Sensitivity of proton NMR relaxation times in a HTPB based polyurethane elastomer to thermo-oxidative aging

Solid-state ¹H NMR relaxometry studies were conducted on a hydroxy-terminated polybutadiene (HTPB) based polyurethane elastomer thermo-oxidatively aged at 80 °C. The ¹H T₁, T₂, and T_1ρ relaxation times of samples thermally aged for various periods of time were determined as a function of NMR measurement temperature. The response of each measurement was calculated from a best-fit linear function of the relaxation time vs. aging time. It was found that the T_2,H and T_1ρ,H relaxation times exhibited the largest response to thermal degradation, whereas T_1,H showed minimal change. All of the NMR relaxation measurements on solid samples showed significantly less sensitivity to thermal aging than the T_2,H relaxation times of solvent-swollen samples.     

Preparation and application of glycolysed polyurethane integral skin foams recyclate from automotive wastes

Summary Glycolysis of isocyanate derived foams with glycol and amine mixture is a simple and economically attractive chemical recycling process. A mixture of diethylene glycol (DEG) and diethanol amine (DEA) is used as solvent system and sodium hydroxide as the catalyst. The obtained polyols can be completely reused in the formulation of integral skin foams in blend with virgin polyol.     

Preparation and characterization of waterborne polyurethane/silica hybrid dispersions from castor oil polyols obtained by glycolysis poly(ethylene terephthalate) waste

Castor oil polyols (COLs) have been synthesized from glycolyzed oligoester polyol in order to produce waterborne polyurethane (WPU)/silica hybrid dispersions. Soft drinks poly(ethylene terephthalate) (PET) bottles were depolymerized by glycolysis with different molar ratio of poly(ethylene glycol) ( PEG 400), in the presence of zinc acetate as catalyst. The obtained glycolyzed products were reacted with castor oil (CO) to attain castor oil polyols by the process of transesterification. Five castor oil polyols were used with hydroxyl values of 255, 275, 326, 366 and 426 mg KOH g⁻¹. Several castor oil-based, polyurethane/silica hybrid dispersions having soft segment content of 39.6% to 28.2% and two concentrations of SiO₂ nanoparticles (0.5 and 1.0) have been prepared.The incorporation effect of SiO₂ nanoparticles into the PU matrix and the hydroxyl functionality of the COLs on the thermal and mechanical properties of resulting polyurethane films has been examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TG) and measurement of the mechanical properties. The degree of phase separation (DPS) between oxide nanoparticles and hard segment, and particle size in the polyurethane, depends to some extent on nanosilica content and the hydroxyl functionality of the polyols employed in the polyurethane preparation process.Thermal stability of obtained hybrid materials depends on the hydroxyl functionality of the COLs and nanosilica content. The T_10% and T_50% (the temperature where 10 and 50% weight loss occurred) of WPU films decreased with the rise of OH functionality of castor oil polyols, caused by the increase of hard segment content. Glass transition temperature increased with increasing OH functionality and SiO₂ content. The hardness, adhesion and gloss quality of the polyurethane films were also determined with a view to assessing the effect of mole ratios of PET to glycol in glycolyzed products, the hydroxyl functionality and the SiO₂ content.     

含液晶基元聚氨酯对普通聚氨酯性能的影响

合成了一类既含有刚性液晶基元又含有柔性链段的主链型含液晶基元聚氨酯(LCPU)，以端羟基四氢呋喃-环氧乙烷共聚醚为基体材料，多异氰酸酯N-100为固化剂，探讨这类含液晶基元聚氨酯对聚氨酯弹性体力学性能的影响。结果表明，5种含液晶基元聚氨酯随着柔性链段长度的变化和在聚氨酯弹性体中加入比例的变化。表现出对聚氨酯弹性体力学性能的影响有较大的差异。与未改性聚氨酯弹性体相比，改性后聚氨酯弹性体共混物垃伸强座量大提高71％倍．断裂伸长率最大提高8．7倍．     

Effect of polyurethane structure on mechanical properties of nylon-66/polyurethane blends

A polyamide (nylon-66, N66) was blended with a series of polyurethanes (PU) based on different polyols or chain extenders. The effects of PU structure and content on the mechanical properties of the blends were investigated. The morphology of the polyblends was examined by scanning electron microscopy. The Izod impact strength of the blends increased with increasing PU content and showed a maximum value at the composition of 15 wt % PU. The effects of moisture content on the mechanical properties of the blends were also investigated. It was found that the water-toughened N66 could be further toughened by the addition of PU. Polyester-type PU rather than polyether type PU was recommended for the toughening of N66 because the blends containing the former showed higher tensile strength and Izod impact strength except at very low moisture (0.3 wt %) content. Carboxyl groups was introduced into the molecular chains of PU by using dimethylol propionic acid as chain extender replacing part of 1,4-butanediol. The blends containing PU with carboxyl groups showed a lower Izod impact strength than those without carboxyl groups in the structure of PU.     

