Thermal and Mechanical Properties of Polyurethanes Derived from Mono- and Disaccharides

Thermal and mechanical properties of polyurethane (PU) sheets pre-pared from the glucose/fructose/sucrose–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system were examined by differential scanning calorimetry, thermogravimetry, dynamic mechanical analysis and tensile tests. The saccharide content was varied at a constant NCO: OH ratio of 1·0. The glass transition temperature (T_g) increased with increasing saccharide content. The incorporation of saccharides into the PU structure results in a higher crosslinking density and a higher content of hard segments. The thermal decomposition was dependent on the saccharide content, an increase leading to a lower thermal decomposition temperature (T_d). The dissociation of saccharide OH groups and NCO groups is a major part of the thermal decomposition of these PUs. Dynamic mechanical analysis revealed two kinds of relaxation: the high temperature relaxation corresponds to main chain motion and the other is a local mode relaxation due to non-reacted isocyanate groups. The tensile stress and Young’s modulus increased with the saccharide content. © of SCI.     

Polyurethanes from benzene polyols synthesized from vegetable oils: Dependence of physical properties on structure

Asymmetric and symmetric aromatic triol isomers were synthesized from erucic acid. The pure asymmetric and symmetric triols were crosslinked with MDI into their corresponding polyurethane sheets. The physico‐chemical properties of these polyurethanes were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis coupled with Fourier transform infrared (TGA‐FTIR) spectroscopy, and tensile analysis. The A‐PU and S‐PU demonstrated differences in their glass transition temperatures (T_g) and crosslinking densities. The difference in T_g of these polyurethanes could be explained by the differences in crosslinking densities, which could be related to the increase in steric hindrance, to the crosslinking MDI molecules, between adjacent hydroxyl groups of the asymmetric triol monomers. Overall, it was found that both polyurethanes had similar mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of crosslinking density on structure and properties of interpenetrating polymer networks from polyurethane and nitroguar gum

Semi‐interpenetrating polymer networks (semi‐IPNs) of castor oil‐based polyurethane prepolymer and nitroguar gum (NGG) with different crosslinking density of the PU network, coded as UNG films, were prepared through varying the trimethanol propane (TMP)/1,4‐butanediol (BDO) molar ratios in the chain extender mixture. The effects of crosslinking density on the structure and properties of the UNG films was investigated by attenuated total reflection Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, scanning electron microscopy, crosslinking density measurements, solvent‐extracting tests, and tensile tests. The experimental results revealed that incorporation of TMP crosslinker into the hard segments of polyurethane resulted in a decrease in the aggregation of hard segments. With an increase of the TMP/BDO molar ratios, the semi‐IPN films exhibited the higher crosslinking density, glass temperature (T_g), stiffness, and tensile strength (σ_b). Furthermore, the experimental results also indicated that NGG restricted the formation of crosslinking networks when the TMP content is relatively high, which led to the negative deviation of the theoretically predicted crosslinking density and Dibenedetto's equation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)

Poly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T_g) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T_g and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006     

Mechanical properties of blocked polyurethane/epoxy interpenetrating polymer networks

The mechanical properties of blocked polyurethane(PU)/epoxy interpenetrating polymer networks (IPNs) were studied by means of their static and damping properties. The studies of static mechanical properties of IPNs are based on tensile properties, flexural properties, hardness, and impact method. Results show that the tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs decreased with increase in blocked PU content. The impact strength of IPNs increased with increase in blocked PU content. It shows that the tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (CaCO₃) content to a maximum value at 5, 10, 20, and 25 phr, respectively, and then decreased. The higher the filler content, the greater the hardness of IPNs and the lower the notched Izod impact strength of IPNs. The glass transition temperatures (T_g) of IPNs were shifted inwardly compared with those of blocked PU and epoxy, which indicated that the blocked PU/epoxy IPNs showed excellent compatibility. Meanwhile, the T_g was shifted to a higher temperature with increasing filler (CaCO₃) content. The dynamic storage modulus (E′) of IPNs increased with increase in epoxy and filler content. The higher the blocked PU content, the greater the swelling ratio of IPNs and the lower the density of IPNs. The higher the filler (CaCO₃) content, the greater the density of IPNs, and the lower the swelling ratio of IPNs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1826–1832, 2006     

