STRUCTURE-PROPERTY RELATIONSHIP IN VEGETABLE OIL-BASED POLYURETHANES

Zoran S. Petrović, Wei Zhang, Ivan Javni and Andrew Guo

Kansas Polymer Research Center, Pittsburg State University, Pittsburg, KS

IntroductionThermosetting resins derived from vegetable oils can be useful binders for composites, casting resins for electrical applications, compression molding compounds, foams and coatings. They will successfully compete with petrochemical resins on price and performance. In this work we will describe the properties of polyurethane resins obtained from polyols derived from soybean oil and different isocyanates.

Advantages of soy polyurethanes

High hidrophobicity-better water resistanceBetter thermo-oxidative stabilityBetter electrical propertiesRenewable resource- stable priceWill compete with more expensive epoxy resins

Soy PolyurethanespolyurethanePolyol + isocyanate

Soy Polyols by epoxidation or hydroformylation

Isocyanates: diisocyanates vs. triisocyanates; aliphatic vs. aromatic

STRUCTURE OF SOYBEAN OIL

-OOC(CH2)7CH=CHCH2CH=CHCH2CH=CHCH2CH3 linolenic - 9%-OOC(CH2)7CH=CHCH2CH=CH(CH2)4CH3 linoleic - 51%

-OOC(CH2)7CH=CH(CH2)7CH3 oleic - 25%

-OOC(CH2)16CH3 stearic - 15%

Average unsaturation = 4.6 (I.V. = 120-140)

O

O

O

O

O

O

POLYOL FORMATION FROM EPOXIDIZED OILS

Epoxidized soybean oil

CH CH

OHY

Soy polyol

(A). CH3OH

(B). HCl

CH CH

O

(C). HBr

(D). H2/Catalyst

where Y = −OCH3, −Cl, −Br, or −H

POLYOLS BY HYDROFORMYLATION (HF)

OO

OO

O

O

CH=O

CH=O

CH=O

CH=OHydroformylation

OO

OO

O

O

CO/H2, Rh/P

The polyaldehyde is then reduced to a polyol.

Designation and properties of polyols

Polyol ID Reagent Conversion Yield

Hydroxyl Number

Equiv. Weight

Function-ality

Polyol Mol. Weight, Mn

Physical state at

(%) (mg KOH/g) (g/Equiv.) R. T. Soy-H2 H2 89 212 265 3.5 938 grease

Soy-Met CH3OH 93 199 282 3.7 1053 liquid

Soy-HCl a HCl 94 197 285 3.8 1071 grease

Soy-HBr a HBr 100 182 308 4.1 1274 grease

Soy-HF H2/CO 92 223 251 4.0 1004 liquid

a - All values are calculated based on the analyzed Cl and Br contents and assuming that each halogen is accompanied by a hydroxy group.

Viscosity of polyols vs. temperature

4.0

5.0

6.0

7.0

8.0

9.0

10.0

2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4

1/T x 1000 (K-1)

Ln

( η)

Soy-HF-16 Soy-Met-21 Soy-HCl Soy-HBr Soy-H2

Viscosity-temperature curves for Soy polyols and PPO triol

0500

1000150020002500300035004000

0 20 40 60 80 100 120

Temperature, deg. C

Vis

cosi

ty, m

Pa.

s Soy BMW-206

Soy BMW 179

Arcol LHT-240

Formation of Polyurethane Networks by Reaction of Polyols with Isocyanates

OC(O) Heat or catalyst

Oil-based polyol Isocyanate

+ OCN NCO

OH

OH

OH OH

OC(O)

OC(O)

OC(O)

OC(O)

OC(O)

Crosslinked polyurethane

OH

OH

Stress-strain curves for PAPI/soy-based polyurethanes

0

10

20

30

40

50

0 1 2 3 4 5 6 7 8 9 1 0

S tra in (% )

Stre

ss (M

Pa)

S o y-H 2

S o y-H C l

S o y-M et

S o y-H B r

TGA curves of soy-polyurethanes in air

0

20

40

60

100

0 100 200 300 400 500 600

Temperature (°C)

