Thermomechanical Properties Research Articles

Effects of wheat cultivar, bran concentration and endoxylanase on the thermomechanical, viscoelastic and microstructural properties of whole wheat flour dough

Globally, it is challenging to promote the market of whole wheat product due to its undesirable product quality issues. To overcome this remarkable challenge, this research was to work on the constructive strategies for mitigating the negative impact of wheat bran. As such, the objective of this research was to investigate how the wheat cultivar, bran concentration and endoxylanase affected dough thermomechanical properties, viscoelasticity and microstructure by a combined use of mixolab, rheometry, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). A cultivar-dependent discrimination for the bran tolerance was observed to suggest the suitable wheat cultivars for whole wheat manufacturing. Bran addition positively affected dough mechanical and viscoelastic properties, i.e., larger dough mechanical weakening (C2) and gel strength, and it negatively affected starch gelatinization (C3) and retrogradation (C5). However, the main conclusions are below. The endoxylanase was incorporated to invert the bran impact on the above properties of dough. Endoxylanase was also used to develop a better integrity of gluten network, larger coverage of starch granules and even distribution of gas cells. Outcomes from this work will provide a practical guidance for improving the high-fibre product quality and promoting its market growth.

A novel bio-based autocatalytic amide-type phthalonitrile monomer: Synthesis, curing kinetics and thermal properties

A bio-based bisphenol compound (DFA) was prepared using bisphenolic acid and furfurylamine in biomass as raw materials. Then, a bio-based amide phthalonitrile monomer (DFAP) was obtained in an environmentally friendly solvent. Nuclear magnetic resonance and Fourier transform infrared spectroscopy (FT-IR) proved the successful synthesis of DFA and DFAP. The curing behavior and curing kinetics of the polymer were studied using FT-IR and differential scanning calorimetry. Calculate the activation energy using the isoconversion method. The SB(m, n) autocatalytic reaction model describing the curing process of poly(DFAP) was modified and fitted by introducing the variable activation energy model. The thermal stability, thermomechanical properties and processing properties of the resin were studied using technologies such as thermogravimetric analyzer, dynamic mechanical analyzer and rheometer. The results show that the prepolymer has a wide processing window and a low melt viscosity. Poly (DFAP) has a high glass transition temperature and excellent thermal stability.

Oxygen-induced surface hardening and aromatization of thermoset furanic biobased resin: origin and consequences

This article emphasizes the phenomena occurring in furan resins at high temperature, once they are polymerized and before their carbonization. The effects of the atmosphere (N2 and air) during the curing of furan resins were investigated and it is shown that upon exposure to air at temperatures above 175 °C, the furan resins develop an aromatic surface. By means of solid-state NMR and infrared spectroscopy, it is demonstrated that the aromatic groups are mainly located on the material's surface. A mechanism of this surface modification is proposed together with a short kinetic study. In addition, the thermo-mechanical properties are studied. The aromatic surfaces decrease the damping capacity of the material, yet its resistance to degradation is increased. Finally, tensile properties of the furan resins are not affected by the presence of this aromatic surface.

Effect of the alignment of Fe nanoparticles in polyvinyl alcohol film on the morphological, thermomechanical, optical, and magnetic properties

Nanocomposite films of polyvinyl alcohol (PVA) and iron (Fe) magnetic nanoparticles were fabricated by the casting method. Fe nanoparticles were analyzed via a transmission electron microscope (TEM). Two films were fabricated under the same conditions, and one was exposed to a magnetic field (aligned) and another without it (isotropic). The two samples (isotropic & aligned) were studied via a scanning electron microscope (SEM), an optical microscope, and a thermomechanical analysis (TMA). TMA measures the changes in sample dimensions as a function of temperature under a non-oscillatory load with a programmed temperature under constant pressure. The aligned sample exhibits less penetration than pure PVA and isotropic samples. The aligned film exhibits less penetration than isotropic and pure PVA film. Optical properties were carried out using an ultraviolet–visible spectrophotometer. The optical and magnetization properties were investigated for the pure PVA, isotropic, and aligned samples. The bandgap energy decreases after adding Fe to the PVA, and the bandgap for the isotropic sample is lower than that for the aligned one. The magnetizations for the isotropic and aligned samples are 2.75 and 5.05 emu/g, respectively. The exposure of the polymer matrix containing magnetic nanoparticles to the magnetic field helps to change the film structure and makes it promising in medical and optical applications