Pultruded fiber reinforced blocked polyurethane (PU) composites. II. Processing variables and dynamic mechanical properties

Unidirectional fiber reinforced blocked polyurethane (PU) composites have been prepared by the pultrusion process. The effects of processing variables on the mechanical properties and dynamic mechanical properties of fiber reinforced PU composites by pultrusion have been studied. The processing variables investigated included pulling rate (in-line speed), die temperature, postcure time and temperature, and filler type and content. The dynamic mechanical properties of the composites produced by the process were studied utilizing dynamic mechanical spectrometer. Results show that the composites possessed various optimum pulling rates at different die temperatures. From the DSC data analysis, swelling ratio, and mechanical properties, the optimum die temperature was determined. It was found that the mechanical properties increase with filler content for various types of filler. The increasing of mechanical properties depends on the optimum postcure temperature and time. However, the properties decreased for longer postcure times since the composite materials were degraded. The glass-transition temperature (T_g) increased slightly and the damping peak (tan δ) was broadened due to fiber reinforcement. The dynamic mechanical moduli (G′, G″) of pultruded PU composites are apparently higher than those of the matrices. The moduli (G′, G″) increase with increasing fiber and filler content, and the damping peak becomes broad. Effect of postcuring on the degree of crosslinking, T_g, and dynamic modulus will be discussed.     

Structure‐property relationship in polyurethane elastomers containing starch as a crosslinker

Polyurethane elastomers were synthesized using polypropylene glycol (PPG 2000) as the polyol and starch as the multifunctional crosslinker in varying concentrations. Thermal and mechanical properties were measured by DSC, DMA and tensile tests. The morphology was examined by SEM. The swelling behavior of the polyurethanes in various solvents was investigated and the solubility parameter was determined. All these properties were compared with those of polyurethanes containing 1,1,1 ‐trimethylol propane (TMP) as the crosslinker. Starch‐based polyurethanes exhibited better mechanical properties. The effect of varying the starch:TMP ratio on the mechanical strength was also studied. With increasing starch content, the tensile strength and elongation increased. The starch‐based PUs exhibited two glass transitions, whereas TMP‐based PUs exhibited one T_g. No significant difference in the T_gs of the two PUs was observed. The activation energy of St‐PU calculated from DMA was 69 kcal/mol. Soil degradation tests indicated greater biodegradability in polyurethanes containing starch than in those containing TMP.     

Effects of hard-segment compositions on properties of polyurethane–nitrolignin films

Segmented polyurethane (PU) films from castor-oil-based PU prepolymer with different hard-segment compositions and nitrolignin (NL) were synthesized. Diisocyanates (DIs), such as 2,4-tolylene DI (TDI) and 4,4′-diphenylmethane DI (MDI), 1,4-butanediol (BDO) as a chain extender, and trimethanol propane (TMP) as a crosslinker were used to obtain PU films containing NL (UL) which were named as UL–TB for TDI and BDO, UL–TT for TDI and TMP, UL–MB for MDI and BDO, and UL–MT for MDI and TMP, respectively. The mechanical properties and thermal stability of the films were characterized by a tensile test and thermogravimetric analysis, respectively. The MDI-based UL films exhibited a higher tensile strength (σ_b) and thermal stability than TDI-based UL. However, the recoverability of the TDI-based UL films was better than that of others. The UL films with TMP (UL–TT and UL–MT) had higher σ_b and lower breaking elongation (ϵ_b) than the UL films with BDO (UL–TB and UL–MB), caused by enhancement in the crosslinking network of hard segments and microphase separation between soft and hard segments. The values of σ_b and ϵ_b of the UL films that contained NL were much higher than those of the PU films, which indicates that the introduction of NL increased the interaction between hard segments by crosslinking. The hydrogen bonding in the UL films was studied by infrared spectroscopy, which indicated that MDI favored the formation of hydrogen bonds, especially in the ordered domain. Differential scanning calorimetry, dynamic mechanical analysis, and wide-angle X-ray diffraction indicated that the UL films were compatible as a whole, but microphase separation existed between soft and hard segments and significantly affected the mechanical properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3251–3259, 2001     

