Valorization of lignin in polymer and composite systems for advanced engineering applications – A review

Polymer/lignin blends: Interactions, properties, applications

An accurate and reliable Indoor Positioning System (IPS) applicable to most indoor scenarios has been sought for many years. The number of technologies, techniques, and approaches in general used in IPS proposals is remarkable. Such diversity, coupled with the lack of strict and verifiable evaluations, leads to difficulties for appreciating the true value of most proposals. This paper provides a meta-review that performed a comprehensive compilation of 62 survey papers in the area of indoor positioning. The paper provides the reader with an introduction to IPS and the different technologies, techniques, and some methods commonly employed. The introduction is supported by consensus found in the selected surveys and referenced using them. Thus, the meta-review allows the reader to inspect the IPS current state at a glance and serve as a guide for the reader to easily find further details on each technology used in IPS. The analyses of the meta-review contributed with insights on the abundance and academic significance of published IPS proposals using the criterion of the number of citations. Moreover, 75 works are identified as relevant works in the research topic from a selection of about 4000 works cited in the analyzed surveys.

https://www.mdpi.com/1424-8220/19/20/4507/pdf

A Meta-Review of Indoor Positioning Systems.

The production of carbon fibers based on lignin reduces the cost and the environmental impact associated with carbon fiber manufacturing. However, the melt processing of lignin as a carbon fiber precursor is challenging due to its brittleness and limited thermoplastic behavior. For this reason we produce biopolymer blends based on Alcell organosolv hardwood lignin, hydroxypropyl modified Kraft hardwood, and a thermoplastic elastomer polyurethane (TPU). Samples with TPU content greater than 30% showed excellent melt processability and carbonization yield (35% carbon yield for the samples containing 30% of TPU). The thermal properties were analyzed by differential scanning calorimetry, rheology and thermogravimetric analysis. Fourier infrared measurements were utilized to explain the lignin/TPU interactions which governed the thermal and rheological behavior of the blends. SEM analysis showed that the blends produce a homogeneous structure which was void free after carbonization. These structurally compleme...

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Biobased Structurally Compatible Polymer Blends Based on Lignin and Thermoplastic Elastomer Polyurethane as Carbon Fiber Precursors

Chemical modification of lignocellulosic materials, especially as a pre-treatment in nanocellulose production, has mainly been conducted with lignin-free bleached cellulose pulps. However, non-bleached pulp exhibits several advantages over bleached pulp, namely excluding of the use of hazardous bleaching chemicals, higher yield, and lower cost. In this study, the chemical modification of lignocellulose (groundwood pulp, GWP) with a high lignin content (27.4 wt%) was investigated using a deep eutectic solvent (DES) as a reaction medium. A low-melting DES was easily obtained within one hour by mixing triethylmethylammonium chloride (TEMACl) and imidazole at room temperature. Carboxylated GWP was obtained by adding succinic anhydride to the DES. Under mild reaction conditions (2 h at 70 °C), carboxylic acid contents of 1.88–3.34 mmol g−1 were obtained depending on the anhydride dosage used (5–20 mmol/1 g of pulp) with excellent yield (over 90%). The GWP was more reactive in the pre-treatment step, measuring carboxylic acid contents higher than those of bleached cellulose pulps treated under identical reaction conditions (containing less than 0.5 wt% lignin). After deprotonation of the carboxylic acid groups, highly anionic wood nanofibers (AWNFs) were produced using a microfluidizer. Vacuum filtration was applied in the preparation of self-standing films, which had good mechanical properties and were transparent. The fabricated AWNFs have many potential uses—for instance, in sustainable water purification because of their adjustable surface charge.

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Anionic wood nanofibers produced from unbleached mechanical pulp by highly efficient chemical modification

Polymer/lignosulfonate blends were prepared from three polymers containing an aromatic moiety in their chain: polystyrene (PS), polycarbonate (PC), and a glycol modified poly(ethylene terephthalate) (PETG), in order to study the effect of aromatic, π electron interactions on miscibility and on the structure and properties of the blends. Polypropylene (PP)/lignin blends were used as a reference. The components were homogenized in an internal mixer and compression molded into plates of 1 mm thickness. Structure was characterized by scanning electron microscopy (SEM) and image analysis, while mechanical properties were characterized by tensile testing and acoustic emission measurements. Component interactions were estimated from solubility parameters, the composition dependence of glass transition temperature, and mechanical properties. The results indicated that π electron interactions result in better compatibility than the dispersion forces acting in PP blends. The average size of the dispersed lignin par...

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Competitive Interactions in Aromatic Polymer/Lignosulfonate Blends

Structure, properties and interactions in ionomer/lignin blends

The paper proposes three different multiplexing methods that can be applied in a Visible Light Communication-based indoor-positioning system. Our solutions realize the positioning algorithms via simple means which do not influence the light sources' performance significantly. The measurement results show that the proposed procedures are suitable for precise indoor-positioning applications.

Experimental investigation of multiplexing methods in Visible Light Communication system for indoor positioning

The visible light communication (VLC) with LED lamps is a very promising technique which can be a possible alternative to certain simplex radio connections aiming to relieve the quickly saturating radio frequency domain. The advantages of visible light communication can be exploited by indoor applications most efficiently. Because - similarly to radio communications - it may be necessary to run more connections simultaneously, the signals of each transmitter must be discriminable. A certain method that ensures the discriminability of signals is code division multiplexing (CDM). In this multiplexing method the channels share a common frequency band but the signals of different transmitters use digital modulation with different quasi-orthogonal codes. In my study I show step-by-step how to realize a VLC CDM system. I approximate the parameters of a system of this type by simulation models, design the software to real-time communication and verify the functionality of VLC CDM scheme with visible light demonstration circuits.

Investigation of code division multiplexing technique for VLC-based indoor positioning

This paper introduces a novel driving circuit for power LEDs that is capable of effectively utilizing the OOK modulation for visible light communication applications. The circuit uses the carrier drawing-out technique and consists of cheap discrete elements, so total cost can be kept low which is a must for future integration in lighting systems.

Gábor Szabó

Papers

Competitive Interactions in Aromatic Polymer/Lignosulfonate Blends

Structure, properties and interactions in ionomer/lignin blends

Experimental investigation of multiplexing methods in Visible Light Communication system for indoor positioning

Investigation of code division multiplexing technique for VLC-based indoor positioning

Carrier drawing-out power LED driver with cost-effective discrete parts