Exploring synergies between GnP and fiber orientation in enhancing mechanical, thermomechanical, and shape memory properties of carbon fiber polymer composites

Abstract This research investigates the mechanical, thermomechanical, and shape memory properties across 12 configurations of shape memory hybrid composites, varying in carbon fiber orientation: uni-directional (UD), bi-directional-Twill (BDT), and bi-directional-Plain (BDP), and multi-walled carbon nanotube weight percentages of 0.4%, 0.6%, and 0.8% elucidate the synergistic effects of fiber architecture and nanomaterial reinforcement. The fabrication process involves initially preparing GnP-modified epoxy nanocomposites through ultrasonication followed by hand layup techniques to fabricate three-phase shape memory hybrid composites. Optimal tensile performance is observed in GnP-modified UD composites at a 0.6 wt% concentration, achieving a tensile strength of 728.32 MPa and a modulus of 71.29 GPa. Furthermore, enhancements in thermomechanical and shape memory properties are noted in GnP-modified BDT composites and are further improved in GnP-modified BDP composites configurations. These improvements are attributed to enhanced interfacial bonding between the polymer and fiber, with the maximum effect observed at the 0.6 wt% BDP composite, validated by morphological analysis using FESEM. The study demonstrates that despite polymer modification, all configurations maintain high shape recovery ratios, particularly notable at 97.54% for 0.6 wt% GnP modified BDP composite, exceeding 90% across all configurations, indicating robust performance in shape memory capabilities.

Curing kinetics effect on thermo-mechanical properties of an epoxy resin cured by imidazolium-based ionic liquid

Curing kinetics effect on thermo-mechanical properties of an epoxy resin cured by imidazolium-based ionic liquid

Enhancing enset fiber‐reinforced polylactic acid composites through different surface treatments for emerging applications

AbstractEnvironmental concerns and the over‐exploitation of natural resources have driven the search for eco‐friendly materials. Agro/industrial waste, often discarded, can be repurposed as fillers in biocomposites. However, bio‐fibers present challenges such as poor compatibility, high moisture absorption, and variable mechanical properties. This study examines various fiber surface modification techniques, including NaOH, silane, alkali‐silane, and pectinase enzyme treatments on enset fiber (EF) to produce sustainable reinforced poly(lactic acid) (PLA) composites. Untreated EF/PLA composites were fabricated for comparison. Results showed that the applied EF surface treatments, especially using pectinase enzyme, significantly enhanced mechanical, thermal, and thermomechanical properties. Pectinase‐treated EF/PLA composites displayed increased tensile strength by 55.99%, elongation at the break by 39.49%, tensile modulus by 32.59%, impact strength by 51.50%, flexural strength by 51.85%, flexural modulus by 60.90%, and improved thermal stability as compared to untreated composite. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses verified better fiber‐matrix interaction with clarity due to reduced non‐cellulosic components. Pectinase enzyme treatment emerged as the most effective, eco‐friendly method, enhancing the enset fiber's potential in polymer biocomposites, suitable for automotive interiors and packaging industries, reducing synthetic plastic pollution, and utilizing agricultural waste.Highlights Enset fibers were modified by NaOH, silane, NaOH/silane, and pectinase enzyme The modified enset/PLA composites were prepared by compression molding Surface treatments enhanced the enset‐PLA matrix interaction Pectinase‐modified enset/PLA composite showed superior properties Improved properties of enset composites make it ideal for various applications

Investigation of the Effect of Reprocessing on Thermal and Mechanical Properties of Polymers and Polymer Nanocomposites

