Dynamic Mechanical Thermal Analysis Research Articles

Enzymatic synthesis of furan-based copolymers: Material characterization and potential for biomedical applications.

Today's growing demand for advanced and sustainable polyester materials is driven by an increasing awareness of the environmental impact of traditional materials, emphasizing the need for eco-friendly alternatives. Sustainability has become central in materials development, including the biomedical area, where biobased and environmentally friendly solutions are a rapidly growing field. This research aims to comprehensively evaluate a new enzymatically catalyzed furan-based copolymer, poly(decamethylene furanoate)-co-(dilinoleic furanoate) (PDF-DLF), with a 70-30 wt% hard-to-soft segment ratio. Then, its performance across medical applications is explored, with a particular focus on its potential as a nanofibrous scaffolding material. PDF-DLF was synthesized from biobased monomers using Candida antarctica lipase B (CAL-B) as the biocatalyst. Material characterization included dynamic mechan‑ical thermal analysis (DMTA) to assess the mechanical behavior and thermal properties. Enzymatic degradation studies determined biodegradability, while cytotoxicity tests established in vitro biocompatibility. The copolymer was electrospun into nanofibers, with scanning electron microscopy (SEM) employed to analyze their morphology. PDF-DLF displays mechanical and thermal properties indicating high storage modulus and 2 main temperature transitions. Enzymatic degradation studies and cytotoxicity assessments confirm biodegradability and in vitro biocompatibility. Electrospinning successfully transformed the copolymer into nanofibers with diameters ranging from 500 nm to 700 nm. This study significantly advances our understanding of sustainable polyesters with versatile processing capabilities. The successful electrospinning highlights its potential as a biodegradable scaffold for medical engineering, supported by biocompatibility and sufficient mechanical properties. It opens new opportunities for sustainable materials in critical biomedical industries, including tissue engineering.

Thermophysical Properties of Composite Metal-Filled Copolymers of Polyvinylpyrrolidone

The effect of the presence of finely dispersed metal fillers of various natures (Zn, Co, Ni) on the thermophysical characteristics (Vick heat resistance, glass transition temperature) of polyvinylpyrrolidone block copolymers with 2-hydroxyethylmethacrylate was studied. It was found that the heat resistance of the obtained composites significantly exceeds the heat resistance of unfilled copolymers and is in the range of 360-395K, depending on the nature and content of the metal filler. The change in heat resistance correlates with the change in glass transition temperature, which was evaluated according to the results of thermomechanical and dynamic mechanical thermal analyses. The results of this work are an additional source to characterize the structure of metal-filled copolymers: they confirm the participation of metal filler particles in the formation of the nodes of the copolymer spatial network, and also prove the formation of a different polymer network structure in the interfacial layer on the surface of the metal particle and in the polymer volume.

Effects of carbon‐based nanoparticles on the properties of poly(lactic acid) hybrid composites containing basalt fibers and carbon‐based nanoparticles processed by injection molding

AbstractIn this study, we developed composites with a poly(lactic acid) matrix and reinforced with basalt fiber, carbon‐based nanoparticles (carbon nanotube [CNT] and expanded graphene [GNP]), and both basalt fiber and nanoparticles (hybrid composites). The composites were produced by extrusion, and then tensile specimens were injection molded from the composites. The hybrid composites exhibited enhanced mechanical properties. The reinforcing materials increased crystallinity; this was more pronounced for hybrid composites. We experienced significant increase in the glass transition temperature, which proves the better interaction between the reinforcing and the matrix phases. Dynamic mechanical thermal analysis showed that the nanoparticles increased the storage modulus both alone and in combination with basalt fibers. Furthermore, the basalt fiber‐reinforced composites and hybrids exhibited significant modulus above the glass transition temperature. Based on scanning electron microscopy images of the fracture surfaces, we concluded that adding basalt fibers during compounding resulted in better dispersion of the nanoparticles.Highlights Poly(lactic acid) (PLA) reinforced with basalt fiber has good strength properties. Graphene hybrid exhibits notable tensile modulus improvement in hybrids. Graphene and carbon nanotubes are crystalline nucleating agents for PLA. Enhanced nanoparticle distribution was discovered for hybrid composites. The glass transition temperature of PLA increases with reinforcement.

