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Öğe 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, MehmetVarious 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.imageÖğe Effects of ov-poss nanoparticles on the vulcanization kinetics of natural rubber compounds(INST ZA KOVINSKE MATERIALE I IN TEHNOLOGIE, 2021) Uçtepe, Ebru; Yazıcı, Nazlı; Kodal, Mehmet; Karaağaç, Bağdagül; Özkoç, GüralpPolyhedral oligomeric silsesquioxanes (POSSs) are new-generation additives, which can provide improved properties of polymer matrices due to physical and/or chemical interactions between the polymer molecules and their reactive sites. In the case of rubber-based polymeric systems, POSSs are also able to accompany a vulcanization reaction. This study aimed to investigate the effect of octavinyl functionalized POSS (OV-POSS) on the sulphur vulcanization of a model natural rubber (NR) based compound. The reaction kinetics was studied using various kinetic approaches based on moving die rheometry and differential scanning calorimetry. Rheometric data was evaluated using a common non-linear cure kinetic model, called the Isayev and Deng Model. The Kissinger, Flynn-Wall-Ozawa and Crane Models were used to evaluate the thermal data for curing reactions. All the models were found to be able to analyze the vulcanization kinetics of OV-POSS containing NR-based rubber compounds as well as the effect of the OV-POSS incorporation.Öğe 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, GuralpThe 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.Öğe Improving bonding strength of injection overmolded composites(John Wiley and Sons Inc, 2022) Akpınar, Serkan; Metin, Merve; Koçoğlu, Hürol; Kodal, Mehmet; Sezen, Meltem; Özkoç, Güralp; Altan, M. CengizThe overmolding of short fiber reinforced polymer compounds onto continuous fiber reinforced composite substrates provides design flexibility and the ability to tailor stiffness, strength, and damage tolerance for structural applications. In this work, a novel molding approach that enhances the bonding strength by mechanical interlocking is presented. The effectiveness of the proposed approach was validated by characterization of the bonding strength between a short glass fiber PP (SGFPP) composite overmolded onto a continuous glass fiber reinforced PP (CGFRPP) prepreg. Enhancement of the bonding strength was achieved by judiciously drilling tapered holes on the CGFRPP substrate before molding, which facilitated better interlocking with the injection molded SGFPP composite. The overmolding of preheated composites with tapered holes yielded up to 60% improvement in bonding strength. In general, having multiple holes helped improve bonding up to certain hole diameter. Similarly, preheating of the substrate over a short time improved the interfacial adhesion, while extended preheating resulted in a reduction of bonding quality. SEM analysis of the fracture surfaces after the tensile debonding test revealed that the SGFPP filled the holes on the substrate during overmolding. © 2022 Society of Plastics Engineers.Öğe Lab-scale twin-screw micro-compounders as a new rubber-mixing tool: ‘a comparison on EPDM/carbon black and EPDM/silica composites’(MDPI, 2021) Yazıcı, Nazlı; Kodal, Mehmet; Özkoç, GüralpThe research and development (R&D) in rubber formulation development require reproducible, repeatable, fast, accurate, and efficient sample preparation. The lab-scale formulation development is conventionally carried out using small-scale internal mixers and two-roll mills. However, high torque laboratory twin-screw micro-compounder, which have been serving the plastic industry for more than 30 years, can be used to formulate new rubber compounds for fast and accurate sample preparation that on top can contribute to the economics of R&D. In this study, we investigated the possibility of using lab-scale 15 mL high torque twin-screw micro-compounder as a tool for new rubber compound development. For this purpose, we formulated EPDM/carbon black and EPDM/silica recipes through conventional way using a Banbury mixer followed by a two-roll mill, and through the possible way using a lab-scale 15 mL twin-screw micro-compounder. We crosslinked both systems via hot press at a predefined temperature and time. The rheological and mechanical properties of the compounds were investigated. Moreover, the dispersion of carbon black and silica in the EPDM matrix was judged by DisperGrader and scanning electron microscope (SEM). The conventional way of sample preparation was compared with a possible sample preparation method based on materials’ parameters and ease of operation.Öğe 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, MehmetThis 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.Öğe A new approach for the reuse of scrap carbon fiber in high-added value continuous fiber reinforced composite structures(Elsevier Ltd, 2022) Koçoğlu, Hürol; Kodal, Mehmet; Altan, M. Cengiz; Özçelik, Babür; Özkoç, GüralpThis study proposes an innovative processing approach for high-added value hybrid fiber-reinforced composite structures by reusing scrap carbon fiber (CF). Thermoplastic prepregs were produced via wet-laid method using chopped polyamide 6.6 fibers as matrix and short scrap CFs as the reinforcing phase. These prepregs were then hot stacked with woven glass fabrics, forming a novel hybrid lightweight composite laminate. Silane treatment was used to improve the adhesion of glass fabric to the novel wet-laid scrap CF/PA6.6 prepregs. Tensile, flexural, dynamic-mechanical, and morphological properties of the composites were examined to characterize the effectiveness of the hybridization of short scrap CFs and glass fabric. The results showed that short scrap CF in the laminates increased the tensile strength up to 30 % and flexural strength up to 60 %. Moreover, silane surface modification of the glass fabric yielded a 140 % improvement in the flexural strength of scrap CF/PA6.6 prepreg-glass fabric hybrid laminates.