High-performance polyethylene fibers, renowned for their superior attributes encompassing a high strength, modulus, and lightness, are conventionally manufactured through the gel spinning method. However, this method is encumbered by several drawbacks, including the requisite application of a separate process to eliminate solvents from the fibers and the utilization of chemicals deleterious to both the environment and human health. Alternatively, the adoption of the melt spinning method presents a cleaner and environmentally friendly approach to attain high-performance fibers. In the present investigation, high-density polyethylene (HDPE) fibers were produced employing the melt spinning method. After the spinning process, strategic orientation procedures were implemented to enhance the crystallinity of the spun fibers. As a concluding step, seeking to elevate the overall performance of the oriented spun HDPE fibers, a cross-linking treatment was applied via UV irradiation. Notably, this study pioneers the incorporation of polyhedral oligomeric silsesquioxane (POSS) hybrid nanoparticles into HDPE during melt spinning, presenting a novel advancement aimed at further enhancing the mechanical properties of oriented HDPE fibers during UV irradiation. For this purpose, two distinct types of POSS, namely octavinyl POSS (OVPOSS) and methacryl POSS (MACPOSS), both having unsaturated double bonds capable of participating in the network structure of oriented HDPE spun during UV cross-linking, were used. The thermal, morphological, and mechanical properties, as well as the crystal structure of samples with and without POSS molecules, were investigated. The mechanical properties of the fibers exhibited higher values in the presence of OVPOSS. The incorporation of OVPOSS and MACPOSS resulted in a noteworthy improvement in the material’s tensile strength, exhibiting a marked increase of 12.5 and 70.8%, respectively. This improvement can be attributed to the more homogeneous dispersion of OVPOSS in HDPE, actively participating in the three-dimensional network structure. After orientation and UV irradiation, the tensile strength of HDPE fibers incorporating OVPOSS increased to 293 MPa, accompanied by a concurrent increase in the modulus to 2.8 GPa. The addition of POSS nanoparticles thus yielded a substantial improvement in the overall performance of HDPE fibers.

The aim of this study was to produce crosslinked low-density polyethylene (LDPE) composites using peroxide and octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) and to examine the shape memory behavior. The strategy was to use OvPOSS as a coagent to increase the crosslinking density and crosslinking efficiency while improving the mechanical and shape memory properties as well. The peroxide concentration, from 0.5 phr to 3.0 phr, was taken as the experimental parameter, with 4 phr OvPOSS added to all composites. The melt mixing route was applied similar to that which would be used industrially. The thermo-responsive shape memory properties near the melting point were examined in tension mode. The dispersion of OvPOSS in the LDPE matrix was observed via scanning electron microscopy and Si-mapping. In addition, the thermal, mechanical, structural, and rheological features of the novel LDPE/OvPOSS and LDPE/peroxide/OvPOSS systems were investigated. It was observed that the crosslinking density of LDPE increased in the presence of OvPOSS, which affected the mechanical, rheological and thermal properties and increased the shape recovery ratio of the LDPE.

Autoclaved aerated concrete (AAC) thermal insulation board has a density of 130–155 kg/m³, a compressive strength above 0.4 MPa and a thermal conductivity value of 0.045 W/m.K. It is a Class A non-combustible, mineral-based and non-toxic material and used for thermal insulation from the outside, inside, in the middle, underground, on floors, and roof surfaces. The porous structure of the material decisively affects its mechanical and thermal conductivity properties. In this study, the potential for pore size reduction was evaluated by adding ratios of 0%, 0.1%, 0.25%, 0.5%, 0.75% and 1% amorphous silica-forming additive to the AAC thermal insulation board by mass. Furthermore, the mechanical performance was compared with the corresponding pore size characteristics. In determining the pore distribution, the air pores in the structure were examined by image analysis technique based on the Monte Carlo approach. When the density and compressive strength of the samples obtained after hydrothermal curing were compared with the A value, it was observed that the highest increase was 29.94% with a 1% additive rate. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses showed that the amount of tobermorite increased continuously up to a dosage of 0.5%. The fact that the addition of the admixture by mass reduces the pore diameter, reduces density and increases compressive strength reveals that the amorphous silica-forming additive is usable in AAC thermal insulation board. Achieving the same compressive strength with less material during the production phase and reducing per-unit energy consumption during service due to improved thermal insulation associated with smaller pore sizes are critical for lowering the carbon footprint.

Autoclaved aerated concrete (AAC) is a building material with low density compared to traditional and structurally lightweight concrete. In addition to being very light, it is frequently preferred in many different areas, especially in external walls, floor slabs, lintels, roof slabs and panel elements of buildings, since it offers good heat and sound insulation. When the AAC production process is evaluated in terms of energy requirement, it has high environmental sensitivity compared to traditional concrete and brick processes. Since environmental sensitivity has become more important today, it was desired to evaluate the waste casting sands (WCS) generated in metal casting companies within the scope of the study. In this study, the usability of WCS as an alternative instead of silica sand used in AAC production was investigated. For this purpose, WCS was provided by 3 different casting companies. The usability potential of WCSs at 30% was examined and the quality of AAC was compared with reference castings. The fineness potentials of WCSs were compared by grinding in a disc mill. First of all, X-ray fluorescence spectrometry (XRF) and grain size analyses were performed on WCSs. 150x150x150 mm3 sized AAC laboratory samples were produced. The produced AAC samples were kept in the oven at 60°C until they set and then cured in an autoclave for approximately 10 hours. After the curing process in the autoclave, analyses such as compressive strength analyses and dry unit weight measurements were performed on the samples, and in addition to these analyses, they were subjected to visual examinations. Mechanical analyses were performed by replacing the WCS, from which positive results were obtained, at 5 different substitution ratios of 5, 10, 15, 20, and 30% by weight. From scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, it was determined that tobermorite structures were formed. From thermal analyses, it was observed that the thermal stability of the samples produced with WCS was better. When the results were evaluated in general, it was found that up to 30% WCS could be included in the AAC production system. In addition, an increase in compressive strength values occurred. The improvement in compressive strength also showed that WCS could be a good alternative source to silica sand.

This study investigates the effect of branching of linear low-density polyethylene (LLDPE) and POSS types on thermal, mechanical, and rheological properties and shapes memory behavior of crosslinked LLDPE/POSS composites using different concentrations of peroxide (PRX). Shape memory polymers (SMPs) are intelligent materials that can recall their original shape from the temporary shape by applying an external stimulus such as temperature and pH when they are deformed. In this work, polyethylene (PE) copolymers of 1-octene (LLDPE C8) and 1-hexene (LLDPE C6) were utilized as the PE types. Di-tert-butyl cumyl peroxide was used as peroxide in 0.5, 1, 2, and 3 phr ratios. Octavinyl POSS (OvPOSS) and Octaisobutyl POSS (OibPOSS) were used as potent co-agents. The composites were prepared in an Xplore micro-compounder. The crosslinking was carried out using a hot press. The composites were characterized by performing rheological, thermal, and shape memory tests. It was found that the viscosity, storage modulus, and crosslinking density of composites increased in the presence of OvPOSS than that of composites including OibPOSS; however, the gelation times decreased as PRX amount increased. Plasticizing effect of OibPOSS was obtained from rheology test results. It was observed from shape memory tests that OibPOSS decreased shape recovery ratio whereas OvPOSS increased. When the PE types were compared, the highest shape memory results were obtained with LLDPE C6.