Polymer Physics – Insight into Polyurethane

Structure/Property Relationships

Steve Seneker, Ph.D. Anderson Development Company

Outline n  Elastomer Structure (Morphology) n  Effect of Hard-Segment Structure

•  Diisocyanate Symmetry n  TDI n  H12MDI

•  Diol Extenders – Mixed •  Unsymmetrical Urea Hard Segments

n  Effect of Soft-Segment Structure •  Brittleness Temperature or Tg •  Polyol MW Distribution and Crystallizability •  Polyol Compatibility

Elastomer Structure (Morphology)

n  Three Basic Components •  Diisocyanate •  Chain Extender •  Polyol

n  These three components react together and form two phases. •  Hard-segment phase •  Soft-segment phase

Elastomer Structure (Morphology)

n  Hard-Segment Phase •  Diisocyanate •  Chain Extender

n  Soft-Segment Phase •  Polyol

Elastomer Structure (Morphology)

n  Two Types of Hard-Segment Phases

•  Symmetrical Diisocyanates (MDI, H12MDI, NDI,PPDI, TODI) reacted with symmetrical diol curatives.

n  Phase separation driven by order or crystallinity. n  Results in “macro” phase separation.

•  Unsymmetrical Diisocyanates (TDI, IPDI) need aromatic diamine curatives resulting in urea linkages.

n  Phase separation driven by hydrogen bonding of urea linkage n  Results in “micro” phase separation.

Urethane and Urea Linkage: H-Bonding

RN C

O

O

H

R RN C

O

N

H

HR

Urethane (One H-Bond)

Urea (Two H-Bonds)

Elastomer Structure (Morphology)

Elastomer DMTA Curve

Effect of Hard Segment Structure

n  Diisocyanate Symmetry • H12MDI • TDI

n  Diol Extenders - Mixed n  Unsymmetrical Urea Hard Segments

Aliphatic Diisocyanates

N NC C

O O

CH3

CH3 CH3

N

NC

C OO

Dicyclohexylmethane Diisocyanate

(H12MDI)

Isophorone Diisocyanate (IPDI)

CH2CH2

CH2CH2

CH2CH2

NN C

C

O

O

Hexamethylene Diisocyanate

(HDI)

H12MDI Isomers

H12MDI/PTMEG-2000/1,4-Butanediol

Physical  Property   20%  t,t  -­‐H12MDI  97%  t,t-­‐H12MDI  

Hardness,  Shore   26D   41D  Bashore  Rebound,  %   39   58  

ElongaIon,  %   370   720  Tensile  Strength,  psi   2680   3690  

Die  C  Tear,  pli   340   740  Compression  Set,  %   42   27  

Toluene Diisocyanate (TDI) CH3

N

N

CO

CO

CH3N

CO

NC

O

2,4-TDI 2,6-TDI

TDI/PTMEG/1,4-Butandiol

2,4-TDI Content Hardness Tensile Die C Tear Split Tear (wt %) (Shore) (psi) (pli) (pli)

100 60A 1700 170 11

80 51A 800 90 50

0 82A 3200 280 200

Potlife: TDI Isomer Effect

2,4-TDI Content Potlife (wt %) (minutes)

100 12 80 7 65 5 40 3.5 20 3.5 0 3

Toluene Diisocyanate (TDI) CH3

N

N

CO

CO

CH3N

CO

NC

O

2,4-TDI 2,6-TDI

MDI and Mixed Extenders

MDI/PTMEG and Mixed Extenders Curative(s) Ratio Hardness (A) Rebound (%) Clarity

DiHEDS 92 58 Slightly hazy DiHEDS/BDO 75/25 78 47 Clearish DiHEDS/BDO 50/50 81 55 Hazy/Opaque

BDO 90 66 Opaque

DiHEDS 92 58 Slightly hazy DiHEDS/DEG 75/25 75 48 Clear DiHEDS/DEG 50/50 74 45 Clear

DEG 83 56 Opaque

DiHEDS 92 58 Slightly hazy DiHEDS/HDO 75/25 86 56 Hazy DiHEDS/HDO 50/50 84 53 Slightly hazy

