Polymers from renewable resources. VIII. Thermal properties of the interpenetrating polymer networks derived from castor oil–isophorone diisocyanate–polyacrylamides

Castor oil was reacted with isophorone diisocyanate varying the isocyanate/hydroxyl ratio to produce a number of polyurethanes (PUs). All the PUs were reacted with acrylamide and methacrylamide using ethylene glycol dimethacrylate as the crosslinker and benzoyl peroxide as the initiator. Thermogravimetric analysis of the polymers was conducted using a computer analysis method for assigning the kinetic mechanism. The degradation steps have been discussed in the light of the kinetic parameters. © 1995 John Wiley & Sons, Inc.     

Green polyurethane from dimer acid based polyether polyols: Synthesis and characterization

In this study, dimer acid (DA) obtained from waste soybean oil was used together with propylene oxide (PO) to obtain novel polyether polyols [prepolymers for polyurethanes (PUs)] through ring‐opening polymerization reaction. The average molecular weight of polyols was estimated by gel permeation chromatography and titration method. The substantial reaction between DA and PO was evident from FTIR and nuclear magnetic resonance spectroscopy. Subsequently, the polyols were reacted with chain extender [ethylene glycol, (EG)] and 4, 4 ‐ Diphenylmethane diisocyanate (MDI) to prepare green PUs. The effect of molar ratio variation of EG and MDI with a fixed amount of polyols was estimated by measuring hydrophobicity and mechanical strength of PUs. The molar ratio such as 1 : 4 : 5.7 of polyol : EG : MDI was found to exhibit maximum hydrophobicity and improved mechanical strength that were comparable with typical PU sample prepared from commercially available polyol, such as polypropylene glycol. FTIR spectroscopic analysis confirmed the chemical changes and possible crosslinking in PUs. Thermalgravimetric analysis and differential scanning calorimetry analysis also showed substantial thermal stability of the green PUs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41410.     

Polymers from renewable resources. I. Castor oil-based interpenetrating polymer networks: Thermal and mechanical properties

A number of polyurethanes (PUs) were synthesized by reacting castor oil with toluene-2,4-diisocyanate and hexamethylene diisocyanate and varying the NCO/OH ratio. All these polyurethanes were reacted with some acrylic monomers like ethyl acrylate, n-butyl acrylate, ethyl methacrylate, and butyl methacrylate using a crosslinker ethylene glycol dimethyl-acrylate and benzoyl peroxide as the initiator. The physicochemical properties of interpenetrating polymer networks (IPNs) are reported. Thermogravimetric analysis was used to study the thermal behavior of IPNs and the evaluation of kinetic parameters. Degradation mechanism has also been investigated. Some of the mechanical properties viz. tensile strength, shore-A hardness, elongation at break, etc. are also reported. © 1993 John Wiley & Sons, Inc.     

Preparation of multifunctional thiol‐ and acrylate‐terminated polyurethane: A comparative study on their properties in UV curable coatings

The multifunctional thiol‐ and acrylate‐terminated polyurethane (PU) has been successfully prepared for using as the main resin in the UV curable coatings. The structure and molecule weight of prepared PUs were analyzed by fourier transformed infrared spectroscopy (FTIR) and gel permeation chromatography, respectively. The results showed that the different terminal multifunctional groups have been grafted onto the PU and their difference in molecule weight was significant. Used as the main resin in coatings, the curing kinetic and percentage conversion of the different UV curing coatings system were investigated by real‐time FTIR method, and the effects of terminal functional groups and photoinitiator on the final conversion percentage and conversion rate were also compared. It is observed that the thiol‐terminated PU had higher conversion speed and final conversion percentage due to the remarkable effect of mercapto groups on reducing oxygen inhibition during UV curing process. The shrinkage, viscosity, and adhesion of UV curable coatings with thiol‐ and acrylate‐terminated PUs were also investigated and compared, and the results indicated that the former exhibited lower shrinkage and higher adhesion performances than the latter, along with the lower viscosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40740.     

