Thermal properties of lignin-and molasses-based polyurethane foams

Lignin-and molasses-based polyurethane (PU) foams with various lignin/molasses mixing ratios were prepared. The hydroxyl group in molasses and lignin is used as the reaction site and PU foams with various isocyanate (NCO)/the hydroxyl group (OH) ratios were obtained. Thermal properties of PU foams were investigated by differential scanning calorimetry (DSC), thermogravimetry (TG) and thermal conductivity measurement. Glass transition temperature (T _g) was observed depending on NCO/OH ratio in a temperature range from ca. 80 to 120°C and thermal decomposition temperature (T _d) from ca. 280 to 295°C. Mixing ratio of molasses and lignin polyol scarcely affected the T _g and T _d. Thermal conductivity of PU foams was in a range from 0.030 to 0.040 Wm⁻¹ K⁻¹ depending on mixing ratio of lignin and molasses.     

Thermal properties of solvolysis lignin-derived polyurethanes

Thermal properties of polyurethane (PU) films prepared from solvolysis lignin (SL), polyethylene glycol (PEG) and diphenylmethane diisocyanate (MDI) were examined by differential scanning calorimetry and thermogravimetry. In the SL—PEG—MDI system, the SL content, the molecular weight (M_n) of PEG and the NCO/OH ratio were changed in order to control the thermal properties. Glass transition temperatures (T_g's) of the prepared PU's were dependent on the SL content, the M_n of PEG and the NCO/OH ratio. However, the T_g of PU was significantly influenced by the SL content: the increment of T_g was ca. 150 K when the SL content in PEG increased from 0 to ca. 50%. The decomposition of the PU's was markedly dependent on the content of SL. Other factors, such as the NCO/OH ratio and the M_n of PEG, are less dominant compared with the SL content. This fact suggests that the dissociation between the isocyanate groups and the phenolic OH groups in SL may be the major factor in the whole process of the thermal decomposition of the PU containing SL     

Interpenetrating polymer networks from polyurethanes and methacrylate polymers. I. Effect of molecular weight of polyols and NCO/OH ratio of urethane prepolymers on properties and morphology of IPNs

Two types of reinforced elastomeric interpentrating polymer network (IPN) were prepared by simultaneous polymerization and crosslinking in solution. The first type consisted of polyurethane-poly(methyl methacrylate) (PU/PMMA), and the second, of polyurethane-poly(methyl methacrylate-methacrylic acid) PU/P(MMA–MAA) of constant composition (90/10) and (80/20) by weight, respectively. The members of each type differed in the NCO/OH ratio of the PU prepolymer and the molecular weight (MW) of the polyol in the PU component because we wished to investigate systematically the effect of changing the NCO/OH ratio and MW of the polyol on the mechanical properties and morphology of the resulting IPNs. The mechanical properties, particularly the modulus of both tyes of IPN, increased with increasing NCO/OH ratio and decreased with increasing MW of the polyol in the PU. The morphology of the IPNs was studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Improved phase compatibility and decreasing extent of phase separation was observed in both types of IPN with increasing NCO/OH ratio and decreasing MW of the polyol used in the PU. These results may imply that improved interpenetration results from increasing the NCO/OH ratio and decreasing the MW of the polyol in the PU component. The fact that the effect is more pronounced with the type of PU-P(MMA–MAA) IPN can be rationalized as due to the additional hydrogen bonding between the carbonyl in the carboxyl groups and the urethane or urea groups in the PU component.     

Mechanical properties of solvolysis lignin-derived polyurethanes

In order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG-MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.     

Effect of NCO/OH ratio and Ce‐Zr nanoparticles on the thermo‐mechanical properties of hyperbranched polyurethane urea coatings

