Lignin-based rigid polyurethaneLignin based rigid polyurethane foam reinforced with cellulose

hi knanowhiskers

Yang Li and Arthur J. Ragauskas

School of Chemistry and BiochemistryInstitute of Paper Science and Technology

Georgia Institute of Technologyg gy

Explore the applicability of lignin in the preparation of PUObjective

Explore the applicability of lignin in the preparation of PUStudy the reinforcing effect of cellulose nanowhiskers (CNWs)

Environnmental issuesEnergy conservation

Economical utilization of waste lignin

Improve performanceof PU

OutlineOutline Introduction of major materials and techniques Oxypropylation of kraft lignin and foam formulation optimizationyp py g p Preparation of ethanol organosolv lignin-based rigid PU

nanocomposite foam Summary

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Summary

PolyurethanePolyurethane PU is any polymer consisting of a chain of organic units joined by

urethane links.urethane links. Rigid PU foam is a highly crosslinked polymer with a closed-cell

structure.

600

700Lower densityLow thermal conductivity

100

200

300

400

500Low thermal conductivityLow moisture permeability Low cost High dimensional stability

0

100

1 2 3 4

Boardstock Sandwich panels

Refrigerationappliances

Technical insulation

High dimensional stability Good adhesive properties

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Global market of main applications of rigid PU foam in 2000 (2.1 million tons)

Huntsman Polyurethane

Lignin structureLignin structure Three-dimensional amorphous polymer consisting of methoxylated

h l t tphenylpropane structures. 25-35 wt% in SW and 18-25 wt% in HW

OH

HOO

OH

OMe

OH

OHO

OMe

Lignin OHLignin

OHH3CO

P-coumaryl alcohol(Grasses)

HOHOOH OH

OMeO

HO

OHO

OMe

OHO

O

HO

OHH3CO

coniferyl alcohol(SW/HW/Grasses)

O O OMeMeO

HOOOHO OH

HO

MeOOMe

HO

sinapyl alcohol(HW/Grasses)

a small piece of SW lignin

OMe

OHOCH3

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Sjostrom, E. Wood Chemistry: Fundamentals and Applications. Orlando, Academic Press, (1981).Sarkanen, K.V., Ludwing, C.H. Lignin, Occurrence, Formation, Structure and Reactions. New York, Wiley (Interscience), (1971).

Eth l l t t tEthanol organosolv pretreatment

Biomass

2:1 (v/v) of benzene:ethanol for 48 hours

1 1 wt% H2SO4 65% ethanol

Extraction

1.1 wt% H2SO4, 65% ethanol, 7:1 v/w, 170 ºC, 60 minCooking with ethanol, water, and H2SO4

Solid fraction: Cellulose

Precipitate:Ethanol Organosolv

Water-soluble fraction:SugarsCellulose

Residual ligninResidual hemicellulose

Ethanol Organosolv Lignin (EOL)

SugarsDepolymerized ligninFurfural and HMF

5X. Pan et al., Ind. Eng. Chem. Res. 2007, 46, 2609-2617.

Cellulose structure

Polymer of β-(1-4)-glucan, DP of 300-15,000 ~41wt% in SW and 42-51 wt% in HW

Cellulose molecule

Inter- and intra-molecule hydrogen bonding

6D. Klemm, H.-P. Fink et al. Angew. Chem. Int. Ed. 2005, 44, 3358-3393.A.J. Ragauskas et al. Industial Biotechnology Spring 2006

C ll l hi k (CNW)Cellulose nanowhisker (CNW)

Sulfuric acid (64% w/w) hydrolysis 10 ml acid/g pulp at 45 oC for 45 minSulfuric acid (64%, w/w) hydrolysis, 10 ml acid/g pulp, at 45 C for 45 min

Dilute with 10 fold of water Centrifugation at 12,000 rpm for 3 times

SonicationDialysis against waterCentrifugation at 10000 rpm

150-200 nm × ~10 nmBending strength of ~10 GPaBending strength of ~10 GPaYoung’s Modulus of ~150 GPa

Kevlar 156 GPa, Aluminum 70 GPa, Glass fiber 76 GPa

7500 nm

S. Beck-Candanedo et al. Biomacromolecules 2005, 6, 1048-1054.

Lignin oxypropylation

St ti t i lStarting materials: Kraft lignin (used for optimization) EOL Propylene oxide (PO) Potassium hydroxide (KOH)

Reaction parameters: 20/80/5 [w/v/%(w/w)] of lignin/PO/KOH

Lignin Tset (ºC) Tmax (ºC)

Pmax(bar)

Time( ) ( )

kraft 150 285 17.5 ~9minEOL 160 285 22.5 ~10min

8C.A. Cateto et al. Ind. Eng. Chem. Res. 2009, 48, 2583-2589.