Carbohydrate crosslinked biocompatible polyurethanes: Synthesis,characterization, and drug delivery studies

A series of novel polyurethanes (PUs) with carbohydrate crosslinkers was synthesized. The drug loading and release kinetics were studied by using lamotrigine as a model drug. The polymers were designed in such a way that the drug release was tailored by differences in the stoichiometry of polymers. All the PUs were characterized for thermal and morphological properties by using differential scanning calorimetry and thermogravimetric analysis and scanning electron microscope , respectively. The encapsulation of drug inside PU matrix was confirmed via Fourier transform ‐ infrared (FT‐IR) spectra and scanning electron microscope . The kinetics and release mechanisms were observed to be a function of stoichiometric parameters such as type of crosslinker, polyol/crosslinker ratio and polyol/chain extender ratio. All the PUs were observed to be non‐cytotoxic in normal lung cell line L132. The synthesized PUs exhibited good mechanical strength, tunable release rates and biocompatibility that can be utilized in biomedical applications like wound dressing, biomedical implants , and drug delivery carriers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42223.     

Synthesis and characterization of biodegradable polyurethanes based on L‐cystine/cysteine and poly(ϵ‐caprolactone)

Tunable biodegradable polyurethanes (PUs) with favorable mechanical properties were synthesized from 1,6‐hexamelthylene diisocyanate (HDI) as the hard segment, poly(?‐caprolactone) (PCL) as the soft segment, and L ‐cystine ester as chain extender. The structure of PUs was confirmed by FTIR and ¹H‐NMR. The results of differential scanning calorimeter, thermogravimetric analysis, dynamic mechanical analysis, and tensile test revealed that the thermal and mechanical properties of PUs were strongly influenced by the molecular weight of soft segment PCL. In the presence of glutathione, the disulfide group cleaved into thiols, realizing the PUs degraded and the molecular weight decreased. For PU [550], it remained only 50% of the original M_w. Evaluation of cell viability demonstrated the nontoxicity of the PUs, which facilitated their potential in biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preliminary study on the biodegradation of adipate/phthalate polyester polyurethanes of commercial‐type by Alicycliphilus sp. BQ8

Accumulation of polyurethane (PU) waste has increased considerably due to its extensive use. Even though many efforts are being carried out to develop more biodegradable PU, the use of these new materials is far from being commercially available. Here, we analyzed the susceptibility of solid polyester polyurethanes (PS‐PU) of commercial‐type, to biodegradation by Alicycliphilus sp. BQ8, a polyurethanolytic bacterial strain. Four polyester polyols were synthesized from dipropylene glycol (DPG) or diethylene glycol (DEG), and adipic acid (ADA) or phthalic anhydride (PHA), and were combined with either 4,4′‐ and 4,2′‐methylene diphenyldiisocyanate (MDI) or 2,4‐ and 2,6‐toluene diisocyanate (TDI). Synthesized polyols and PUs were characterized. PU biodegradation was assessed by the capacity of the polymers to support bacterial growth, and by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) spectroscopy, and gas chromatography/mass spectrometry (GC‐MS) analyses. Although all the synthesized PUs supported BQ8 growth, SEM analysis showed that PHA‐based PU foams were the most affected by bacterial growth. FTIR spectroscopy and GC‐MS analyses of bacterial treated PS‐PUs showed that they were attacked at ester and urethane groups, suggesting that esterase and amidase activities are involved. Extra‐cellular and membrane bound esterase activities were detected during the five days of analysis. Our results suggest that solid PHA‐based PUs might be more susceptible than ADA‐based PUs to microbial biodegradation in the environment. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42992.     

