Celia Katharina Falkenreck, Jan-Christoph Zarges, Hans-Peter Heim
The effects of hygrothermal aging on the crystallinity, molecular structure and viscosity as well as on the quasi-static behavior of regenerated cellulose fiber-reinforced (RCF) bio-based polyamide (PA) 5.10 were examined in this study. Composites with 20 wt% RCF were produced on a twin-screw extruder and non- and RCF-reinforced specimens were manufactured on an injection molding machine. Specimens were aged in a climate chamber under conditions of four temperatures (23 °C, 50 °C, 70 °C, 90 °C) and five relative humidities (10 %rH, 25 %rH, 50 %rH, 75 %rH, 90 %rH). Once hygrothermal aging was carried out, tensile tests, μCT images as well as DSC, FTIR, GPC, moisture and rheology measurements have been performed on aged specimens and compared with results obtained from non-aged specimens. In addition, the influences of temperature and relative humidity were investigated using a 2nd-degree polynomial regression. Strong hydrolytic and thermo-oxidative influences were detected in combination with elevated temperatures, which accelerate the degradation of the PA5.10. Furthermore, a strong association between aging and moisture content was demonstrated, which corresponds with the resulting mechanical properties. An influence of the inhomogeneous saturation of the PA5.10 on the molecular chain splitting processes could also be shown. The RCF have a positive effect on the durability of PA5.10. However, fiber-matrix-debonding due to swelling processes of the RCF, which have been detected in μCT images, reduce the tensile strength and young's modulus significantly.
Modulating the β-crystalline phase and adding elastomers have traditionally been used to overcome the brittleness of polypropylene (PP); however, the synergistic mechanisms of these components in enhancing low temperatures toughness remain insufficiently explored. A β-nucleating agent (TMB-5) was incorporated into the polypropylene/ethylene–propylene rubber (PP/EPR) system to address the challenges of enhancing low-temperature toughness. Under an extreme low-temperature condition of −40 °C, the PP/EPR/TMB-5 blends exhibit a remarkable enhancement in low-temperature toughness compared with PP/EPR blends, showing a 138 % increase to reach 38.3 kJ/m2. In addition, these blends demonstrate an 8.47 % increase in tensile strength at room temperature. The addition of TMB-5 provides numerous nucleation sites that facilitate the β-crystallization of polypropylene, leading to an increased content of β-crystals and a reduction in crystal grain size. Broadband dielectric relaxation spectroscopy shows that the constrained relaxation of EPR near the crystals shifts to higher temperatures with the formation of β-crystals. The lamellar structure of the β-crystals prevents the aggregation of EPR rubber domains during cooling process, resulting in reduced rubber particle spacing. Observations of remarkable shear deformation and extensive stress-whitening areas on the fracture surfaces of PP/EPR/TMB-5 blends upon impact at −40 °C, as opposed to PP/EPR blends, underpin that the lamellar structure of β-crystals within the composite material efficiently transmits stress further away, facilitating the involvement of more EPR particles in energy dissipation. This finding enables an in-depth investigation into the synergistic toughening mechanism and provides new insights into blends design with conventional rubber for extreme conditions.
In-Tae Hwang, Eunchong Shin, Joon-Yong Sohn
et al.
Herein, we newly developed an eco-friendly and efficient strategy for antibacterial modification of PLA fabrics that facilitates manufacturing processing in an all-aqueous solution and ensures antibacterial activity without significant deterioration of the mechanical strength. The PLA fabrics were efficiently modified with covalent bonding through electron beam (EB)-induced aqueous graft polymerization of acrylic acid (AA) in the presence of a poly(ethylene glycol) diacrylate (PEGDA) crosslinker and then complexed with antibacterial copper (Cu) ions (PLA-g-cPAA-Cu). The addition of the PEGDA crosslinker (0.6 wt%) to the graft polymerization led to a nearly twofold increase in the grafting degree from 50 to 91 % in the water solvent in comparison to in the absence of PEGDA. The resulting grafted fabric also showed minimal deterioration of mechanical strength. It was further found that the hydrophilic PEGDA-crosslinked PAA-Cu complexes were incorporated mainly onto the surfaces of the fiber constituents, preserving the porous structure of the PLA fabric. The prepared PLA-g-cPAA-Cu fabrics with a grafting degree of above 20 % showed excellent contact-killing ability of 99.9 % for Gram-negative E. coli and Gram-positive S. aureus within 3 h and cell viability of above 90 % in a WST-1 cytotoxicity assay using a skin cell line, HaCaT. Moreover, the PLA-g-cPAA-Cu fabric with a grafting degree of 20 % was more than 90 % enzymatically degraded after 90 days. The obtained results unequivocally demonstrate that this EB-based functionalization strategy is not only environmentally friendly and efficient, but also yields PLA-based PPEs with exceptional antibacterial activity, good biodegradability, and suitable mechanical strength.
