Surface Composition and Morphology of Particles Dried Individually and by Spray Drying

This study investigates how the morphology of spray-dried particles is related to the formulation and properties of the components in the formulation. Further, the scale effects in comparisons of levitation-dried single particles and spray-dried particles in a lab-scale spray dryer have been addressed. The Drying Kinetics Analyzer^TM generates single particles from a levitated drop under simulated spray-drying conditions. A set of surface-active polymers (bovine serum albumin, hydroxypropyl methyl cellulose, and triblock co-polymer Poloxamer), in combination with lactose, were analyzed for their dynamic surface properties in solution, and their effect on particle morphology and surface composition were determined by low-vacuum SEM and XPS analyses. The morphology obtained in spray drying was reproduced in the single-particle drying. The surface compositions were also similar, but higher levels of surface-active materials were found at the surface of the single particles as compared to the spray-dried particles. Further, the adsorption rate of surface-active compounds at the drop surface estimated by dynamic surface tension was found to be an important parameter to estimate the surface composition at different drying scales. The particle morphology was primarily determined by the surface rheological properties of the feed solution and, to a lesser extent, by the surface composition.     

Synthesis of surface-modifying macromolecules for use in segmented polyurethanes

Polyurethanes are one of the most important classes of thermoplastic elastomers and have been widely used in medical-device manufacturing as well as in other applications. However, their function can be limited, particularly under environmental conditions that render them susceptible to hydrolysis. Using polymeric additives that are hydrolytically stable may be one approach to modifying the surface of polyurethanes for the purpose of improving their hydrolytic resistance without compromising their structural features. In this paper, the development of a series of novel fluorine-containing polyurethane surface modifying macromolecules (SMMs) is described and their synthesis conditions are investigated. The material structure and mixing properties of the synthesized SMMs with base polyurethanes was dependent on the reactant stoichiometry and concentration for the SMM components, as well as the reaction temperature and the amount of catalyst used in the SMM synthesis. This study describes the use of low surface energy components (fluorinated tails) which showed selective migration towards the surface when added to a polyester-urea-urethane. These novel macromolecules generated a nonwettable surface while not significantly altering the apparent bulk structure of the base polymer. The advancing and receding contact angle results indicated that the surface of these modified polyurethanes showed wettability characteristics similar to that of Teflon. ^TM The differential scanning calorimetry thermograms for the mixtures of the SMM with the polyurethane showed that, at 5% w/w SMM in the base polyurethane, the thermal transitions were similar to that of the native base polyure-thane, indicating that the additives had no detectable effect on the polyurethane structure. © 1996 John Wiley & Sons, Inc.     

Physical and mechanical behavior of sterilized biomedical segmented polyurethanes

Changes in the physical and mechanical behavior induced by two sterilization methods, gamma irradiation and ethylene oxide, were determined on two commercial medical-grade segmented polyurethanes. The two materials have different chemical composition: one is an aromatic poly(ether urethane urea), Biospan^TM, and the other an aliphatic ether-free polyurethane, Chronoflex^TM. Properties before and after sterilization procedures were compared resulting in specific structural changes for each formulation. The thermal and mechanical properties were examined using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), stress–strain measurements, and its hysteresis cycle. Molecular weight measurements were performed by gel permeation chromatography (GPC). Sterilized Biospan samples showed a decrease in the soft-segment glass transition temperature (T_g,s) and an increase in the soft segment crystallization heat along the quenching process. Sterilized Chronoflex materials showed the opposite behavior. The hysteresis percent and residual strain percent increased after sterilization. The same effect was observed when irradiation dose and strain level increased. Surface analysis performed by scanning electron microscopy showed magnification of original surface defects after sterilization. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1193–1203, 1997     

Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings

Novel two pack polyurethane wood finished coatings are prepared from renewable sources, such as vegetable oil based fatty acid and dimer fatty acid. In actual experimental part oleic acid was reacted with diethanolamine to obtain amide which was on condensation polymerization with dimer fatty acid converted into the polyesteramide polyol. These are all being used to prepare polyurethanes. The functional and structural elucidation of dimer fatty acid based polyesteramide and diethanolamide were carried out by end group analysis, spectral studies such as FTIR and ¹H NMR. Average molar masses of the polyesteramide were estimated by gel permeation chromatography (GPC). The polyesteramide was used in the preparation of wood finished polyurethane coatings by reacting it with aromatic diisocyanates. Thermogravimetric analysis (TGA) was used to study the thermal behavior of coatings. Physico-chemical and coating properties of the coatings were investigated by using standard methods. The results indicated that the bio-based wood finished PU coatings provided good mechanical, weather resistance as well possessed adequate coating properties for wood surface protections.     

