Windshield recycling focused on effective separation of PVB sheet

The study is focused on windshield recycling process resulting in poly(vinyl butyral) (PVB) sheets with very low amout of remain glass particles. PVB sheets were obtained from worldwide manufacturer DuPont and then they were laminated by standard autoclaving process. One sample of PVB sheet was modified by multi‐functional organic acid in order to compare various levels of adhesion. Three‐stage technology was proposed for recycling PVB sheets. In the first‐stage laminated safety glass was mechanically cracked. In the second‐stage the adhesion reduction to minimal degree was followed by chemical‐physical assisted separation. It causes self‐release of the glass out of the PVB sheet. The third‐stage was mechanical peeling of the remaining glass from the PVB sheet which completed the recycling process. The optimal process conditions for the most effective delamination process were found. Delamination technology produces PVB sheet with minimal residual glass content (up to 300 ppm) and minimal change in PVB sheet properties. Described recycling technology is ecologically friendly (the effluent is fully recyclable as well) and could reduce the worldwide problem with windshield waste disposal. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39879.     

Preparation of CaCO3‐based biomineralized polyvinylpyrrolidone–carboxymethylcellulose hydrogels and their viscoelastic behavior

In the blend of natural and synthetic polymer‐based biomaterial of polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC), fabrication of CaCO₃ was successfully accomplished using simple liquid diffusion technique. The present study emphasizes the biomimetic mineralization in PVP–CMC hydrogel, and furthermore, several properties of this regenerated and functionalized hydrogel membranes were investigated. The physical properties were studied and confirmed the presence of CaCO₃ mineral in hydrogel by Fourier transform infrared spectroscopy and Scanning electron microscopy. Moreover, the absorptivity of water and mineral by PVP–CMC hydrogel was studied to determine its absorption capacity. Further, the viscoelastic properties (storage modulus, loss modulus, and complex viscosity) of mineralized and swelled samples (time: 5–150 min) were measured against angular frequency. It is interesting to know the increase of elastic nature of mineralized hydrogel filled with CaCO₃ maintaining the correlation between elastic property and viscous one of pure hydrogel. All these properties of biomineralized hydrogel suggest its application in biomedical field, like bone treatment, bone tissue regeneration, dental plaque and tissue replacement, etc. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40237.     

Analysis of polymer viscoelastic properties based on compressive creep tests during hot embossing for two‐dimensional polyethylene terephthalate nanochannels

Hot embossing is an emerging technology, which enables cost‐effective and high‐productivity nanofabrication. It is important to optimize the processing parameters to achieve high replication accuracy nanostructure fabrication. In this article, to reveal the interrelationship between the hot embossing conditions and replication accuracy of two‐dimensional (2D) polyethylene terephthalate (PET) nanochannels, the numerical simulations were conducted by using the generalized Maxwell model. The constants of the generalized Maxwell model were calculated by a newly established fitting formula based on experimental compressive creep curves rather than tensile stress relaxation curves. Replication accuracy of 2D PET nanochannels was evaluated by a method based on weighted averages. Orthogonal method was employed during numerical simulations to optimize the hot embossing process. Under optimized hot embossing parameters, 2D PET nanochannels, ～80 nm wide, 250 nm deep and 4 mm long, were precision‐imprinted into a PET sheet. POLYM. ENG. SCI., 54:2398–2406, 2014. © 2013 Society of Plastics Engineers     

Hierarchically Structured Surfaces Prepared by Phase Separation: Tissue Mimicking Culture Substrate

The pseudo 3D hierarchical structure mimicking in vivo microenvironment was prepared by phase separation on tissue culture plastic. For surface treatment, time-sequenced dosing of the solvent mixture with various concentrations of polymer component was used. The experiments showed that hierarchically structured surfaces with macro, meso and micro pores can be prepared with multi-step phase separation processes. Changes in polystyrene surface topography were characterized by atomic force microscopy, scanning electron microscopy and contact profilometry. The cell proliferation and changes in cell morphology were tested on the prepared structured surfaces. Four types of cell lines were used for the determination of impact of the 3D architecture on the cell behavior, namely the mouse embryonic fibroblast, human lung carcinoma, primary human keratinocyte and mouse embryonic stem cells. The increase of proliferation of embryonic stem cells and mouse fibroblasts was the most remarkable. Moreover, the embryonic stem cells express different morphology when cultured on the structured surface. The acquired findings expand the current state of knowledge in the field of cell behavior on structured surfaces and bring new technological procedures leading to their preparation without the use of problematic temporary templates or additives.     

The Influence of the Material Structure on the Mechanical Properties of Geopolymer Composites Reinforced with Short Fibers Obtained with Additive Technologies

