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In bioprinting approaches, the choice of bioink plays an important role since it must be processable with the selected printing method, but also cytocompatible and biofunctional. Therefore, a crosslinkable gelatin-based ink was modified with hydroxyapatite (HAp) particles, representing the composite buildup of natural bone. The inks’ viscosity was significantly increased by the addition of HAp, making the material processable with extrusion-based methods. The storage moduli of the formed hydrogels rose significantly, depicting improved mechanical properties. A cytocompatibility assay revealed suitable ranges for photoinitiator and HAp concentrations. As a proof of concept, the modified ink was printed together with cells, yielding stable three-dimensional constructs containing a homogeneously distributed mineralization and viable cells.
Natural wood colors occur within a wide range from almost white (e.g., white poplar), various yellowish, reddish, and brownish hues to almost black (e.g., ebony). The intrinsic color of wood is basically defined by its chemical composition. However, other factors such as specific anatomical formations or physical properties further affect the optical impression. Starting with the chemical composition of wood and anatomical basics, wood color and its modifications are discussed in this chapter. The classic method of coloring or re-coloring wood-based material surfaces is the application of a coating containing appropriate dyes or pigments. Different concepts for wood coating and coloration are presented. Another method used dyes for coloration of the wood structure. As alternative techniques, physical methods, for example, drying, steaming, ammoniation, bleaching, enzyme treatment, as well as treatment with electromagnetic irradiation (e.g., UV), are explained in this chapter.
Allyls
(2014)
This chapter addresses the importance and usage of the commercially low volume thermoset plastics group known as allyls. The three significant sub-elements of this group are poly(diallylphthalates), poly(diallylisophthalates), and poly(allyldiglycol carbonate). Chemistry, processing, and properties are also described. Allyl polymers are synthesized by radical polymerizations of allyl monomers that usually do not produce high-molecular-mass macromolecules. Therefore, only a few specific monomers can produce thermosetting materials. Diallyldiglycolcarbonate (CR-39) and diallylphthalates are the most significant examples that have considerably improved our everyday life.
Allyls
(2022)
This chapter addresses the importance and usage of the commercially low-volume thermoset plastics group known as allyls. The three significant subelements of this group are poly(diallylphthalates), poly(diallylisophthalates), and poly(allyldiglycol carbonate). Chemistry, processing, and properties are also described. Allyl polymers are synthesized by radical polymerizations of allyl monomers that usually do not produce high-molecular-mass macromolecules. Therefore only a few specific monomers can produce thermosetting materials. Diallyldiglycolcarbonate (CR-39) and diallylphthalates are the most significant examples that have considerably improved our everyday life.
Mass-customization is a megatrend that also affects the wood industry. To obtain individually designed laminates in batch size one efficient printing and processing technologies are required. Digital printing was envisaged as it does not depend on highly costly printing cylinders (as used in rotogravure printing) and allows rapid exchange of the printing designs. In the present work, two wellestablished digital printing approaches, the multi-pass and the single-pass technique, were investigated and evaluated for their applicability in decorating engineered wood and low-pressure melamine films. Three different possibilities of implementing digital printing in the decorative laminates manufacturing process were studied: (1) digital printing on coated chipboard and subsequently applying a lacquered top-coat or melamine overlay (designated as “direct printing”, since the LPM was the printing substrate), (2) digital printing on decorative paper which was subsequently impregnated before hot pressing (designated as “indirect printing, variant A”) and (3) digital printing on decorative paper with subsequent interlamination of the paper between impregnated under- and overlay paper layers during the pressing process (designated as “indirect printing, variant B”). Due to various advantages of the resulting cured melamine resin surfaces including a much better technological performance and flexibility in surface texture design, it was decided to industrially further pursue only the indirect digital printing process comprising interlamination and the direct printing process with a melamine overlay-finishing. Basis for the successful trials on production and laboratory scales were the identification of applicable inks (in terms of compatibility with melamine resin) and of appropriate printing paper quality (in terms of impregnation and imprinting ability). After selection and fine tuning of suitable materials, the next challenge to overcome was the initially insufficient bond strength between impregnated overlay and the ink layers which led to unsatisfactory quality of the print appearance and delamination effects. However, the optimization of the pressing program and the development of a modified impregnation procedure for the underlay and overlay papers allowed the successful implementation of digital printing in the production line of our industrial partner FunderMax.
