Thermoplastic starch modified with hydrophobic polyurethane microparticles

Modified thermoplastic starches (TPS) were successfully prepared from corn starch (CS) and hydrophobic polyurethane prepolymers (PUPs) by solid‐state reactions under intensive mixing conditions. The structure and properties were investigated using FTIR, SEM, wide‐angle XRD, tensile testing machine, Brookfield viscometer, and contact angle (CA) meter. The results showed that 98.6 ± 0.4% of PUP was cross‐linked to starch, suggesting a high efficiency of the solid‐state reaction. Compared with unmodified starch, the hydrophobic property of the modified TPS was improved, resulting in an increase of the CAs and a decrease of the Brookfield viscosity. Morphology analysis indicated that the modified starch exhibited increased compatibility between the PUP particle and nature starch, leading to the increased elongation at break.     

Enhanced anti-graffiti or adhesion properties of polymers using versatile combination of fluorination and polymer grafting

Commonly used polymers and polymer articles have some advantages, e.g. low. But very often they have not very good adhesion, barrier properties, low conductivity, etc. Specialty polymers possessing necessary properties, e.g. fluoropolymers, can be used to fabricate polymer articles. However, practical use of specially synthesized polymers is restricted due to their high cost and complexity of synthesis. It is possible to coat a polymer with another polymer layer with necessary properties but this co-extrusion method is difficult to apply due to a complexity of applied equipment. Also the problems of adhesion between two polymers and polymers compatibility are to be solved. Very often application properties of polymer goods (adhesion, barrier properties, conductivity, etc.) are defined mainly by their surface properties. Hence, it is not necessary to fabricate articles from specialty polymers but simpler, cheaper, and more convenient to apply a surface treatment of articles made from commonly used relatively cheap polymers. In this case, only thin surface layer several nm to several μm in thickness is to be modified and direct fluorination (treatment with mixture of F₂ and other gases) can be effectively used. For our research we have chosen common widely used polymers. We targeted to improve hydrophobicity/hydrophylicity, adhesion properties and surface conductivity of polymers. For the first time modification of the surface of high density (HDPE), low density (LDPE) and ultrahigh molecular weight polyethylene (UHMWPE), polypropylene (PP), polyethylene terephthalate (PET) and polyvinylchloride (PVC) was performed by direct fluorination followed by a grafting of acrylic acid, styrene, acrylonitrile, vinylidene chloride, aniline and thiophene from the gas phase. Aniline grafting was studied to improve surface conductivity of polymers. Grafting of polymers was confirmed by ATR and MATR FTIR spectroscopy and energy-dispersive X-ray microprobe spectroscopy (cartography). AFM was used to study polymers surface. Influence of the nature of grafted monomers on the surface energy was studied. It was shown that depending on the nature of a grafted monomer hydrophobicity or hydrophilicity can be markedly improved. The hydrophobicity of modified polymers is not changed and is even improved with time contrary to virgin polymers. For the case of PP and UHMWPE grafting of styrene and acrylonitrile improved anti-graffiti properties (graffiti and pollutions from the polymer surface can be easier removed). For the case of HDPE and LDPE grafting of styrene and acrylonitrile improved printability. Grafting of aniline did not improved electrical conductivity. The uniformity of grafted polymers distribution was investigated by energy-dispersive X-ray microprobe spectroscopy (cartography) for the first time.     

Evaluation of anticorrosion and contact resistance behavior of poly(orthophenylenediamine)- coated 316L SS bipolar plate for proton exchange membrane fuel cell

The present work was focused on the corrosion properties and contact resistance behavior of poly(orthophenlyenediamine) (PoPD) coating on 316L SS bipolar plates. To reduce the corrosion rate and increase the interfacial conductivity of 316L SS bipolar plates, PoPD coating was deposited using an electropolymerization technique by the various monomer concentration of orthophenlyenediamine (oPD) on its surface. The presence of 1, 2, 4, 5- tetra substituted benzene nuclei of phenazine units in the polymer coating was confirmed by infrared spectroscopy. X-ray photoelectron spectroscopy analysis has confirmed the (%) of chemical composition in PoPD coating. The results of scanning electron microscopy analysis revealed that the uniform and compact coating with complete cover on 316L SS. The corrosion properties were investigated in 0.5 M H₂SO₄ and 2 ppm HF solution at 80 °C. The polarization test results showed that the PoPD coating reduced the corrosion current density both in the PEMFC anode and cathode environments. The charge transfer resistance values were in the order of 316L SS ? 0.02 M PoPD ? 0.06 M PoPD ? 0.04 M PoPD. A very low interfacial contact resistance and good adhesion strength was observed for 0.04 M PoPD coating. The higher contact angle of 0.04 M PoPD coating explained the hydrophobic property and more benefit of water management in the PEMFC environment. The results of the analysis of total metal ion releases clearly explained that the low level of metal ions released for 0.04 M PoPD coating. The overall studies revealed the PoPD coating with optimized 0.04 M oPD concentration showed best performance and provided more anodic protection to 316L SS bipolar plates.     

