A novel group of silsesquioxane derivatives, which are siloxane-silsesquioxane resins (S4SQ), was for the first time examined as possible flame retardants in polypropylene (PP) materials. Thermal stability of the PP/S4SQ composites compared to the S4SQ resins and neat PP was estimated using thermogravimetric (TG) analysis under nitrogen and in air atmosphere. The effects of the non-functionalized and n-alkyl-functionalized siloxane-silsesquioxane resins on thermostability and flame retardancy of PP materials were also evaluated by thermogravimetry-Fourier transform infrared spectrometry (TG-FTIR) and by cone calorimeter tests. The results revealed that the functionalized S4SQ resins may form a continuous ceramic layer on the material surface during its combustion, which improves both thermal stability and flame retardancy of the PP materials. This beneficial effect was observed especially when small amounts of the S4SQ fillers were applied. The performed analyses allowed us to propose a possible mechanism for the degradation of the siloxane-silsesquioxane resins, as well as to explain their possible role during the combustion of the PP/S4SQ composites.
The impact of the addition of the nanofiller -halloysite -on the mechanical, physicochemical and biological properties of a nanocomposite, in which thermoplastic polyurethane fulfilled the role of the matrix was investigated. The nanocomposite was obtained by extrusion in three variants with 1, 2 and 3 wt % halloysite. The nanostructure of the obtained materials was confirmed using Atomic Force Microscopy (AFM). Based on the mechanical tests carried out, it was proven that the obtained nanocomposites were characterized by a tensile modulus greater than the polyurethane constituting the matrix. The density and hardness of the nanocomposites had changed within error limits compared to unmodified polyurethane. Biological tests showed no cytotoxicity of all the tested materials to normal human dermal fibroblasts (NHDF). Degradation tests were carried out in artificial plasma and showed that samples with 2 wt % halloysite addition had the best ratio of tensile strength and elongation at break to elasticity modulus.
Thermoplastic starch (TPS)/ethylene vinyl acetate (EVA) blends compatibilized with polyethylene-graft-maleic anhydride (PE-g-MA) were prepared from various native starches (potato, maize and waxy maize) and subjected to multiple extrusion cycles. Source of starch has significant impact on its composition, hence properties of obtained TPS and their blends with EVA. Higher content of amylopectin in waxy maize starch, comparing to other types, enhanced the mechanical performance and increased tensile strength and elastic modulus even by 41 and 71%, respectively. Such effect was related to the branching of amylopectin and was confirmed by SEM analysis of fracture areas, which showed more ductile behavior for blends with higher content of amylose. Multiple processing had beneficial impact on the performance of blends, due to the increasing compatibility and more homogenous structure after additional processing time. FTIR analysis indicated higher extent of compatibilization reaction, which, together with finer morphology, resulted in the enhancement of mechanical performance. Such effect is very beneficial from application point of view, because materials can be reprocessed without the loss of properties.
Purpose: Thermoplastic polyurethanes (TPU) found application in mining. Due to the
excellent processing properties, thermoplastic polyurethanes can be also use to make
elements that would facilitate miner's work. These elements, however, differ in dimensions
depending on the person who is going to use them, that is why they should be personalized.
In case of all the above studies, the elements or stuffs were made by means of the injection
method. This method limits the possibility of producing mining’s stuff only to models that
have a mould. The 3D printing technology developing rapidly throughout the recent years
allows for high-precision, personalized elements’ printing, made of thermoplastic materials.
Design/methodology/approach: The samples from thermoplastic polyurethanes were
made using 3D printing and then subjected to the aging process at intervals of 2, 7 and 30
days. The samples were then subjected to a static tensile tests, hardness tests and FT-IR
spectroscopy.
Findings: The obtained results of mechanical tests and IR analyses show that the aging
process in mine water does not affect the mechanical properties of the samples regardless
of the aging time. IR spectral analysis showed no changes in the structure of the main and
side polyurethane chains. Both mechanical and spectral tests prove that polyurethanes
processed using 3D printing technology can be widely used in mining.
Research limitations/implications: Only one type of TPU was processed in this work.
Further work should show that synthetic mine water does not degrade the mechanical
properties of other commercially available TPUs.
Practical implications: The additive technology allows getting elements of mining
clothing, ortheses, insoles or exoskeleton elements adapted to one miner.
Originality/value: The conducted tests allowed to determine no deterioration of the
mechanical properties of samples aged in synthetic mine water. TPU processing using 3D
printing technology can be used in mining.
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