Polyurea Synthesis and Properties as a Function of Hard-Segment Content

1988 ◽  
Vol 61 (1) ◽  
pp. 86-99 ◽  
Author(s):  
Z. S. Chen ◽  
W. P. Yang ◽  
C. W. Macosko
Keyword(s):  
Molecular Weight ◽  
Hard Segment ◽  
Soft Segment ◽  
Tensile Elongation ◽  
Mechanical And Thermal Properties ◽  
Solution Polymerization ◽  
Dynamic Mechanical ◽  
Hard Segment Content ◽  
Mechanical Modulus ◽  
Dynamic Mechanical Modulus

Abstract High-molecular-weight linear polyureas of different hard-segment content are obtained with a two-step solution polymerization. Elimination of water, careful choice of solvent, reactant concentration, and good control of reaction temperature are essential to obtain satisfactory results. We have studied the influence of the hard-segment content on the mechanical, dynamic-mechanical, and thermal properties of these solution polymerized amine-terminated polypropylene-oxide-based thermoplastic polyureas. Two-phase morphology is predominant within the range of the hard-segment concentration studied. Inversion of the continuous and dispersed phase might occur in the polyurea series at about 60 wt.% of hard segment. This changes the nature of the polyureas from a tough elastomeric material to a more brittle, high-modulus plastic. The modulus of the rubbery plateau measured from dynamic-mechanical spectra increases with hard-segment concentration due to the reinforcing effect of hard-segment domains. However, continuous improvement in dynamic-mechanical modulus is not significant when the hard segment is above 50 wt.% due to higher degree of phase mixing in high hard-segment concentration systems. The amount of solubilized hard segment in the soft-segment phase in these polyureas is limited as judged from the relatively constant soft-segment Tg. However, the extent of phase separation, as determined by the heat capacity change ΔCp across the soft-segment Tg, decreases with increasing hard-segment content. The same characterizations and analyses have also been carried out on a series of RIM produced polyurea samples of the same composition. Great difference in properties is observed in comparison of these two sets of samples due to their different synthesis routes. In general, samples produced by RIM exhibit lower molecular weight, lower dynamic-mechanical modulus, higher soft-segment Tg, more phase-mixed, and more tensile elongation than those synthesized by solution polymerization. The detailed comparison will be treated in a separate paper.

Synthesis and Properties of Polyurethane-Based Actuator with Poly(dimethyl Siloxane)

2009 ◽  
Vol 620-622 ◽  
pp. 299-302
Author(s):  
Nam Ju Jo ◽  
Do Hee Lim ◽  
Young Min Song ◽  
Geong Mi Bark ◽  
Won Ki Lee
Keyword(s):  
Hard Segment ◽  
Soft Segment ◽  
Polar Phase ◽  
Stress Effect ◽  
Maxwell Stress ◽  
Diphenylmethane Diisocyanate ◽  
Free Charge ◽  
Dimethyl Siloxane ◽  
Hard Segment Content ◽  
Compliant Electrodes

This paper investigated the use of electrostrictive polymers with compliant electrodes as a means of actuator. In many electrostrictive materials, especially polyurethane (PU) can produce large deformation and force because of its low elastic modulus.The electromechanical response is mainly due to Maxwell stress effect and electrostriction effect. When a thin film of dielectric elastomer is applied to an electric field, it will experience Maxwell stress caused by interactions of free charge between the electrodes and electrostriction caused by the reorientation of polar phase in the material. In this work, PU was composed of the soft segment with poly(dimethyl siloxane) (PDMS) and the hard segment with 4, 4’-diphenylmethane diisocyanate. Also the hard segment content of synthesized PU was controlled at 20, 25, 30, and 35wt%. To conclude, mechanical properties increased with the increase in hard segment contents. However actuation test showed that the deformation was decreased as hard segment contents increased.

Effects of Ionic Group on the Shape Memory Performance of Polyurethane

2016 ◽  
Vol 848 ◽  
pp. 140-147
Author(s):  
Yan Ou Hu ◽  
Hui Qin Lian ◽  
Lei Zu ◽  
Yue Ting Li ◽  
Yang Liu ◽  
...  
Keyword(s):  
Shape Memory ◽  
Hard Segment ◽  
Soft Segment ◽  
Memory Performance ◽  
Average Molecular Weight ◽  
Phenyl Isocyanate ◽  
Exchange Capacity ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Hard Segment Content

Ionic polyurethane (IPU) was synthesized as shape memory materials. Poly (tetramethylene ether) glycol with 2000g/mol number average molecular weight were used as soft segment, 4,4-methylenebis (phenyl isocyanate), and 1,2-dihydroxy-3-propanesulfonic acid salt were used to compose the segment of SMP materials. The structure and properties of these IPU films were characterized by Fourier Transform infrared, X-ray diffraction, Thermal gravimetric analysis and Differential scanning calorimeter. The results showed that the glass transition temperature of the IPU increased with the increase of hard segment content. The physical properties in terms of swelling property, water absorption and ion-exchange capacity increased with the improving of sulfonic group content in IPU. The shape memory property of IPU exhibited that the shape fixity ratio and recovery rate improved remarkably with the increase of hard segment content.