The present study describes the effect of NCO/OH ratio and addition of Cerium (Ce)‐Zirconium (Zr) mixed oxide nanoparticles on the properties of Hyperbranched Polyurethane Urea (HBPUU) Coatings. Initially a hydroxyl terminated hyperbranched polymer (HTBP) was synthesized through A₃ + CB₂ approach. The HTBP and Ce‐Zr nanopowder dispersed HTBP, both were reacted with hexamethylene diisocyanate (HDI) separately; at various NCO/OH eq. ratios to get different NCO terminated HBPU and HBPU/Ce‐Zr hybrid prepolymers. These prepolymers were used for the preparation of HBPUU and HBPUU/Ce‐Zr hybrid coating films through moisture curing. The techniques such as ¹H NMR, ¹³C NMR, FT‐IR, and XRD have been used for structural information while Dynamic mechanical and thermal analyzer (DMTA), Thermogravimetric analysis (TGA) and Universal testing machine (UTM) have been used for evaluation of thermo‐mechanical properties. The combined spectroscopic investigations results indicate the formation of HBPUU network with a degree of branching of 76% while FT‐IR deconvolution results indicates the formation of more hydrogen bonded structure with increasing NCO/OH ratio. The XRD and FT‐IR studies confirm the presence of Ce‐Zr mixed nanoparticles in the HBPUU hybrids. As per TGA and DMTA analysis the thermal stability, char residue, storage modulus (E', material stiffness) and glass transition temperature (T_g), increases with increasing NCO/OH ratio and Ce‐Zr nanoparticle loading in HBPUU coatings. In general, UTM data suggest that the tensile strength increases and per cent elongation at break decreases with increasing the NCO/OH ratio and addition level of nanoparticles in HBPUU coatings. Copyright © 2009 John Wiley & Sons, Ltd.     

Structure and properties of polyurethane/polyacrylate latex interpenetrating networks hybrid emulsions

Some new kinds of novel polyurethane (PU)/polyacrylate (PA) latex interpenetrating networks (LIPNs) were synthesized. Firstly PU dispersions were synthesized by self-emulsification polymerization. Then PU/PA LIPNs using PU dispersion as the seed were prepared by soap free emulsion polymerization. The effects of different PU/PA ratios, the blending method and the NCO/OH molar ratio of PU components on PU/PA LIPNs performance were also investigated. The structure and properties of PU/PA LIPNs such as mechanical properties, particle size, morphology of the surface were characterized by dynamic mechanical analysis, scanning electron microscopy, and dynamic light scattering. It was found that PU/PA LIPNs can markedly improve the water resistance and the mechanical properties of PU latex much more than those of PU/PA physical blends due to a great deal of interpenetrating and entangling between PU and PA latex. Moreover, the particle size of PU/PA LIPNs is related to the PA content and NCO/OH molar ratio of PU components: the higher the NCO/OH molar ratio in PU dispersions, the larger is the particle size of PU/PA LIPNs, and the average particle size of PU/PA LIPNs becomes larger with an increase in PA content.     

Thermal and viscoelastic properties of polyurethane-imide/clay hybrid coatings

This paper reports the synthesis and characterization of polyurethane (PU)-imide/clay hybrid coatings based on two types of polyester (PE) polyols (PE-1 and PE-2). PE-1 was prepared from neopentyl glycol (NPG), adipic acid (AA) and isophathalic acid (IPA), whereas PE-2 contains NPG, AA, IPA and TMP (trimethylol propane) with the same hydroxyl value 280 as PE-1. Cetyl trimethyl ammonium bromide (CTAB) modified montmorillonite (K10) was used as the organoclay for the synthesis of the hybrid coatings. The organoclay particles (3 wt%) were well-dispersed into the PE matrix by ultrasonication method. Then the isocyanate terminated PU prepolymers were synthesized by the reaction of polyester polyols with hard segments such as 2,4-toluene diisocyanate (TDI) or isophorone diisocyanate (IPDI) in different NCO/OH ratios e.g., 1.6:1, 2:1 and 3:1, respectively. Finally the thermally stable imide rings were incorporated into the PU backbone by complete reaction of excess NCO content present in the PU prepolymer with pyromellitic dianhydride (PMDA). The thermogravimetric analysis (TGA) shows a higher thermal stability for the PU-imide hybrid coatings with respect to the corresponding PU-imide films. A higher NCO/OH ratio has resulted in higher thermal stability. The activation energies of degradation were calculated by the Broido and Coats-Redfern methods, respectively. The dynamic mechanical thermal analysis (DMTA) results show an enhancement in the glass transition temperature value (T_g) for the clay containing hybrid coatings. The surface analysis by angle resolved X-ray photoelectron spectroscopy (AR-XPS) showed an enrichment of the soft segment towards the surface, and an enhancement in the hard segment composition in the hybrid coatings, resulted in phase mixing.     