Development of starch-rich thermoplastic polymers based on mango kernel flour and different plasticizers

This work reports on the development of starch-rich thermoplastic based formulations produced by using mango kernel flour, avoiding the extraction process of starch from mango kernel to produce these materials. Glycerol, sorbitol and urea at 15 wt% are used as plasticizers to obtain thermoplastic starch (TPS) formulations by extrusion and injection-moulding processes. Mechanical results show that sorbitol and urea allowed to obtain samples with tensile strength and elongation at break higher than the glycerol-plasticized sample, achieving values of 2.9 MPa of tensile strength and 42 % of elongation at break at 53 % RH. These results are supported by field emission scanning electron microscopy (FESEM) micrographs, where a limited concentration of voids was observed in the samples with sorbitol and urea, indicating a better interaction between starch and the plasticizers. Thermogravimetric analysis (TGA) shows that urea and sorbitol increase the thermal stability of TPS in comparison to the glycerol-plasticized sample. Differential scanning calorimetry (DSC) and dynamic-mechanical-thermal analysis (DMTA) verify the increase in stiffness of the sorbitol and urea plasticized TPS and also illustrate an increase in the glass transition temperature of both samples in comparison to the glycerol-plasticized sample. Glass transition temperatures of 45 °C were achieved for the sample with sorbitol.

Biocomposites Based on Wheat Flour with Urea-Based Eutectic Plasticizer and Spent Coffee Grounds: Preparation, Physicochemical Characterization, and Study of Their Influence on Plant Growth.

In this study, we conducted the first plasticization of wheat flour (WF) with the addition of choline chloride:urea (1:5 molar ratio) eutectic mixture as a plasticizer and spent coffee grounds (cf) as a filler. Thermoplastic wheat flour (TPWF) films were obtained via twin-screw extrusion and then thermocompression. Their physicochemical characterization included mechanical tests, dynamic mechanical thermal analysis (DMTA), and sorption tests. XRD analysis revealed that the eutectic plasticizer led to a high degree of WF amorphization, which affected the physicochemical properties of TPWF. The results indicated that it was easy for the TPWF biocomposites to undergo thermocompression even with a high amount of the filler (20 pph per flour). The addition of the cf into TPWF led to an increase in tensile strength and a decrease in the swelling degree of the biocomposites. Biodegradation tests in soil revealed that the materials wholly degraded within 11 weeks. Moreover, a study of cultivated plants indicated that the biocomposites did not exhibit a toxic influence on the model rowing plant.

Influence of LLDPE on the mechanical properties improvement of 3D printed POE/LLDPE blends

AbstractPolyolefins and polyolefin elastomers (POEs) are widely used in various applications due to their unique properties. However, their use in 3D printing has been limited due to challenges such as excessive softness, shrinkage, warpage, and poor mechanical properties. In this study, two strategies were employed to enhance the performance of POEs in 3D printing. First, POE was blended with 10%, 30%, and 50% percentages of linear low‐density polyethylene (LLDPE) to improve the material's mechanical properties and printability. Second, a specialized printer called a pneumatic feeding fused granule fabrication (FGF) printer was used. This printer allows for the direct printing of material granules, eliminating the need for filaments and resolving filament‐related problems. To evaluate the quality of the printed parts, tensile tests, dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM) imaging were conducted. The printed parts showed desirable tensile properties (with approximately 3000% elongation at break and approximately 12 MPa tensile strength). Compression tests were also conducted on cubic structures with varied composition ratios and printing patterns such as grid, triangle, and honeycomb. The main purpose of this research was to explore the energy absorption capabilities of the printed blends. The results of our study showed that blending POE with LLDPE improved printability, tensile strength, energy absorption, and compressive properties. The blend with 50% LLDPE and honeycomb structure exhibited the best compressive and energy absorption properties.Highlights Blending of POE and LLDPE using melt mixing with three different blending ratios. Successful 3D printing with the fused granule fabrication technique. Investigating mechanical properties, microstructure, and thermal analysis. 125% increase in ultimate tensile strength by increasing LLDPE. Achieving the highest energy absorption for the 3D printed honeycomb structure.