Simultaneous full‐interpenetrating polymer networks of blocked polyurethane and vinyl ester. II. Static and dynamic mechanical properties

Simultaneous full‐interpenetrating polymer networks (full‐IPNs) based on blocked polyurethane (PU) and vinyl ester (VE) have been prepared. The static and dynamic properties of these IPNs have been examined. Results show that the tensile strength and flexural strength of IPNs increased with blocked PU content to a maximum value at 7.5 wt % PU content and then decreased. The tensile modulus, flexural modulus, and hardness of IPNs decreased with increasing blocked PU content. The impact strength of IPNs increased with increasing blocked PU content. The tensile strength, flexural strength, tensile modulus, and flexural modulus of IPNs increased with filler (kaolin) content to a maximum value at 20 to 25 phr filler content and then decreased. The higher the filler content, the greater the hardness, and the lower the impact strength of IPNs. The tensile strength, flexural strength, tensile modulus, flexural modulus, and hardness of IPNs increased with increasing VE initiator content. The dynamic technique was used to determined the damping behavior across a temperature range. Results show that the glass transition temperature (T_g) of IPNs are shifted inwardly compared with pure PU and VE, which indicated that the blocked PU–VE IPNs showed excellent compatible. Meanwhile, the glass transition temperature was shifted to a higher temperature with increased filler content. The dynamic storage modulus (E′) of IPNs increased with increasing VE and filler content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1977–1985, 1999     

Use of short isobornyl methacrylate building blocks to improve the heat and oil resistance of thermoplastic elastomers via RAFT emulsion polymerization

Triblock copolymer (TCP)‐based thermoplastic elastomers (TPEs) were designed via reversible addition–fragmentation chain‐transfer emulsion polymerization. Short isobornyl methacrylate (IM) building blocks in the two ends of molecular chain were incorporated to guarantee the mechanical properties of the TPEs at high temperature (i.e., heat resistance) because of the high glass‐transition temperature (T_g) of poly(isobornyl methacrylate) (PIM; ～180 °C). The microphase separation, tensile properties at different temperatures, dynamic mechanical properties, oil resistance, and thermal stability of the TPEs were extensively characterized. The TPEs had distinct microphase separation with a wide inter‐T_g interval (150–185 °C). The tensile strength and elongation at break of the TPEs decreased with increasing temperature from 25 to 100 °C because of the reduced interactions in the phase domain. Even so, the TPEs had a high elongation at break beyond 200% and little change in the tensile strength even at 100 °C together with a wide quasi‐platform stage between the T_g values in dynamic mechanical analysis; this indicated good heat resistance. Meanwhile, the TPEs had an enhanced oil resistance and a thermal stability higher than 300 °C. These TCP‐based TPEs with heat and oil resistance broaden the application potential in practical fields. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45379.     

Biodegradable polyurethane based on random copolymer of L‐lactide and ϵ‐caprolactone and its shape‐memory property

A series of biodegradable polyurethanes (PUs) are synthesized from the copolymer diols prepared from L ‐lactide and ε‐caprolactone (CL), 2,4‐toluene diisocyanate, and 1,4‐butanediol. Their thermal and mechanical properties are characterized via FTIR, DSC, and tensile tests. Their T_gs are in the range of 28–53°C. They have high modulus, tensile strength, and elongation ratio at break. With increasing CL content, the PU changes from semicrystalline to completely amorphous. Thermal mechanical analysis is used to determine their shape‐memory property. When they are deformed and fixed at proper temperatures, their shape‐recovery is almost complete for a tensile elongation of 150% or a compression of 2‐folds. By changing the content of CL and the hard‐to‐soft ratio, their T_gs and their shape‐recovery temperature can be adjusted. Therefore, they may find wide applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4182–4187, 2007     

