Superhydrophobic Wood Fiber Products

Yulin Deng and Hongta Yang

School of Chemical & Biomolecular EngineeringGeorgia Institute of Technology

Outline• Research Background and Project Objectives

• Experiments

• Results and Discussions- Nanostructured paper surface- Moisture Resistance- Water Resistance- Prevent Contaminations from Biomaterials

• Conclusions

• Future Work

Research Background

Current Treatments:• Sizing treatments

- Internal sizing treatment - Surface sizing treatment

• Barrier coating- Wax - Polymer

Problems of current hydrophobic coatings:• Too much polymer is used•Unrecyclable

Paper Product Properties:• Biodegradable• Recyclable• Low cost• Hydrophilic materials with high water and moisture absorption

What’s “Superhydrophobic” Surface ?

Hydrophilic Surface:

Hydrophobic Surface:

Superhydrophobic Surface:

Water Contact Angle < 90o

Water Contact Angle > 150o

(On a flat surface, no chemical has a water contact angle is greater than 125o)

Water Contact Angle > 90o (Contact angle of wax coated paper is ~115o)

Key Requirements:- Hydrophobic surface- Nanoscaled surface roughness

Superhydrophobic Papers:- Liquid/food packages.- Cup and food plates.- Self-cleaning clothes and paper boxes.- Substitution of wax and polymer coating paper products.

Superhydrophobic Concept

Lotus Effect: Water Contact Angle > 150o

Project Objectives

• Develop a method to control the roughness of paper surface.

• Chemically modify the surface from hydrophilic to hydrophobic.

• Prove the anti-contamination from biomaterials.

• Study the relationship between nano-surface roughness and the superhydrohpobic property

• Feasibility of different coating methods.

• Tetraethyl Orthosilicate (TEOS, 98%) Sigma-Aldrich

• Ammonium Hydroxide (NH4OH, 99.5%) Sigma-Aldrich

• Ethanol (99.5%) Sigma-Aldrich

• Poly(diallyldimethylammonium Chloride) (PolyDADMAC) Sigma-Aldrich

• 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (POTS) Deguessa

• Linerboard (Unbleached kraft softwood fiber)

Materials

Synthesis of Silica Particles

Stober Method:

Hydrolysis:

Alcohol Condensation (Alcoxolation):

Water Condensation(Oxolation):

Net Reaction:

Poly(DADMAC) Deionized Water Deionized WaterSilica Particles

A B

Repeat Step A & Step B for five times

Layer by Layer Deposition of PolyDADMAC/Silica

PolyDADMAC:

Silica Particles:SiO2

OH

OH

OHOH

OH

OH

OH

Remove C2H5OH

Sealed System at 125oC

POTS Vapor

POTSSilica-coated linerboard

Surface Modification

Chemical Vapor Deposition Using1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS )

Superhydrophobic Paper

Moisture Resistance

Weight of specimen - Weight of dry specimenMoisture content (%) = Weight of dry specimen

Sealed box

Pump

Pressure of water vapor Relative humidity (%) = x 100 % Saturation vapor pressure of water

0 10 20 30 40 50 60 70 80 90 1000

100

200

300

400

500

600

700

800

900

1000

Rel

ativ

e M

oist

ure

Con

tent

(%)

Relative Humidity (%)

UP HP SHP

0 10 20 30 40 50 60 70 80 90 1000

20

40

60

80

100

Rel

ativ

e Te

nsile

Stre

ngth

(%)

Relative Humidity (%)

UP HP SHP

0 10 20 30 40 50 60 70 800

2

4

6

8

140

160

180

0

2

4

6

8

140

160

180

Wat

er C

onta

ct A

ngle

(Deg

ree)

Moi

stur

e C

onte

nt (%

)

Immersing Time (Hours)

Paper Hydrophobicity after Immersing in Water

Superhydrophobic Linerboard

Water

Measure M.C. Measure W.C.A.

Theoretical Background

cos (cos 1) 1c Yfθ θ= ⋅ + −

cos SV SLY

LV

γ γθγ−

=

Cassie’s Law (Hydrophobic Rough Surface)

Young’s Equation (Hydrophobic/ Hydrophilic Flat Surface)

cθ

f : Solid Projected Area Fraction

aa

b

b

2

2

9afb

=

Projected Area Fraction ( )

Water Contact Angle: 155o

cos (cos 1) 1c Yfθ θ= ⋅ + −Cassie’s Law

155ocθ = 100o

Yθ =

0.11f =

f

Water Contact Angle: 110o

Cassie’s Law cos (cos 1) 1c Yfθ θ= ⋅ + −

110ocθ = 100o

Yθ =

0.82f =

Particle Size Effect

0 200 400 600 800 10000

30

60

90

120

150

180

Wat

er C

onta

ct A

ngle

(Deg

ree)

