Structured textile surfaces for easy-to-clean properties towards dry soil

Soiling of (textile) surfaces is a big issue as it reduces the users comfort and may decrease the conservation of value of the product. In automotive, interior parts of head lining and side lining are soiled by airborne dust, brought into the car by the ventilation system. To overcome these problems, textiles can be functionalized with anti-soiling finishes. However, commercial anti-soiling products often are very effective against liquid soil but less effective against dry soil. Repellency of this type of soil (e.g. street dust) can be achieved by (nano) structured surfaces which reduce the contact area between textile and dirt particle. In this research project textile surfaces with easy-to-clean properties for dry soil were prepared. Textile samples were functionalized with mixtures of structuring hydrophilic silica particles (HDK-C10) and binder systems based on silanes. To determine the easy-to-clean effect, samples were soiled with standard soil using a modified filter test rig and were vacuum cleaned afterwards. Scanning electron microscopy (SEM) was used to analyze particle size and distribution. The low viscosity of the components of the binder system enabled film formation around each single fiber. Film properties could be adjusted by different functionalities of silanes. Especially, silica particles in combination with a mixture of a vinylsilane (VTEO) and a mercapto silane (MS) showed good cleaning properties. This effect remains for several soiling and cleaning cycles which demonstrates the permanence of the finishing. (C) 2017 Elsevier Ltd

HT process for treatment of PET fabrics with chitosan containing recipes

Polyester is the leading man-made fiber in the field of textiles and clothing. Polyester is usually dyed and finished using a process temperature in the range of 120 to 135 ºC. Such a process is known as a high-temperature (HT) process. The application of chitosan on cellulosic materials is an interesting approach to textile functionalization. In contrast, the application of chitosan by the HT process for the functional treatment of polyester is less investigated. With this background, the present study is related to the surface characteristics of different polyester fabrics with implemented chitosan after performing the HT process

Разработка ПГУ-ТЭЦ на базе ГТУ SGT5-4000F

Целью работы является разработка парогазового энергоблока ТЭЦ на базе ГТУ. Проводится анализ режимов работы теплофикационных турбин в составе ПГУ, разрабатывается математическая модель поверочного расчета котла-утилизатора, проводится обоснование расчетного режима проектирования КУ, выполняется расчет режимов работы и годовых показателей ПГУ-ТЭЦ.The aim of the work is to develop a combined cycle power plant based on the SGT5-4000F GTU. The analysis of the operating modes of cogeneration turbines as part of a combined cycle power plant

Reduction of radiation transmission through functionalization of textiles from man-made cellulosic fibers

Both ultraviolet (UV) and infrared (IR) light have negative impact on the human health. With this background it is the main aim of the current research to realize a textile material which is able to protect against both UV light and IR light. For this research, regenerated cellulosic fibers from the Lyocell process are used and modified. Main analytical investigations are done by photo-spectroscopy in arrangement of diffuse transmission for the spectral range from 220 nm to 1400 nm. Additionally, microscopic investigations are done by scanning electron microscopy (SEM). For material development, Lyocell fibers functionalized with TiO2 particles are first processed into yarns and then into knitted fabrics. Compared to non-functionalized textiles, the transmission is reduced in the UV range due to the absorption behavior of TiO2. Subsequent dyeing with anthraquinone or reactive dyes enhanced the UV protective effect. To reduce the transmission in the near IR range (NIR), non-functionalized Lyocell knitted fabrics are functionalized with various IR absorbers in different concen­trations. With increasing concentration, the transmission de­creased. However, a grey coloration of the textile is observed simultaneously, with increased concentration. This must be con­sidered in further processing steps. With these methods for function­alization, it is possible to produce textiles that offer increased protection against UV and IR radiation. These are promising materials for the production of clothing or work wear

Development of tissue engineering strategies for supporting regeneration after injuries of the nervous system