Effects of Temperature on Morphology and Properties of Films Prepared from Poly(ester‐urethane) and Nitrochitosan

Summary: Novel elastic materials were prepared by mixing semicrystalline polyester‐based polyurethane (PU) synthesized at 100 °C with nitrochitosan (NCH) and 1,1,1‐tris(hydroxylmethyl)propane as crosslinker, and then by curing the mixture at 18, 25, 40, 60, and 80 °C. The effects of cure temperature on the crystallization behavior, miscibility, and mechanical properties of the PUNCH materials were studied by attenuated total reflection Fourier transform IR, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, X‐ray photoelectron spectroscopy, and tensile test. The results indicated that the crystalline structure of the blend films was more easily interrupted as the cure temperature increased, leading to a decrease of the degree of crystallinity. With an increase of cure temperature, the blend films exhibited high crosslinking density and tensile strength, and the phase separation between hard and soft segments of PU enhanced, resulting in a decrease in the glass transition temperature (T_g) of soft segment. Interestingly, the composite films keeping high elongation at break possessed tensile strength higher than that of the native poly(ester‐urethane). The enhanced mechanical properties of the blend films can be attributed to the relatively dense crosslinking network and strong intermolecular hydrogen bonding between NCH and PU. Therefore, this study not only provided a novel way by adding NCH into PU matrix to prepare elastic materials, which would remain functional characteristic of chitosan, but also expanded the application field of chitosan.

The cure temperature dependence of the tensile strength and elongation at break for the PEPU‐100 and PUNCH‐100 films.     

Comparison of the effects of linking diglycidyl ether‐terminated PDMS and BPA onto polyurethane with respect to the tensile and thermal properties

Flexible poly(dimethylsiloxane) (PDMS) or rigid bisphenol A (BPA) with diglycidyl ether end groups was linked to polyurethane (PU), which was composed of 4,4′‐methylenebis(phenyl isocyanate) as a hard segment and poly(tetramethylene ether)glycol as a soft segment. A control PDMS (CPDMS) series was prepared with an additional deprotonation step by NaH. The spectroscopic, thermal, tensile, shape memory, and low‐temperature flexibility properties were compared with those of plain PU to investigate the effects of linking the flexible PDMS or the rigid BPA on PU. The soft segment melting peaks were not affected by the PDMS content for the PDMS series but disappeared as the BPA content increased in the BPA series. The soft segment crystallization of PU was completely disrupted as the linked BPA content increased in the differential scanning calorimetry results and disappeared in the dynamic mechanical analysis results. The glass transition temperature (T_g) of the BPA series increased with increasing BPA content, whereas that of the PDMS series remained the same. The tensile strength of the PDMS series sharply increased with increasing PDMS content. The shape retention of the BPA series at ?25 °C sharply decreased as the BPA content increased. Finally, the BPA series linked with rigid aromatic BPA demonstrated excellent low‐temperature flexibilities compared with the PDMS series and plain PU. Compared with PUs linked with PDMS, PUs linked with rigid BPA demonstrated a significant change in the cross‐link density, thermal properties, shape retention, and low‐temperature flexibility. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43284.     

