Kamila Salasinska

The effect of filler chemical constitution and morphological properties on the mechanical properties of natural fiber composites

The purpose of this work was to obtain environmentally friendly natural fibre composites (NFC) from high-density polyethylene (PE-HD) foil and either finely ground sunflower husk or pistachio shells, which both possess physico-mechanical characteristics similar to wood-polymer composite. The composites were prepared from waste materials without the use of additives. It was found that 66% of the sunflower husk grains were from 180 to 850 μm in size, and 88% of the pistachio shell particles were less than 63 μm in size. With the use of a rolling mixer, six mixtures were produced with filler shares amounting to 5, 15 and 30 wt.% of sunflower husk and 15, 35 and 55% of pistachio shell, from which dumbbell-shaped samples were formed via injection processing. The produced materials were analysed for their mechanical properties (impact strength, hardness, tensile strength, Young’s modulus and DMA). The morphologies and chemical composition of the filler as well as the morphological properties of the composites (SEM) were also investigated. The chemical constitution and shape of the filler particles affected the investigated properties of the obtained NFC, and the results were especially significant for the properties of impact strength, stiffness and tensile strength.

Natural fibre composites from polyethylene waste and hazelnut shell: dimensional stability, physical, mechanical and thermal properties

Within the framework of this study, the physical modification of high-density polyethylene waste foil was performed using finely ground hazelnut flour to produce a composite whose physical, mechanical and flammable properties make it possible to use inside and outside of buildings. Three mixtures were produced with filler shares of 11, 26 and 42 vol.% using equipment that is normally used in polymer processing, and no refining additives were applied. The produced materials were analysed for their processing (mass flow ratio), physical (density and moisture content) and mechanical properties (tensile strength, elongation at break and dynamic thermal analysis) and resistance to environmental factors (swelling and water absorption, thermogravimetric analysis and combustion heat). The particle size distribution of the filler and morphological properties of the composites (scanning electron microscopy) were also investigated. It was vital to obtain an inexpensive material with low absorptivity. The resulting materials are characterised by a low density, acceptable low absorptive and good mechanical properties; also, they can constitute an important fuel once their practical properties have been exploited.

Analysis of flammability and smoke emission of rigid polyurethane foams modified with nanoparticles and halogen-free fire retardants

Using one-step method, rigid polyurethane foams were made, modified with developed fire retardant systems containing halogen-free flame retardants and nanofillers in the form of multi-walled carbon nanotubes or nanoscale titanium dioxide. The materials were subjected to a test using a cone calorimeter and smoke-generating chamber, and selected samples were further analyzed via thermogravimetry and oxygen index. Moreover, the products of thermal degradation of selected samples were identified using gas chromatography with mass spectrometer. Conducted flammability tests confirmed the presence of a synergistic effect between the used nanofillers and halogen-free flame retardants. It has been observed that the carbonized layer, the formation of which favored the presence of nanoadditives, inhibits the combustion process. Furthermore, nanofillers influenced favorably reduction in the amount and the number of occurring products of thermal degradation.

Thermal stability, fire behavior, and fumes emission of polyethylene nanocomposites with halogen-free fire retardants

Funding information Ministry of Science and Higher Education/ National Center for Research and Development, Grant/Award Number: III.P.01 Abstract The synergism between nanoparticles and different kinds of halogen-free fire retardants leading to reduction in flammability and smoke generation of polyethylene was investigated. The composites were evaluated by thermogravimetric analysis, oxygen index test, cone calorimeter measurements, and a singlechamber test. Moreover, the semivolatile and volatile compounds evolved in the thermal degradation processes of polyethylene were determined using a steady state tube furnace and gas chromatograph with mass spectrometer. Morphological and structural characteristics as well as thermomechanical properties of the composites were characterized using various techniques including scanning electron microscopy (SEM), Xray diffraction (XRD), and dynamic mechanical thermal analysis (DMTA). The obtained data were compared to the results received for polyethylene and polymer with brominecontaining fire retardants. The incorporation of nanofillers and halogenfree fire retardants caused a reduction in combustibility as a consequence of the formation of char. Furthermore, the presence of nanoparticles has a beneficial effect on the inhibition of dripping. The polyethylene with carbon nanotubes, zinc borate, and aluminum hydroxide exhibited better combined properties of fire behavior and production of nontoxic smoke compared to the remaining composition and reference materials.