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    A comprehensive review of the recent developments in thermoplastics and rubber blends-based composites and nanocomposites
    (Wiley, 2023) Urtekin, Gizem; Ullah, Muhammad Saeed; Yildirim, Rumeysa; Ozkoc, Guralp; Kodal, Mehmet
    Various blends and composites have been prepared during the past decade to address limitations, including the poor mechanical properties of polymers, or to balance out the high cost of synthetic polymers. Rubber-based thermoplastic blends and composites are being developed to attain improved performance and balanced qualities for usage in a variety of industries, including automotive, packaging, home products, space technology, and biomedical. Thermoplastics can be produced via standard manufacturing procedures and have outstanding qualities like low density, good chemical resistance, and heat resistance. However, rubbers are being used because of their elastic attributes, including their resilience, impact resistance, and good tear strength. These two materials work well together when blended or combined. In this article, an effort was made to narrow the gap between rubbers and thermoplastics. The mechanical, rheological, and morphological properties of the rubber/thermoplastic blends and composites/nanocomposites containing various types of conventional fillers and nanofillers were discussed comprehensively. Blends of these materials can provide too easier melt processing as well as financial benefits. The flexible nature and damping properties of rubber and better thermal stability and thermoplastic processability contributed to the development of high-performance rubber/thermoplastic composites with better ductility, impact strength, and stiffness. Rubber reduced the high brittleness of thermoplastics because of its resilience and damping properties. In contrast, the poor processability and weak chemical resistance of rubbers were overcome via better processability and higher stiffness of thermoplastics. Rubber-based thermoplastic composites and nanocomposites have been reported to offer greater flexibility, better processing, high impact strength, and chemical resistance.HighlightsThe properties of rubber/thermoplastic blends were discussed in this article.More recent advancements in rubber/thermoplastic blends were evaluated.Morphological properties depend on the rubber/thermoplastic blend ratio.The addition of reinforcements affects the rheological properties.Dispersion of additives and blend ratio influence the mechanical properties. Rubber/thermoplastic blends and composites.image
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    Development of Electrically Conductive Wood-Based Panels for Sensor Applications
    (MDPI, 17.11.2024) Kocoglu, Ozden Beste; Pretschuh, Claudia; Unterweger, Christoph; Kodal, Mehmet; Ozkoc, Guralp
    This study investigates the development of electrically conductive panels for application as emergency detection sensors in smart house systems. These panels, composed of wood chips coated with polymeric methylene diphenyl isocyanate, were modified with carbon black and carbon fibers to enable detection of moisture, temperature, and pressure variations. Manufactured via hot pressing, the panels retained standard mechanical properties and exhibited stable performance under diverse environmental conditions. Carbon black-filled panels achieved electrical percolation at a lower filler concentration (5%) compared to carbon fiber-filled panels. The incorporation of carbon black reduced the electrical resistivity to 8.6 ohm·cm, while the addition of carbon fibers further decreased it to 7.7 ohm·cm. In terms of sensor capabilities, panels containing carbon fibers demonstrated superior sensitivity to moisture and pressure changes. However, carbon black was ineffective for temperature sensing. Among the carbon fiber-filled panels, those with 20 wt.% concentration exhibited the best performance for moisture and pressure detection, whereas panels with 40 wt.% carbon fiber content displayed the most reliable and consistent temperature-sensing properties.
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    Improved Heat Dissipation of NR/SBR-Based Tire Tread Compounds via Hybrid Fillers of Multi-Walled Carbon Nanotube and Carbon Black
    (Mdpi, 2023) Kodal, Mehmet; Cakir, Nazli Yazici; Yildirim, Rumeysa; Karakaya, Nursel; Ozkoc, Guralp
    The development of thermally conductive rubber nanocomposites for heat management poses a formidable challenge in numerous applications, notably within the realm of tire technology. Notably, rubber materials are characterized by their inherently low thermal conductivity. Consequently, it becomes imperative to incorporate diverse conductive fillers to mitigate the propensity for heat build-up. Multi-walled carbon nanotubes (MWCNTs), as reinforcement agents within the tire tread compounds, have gained considerable attention owing to their extraordinary attributes. The attainment of high-performance rubber nanocomposites hinges significantly on the uniform distribution of MWCNT. This study presents the influence of MWCNTs on the performance of carbon black (CB)-reinforced natural rubber (NR)/styrene butadiene rubber (SBR) tire compounds prepared via high shear melt mixing. Morphological analysis showed a good distribution of MWCNTs in the NR/SBR/CB compound. The vulcanization parameters, such as the maximum and minimum torque, cross-linking density, hardness, abrasion resistance, tensile strength, and Young modulus, exhibited a progressive improvement with the addition of MWCNT. Remarkably, adding MWCNT into CB improved the heat conductivity of the NR/SBR/CB compounds, hence decreasing the heat build-up. A percolation mode was also proposed for the hybrid carbon fillers based on the data obtained.