This study explored the impact of multiple reprocessing cycles on the thermomechanical properties of polystyrene (PS) and low‐density polyethylene (LDPE), simulated through reprocessing with a twin‐screw extruder. Additionally, it compared the thermal and mechanical properties of graphene nanoplatelets (1% w/w) reinforced polypropylene (PP‐GNP) nanocomposites with PP. The materials undergo seven consecutive extrusion cycles at varying screw speeds (100 and 150 rpm) and temperatures (180 and 200 °C). Increasing the screw speed from 100 to 150 rpm raised LDPE's screw torque by about 40% at the first reprocessing cycle. Processing PS at 200 °C reduced screw torque by ≈20% compared to 180 °C at 1–5 reprocessing cycles. Both torque and power decrease for PP and PP‐GNP with each reprocessing cycle. LDPE's tensile modulus decreases with more cycles at 200 °C, while PS shows no consistent variation. PP's tensile modulus and ultimate tensile strength drop by 24% and 12%, respectively, from the first to the fifth cycle, while PP‐GNP exhibits no consistent variation. Differential scanning calorimetry shows no clear change in LDPE's melting point, but an increase in PP and PP‐GNP's melting points up to the fifth cycle. This research provides crucial insights to advance the recycling of polymers reducing environmental impact.

Effect of Thermal Expansion Mismatch on Thermomechanical Behaviour of Compacted Graphite Iron

Compacted graphite iron (CGI) attracts significant attention in the automotive industry thanks to its suitable thermomechanical properties and cost-effectiveness. A primary fracture mechanism at the microscale for CGI involves interfacial damage and debonding between graphite inclusions and its metallic matrix, which can occur under high-temperature service conditions due to a mismatch in the coefficients of thermal expansion between these two phases. Such microscopic interfacial damage can initiate macroscopic fractures in cast-iron components subjected to thermal loading. While this phenomenon was studied in various composites, there remains a lack of detailed information for CGI, especially related to the complex morphology of its graphite inclusions. This study investigates the influence of graphite morphology and type of matrix on the thermomechanical performance of CGI at high temperatures. A set of three-dimensional finite-element models were developed in the form of unit cells with a single graphite inclusion embedded within a cubic domain of the metallic matrix. Elastoplastic behaviour was assumed for both phases in the numerical simulations. The study is focused on the response of the constituents in CGI to pure thermal loading in order to explore the relationship between graphite morphology and fracture mechanisms. The findings aim to enhance understanding of how graphite morphology affects the behaviours of CGI under high-temperature conditions.

The Thermomechanical, Functional and Biocompatibility Properties of a Au–Pt–Ge Alloy for PFM Dental Restorations

A high-noble Au–Pt–Ge porcelain-fused-to-metal (PFM) dental alloy without the known adverse metallic elements and with the addition of germanium (Ge) was produced as a more cost-effective alternative to other precious alloying metals, with investigations for determining the functionality and clinical use of this alloy. The thermomechanical, biocompatibility, durability, workability and economic characteristics of the produced dental alloy were investigated. These properties were investigated with in vitro biocompatibility testing on human gingival fibroblasts (HGFs); static immersion testing for metal ion release; DSC analysis; hardness, tensile testing, density and coefficient of thermal expansion (CTE) measurements; metallographic and SEM/EDX microstructure investigations; and finally with the production of a test PFM dental bridge. The results of the thermomechanical testing showed alloy properties suitable for dental restorations and clinical use, with somewhat lower mechanical properties, making the alloy not suitable for extensive multiunit fixed restorations. The microstructure investigations showed segregations of Ge in the homogeneous alloy matrix, which reduce the alloy’s mechanical properties. The produced PFM dental bridge showed excellent workability of the alloy in a dental laboratory setting, as well as a high standard of the final dental restoration. The ion release was negligible, well below any harmful quantities, while the cell viability examination showed significantly higher viability ratings on polished alloy samples as compared to as-cast samples. The results showed that a dental substructure in direct contact with oral tissue and fluids should be highly polished. The performed investigations showed that the produced PFM dental alloy is suitable for clinical use in producing high-quality dental restorations with high biocompatibility for patients prone to metal allergies.

Thermoplastic Starch with Maltodextrin: Preparation, Morphology, Rheology, and Mechanical Properties

This work describes the preparation of highly homogeneous thermoplastic starches (TPS’s) with the addition of 0, 5, or 10 wt.% of maltodextrin (MD) and 0 or 3 wt.% of TiO2 nanoparticles. The TPS preparation was based on a two-step preparation protocol, which consisted in solution casting (SC) followed by melt mixing (MM). Rheology measurements at the typical starch processing temperature (120 °C) demonstrated that maltodextrin acted as a lubricating agent, which decreased the viscosity of the system. Consequently, the in situ measurement during the MM confirmed that the torque moments and real processing temperatures of all TPS/MD systems decreased in comparison with the pure TPS. The detailed characterization of morphology, thermomechanical properties, and local mechanical properties revealed that the viscosity decrease was accompanied by a slight decrease in the system homogeneity. The changes in the real processing temperatures might be quite moderate (ca 2–3 °C), but maltodextrin is a cheap and easy-to-add modifier, and the milder processing conditions are advantageous for both technical applications (energy savings) and biomedical applications (beneficial for temperature-sensitive additives, such as antibiotics).

