Photopolymer-Based Composite with Substance Release Capability Manufactured Additively with DLP Method.

In this study, caffeine-loaded photoresin composites with homogeneous structures, suitable for additive manufacturing of transdermal microneedle systems, were obtained. The properties of the composites with varying caffeine concentrations (0.1-0.4% w/w) were investigated for carbon-carbon double bond conversion using Fourier Transform Infrared Spectroscopy, surface wettability and mechanical properties using a static tensile test and nanoindentation, and caffeine release in ethanol using UV-Vis. The caffeine concentration did not affect the final degree of double bond conversion, which was confirmed in tensile tests, where the strength and Young's modulus of caffeine-loaded samples had comparable values to control ones. Samples with 0.1 and 0.2% caffeine content showed an increase in nanohardness and reduced elastic modulus of 50 MPa and 1.5 MPa, respectively. The good wettability of the samples with water and the increase in surface energy is a favorable aspect for the dedicated application of the obtained composite materials. The amount of caffeine released into the ethanol solution at 1, 3 and 7 days reached a maximum value of 81%, was higher for the lower concentration of caffeine in the sample and increased over time. The conducted research may enhance the potential application of composite materials obtained through the digital light processing method in additive manufacturing.

Reproducibility of inverse gas chromatography under infinite dilution: Results and interpretations of an interlaboratory study.

Over the last years, inverse gas chromatography (IGC) proved to be a versatile and sensitive analytical technique for physicochemical properties. However, the comparability of results obtained by different users and devices remains a topic for debate. This is the first time, an interlaboratory study using different types of IGC instruments is reported. Eight organizations with different IGC devices defined a common lab measurement protocol to analyse two standard materials, silica and lactose. All data was collected in a standard result form and has been treated identically with the objective to identify experimentally observed differences and not potentially different data treatments. The calculated values of the dispersive surface energy vary quite significantly (silica: 22 mJ/m2 - 34 mJ/m2, lactose 37 mJ/m2 - 51 mJ/m2) and so do the ISP values and retention volumes for both materials. This points towards significant and seemingly undiscovered differences in the operation of the instruments and the obtained underlying primary data, even under the premise of standard conditions. Variations are independent of the instrument type and uncertainties in flow rates or the injected quantities of probe molecules may be potential factors for the differences. This interlaboratory study demonstrates that the IGC is a very sensitive analytical tool, which detects minor changes, but it also shows that for a proper comparison, the measurement conditions have to be checked with great care. A publicly available standard protocol and material, for which this study can be seen as a starting point, is still needed to judge on the measurements and the resulting parameters more objectively.

Transformation of Iodosulfuron-Methyl into Ionic Liquids Enables Elimination of Additional Surfactants in Commercial Formulations of Sulfonylureas.

Efficient use of herbicides for plant protection requires the application of auxiliary substances such as surfactants, stabilizers, wetting or anti-foaming agents, and absorption enhancers, which can be more problematic for environment than the herbicides themselves. We hypothesized that the combination of sulfonylurea (iodosulfuron-methyl) anion with inexpensive, commercially available quaternary tetraalkylammonium cations could lead to biologically active ionic liquids (ILs) that could become a convenient and environment-friendly alternative to adjuvants. A simple one-step synthesis allowed for synthesizing iodosulfuron-methyl based ILs with high yields ranging from 88 to 96% as confirmed by UV, FTIR, and NMR. The obtained ILs were found to possess several favorable properties compared to the currently used sodium salt iodosulfuron-methyl, such as adjustable hydrophobicity (octanol-water partition coefficient) and enhanced stability in aqueous solutions, which was supported by molecular calculations showing cation-anion interaction energies. In addition, soil mobility and volatility of ILs were more beneficial compared to the parental herbicide. Herbicidal activity tests toward oil-seed rape and cornflower revealed that ILs comprising at least one alkyl chain in the decyl to octadecyl range had similar or better efficacy compared to the commercial preparation without addition of any adjuvant. Furthermore, results of antimicrobial activity indicated that they were practically harmless or slightly toxic toward model soil microorganisms such as Pseudomonas putida and Bacillus cereus.

Evaluation of the physico-chemical properties of hydrocarbons-exposed bacterial biomass.