Effects of TPU on the mechanical properties, fracture toughness, morphology, and thermal analysis of 3D‐printed ABS‐TPU blends by FDM

AbstractIn this paper, blends of ABS‐TPU with two different weight percentages of TPU were prepared using fused deposition modeling technology. The effect of adding TPU on the fracture toughness of ABS and mechanical properties was comprehensively studied. Tensile, compression, fracture toughness, and shear tests were conducted on the 3D‐printed samples. Thermal and microstructural analyses were performed using dynamic mechanical thermal analysis (DMTA), and scanning electron microscope (SEM). The DMTA results showed that adding TPU decreased the storage modulus and the glass transition temperature of ABS, as well as its peak intensity. The mechanical test results showed that adding TPU decreased the strength but increased the formability and elongation of the samples. Fracture tests showed that the addition of TPU decreased the maximum force needed for a crack to initiate. The force required for crack initiation decreased from 568.4 N for neat ABS to 335.3 N for ABS80 and 123.2 N for ABS60. The ABS60 blend exhibited the highest strength against crack growth, indicating that TPU can change the behavior of ABS from brittle to ductile. Shear test results and SEM images also showed good adhesion strength between the printed samples for all three specimens, indicating their good printability. Adding TPU resulted in a reduction in the size and number of voids and holes between the printed layers.Highlights Melt mixing, filament preparation, and 3D printing of ABS‐TPU blends. Investigation of mechanical properties, microstructure, and fracture toughness. Improved resistance to crack growth and elongation by adding TPU to ABS. Improving printability and reducing microholes in blends compared with ABS. Achieving a wide range of mechanical properties for various applications.

Microwave curing of modified benzoxazine resin/ethylene–propylene–diene monomer rubber/Kevlar composite

AbstractThe purpose of this paper was to show how modified benzoxazine resin/ethylene–propylene–diene monomer rubber/Kevlar composites are prepared. The compatibilization of polar benzoxazine resin and non‐polar EPDM was carried out by EPDM‐g‐MAH copolymer synthesized as a compatibilizer, and then, the microwave (MW) irradiation method and conventional thermal cure (CV) were used to cure this composite. The samples cured by both methods were evaluated and compared by differential scanning calorimetry analysis (DSC), dynamic mechanical thermal analysis (DMTA), scanning electron microscope (SEM), and thermo‐gravimetric analysis (TGA). Microwave curing significantly reduced the curing time, and the composites cured with MW irradiation had higher glass transition temperature (Tg), more uniform curing, higher cross‐link density, and more thermal stability than CV‐cured composites.Highlights Constructing BZ/EPDM/Kevlar thermal composite for use at high temperatures. Using modified resin to reduce curing temperature and improve final properties. Creating compatibility between non‐polar EPDM rubber and polar BZ resin. Investigating and comparing between thermal and MW curing of the composites.

Mechanical behavior of carbon/glass polypropylene hybrid composites

AbstractThis research investigates the influence of graphene and some additives on the mechanical behavior of polypropylene (PP). Anhydride maleic coupling agent (MAPP), graphene nanoplatelets (GNPs), and glass fiber (GF) were incorporated into the polymer matrix. The incorporation of MAPP and/or GNP significantly improved the affinity between the PP matrix and fibers while altering the surface morphology. More than 60% of the fibers showed a dimension lower than 0.5 mm. The tensile strength increased from 27.45 to 41 MPa for the neat PP compared to one of the composites. The strength modulus varied from 0.5 to 0.9 GPa. Mechanical tests showed that the addition of MAPP improved the tensile toughness (from 27.45 to 41 N mm mm−2) by 49%, while the GF increased tensile strength, albeit reducing elongation at break. The dynamic mechanical thermal analysis uncovered distinct behavioral variations among fiber‐reinforced samples, particularly in modulus peak differences. In rheological assessment, the presence of GF notably increased viscosity within certain shear rate ranges (at 100 [1/s], the viscosity goes from 200 to 300 Pa s to neat PP for some composites). This research highlights how chosen additives can influence a PP homopolymer's properties, offering useful insights for practical material processing and design.Highlights MAPP and GNP can increase PP and glass fiber interfacial bonding. Glass fiber raises tensile strength and decreases elongation. Sample with just GNP has a rougher surface, implying better energy dissipation. Glass fiber raises viscosity in the observed shear rate ranges. DMA demonstrates that MAPP and GNP have an influence on energy dissipation.