Mads Nibe Larsen, Anders Løchte Jørgensen, Victor Petrunin
et al.
Identification of black plastics poses a significant challenge in recycling due to the absorptive nature of carbon black additives. This work introduces a method where hyperspectral imaging in the long-wave infrared regime is used to distinguish between twelve samples of commercially available black plastics encompassing nine distinct polymer types. The spectral scanner comprises a scanning Fabry-Pérot interferometer and a thermal camera based on an uncooled microbolometer detector sensitive to wavelengths from 8 μm to 15 μm. A principal component model is combined with k-nearest neighbors to differentiate between plastic samples in hyperspectral images. The model successfully classifies five (PET, POM, PMMA, PA6, and PA66) out of nine black polymers, and the overall accuracy of the model is A=73.1 %.
The study suggests that GB-CNT/PA6 multiscale hybrid composite can be used to create a network structure with controllable electrical conductivity, making it a promising material for various practical applications. The paper introduces a new method for controlling electrical conductivity of composite materials by creating a segregated network morphology (SNM) using a glass bubble (GB)-carbon nanotube (CNT)/polyamide 6 (PA6) multiscale hybrid composite. Instead of relying solely on CNTs, the addition of GB allows for a more economical process by reducing the required CNT concentration to achieve the desired electrical conductivity. The paper also analyzes the effects of varying GB and CNT content on electrical conductivity based on percolation theory. The results demonstrate an 18.8 times increase in electrical conductivity with the SNM approach. The study proposes that this approach could be used to create composite materials with controllable electrical conductivity, making them suitable for various applications.
Sudheer D. Kulkarni, B. Manjunatha, U. Chandrasekhar
et al.
A seal is a mechanism or a piece of material that securely shuts a hole so that air, liquid, or other substances cannot enter or exit the system. Seals are an essential component of practically all machinery and engines and have several applications in industry. The development of novel materials for sealing applications is essentially required on these days. In this research, an attempt is made to find the polymer material for the said application. Poly vinyl rubber material has been taken, and the specimens are prepared for testing the tensile properties and hardness. The specimens were prepared by using die with various temperatures and curing time. Sixteen specimens were prepared by changing the curing temperature, curing time, postcuring temperature, and postcuring time. The curing temperature 150°C and 170°C, postcuring temperature 100°C and 50°C, curing time 14 mins and 18 mins, postcuring time 120 mins and 60 mins, and the pressure of 150 kg/cm2 for all the specimens were maintained. The tensile strength and hardness analysis were done as per the ASTM standard, and it was found that the specimen prepared on 150°C curing temperature, 18 min curing time, 50°C postcuring temperature, and 120 min postcuring time provides the higher tensile strength. DOE analysis is also done to determine the best values of the factors impacting the mechanical characteristics of the seal material. Simple regression analysis is used to find the influence of curing temperature and curing time on the tensile strength and hardness for every 1°C temperature rise and 1 sec curing time.
The compression packer is an important downhole oil production tool, and its failure is mainly attributed to the degradation of its embedded rubber cylinders under the action of high temperatures. In the present study we have made a comprehensive investigation on the mechanical response of the sealing packer based on two rubber materials at high temperatures. Firstly, by measuring the material parameters under different temperatures, we established the constitutive relationships of the two rubber materials (Aflas and Kalrez) in consideration of the temperature effect, in the light of the Mooney-Rivlin model. Next, the sealing performances of two optimized packers were analyzed including Aflas and Kalrez rubber cylinders. The effects of high temperature and the initial setting pressure on the sealing effects of these two optimized packers were probed based on the finite element analysis (FEA), and the ranges of temperature and initial setting pressure for best sealing were determined. This study can provide some ideas for the material selection and structural optimization for sealing packers, aiming to ensure the safe operation of the packers in severe environments.