Synthesis and characterization of hyperbranched polyesters and polyurethane coatings

Polyurethane (PU) coatings are widely used for variety of high‐performance applications in today's coating technology. The emerging hyperbranched polymers having three‐dimensional morphology have opened a new avenue to tailor the architecture of PU coatings. The methodology followed here is based on preparation of PU coatings from hyperbranched polyester. Initially, different hyperbranched polyester polyols (HPs) were synthesized by varying the hydroxyl‐terminated precursors that is, pentaerythritol, trimethylol propane or glycerol and keeping the diacid that is, adipic acid quantity constant at various mole ratios of 1:0.6, 1:0.8, 1:0.9, and 1:1, respectively. The obtained HPs were characterized by nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF)‐mass spectrometry, and Fourier transform‐infrared (FTIR) spectroscopy. The degree of branching and the quantity of different structural units present in the various HPs were calculated by integrating the quaternary carbon and carbonyl zone in ¹³C NMR spectroscopy. The extent of condensation in different HPs was also calculated from ¹H NMR spectra. Later on, NCO‐terminated PU prepolymers (NCO‐PU) were synthesized by reacting HPs with isophorone diisocyanate (IPDI) at NCO/OH ratio of 1.6:1. In the third step, the excess NCO content in the NCO‐capped PU prepolymers were reacted with atmospheric moisture and hyperbranched polyurethane (HPU) coatings were formed. The coating films were analyzed by FTIR and dynamic mechanical thermal analysis instruments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2673–2688, 2007     

偶联剂对丙烯酸酯改性聚氨酯聚合物接枝率和乳液性能的影响

合成了含双羟基的甲基丙烯酸甘油酯(GM)并将其作为偶联剂用于聚丙烯酸酯(PAC)对水基聚氨酯(PU)的改性.采用核磁共振、红外光谱和气相色谱等对GM进行了表征.分别以该双羟基GM和单羟基的丙烯酸羟乙酯(HEA)与异氰酸酯基(NCO)封端的PU预聚体进行反应以在PU分子链上引入双键,然后再与丙烯酸酯类单体通过自由基聚合制...     

Concept of hard clusters in the interpretation of thermal and mechanical properties of polyurethane and polyurethane acrylate networks

Polyurethane (PU) and polyurethane acrylate (PUA) networks based on hydroxyl-terminated polycaprolactone (PCL), 1,3-bis-2,2′(2-isocyanatopropyl)benzene (m-TMXDI), trimethylolpropane (TMP) for PU or hydroxyethyl methacrylate (HEMA) for PUA were synthesized. Glass transition temperature, T_g, dynamic mechanical relaxation, α, and equilibrium tensile modulus, E′, were measured to compare the two kinds of networks. To explain thermal and mechanical properties of networks, the concept of hard clusters has been introduced. PU networks exhibit a single-phase structure with modulus and T_g dependent on the concentration of elastically active network chains (EANC) per unit volume calculated by considering hard crosslink clusters. The rigidity of the clusters comes from small diisocyanate and trimethylolpropane units connected by urethane bonds. They are embedded in a continuous soft phase of macrodiol urethane. Physical equivalence between several kinds of network models has been demonstrated for full conversion of isocyanate-alcohol reaction. PUA networks exhibit thermodynamically one-phase structures that become a two-phase structure for high molar mass of macrodiol when the molar fraction of isocyanate groups increases. For those networks, the calculated modulus considering clusters based on polyacrylate chains seems to be a good way to approach the experimental value of the equilibrium modulus. For the same molar ratio of OH to NCO groups the range of dynamic moduli is larger for PUA than for PU. This difference can be explained by a different concentration of crosslinks in the networks. © 1996 John Wiley & Sons, Inc.     

Thermal Study of Polyurethane Elastomers Based on Biopitch–PEG–MDI System

Polyurethanes based on biopitch and PEG of distinct molecular masses (M _w 1500, 4000 and 6000) were synthesized using polymeric MDI. Different materials were obtained through syntheses using various biopitch content and NCO/OH ratio. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were used to determine their thermal properties. Variations of thermal stability were observed with amorphous and semicrystalline structures depending on the biopitch content and the NCO/OH ratio. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of Chain Length of Polyethylene Glycol and Crosslink Density (NCO/OH) on Properties of Castor Oil Based Polyurethane Elastomers

The equilibrium swelling study of polyurethanes (PU) was carried out in various solvents in order to calculate their solubility parameter. The kinetics of swelling and sorption have also been studied in 1,4‐dioxane at 30°C. The PU was synthesized by reacting a novel polyol (castor oil derivative and epoxy based resin, EpxR) and one of the polyethylene glycols (PEG 200, PEG 400, PEG 600) with different weight compositions, with a toluene diisocyanate (TDI) adduct (derived from toluene diisocyanate and R60 polyol). Different NCO/OH ratio viz. 1, 1.3 and 1.7 were employed in the study. The results were found to vary with the weight composition of polyol components, as well as the crosslink density of the samples. The sorption behavior is also found to vary with the molecular weight of polyethylene glycol employed in the preparations of the polyurethanes. Kinetic studies of swelling revealed that the sorption is anomalous in nature. The diffusion coefficient (D) increased with an increase in the NCO/OH ratio and decreased with an increase in chain length of polyethylene glycol. The sorption coefficient (S) decreased with an increase in crosslink density (NCO/OH) and increased with increasing polyethylene glycol (i.e., PEG 200, PEG 400, and PEG 600) moieties in the polyurethanes. The molecular weight between two crosslink points was calculated using the Flory Rehner equation (24), and hence, the number of chains per unit volume (N) and degree of crosslinking (ν) in all the samples were determined.     