Morphological, compatibility, rheological and mechanical properties of graphene oxide/PLA/XNBR-g-GMA/XNBR: empirical and theoretical approaches

ABSTRACT The incompatible thermoplastic poly lactic acid/carboxylated acrylonitrile butadiene rubber (PLA/XNBR) was prepared, and the effect of graphene oxide (GO) as a reinforcement and glycidyl methacrylate (GMA)-grafted XNBR (XNBR-g-GMA) as a compatibilizer on the properties of PLA/XNBR blend was investigated in this research. The microstructure, mechanical behavior, thermal, rheology, and dynamic mechanical properties of PLA/XNBR composites were investigated by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), tensile test, and dynamic mechanical thermal analysis (DMTA). The incorporation of XNBR-g-GMA improved the compatibility of the PLA/XNBR blend phases, as confirmed by microstructure and DMTA analysis. The results of the mechanical properties showed that with an increase in GO content in the PLA/XNBR/XNBR-g-GMA matrix, there was a significant improvement in tensile strength, Young’s modulus, hardness, and impact strength. In order to validate the experimental mechanical and rheological results, various theoretical models were applied and a good agreement was observed between the theoretical and experimental data.

Mechanical, Rheological, and Heat Seal Properties of 1‐Octene Grafted Low Density Polyethylene Films

AbstractHeat seal and mechanical properties of 1‐octene grafted low density polyethylene films containing various concentrations of Dicumyl peroxide as the initiator and 1‐octene grafting agent is investigated through using experimental measurements. The results of differential scanning calorimeter (DSC) measurements revealed that the melting temperature shifts to higher values and the peak of the DSC curve becomes wider with the increase of 1‐octene concentrations. Thermogravimetric analysis (TGA) revealed a higher thermal stability up to 20 °C for 1‐octene grafted PE compared with neat LDPE alloy. The results of stress–strain measurements revealed that the 1‐octene grafted PE alloys has higher tensile strength in comparison with neat PE alloy and samples containing only DCP initiator. The results of heat seal analysis indicated that both DCP initiator and 1‐octene tended to offer a moderate increase peel strength of PE alloy. DMTA measurements for various grafted PE alloys show a higher damping factor in comparison with neat LDPE alloy. Rheological measurements indicated a higher storage modulus up to 25% and higher complex viscosity for grafted PE samples containing 1‐octene comonomer.

Biodegradable Nanocomposites Based on Blends of Poly(Butylene Adipate-Co-Terephthalate) (PBAT) and Thermoplastic Starch Filled with Montmorillonite (MMT): Physico-Mechanical Properties.

Poly(butylene adipate-co-terephthalate) (PBAT) is widely used for production of biodegradable films due to its high elongation, excellent flexibility, and good processability properties. An effective way to develop more accessible PBAT-based bioplastics for wide application in packaging is blending of PBAT with thermoplastic starch (TPS) since PBAT is costly with prices approximately double or even triple the prices of traditional plastics like polyethylene. This study is focused on investigating the influence of TPS/PBAT blend ratio and montmorillonite (MMT) content on the physical and mechanical properties and molecular mobility of TPS-MMT/PBAT nanocomposites. Obtained TPS-MMT/PBAT nanocomposites through the melt blending process were characterized using tensile testing, dynamic mechanical thermal analysis (DMTA), and X-ray diffraction (XRD), as well as solid-state 1H and 13C NMR spectroscopy. Mechanical properties demonstrated that the addition of TPS to PBAT leads to a substantial decrease in the tensile strength as well as in the elongation at break, while Young's modulus is rising substantially, while the effect of the MMT addition is almost negligible on the tensile stress of the blends. DMTA results confirmed the formation of TPS domains in the PBAT matrix. With increasing TPS content, mobility of starch-rich regions of TPS domains slightly increases. However, molecular mobility in glycerol-rich regions of TPS domains in the blends was slightly restricted. Moreover, the data obtained from 13C CP/MAS NMR spectra indicated that the presence of TPS in the sample decreases the mobility of the PBAT chains, mainly those located at the TPS/PBAT interfaces.

