Arūnas Baltušnikas

Properties of mechanically recycled polycaprolactone-based thermoplastic polyurethane/polycaprolactone blends and their nanocomposites

In this study, the effect of mechanical recycling process parameters on the morphology, properties, and hydrolytic degradation of polycaprolactone-based thermoplastic polyurethane/polycaprolactone waste blends (TPU-PCL/PCL) and their nanocomposites were investigated. Modification of recycled TPU-PCL/PCL was carried out using natural and organically modified montmorillonite nanoclays. Effect of reprocessing time on the structure of TPU-PCL/PCL and nanoclay separation in nanocomposites was evaluated by differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy analysis. It has been demonstrated that mechanical recycling of waste from industrial TPU-PCL/PCL only marginally changes its properties. The exfoliation of Cloisite 30B clay was not enough to enhance the properties of recycled materials. However, the structure, thermal, and mechanical properties, hydrolytic degradation of obtained recycled TPU-PCL/PCL:nanoclay nanocomposites depend on the separation level of the nanoclays.

Modified xonotlite–type calcium silicate hydrate slabs for fire doors

Xonotlite-type calcium silicate hydrate slabs were examined under the thermal shock conditions in a solar furnace at the Plataforma Solar de Almeria which can reach a peak of 300 W/cm2. We have studied the original slabs as well as those modified with a mixture of liquid sodium silicate including montmorillonite as thermal insulation materials for fire doors applications. The slabs were kept at 950°C for 1 h. We performed X-ray diffraction, thermogravimetry and differential scanning calorimetry analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermal conductivity measurements and determined N2 adsorption/desorption isotherms. X-ray diffraction shows that during the thermal shock at 950°C xonotlite is converted to wollastonite. Specific surface areas of xonotlite slabs decrease due to release of crystalline water molecules. It is possible to maintain temperatures of the back door not exceeding 70°C while the front door is subjected to 950°C for 1-h time periods. The standard requires no more than 140°C at the back door.

Utilization of sewage sludge-biomass gasification residue in cement-based materials: effect of pozzolant type

ABSTRACT In this study, the viability to utilize the residue, obtained from a sewage sludge (SS) and biomass combustion/gasification plant (GR), in cement-based materials was analysed. Two pozzolanic materials were selected to make GR more recyclable: metakaolin (MK) and spent catalyst waste (Z), received from fluidized-bed catalytic cracking process. Functional and environmental properties of standard cement pastes and mortars as well as binary and ternary combinations of GR with MK and Z were assessed. Results showed that enhanced mechanical strength, reduced water absorption and heavy metals release were obtained for compositions when GR was combined with one of the pozzolanic material MK or Z. Microstructural analysis revealed that due to addition of pozzolan the surface of GR particles was covered by a layer of hydration products. In particular, the use of MK led to the formation of more porous layer whereas application of Z tends to the formation of a dense-layered structure on the surface of GR. N2 sorption results showed that contrary to MK the incorporation of Z into cement composition with GR reduced volume of small capillary pores, and therefore, resulted in lower water absorption and heavy metals release. The obtained results suggest that the application of Z appears to be advantageous pozzolan for the stabilization of SS-biomass gasification residue in cement-based materials.

Modification of structure of synthetic gyrolite

Abstract Gyrolite (calcium silicate hydrate), pure and organically modified, was studied by XRD, DSC, TG and FTIR spectroscopy. X-ray diffraction results show the size of gyrolite particles between 10 and 50 nm. SEM results show that synthetic gyrolite with intercalated Na+ ions morphology is characterised as a plate/fibre shape structure and is suitable for modification of gyrolite with octadecylammonium chloride. The chloride molecules fill the interlayer space of pure gyrolite without forming chemical bonds. When gyrolite with intercalated sodium ions is modified, exchangeable sodium cations are replaced by organic modifier ions forming the chemical bonds with gyrolite atoms.