In the efforts for the removal of hazardous materials from the environment biological processes are a valuable tool. Although much attention has been paid to the changes in bacteria at the omics level, another, physical-chemical perspective on the issue is essential, as little is known of microbial response to continuous exposition on harmful substances. This study provides in-depth characterization of the physical-chemical parameters of bacterial biomass after hydrocarbons exposure. To provide comparability of the harmful effects of chlorotoluenes and xylenes non-exposed and 12-months hydrocarbons exposed cells were analyzed, using the advanced spectrometric methods, inverse gas chromatography and low-temperature N2 sorption to evaluate acid-base as well as dispersive properties of the studied biomass. Presented results indicate P. fluorescens B01 cells strategy aimed at protecting the cell, thus lowering its' biodegradation efficiency as a result of metabolic stress. The outcome of the study was that prolonged exposure to pollutants might reduce the bioavailability of hydrocarbons to bacteria cells, and consequently decrease the effectiveness of decontamination of polluted sites by indigenous microorganisms.

Synthesis and Characterization of Low-Cost Cresol-Based Benzoxazine Resins as Potential Binders in Abrasive Composites.

A series of cresol-based benzoxazines were synthesized for potential application as a polymer matrix in abrasive composites. The chemical structures of the obtained benzoxazine resins were investigated in detail using Fourier transform infrared spectroscopy (FTIR) and hydrogen-1 as well as carbon-13 nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR) with an additional analysis using two-dimensional NMR techniques (2D NMR 1H-1H COSY, 1H-13C gHSQC and gHMBC). Structural analysis confirmed the presence of vibrations of -O-C-N- at ~950 cm-1 wavenumber, characteristic for an oxazine ring. The thermal properties of benzoxazine monomers were examined using differential scanning calorimetry (DSC) analysis. The polymerization enthalpy varied from 143.2 J/g to 287.8 J/g. Thermal stability of cresol-based benzoxazines was determined using thermogravimetry (TGA) analysis with additional analysis of the amount of volatile organic compounds (VOC) emitted from the synthesized benzoxazines during their crosslinking by static headspace coupled with gas chromatography technique (HS-GC). The amount of residual mass significantly differed between all synthesized polybenzoxazines in the range from 8.4% to 21.2%. The total VOC emission for benzoxazines decreased by 46-77% in reference to a conventional phenolic binder. The efficiency of abrasive composites with the benzoxazine matrix was evaluated based on abrasion tests. Performed analyses confirmed successful synthesis and proper chemical structure of cresol-based benzoxazines. All the experiments indicated that benzoxazines based on different cresol isomers significantly differ from each other. Good thermal performance and stability of the abrasive composites with the polybenzoxazine matrix and significantly lower VOC emission allow us to state that benzoxazines can be a promising and valuable alternative to the phenolics and a new path for the development of modern, eco-friendly abrasives.

The effect of lignin-alumina hybrid additive on the properties of composition used in abrasive tools.

Lignin-Al2O3 hybrids were tested as effective additives for application in abrasive materials. The main focus was on the reduction of environmental pollution. The emission of volatile compounds, mainly phenol and formaldehyde, was investigated using detailed evolved gas analysis (EGA) performed by means of mass spectroscopy (QMS) in combined differential scanning calorimetry (DSC) and thermogravimetry (TG) analysis. It was established that the addition of lignin-Al2O3 hybrid additives can reduce the emission of phenol and formaldehyde. Crucially, free phenol emission was not detected from the lignin-Al2O3 additives or from lignin itself using the TG-MS method. Moreover, the addition of lignin-type fillers to phenolic composites can lower emissions of the two aforementioned compounds. No emission of other toxic compounds was detected. The mechanical properties of the lignin-alumina hybrids and resin systems were investigated using the three-point flexural test (also as an element of an ageing test), a compressive test, and testing of abrasibility. The results indicate that the lignin and alumina used as a hybrid additive for abrasive materials improve the adhesion between the binder and abrasive grain, and increase the flexibility of the composites, which has a positive impact on the performance of the final products.

Kraft lignin/cubic boron nitride hybrid materials as functional components for abrasive tools.