To achieve efficient heat dissipation using polymer composites, it is important to optimize the heat conduction pathway. Therefore, manipulating the orientation of thermally conductive and anisotropic fillers in composites represents a judicious strategy. So far, external fields have been applied to align fillers within the matrix. However, these processes are energy-intensive and require stimuli-responsive fillers through surface modification, further complicating the process and deteriorating filler thermal conductivity. Herein, to these ends, a facile method for manufacturing composite with an orientation-controlled model anisotropic filler, hexagonal boron nitride (h-BN), was proposed by harnessing thermophoresis. Thermophoresis causes movement and/or rotation of solid particles in a fluid with a steady temperature gradient. A suspension of UV-curable monomer with well-dispersed h-BN was subjected to a temperature gradient, inducing filler rotation via thermophoresis. A subsequent photo-curing yielded a solid composite with the frozen h-BN aligned in a direction agreed with expected for thermophoresis, as indicated by the anisotropic thermal conductivity measurement and cross-sectional scanning electron microscopy (SEM) observation. Additionally, the theoretically estimated Peclet number, induced by thermophoresis, was higher than the experimentally determined value required to align suspended h-BN. To our best knowledge, the current study is the first experimental demonstration of controlling anisotropic filler orientation using thermophoresis.
The ultimate aim of tissue engineering entails fabrication of functional replacements for damaged organs or tissues. Scaffolds facilitate the proliferation of cells, while also improving their various functions. Scaffolds are 3-D structures capable of imitating mechanical and bioactive behaviors of tissues extracellular matrix, which provides enabling environment for cellular bonding, proliferation, and distinction. Hence, scaffolds are often applied in tissue engineering with the aim of facilitating damaged tissue regeneration which is a very important aspect of bone repair. Polymers are broadly utilized in tissue engineering due to their inherent versatility. However, polymers cannot attain mechanical behavior comparable to the bone. Thus, polymer nanocomposites fabricated through inclusion of fibers/or uniformly distributed ceramic/metallic nanoparticles in the matrix are potential materials for bone scaffold fabrication because inclusion of fiber or nanoparticles enhances composites mechanical behavior, while also improving other properties. Hence, this article elucidates recent trailblazing studies in polymer fiber composites and nanocomposites applied in the medical field especially in tissue engineering and bone regeneration. Also insights into market prospects and forecasts are presented.
The present manuscript describes the synthesis of urethane (ROGAU) coating material from Rapeseed oil (RO), Gallic acid (GA) and Toluylene-2,4-diisocyanate [TDI], for the first time. The reaction was accomplished in the following steps: (i) amidation of RO, producing diol fatty amide, HERA, followed by (ii) gallation reaction of HERA with GA, resulting in RO-based gallate amide (ROGA). The structural elucidation by FTIR and NMR confirmed the insertion of amide and ester moieties in the ROGA backbone. To add applicational value to ROGA, it was then derivatized by urethanation reaction with TDI to develop ambient temperature-cured ROGAU, as a corrosion protective coating material. ROGAU coatings were scratch resistant, well-adherent, and flexible to a considerable extent and showed good corrosion resistance performance toward saline medium (3.5 wt% NaCl). ROGAU coatings can be safely used up to 200°C.
Over last few years, polyurethane (PU) has been applied in a number of areas because of its remarkable features, such as excellent mechanical strength, good abrasion resistance, toughness, low temperature flexibility, etc. More specifically, PU can be easily “tailor made” to meet specific demands. This structure–property relationship endows great potential for use in wider applications. With the improvement of living standards, ordinary polyurethane products cannot meet people’s growing needs for comfort, quality, and novelty. This has recently drawn enormous commercial and academic attention to the development of functional polyurethane. Among the major applications, PU is one of the prominent retanning agents and coating materials in leather manufacturing. This review gives a summary of academic study in the field of functional PU as well as its recent application in leather manufacture.
Rattanaporn Wongkumchai, Lunjakorn Amornkitbamrung, Phattarin Mora
et al.