This thesis deals with the preparation of artificial guiding structures for supporting regeneration after nerve injuries. Injuries of the nervous system can have serious consequences such as the loss of motoric and sensoric function. As existing treatment methods for the peripheral nervous system include several unsatisfying deficits and due to the absence of efficient treatment for injuries of the central nervous system, the development of an artificial scaffold for supporting nerve regeneration is highly desirable. Chemical composition, mechanical properties and oriented structures for aligned guidance of recovering nerves are important issues for such scaffolds. The method of electrospinning was applied to produce highly oriented fibres from different materials with low densities to achieve oriented cell growth and aligned extensions from a variety of neuronal and non-neuronal cells. For in vitro experiments fibres were collected onto glass cover slips which were surface functionalised with a thin hydrogel layer based on star-shaped poly(ethylene glycol)-stat-poly(propylene glycol) (sPEG). This layer demonstrated non-adhesive properties towards cells and proteins which enabled controlled investigation of the effects actuated by the fibres. Three different polymeric materials were developed and electrospun into fibres: Firstly, blends of poly(caprolactone) (PCL) and the extracellular matrix protein collagen with different ratios were prepared. High quality oriented suspended fibres were obtained at a PCL-collagen ratio of 3:1. Fibre diameters were between 0.4-2.4 µm. Several analytical methods demonstrated the existence of collagen at the fibre surface. Experiments with cells important in the nervous system including neurons, Schwann cells, astrocytes, oligodendroyctes and olfactory ensheathing cells showed an affinity of the cells to the collagen containing fibres. Neurites were longer and cells migrated further on these fibres, in contrast to pure PCL fibres. Secondly, amphiphilic poly(ethylene oxide)-b-poly(caprolactone) (PEO-b-PCL) block copolymers with molecular weights between 34000 to 76000 g/mol and different block length ratios were prepared. High quality oriented fibres could easily be obtained with high molecular weight polymers. Surface analysis demonstrated a hydrophilic character and reduced protein adsorption. Additionally, a GRGDS-functionalised block copolymer was prepared. Analytics verified the success of each preparation step. The functionalisation with the peptide sequence should allow cellular adhesion and guidance of neuronal cells while simultaneously inhibiting undesired protein adsorption. This makes the polymers suitable as implantable biomaterials with controlled material/body interactions. However, impurities and degradation processes during the synthesis prevented oriented electrospinning and therefore cell experiments were not performed. Thirdly, blends of sPEG, PCL and poly(caprolactone-diol) (PCL-diol) were prepared and functionalised either with the peptide sequence GRGDS or the protein fibronectin. Oriented suspended fibres could be electrospun. A reduced protein affinity the blends demonstrated the existence of sPEG at the fibre surface. Unfunctionalised PCL/sPEG fibres showed minimal cellular migration and axonal outgrowth while in contrast, the biologically functionalised fibres increased cellular response significantly. Oriented suspended and biological functionalised electrospun fibres encouraged cell adhesion and migration and induced alignment of cells and extensions according to the fibre direction. Thus, the fibres developed in this thesis are a promising tool for the preparation of scaffolds for neuronal regeneration after nerve injuries

Development of tissue engineering strategies for supporting regeneration after injuries of the nervous system