In this study, the kraft lignin/cubic boron nitride hybrid materials have been obtained and characterized for the first time. The effectiveness of the combination of lignin and boron nitride was evaluated on the basis of Fourier transform infrared spectroscopy. Furthermore, it was confirmed that the addition of cubic boron nitride (cBN) improved the thermal stability of the inorganic-organic material. Upswing in thermal properties allowed to apply the prepared materials in preparation of model abrasive composites. Beneficial influence of the lignin/cBN filler was also proven by a noticeable decrease in the amount of harmful phenol released from the compositions during headspace gas chromatography analysis. Mechanical properties of the lignin/boron nitride hybrids and resin systems were investigated by the three-point flexural test. The obtained results show that the used additives can be promising materials for abrasive tools combining the good properties of lignin as a plasticizer and of cubic boron nitride as a filler which improves the thermal and mechanical properties of finished products and, at the same time, limits the negative impact on human health and environment.

Modification of Ti6Al4V surface by diazonium compounds.

Ti6Al4V alloy is the most commonly used in orthopedic industry as an endoprosthesis. Ti6Al4V exhibits good mechanical properties, except the abrasion resistance. Surface modification of Ti6Al4V in order to obtain organic layer, and then the attachment of the polymer, can allow for overcoming this problem. The aim of the work was the modification of Ti6Al4V surface by diazonium compounds: salt or cation generated in situ and examine the influence of the reducing agent - ascorbic acid, and the temperature of reaction on modification process. Moreover, the simulated body fluid was used for the assessment of the organic layer stability on Ti6Al4V surface. The evaluation of the modification was carried out using the following methods: Raman microspectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Higher temperature of modification by 4-hydroxymethylbenzenediazonium cation, provides the largest amount of organic layer on the Ti6Al4V alloy. In the case of the Ti6Al4V modified by Variamine Blue B salt, the amount of organic layer is not dependent on the reaction condition. Moreover, the ascorbic acid and the presence of TiO2 does not effect on the modification. The modified surface is completely coated with the organic layer which is stable in simulated body fluid.

The Physicochemical Characteristics of Prosthetic Materials and Their Influence on Their Clinical Properties.

The use of elastic materials favours degradation of their surface. The period of their clinical usefulness is then shortened, and their further utilisation in the oral cavity may have the reverse effect. The surface properties of such material as well as the influence of the humidity on their surface are very important as they determine the prosthetic materials behavior in the mouth. The surface of such material should be resistant to water. Inverse gas chromatography is an accurate, sensitive technique for studying surface properties. Thanks to using a unique equipment specially designed for IGC technique, Surface Energy Analyzer, it was possible to characterize the surface at 0 and 80% of humidity. Our results show that increased humidity does not affect surface properties of studied prosthetic materials. Their ability to dispersive and specific interactions change in very limited degree. IGC experiment was also applied for the estimation of Hansen solubility parameters that indicate ability of a material to dispersive, polar, and hydrogen-bonding interactions. Relation between the surface characteristics and practical use of soft lining materials with implications for their clinical usefulness is also discussed.

Characteristics of Multifunctional, Eco-Friendly Lignin-Al2O3 Hybrid Fillers and Their Influence on the Properties of Composites for Abrasive Tools.

The main aim of the present study was the preparation and comprehensive characterization of innovative additives to abrasive materials based on functional, pro-ecological lignin-alumina hybrid fillers. The behavior of lignin, alumina and lignin-Al2O3 hybrids in a resin matrix was explained on the basis of their surface and application properties determined by inverse gas chromatography, the degree of adhesion/cohesion between components, thermomechanical and rheological properties. On the basis of the presented results, a hypothetical mechanism of interactions between lignin and Al2O3 as well as between lignin-Al2O3 hybrids and phenolic resins was proposed. It was concluded that lignin compounds can provide new, promising properties for a phenolic binder combining the good properties of this biopolymer as a plasticizer and of alumina as a filler improving mechanical and thermal properties. The use of such materials may be relatively non-complicated and efficient way to improve the performance of bonded abrasive tools.

Activation of Magnesium Lignosulfonate and Kraft Lignin: Influence on the Properties of Phenolic Resin-Based Composites for Potential Applications in Abrasive Materials.