Bioenergy production is a new and promising industry in Ecuador. However, a confusing variety of laws, which are spread among different regulating institutions, regulate the agricultural sector. Such dispersion makes it difficult for farmers and businesses to understand applicable rights, duties, regulations and agricultural policies. Moreover, this rather young industry lacks important experience. In the first section of this work, the existing Ecuadorian legislation on bioenergy is presented and analyzed. Then, a brief, thorough analysis and comparison are carried out for experiences not only in developed countries, but also with similar cultural frameworks and comparable climatic conditions. The results are summarized as specific recommendations that have been handed to the National Agricultural Chamber of Ecuador from academia for the proposal of a Unified Agricultural Code established in the Ecuadorian legal hierarchy as an Organic Law.
Cross-linked thermoplastics
(2022)
Cross-linked thermoplastics represent an important class of materials for numerous applications such as heat-shrinkable tubing, rotational molded parts, and polyolefin foams. By cross-linking olefins, their mechanical performance can be significantly enhanced. This chapter covers the three main methods for the cross-linking of thermoplastics: radiation cross-linking, chemical cross-linking with organic peroxides, and cross-linking using silane-grafting agents. It also considers the major effects of the cross-linking procedure on the performance of the thermoplastic materials discussed.
Auf jeder Stufe der Lebensmittelkette muss von der Herstellung bis zum Inverkehrbringen eine Rückverfolgung der Produkte möglich sein. Erzeuger, Verarbeiter, Transportunternehmen und Händler stehen vor der Herausforderung, Systeme zur Rückverfolgbarkeit effizient in ihre Unternehmensprozesse zu integrieren und gegenseitig zu vernetzen. Für die betriebliche Umsetzung werden die rechtlichen Anforderungen skizziert und die Grundlagen eines Rückverfolgbarkeitssystems vorgestellt.
Die Diskussion um Nachhaltigkeit und Ressourcenschonung hat die gesamte Industrie erreicht. Das Interesse an Naturfasern und Recyclingmaterialien ist gestiegen. An der Fakultät Textil und Design der Hochschule Reutlingen befasst sich die Forschungsgruppe Textile Verfahrenstechnik und Produktentwicklung in enger Kooperation mit mittelständischen Unternehmen mit Naturfasern und Recyclingmaterialien.
Silicones
(2014)
Silicones are found in a variety of applications with requirements that range from long life at elevated temperatures to fluidity at low temperatures. This chapter first considers silicone elastomers and their application in room temperature vulcanizing (RTV) and heat curing systems (HTV). Also, new technologies for UV curing are introduced. Coverage of RTVs includes both one-component and two-component systems and the different cure chemistries of each, and is followed by a separate discussion of silicone laminates. Due to the high importance of silicone fluids, they are also discussed. Fluids include polishes, release agents, surfactants, and dielectric fluids.
Silicones
(2022)
Silicones are found in a variety of applications with requirements that range from long life at elevated temperatures to fluidity at low temperatures. This chapter first considers silicone elastomers and their application in room temperature vulcanizing (RTV) and heat curing systems (HTV). Also, new technologies for UV curing are introduced. Coverage of RTVs includes both one-component and two-component systems and the different cure chemistries of each and is followed by a separate discussion of silicone laminates. Due to the high importance of silicone fluids, they are also discussed. Fluids include polishes, release agents, surfactants, and dielectric fluids.