低表面能UV固化水性柔感塑料涂料的研究

将季戊四醇三丙烯酸酯（PETA）和聚二甲基硅氧烷（PDMS）引入水性聚氨酯的主链,制得硅氧烷改性的UV固化水性聚氨酯乳液,通过FTIR红外光谱对乳液的结构进行表征。将该乳液与助剂复配,制得水性塑料涂料,并对涂层的固化动力学和表面性能进行研究。与未改性的涂料相比,硅氧烷改性的UV固化水性涂料具有良好的耐水性和耐溶剂性,同时保留了优良的手感,可用作水性柔感塑料涂料。     

DETDA在浇注型聚氨酯弹性体中的应用研究

采用芳香二胺固化剂DETDA、聚醚多元醇和TDI为主要原料,合成出了透明性良好的聚氨酯弹性体制品。讨论了异氰酸酯种类、混合比例和催化剂等对操作工艺和制品性能的影响。结果表明,采用DETDA作为固化剂合成的聚氨酯弹性体制品具有优异的力学性能、耐磨性和回弹性。     

超高韧性聚氨酯复合材料性能影响因素

通过研究异氰酸酯指数(R值)、外加剂掺量、以及养护龄期对超高韧性聚氨酯复合材料性能的影响,优化材料制备技术,得到超高韧性聚氨酯复合材料的最佳制备技术.结果表明:R值决定着聚氨酯材料的软硬段比例,对力学性能影响较大,外加剂的掺入降低了材料的孔隙率,提高了材料致密度,聚氨酯材料的后熟化过程在7 d左右;超高韧性聚氨酯复合材...     

Star‐shaped amphiphilic block polyurethane with pentaerythritol core for a hydrophobic drug delivery carrier

To obtain polyurethane micelles with excellent stability as a drug delivery carrier, star‐shaped amphiphilic block polyurethane (SAPU) was successfully synthesized by the ‘arm‐first’ method, using methoxypoly(ethylene glycol) and poly(ε‐caprolactone) diol as soft segments, hexamethylene diisocyanate as hard segments and pentaerythritol as the core. The structure of the SAPU was characterized by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy and gel permeation chromatography. The micellization behaviour and micelle properties of SAPU were measured by the pyrene fluorescence probe technique, ¹H NMR, SEM and dynamic light scattering. The results indicated that SAPU could self‐assemble to form nanomicelles in aqueous solution and that the micelles showed excellent stability upon dilution and storage. Indometacin as a model drug could be incorporated into SAPU micelles and be released sustainedly. Meanwhile, the hydrophilic segment content and the molecular weight of SAPU had effects on the micelle properties. In addition, SAPU exhibited good cytocompatibility estimated by methylthiazole‐tetrazolium assay. © 2016 Society of Chemical Industry     

Preparation of silica aerogel from oil shale ash by fluidized bed drying

The silica aerogel with high specific surface area and large pore volume was successfully synthesized using oil shale ash (OSA) via ambient pressure drying. The oil shale ash was burned and leached by sulfuric acid solution, and then was extracted using sodium hydroxide solution to produce a sodium silicate solution. The solution was neutralized with sulfuric acid solution to form a silica gel. After washing with water, the solvent exchange with n-hexane, and the surface modification with hexamethyldisilazane (HMDZ), the aged gel was dried by fluidization technique and also using a furnace to yield silica aerogels. The physical and textural properties of the resultant silica aerogels were investigated and discussed. The results have been compared with silica aerogel powders dried in a furnace. From the results, it is clear that the properties of silica powders obtained in fluidized bed are superior to that of powders dried in the furnace. Using fluidization technique, it could produce silica aerogel powders with low tapping density of 0.0775 g/cm³, high specific surface area (789 m²/g) and cumulative pore volume of 2.77 cm³/g.     

Dry‐peelable temporary protective coatings from waterborne self‐crosslinkable sulfourethane–silanol dispersions

Novel temporary protective coatings were prepared by the addition of release additives to waterborne polyurethane dispersions. New types of self‐crosslinkable sulfourethane–silanol (SUS) dispersions were utilized as the peelable coatings. These dispersions are stable, low‐volatility organic chemical (VOC) waterborne dispersions that spontaneously crosslink upon drying without extra additives or processing steps. Tensile strengths up to 6000 psi with elongations between 300–600% were obtained for the crosslinked films. The adhesion of the films to a variety of substrates can be controlled by the addition of hydrophilic additives, including glycerol, oligomers of glycerol, and poly(ethylene glycol) derivatives. Alternatively, hydrophobic additives that are water dispersible, such as paraffin waxes and sulfated castor oil, can also be used to control adhesion. In addition, this technique can be utilized for the release of films derived from a wide variety of waterborne urethane dispersions, including carboxylated polyurethane ureas. The removable coatings are useful for the temporary protection of plastic surfaces during thermoforming processes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1443–1449, 2004     