Abstract Ultrafine fully vulcanized powdered natural rubber (UFPNR) is a renewable material that is promising for industrial application as a toughening filler in polymer matrix. In this work, effects of coagent on properties of UFPNR produced by radiation vulcanization and spray‐drying was systematically investigated, in which trimethylol propane trimethaacrylate (TMPTMA) was used as coagent. The crosslinking density of UFPNR could be enhanced by increasing radiation dose from 50 to 350 kGy and it was further enhanced by using TMPTMA as coagent during the production process. UFPNR with the smallest particle size of 3.9 ± 1.8 μm and highest thermal stability (Td5 = 347°C) could be obtained by using TMPTMA with the highest content of 9 phr. The results suggested that polymer chains of natural rubber were more packed into smaller particle as they were more crosslinked by the coagent. Finally, an application of UFPNR as a toughening filler in polybenzoxazine was demonstrated. The highest impact strength improvement of 20% was achieved by incorporation of 3 phr UFPNR in polybenzoxazine.
With the application of bioresorbable materials in self-expandable braided stent, current analytical model for radial compression property of the stent is not applicative if considering the constraint between the polymeric filaments. Poly (l-lactic acid) (PLLA) is one of the broadly used bioresorbable materials in stents due to its superior biocompatibility and mechanical properties. The radial compression properties of PLLA braided stents were investigated by considering two types of constraints between filaments in this work. Weak constraint indicates the friction between filaments of PLLA stents and strong constraint indicates the close looped end (extremity configuration) of PLLA stents. It is found that the radial stiffness can be enhanced by two types of constraints, and strong constraint improves the peak compression force slightly in the radial compression behavior of PLLA braided stents. This work provides suggestions for the study of PLLA braided stents theoretical development.
Abstract Consumption of As(III) in drinking water is a severe problem, and more than 180 million people are suffering worldwide. Therefore, developing an affordable technique to remove As(III) from drinking water is essential to protect human health. In this work, we report chitosan‐iron oxide‐graphene oxide composite beads (GO‐BDs) for the removal of As(III) from the drinking water. The incorporation of chitosan and graphene oxide (GO) provides better physical strength and stability to the GO‐BDs. Prepared GO‐BDs were characterized using different characterization techniques. X‐Ray diffraction (XRD) spectra show the iron oxide nanoparticles were successfully linked with graphene oxide. The size of the beads confirmed by scanning electron microscopy (SEM) and found to be ~1 mm. Elemental mapping of beads show the uniform dispersion of GO/iron oxide on the surface of the beads. The adsorption of As(III) occurs rapidly and attain equilibrium condition in <6 h after removing As(III) from the water within the permissible limit. Effect of water pH, time, temperature, adsorbent dosage, and concentration of the dose have been studied in detail for arsenic removal. Coexisting ions show negligible influence on As(III) removal. Langmuir and Freundlich isotherms were also examined. This study provides the application of GO‐BDs for As(III) removal from contaminated drinking water.
Fibre-reinforced polymers (FRP) have attracted much interest within many industrial fields where the use of 3D printed molds can provide significant cost and time savings in the production of composite tooling. Within this paper, a novel method for the manufacture of complex-shaped FRP parts has been proposed. This paper features a new design of bike saddle, which was manufactured through the use of molds created by fused deposition modeling (FDM), of which two 3D printable materials were selected, polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), and these molds were then chemically and thermally treated. The novel bike saddles were fabricated using carbon fiber-reinforced polymer (CFRP), by vacuum bag technology and oven curing, utilizing additive manufactured (AM) molds. Following manufacture the molded parts were subjected to a quality inspection, using non-contact three-dimensional (3D) scanning techniques, where the results were then statistically analyzed. The statistically analyzed results state that the main deviations between the CAD model and the manufactured CFRP parts were within the range of ±1 mm. Additionally, the weight of the upper part of the saddles was found to be 42 grams. The novel method is primarily intended to be used for customized products using CFRPs.