TG

A W

eigh

t (%

)

Soy-H2

Soy-HCl

Soy-HBr

80 Soy-HCl

Soy-Met

Mechanical properties of soy-based polyurethanes

Sample ID Density g/cm3

DSC Glass transition

Tensile strength

Elongation at break

Young’s Modulus

(°C) (MPa) (%) (MPa) Soy-HBr PAPI 1.262 75 44 7.7 1102

Soy-HBr Isonate 1.270 68 40 7.3 955

Soy-HCl PAPI 1.152 77 48 7.5 1204

Soy-HCl Isonate 1.152 73 46 8.9 1190

Soy-Met PAPI 1.113 72 45 8.4 986

Soy-Met Isonate 1.152 70 46 9.0 979

Soy-H2 PAPI 1.093 31 19 29 383

Soy-H2 Isonate 1.090 34 16 15.4 362

Soy-HF-16 PAPI 1.094 45 33.31 12.0 785

Soy-HF-16 Isonate 1.094 44 30.78 11.7 770

Conclusions (1)

Soy-based polyols displayed decreasing density and viscosity in the following order: SoyHBr> Soy-HCl> Soy-met> SoyH2> Soy-HF.Soy-HF and Soy-Met are liquid at RT.The reactivity of the polyols increased in the reverse order.Two series of polyurethanes prepared with two isocyanates had similar properties.

Effect of NCO/OH molar ratio

Crosslinking density of polyurethanes networks can be varied by varying isocyanate/hydroxyl ratio.

This ratio is directly proportional to the crosslinking density if conversion is complete

Relationship between number of elastically active chains (crosslinking density) and NCO/OH molar ratio for the system - the polyol with OH# =203 mg KOH/g and MDI

0.00E+002.00E-04

4.00E-046.00E-04

8.00E-041.00E-03

1.20E-031.40E-03

0 0.2 0.4 0.6 0.8 1 1.2

NCO/OH molar ratio

EANC

, mol

/cm

3

Effect of NCO/OH molar ratio for the system polyol (OH#=203)/MDI on Tg measured by DSC ( ), TMA( ) and

DMA (+)

-20-10

010203040506070

0 0.2 0.4 0.6 0.8 1 1.2

NCO/OH molar ratio

Gla

ss tr

ansi

tion,

o C Tg = Tgo + k1/Mc= Tgo + k2(EANC)

Effect of NCO/OH ratio on density, tensile strength and elongation

0

50

100

150

200

250

0 0.2 0.4 0.6 0.8 1 1.2

NCO/OH molar ratio

Ten

sile

str

eng

th, M

Pa

or

elo

ng

atio

n, %

1.061.0651.071.0751.081.0851.091.0951.11.1051.11

den

sity

, g/c

m3

elongation

Tensile strength

Dependence of tensile strength on glass transition

05

101520253035404550

0 10 20 30 40 50 60 70

glass transition temperature, oC

Te

ns

ile

str

en

gth

, M

Pa

Effect of crosslinking density (OH number of polyols) on tensile strength and elongation of polyurethanes at RT

0

10

20

30

40

50

60

150 170 190 210 230 250

OH number, mg KOH/g

tens

ile s

treng

th, M

Pa

02040

6080100120

140160180

elon

gatio

n, %

Effect of isocyanates on properties of polyurethanes

Isocyanates: diisocyanates vs. triisocyanates; aliphatic vs. aromatic

Polyol: Soy-206-polyol, OH# = 206 mgKOH/g.

Isocyanates

Diisocyanates: Aromatic -MDI, TDI, Cycloaliphatic -RMDI, IPDI, Aliphatic - HDI

Triisocyanates: DESMODUR N100, N3300, RFE, CB 75N

TriisocyanatesDESMODUR N100: Aliphatic Polyisocyanate, Ew = 191. HDI based. Solvent free.DESMODUR N3300: Aliphatic Polyisocyanate, Ew - 195. HDI based. Solvent free.DESMODUR RFE: Tris(p-isocyanato-phenyl)-thiophosphate in ethyl acetate (27%). Ew = 583DESMODUR CB 75N: TDI based aromatic polyisocyanate in ethyl acetate (75%). Ew = 323