HDO 86 63 Opaque

MDI/Polyester and Mixed Extenders

Curative(s) Ratio Hardness (A) Rebound (%) Clarity DiHEDS 88 28 Clearish

DiHEDS/BDO 75/25 69 12 Clear DiHEDS/BDO 50/50 71 12 Clearish

BDO 85 32 Opaque

DiHEDS 88 28 Clearish DiHEDS/DEG 75/25 63 10 Clear DiHEDS/DEG 50/50 60 8 Clear

DEG 75 17 Clear

DiHEDS 88 28 Clearish DiHEDS/HDO 75/25 76 21 Mostly Clear DiHEDS/HDO 50/50 75 20 Clear

HDO 80 30 Hazy/Opaque

Aliphatic – Urea n  Prepolymer:

•  2,4-TDI/PPG Diol - 3.0% NCO •  Aliphatic Diisocyanate (NBDI, Des W, IPDI, TMXDI) •  % NCO: 4.0 and 8.0

n  Curative: Curene 89 LC (low color DETDA) n  Casting Conditions:

•  Prepolymer @ 60 C, Curative @ R.T. •  Molds preheated @ 100 C •  Stoichiometry: 0.95

n  Curing Conditions: 16 hours @ 100 C n  Samples conditioned at least 2 weeks prior to

testing.

4% NCO Results

Aliphatic Isocyanate

Shore Hardness Rebound % Elongation %

Tensile Strength

psi Die C

Tear pli

Split Tear pli

IPDI 77A 62 770 3190 265 89

TMXDI 76A 59 820 2820 265 125

Des W 82A 59 840 3270 260 88

NBDI 78A 61 750 3140 260 86

8% NCO Results

Aliphatic Isocyanate

Shore Hardness Rebound% Elongation %

Tensile Strength

psi Die C

Tear pli

Split Tear pli

IPDI 97A, 46D 56 740 4280 440 242

TMXDI 97A, 47D 59 730 4360 430 238

Des W 98A, 54D 57 590 4140 515 243

NBDI 97A, 48D 59 650 4640 460 197

H12MDI/PTMEG-2000/DETDA

Physical  Property   20%  t,t  -­‐H12MDI   97%  t,t-­‐H12MDI  

Hardness,  Shore   47D   47D  Bashore  Rebound,  %   53   57  ElongaIon,  %   310   380  Tensile  Strength,  psi   4410   4410  Die  C  Tear,  pli   510   590  Compression  Set,  %   50   55  

Effect of Soft Segment Structure

n  Polyol Effect on Tg/Brittleness Temperature

n  Polyol MW Distribution n  Polyol Compatibility

Polyether Polyols

CH2CH2

CH2CH2

OO H

H n

CH2CH

CH3

OO H

H

n

CH2CH2CH2

OH

OHn

Polypropylene Glycol (PPG)

Polytetramethylene Glycol (PTMEG) Polytrimethylene Glycol (Cerenol Polyol)

CH2CH

CH3

OO CH2

CH2O

HCH2CH2

OH

nx x

Hydroxyethyl capped Polypropylene Glycol

(EO capped PPG)

Polyester Polyols

O

O

O

OO

H OH

x

O

O

O

OO

H OH

x

O

OO

HO

O

OH

xx

Polyethylene Adipate

Polybutylene Adipate

Polycaprolactone (1,4-BDO initiated)

Brittleness Point – Polyol Effect

n  PTMEG • 70A to 75D: -68C (-90F) to -55C (-67F)

n  PPG • 70A to 75D: -45C (-49F) to -26C (-15F)

n  Polyesters • 70A to 70D: -27C (-17F) to -13C (9F)

Ultra-Low Monol PPG versus PTMEG

Ultra-Low Monol PPG PTMEG

Chemical Structure

-O(-CH2-CH-O)x- I

CH3

Tg ≈ -75°C

-O(-CH2 CH2 CH2 CH2-O)x-

Tg ≈ -84°C

Hydroxyl Type (Reactivity)

Secondary Hydroxyl (Lower Reactivity)

Primary Hydroxyl (Higher Reactivity)

Molecular Weight Distribution (Viscosity)

Narrow: Mw/Mn = 1.02-1.15

(Acclaim 2200: 165 cps @ 40°C)

Broad: Mw/Mn = 1.7-2.4

(PTMEG-2000: 1200 cps @ 40°C)

Crystallizability Noncrystallizable (Liquid; Pour Point = -33°C)

Crystallizable (Waxy Solid; m.p. = 28 to 40°C)

Stress/Strain Curves – 80 Shore A Elastomers (MDI Prepolymers; BDO Cured)