Physical properties and morphology of crosslinked polyurethane synthesized from para‐phenylene diisocyanate and polyether polyol

A series of crosslinked polyurethanes (PUs) were synthesized from para‐phenylene diisocyanate, 2‐(hydroxymethyl)‐2‐ethyl propane‐1,3‐diol (TMP), and butane‐1,4‐diol as the hard segments and poly(oxytetramethylene glycol) as the soft segments. The effects of TMP on the physical properties and microphase structure of the PUs were studied with dynamic mechanical analysis, Fourier transform infrared–attenuated total reflection spectroscopy, small‐angle X‐ray scattering (SAXS), and mechanical testing. We found that the storage modulus, hydrogen bonding with carbonyl groups, SAXS intensity, and hysteresis values decreased with increasing TMP; this indicated that the degree of microphase separation decreased with the increasing crosslinking density introduced by TMP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45241.     

Shape memory crosslinked polyurethanes containing thermoreversible Diels‐Alder couplings

Crosslinked polyurethanes (PUs) containing irreversible (allophanate) and reversible Diels‐Alder chemical bonds were synthesized using various diisocyanates (methylene diphenyl diisocyanate MDI, 1,6‐hexamethylenediisocyanate HDI) and poly(?‐caprolactone) ((PCL) with different molecular weights (M_n = 10 kg/mol, 25 kg/mol, 50 kg/mol) as diol component. The melting/crystallization of PCL and the reversible DA bonds acted as temperature‐activated switches for shape memory performances, while allophanate network provided the permanent crosslinks for these PUs. The reversible DA bonds were obtained by the reaction of diisocyanate‐ended prepolymers with furfurylamine (FA) followed by the addition of bismaleimide (BMI). The permanent crosslinks between the linear chains containing DA bonds were achieved using additional amounts of diisocyanates (MDI or HDI). The above reaction path was supported by infrared spectroscopic results and swelling experiments. Tensile mechanical and shape memory properties in tension of the PUs were determined and discussed as a function of composition and crosslink densities deduced from swelling and dynamic mechanical analysis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44145.     

Crystallization and thermal properties of biodegradable polyurethanes based on poly[(R)‐3‐hydroxybutyrate] and their composites with chitin whiskers

A series of biodegradable polyurethanes (PUs) were synthesized from hydroxylated bacterial poly[(R)‐3‐hydroxybutyrate], P[(R)‐HB]‐diol, as crystallizable hard segment and hydroxyl‐terminated synthetic poly[(R,S)‐3‐hydroxybutyrate), P[(R,S)‐HB]‐diol, as an amorphous soft segment, using 1,6‐hexamethylene diisocyanate, as non‐toxic connecting agent. The P[(R)‐HB] content was varied from 30 to 70 wt %. The resulting copolymers were characterized by FT‐IR, ¹H‐NMR, DSC, and TGA. The DSC data revealed that the melting of P[(R)‐HB] segment increases with increasing its own content in the PUs. The cold and melt crystallization are enhanced with increasing P[(R)‐HB] content. The TGA data revealed that the thermal decomposition mainly occurred via a single degradation step and the thermal stability slightly increased with increasing P[(R)‐HB] content. The non‐isothermal crystallization behavior of PU sample containing 40 wt % PHB with and without α‐Chitin whiskers was studied using DSC, and their kinetics data were investigated via the Avrami, Ozawa, and Z.S. Mo methods, respectively. Crystallization activation energy was estimated using Kissinger's method. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40784.     