A new insight into the adsorption mechanism of patulin by the heat-inactive lactic acid bacteria cells

The primary objective of this study was to identify the characteristics of the heat-inactived lactic acid bacteria (LAB) cells involved in the adsorption of patulin. The bacterial cells were characterized by Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Transmission Electron Microscopy (TEM) and Brunauer–Emmett–Teller (BET) technique. The patulin-exposed bacterial cells and patulin-unexposed bacterial cells were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Zeta Potential and Contact Angle Method. It was found that Lactobacillus brevis 20023 (LB-20023), which has the highest specific surface area and cell wall volume, showed the highest capacity to adsorb patulin from the aqueous solution. Five major elements (C, N, O, P, and S) were detected by SEM-EDS, and LB-20023 displayed the highest nitrogen-to-carbon (N/C) ratio (0.2938). LB-20023 exhibited the highest hydrophobicity, but the zeta potential was not prominent compared to other bacterial cells. The main functional groups involved in adsorbing patulin were C–O, OH and/or NH groups, suggesting that polysaccharides and/or protein were important functional components. Above all, the adsorption capacity of bacterial cells had close relationships with physical and chemical properties of cell surface, including specific surface area, cell wall volume, nitrogen-to-carbon (N/C) ratio, hydrophobicity and functional groups. Further study will be needed to find other additional functional factors.     

Production of calcium nitrate crystals via membrane distillation crystallization using polyvinylidene fluoride/sorbitan trioleate membranes

As an alternative to the energy-intensive evaporation-crystallization method, membrane distillation crystallization (MDC) was applied for the first time to obtain calcium nitrate crystals from its aqueous solution. Calcium nitrate solution was obtained through the reaction between calcium carbonate and nitric acid, and then it was concentrated in the membrane distillation (MD) process and further crystallized. The MD step was conducted using hydrophobic polyvinylidene fluoride (PVDF)/sorbitan trioleate (Span 85) membranes. Span 85 was incorporated into the membrane structure in various concentrations to improve the hydrophobicity of membranes, and the resultant membranes were characterized via different methods. In addition, the resultant calcium nitrate crystals were characterized by X-ray fluorescence (XRF) spectroscopy. The MDC results showed that the optimum amount of Span 85 in the polymeric solution was 4%, which led to the formation of a membrane with higher porosity (67.2%) and water contact angle (95.7°) compared to the neat PVDF membrane. The mentioned membrane exhibited the highest water flux in the MD process compared to the other membranes, and also it produced the highest amount of crystals due to its remarkably better performance in the MD step in terms of feed concentration.     

Influence of slip length on filtration performance of fine particles

Fine particle filtration has been known to become progressively inefficient as the filter cake builds up owing to restricted movement of liquid through the small cavities formed in the cake. In different chemical industries, this restricts higher throughput rates and also results in higher transportation costs due to increase in moisture content. This paper discusses the influence of using a surfactant, DAH (dodecylamine hydrochloride), in enhancing the filtration rate of a finely ground particles and the reduction of moisture content in the cake. The observed enhanced filtration rate has been attributed to a reduction in the resistance to liquid flow due to the increase in hydrophobicity at the particle surface. The resulting enhanced filtration rate has been modelled by superimposing a slip velocity at the boundary of the capillaries formed in the cake. The model evaluates the cake and medium resistances by incorporating a slip length into the filtration equation which varies with the concentration of hydrophobic reagent and the effective size of capillaries. The increase in filtration rate is more pronounced for finer particle slurries. Also, it has been observed that the moisture content of the filter cakes formed was reduced.     