Preparation and properties of novel poly(propylene oxide)‐block‐polylactide‐based polyurethane foams

A novel degradable flexible polyurethane (PU) foam was prepared by varying the ratio of poly(propylene oxide) (PPO) and triarm poly(propylene oxide)‐block‐polylactide copolymer (PPO‐b‐PLA), and was compared with conventional PU foams based on toluene diisocyanate (TDI) and PPO. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) showed that introducing PLA segments were able to result in a transition from a microphase separated state to a microphase mixed state and improve the microphase mixing. The changes in structure and domain size distribution associated with this transition were found to have led to enhanced mechanical properties such as the tensile strength, the elongation at break, and the rebound resilience for the PU foams containing PLA segments. Furthermore, it was observed that the network structure was destroyed by hydrolytic degradation in alkali solution (10 wt%/vol%) at 80°C for 50 h, and that as the PLA content increased, the degradation rate of PU foams enhanced. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Synthesis and characterization of multiwalled carbon nanotube/polyurethane composites via surface modification multiwalled carbon nanotubes using silane coupling agent

Well‐dispersed multiwalled carbon nanotubes/polyurethane (MWCNTs/PU) composites were synthesized in situ polymerization based on treating MWCNTs with nitric acid and silane coupling agent. The morphology and degree of dispersion of the MWCNTs were studied using a high resolution transmission electron microscopy (HR‐TEM) and X‐ray powder diffraction (XRD). The result showed that MWCNTs could be dispersed still in the PU matrix well with the addition of 2 wt% MWCNTs. The thermal and mechanical properties of the composites were characterized by dynamic mechanical thermal analysis, thermogravimetric analysis, tensile, and impact testing. The result suggested that the glass transition temperature (T_g) of composites increased greatly with increasing MWCNTs content slightly, and the MWCNTs is also helpful to improve mechanical properties of composites. Furthermore, the composites have an excellent mechanical property with the addition of 0.5 wt% MWCNTs. The electrical property testing indicates that the MWCNTs can improve evidently the electrical properties of composites when adding 1 wt% MWCNTs to the PU matrix. The volume resistivity of composites reaches to an equilibrium value. POLYM. COMPOS., 33:1866–1873, 2012. © 2012 Society of Plastics Engineers     

Physical Properties of Polyurethanes Produced from Polyols from Seed Oils: I. Elastomers

Polyols synthesized by ozonolysis and hydrogenation from canola oil were reacted with aliphatic 1,6-hexamethylene diisocyanates (HDI) to produce polyurethane (PU) elastomers. The properties of the materials were examined by dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), modulated differential scanning calorimetry (MDSC), and thermogravimetric analysis (TGA), and measurements were taken of tensile properties. The effect of dangling chains on network properties was assessed. The formation of hydrogen bonds was observed by FTIR. The measured properties were found to be strongly dependent on processing-dependent factors such as the crosslinking density and the molar ratio of polyols to HDI component. The glass transition temperatures (T _g) of the elastomers were found to increase as the OH/NCO molar ratio decreased. With the same OH/NCO molar ratio, T _g of canola-oil-based PU was higher than that of soybean-oil-based PU. The TGA thermographs showed two well-defined steps of degradation for all the elastomers. In the first step, up to 30% weight loss, the fastest rate of loss was found at 345 °C for canola-oil-based PU while soybean-oil-based PU lost most of the weight in the second step. With the same OH/NCO molar ratio, the elastomers made from canola-oil-based polyol showed slightly higher Young’s modulus and tensile strength.     

Polymeric carbon nanocomposites from multiwalled carbon nanotubes functionalized with segmented polyurethane

Multiwalled carbon nanotubes (MWNT) were functionalized with segmented polyurethanes (PU) by the “grafting to” approach. Raman and X‐ray photoelectron spectroscopy (XPS) spectra show that the sidewalls of MWNTs have been functionalized with acid treatment, and the amount of COOH increases with increasing acid treatment time. FTIR and X‐ray diffraction (XRD) spectra confirm that PU is covalently attached to the sidewalls of MWNTs by esterification reaction. Similar to the parent PU, the functionalized carbon nanotube samples are soluble in highly polar solvents, such as dimethyl sulfoxide (DMSO) and N,N‐dimethylformamide (DMF). The functionalized acid amount and the grafted PU amount were determined by thermogravimetric analyses (TGA). Comparative studies, based on SEM images between the PU‐functionalized and chemically defunctionalized MWNT samples, also reveal the covalent coating character. Dynamic mechanical analysis (DMA) of nanocomposite films prepared from PU and PU‐functionalized MWNTs show enhanced mechanical properties and increased soft segment T_g. Tensile properties indicate that PU‐functionalized MWNTs are effective reinforcing fillers for the polyurethane matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Biobased chain extended polyurethane and its composites with silk fiber