原料及配方对单组分聚氨酯胶粘剂性能的影响

以不同性质的聚醚多元醇（210，220，330，3050）、TD1－80等为主要原料，分别采用一步法和预聚物法合成单组分聚氨酯胶粘剂，并用该胶粘结橡胶粉压制成铺垫材料。研究了不同多元醇、各多元醇的不同配比、合成工艺及不同异氰酸酯指数等因素对橡胶粉粘接料（以下简称粘接料）的影响。结果表明：以220和3050的1：1混合物，TDI为主要原料，用预聚物法合成的游离NCO含量为5％的单组分聚氨酯，其拉伸强度、扯断伸长率、耐水性、耐热性等均能满足橡胶粉粘结料的性能要求。     

Effect of 3-Aminopropyltriethoxysilane on polycarbonate based waterborne polyurethane transparent coatings

A series of waterborne polyurethane (WPU) dispersions modified with different contents of 3-aminopropyltriethoxysilane (APTES) were synthesized based on poly(1,6-hexyl 1,2-ethylcarbonate) diol (PHEC) and isophorone diisocyanate (IPDI), and the films were obtained by casting the dispersions on Teflon molds. Effects of APTES content on the particle size and viscosity of the dispersions were studied. The structure and properties of the resulting films were investigated by Fourier transform infrared spectroscopy, wide angle X-ray diffraction measurement, dynamic mechanical analysis, thermogravimetric analysis and mechanical testing. The experimental results showed that the incorporation of APTES played an important role in the enhancement of the water and toluene resistance and mechanical properties of the SPU films. Young's moduli and ultimate tensile strengths were improved from 8.0 to 451 MPa and 6.5–19 MPa respectively as the APTES content increased from 1 wt.% to 20 wt.%. The ability of scratch resistance was enhanced, when the content of APTES increased to 20 wt.%, the 3H pencil could not mar the surface. Moreover, the transmittance spectra indicated that the coatings showed high transparence.     

Effect of clay modifiers on the morphology and physical properties of thermoplastic polyurethane/clay nanocomposites

Thermoplastic polyurethanes (TPUs)/clay nanocomposites were prepared via melt processing using the ester type and the ether type TPUs and three differently modified organoclays (denoted as C30B, C25A and C15A) as well as pristine montmorillonite (PM). XRD and TEM results showed that the addition of C30B with hydroxyl group led to the nearly exfoliated structures in both TPUs. In the case of C25A and C15A clays, partially intercalated nanocomposites were obtained in both TPUs, where C25A showed better dispersion than C15A. Natural clay (PM) was not effectively dispersed in both TPUs. The tensile properties of nanocomposites with C30B were better than ones with the other clays. Higher tensile properties were obtained for ester type TPU than ether type TPU nanocomposites with all clays tested. Although the improvement in tensile properties decreased after the second extrusion of the nanocomposites, properties of the nanocomposite after first melt processing were still good enough for practical applications. Morphological changes induced by the addition of clays were analyzed using FTIR, DSC and rheological test results. Some clays were observed to cause demixing of hard and soft segments in the nanocomposites and location of clays in either soft segment or hard segment domains was also studied.     

Effect of crosslinking density on the physical properties of interpenetrating polymer networks of polyurethane and 2-hydroxyethyl methacrylate-teminated polyurethane

Interpenetrating polymer networks (IPNs) of 2-hydroxyethyl methacrylate-terminated polyurethane (HPU) and polyurethane (PU) with different crosslinking densities of the PU network were prepared by simultaneous solution polymerization. Dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) show that compatibility of component polymers in IPN formation depends on the crosslinking density of the PU network. Physical properties such as density and water absorption rely on the subtle balance between the degree of phase separation and the crosslinking density of the PU network. In spite of the occurrence of phase separation, the tensile moduli and tensile strength of the IPNs increase with the crosslinking density of the PU network. Morphological observation by scanning electron microscopy revealed different fracture surfaces between the compatible and incompatible IPNs. Surface characteristics of the IPNs, indicated as hydrogen bonding index and hard-to-soft segment ratio, are altered considerably by varying surface morphologies. Improved blood compatibility of IPN membranes is due to the variation of the hydrophilic and hydrophobic domain distribution.     