Surface rearrangement of tailored polyurethane-based coatings

Polyurethane coatings with different network composition were prepared from an oligomeri diol, a diisocyanate, and a low molecular weight triol. The glass transition temperature of the network was tuned by the ratio of diol and triol and the composition (aromatic or aliphatic) of the diisocyanate. All coatings were studied for their bulk properties as well as their surface properties. It was found that by the addition of a fluorinated additive the surface free energy of the coating was lowered by approximately 15 mN·m⁻¹, leaving the bulk properties intact. It was also shown that these polyurethane coatings are able to adapt their surface free energy in a reversible manner when exposed to water. The magnitude and rate of surface rearrangement is strongly dependent on the network density of the coating.     

Nano-adsorbents control surface properties of polyurethane

Additives are minor but critical components that polymers need for processing and applications. However, these additives may also have adverse effects, e.g. for polymeric biomaterials, leaching additives can change surface properties, and may lead to poor biocompatibility. How to use additives yet keep them from detrimental behaviors is a challenging issue. Diffusion barriers may be used to slow down the additive migration but difficult to stop it. In this paper, we introduce the concept of “nano-adsorbents” in polymers. These nano-adsorbents confined the additives within the polymers by thermodynamically interacting with them. While the additives are still present in polymers to provide intended functions, they are thermodynamically constrained from free migration to the surface. Nano sized-fillers were selected due to their high surface to volume ratio. This new usage of nano-fillers for polymers was demonstrated with a biomedical polyurethane and a surface coated nanoclay that thermodynamically attracts the additive in the polyurethane.     

城轨车辆用聚氨酯半光漆光泽稳定性研究

以丙烯酸树脂为基料,制得了适合城轨车辆使用的聚氨酯半光漆.研究了不同丙烯酸树脂、不同CAB助剂、不同涂膜干燥方式及不同涂膜厚度对半光漆光泽稳定性的影响.通过SEM和IR等检测手段对涂料性能进行了表征.结果表明,当选用某高羟值树脂和低羟值树脂搭配使用时,半光漆具有较好的光泽稳定性,当助剂CAB381和CAB551搭配使用时,此时消光粉有最佳的定向效果,当采用常温晾1h、60℃烘干1h的干燥工艺及涂膜厚度控制在40～60μm时,此时涂料光泽波动最小.     

Structural-mechanical properties of corundum bodies containing a porous filler

Conclusions We studied the structural-mechanical properties of granular corundum bodies in relation to the form, amount of additives consisting of surface active substances, and the type of porous filler.It was shown that a positive influence on the forming properties of the bodies based on spherical corundum and porous corundum briquet is exerted by the incorporation of technical lignosulfonate, and moreover it is most advantageous to use 0.5% solution for the spherical corundum and 2% solution for the briquet. An addition of GKZh-11 in amounts of 0.05% is desirable only for bodies based on spherical corundum. The addition of these agents increases the plasticity of the bodies on account of reducing the internal friction between the particles, and enables us to obtain articles with good properties.Translated from Ogneupory, No. 8, pp. 10–13, August, 1987.     

Selective pyrolysis of polystyrene to that with a desired low polymeric degree

To obtain low polymeric polystyrene (PS), pyrolysis of high polymeric PS in solution was studied in the temperature range from 290 to 400°C by using additives or acid catalysts. The low polymeric PS targeted here was that with average molecular weight of 10⁴. When the feed PS was pyrolyzed in tetralin by adding sulfur or diphenyl disulfide, the molecular weight of PS decreased greatly, even at lower temperatures, and the desired low polymeric PS was formed in a relatively large amount at the temperatures below 350°C. The degradation behavior was able to be explained in terms of a random polymer chain scission mechanism initiated by sulfur radicals formed from the additives. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2299–2305, 1998     

Influence of an oligomer polyol and monomers on the structure and properties of core–shell polyurethane–poly(n‐butyl acrylate‐co‐styrene) hybrid emulsions

The free‐radical polymerization of alkenyl‐terminated polyurethane dispersions with styrene and n‐butyl acrylate was performed to obtain a series of stable polyurethane–poly(n‐butyl acrylate‐co‐styrene) (PUA) hybrid emulsions. The core–shell structure of the emulsions was observed by transmission electron microscopy, and the microstructure was studied by ¹H‐NMR and Fourier transform infrared spectroscopy. The effects of the poly(propylene glycol)s (number‐average molecular weights = 1000, 1500, and 2000 Da) and the mass ratios of polyurethane to poly(n‐butyl acrylate‐co‐styrene) (PBS; 50/50, 40/60, 30/70, 20/80, and 10/90) on the structure, morphology, and properties of the PUAs were investigated. The average particle size and water absorption values of the PUAs increased with increasing of PBS content. However, the surface tension decreased from 34.61 to 30.29 mN/m. PUA‐2, with a bimodal distribution, showed Newtonian liquid behaviors, and PUA‐3 showed a great thermal stability, fast drying characteristics, and excellent adhesion to packaging films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43763.     