Effect of Polyester Crystallizability on Stress/Strain Curves of 80 Shore A Elastomers (MDI Prepolymers; BDO Cured)

0

5

10

15

20

25

30

35

40

45

0 200 400 600 800 1000 1200 1400

Strain (%)

Stre

ss (M

Pa)

PBA PCL PEBA PMPA

PBA – Polybutylene Adipate PCL - Polycaprolactone PEBA - Polyethylene Butylene Adipate PMPA - Poly-2-Methyl-1,3-Propanediol Adipate

Polyol Molecular Weight Distribution

Ultra-Low Monol PPG versus PTMEG in Polyurethane/Urea Elastomers

(6% NCO 2,4-TDI Prepolymers; MBOCA Cured)

PPG-1000 Acclaim® 4200/DEG

Andur® 2-92 AP

Hardness, Shore 83A 92A 92A Pendulum Rebound, % 15 55 46

Ultimate Elongation, % 340 310 410 Tensile Strength, MPa 9.3 21.7 48.2

Die C Tear Strength, kN/m 39 88 91

Andur® is a registered trademark of Anderson Development Company

Polyol Compatibility

n  Krasol Polyols • Hydroxyl-terminated polybutadienes • Functionality close to 2.0 • Miscible with PPG and PTMEG polyols

Curatives Used for Compatibility Study – Aromatic Diamines

MBOCA

MCDEA

Cl Cl

NH2

NH2NH2

NH2

S CH3

CH3

SCH3

O

O

O

O (CH2)3

NH2 NH2

ClCl NH2NH2

H3CH2C

CH2CH3 H3CH2C

CH2CH3

Curene 107

•  Versalink 740M

TDI-80/Krasol LBH-3000 (NCO:OH = 1.90; 2.04% NCO)

MBOCA MCDEA Curene 107 (Ethacure 300)

Versalink 740M

Potlife 6’ 00” 4’ 30” 6’ 00” 25’ Demold 40 min. 30 min. 35 min. > 60 min. Prepolymer Appearance Solid Flakes Clear Clear Opaque Elastomer Appearance Solid Flakes Clear Clear Opaque Shore Hardness ---- 73A 65A 65A Elongation, % ---- 290 350 350 Tensile Strength, psi ---- 1510 1560 1240 100% Modulus, psi ---- 750 540 510 300% Modulus, psi ---- ---- 1280 1100 Die C Tear, pli ---- 145 113 112 Split Tear, pli ---- 29 27 24

Hydrolytic Stability Data

n  Test Solutions: • Water (90C, 3 weeks) • 50% Sodium hydroxide (RT, 3 weeks) • 60% Sulfuric acid (RT, 3 weeks) • Sodium hypochlorite (5% Cl) (RT, 5

weeks)

90C Water Immersion, 3 weeks H2O immersion, 90C for 3 weeks

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

140.0%

PPG/MBOCA PTMEG/MBOCA Krasol/PPG/MBOCA Krasol/MCDEA Krasol/Curene 107

Candidate

% R

eten

tion Hardness

Tensile100% ModulusElongation

60 % Sulfuric Acid Immersion (RT), 3 weeks H2SO4, RT, 3 weeks

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

140.0%

PPG/MBOCA PTMEG/MBOCA Krasol/PPG/MBOCA Krasol/MCDEA Krasol/Curene 107

Candidate

% R

eten

tion Hardness

Tensile100% ModulusElongation

Sodium Hypochlorite (5% Cl) (RT), 5 weeks

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

120.0%

PTMEG/MBOCA Krasol/MCDEA Krasol/Curene 107

Candidate

% R

eten

tion

Tensile100% ModulusElongation

Outline n  Elastomer Structure (Morphology) n  Effect of Hard-Segment Structure

•  Diisocyanate Symmetry n  TDI n  H12MDI

•  Diol Extenders – Mixed •  Unsymmetrical Urea Hard Segments

n  Effect of Soft-Segment Structure •  Brittleness Temperature or Tg •  Polyol MW Distribution and Crystallizability •  Polyol Compatibility

Acknowledgements

n  Mobay Corporation (Bayer Material Science)

n  ARCO Chemical (Lyondell Chemical)

n  Anderson Development Company

n  PMA (Polyurethane Manufacturer’s Association)

n  CPI (Center for the Polyurethane Industry)