Three different polyols (soluble starch, sucrose, and glycerol) were tested for their potential in the chemical modification of melamine formaldehyde (MF) resins for paper impregnation. MF impregnated papers are widely used as finishing materials for engineered wood. These polyols were selected because the presence of multiple hydroxy groups in the molecules was suspected to facilitate cocondensation with the main MF framework. This should lead to good resin performance. Moreover, they are readily produced from natural feedstock. They are available in large quantities and may serve as economically feasible, environmentally harmless alternative co-monomers suitable to substitute a portion of fossil-based starting material. In the presented work, a number of model resins were synthesized and tested for covalent incorporation of the natural polyol into the MF Framework. Spectroscopic evidence of chemical incorporation of glycerol was found by applying by 1H, 13C, 1H/13C HSQC, 1H/13C HMBC, and 1H DOSY methods. It was furthermore found that covalent incorporation of glycerol in the network took place when glycerol was added at different stages during synthesis. Further, all resins were used to prepare decorative laminates and the performance of the novel resins as surface finishing was evaluated using standard technological tests. The technological performance of the various modified thermosetting resins was assessed by determining flow viscosity, molar mass distribution, the storage stability, and in a second step laminating impregnated paper to particle boards and testing the resulting surfaces according to standardized quality tests. In most cases, the average board surface properties were of acceptable quality. Our findings demonstrate the possibility to replace several percent of the petrol-based product melamine by compounds obtained from renewable resources.
Estimating molar solubility from the Hildebrand-Scott relation employing Hansen solubility parameters (HSP) is widely presumed a valid semi quantitative approach. To test this presumption and to determine quantitatively the inherent accuracy of such a solubility prognosis, l-ascorbic acid (LAA) was treated as an example of a commercially important solute. Analytical calculus and Monte Carlo (MC) simulation were performed for 20 common solvents with total HSP ranging from 14.5 to 33.0 (MPa)0.5 utilizing validated material data. It was found that, due to the uncertainty of the material data used in the calculations, the solubility prediction had a large scattering and, thus, a low precision.
Comments on “Solubility parameter of chitin and chitosan”, Carbohydrate Polymers 36 (1998) 121–127
(2017)
Results on the solubility parameters of chitin and chitosan presented in the paper DOI: 10.1016/S0144-8617(98)00020-4 were recalculated and data evaluation was redone. A number of misprints, erroneous calculations and data evaluations were found with respect to Hansen as well as total solubility parameters as derived according to group contribution methods by Hoftyzer-Van Krevelen and Hoy’s system. Revised numerical data are presented.
Self-healing thermosets
(2022)
This chapter discusses the basic extrinsic, intrinsic, and combined extrinsic/intrinsic strategies for equipping thermosetting polymers with self-healing properties. The main focus will be on the presentation of a holistic optimization of thermosetting materials, that is, on a simultaneous optimization of both self-healing and other, specialized material properties. Due to their very rigid, highly cross-linked three-dimensional structure, thermosetting polymers require special chemical strategies to achieve self-healing properties. The main chemical strategies available for this will be briefly outlined. The examples given illustrate interesting and/or typical procedures and serve as an inspiration to find solutions for your own applications. They summarize important recent development in research and technology aiming toward multifunctional truly smart self-healing thermosetting materials. An important aspect in this topic area is also how precisely the self-healing effects are analytically checked, quantified, and evaluated. A range of measuring methods is available for this purpose. In this chapter, the most important analytical tools for testing self-healing properties are briefly introduced and highlighted with some illustrative examples.