4 , 4 ’ - D i p h e n y l m e t h a n e d i i s o c y a n a t e , M D I ( D e s m o d u r M )

H 2C N C ONCO

2 , 4 : 2 , 6 - T o l u e n e d i i s o c y a n a t e , T D I 8 0 : 2 0 is o m e r m i x t u r e ( D e s m o d u r T D 8 0 )

CH 3N C O

N C O

CH 3N C ONCO

R M D I , h y d r o g e n a t e d M D I ( D e s m o d u r W )

H 2C N C ONCO

I s o p h o r o n e d i i s o c y a n t e I P D I ( D e s m o d u r I )

N C O

N C OH 2C

H e x a m e t h y l e n e d i i s o c y a n t e H D I ( D e s m o d u r H )

NCON C O

D e s m o d u r N - 1 0 0 a n d D e s m o d u r N - 3 3 0 0 t r i i s o c y a n a t e s d e r i v e d f o r m 1 , 6 -h e x a m e t h y l e n e d i i s o c y a n a t e .

N

H N

CO

N C O

H N

CON C O

N C O

D e s m o d u r R F - E i s a t r i s ( p - i s o c y a n a t o -p h e n y l ) - t h i o p h o s p h a t e .

N C O

N C O

N C O

O

O

O

PS

D e s m o d u r C B 7 5 N is a

t r i m e t h y l o l p r o p a n e

T D I b a s e d p r e p o l y m e r

CH 3

N C O

NC

CH 3

N C O

NC

CH 3

N C O

NC

OO

O

O

O

O

Density of polyurethanes

1.104 1.104

1.062 1.061 1.0661.082

1.096

1.272

1.186

0.95

1

1.05

1.1

1.15

1.2

1.25

1.3

De

nis

ty, g

/cm

3

MDI TDI RMDI IPDI HDI N100 N3300 RFE CB 75NIsocyanate

Ar-Dii CAl-Dii Al-Trii Ar-Trii

Al-Dii

Overlay of the E' curves

10

100

1000

10000

-100 -50 0 50 100 150

Temperature, 0C

Sto

rage

mod

ulus

E',

MP

a

HDI

N3300

N100

TDIIPDI

RMDI

MDI

RFI

CB75N

Overlay of the E" curves

0.01

0.1

1

10

100

1000

-100 -50 0 50 100 150

Temperature, oC

Loss

mod

ulus

E",

MPa

HDI

N3300 N100

TDI

IPDIRMDI

MDI

RFE

CB75N

Tg by DSC

RFE

N100

26

25 93

10

47

5950

48

N3300

CB75N

HDI

TDI

RMDI

IPDIMDI

Al-Diis Al-Triis AR-CAl-Diis

AR-Trii

0

10

20

30

40

50

60

70

MDI TDI RMDI IPDI HDI N100 N3300 RFE CB 75N

Isocyanate

Ten

sile

str

eng

th, M

Pa/

Elo

nag

tio

n, %

Tensile strength Elongation

Effects of different isocyanates on flexural modulus of the soy-polyol based cast PU

resins

1380

1180 1190 1220

0 29 23

2480

2040

0

250

500

750

1000

1250

1500

1750

2000

2250

2500

MDI TDI RMDI IPDI HDI N100 N3300 RFE CB 75N

Different Isocyanates

Flex

ural

Mod

ulus

[ M

Pa ]

Swelling in toluene

0

10

20

30

40

50

60

70

80

90

0 1 2 3 4 5 6 7 8 9 10 11 12

Time,Days

Sw

elli

ng

Deg

ree

( w

t% )

CB75N

RFE

N100

MDIN3300

TDI

RMDIHDIIPDI

Conclusions (2)New types of polyurethanes were prepared by reacting soybean oil based polyol and different isocyanates. Aromatic triisocyanates give the highest strength and modulus materials with the highest resistance to swelling.Aromatic and cycloaliphatic diisocynates give materials of lower strength but higher impact resistance. Aliphatic isocyanates produced rubbery PUR’s.