Öğe Novel and eco-friendly hydrophobic treatment of cotton and polyester fabrics based-on octavinyl and aminopropylisobutyl polyhedral oligomeric(Elsevier Sci Ltd, 2023) Akbasak, Tughan; Kodal, Mehmet; Mert, Olcay; Ozkoc, GueralpThe hydrophobicity of cotton and polyester fabrics plays a significant role in various industrial applications. Anchoring hydrophobic chemicals onto the fabric surface is one of the major strategies. Fluorinated chemicals are widely employed to construct hydrophobic surfaces. However, alternative hydrophobic coatings are urgently sought by researchers due to the potential risks and hazards of fluorinated chemicals. Polyhedral oligomeric silsesquioxanes (POSS) are one of the most potential alternatives as they increase the roughness and lower the surface energy through chemical enhancement of the surface. In this work, hydrophobic cotton and polyester surfaces were fabricated anchoring Octavinyl POSS (OL-POSS) and Aminopropylisobutyl POSS (AM-POSS) onto the surface via one-step dip-coating technique. To enhance the surface roughness and the hydrophobicity, Ul-traviolet (UV) radiation was employed with Benzoyl Peroxide (BPO) initiator. Water contact angle (WCA) of both fabrics increased from 0 degrees to 136 degrees using 5% POSS coatings with initiator and UV present. Water absorption duration (WAD) also increased from several seconds up to 310 min. Furthermore, 5% POSS modified fabrics gave similar or better WAD values when compared to coatings treated with fluorinated chemicals. The findings confirmed that OL-POSS and AM-POSS coatings are eligible environmentally friendly candidates for the replacement of fluorinated chemicals.Öğe A novel practical approach for monitoring the crosslink density of an ethylene propylene diene monomer compound: Complementary scanning acoustic microscopy and FIB-SEM-EDS analyses(SAGE, 2022) Yazıcı, Nazlı; Opar, Ekin; Kodal, Mehmet; Tanören, Bükem; Sezen, Meltem; Özkoç, GüralpTuning of the crosslink density (CLD) in the rubber compounds is very crucial for optimizing the physical and mechanical properties of the ultimate rubber products. Conventionally, CLD can be measured via rheological methods such as moving die rheometer (MDR), via mechanical tests such as temperature scanning stress relaxation analysis (TSSR), or via direct swelling experiments using Flory–Rehner approach. In the current study, two novel techniques, focused ion beam - scanning electron microscopy (FIB-SEM) processing, with simultaneous energy dispersive X-ray spectrometry (EDS) mapping analysis and scanning acoustic microscopy (SAM) were combined and correlated to conventional methods on a model recipe of ethylene propylene diene monomer (EPDM) compound having different sulphur contents. Depending on the applied technique, the increase in the crosslink density with sulphur content was found to be 1.7 fold for the Flory–Rehner approach and 1.2 fold for both TSSR and MDR. It is directly monitored from the FIB-SEM-EDS analysis that the sulphur distribution and agglomeration behavior increased in line with ZnO content, which is an indirect indication of the rise in crosslink density. The impedance maps of the crosslinked samples obtained through SAM analysis revealed that the impedance of the samples increased with the increasing sulphur content, which can be attributed to higher level of crosslink density. A quantified correlation was obtained between SAM images and the crosslink density of the samples. It was shown that SAM is a promising tool for practical and non-destructive analysis for determining the formation of crosslink density of the rubbers. © The Author(s) 2022.Öğe Processing and Characterization of UV Irradiated HDPE/POSS Fibers(Mdpi, 2023) Bicer, Ezgi; Kodal, Mehmet; Ozkoc, GuralpHigh-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.Öğe Reactive compatibilization of PLA/PBS bio-blends via a new generation of hybrid nanoparticles(John Wiley and Sons Ltd, 2022) Ullah, Muhammad Saeed; Yıldırım, Rümeysa; Kodal, Mehmet; Özkoç, GüralpPoly(butylene succinate) (PBS) is a worthy biodegradable thermoplastic polyester for blending along with other biopolymers, especially with poly (lactic acid) (PLA), to overcome its inadequacies in mechanical and thermal characteristics. Since binary blends of PLA and PBS showed that they are incompatible, compatibilization is required. In this work, multi-epoxide polyhedral oligomeric silsesquioxane (Glycidyl POSS) was added to PLA and PBS using the melt blending method to make them compatible. The blends were prepared at different weight ratios having different amounts of compatibilizer. SEM analysis showed that the Glycidyl POSS impacted the interfacial adhesion and other properties of PLA and PBS blends. Noticeable improvements in mechanical properties were revealed by tensile and impact test results. Tensile strength and Young's modulus were improved when epoxy-POSS was added up to 1 and 3 wt% into ternary blends, but further increasing POSS concentrations resulted in lower values. FTIR analysis showed a strong interaction between the epoxide group of POSS and the end groups of PBS or PLA. The thermal properties of samples were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The shifts in glass transition temperatures of the PLA phase towards lower values appeared in DSC, confirming the enhanced compatibility of PLA and PBS. Also, the reinforcing ability of the POSS inorganic core structure impacted the thermal stability of the blends.