Transport characteristics of carboxylic acids based chain extended PU membranes with n‐alkane penetrants

Castor oil based chain extended polyurethanes (PUs) have been prepared using citric acid and maleic acid as chain extenders. Molecular transport of n‐alkanes into prepared carboxylic acid chain extended PUs has been studied at different temperatures, viz., 25, 40, and 60°C using a gravimetric sorption method. The sorption (S), the diffusion (D), and the permeation (P) coefficients for n‐alkane penetrants have been calculated. Transport data are affected by the nature of the interacting solvent molecules, molar volume, solubility parameters, temperature, and the structural variation of the chain extended PUs. The temperature dependence of the transport coefficient has been used to estimate the kinetic parameters for the processes of diffusion (E_D) and permeation (E_P) from the Arrhenius plots. The van't Hoff relation was used to obtain enthalpy (ΔH) and entropy (ΔS) of sorption process. POLYM. ENG. SCI., 47:2057–2064, 2007. © 2007 Society of Plastics Engineers     

Development of polyurethane‐based sheets by phase inversion method for therapeutic footwear applications: Synthesis,fabrication, and characterization

It has been proved that polyurethane (PU) foam and viscoelastic PUs are offering better cushioning and shock absorption properties than other materials such as foam rubbers, polyethylene, ethylene vinyl acetate, and polyvinyl chloride which are used currently as insole materials in therapeutic footwear for diabetic and orthopedic patients to “offload” or redistribute high pressure under the foot. The aim of this research work was to prepare viscoelastic materials based on PUs having the highest degree of phase separation that provides for the elastomeric nature of these polymers. Polymer structures with a high concentration of amide groups can be made with the addition of hydrazine or a diacid hydrazide to a diisocyanate. We had prepared various PUs by chain extending the isocyanate‐terminated prepolymer with terepthalic dihydrazide, 5‐hydroxy isothalic dihydrazide, and 1,4‐butanediol. Polymers were developed into sheets by phase inversion method using dimethyl formamide as solvent and water as nonsolvent. To improve the mechanical properties of PU sheets the polymer solution was blended with polyester‐based PU Desmopan 8078 (CPU) in 1 : 1 ratio and the solution mixture was developed into sheet by the same method. Further PU sheets based on only CPU were also developed with various concentrations of PU. The synthesized PU and their blends with CPU were characterized by infrared spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, gel permeation chromatography, and dynamic mechanical analysis. Morphological characteristics of PU sheets were studied by scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Activation energies for the epoxy system BADGE n = 0/m‐XDA obtained using data from thermogravimetric analysis

In this article we study the kinetics of thermal degradation of the epoxy system BADGE n = 0/m‐XDA using different kinetic methods with data from thermogravimetric analysis (TGA) in dynamic conditions. Activation energies obtained using different integral methods (Flynn‐Wall‐Ozawa and Coats‐Redfern Methods) are in good agreement with the value obtained using the Kissinger method (204.44 kJ/mol). The solid‐state decomposition mechanism followed by this epoxy system is a decelerated R_n type (phase boundary controlled reaction). We have also calculated activation energies using the Van Krevelen and the Horowitz‐Metzger methods. These last methods corroborate the decelerated behavior. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 776–782, 2001     

Synthesis and characterization of permanently antistatic polyurethanes containing ionic liquids

An in situ embed ionic liquid method is designed and employed in thermoplastic polyurethanes (PUs). Unlike the traditional physically incorporated antistatic polymers where conductive fillers do not firmly combined with the matrix. This permanently antistatic PUs are successfully synthesized by using a novel polyester diol bonded with ionic liquids (ILs), which are obtained by an esterification. The ILs and novel polyester polyol are successfully synthesized and subsequently characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectrum (¹H NMR), respectively. The effects of ILs content, temperature, and relative humidity (RH) on the surface resistivity of PUs are studied by surface resistivity tests. It is found that the surface resistivity of PUs dramatically decreases with the increment of ILs and are insensitive to surrounding environment. The surface resistivity of PUs with 5.96 wt% ILs reaches 10¹⁰ Ω cm^?2 order of magnitude. The crystalline properties, thermal decomposition behaviors and mechanical properties of synthesized PUs are investigated by X‐ray diffraction (XRD), thermal gravimetric analysis (TGA) and tensile test respectively. The crystallinity of PUs with ILs is lower than that of pure PUs. Moreover, we also investigate the effect of ILs on the surface morphology of the PUs. POLYM. ENG. SCI., 56:629–635, 2016. © 2016 Society of Plastics Engineers     