Design and Depolymerization of Bis(2‐hydroxyethyl) Terephthalate‐Containing Polyurethanes for Vat Photopolymerization

AbstractVat photopolymerization (VPP) of highly aromatic polyurethanes (PUs) expands the library of additive manufacturing (AM) materials and enables a vast array of ductile thermoplastics, rigid and flexible thermosets, and elastomers. Aromatic diisocyanates and various diols enable printing of rigid, highly aromatic cross‐linked parts, which offer high glass transition temperatures and tunable thermomechanical performance. The judicious control of molecular weight of the photo‐reactive telechelic oligomers allows for a fundamental study of the influence of cross‐link density in highly aromatic 3D PU printed objects. VPP AM produces objects with high resolution, smooth surface finish, and isotropic mechanical properties. Thermal post‐processing is critical in maintaining excellent thermomechanical properties with semi‐crystallinity as a function of cross‐link density. Due to the presence of two ester carbonyls in the bis(2‐hydroxyethyl) terephthalate chain extender, the printed parts are readily amenable to depolymerization with methanolysis to produce difunctional dimethyl dicarbamates under modest reaction conditions. Dimethyl dicarbamates serve as suitable monomers for subsequent polycondensation.

Impact of Graphene Nano particles on static and dynamic mechanical properties of basalt-glass fibre reinforced epoxy polymer hybrid composites

ABSTRACT This paper investigates the structure-property relationships in basalt – glass fabric reinforced hybrid polymer composites doped with graphene nanoplatelets. Basalt Glass fabrics were reinforced with 0.2 wt.% − 0.8 wt.% graphene using hand layup and compression moulding to fabricate laminated plates. The mechanical, morphological, and thermomechanical properties were characterised using tensile, flexural, impact, SEM, FTIR, XRD, and DMA testing. Results showed that low graphene loadings of 0.2 wt.% − 0.4 wt.% led to small, isolated graphene platelets decorating the basalt fibres. At 0.8 wt.% loading, extensive wrinkling, folding, and stacking of graphene sheets on the basalt was observed. FTIR revealed increasing sp2 C=C vibrations and XRD showed rising graphene peak intensities with higher loadings. While tensile and flexural strengths improved up to 0.6 wt.% graphene due to efficient stress transfer, impact energy increased consistently until 0.8 wt.% graphene owing to reinforcement effects. DMA exhibited enhanced storage modulus and restricted mobility with more graphene. An optimum graphene loading of 0.6 wt.% was found to maximise the mechanical performance through uniform dispersion and strong interfacial adhesion. The results demonstrate that graphene incorporation can substantially augment the strength, toughness, and thermomechanical properties of the composites at appropriate compositions prior to aggregation.

Scratch-Induced Wear Behavior of Multi-Component Ultra-High-Temperature Ceramics

Multi-component ultra-high-temperature ceramics (MC-UHTCs) are promising for high-temperature applications due to exceptional thermo-mechanical properties, yet their wear characteristics remain unexplored. Herein, the wear behavior of binary (Ta, Nb)C, ternary (Ta, Nb, Hf)C, and quaternary (Ta, Nb, Hf, Ti)C UHTCs synthesized via spark plasma sintering (SPS) is investigated. Gradual addition of equimolar UHTC components improves the wear resistance of MC-UHTCs, respectively, by ~29% in ternary UHTCs and ~49% in quaternary UHTCs when compared to binary UHTCs. Similarly, the penetration depth decreased from 115.14 mm in binary UHTCs to 73.48 mm in ternary UHTCs and 44.41 mm in quaternary UHTCs. This has been attributed to the complete solid solutioning, near-full densification and higher hardness (~up to 30%) in quaternary UHTCs. Analysis of the worn-out surface suggests pull-out, radial, and edge micro-cracking and delamination as the dominant wear mechanisms in binary and ternary UHTCs. However, grain deformation and minor delamination are the dominant wear mechanisms in quaternary UHTCs. This study underscores the potential of MC-UHTCs for tribological applications where material experiences removal and inelastic deformation under high mechanical loading.