Magnesium lignosulfonate and kraft lignin were activated by different oxidizing agents for use in phenolic resin composites used for the production of abrasive components. The physicochemical properties of the oxidized materials were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), dynamic mechanical-thermal analysis (DMTA) and inverse gas chromatography (IGC). The homogeneity of the model abrasive composites containing the studied products was assessed based on observations obtained using a scanning electron microscope (SEM). FTIR and XPS analysis of the oxidized products indicated that the activation process leads mainly to the formation of carbonyl groups. The IGC technique was used to assess changes in the surface energy and the acid-base properties of the studied biopolymers. The changes in the acid-base properties suggest that more groups acting as electron donors appear on the oxidized surface of the materials. DMTA studies showed that the model composites with 5% magnesium lignosulfonate oxidized by H2O2 had the best thermomechanical properties. Based on the results it was possible to propose a hypothetical mechanism of the oxidation of the natural polymers. The use of such oxidized products may improve the thermomechanical properties of abrasive articles.

Reactive Diazonium-Modified Silica Fillers for High-Performance Polymers.

We describe a simple way of modification of three silica-based fillers with in situ generated 4-hydroxymethylbenzenediazonium salt (+N2-C6H4-CH2OH). The rationale for using a hydroxyl-functionalized diazonium salt is that it provides surface-functionalized fillers that can react with phenolic resins. The modification of silica by diazonium salts was assessed using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). FTIR spectroscopy permitted the tracking of benzene ring breathing and C-C. The absence of the characteristic N≡N stretching vibration in the 2200-2300 cm-1 range indicates the loss of the diazonium group. XPS results indicate a higher C/Si atomic ratio after the diazonium modification of fillers and the presence of π-π* C1s satellite peaks characteristic of the surface-tethered aromatic species. Adhesion of aryl layers to the silicas is excellent because they withstand harsh thermal and organic solvent treatments. Phenolic resins (used, for example, as binders in abrasive products) were filled with diazonium-modified silicas at 10-25 wt %. The reactivity of the fillers toward phenolic resins was evaluated by the determination of the flow distance. After annealing at 180 °C, the diazonium-modified silica/phenolic resin composites were mechanically tested using the three-point flexural method. The flexural strength was found to be up to 35% higher than that of the composites prepared without any diazonium salts. Diazonium-modified silica with surface-bound -CH2-OH groups is thus ideal reactive filler for phenolic resins. Such filler ensures interfacial chemical reactions with the matrix and imparts robust mechanical properties to the final composites. This specialty diazonium-modified silica will find potential application as fillers in the composites for the abrasive industry. More generally, aryl diazonium salts are a unique new series of compounds for tailoring the surface properties of fillers and tuning the physicochemical and mechanical properties of polymer composites.

Physicochemical Characterization of Functional Lignin-Silica Hybrid Fillers for Potential Application in Abrasive Tools.

Functional lignin-SiO2 hybrid fillers were prepared for potential application in binders for phenolic resins, and their chemical structure was characterized. The properties of these fillers and of composites obtained from them with phenolic resin were compared with those of systems with lignin or silica alone. The chemical structure of the materials was investigated by Fourier transform infrared spectroscopy (FT-IR) and carbon-13 nuclear magnetic resonance spectroscopy (13C CP MAS NMR). The thermal stability of the new functional fillers was examined by thermogravimetric analysis-mass spectrometry (TG-MS). Thermo-mechanical properties of the lignin-silica hybrids and resin systems were investigated by dynamic mechanical thermal analysis (DMTA). The DMTA results showed that abrasive composites with lignin-SiO2 fillers have better thermo-mechanical properties than systems with silica alone. Thus, fillers based on lignin might provide new, promising properties for the abrasive industry, combining the good properties of lignin as a plasticizer and of silica as a filler improving mechanical properties.

Surface energy of bovine dentin and enamel by means of inverse gas chromatography.