Öğe A review on polyhedral oligomeric silsesquioxanes as a new multipurpose nanohybrid additive for poly(lactic acid) and poly(lactic acid) hybrid composites(WILEY, 2022) Ullah, Muhammad Saeed; Yazıcı, Nazlı; Wis, Abdulmounem Alchekh; Özkoç, Güralp; Kodal, MehmetAbstract The production of petroleum-based polymers in huge amounts is perilous for our ecosystem and oil reserves. The use of biodegradable polymers instead of synthetic polymers for various commodity, engineering, and biomedical applications remains the overriding concern of the researchers in last decades. Although poly(lactic acid) (PLA) is considered to be the most befitting substitute for conventional petroleum-based products because of its superlative mechanical properties, material & processing cost, and non-toxicity, they have some consequential limitations for various applications because of their slow rate of crystallization, low thermal stability, high brittleness, and low toughness. To overwhelm these deficiencies during the last two decades, researchers have developed various techniques to tailor the properties of PLA, that is, blending with other polymers or using additives such as nanofillers. Among all the nanofillers, for example, carbon nanotubes and organoclays, polyhedral oligomeric silsesquioxanes (POSS) was found the most promising nanofiller because of its organic and inorganic nanostructure and fine dispersion into PLA matrix. This article reviews all the investigations relevant to POSS incorporation into PLA or blends of PLA with other polymers to compare the mechanical, morphological, and physical properties of the ameliorated composites and the neat PLA.Öğe 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, GuralpThis 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.Öğe Solid particle erosion and scratch behavior of novel scrap carbon fiber/glass fabric/polyamide 6.6 hybrid composites(Wiley, 2023) Kocoglu, Hurol; Korkusuz, Orkan Baran; Ozzaim, Pelin; Kodal, Mehmet; Altan, M. Cengiz; Sinmazcelik, Tamer; Ozcelik, BaburThis study investigated the tribological performance of hybrid composites composed of scrap carbon fiber (CF), glass fabric (GF), and polyamide 6.6 (PA6.6) through an innovative approach for reusing scrap CFs in high-value composite structures. The experimental setup included CF/GF/PA6.6 hybrid composite laminates with varying CF contents and surface-modified GFs, as well as PA6.6 sheets and GF/PA6.6 composite laminates. Solid particle erosion and scratch tests were conducted to assess the influence of scrap CF hybridization and GF surface modification on the tribological properties of the composites. The results demonstrated that neat PA6.6 sheets exhibited the lowest erosion rate, while the incorporation of CF and GF reinforcements had a detrimental effect on erosion resistance. The highest erosion rate was observed within the impact angle range of 15 degrees -30 degrees for pure PA6.6 sheets, whereas for composite laminates, it occurred within the range of 30 degrees-45 degrees. In contrast, CFs positively affected scratch hardness despite their negative impact on erosion resistance. Additionally, the silane treatment of GFs, which enhanced interfacial strength, improved the erosion resistance and scratch hardness of GF/PA6.6 composite laminates without CF. Profilometer-based topographic analysis revealed a correlation between the average surface roughness of the eroded surfaces and the weight loss resulting from solid particle erosion.Öğe Unlocking the Potential Use of Reactive POSS as a Coagent for EPDM/PP-Based TPV(Mdpi, 2023) cakir, Nazli Yazici; Inan, Oezgenur; Ergun, Merve; Kodal, Mehmet; Ozkoc, GueralpThermoplastic vulcanizates (TPVs) are multifunctional materials consisting of two or more phases with solid elastomeric properties at room temperatures and fluid-like properties above their melting point. They are produced through a reactive blending process known as dynamic vulcanization. The most widely produced TPV type is ethylene propylene diene monomer/polypropylene (EPDM/PP), which is the focus of this study. The peroxides are mainly selected to be used in crosslinking of EPDM/PP-based TPV. However, they still have some disadvantages, such as the side reactions resulting in the beta chain scission of the PP phase and undesired disproportionation reactions. To eliminate these disadvantages, coagents are used. In this study, for the first time, the use of vinyl functionalized polyhedral oligomeric silsesquioxane (OV-POSS) nanoparticles was investigated as a potential coagent in EPDM/PP-based TPV production via peroxide-initiated dynamic vulcanization. The properties of the TPVs having POSS were compared with the conventional TPVs containing conventional coagents, such as triallyl cyanurate (TAC). POSS content and EPDM/PP ratio were investigated as the material parameters. Mechanical properties of EPDM/PP TPVs exhibited higher values in the presence of OV-POSS, which resulted from the active participation of OV-POSS into the three-dimensional network structure of EPDM/PP during dynamic vulcanization.