This thesis deals with the preparation of artificial guiding structures for supporting regeneration after nerve injuries. Injuries of the nervous system can have serious consequences such as the loss of motoric and sensoric function. As existing treatment methods for the peripheral nervous system include several unsatisfying deficits and due to the absence of efficient treatment for injuries of the central nervous system, the development of an artificial scaffold for supporting nerve regeneration is highly desirable. Chemical composition, mechanical properties and oriented structures for aligned guidance of recovering nerves are important issues for such scaffolds. The method of electrospinning was applied to produce highly oriented fibres from different materials with low densities to achieve oriented cell growth and aligned extensions from a variety of neuronal and non-neuronal cells. For in vitro experiments fibres were collected onto glass cover slips which were surface functionalised with a thin hydrogel layer based on star-shaped poly(ethylene glycol)-stat-poly(propylene glycol) (sPEG). This layer demonstrated non-adhesive properties towards cells and proteins which enabled controlled investigation of the effects actuated by the fibres. Three different polymeric materials were developed and electrospun into fibres: Firstly, blends of poly(caprolactone) (PCL) and the extracellular matrix protein collagen with different ratios were prepared. High quality oriented suspended fibres were obtained at a PCL-collagen ratio of 3:1. Fibre diameters were between 0.4-2.4 µm. Several analytical methods demonstrated the existence of collagen at the fibre surface. Experiments with cells important in the nervous system including neurons, Schwann cells, astrocytes, oligodendroyctes and olfactory ensheathing cells showed an affinity of the cells to the collagen containing fibres. Neurites were longer and cells migrated further on these fibres, in contrast to pure PCL fibres. Secondly, amphiphilic poly(ethylene oxide)-b-poly(caprolactone) (PEO-b-PCL) block copolymers with molecular weights between 34000 to 76000 g/mol and different block length ratios were prepared. High quality oriented fibres could easily be obtained with high molecular weight polymers. Surface analysis demonstrated a hydrophilic character and reduced protein adsorption. Additionally, a GRGDS-functionalised block copolymer was prepared. Analytics verified the success of each preparation step. The functionalisation with the peptide sequence should allow cellular adhesion and guidance of neuronal cells while simultaneously inhibiting undesired protein adsorption. This makes the polymers suitable as implantable biomaterials with controlled material/body interactions. However, impurities and degradation processes during the synthesis prevented oriented electrospinning and therefore cell experiments were not performed. Thirdly, blends of sPEG, PCL and poly(caprolactone-diol) (PCL-diol) were prepared and functionalised either with the peptide sequence GRGDS or the protein fibronectin. Oriented suspended fibres could be electrospun. A reduced protein affinity the blends demonstrated the existence of sPEG at the fibre surface. Unfunctionalised PCL/sPEG fibres showed minimal cellular migration and axonal outgrowth while in contrast, the biologically functionalised fibres increased cellular response significantly. Oriented suspended and biological functionalised electrospun fibres encouraged cell adhesion and migration and induced alignment of cells and extensions according to the fibre direction. Thus, the fibres developed in this thesis are a promising tool for the preparation of scaffolds for neuronal regeneration after nerve injuries

Electrospinning of Chitosan for Antibacterial Applications—Current Trends

Chitosan is a natural biopolymer that can be suitable for a wide range of applications due to its biocompatibility, rigid structure, and biodegradability. Moreover, it has been proven to have an antibacterial effect against several bacteria strains by incorporating the advantages of the electrospinning technique, with which tailored nanofibrous scaffolds can be produced. A literature search is conducted in this review regarding the antibacterial effectiveness of chitosan-based nanofibers in the filtration, biomedicine, and food protection industries. The results are promising in terms of research into sustainable materials. This review focuses on the electrospinning of chitosan for antibacterial applications and shows current trends in this field. In addition, various aspects such as the parameters affecting the antibacterial properties of chitosan are presented, and the application areas of electrospun chitosan nanofibers in the fields of air and water filtration, food storage, wound treatment, and tissue engineering are discussed in more detail

Direct in vitro electrospinning with polymer melts

The electrospinning of polymer melts can offer an advantage over solution electrospinning, in the development of layered tissue constructs for tissue engineering. Melt electrospinning does not require a solvent, of which many are cytotoxic in nature, and the use of nonwater soluble polymers allows the collection of fibers on water or onto cells. In this article, melt electrospinning of a blend of PEO-block-PCL with PCL was performed with in vitro cultured fibroblasts as the collection target. The significant parameters governing electrospinning polymer melts were determined before electrospinning directly onto fibroblasts. In general, a high electric field resulted in the most homogeneous and smallest fibers, although it is important that an optimal pump rate to the spinneret needs to be determined for different configurations. Many parameters governing melt electrospinning differ to those reported for solution electrospinning: the pump rate was a magnitude lower and the viscosity a magnitude higher than successful parameters for solution electrospinning. Cell vitality was maintained throughout the electrospinning process. Six days after electrospinning, fibroblasts adhered to the electrospun fibers and appeared to detach from the underlying flat substrate. The morphology of the fibroblasts changed from spread and flat, to long and spindle-shaped as adherence onto the fiber progressed. Therefore, an important step for producing layer-on-layer tissue constructs of cells and polymers in view of scaffold construction for tissue engineering was successfully demonstrated. The process of using cultured cells as the collection target was termed "direct in vitro electrospinning"