聚醚聚氨酯/环氧树脂互穿网络聚合物的研究(Ⅱ)

合成了不同类型聚醚聚氨酯/环氧树脂(PU/EP)互穿网络聚合物(IPN),通过改变PU中聚乙二醇分子量、3OH/2OH及NCO/OH比值等,研究IPN组份间分子混合程度,采用电镜、动态力学分析及应力应变等测试方法表征。结果表明:聚乙二醇分子量降低及3OH/2OH、NCO/OH比的提高,可使相容性提高,材料力学性能增强。     

聚氨酯/聚苯乙烯互穿聚合物网络的研究

互穿聚合物网络形态和力学性能的研究已有报道^[1～3],但有关合成过程中分子量变化形态和性能的影响研究甚少。本文在动力学研究的基础上^[4],用GPC、DSC和Instron万能机研究了聚氨酯/聚苯乙烯互穿聚合物网络(PU/PSt-IPN)的分子量,玻璃化转变温度和力能,考察了分子量与相分离点之间的关系。     

Synthesis and thermal studies of flexible polyurethane nanocomposite foams obtained using nanoclay modified with flame retardant compound

This work presents thermal studies of nanocomposites based on the flexible polyurethane (PU) matrix and filled using montmorillonite organically modified with organophosphorus flame retardant compound. Flexible PU nanocomposite foams were prepared in the reaction carried out between reactive alcoholic hydroxyl and isocyanate groups with the ratio of NCO to OH groups equal to 1.05. The amount of an organoclay ranging from 3 to 9 vol% was added to the polyol component of the resin before mixing with isocyanate. The apparent density of PU foams was ranging from 0.066 to 0.077 g cm^?1. Thermal properties of the flexible PU nanocomposite foams were investigated by thermogravimetry and dynamical mechanical analysis. Glass transition temperatures (T _g) were defined as maximum peak on tanδ curve. Thermal decomposition was observed at 310–320 °C (calculated from the onset of TG curve). Tensile strength of the PU foams was determined using mechanical test. The microstructure of the nanoparticles and the composites was investigated by X-ray diffraction. Finally, it was confirmed that the thermal and mechanical properties of flexible PU nanocomposite depend on the amount of nanoclay.     

Investigation of the curing kinetics of polyurethane/nitrocellulose blends through FT-IR measurements

Polyester (HTPS) based polyurethane (PU) elastomers were currently established to be effective binders for high-energy composites with improved performances. Conventional PU binders are mostly non-energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, it may be introduced in PU-based compositions to overcome their performance drawback. Kinetic parameters must be specified in order to build PU binders with the most convenient and appropriate features. Therefore, the cure kinetics of polyester based polyurethane binder systems were investigated by Fourier transform infrared spectroscopy (FT-IR) isothermal method. The polyester prepolymer (Desmophen^® 1200) was cured with hexamethylene diisocyanate (HDI: Desmodur^® N100) at various molar ratios (R_[NCO]/[OH] = 0.6, 1, 1.25, and 1.5) and under different isothermal conditions (T = 60°C, 80°C, 100°C, and 120°C). In addition, the effect of the addition of nitrocellulose on the kinetics of polymerization of PU was investigated. The progression of the reaction was followed based on the decrease of the peak intensity of –NCO group at 2271 cm⁻¹ as a function of the reaction time. The curing kinetic model and the apparent activation energy (E_α) were determined by the use of Kamal autocatalytic model and Friedman isoconversional method, respectively.     