Durable polymer composites preparation with oxy-delignified banana fiber for automotive parts: A study on mechanical and thermal properties

An innovative process route has been developed to produce modified banana fiber that are used as reinforcement in polypropylene composites for automotive parts. Banana fiber (BF) is modified through, Alkaline peroxide (APF), and oxygen delignification (ODF) treatment to obtain better adhesion and enhanced thermo-mechanical properties. The fiber-reinforced polymer (FRP) composites (10–30 % loading), were prepared through a specified configuration in a co-rotating twin screw extruder followed by injection molding. The results show that the ODF treatment with a 15 % NaOH concentration resulted in an 11-kappa number, which was lower than APF and untreated fiber. The highest improvement in tensile (31.27 ± 2.56) and flexural strength (44.880 ± 1.05 MPa) was achieved for ODF polymer composite and were 20.40 % and 35.6 % higher compared to the untreated fiber. The addition of natural fiber decreased the melt flow index to 7.56 gm/10 min with a slight decrease in hydrophilicity. The thermal stability was increased with enhanced melting, crystallization temperatures, and surface morphology.

Impact of statistical poly(propylene co-ethylene) on the thermo-mechanical properties of high-density polyethylene

A series of high-density polyethylene and a statistical copolymer of poly(propylene-co-ethylene) blends in a wide range, namely (0, 10, 20, 30, 40, 50, 60,70, 80, 90, 100) abbreviated as HDPE/VM were systematically investigated by using a rheometer, differential scanning calorimetry (DSC) measurements, polarized optical microscopy (POM) and tensile tests. Rheometer results show that adding VM decreases dynamic viscosity, storage, and loss modulus. Han plot shows that HDPE and VM are compatible and miscible in the range from 20 to 60 VM % in the molten state. DSC results show little nucleation effect of VM on HDPE (HDPE’s melt crystallization temperature shifts 2 °C higher). Moreover, a linear composition dependence of ∆cp ∆Hc, ∆Hm shows that PE and VM are most probably compatible in the molten state in composition range from 20 to 60%. However, upon crystallization, the VM and PE domains occur distinctively. The results of the tensile tests demonstrated a decrease in elastic modulus, yield stress, and ultimate tensile strength as VM content increased. At low VM content (less than 20%), high elongation at break was detected for the blends, and very fine spherulites of HDPE were found across the sample by POM.

Effect of the Compounding Method on the Development of High-Performance Binary and Ternary Blends Based on PPE

The polymer blends are an effective strategy for materials design with new properties in the plastic industry; such features may depend on the blend components and the processing method. This study aimed to understand the effect of styrene-butadiene-styrene (SBS) content and its architecture on blends based on polyphenylene ether (PPE), high-impact polystyrene (HIPS), and SBS. In addition, this research compared and analyzed the blends formulated by different processing methods: twin-screw extrusion (TSE) and internal mixing (IM). Furthermore, three SBS copolymers, two radial and one linear (with different molecular weights), were used to produce PPE/HIPS/SBS blends, analyzing which SBS copolymer feature provides excellent viscoelasticity, thermomechanical properties, and impact resistance. The findings revealed that the melt processing method played a crucial role in Izod impact resistance of the PPE/HIPS/SBS blends, as well as the molecular architecture, molecular weight, and SBS content. The findings also demonstrated that the TSE process is more effective than the IM. Since the PPE/HIPS/SBS blends displayed higher Izod impact resistance than the PPE/HIPS or PPE/SBS binary blends, a synergistic effect of SBS and HIPS is suggested.