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    Investigation of effects of MoEpPOSS nanoparticle on the morphological and rheological properties of PA6/TPE blends
    (İdris Karagöz, 31 Temmuz 2024) Yıldırım, Rumeysa; Koçoğlu, Hürol; Ün, Merve; Ullah, Muhammad Saeed; Yakar, İpek; Ozkoc, Guralp; Mert, Olcay; Kodal, Mehmet
    Polyamide 6 (PA6) is one of the used engineering thermoplastics with the advantages of high resistance to chemicals and abrasion, high fatigue resistance and toughness. However, it has some disadvantages such as low impact strength and notch sensitivity. The blend of PA6 with elastomers can mitigate these shortcomings. Lately, thermoplastic elastomers (TPE) have been frequently used to toughen notch-sensitive polymers such as PA6 due to their outstanding properties such as high elasticity, recyclability, and easy processing. As it is known, obtaining superior properties in polymer blends relies on the interfacial interaction between the components of the blend. Additionally, by using compatibilizers, blends with the required properties can be created by enhancing interaction between phases, or interfacial adhesion. Recently, polyhedral oligomeric silsesquioxane (POSS) nanoparticles, organic/inorganic hybrid nanoparticles, are preferred as an alternative compatibilizer to conventional types. In this study, PA6/TPE blends were compatibilized with POSS nanoparticle with single epoxy group (MoEpPOSS). The morphological and rheological properties of PA6/TPE blends compatibilized with MoEpPOSS nanoparticle were investigated. Also, possible chemical interactions between PA6 and/or TPE and MoEpPOSS nanoparticle were determined via Fourier transform infrared spectroscopy (FTIR) analyses.
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    Miscibility and phase behavior of reactively compatibilized poly(lactic acid)/poly(butylene succinate) bio-blends using various rheological analyses
    (Wiley, 2023) Ullah, Muhammad Saeed; Yildirim, Rumeysa; Caraseva, Lulia; Zuza, Ester; Ozkoc, Guralp; Kodal, Mehmet
    This study focuses on the compatibilization of PLA/poly(butylene succinate) (PBS) blends using mono- and multi-epoxide POSS (MoEpPOSS and MuEpPOSS) nanoparticles, from a rheological point of view for the first time in the literature. The addition of PBS to PLA decreased the complex viscosity, storage modulus, and loss modulus, indicating weak interactions between polymers. However, the incorporation of MoEpPOSS and MuEpPOSS increased the complex viscosity and storage modulus due to the formation of long polymeric chains or complex polymeric structures through interactions between the epoxide groups of POSS and the end groups of the polymers. The effect was more significant with MuEpPOSS because MuEpPOSS has multiple epoxide groups in its cage structure, leading to stronger interactions with the polymers. POSS incorporation resulted in semicircular and arc-shaped curves in the Cole-Cole plots, indicating better dispersion, phase homogeneity, and compatibility. The introduction of POSS also influenced the dynamic loss tangent (tan d) versus frequency (?) plot. When POSS was introduced, the tan d peak decreased and shifted to a higher frequency, indicating improved compatibility, and enhanced interfacial adhesion. These findings indicated that the addition of epoxy-POSS nanoparticles can effectively compatibilize PLA/PBS blends and enhance their rheological properties, potentially improving their overall performance for various applications.
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    Preparation and characterization of poly(lactic acid)-based contact-active antimicrobial surfaces
    (Springer, 2023) Aynali, Figen; Doganci, Erdinc; Balci, Huseyin; Cetin, Metin; Ozkoc, Guralp; Sadikoglu, Hasan
    Poly(lactic acid) (PLA)-based contact-active antimicrobial surfaces were successfully fabricated via the spray coating method. For this purpose, firstly two separate antimicrobial polymers were synthesized by introducing alkyne functionalized quaternary ammonium salt into clickable copolymer containing 30 mol% and 5 mol% of quaternary ammonium salt on their backbones. Then, these synthesized polymers were applied to coat one surface of the neat PLA films (PLA/PEG, 90/10) at the rate of 5, 15, and 25 times, respectively. Afterward, the biocidal effect of these films was considered against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria by the way of contact-active method. It was observed that the films coated with polymer containing 30 mol% of quaternary ammonium salt (QAS), even at the lowest coating amount, showed a considerably active antimicrobial property against both bacteria. The thermal, mechanical, and barrier properties of coated films were also investigated. In addition, a cytotoxicity test was performed, and it was found that the PLA film was nontoxic when it was coated with polymer containing 5 mol% of quaternary ammonium salt, even at a high coating amount. For a polymer containing 30 mol% of quaternary ammonium salt on its backbone, it was necessary to coat the films at a low rate for acceptable cytotoxicity. In conclusion, due to the contact-active behavior of covalently attached antimicrobial agents, high antibacterial activity, suitable mechanical properties, and acceptable cytocompatibility, these antimicrobial surfaces can be considered as a potential candidate for bio-based materials.
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    Processing and Characterization of UV Irradiated HDPE/POSS Fibers
    (Mdpi, 2023) Bicer, Ezgi; Kodal, Mehmet; Ozkoc, Guralp
    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.
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    Shape Memory Behavior and Physical Properties of Peroxide X -Linked LLDPE-C6/POSS and LLDPE-C8/POSS Composites
    (Amer Inst Physics, 2023) Bicer, Ezgi; Demir, Gulsen Kurt; Kodal, Mehmet; Ozkoc, Guralp
    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.