Adhesion between tooth tissues and dental fillings depends on the surface energy of both connected materials. Bond strength can be determined directly or indirectly as a work of adhesion on the basis of values of surface energy of these materials. Inverse gas chromatography (IGC) is one of the methods of surface energy examination. In this study the values of total surface energy components of wet and dry teeth fragments (enamel, crown dentin and root dentin) were determined with the use of inverse gas chromatography. Inverse gas chromatography has never been used for investigation of surface energy of natural tooth tissues. Different storage conditions were examined - wet and dry. Different values of surface energy are observed according to the type of tooth tissue (dentin or enamel), occurring place (crown or root) and storage conditions (dry or wet). The effect of tissue type and occurring place was the greatest, while storage conditions were of secondary importance. Surface energy depends on composition of tissue, its surface area and the presence of pores.

Application of inverse gas chromatography in physicochemical characterization of phenolic resin adhesives.

One of the most important stages during production of abrasive tools is their hardening. The degree of hardening is very important and influence toughness of the final product. During hardening process the cross-linking of the phenolic resins, used as a binder, occurs. Nowadays, there is no standard, accurate and simple method for the estimation of the hardening degree of abrasive tools. The procedure of the determination of hardening degree of the binder (phenolic resins) by means of inverse gas chromatography (IGC) was presented in this paper. Results obtained by use of IGC derived method was verified by Soxhlet extraction and by FTIR method. Good agreement was found for results from IGC and Soxhlet extraction whereas those from FTIR were much lower. FTIR method supplies data concerning bulk properties not the surface as in case of IGC and Soxhlet methods. These results indicate that resins are more cross-linked on the surface than inside the material.

Inverse gas chromatography investigation of oxidized polyolefins: surface properties.

Oxidized polyolefins were obtained in processes with the use of air or oxygen as oxidizing agent. The oxidation process caused partial polymer degradation and the change of the surface properties of examined materials. The magnitude of these changes was estimated by means of inverse gas chromatography. All oxidized materials were found to exhibit slightly acidic character. Surface properties strongly depend on the content of oxygen functional groups (oxidation degree) and type of initial material. The most active surfaces were found for oxidized polypropylene and polyethylene wax. The use of principal component analysis allowed to select four parameters offering complete information on the physiochemical character of examined materials (γS(D)), acid volume or saponification number, KA or KD and KA/KD.

Estimation of polyurethane-carbon black interactions by means of inverse gas chromatography.

The properties of composites depend mainly on the interfacial interactions between filler and matrix that can be related to the adhesion between filler and polymer matrix. In this study the work of cohesion between the carbon black particles - Wcoh - and the thermodynamic work of adhesion - Wa - between four carbon blacks of different specific surface area and surface chemistry (nature and content of carbon-oxygen functional groups) and thermoplastic polyurethane were calculated by means of inverse gas chromatography (IGC) at infinite dilution. IGC derived data indicated that the work of adhesion increased by increasing the surface area of the carbon black, but the opposite trend was found in Wa/Wcoh and work of cohesion. According to the Wa/Wcoh values the filler particles should be well dispersed into the polyurethane matrix giving homogenous composites. The carbon black-thermoplastic polyurethane interactions determined by plate-plate rheology showed the same trend than that for the Wa/Wcoh values. However, the thermodynamic work of adhesion values derived from IGC were not in agreement with the carbon black-polyurethane interfacial interactions, likely due to the dominant effect of the carbon black in reducing the crystallinity and increasing the degree of phase separation of the thermoplastic polyurethane.

Influence of relative humidity on the properties of examined materials by means of inverse gas chromatography.

Inverse gas chromatography (IGC) at infinite dilution was applied to evaluate the surface properties of sorbents and the effect of different carrier gas humidity. They were stored in different environmental humidity - 29%, 40%, and 80%. The dispersive components of the surface free energy of the zeolites and perlite were determined by Schulz-Lavielle method, whereas their tendency to undergo specific interactions was estimated basing on the electron donor-acceptor approach presented by Flour and Papirer. Surface parameters were used to monitor the changes of the properties caused by the humidity of the storage environment as well as of RH of carrier gas. The increase of humidity of storage environment caused a decrease of sorbents surface activity and increase the ability to specific interaction.

Inverse gas chromatography as a source of physiochemical data.

Inverse gas chromatography (IGC) is presented as a useful method for the examination of physicochemical properties of various materials. The advantages of IGC are presented. However, the uncertainties and sources of possible errors are also indicated and discussed.