Strength Retention of Carbon Fiber/Epoxy Vitrimer Composite Material for Primary Structures: Towards Recyclable and Reusable Carbon Fiber Composites

Recently, the growth of the recyclability of carbon fiber reinforced polymer (CFRP) composites has been driven by environmental and circular economic aspects. The main aim of this research work is to investigate the strength retention of a bio-based vitrimer composite reinforced with carbon fibers, which offers both recyclability and material reusability. The composite formulation consisted of an epoxy resin composed of diglycidyl ether of bioshpenol A (DGEBA) combined with tricarboxylic acid (citric acid, CA) and cardanol, which was then reinforced with carbon fibers to enhance its performance. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were performed to analyze the chemical composition and curing behavior of the vitrimer. Mechanical testing under tensile loading at room temperature was carried out on epoxy, vitrimer, and associated carbon fiber reinforced composite materials. The results demonstrated that the DGEBA/CA/cardanol vitrimer exhibited thermomechanical properties comparable to those of an epoxy cured with petroleum-based curing agents. It was observed that the maximum tensile strength of vitrimer is about 50 MPa, which is very close to the range of epoxy resins cured with petroleum-based curing agents. Notably, the ability of the vitrimer composite to be effectively dissolved in a dimethylformamide (DMF) solvent is a significant advantage, as it enables the recovery of the fibers. The recovered carbon fiber retained comparable tensile strength to that of the fresh carbon composites. More than 95% strength was retained after the first recovery, which confirms the use of fibers for primary and secondary applications. These research results open up new avenues for efficient recycling and contribute to the overall sustainability of the composite material at an economic level.

The Influence of In-Mould Annealing and Accelerated Ageing on the Properties of Impact-Modified Poly(Lactic Acid)/Biochar Composites

In the last few decades, a large number of natural additives have been analysed in connection with the improvement of the properties of poly(lactic acid) (PLA) bioplastic materials. This article comprehensively analyses the applicability of a highly stable and progressive multifunctional additive produced from renewable resources—biochar. The effect of biochar on the structural development and various thermo-mechanical properties was evaluated as a function of the biochar size and volume, addition of an impact modifier and in-mould annealing during injection moulding. In addition, the effect of accelerated ageing on the change in properties was also analysed. The evaluated results showed a significant influence of the particle size and biochar content on the properties of PLA biocomposites. However, the crucial aspect was the production process with a higher mould temperature and longer production time. Consequently, the effect of additives with adjusted processing worked synergistically on the performance of the resulting biocomposites. The accelerated ageing process did not induce any significant changes in the mechanical, impact and heat resistance behaviour of neat PLA. On the other hand, significant effects on the behaviour of the modified PLA biocomposites were observed. Impact-modified PLA achieved a toughness of 28 kJ/m2, an increase of 61% compared to neat PLA. Similar observations were made when submicron biochar was incorporated into the PLA matrix (a 22% increase with PLA/5B1). These increases were even more pronounced when injected into a 100 °C mould. Due to the synergistic effect, excellent impact toughness results of 95 kJ/m2 (a 428% increase) were achieved with PLA/IM/5B1. Moreover, these results persisted even after accelerated ageing.

Repurposing ABS to Produce Polyamide 6 (PA6)-Based Blends: Reactive Compatibilization with SAN-g-MA of a High Degree of Functionalization

In this study, recycled acrylonitrile-butadiene-styrene terpolymer (ABSr) was reused to produce polyamide 6 (PA6)-based blends. This was achieved through reactive compatibilization using styrene-acrylonitrile-maleic anhydride (SAN-g-MA) copolymer with a high degree of functionalization (6–10% MA). The PA6/ABSr and PA6/ABSr/SAN-g-MA blends were prepared through melt processing and injection molding and then analyzed for their rheological, mechanical, thermomechanical, thermal, and structural properties, as well as morphology. The torque rheometry revealed a maximum reactivity of the PA6/ABSr (70/30 wt%) blend with low SAN-g-MA (5 phr—parts per hundred resin) content, while above this threshold, torque began to decline, indicating compatibilizer saturation in the interface. These findings were further substantiated by the increase in complex viscosity and the lower melt flow index (MFI) of the PA6/ABSr/SAN-g-MA (5 phr) blend. The 5 phr SAN-g-MA reactive compatibilization of the PA6/ABSr blends significantly enhanced its impact strength, elongation at break, tensile strength, and heat deflection temperature (HDT) by 217%, 631%, 12.6%, and 9.5%, respectively, compared to PA6/ABSr. These findings are promising for the plastic recycling field, paving the way for the production of new tailor-made materials at a reduced price.