Acrylate composite polyurethane binder for steel bridge deck pavements: Process optimization by response surface methodology and microanalysis

AbstractTo better serve the steel bridge deck paving project, a novel room‐temperature curing acrylate composite polyurethane binder (APUB) was developed as a substitute for traditional asphalt binders. APUB was synthesized by the copolymerization of a custom‐made polyurethane prepolymer (BDO‐PU) and acrylate. Fourier transformed infrared and proton nuclear magnetic resonance spectroscopy analyses confirmed the presence of carbamate structures in prepolymer BDO‐PU. Utilizing tensile strength, breaking elongation and water absorption as optimization criteria, the response surface methodology was used to optimize synthesis process of APUB. The results showed that the optimized parameters for APUB synthesis include an isocyanate index (R) of 1.5, a mass ratio of methyl methacrylate to BDO‐PU of 1.1, and a curing agent content of 2.7%. These settings resulted in predicted values of 10.12 MPa for tensile strength, 123.85% for breaking elongation, and 0.075% for water absorption. Experimental validation demonstrated the consistency between the predicted and actual properties of APUB. Further microanalyses, including dynamic mechanical thermal analysis, differential scanning calorimetry, and scanning electron microscope, confirmed APUB exhibits excellent component compatibility and glass transition temperatures suitable for bridge engineering environments. Overall, APUB demonstrates outstanding tensile properties, water resistance, low energy consumption, and potential applications in the steel bridge deck pavement industry.

Experimental Study and Seismic Response Evaluation of Chlorobutyl Rubber-Based Viscoelastic Dampers

Conventional viscoelastic devices often use high-damping elastomeric pads, typically made of patented formulations, that are bonded to steel plates. The response properties of these pads under cyclic shear deformations directly influence the load-deformation hysteretic response of the device. Chlorobutyl (CIIR) is a high-damping rubber commonly used in industrial applications. However, this study found that the damping properties of a typical CIIR rubber compound are insufficient for effective structural seismic mitigation at ambient temperatures above 0°C. The goal of this study was to develop a new composite of CIIR, referred to as modified CIIR, with improved damping properties and to compare its performance with that of the reference CIIR rubber. In the first phase of the experimental studies, the viscoelastic characteristics of the reference and modified CIIR rubber materials were evaluated using dynamic mechanical thermal analysis (DMTA) in tension mode. Prototype viscoelastic damper devices were then fabricated from both the reference and modified CIIR rubber materials and subjected to cyclic shear tests at room temperature and various loading frequencies. The results showed that the modified CIIR rubber exhibited significantly improved effective damping compared to the reference CIIR. The final component of this study involved investigating the seismic response of a 2D frame structure equipped with prototype dampers made from both reference and modified CIIR materials, using nonlinear time-history analyses. The analysis results indicated that the modified CIIR rubber can be effectively utilized in the seismic response mitigation of structures.