Melamine formaldehyde (MF) resins are widely used for the gluing and surface coating of wood-based consumer products in the interior design of living environments. MF resins are especially relevant in decorative laminate applications because of their good performance-to-price ratio. In their industrial processing, an important intermediate state is the liquid MF prepolymer that is used for decorative paper impregnation. Here, the drying of impregnated papers is investigated with respect to premature curing. A new method to quantify water release upon drying that allows estimation of the degree of undesired precuring is described. Since curing proceeds via polycondensation, crosslinking brings about the release of water molecules. By thermogravimetric analysis (TGA), drying was studied in terms of water release due to physical drying (elimination of “dilution water”) and chemical crosslinking of the prepolymer to a three-dimensional MF network (elimination of chemically liberated water). The results obtained by TGA/IR spectroscopic analysis of the liberated volatiles show that the emission of water from b-stage MF can be clearly analytically separated into a physical (evaporation of dilution water) and a chemical (liberation via condensation) sequence. TGA experiments were correlated with curing experiments performed with differential scanning calorimetry (DSC) to estimate the residual crosslinking capacities of the impregnated papers. The drying conditions used during the preparation of impregnated decorative papers seemed to significantly affect their remaining reactivity only when harsh drying conditions were used. Upon heat exposure for prolonged time, precuring of the oligomer units results in a shift of the temperature maxima in TGA.
Unsaturated polyester resins (UPR) and vinyl ester resins (VER) are among the most commercially important thermosetting matrix materials for composites. Although comparatively low cost, their technological performance is suitable for a wide range of applications, such as fiber-reinforced plastics, artificial marble or onyx, polymer concrete, or gel coats. The main areas of UPR consumption include the wind energy, marine, pipe and tank, transportation, and construction industries. This chapter discusses basic UPR and VER chemistry and technology of manufacturing, and consequent applications. Some important properties and performance characteristics are discussed, such as shrinkage behavior, flame retardance, and property modification by nanoparticles. Also briefly introduced and described are the practical aspects of UPR and VER processing, with special emphasis on the most widely used technological approaches, such as hand and spray layup, resin infusion, resin transfer molding, sheet and bulk molding, pultrusion, winding, and centrifugal casting.
Unsaturated polyester resins (UPR) and vinyl ester resins (VER) are among the most commercially important thermosetting matrix materials for composites. Although comparatively low cost, their technological performance is suitable for a wide range of applications, such as fiber-reinforced plastics, artificial marble or onyx, polymer concrete, or gel coats. The main areas of UPR consumption include the wind energy, marine, pipe and tank, transportation, and construction industries.
This chapter discusses basic UPR and VER chemistry and technology of manufacturing, and consequent applications. Some important properties and performance characteristics are discussed, such as shrinkage behavior, flame retardance, and property modification by nanoparticles. Also briefly introduced and described are the practical aspects of UPR and VER processing, with special emphasis on the most widely used technological approaches, such as hand and spray layup, resin infusion, resin transfer molding, sheet and bulk molding, pultrusion, winding, and centrifugal casting.
Processing
(2014)
In this chapter, some relevant aspects and illustrative examples of online monitoring tools as the basis for process control in the manufacturing and processing of thermosetting resins are briefly discussed. In principle, any chemical or physical information made accessible by sensors can be used for online monitoring of resin formation, resin location in the mold, and resin cure. For instance, changes in the flow properties of the reaction mixture are often routinely recorded in dependence of the reaction time during resin synthesis as a measure for the degree of conversion of raw materials into macromolecules or oligomers by applying rheometry in an in-process environment. Typically, a small sample of the reaction mixture is by-passed, subjected to rheological measurement, and re-introduced into the bulk reactor. In a similar way, pH measurements, turbidimetric measurements, or other analyses are performed. Although rheometry may not always be suitable for following resin cure (especially in cases where there is a very rapid increase in viscosity after initiation of the cure), [1] naturally, the method can in principle also be used in the subsequent processing of the thermosets, for instance in the curing of wood glue applied to wood specimen [2]. Similarly, pH changes during thermoset curing can be followed. Hence, an encyclopedic and comprehensive approach to present process control methods would systematically proceed according to the involved physical measurement principle. However, since only a very Brief sketch of means for monitoring thermoset processing can be given here, only a small, personally biased selection of important methods and application examples is addressed in the following sections. These examples hopefully illustrate some of the general strategies and solutions to problems that are typically encountered when processing thermosets.