Characterization GPC & FT IRCharacterization- GPC & FT-IRPropylene oxide oligmers (PPO) was separated from lignin polyol by extracting the product three times with hot hexane under reflux.

Lignin PPO Mnbefore Mnafterg(wt%)

before

(g/mol)after

(g/mol)Kraft 46 ± 5 1008 1732

oxykraft

EOL 45 ± 4 1082 1760kraft

Increased stretching of aliphatic CH3, CH2, CH groupsIncreased stretching of C-OIncreased stretching of C O

Chain extension reaction occurred!

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Characterization 31P NMRCharacterization - 31P-NMRNHND NHND

Oxykraft OxyEOL

Ali h ti OH

Condensed phenolic OH

Guaiacyl phenolic OH

Condensed phenolic OH

Guaiacyl phenolic OH

Aliphatic OH Aliphatic OHcarboxylic OHcarboxylic OH

10A. Granata, D.S. Argyropoulos, J. Agric. Food Chem. 1995, 43, 1538-1544.M. Zawadzki, A. Ragauskas, Holzforschung 2001, 55, 283-285.

St ti t i l f f tiStarting materials for foam preparationHydroxyl index IOH is the weight of KOH in mg that will neutralize the

ti h d id bl f ti b t l ti ith 1 f l l

OH value IOH

acetic anhydride capable of reacting by acetylation with 1 g of polyol.

(mmol/g)Kraft lignin 5.62 351.2

k f 6 91 387 6

Dimethylcyclohexylamine (DMCHA)oxykraft 6.91 387.6

EOL 6.02 337.7oxyEOL 6 60 380 0

(DMCHA) Potassium octotate Silicon surfactant

oxyEOL 6.60 380.0

Mn Functionality IOH NCO

n-pentane

n y OH

Sucrose polyol 690 4.4 356 -Glycerol polyol 1008 3.0 246 -

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Polymeric MDI 340 2.7 - 31.1%

Formulation of kraft lignin based PU foamsFormulation of kraft lignin-based PU foams

Percentage Lignin Sucrose Glycerol Polymeric CreamPercentage (wt%)

Lignin polyol

Sucrose polyol

Glycerol polyol

Polymeric MDI *

Cream time

0 0.00 g 25.00 g 15.00 g 36.37 g 40 sControl10 2.50 g 22.50 g 15.00 g 36.66 g 38 s30 7.50 g 17.50 g 15.00 g 37.24 g 34 s

(no oxykraft)

60 15.00 g 10.00 g 15.00 g 36.07 g 26 s100 25.00 g 0.00 g 15.00 g 39.24 g 23 sONLY

k f 100* 40.00 g 0.00 g 0.00 g 42.20 g 17 s

* The molar ratio of NCO to OH was 1.2 Replace sucrose polyol by k ft t l t

oxykraft

DMCHA Potassium octotate surfactant Pentane

oxykraft at several percentages

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1.80 g 0.90 g 1.50 g 10.00 g

Preparation of kraft lignin based PU foamsPreparation of kraft lignin-based PU foams

Representative reactions happened during foaming

R-NH-CO

OR'+ R''-N=C=O R-N-C-O-R'

CO

O

AllophonateNH R''

p

PolyolsSurfactantCatalysts

Polymeric MDI

Pentane

Self-risingPolymerization Cure

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Morphology and densityMorphology and density

Oxykraft content 0% 10% 30% 60% 100% 100*%Cell size (μm ) 620

±30638 ±50

610 ±30

750 ±30

750 ±20

630±±30

D it (k / 3) 29 3 30 2 29 4 30 7 30 1 29 4Density (kg/m3) 29.3 30.2 29.4 30.7 30.1 29.4

With increasing oxykraft content: Cell size was kept 620-650 μm except at 60% &100% where cell size went up to 750 μm and foam shrinkage also occurred Densities were kept ~30 kg/m3 Densities were kept 30 kg/m

