Cast Elastomers from Ethylene Glycol and 1,4- Butane Diol Curatives

Transcription

1 Cast Elastomers from Ethylene Glycol and 1,4- Butane Diol Curatives K. Hillshafer, J. Westfall and S. Stefanova Stepan Company Northfield, IL April, 2015 Nothing contained herein grants or extends a license, expressed or implied, in connection with patents, issued or pending, of the manufacturer or others. The information contained herein is based on manufacturer s own study and the work of others. The manufacturer makes no warranties, expressed or implied, as the accuracy, completeness, or adequacy of the information contained herein. The manufacturer shall not be liable (regardless of fault) to the vendee s employees, or anyone for any direct, special or consequential damages arising out of or in connection with the accuracy, completeness adequacy or furnishing of such information

2 Outline * Background * Architecture of two phase elastomers * Hard and soft segment selection * Thermodynamics of melting * Experimental * Results and Discussion * Elastomer properties from different hard segments * Solubility parameters to support product development * Influence of soft segment interchanges * Summary

3 Background * Elastomers: elastic polymers properties * Tensile Strength, Heat Resistance at a Hardness * Curing of prepolymers: 4,4 - diphenylmethane diisocyanate (MDI) in this study * Influence of polyols used to make prepolymers * Choice of extenders (curatives)

4 Two- phase Elastomers: Soft Segments, Hard Segments and Hard Domains Hard Domain Hard Segment Soft Segments From Thermoplastic Elastomer, Wikipedia

5 Roles of Urethane Elastomer Soft and Hard Segments Soft Segments: Generally high molecular weight polyols Impart flexibility, impact resistance & elongation Hard Segments: Generally lower MW diols & diamines Impart modulus, strength & heat resistance

6 Tailoring Soft Segments * Choices: Polyether polyols primarily from propylene oxide & ethylene oxide or polytetramethylene oxide Polyester polyols primarily adipates of butane diol, ethylene glycol

7 Tailoring Hard Segments from MDI Prepolymers * Choices: Glycols, primarily 1,4- butane diol and ethylene glycol for crystalline hard segments when reacted with MDI Hard segments correlated with melting point Diamines, usually methylene ortho- chloroanaline ( MOCA or MbOCA ), for amorphous hard segments when reacted with prepolymers

8 Tailoring Hard Segments 1,4- butane diol, 90 g mol - 1 ethylene glycol, 62 g mol - 1

9 Hard Segment Melting Point Trends The Gibbs Free Energy predicts spontaneity for processes; for melting, G melt = H melt T melt S melt For T < T melt, ΔG melt > 0 T > T melt, ΔG melt < 0 so at T melt, ΔG melt = 0.

10 Hard Segment Melting Point Trends G melt = H melt T melt S melt Then when ΔG melt = 0 the Gibbs equation becomes T melt = H melt / S melt With Boltzmann s constant, k B, S= k B ln(ω) Ω = degrees of freedom/molecular confirmations T melt = ~Constant/ k B ln(ω) Compared to BDO- MDI hard segments, Ω for EG- MDI is lower so T melt is higher.

11 Background & Study Purpose Therefore, expect higher melting point hard segments from ethylene glycol- MDI hard segments versus 1,4- butane diol analogues. Will this guarantee better properties from EG vs. BDO? If so, the advantages are obvious: amount, price & regulatory. This reasoning neglects soft- segment (polyol) effects.

12 Experimental * Materials * Prepolymers: 5, 10 & 15% NCO from selected polyols and 4,4 - diphenylmethane diisocyanate (MDI). * STEPANPOL PC- 1040P- 55 (ethylene butylene adipate) * STEPANPOL PC- 102P- 56 (butylene adipate) * VORANOL N (polypropylene glycol) * Extenders: * 1,4- butane diol (BDO) * ethylene glycol (EG)

13 Experimental, cont d * Process * Hand mix prepolymer with extender (1.03 index) * Addition of Bicat8 catalyst, ~ 0.1% * Cast and press 1 hour at 120 C * Evaluate * ASTM D- 683, Type I (tensile, ultimate elongation and modulus) * Heat Sag 120 C/30 min. * Differential Scanning Calorimetry (DSC) 10 C/min, - 60 to 250 C

14 Results Elastomeric plaque analysis from an ethylene- butylene adipate so: segment Reference Hardness, Shore A/D Tensile Strength, psi Elongation, Untimate % Modulus, psi Heat Sag, cm 250 /30 min. Thermal Transition, C 15BDO 65/ EG 63/ BDO 61/ ND* 10EG 60/ ND 5BDO 55/ ND 5EG 54/ ND *No thermal transi/on detected

15 Soft Segment Detail Butylene Ethylene Adipate Consider polypropylene glycol (lower polarity):

16 Results: Series 2 (PPG) Elastomeric plaque analysis from a polypropylene glycol so: segment Reference Hardness Shore A Tensile Strength, psi Elongation, % Modulus, psi Heat Sag, cm 250 /30 min. Thermal Transition, C 15BDO 65/ EG 63/ BDO 60/ ND 10EG 61/ ND

17 Quantifying phase separation criteria: solubility parameters δ 2 = ρ F i /M Solubility parameter, δ 2, is in units of (cal/cc) 1/2 ρ is density M is molecular weight F i is a factor for each structural unit Then for polymers, if density is known and approximately equal for oligomers, the sum of factors keeps repeating with increasing molecular weight.

18 Changing Soft Segment Polarity with Polyesters Butylene Adipate Butylene Ethylene Adipate

19 Results: Series 3 (butylene adipate) Elastomeric plaque analysis from a butylene adipate so: segment Reference Hardness Shore A/D Tensile Strength, psi Elongation, % Modulus, psi Heat Sag, 250 /30 min. Thermal Transition, C 15BDO 96/ EG 92/ BDO 92/ ND 10EG 90/ ND

20 Comparing Tensile of the Three Series Plot of 10 and 15% NCO tensile data by prepolymer type and curative Tensile, psi EG 1040 BDO 1040 EG PPG BDO PPG EG 102 BDO 102 EG- BD Adipate PPG BD Adipate Prepolymer % NCO by weight

21 Solubility Parameters of Hard & Soft Segments SoD Segment: STEPANPOL PC- 1040P- 55 (EG- BDO Adipate) 9.0 STEPANPOL PC 102P- 55 (BDO Adipate ) 8.89 Hard Segment: PPG (Propylene Oxide) 6.77 EG- MDI 12.8 BDO- MDI 10.7 Decreasing Polarity 13 δ 2 (cal/cc 3 ) 1/2, calculated 5

22 Summary * Polyol choice contributes to final properties * In the ethylene- butylene adipate prepolymers examined, 1,4- butane diol was a superior curative over ethylene glycol * In polypropylene glycol and butylene adipate prepolymers, ethylene glycol had advantages * Ethylene glycol: lower cost vs. 1,4- butane diol * Regulatory concerns

23 Acknowledgements * Jennifer Westfall * Stella Stefanova * Tom Johnson