Synthesis and characterization of methoxypolyethyleneglycol and lauric acid grafted novel polyurethanes for controlled release of nifedipine

Novel polyurethanes (PUs) grafted with methoxypolyethyleneglycol (mPEG) and lauric acid (LA) were synthesized by solution polymerization using dibutyl tin dilaurate as a catalyst, taking different molar ratios of LA‐trimethylol propane (LA‐TMP) with respect to mPEG‐trimethylol propane (mPEG‐TMP). The polymers obtained were characterized by Fourier transform infrared spectroscopy and gel permeation chromatography to confirm, respectively, the PU formation and molecular weight. Moderate molecular‐weight PUs were obtained, and nifedipine (NFD)‐loaded microspheres were prepared by solvent evaporation method. The size of the microspheres as measured by laser light scattering technique ranged between 10 and 50 μm. An increase in the size of particles was observed with an increasing molar ratio of mPEG‐TMP with respect to LA‐TMP. The % encapsulation efficiency was found to vary between 65 and 92. The surface morphology of microspheres as studied by scanning electron microscopy revealed the spherical nature of the particles with wrinkles on their surfaces. Crystalline nature of the drug in the microspheres after loading was studied by X‐ray diffraction technique. The release of NFD through the matrix microspheres was investigated in pH‐7.4 phosphate buffer. An increase in release rate was observed with increasing molar ratio of mPEG‐TMP with respect to LA‐TMP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Segmented MDI/HMDI‐based polyurethanes with lowered flammability

A series of segmented polyurethanes (PUs) based on 4,4′‐diphenylmethane diisocyanate and 1,6‐hexamethylenediisocyanate; polyoxypropylenediol (POPD); and low‐molecular chain extenders, 1,2‐propanediol or 3‐chloro‐1,2‐propanediol was obtained by solution polymerization and characterized by GPC and microscopic methods. Spherical aggregates with diameter of about 200 nm, arranged in a quasi‐linear mode, were observed by SEM technique; further investigations by the TEM method revealed hard‐segment domains of longitudinal shape, with length of about 5–10 nm, showing some features of the arrangement along a “director” axis. The process of thermal decomposition was monitored by thermogravimetric analysis in both dynamic and isothermal mode; to gain a deeper look into the mechanism of decomposition, kinetic analysis was performed. First, isoconversional methods showed a multistep decomposition route, as the value of (apparent) energy of activation changes from about 150 kJ/mol in the first step up to about 350 kJ/mol in the third step, which corresponds to the energy of dissociation of C? C bonds and leads to a char (carbonaceous) residue. Further calculations by means of the linear regression method revealed that kinetic model functions describing the degradation process of PU that does not contain chlorine were Bna → An → Fn, whereby for chlorine‐containing polyurethanes the CnB → An → An model was applied as best fit. Volatile products were investigated by pyrolysis–gas chromatography/mass spectrometry method at 770°C; the low molecular weight decomposition products, which were identified, indicate that the depolymerization process, yielding mainly diols and isocyanates through breakage of urethane bonds, prevailed during the thermal treatment under pyrolytic conditions. Finally, the mechanism of thermal degradation of modified polyurethanes with lowered flammability was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3214–3224, 2004     

Thermoreversible supramolecular polyurethanes with self‐complementary quadruple hydrogen‐bonded end groups