Additive manufacturing technologies have a lot of potential advantages for construction application, including increasing geometrical construction flexibility, reducing labor costs, and improving efficiency and safety, and they are in line with the sustainable development policy. However, the full exploitation of additive manufacturing technology for ceramic materials is currently limited. A promising solution in these ranges seems to be geopolymers reinforced by short fibers, but their application requires a better understanding of the behavior of this group of materials. The main objective of the article is to investigate the influence of the microstructure of the material on the mechanical properties of the two types of geopolymer composites (flax and carbon-reinforced) and to compare two methods of production of geopolymer composites (casting and 3D printing). As raw material for the matrix, fly ash from the Skawina coal power plant (located at: Skawina, Lesser Poland, Poland) was used. The provided research includes mechanical properties, microstructure investigations with the use of scanning electron microscope (SEM), confocal microscopy, and atomic force microscope (AFM), chemical and mineralogical (XRD-X-ray diffraction, and XRF-X-ray fluorescence), analysis of bonding in the materials (FT-IR), and nuclear magnetic resonance spectroscopy analysis (NMR). The best mechanical properties were reached for the sample made by simulating 3D printing process for the composite reinforced by flax fibers (48.7 MPa for the compressive strength and 9.4 MPa for flexural strength). The FT-IR, XRF and XRD results show similar composition of all investigated materials. NMR confirms the presence of SiO₄ and AlO₄ tetrahedrons in a three-dimensional structure that is crucial for geopolymer structure. The microscopy observations show a better coherence of the geopolymer made in additive technology to the reinforcement and equal fiber distribution for all investigated materials. The results show the samples made by the additive technology had comparable, or better, properties with those made by a traditional casting method.     

Three‐dimensional modeling of porosity development during the gasification of a char particle

This work is devoted to the three‐dimensional, direct modeling of porosity and specific surface development during the gasification of a char particle. The model was developed for heterogeneous reactions occurring inside a char particle in a kinetically controlled regime. The main goal of this work is to analyze the impact of different pore size distributions on the particle carbon conversion rate. In particular, it is shown that under certain conditions the outer particle surface can influence the specific surface area. In this context the possible adaptation of the parameter ψ from the random pore model (RPM) developed by Bhatia and Perlmutter is explained. The results of simulations are compared against the RPM and discussed. Additionally, based on the results of simulations, the physics behind several input parameters used by the RPM are explored. Finally, the possible fragmentation of a chemically reacting char particle during its gasification in dependence of instantaneous porosity was investigated numerically. It was shown that the earliest fragmentation occurs at a carbon conversion of about 0.5–0.6 due to the disaggregation of the pore walls. The results are discussed and compared implicitly with data published in the literature. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1638–1647, 2017     

Preparation of dehydroxylated and delaminated talc: Meta-talc

The roentgen-amorphous delaminated and dehydroxylated phase was prepared applying intensive milling procedure and subsequent thermal treatment of talc. Due to the similarity in properties and in thermal behavior of this material with roentgen-amorphous delaminated and dehydroxylated kaolinite phase, i.e. meta-kaolinite, the name meta-talc was suggested for this material. The properties and the behavior during thermal treatment were investigated using thermal analysis, x-ray diffraction analysis, infrared spectroscopy and scanning electron microscopy. The suggested procedure changes the activation energy of dehydroxylation, the behavior during thermal treatment and the phase composition of the product. The kinetics and thermodynamics of the thermal transition were evaluated using Kissinger equation and Eyering law.     

Contact Doping for Vertical Organic Field‐Effect Transistors

Doping is a powerful tool to overcome contact limitations in short‐channel organic field‐effect transistors (OFETs) and has been successfully used in the past to improve the charge carrier injection in OFETs. The present study applies this familiar concept to the architecture of vertical organic field‐effect transistors (VOFETs), which are often severely limited by injection due to their very short channel lengths. The present study shows that the performance of p‐type VOFETs with pentacene as an active material can be significantly enhanced by the addition of the common p‐dopant C₆₀F₃₆ as a thin injection layer underneath the VOFET source electrode, resulting in an increase of On‐state current and On/Off ratio by one order of magnitude. The present study further investigates mixed injection layers of pentacene and the p‐dopant and finds that the improvement is less pronounced than for the pure dopant layers and depends on the concentration of dopant molecules in the injection layer. Through application of the transfer length method to equivalent OFET geometries, the present study is finally able to link the observed improvement to a decrease in transfer length and can thus conclude that this length is a crucial parameter onto which further improvement efforts have to be concentrated to realize true short‐channel VOFETs.     

Twinned Growth of Metal‐Free,Triazine‐Based Photocatalyst Films as Mixed‐Dimensional (2D/3D) van der Waals Heterostructures

Design and synthesis of ordered, metal‐free layered materials is intrinsically difficult due to the limitations of vapor deposition processes that are used in their making. Mixed‐dimensional (2D/3D) metal‐free van der Waals (vdW) heterostructures based on triazine (C₃N₃) linkers grow as large area, transparent yellow‐orange membranes on copper surfaces from solution. The membranes have an indirect band gap (E _g,opt = 1.91 eV, E _g,elec = 1.84 eV) and are moderately porous (124 m² g^?1). The material consists of a crystalline 2D phase that is fully sp² hybridized and provides structural stability, and an amorphous, porous phase with mixed sp²–sp hybridization. Interestingly, this 2D/3D vdW heterostructure grows in a twinned mechanism from a one‐pot reaction mixture: unprecedented for metal‐free frameworks and a direct consequence of on‐catalyst synthesis. Thanks to the efficient type I heterojunction, electron transfer processes are fundamentally improved and hence, the material is capable of metal‐free, light‐induced hydrogen evolution from water without the need for a noble metal cocatalyst (34 µmol h^?1 g^?1 without Pt). The results highlight that twinned growth mechanisms are observed in the realm of “wet” chemistry, and that they can be used to fabricate otherwise challenging 2D/3D vdW heterostructures with composite properties.