A novel alkoxysilane‐modified high solids hydroxyl acrylic polyurethane: Preparation and surface properties

Alkoxysilane‐modified high solids hydroxyl acrylic polyurethane was prepared by solution polymerization. Its structure, surface, and thermal properties were investigated by ¹H NMR, device of contact angle, thermo gravimetric analysis (TGA), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS). Research showed that alkoxysilane modified high solids hydroxyl acrylic polyurethane has superior properties that can be used for automotive paints. The contents of silicone in the alkoxysilane‐modified high solids hydroxyl acrylic polyurethane were 1.25, 1.5, 2, and 2.5 wt %. In this study, γ‐methacryloxypropyltrimethoxysilane (MPTS) was chosen as the modifier. Results showed that the contact angles of water and surface roughness on the film of MPTS modified high solids hydroxyl acrylic polyurethane increased, and thermal stability of the film at high temperatures improved with the increasing of the silicone content in the resins. MPTS modified high solids hydroxyl acrylic polyurethane with 2.5 wt % silicone content had better water resistance, better acid resistance, higher hardness, and excellent weatherability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1866–1871, 2006     

Syntheses and properties of fluorinated phosphate acrylates used for UV-curing coatings

The acrylated perfluoroalkyl phosphates (PFPA I and PFPA II) used as an oligomer and monomer, respectively, for UV-curing systems were synthesized and characterized with ¹H NMR and FTIR spectra. The photopolymerization behavior was investigated by using photo-DSC analysis, showing that both acrylates were photopolymerized quickly to a moderate final unsaturation conversion at the presence of a photoinitiator. The limiting oxygen indices of the UV-cured pure films were determined to be over 35. The surface properties of UV-cured polyurethane films added PFPAs, respectively, as additives were investigated by measuring the contact angles. The results showed that the addition of a small amount of PFPA I or PFPA II efficiently led to the increases in the contact angles, and the decreases in the surface tension. The X-ray photoelectron spectroscopy analysis confirmed that the film surface was enriched with fluorinated species.     

Improvements in the drying process for wet-spun chitosan fibers

Chitosan fibers were wet spun from a 6% by weight chitosan in 3% by volume acetic acid solution. The fibers were collected as a 20 filament yarn intended for use as a chaff substrate. The yarn had to be sufficiently dry following spinning to allow for winding and subsequent separation of the filaments. Drying of the yarn was attempted using various techniques including direct and radiant heat, forced air, and chemical drying agents. Product yarns were analyzed for ease of separation of the filaments, as well as comparison of mechanical properties. Individual fibers were evaluated on the basis of moisture content, surface morphology and fiber diameter. Results indicate that the particular drying method or agent used has a considerable impact upon all of the characteristics listed above. A methanol dry bath was found to provide optimum drying of the chitosan yarn, producing filaments with low moisture content that separated easily from one another. Methanol drying yielded chitosan fibers with smaller diameter, superior surface smoothness and superior mechanical properties to fibers dried using forced air, heat, or other tested drying agents such as acetone and isopropanol. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1435–1444, 1998     

Inkjet printing and surface treatment of an optimized polyurethane-based ink formulation as a suitable insulator over silver for contact with aqueous-based fluids in low-voltage applications

An optimized, formulated polyurethane (PU)-based insulating ink, which was inkjet printed and cured as a tri-layer on top of an inkjet-printed and sintered commercial silver ink base metal fused to polyethylene terephthalate substrate, demonstrated a resistivity of >1.2 × 10⁸ Ω cm at a film thickness of 100 μm when exposed to an aqueous saline solution and a voltage differential of <2 V. This insulating property is highly desirable for biofluids-contacting biosensors. Three PU-based insulator ink formulations were made with different levels of ethylene glycol and carboxymethylcellulose additives to improve ink volatility, viscosity, and dispersion properties. Based on the resultant ink properties important to printing, one of these formulations was selected for further evaluation. The effects of the type and extent of surface conditioning involving UV–O₃ and/or thermal treatments on print quality and completed insulator functionality are discussed. Print quality is assessed by visual and profilometry measurement.