Structure versus hydrolytic and thermal stability of bio-based thermoplastic polyurethane elastomers composed of hard and soft building blocks with high content of green carbon

Nowadays, sustainability plays a key role in the design and synthesis of new materials. One of the methods for the preparation of green materials is incorporation into their structure the monomers with a high content of green carbon. Therefore, the aim of this work was to investigate the influence of the type and molecular mass of two bio-based polyester polyols and bio-glycol on the properties of aliphatic partially bio-based thermoplastic polyurethane elastomers (bio-TPU). Two series of bio-TPUs materials composed of hard and soft building blocks with high green carbon content were prepared via the two-step method (prepolymer method). Two amorphous bio-based polyester polyols with the molecular mass ~ 2000 (P1) and ~ 3000 (P2) were used. Bio-TPUs were prepared at three different molar ratio of [NCO]/[OH]: 0.9, 0.95, and 1.0. In order to determine the influence of bio-based polyols and the content of hard segments on the properties of bio-TPU, relevant test methods were used. The Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetry (TG) revealed hydrolytic and thermal stability of bio-TPUs. Viscoelastic behavior, mechanical and physical properties were examined in terms of dynamic mechanical thermal analysis (DMTA), tensile test, hardness, and density. Analysis of the measurement results confirmed the significant influence of the molecular mass of the bio-based polyols and the molar ratio of [NCO]/[OH] on the bio-TPUs properties. Due to good mechanical properties, low density, and thermal stability up to 300 °C, the obtained materials can find many useful applications. This issue is essential in terms of sustainable development and reduction in the CO2 emissions to the atmosphere.

Direct Pellet Three-Dimensional Printing of Polybutylene Adipate-co-Terephthalate for a Greener Future.

The widespread use of conventional plastics in various industries has resulted in increased oil consumption and environmental pollution. To address these issues, a combination of plastic recycling and the use of biodegradable plastics is essential. Among biodegradable polymers, poly butylene adipate-co-terephthalate (PBAT) has attracted significant attention due to its favorable mechanical properties and biodegradability. In this study, we investigated the potential of using PBAT for direct pellet printing, eliminating the need for filament conversion. To determine the optimal printing temperature, three sets of tensile specimens were 3D-printed at varying nozzle temperatures, and their mechanical properties and microstructure were analyzed. Additionally, dynamic mechanical thermal analysis (DMTA) was conducted to evaluate the thermal behavior of the printed PBAT. Furthermore, we designed and printed two structures with different infill percentages (40% and 60%) to assess their compressive strength and energy absorption properties. DMTA revealed that PBAT's glass-rubber transition temperature is approximately -25 °C. Our findings demonstrate that increasing the nozzle temperature enhances the mechanical properties of PBAT. Notably, the highest nozzle temperature of 200 °C yielded remarkable results, with an elongation of 1379% and a tensile strength of 7.5 MPa. Moreover, specimens with a 60% infill density exhibited superior compressive strength (1338 KPa) and energy absorption compared with those with 40% infill density (1306 KPa). The SEM images showed that with an increase in the nozzle temperature, the quality of the print was greatly improved, and it was difficult to find microholes or even a layered structure for the sample printed at 200 °C.

Improving water resistance and mechanical properties of starch-based films by incorporating microcrystalline cellulose in a dynamic network structure

The widespread use of starch-based films is hindered by inadequate tensile strength and high water sensitivity. To address these limitations, a novel starch film with a dynamic network structure was produced via the dehydration-condensation reaction of N, N′-methylene diacrylamide (MBA) and microcrystalline cellulose (MCC). The improvement in mechanical properties was enhanced by the incorporation of MCC, which was achieved through intermolecular hydrogen bonding and chemical crosslinking. To verify the interactions among MCC, MBA, and starch, x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD) were conducted. The results established the predicted interactions. The dynamic network structure of the film reduced the water absorption capacity (WAC) of starch and MCC hydroxyl groups, as confirmed by differential scanning calorimeter (DSC) and dynamic mechanical thermal analysis (DMTA). These analyses showed a restriction in the mobility of starch chains, resulting in a higher glass transition temperature (Tg) of 69.26 °C. The modified starch films exhibited excellent potential for packaging applications, demonstrating a higher contact angle (CA) of 89.63°, the lowest WAC of 4.73 g/g, and the lowest water vapor transmission rate (WVTR) of 13.13 g/m2/d, along with improved mechanical properties and identical light transmittance compared to pure starch films.