Polymers from renewable resources. XXI. Semi-interpenetrating polymer networks based on cardanol-formaldehyde-substituted aromatic compounds copolymerized resins and castor oil polyurethanes: Synthesis,structure, scanning electron microscopy and XRD

Substituted aromatic compounds incorporated–cardanol–formaldehyde novolac resins were synthesized by acid base catalyzed reactions. A number of improved high temperature stable interpenetrating polymer networks (semi-IPNs) were prepared by condensing novolac resins and polyurethanes prepared from castor oil and diisocyanates of varying NCO/OH ratio. The structure of these semi-IPNs were studied using various characterization techniques such as IR, nuclear magnetic resonance (NMR) spectra. The scanning electron microscopy of some of the semi-IPNs have been studied and the morphology has been examined. The samples were subjected to wide angle X-ray diffraction analysis. The degree of crystallinity (X_cr) was computed on the basis of the crystal defect concept, developed by Ruland and Vonk. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3117–3124, 1997     

Synthesis and properties of room temperature curable trimethoxysilane‐terminated polyurethane and their dispersions

The purpose of this research is to study the synthesis and characterization of stable aqueous dispersions of externally chain extended polyurethane/urea compositions terminated by hydrolyzable or hydrolyzed trialkoxysilane groups incorporated through secondary amino groups. These dispersions with excellent storage stability are substantially free from organic solvents which cure to water and solvent resistant, tough, scratch resistant, preferably light stable (non‐yellowing) silylated polyurethane (SPU) films. The films were characterized by FT‐IR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and water contact angle measurements, nanoindentation, gel content, water and xylene swellability tests. The properties of the films were discussed and correlated in detail by changing length of soft segment, diisocyanates, NCO/OH ratio and chain extender, ethylenediamine (EDA). From the results, it was found that the particle size and viscosity are lower whereas the gel content and thermal stability are higher for SPUs. Modulus, hardness and tensile properties of SPU films are superior compared to EDA‐PU film. Higher water contact angle and residual weight percentage of SPU films confirm silylation of PU by [3‐(phenylamino)propyl]trimethoxysilane (PAPTMS). Increase in NCO/OH ratios consumes more quantity of PAPTMS which makes PU with superior mechanical properties. Higher PAPTMS content in SPU results in effective crosslinking of the functional silanol groups formed by hydrolysis reaction of trimethoxysilane groups. Overall, SPUs synthesized at 1.4 NCO/OH ratio using Poly‐(oxytetramethylene)glycol (PTMG)‐2000 and isophorone diisocyanate (or) toluene‐2,4‐diisocyanate have excellent properties compared to SPUs prepared using PTMG‐1000 and at 1.2 and 1.6 NCO/OH ratios. SPUs prepared at 1.6 NCO/OH ratio are brittle due to higher crosslinking density. In addition, the crosslinking density of the films can be modified through silane end‐group modification to produce SPUs with a wide range of physical properties. Copyright © 2007 John Wiley & Sons, Ltd.     

Improvement of thermal and mechanical properties of poly(L‐lactic acid) with 4,4‐methylene diphenyl diisocyanate

In this study, the thermal and mechanical properties of biodegradable poly(L ‐lactic acid) (PLA) were improved by reacting with 4,4‐methylene diphenyl diisocyanate (MDI). The resulting PLA samples were characterized with Fourier transformation infrared spectrometer (FT‐IR). The glass transition (T_g) and decomposing (T_d) temperature of the resulting products were measured using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The tensile properties were also measured with a tensile tester. The results show that when the molar ratio of ? NCO to ? OH was 2:1, the T_g value can be increased to 64°C from the original 55°C, and the tensile strength increased from 4.9 to 5.8 MPa. This demonstrated that by reacting PLA with MDI at an appropriate portion, both the thermal and mechanical performance of PLA can be increased. Copyright © 2006 John Wiley & Sons, Ltd.     

Solution properties of NR/PU block copolymers by size‐exclusion chromatography and viscometry

Soluble block copolymers based on natural rubber and polyurethane oligomers derived from 1,3 butane diol and toluene diisocyanate were synthesized for the first time. The dilute solution properties of these block copolymers dissolved in tetrahydrofuran (THF) were studied by viscometry and gel permeation chromatography (GPC). The Mark–Houwink constants K and a of the block copolymer system were determined by the molecular weight data from GPC combined with the viscosity data. Both the values were found to be in the range usually given by flexible elastomers. The intrinsic viscosity values were found to decrease successively with a decrease in the NCO/OH ratio from 1.12 to 1.05. The unperturbed chain parameters, K_θ and B were determined from the viscosity data. The K_θ calculated was used to get the unperturbed end‐to‐end distance and radius of gyration of the block copolymer systems in THF. The viscosity data were also used to study the chain conformation in dilute solutions. It was found that the molecules adopt a compressed core and shell conformation in which the higher molecular weight component, NR, forms the shell, which compresses the PU core. All the block copolymers assume a compressed segregated core and shell model which changes to a partially segregated core and shell conformation, or partially Gaussian conformation, at the transition temperature located at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2104–2111, 2006