Surface roughnessenhances the hydrophobicity of hydrophobic surfaces

Self-Cleaning Properties

• Hydrophobic surface with low surface energy

• water contact angle,  > 90°

• Low roll-off angles ------ small contact angle hysteresis

Basic theory Hysteresis

• The force needed for a drop to move over a solid surface (F ):

F ~ LV (cos R– cos A)

LV is the surface tension of the liquid

• Contact angle hysteresis:

A–R or LV (cos R– cos A)

Fluorinated Polyurethane Films Hysteresis

• Water contact angle:

• Huge hysteresis: primarily due to the surface reorganization during the contact angle measurements.

LEIS (low-energy ion scattering)

First atomic layer, only F and C can be detected

• PDMS

• Hydrophobic

• High MW to limit surface reorganization

Experimental Hysteresis

• Preparation of low-surface energy films

• Polyurethane as polymer matrix

• Poly (dimethyl siloxane) (PDMS) will be used as a low-surface energy agent

Polymer Matrix: HysteresisSolventless Liquid Oligoesters (SLO) and N3600 (cross-linker)

Approach 1

PDMS + SLO + N3600 → PU film of low 

Approach 2

PDMS + N3600 → partially PDMS-modified N3600

SLO + N3600 + PDMS-N3600 → low  PU

(To increase the miscibility between PDMS and other components)

Bi-functional PDMS Hysteresis

(1) EFKA 3299

HO-(EO)n-OCH2CH2CH2-(Si(Me)2O)x-CH2CH2CH2O-(EO)n-OH

n ca. 10

x ca. 20

EO = ethylene oxide, PO = propylene oxide

(2) 481246

HO-CH2CH2-OCH2CH2-(Si(Me)2O)n-CH2CH2O-CH2CH2-OH

n=69

Mono-functional PDMS Hysteresis

Mono-hydroxyl terminated PDMS (480355):

n= 63

Surface wettability Hysteresis

PU film with bi-functional EFKA3299

Water CA and hysteresis of PU film containing EFKA 3299 and cured at room temperature by approach 1

Surface wettability Hysteresis

PU film with bi-functional 481246

PU film containing 481246 by approach 1

Surface wettability Hysteresis

PU film with bi-functional 481246

PU film containing 481246 by approach 1

Surface wettability Hysteresis

PU film with mono-functional 480355

PU film containing 480355 by approach 2

Surface wettability Hysteresis

PU film with mono-functional 480355

PU film containing 480355 by approach 2

Surface chemical composition Hysteresis

PU film with bi-functional 481246

PU film containing 481246 and cured at 80 oC

Surface chemical composition Hysteresis

PU film with mono-functional 480355

The chemical composition (Si%) of the PU films which were modified by different amount of 480355 and cured under different temperature.

Surface chemical composition Hysteresis

PU film with mono-functional 480355

The chemical composition (N%) of the PU films which were modified by different amount of 480355 and cured under different temperature.

Surface chemical composition Hysteresis

PU film with mono-functional 480355

The chemical composition (N% and Si%) in different depth of the PU films which were modified by0.07%wt (PDMS)63-OH and cured under 40 oC and 120 oC

Surface chemical composition Hysteresis

Compare the PU film with 480355 and 481246

The chemical composition (N% and Si%) in different depth of the PU films which were modified by0.07%wt (PDMS)63-OH or 0.08%wt (PDMS)69-(OH)2 and cured under 80 oC

Model Hysteresis

PU film containing EFKA 3299

PU film containing 480355

PU film containing 481246

Future plans Hysteresis

• 1. Increase the roughness of the surface by adding some nano-particles into the film as a additive to get a super-hydrophobic surface.

Future plans Hysteresis

• 2. Application of PDMS-modified PU films as anti-fouling coatings.

• Coatings containing toxic materials

• Non-toxic Systems

• Fouling-release coatings based on silicones

• Perform well initially

• Soft, poor durability, short use life

Acknowledgement Hysteresis

• Dr. W. Ming

• Prof. Wang

• Prof. Lemstra