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions mixtures: Preparation and characterization

A series of newly developed UV-curable polyurethane coatings were prepared by blending multifunctional thiol- and ene-terminated polyurethane aqueous dispersions. The composition, structure, solution stability and mechanical properties of the title coatings were characterized in detail by FT-IR, photo-DSC and DMA measurements. It was found that the resulting polyurethane coatings showed good solution stability and high photopolymerization activity even after a long time (i.e. 1 month). The incorporation of a waterborne polyurethane chain into the both multifunctional thiols and ene monomers promoted their solution stability and avoided any reaction between thiols and ene groups as a result of their high reacting activity in non-aqueous systems. UV-cured films prepared by this method were found to exhibit excellent physical properties with improvements over what can be attained directly with current UV-curable urethane-acrylate based systems. This method allows for the preparation of high performance UV-curable polyurethane aqueous coatings based on thiol-ene chemistry systems.     

Effect of nano ZnO on the phase mixing of polyurethane hybrid dispersions

In the present study series of aqueous polyurethane (PU)/ZnO hybrid dispersions were prepared using dimethylolpropionic acid (bis-MPA) as an ionic center. For this, NCO terminated PU prepolymers with pendent acid groups were prepared first, then different concentrations of nano ZnO powder was incorporated into the PU matrix. The hybrid dispersions were prepared by adding required amount of triethylamine (TEA), water and chain extender. The prepared PU/ZnO hybrid dispersions were casted in a Teflon petri dish and the dried films were used for TGA, DMTA, SEM, gel content and contact angle measurements. The phase mixing behavior was studied from FT-IR peak deconvolution technique and DMTA analysis and the result suggests that phase mixing increases with ZnO content. The DMTA data suggest that the phase mixing and soft segment glass transition increases but storage modulus decreases with increasing with ZnO content. The FT-IR deconvolution result supports to the DMTA analysis. The coating properties like adhesive strength, water absorption, contact angle, gel content and corrosion resistance of the hybrid coatings were also evaluated.     

J-189双组分聚氨酯胶粘剂的研制

介绍了一种有机玻璃与涤纶带粘接用的双组分聚氨酯胶粘剂 ,按Q/HSY 10 7- 2 0 0 2标准测试 ,该胶室温粘接强度可达 2 .0kN·cm-1,12 0℃为 0 .4 5kN·cm-1,- 6 0℃为 2 .15kN·cm-1。在水中浸泡 72h后 ,粘接强度为 2 .10kN·cm-1,在航空煤油中浸泡 72h后 ,粘接强度为 2 .0 8kN·cm-1。探讨了合成聚酯的二元醇与三元醇物质的量比、催化剂用量及种类、贮存时间以及聚酯与固化剂质量比对性能的影响。实验结果表明 ,合成聚酯的二元醇与三元醇物质的量比为 1∶0 .32 ,复合催化剂用量为 1% ,聚酯组分与固化剂质量比为 1∶1时胶粘剂有良好的性能。     

Newly UV-curable polyurethane coatings prepared by multifunctional thiol- and ene-terminated polyurethane aqueous dispersions: Photopolymerization properties

A novel approach toward the preparation of newly UV-curable polyurethane coatings composed of multifunctional thiol- and ene-terminated polyurethane aqueous dispersions is presented. By a synergistic combination of polyurethane dispersions synthesis and thiol-ene chemistry, strategies for the preparation of newly UV-curable polyurethane coatings are developed. Photo-DSC, real-time FTIR, DMA and tensile tests measurements are used to investigate the photopolymerization and mechanical behaviors of newly UV-curable polyurethane coatings. The newly polyurethane coatings have 1.5 times higher polymerization rate and final 99% functional groups conversion in air conditions compared to current urethane-acrylate based UV-curable polyurethane dispersions coatings. UV-cured polyurethane films prepared by this method are also found to exhibit increase in Young's modulus and tensile strength at break by 25% and 10%, respectively. These experiment facts suggest that the incorporation of thiol-ene chemistry to the polyurethane dispersion coatings increase their polymerization rate, producing a high degree of cross-linking. This confirms the preparation of the targeted novel UV-curable polyurethane coatings and reveals the dramatic effect that changes in incorporation of thiol-ene chemistry can have on the photopolymerization behaviors of UV-curable polyurethane dispersions coatings systems.     

