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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.
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.
Crosslinked thermoplastics
(2014)
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.
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.
Cyanate esters
(2014)
Cyanate ester resins are an important class of thermosetting compounds that have experienced an ever-increasing interest as matrix systems for advanced polymer composite materials, which among other applications, are especially suitable for highly demanding functions in the aerospace or microelectronics industries. Other names for cyanate ester resins are cyanate resins, cyanic esters, or triazine resins. The various types of cyanate ester monomers share the aOCN functional group that trimerizes in the course of resin formation to yield a highly branched heterocyclic polymeric network based on the substituted triazine core structure. The basic reaction sequence leading to the typical cyanate ester polymer molecule is depicted in Figure 11.1. The curing reaction may take place with or without catalyst.
Since November 2011 the standard DIN 4709 stipulates performance tests for Micro-CHP units in Germany. In contrast to steady state measurements of the CHP unit itself, the test according to DIN 4709 includes the thermal storage tank as well as the internal control unit, and it is based on a 24 h test cycle following a specified thermal load profile. Hence, heat losses from the storage tank are as well taken into account as transient losses of the CHP unit. In addition, the control strategy for loading and unloading the storage tank affects the test results.
The DIN 4709 test cycle has been applied at the test stand for Micro-CHP units at Reutlingen University, and results for the Micro-CHP unit WhisperGen and the EC Power units XRGI 15® and XRGI 20® are available. During the analysis a method has been developed to evaluate the results in case the test cycle does not end in a time slot between 24 and 24.5 h after the starting as demanded by DIN 4709. Since this method has been successfully applied to the test of various CHP units of different size and technology so far, it is suggested to incorporate it to DIN 4709 during the next revision of the standard.
The performance numbers obtained reveal the differences in efficiencies measured at steady-state on the one hand and following the DIN 4709 test cycle on the other hand. While the deviations in electrical efficiencies are small, thermal efficiencies according to DIN 4709 fall below steady state data by 3–6 percentage points. This is attributed to transient thermal losses and heat losses from the storage tank, which are not included in steady state and separate testing of the CHP unit, only.
In visual adaptive tracking, the tracker adapts to the target, background, and conditions of the image sequence. Each update introduces some error, so the tracker might drift away from the target over time. To increase the robustness against the drifting problem, we present three ideas on top of a particle filter framework: An optical-flow-based motion estimation, a learning strategy for preventing bad updates while staying adaptive, and a sliding window detector for failure detection and finding the best training examples. We experimentally evaluate the ideas using the BoBoT dataseta. The code of our tracker is available online.
Vehicles have been so far improved in terms of energy-efficiency and safety mainly by optimising the engine and the power train. However, there are opportunities to increase energy-efficiency and safety by adapting the individual driving behaviour in the given driving situation. In this paper, an improved rule match algorithm is introduced, which is used in the expert system of a human-centred driving system. The goal of the driving system is to optimise the driving behaviour in terms of energy-efficiency and safety by giving recommendations to the driver. The improved rule match algorithm checks the incoming information against the driving rules to recognise any breakings of a driving rule. The needed information is obtained by monitoring the driver, the current driving situation as well as the car, using in-vehicle sensors and serial-bus systems. On the basis of the detected broken driving rules, the expert system will create individual recommendations in terms of energy-efficiency and safety, which will allow eliminating bad driving habits, while considering the driver needs.
The interaction between lipid bilayers in water has been intensively studied over the last decades. Osmotic stress was applied to evaluate the forces between two approaching lipid bilayers in aqueous solution. The force–distance relation between lipid mono- or bilayers deposited on mica sheets using a surface force apparatus (SFA) was also measured. Lipid stabilised foam films offer another possibility to study the interactions between lipid monolayers. These films can be prepared comparatively easy with very good reproducibility. Foam films consist usually of two adsorbed surfactant monolayers separated by a layer of the aqueous solution from which the film is created. Their thickness can be conveniently measured using microinterferometric techniques. Studies with foam films deliver valuable information on the interactions between lipid membranes and especially their stability and permeability. Presenting inverse black lipid membrane (BLM) foam films supply information about the properties of the lipid self-organisation in bilayers. The present paper summarises results on microscopic lipid stabilised foam films by measuring their thickness and contact angle. Most of the presented results concern foam films prepared from dispersions of the zwitterionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) and some of its mixtures with the anionic lipid — 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG).
The strength of the long range and short range forces between the lipid layers is discussed. The van der Waals attractive force is calculated. The electrostatic repulsive force is estimated from experiments at different electrolyte concentrations (NaCl, CaCl2) or by modification of the electrostatic double layer surface potential by incorporating charged lipids in the lipid monolayers. The short range interactions are studied and modified by using small carbohydrates (fructose and sucrose), ethanol (EtOH) or dimethylsulfoxide (DMSO). Some results are compared with the structure of lipid monolayers deposited at the liquid/air interface (monolayers spread in Langmuir trough), which are one of most studied biomembrane model system. The comparison between the film thickness and the free energy of film formation is used to estimate the contribution of the different components of the disjoining pressure to the total interaction in the film and their dependence on the composition of the film forming solution.