Average Silica Particle Size (nm)

a b

c d

a b c d

Bio-mimic of Lotus Leaf

Different Size Silica Multilayer

0 200 400 600 800 10000

30

60

90

120

150

180

Wat

er C

onta

ct A

ngle

(Deg

ree)

Smaller Silica Particle Size (nm)

United Size Silica Particles Different Sizes mixed with 1000nm of Silica Particles Different Sizes mixed with 800nm of Silica Particles

a b

c d200 nm + 1000 nm

c d

100nm + 1000 nm

400nm + 1000 nm 800nm + 1000 nmMix ratio of small/large particles = 1:5

Self-Cleaning Property

Normal Surface

Self-Cleaning Surface90 100 110 120 130 140 150 160 170 1800

20

40

60

80

Slid

ing

Ang

le (D

egre

e)

Water Contact Angle (Degree)

Sliding Angle = Advancing Angle – Reducing Angle

Anti-Contamination from Biomaterials

Original Linerboard

Superhydrophobic Linerboard

Hydrophobic Linerboard

Spray E-coli Solution on Linerboard Specimens

Offer an Inclining Angle of 5o Submerge in Water

Submerge in LB Broth Medium Respectively

Culture at 37oC for 24 Hours Respectively

Account the CFU of E-coli in the LB Broth Agar Medium Respectively

0

500

1000

1500

2000 With Offering a Inclining Angle With Immersing in Water

Bac

teria

Cul

ture

(CFU

)

Hydrophilic Linerboard Hydrophobic Linerboard Superhydrophobic Linerboard

Inclining Angle

Anti-Contamination from Biomaterials Performanceon Superhydrophobic Linerboard

0 20 40 60 80 1000

200

400

600

800

1000

1200

1400

Bac

teria

Cul

ture

(CFU

)

Inclining Angle (Degree)

Air Contamination

Micro-Scale Pores

0 2 4 6 8 10 12 14 16 18 200

30

60

90

120

150

180

Wat

er C

onta

ct A

ngle

(Deg

ree)

420 nm of Silica Content (wt.%)

Surface Spread Coating MethodLinerboard / Different Concentrations of Silica Solution (Spread Coating) / POTS

a b

c d

a b c d

Deionized WaterSilica Particles

0 2 4 6 8 100

30

60

90

120

150

180

Wat

er C

onta

ct A

ngle

(Deg

ree)

420 nm of Silica Content (wt.%)

Dip-coating Method

a b

c d

e f

Linerboard + (Silica Sol. With Starch)/ POTSSilica + Cationic Starch

Different Paper SubstratesDifferent Paper / Different Number of Layers (L-B-L Deposition) / POTS

0 1 2 3 4 5 6 7 80

30

60

90

120

150

180W

ater

Con

tact

Ang

le (D

egre

e)

Surface Coating with Different Amount of Layer

Linerboard Blotting Paper Copy Paper

Silica Content

0.36%5.1%

95%

Organic Compound 94.54% Moisture 5.1% Inorganic Ash 0.36%

9.8%

3.3%87%

Organic Compound 86.91% Moisture Content 3.3% Ash Content 9.79%

Linerboard / POTS

Water Contact Angle : 92o

Linerboard / Silica / POTS

Water Contact Angle : 153o

Silica (420nm) Added : 9.43 %

Linerboard / PolyDADMAC/ Silica / POTS

Water Contact Angle : 154o

Silica (420nm) Added : 3.99 %

4.4%3.1%

93%

Organic Compound 94.43 % Moisture 1.2 % Inorganic Ash 4.37 %

Directly Synthesizing Silica Particles on Linerboard

TEOS, Ethanol, NH4OH

Linerboard

Room TemperatureSummary:

Layer-By-Layer Deposition Method• W.C.A. > 150o

Spread-Coating Method• W.C.A. > 150o

• High amount of silica is needed

Dip-Coating Method• W.C.A. < 140o

• Silica aggregation

1. Superhydrophobic papers could be successfully prepared.

2. It can keep superhydrophobic by immersing in water for more than three days.

3. Superhydrophobic papers absorb less moisture than regular paper products.

4. Superhydrophobic papers can prevent the contamination from biomaterials.

5. Superhydrophobic property can be improved by increasing the roughness of surface.

Conclusion

Advantages and Future Improvements

• With high hydrophobicity.

• Less polymer used comparing with wax or polymer coated paper products, which is 30 to 50 μm.

• Potentially repulpable because the nanostructured surface can be destroyed by mechanical force.

• Can prevent contaminations from biomaterials.

Future Work

• Use clay/PCC to replace silica particles.

• Use ASA/AKD to replace POTS.

Thanks!

Questions?