Characterization of nanocellulose/pyrolysis oil nanocomposite films

In this study, the sustainable recycling of tire waste, which is frequently formed in the automotive industry, and the transformation of this recycling into valuable materials are in question. Waste tire pyrolysis oil obtained as a result of the pyrolysis of tire wastes was evaluated for the first time as a reinforcement element in nanocellulose-based nanocomposite films. Nanocellulose was produced using the TEMPO method (2,2,6,6-tetramethylpiperidine-1-oxyl radical). 5 %, 10 % and 20 % pyrolysis oil were added to the nanocomposite films. Thermal (thermal gravimetric analysis, differential scanning calorimetry, thermomechanical (dynamic mechanical thermal analysis and morphological (scanning electron microscopy) characterization of the produced nanocomposite films were performed. The highest thermal stability was observed in the nanocellulose/pyrolysis oil-20 sample with 20% pyrolysis oil additive. The pyrolysis oil-reinforced nanocomposites resulted in an excellent increase in storage and loss modulus. The storage modulus of the 20 % pyrolysis oil added sample at 100 °C was exactly 18 times that of pure nanocellulose. Nanocellulose-based nanocomposite films with superior thermal properties and structural compatibility demonstrated by characterized results have been shown to be pioneers in future industrial applications such as pharmacy, coating, green packaging.

Investigation on moisture absorption behavior on GFRP and neat epoxy systems in hygrothermal salt fog aging

This work investigates the moisture absorption behavior in epoxy matrix composites reinforced with glass fibers, used in repairs of offshore topside metal pipelines exposed to aging in saline environment. The materials used were a bicomponent DGEBA epoxy and a woven bidirectional E-glass fabric. In order to simulate the harsh environment, the composites were exposed to accelerated hygrothermal aging tests in three independent salt spray chambers at temperatures of 35, 55 and 70 °C and the materials had their mass gain monitored. The moisture absorption of the neat epoxy resin was also investigated and correlated with that of the composites. Thermal analyses by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Thermal Analysis (DMTA) were performed to evaluate the curing state of the polymeric materials tested and the effects of temperature on the material's post-curing. Fourier-Transform Infrared (FTIR) analyses were performed to investigate the occurrence of post-curing, hydrolysis and thermo-oxidation processes during aging. As expected, it was seen that temperature increased diffusivity for both the composite and the unreinforced epoxy matrix. The neat epoxy resin presented a decrease in moisture absorbed with temperature, evidencing the effect of post-curing on moisture absorption. Furthermore, from the thermal analyses, it was observed the presence of an interphase between matrix and fibers with a Tg higher than the bulk matrix. Non-Fickian models confirmed structural changes caused by temperature and moisture in the materials. A modification of the Berens-Hopfenberg (BH) non-Fickian model was proposed to account for post-curing effects on moisture absorption.

Biomass- and Carbon Dioxide-Derived Polyurethane Networks for Thermal Interface Material Applications.

Recent environmental concerns have increased demand for renewable polymers and sustainable green resource usage, such as biomass-derived components and carbon dioxide (CO2). Herein, we present crosslinked polyurethanes (CPUs) fabricated from CO2- and biomass-derived monomers via a facile solvent-free ball milling process. Furan-containing bis(cyclic carbonate)s were synthesized through CO2 fixation and further transformed to tetraols, denoted FCTs, by aminolysis and utilized in CPU synthesis. Highly dispersed polyurethane-based hybrid composites (CPU-Ag) were also manufactured using a similar ball milling process. Due to the malleability of the CPU matrix, enabled by transcarbamoylation (dynamic covalent chemistry), CPU-based composites are expected to present very low interfacial thermal resistance between the heat sink and heat source. The characteristics of the dynamic covalent bond (i.e., urethane exchange reaction) were confirmed by the results of dynamic mechanical thermal analysis and stress relaxation analysis. Importantly, the high thermal conductivity of the CPU-based hybrid material was confirmed using laser flash analysis (up to 51.1 W/m·K). Our mechanochemical approach enables the facile preparation of sustainable polymers and hybrid composites for functional application.