Miniemulsion polymerization of vegetable oil macromonomers

The Thames Research Group developed vegetable oil macromonomer (VOMM) technology to combine the advantages of oil-modified polyesters and waterborne systems, and reduce volatile organic compounds in waterborne coatings. VOMMs offer the advantage of temporary plasticization with the potential for crosslinking after film formation. However, incorporating VOMMs into emulsions is challenging because the highly hydrophobic nature of VOMMs restricts their diffusion through the water phase. Miniemulsion polymerization has been used to incorporate highly hydrophobic monomers in waterborne systems. Diffusion limitations are avoided by polymerizing inside the monomer droplets, and to ensure this, droplet stabilization is required. In our study, a soybean oil-based VOMM was used as a copolymerizable hydrophobe in miniemulsion polymerization. Monomer droplets were stabilized prior to polymerization via catastrophic phase inversion to form stable and small droplets (100 nm). Dynamic light scattering analysis was used to confirm miniemulsion stability. A coagulum-free latex was obtained after polymerization. Surface tension studies and light scattering techniques were used to confirm that monomer droplet nucleation was the dominant mechanism. Gel content studies indicated the formation of a highly branched or crosslinked network upon film application. The miniemulsion technique permitted VOMM incorporation as high as 35 wt% into the polymer backbone.     

氨基化石墨烯改性水性聚氨酯合成及性能研究

用3-氨丙基三甲氧基硅氧烷(APTMS)插层改性氧化石墨烯(GO)得到氨基化石墨烯(APTMS-GO),通过FT-IR、XRD、Raman、TG、TEM、XPS表征出APTMS-GO的结构和形态。将APTMS-GO与带有异氰酸根的聚氨酯预聚物以原位聚合的方式聚合,制备了0-0.55wt%含量APTMS-GO的APTMS-GO/WPU复合材料,测试了其拉伸性能、热学性能、疏水性的变化;利用FE-SEM和TEM观察了截面中纳米填充物的分散情况以及乳液的粒径。结果表明：通过原位聚合得到的复合材料的拉伸强度得到了明显改善,由原来的10.13Mpa增加到28.96Mpa,当APTMS-GO含量为0.22wt%,复合聚氨酯的初始分解温度(Td5)从245℃增大到279℃,随着APTMS-GO含量的逐步增大,复合膜的接触角由71.3°提高到91.28°,实现了分子结构中疏水性作用的改善与提高。     

Effect of methyltrimethoxysilane as a synthesis component on the hydrophobicity and some physical properties of silica aerogels

The effects of adding methyltrimethoxysilane (MTMS) to the synthesis formulation on the hydrophobicity and physical properties of silica aerogels are reported. The molar ratio of the methanol (MeOH) solvent, water (H₂O), and the ammonia (NH₄OH) catalyst to tetramethoxysilane (TMOS) precursor was fixed at 1TMOS:12MeOH:4H₂O:3.6×10⁻³NH₄OH throughout the experiment and the MTMS/TMOS molar ratio M was varied from 0 to 1.55. After gelation, the alcogels were dried supercritically by high-temperature solvent extraction. The hydrophobicity of the resulting aerogels was tested by measuring the water uptake by the aerogel as a function of time, after putting them directly on the surface of water. It was found that for M<0.26 the aerogels were less hydrophobic but more transparent (>90% in the visible range), whereas for M>1.03 the aerogels were more hydrophobic but semi-transparent to opaque. Aerogels that possessed good hydrophobicity and transparency (85% in the visible range) were obtained with an M≈0.70. An increase in the MTMS content in the gels shifted the pore size distribution towards larger pore radii with a broad distribution. In order to determine the thermal stability of the hydrophobic nature of the aerogels, they were heat-treated in air in the temperature range between 25 and 350°C. It was found that below 280°C the aerogel samples showed hydrophobic properties, whereas above 280°C the hydrophobicity vanished. This is due to the disappearance of the CH₃ groups in the aerogels. The aerogels were characterized by optical transmittance, pore size distribution, BET surface area and infrared spectroscopy measurements.     

Oil Binding Ability of Chlorinated and Heated Wheat Starch Granules and Their Use in Breadmaking and Pancake Baking

Chlorination and heat treatment of wheat flour changes the surface character of starch granules from hydrophilic to hydrophobic, and high oil binding ability of the starch granules can be observed. It was suggested that the hydrophobicity, in case of chlorination, was due to chemical modification of the starch granule surface proteins, and, in case of heat treatment, due to conformational changes of the proteins. This hydrophobicity could be also obtained by aging (233 days at room temperature). The hydrophobicity of starch granules in batter is highly related to the springiness of pancake. Heat treated wheat starch granules can encapsulate flavor through their oil binding ability.