In this article, a new type of strongly dimerizing 2‐ureido‐4‐[1H]‐pyrimidinone (UPy) with amine group is synthesized and then used as end‐group to prepare a novel series of supramolecular polyurethanes (PUs). The effects of strong and well‐defined hydrogen bonding on material properties of PUs are studied. In these PUs, the UPy groups consequently serve as thermoreversible associations or the “hard blocks” and the bi‐functional PU chains act as the “monomers.” This theoretical hypothesis is proved by the results of dynamic mechanical thermal analysis (DMTA) and rheological test. Thermal analysis shows that the strong hydrogen bonds from end groups restrict the formation of their microcrystalline domains. The supramolecular PUs exhibit good mechanical performance and their self‐assemble mechanism is discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Environment‐friendly chemical recycling of aliphatic polyurethanes by hydrolysis in a CO2‐water system

In order to develop a chemical recycling system of polyurethanes (PUs), environment‐friendly hydrolysis of two types of aliphatic PUs was studied under pressured CO₂ in water, in which the carbonic acid generated from CO₂ acted as an acid catalyst. Two PUs, namely H‐PU or I‐PU, were synthesized starting from 1,4‐butanediol and 1,6‐hexamethylene diisocyanate or isophorone diisocyanate, respectively. The hydrolysis of PUs depended on the experimental conditions, such as the temperature and CO₂ pressure. As a result, 98% of H‐PU and 91% of I‐PU were successfully hydrolyzed under the typical conditions of 190 °C for 24 h at 8.0 MPa CO₂. The reaction mixtures afforded 1,4‐butanediol and diamines without the formation of any byproducts. Both of these raw materials generated from the originated PUs by selective hydrolytic cleavage of the urethane linkages, and they were easily isolated in high yields simply by evaporation of the water‐soluble components within the reaction mixture. By comparing the results of the two aliphatic PUs with those of an aromatic PU (M‐PU), the hydrolyzability was found to decrease in the order H‐PU, I‐PU, and M‐PU. The difference can be ascribed to the hydrophilicity of the aliphatic or aromatic groups connected to the urethane moieties at the terminals of PUs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45897.     

Shape memory segmented polyurethanes: dependence of behavior on nanocellulose addition and testing conditions

The response of synthesized shape memory segmented polyurethanes (PUs) was affected by the addition of cellulose nanocrystals, as well as by the various conditions selected to carry out thermomechanical cyclic tests. The PUs were synthesized from an α‐hydro‐ω‐hydroxy‐poly(ethylene oxide), tolylene‐2,4‐diisocyanate and 1,4‐butanediol as chain extender. Nanocomposites were prepared by mixing a suspension of cellulose nanocrystals in N,N‐dimethylformamide with the thermoplastic PU dissolved in the same organic solvent. The thermal properties of the neat PU and resulting composites were examined using differential scanning calorimetry. It was found that cellulose addition increases the PU soft segment melting and crystallization temperatures and the degree of crystallinity of this phase. Shape memory behavior was studied using cyclic thermal tensile tests. Both neat PU and composites exhibit shape memory properties, with fixity and recovery values that depend on heating temperature, imposed deformation, deformation rate and nanofiller addition. Copyright © 2011 Society of Chemical Industry     

Effect of soft segment length on properties of hydrophilic/hydrophobic polyurethanes

Polyurethanes (PUs) were prepared from 4,4′‐diphenylmethane diisocyanate and various molecular weights of poly(tetramethylene glycol) and polydimethylsiloxane. The physical properties of these polymers were determined using Fourier transform infrared spectroscopy and through calculation of their swelling ratios. The thermal properties were investigated through thermogravimetric analysis and dynamic mechanical analysis. The blood compatibility of each polymer was determined by calculating its relative index of platelet adhesion (RIPA). Domain separation of the resulting PUs occurred during polymerization because of the immiscibility of the hydrophilic and hydrophobic polyols. The hydrophilic/hydrophobic domain‐separated structure affected the surface tension through the formation of hydrophilic and hydrophobic domains of the PU, which reduced the adhesion of blood platelets onto the materials. The PU(PDMS/PTMO1000) = 75/25 sample, with its RIPA of 0.34, appears to be suitable for biomedical applications as a blood‐compatible material. Copyright © 2007 Society of Chemical Industry