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0% 30% 60% TotalScale bar: 500 μm

Mechanical properties

0.20 0 % oxykraft10% k ft Oxykraft

contentStrength (MPa)

Modulus(MPa)

0 % 0 095±0 005 1 45±0 07

0.15

Pa

10 % oxykraft 30 % oxykraft 60 % oxykraft 100 % oxykraft

total oxykraft 0 % 0.095±0.005 1.45±0.0710 % 0.100±0.007 1.56±0.0530 % 0 112±0 006 1 58±0 05

0.10

Stre

ss, M

P total oxykraft

30 % 0.112±0.006 1.58±0.0560 % 0.101±0.004 1.13±0.01

100 % 0.085±0.009 1.11±0.03000

0.05

100 % 0.085±0.009 1.11±0.03100*% 0.137±0.009 3.41±0.390 5 10 15 20

0.00

Strain, %

Compressive stress strain curves

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Compressive stress strain curvesIncreased by 44% 135%

P ti f EOL b d it fPreparation of EOL-based nanocomposite foams

oxyEOL DMCHA P.cat Surfactant Pentane Polymeric MDI

Control foam (w/o CNWs)

40.00 g 1.80 g 0.90 g 1.50 g 10.00 g 41.59 g

Nanocomposite foamsNanocomposite foams 1 wt% CNWs by adding 8.89 ml whiskers suspension 5 wt% CNWs by adding 44.47 ml whiskers suspension(Concentration of whiskers suspension is 0.03935 g/ml)

Method:Method:CNWs were added by directly mixing oxyEOL with whiskers suspension followed by removal of water under very high vacuum

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Morphology and densityMorphology and density

Whiskers content 0 wt% 1 wt% 5 wt%Cell size (μm) 320±20 269±28 191±16Density (kg/m3) 33.6 37.1 62.3y ( g )

With increasing CNWs content: Cell size decreased and density were both increasedy

Control foam 1 wt% whiskers foam 5 wt% whiskers foam

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Control foam 1 wt% whiskers foam 5 wt% whiskers foamScale bar: 500 μm

Chemical structure FT IRChemical structure - FT-IR% NH

ssio

n, %

NH

O-CONC=O

Control foam

Tran

smis

CO-NH

NC O

1% whiskers foam

T

Aliphatic CH3, CH2, CH

5% whiskers foam

4000 3500 3000 2500 2000 1500 1000 5001

C-ONHOC=O5% whiskers foam

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Wave number, cm-1

Mechanical propertiesMechanical properties

CNW content 0 wt% 1 wt% 5 wt%Strength (MPa) 0.198±0.010 0.255±0.025 0.519±0.008Modulus (MPa) 4.07±0.24 5.35±0.19 12.82±0.14( )

0.6 0 % whiskers1 % whiskers

0.4

0.5

MPa

1 % whiskers 5 % whiskers Strength 162% , modulus 215%

0.2

0.3

Stre

ss, M

Strength 29% , modulus 31%

0 5 10 15 200.0

0.1

St i %

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Strain, %

Compressive stress strain curves

Thermal stability – DSC & TGA

Both Tg and Td values0 wt% 1 wt% 5 wt%

Tg (ºC) 89 104 104

Both Tg and Td valuesare increased!

16 % f li i b d PU fTd (ºC) 247 263 296

0 % whiskers

16 wt% for non-lignin based PU foam EOL-based foams would give a better fire

retardant property

ss

0 % whiskers 1 % whiskers5 % whiskers

0 % whiskers 1 % whiskers 5 % whiskers

ow

Wei

ght l

os 5 % whiskers

Hea

t Flo

21 wt% char28 % h

0 100 200 300 400 500 600 700Temperature oC

0 50 100 150 200T t oC

28 wt% char24 wt% char

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Temperature, oCTemperature, oC

DSC curves TGA curves

Summary

OxyEOL is a suitable alternative polyol to prepare rigid PU foam with a uniform cell size and low density along with reasonable mechanical strength and thermal properties.

The addition of cellulose nanowhiskers up to 5 wt% d ti ll i d th i d th ldramatically increased the compressive and thermal properties.

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I would like to acknowledgeI would like to acknowledge

Financial support from IPST fellowship programpp p p g

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