Effect of nano layered silicates on automotive polyurethane refinish clear coat

In the present investigation, effect of nano layered silicates on the properties of an automotive refinish clear coat based on polyurethane has been studied. Observation by means of X-ray diffraction (XRD) technique indicates the presence of a partially intercalated structure due to dispersion of nano layers in the polymer matrix. Some levels of hazing have been established by increasing the amount of nano-filler. The effect of nano-filled clear coat on the reflectance spectra of a metallic coated substrate has been studied under three different light sources using a goniospectrophotometer and compared with a blank clear coat to determine if it can be identified by human eye. Scratch and mar resistance tests showed significant improvement even 48 h after application, when there was no gloss reduction due to usage of nano-filler. Gloss retention was increased by about 10% in presence of only 3 wt% of nano-filler. In addition to some scratch and mar resistance tests, other standard tests like adhesion, impact and bending were performed to find out optimum nano-filler/polymer ratio.     

Hyperbranched polyurethane (HBPU)-urea and HBPU-imide coatings: Effect of chain extender and NCO/OH ratio on their properties

Effect of chain extender and NCO/OH ratio on the properties of hyperbranched polyurethane (HBPU)-urea and HBPU-imide coatings were examined. The NCO terminated pre-polymers were prepared by reacting the first (G1) and the second (G2) generation hyperbranched polyester polyols (HBP-G1 and HBP-G2) with excess diisocyanate. The excess NCO content of the prepolymer was reacted with different chain extenders viz., 3-aminopropyl triethoxysilane (APTES), pyromellitic dianhydride (PMDA) and N-hydroxyphthalimide (NHTM) to obtain HBPU-urea or HBPU-imide coatings. The structure–property relationships of the different coatings were investigated by FTIR peak deconvolution, and these data suggests the highest extent of hydrogen bonding interaction for PMDA-based coatings, which increases with increasing NCO/OH ratio. Film properties were evaluated by TGA, DMTA, UTM and contact angle measurements; these results were supported by FTIR deconvolution results. As per contact angle measurements, hydrophobicity of coatings increased by increasing NCO/OH ratio. The adhesive strength, abrasion resistance, alkali resistance, and gel content of the coatings were also evaluated.     

Polymer/layered clay nanocomposites: 2 polyurethane nanocomposites

A kind of novel polyurethane/Na⁺-montmorillonite nanocomposites has been synthesised using modified 4,4′-di-phenymethylate diisocyanate (M-MDI), modified polyether polyol (MPP) and Na⁺-montmorillonite (layered clay). Here, MPP was used as a swelling agent to treat the layered clay. Experimental results indicated that with increasing the amount of layered clay, the strength and strain-at-break increased. The storage modulus below the glass transition temperature of the soft segments in the polyurethane was increased by more than 350%. With increased loading of layered clay, the thermal conductivity decreased slightly rather than increased. This finding will provide valuable information for polyurethane industry.     

Effect of annealing on the properties of waterborne polyurethane adhesive containing urethane-based thickener

Different amounts of hydrophobically modified ethoxylated urethane-based thickener (HEUR) were added to improve the rheology of waterborne polyurethane adhesives. The thickened solid adhesive films were thermally annealed and characterised by IR spectroscopy, plate–plate rheology, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Hydrogen bonds played a key role in the thickening mechanism of polyurethane dispersions containing urethane-based thickener, along with ionic adsorption and micelles formation between hydrophobic groups. The adhesion properties were measured from T-peel test of leather/polyurethane adhesive/vulcanised styrene-butadiene rubber joints. Optimal results were obtained when water in the waterborne polyurethane adhesive (just before joint formation) was removed under open air, while forced air drying impeded the complete removal of water. On the other hand, the thermal annealing did not greatly affect the rheological and thermal properties of the thickened polyurethanes.     

氟、硅改性聚氨酯材料的研究进展

聚氨酯(PU)是一类用途广泛的工程材料,但用传统原料和方法制备的聚氨酯也存在诸多缺点,如耐热性、耐侯型不好,从而限制了它在工程技术领域的进一步应用。为此,聚氨酯的化学改性成为该领域的研究热点之一。作者综述了近年来氟、硅化学改性聚氨酯方面的研究进展,并对今后的研究发展进行展望。     

可紫外光固化聚氨酯乳液的合成与性能研究

对可紫外光固化的芳香族水分散性聚氨酯的合成与性能进行了初步的探讨。利用聚醚多元醇，甲苯二异氰酸酯和丙烯酸羟丙酯合成了稳定的可紫外光固化的水分散和性聚氨酯乳液。发现随着光照时间延长和丙烯酸羟丙酯用量的增加，所得聚氨酯薄膜的拉伸强度增加，断裂伸长率下降，在有机溶剂中的溶胀度也下降。