Influence of soft segment molecular weight on the mechanical hysteresis and set behavior of silicone-urea copolymers with low hard segment contents

Polymer ◽  
2011 ◽  
Vol 52 (2) ◽  
pp. 266-274 ◽  
Author(s):  
Iskender Yilgor ◽  
Tugba Eynur ◽  
Sevilay Bilgin ◽  
Emel Yilgor ◽  
Garth L. Wilkes
Keyword(s):  
Molecular Weight ◽  
Hard Segment ◽  
Soft Segment ◽  
Mechanical Hysteresis

scholarly journals The influence of hard segment content on mechanical and thermal properties of polycarbonate-based polyurethane materials

2012 ◽  
Vol 66 (6) ◽  
pp. 853-862 ◽  
Author(s):  
Jelena Pavlicevic ◽  
Milena Spirková ◽  
Jaroslava Budinski-Simendic ◽  
Mirjana Jovicic ◽  
Oskar Bera ◽  
...  
Keyword(s):  
Phase Separation ◽  
Hard Segment ◽  
Soft Segment ◽  
Chain Extender ◽  
Melting Enthalpy ◽  
Degree Of Crystallinity ◽  
Elongation At Break ◽  
Hard Segment Content ◽  
Hard Segments ◽  
Polycarbonate Diol

Aliphatic segmented polyurethanes were prepared by one-step procedure in catalytic reaction between polycarbonate diol, hexamethylene-diisocyanate and 1,4-butandiol (as chain extender). The hard segment content TS was varied (17, 24, 30 and 42 wt. %) by changing the ratio of starting compounds. The soft segment is made from flexible aliphatic polycarbonate diol, while hard segments consist of chain extender and diisocyanate component. In order to study the hydrogen bonding formation and phase separation, Fourier transform infrared spectroscopy (FT-IR) was used. Wide angle X-ray scattering (WAXS) was performed to determine a degree of crystallinity and to investigate the phase behavior of prepared elastomers. The effect of TS content on mechanical properties (tensile strength, elongation at break and hardness) was tested. Thermal behavior of prepared novel polycarbonate-based polyurethanes was investigated using differential scanning callorimetry (DSC). It was determined that the elastomer which contains the highest amount of urethane groups in its structure (TS content of 42 wt. %) exhibits the most pronounced phase separation and the highest degree of crystallinity. All prepared polyurethanes exhibit high elongation at break (over 700%). The glass transition temperature Tg of prepared samples was in the temperature region from ?39 to ?36?C, and it was found to be slightly influenced by the soft segment content. The enthalpy of chain segments relaxation in diffused region between hard and soft domains (detected in the temperature range from 35 to 55 ?C) was decreased with the increase of hard segment content. The multiple melting of hard segments (connected with the dissruption of physical crosslinks) appeared above 100 ?C. It was found that the melting enthalpy linearly increases with the increase of urethane group content. Sample with 42 wt. % of TS has the highest value of melting enthalpy (41.5 J/g).

Topography and Wettability of Waterborne Polyurethane Coatings with Varying Amounts of Hard Segments

2013 ◽  
Vol 634-638 ◽  
pp. 3033-3037
Author(s):  
Yu Hong Qi ◽  
Zhan Ping Zhang ◽  
Yan Zhang ◽  
Mei Miao
Keyword(s):  
Laser Scanning ◽  
Hard Segment ◽  
Soft Segment ◽  
Hydrophobic Surface ◽  
Waterborne Polyurethane ◽  
Contact Angles ◽  
Water Contact ◽  
Hard Segment Content ◽  
Fouling Release ◽  
Hard Segments

Topography and wettability plays an important role to fouling release performance of a coating. Surface morphology and water contact angles (WCA) depending on time of three waterborne polyurethane (WPU) coatings were studied by laser scanning microscope and optical contact angle meter. The results show that WPU coatings with low hard segment content are consisted of hard segment domains, soft segment domains and crack-like non-cohesive regions. With increasing hard segment content, nanostructured micro-phase separated topography is easier to forming, and crack-like non-cohesive regions is reduced. A stable hydrophobic surface in the WPU system can be obtained by drying coating at 60C as well as adding hard segment content to improve fouling release performance of the coatings.

The influence of 4,4’-bis(6-hydroxyhexoxy)biphenyl moieties on properties of polyurethanes based on 4,4’-methylenebis(cyclohexyl isocyanate)

e-Polymers ◽  
2006 ◽  
Vol 6 (1) ◽  
Author(s):  
Tymon Łazarewicz ◽  
Józef T. Haponiuk ◽  
Adolf Balas
Keyword(s):  
Molecular Weight ◽  
Phase Inversion ◽  
Hard Segment ◽  
Microphase Separation ◽  
Low Molecular Weight ◽  
Polarization Microscopy ◽  
Melting Temperatures ◽  
Hard Segment Content ◽  
Isomer Content ◽  
Thermal Stability Of

AbstractTwo series of polyurethanes (PUs) were synthesized from a low molecular weight diol - 4,4’-bis(6-hydroxyhexoxy)biphenyl (BH6), a high molecular weight diol - poly(1,6-hexylene adipate)diol (PHA) and 4,4’-methylenebis (cyclohexyl isocyanate) (HMDI) using two fractions of different trans,trans isomer content (uT), respectively: 16%, 46%. The effect of low molecular diol content (uB) in the total mass of the diols used for synthesis on properties of PUs was investigated by DSC, DTA, TGA, polarization microscopy, WAXS, DMTA and tensile testing. For segmented PUs microphase separation is observed and melting temperatures of hard segment (HS) microphases are almost constant within the series for uB≥ 40%. The growth of hard segment content (uHS) induces rectilinear growth of crystallization enthalpy of HS microphases. PUs of uT= 46% show birefringence of HS microphases at uBB ≥ 40%. Glass transition temperatures of HS microphases shift towards lower values with a decrease of uB. PUs of u B = 80 and 100% are stiff, for 20 - 60% elastomeric properties are observed, and in absence of low molecular diol moieties (uB= 0%) plastic behaviour is shown when stretched. Phase inversion is observed between u B BB = 60 and 80%. Thermal stability of PUs (by TGA and DTA) does not depend on uBand uT.

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