The biobased chain extended polyurethane (PU) was synthesized by reacting castor oil based polyol with different diisocyanates [toluene‐2,4‐diisocyanate (TDI) and hexamethylene diisocyanate (HMDI)] and chain extender such as glutaric acid. Biocomposites have been fabricated by incorporating the silk fiber into both TDI‐ and HMDI‐based PUs. The effect of incorporation of silk fiber into TDI‐ and HMDI‐based neat PU on the physicomechanical properties such as density, surface hardness, tensile strength, and percentage elongation have been investigated. The dynamic mechanical properties and the thermal stability of neat PUs and the silk fiber incorporated PU composites have been evaluated. The TDI‐based neat PU has showed higher mechanical properties compared to HMDI‐based PU. The incorporation of 10% silk fiber into TDI‐ and HMDI‐based PU resulted in an enhancement of tensile strength by 1.8 and 2.2 folds, respectively. The incorporation of silk fiber into biobased chain extended PU increased the glass transition temperature (T_g) of the resultant biocomposites. The morphology of tensile fractured neat PUs and their biocomposites with silk fiber was studied using scanning electron microscope (SEM). POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Effects of TDI and FA‐703 on physico‐mechanical properties of polyurethane dispersion

A series of water dispersion polyurethanes dispersions (PUDs) were prepared by polyaddition reaction using isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), poly(oxytetramethylene) glycol (PTMG), dimethylol propionic acid (DMPA), and triol (trade name FA‐703). Various formulations were designed to investigate the effects of process variables such as TDI and FA‐703 on the physico‐mechanical properties of PUD. IR spectroscopy was used to check the end of polymerization reaction and characterization of polymer. Evolution of the particle size distribution, contact angle, T_g, molecular weight, viscosity, and mechanical properties of the emulsion‐cast films were significantly affected by variable content of TDI and FA‐703. Average particle size of the prepared polyurethane emulsions and contact angle decrease with increase of content of FA‐703 and TDI. Molecular weight, T_g, tensile strength, tear strength, hardness, viscosity and elongation at break increase with increase of content of FA‐703 and TDI. The increase of molecular weight, tensile strength, tear strength and elongation at break properties are interpreted in terms of increasing hard segments, chain flexibility, and phase separation in high content of FA‐703 and TDI‐based polyurethane. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of ABA‐type block copolymers of trimethylene carbonate and ϵ‐caprolactone

This paper describes the synthesis of a series of ABA‐type triblock copolymers of trimethylene carbonate and ?‐caprolactone with various molar ratios and analyses the thermal and mechanical properties of the resulting copolymers. The structures of the triblock copolymers were characterized by ¹H and ¹³C nuclear magnetic resonance spectroscopy, FT‐IR spectroscopy and gel permeation chromatography. Results obtained from the various characterization methods proves the successful synthesis of block copolymers of trimethylene carbonate and ?‐caprolactone. The thermal properties of the block copolymers were investigated by differential scanning calorimetry. The T_m and ΔH_m values of the copolymers decrease with increasing content of trimethylene carbonate units. Two T_gs were found in the copolymers. Furthermore, both of the T_g values increased with increasing content of trimethylene carbonate units. The mechanical properties of the resulting copolymers were studied by using a tensile tester. The results indicated that the mechanical properties of the block copolymers are related to the molar ratio of trimethylene carbonate and ?‐caprolactone in the copolymers, as well as the molecular weights of the resulting copolymers. The block copolymer with a molar composition of 50/50 possessed the highest tensile stress at maximum and modulus of elasticity. Block copolymers possessing different properties could be obtained by adjusting the copolymer compositions. Copyright © 2004 Society of Chemical Industry