Hypothesis: Using glass fiber in acrylonitrile-butadiene-styrene (ABS) composites has its limitations by increasing the final price (cost) of the product, abrasions in processing machines, the environmental and health problems during recycling as well as the reduction in impact strength of the composite. This study was carried out to evaluate the effect of silane-treated wollastonite, with a needle structure similar to glass fiber, as an alternative to glass fiber in order to eliminate the drawbacks of ABS/glass fiber composites, on the mechanical properties of ABS/wollastonite composites and compared with ABS/glass fiber composites.Methods: The ABS composites were produced using two types of wollastonite with different geometrical specifications. Dispersion of wollastonite in ABS matrix was evaluated using the SEM micrographs, and the mechanical properties of the composites were determined based on tensile and Izod impact testes. Then, the suitable wollastonite was selected and the ABS/wollastonite composites properties such as tensile, impact strength, thermal and dynamic-mechanical properties were compared with the ABS/glass fiber composites properties at similar percentage of reinforcement phase.Findings: The experimental results showed that the geometrical specification, especially the length/diameter ratio of wollastonite has a significant effect on the impact strength of the ABS composite as a result of good interfacial interaction between the filler and polymer matrix. The results showed significant improvement in the impact strength of ABS/wollastonite composites compared with that of ABS/glass fibers, while the modulus and strength as well as the Vicat softening temperature were acceptable compared with those of ABS/glass fibers composites. According to the results, ABS/wollastonite composites can be a good alternative to ABS/glass fiber composites in many applications.
Four-needle zinc oxide whisker (T-ZnOw) incorporated into microcrystalline cellulose/maleic anhydride grafted polypropylene/random copolymer polypropylene (MCC/PP-g-MA/rPP) composite was prepared by melt blending. 5 wt% PP-g-MA was used as a coupling agent to improve the interfacial compatibility between fillers and rPP. The effect of T-ZnOw on MCC/PP-g-MA/rPP composite was investigated by mechanical testing, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Addition of T-ZnOw enhanced the mechanical properties of composites with tensile and flexural strengths increasing by 10% and 6%, respectively. SEM studies showed an improvement in the compatibility of fracture surfaces, which was evident from the absence of gaps between fillers and rPP. Additionally, initial thermal decomposition temperature and maximum weight loss temperature of T-ZnOw/MCC/PP-g-MA/rPP composite were both higher than those of MCC/PP-g-MA/rPP composite. Thermal degradation kinetics suggested that T-ZnOw has a weak catalytic effect on MCC, resulting in the early degradation of MCC and adhesion to the surface of rPP. Because of the presence of inorganic whiskers, the remaining weight percent was more than that of other composites at the end of the reaction. Crystallization temperature of the T-ZnOw/MCC/PP-g-MA/rPP composite was almost 3~5°C higher than that of MCC/PP-g-MA/rPP composite and close to the crystallization temperature of pure rPP.
Side-chain liquid crystalline polythiophenes were synthesised and the effects of the mesogenic units on the structure and electronic properties of the polymers were studied. The liquid crystal properties of the polymer films were studied using polarised hot-stage optical microscopy and differential scanning calorimetry, and X-ray diffractometry was used to investigate the effect of a magnetic field on the monomers and polymers.
Mojtaba Bozorg, Mahdi Abdollahi, Mohammad Ali Semsarzadeh
The presence of molecular iodine was studied in relation the molecular weight and molecular weight distribution of polystyrene, produced by radical poly merization. Radical polymerization of styrene initiated by 2,2׳-azobisisobutyronitrile (AIBN) was performed at 70°C in the presence of molecular iodine. The synthesized polymers were characterized by gel permeation chromatography (GPC) and proton- nuclear magnetic resonance (1H NMR) techniques. The results of these reactions including conversion data, number-average molecular weight and molecular weight distribution were compared with those obtained for styrene radical polymerization initiated by AIBN at the same temperature in the absence of molecular iodine. It was found that the presence of iodine had a profound effect on the molecular weight and its distribution in the produced polystyrene. This was attributed to the ability of iodine to control the polymerization of styrene initiated by AIBN via reverse iodine transfer polymerization (RITP) mechanism. The polymer produced by this method had a molecular weight of 10600 g/mol with a molecular weight polydispersity index of 1.3. Due to the importance of induction period in reverse iodine transfer radical polymerization, increasing the temperature to 120°C during the induction period resulted in shorter induction periods and the produced species led to better control of the molecular weight. Also, due to the role of iodine molecules as a radical inhibitor, the presence of a secondary radical inhibitor, i.e. 4-tert-butylcatechol, along with the iodine was investigated in radical polymerization of polystyrene initiated by AIBN. It was observed that the secondary radical inhibitor prevented the consumption of the iodine molecules by the radicals produced from decomposition of the AIBN initiator; therefore, alkyl halides were not produced during the induction period.