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This paper presents two methods for deformation energy or dynamic for measuring and calculating the torsion modulus, G, for composites with hollow glass microsphere (HGM) additives in unsaturated polyester resin. First, we constructed a measurement system with a torsion pendulum, a force sensor (FS), and a rotational movement sensor (RMS). Then, we deduced a relationship between force (F) and torsion angle (θ) to obtain G by deformation energy. Second, using the relaxation curve, θ in function time (t), we deduce an equation that could return the value of G for dynamic. Both techniques are non-destructive and independent of knowing the value of Poisson's ratio. We used samples of approximately 5.00 mm diameters, and the influence percentage of HGM additives differed from that of 100%Wt resin. They obtained G values by opting for these composite materials' different methods, showing a maximum deviation of 5.44%. [ABSTRACT FROM AUTHOR]

This work presents an alternative to studying and determining the torsion modulus, G, in composites. For this purpose, a measuring system used a rotational motion sensor coupled to a torsion pendulum. The determination of the angular position as a function of time and an equation derived from studies of mechanical spectroscopy, allowed to determine the value of G, so experiments focused on samples of different quantities of hollow glass microspheres (HGMs) in unsaturated polyester resins. The G results show that the addition of HGMs (16.67 %W) reduces the value of torsion modulus by 31% when compared to the unsaturated resin (100 %W). On the other hand, considering the same two samples, there is a material density reduction of approximately 43% with the addition of HGMs, which makes these materials lighter, and of great practical interest. The relationship between G and material density shows that it is possible to change the amount of HGMs for optimal torsion resistance. The advantage of this technique, compared to other dynamic methods, is that it is not necessary to know the Poisson's ratio of the material. [ABSTRACT FROM AUTHOR]

This study is dedicated to conducting a comprehensive examination, both experimentally and numerically, to characterize the mechanical properties of a composite material composed of Alfa fibres and unsaturated polyester resin. In pursuit of this objective, we diligently prepared composite specimens in accordance with the ASTM D3379-75 standardization. The Alfa fibres used were prepares using a purely natural-based extraction technique, which retains approximately 78% of the composite's performance achieved through chemical treatment. The resulting composite consists of polyester resin reinforced with varying weight fractions of fibres, ranging from 0 to 18%.The test results of the manufactured bio-composite show that specimens with an 18% weight fraction offer a tensile strength of 49.749 MPa, whereas specimens with a 10% weight fraction exhibit a strength of 44.312 MPa. Additionally, the specimens with 18% fibre reinforcement exhibit a net increase in Young's modulus by 46% compared to the fibre-free composite, with Young's modulus ranging from 1469.66 MPa to 2726 MPa. When compared with composites based on fibre glass, the introduced bio-composite with 18% Alfa fibres exhibits similar stiffness to that of glass fibres. Additionally, the outcomes from the Finite Element Model (FEM) reveal a remarkable agreement with the experimental data, underscoring the practical applicability of the proposed methodology and tools for accurately simulating tensile tests in composite structures. [ABSTRACT FROM AUTHOR]

The present study has been conducted to investigate the protective effect of graphitic carbon nitride quantum dots (CNQDs) against high energetic and harmful ultraviolet (UV) rays in addition to strengthening impact of CNQDs over mechanical and viscoelastic properties of unsaturated polyester (UP). To achieve this purpose, CNQDs were synthesized using citric acid and extra urea via microwave-assisted method. Afterwards, several percentages of CNQDs (0.25, 0.5 and 0.75 wt%) were added to UP and after curing process, UP/CNQDs nanocomposites were obtained with different percentages. By certain microscopic and spectroscopic tests, correctness of CNQDs formation and various features of UP/CNQDs nanocomposites were examined. Adding CNQDs to the matrix of polyester resin allowed creation of nanocomposites with fluorescence emission ability, also blockage of UV rays by the strengthened samples. Strengthening UP by CNQDs resulted in growth of thermal stability, improvement of tensile strength, 10%–15% increase in flexibility, and progress in viscoelastic characteristics including storage modulus, Tg and cross-linking density. [ABSTRACT FROM AUTHOR]

This work aims to investigate the potential of nonwovens made from untreated (U) and alkaline/bleaching treated (T) palm, wool, and polyester fibers as reinforcing materials in polyester matrix for automotive interior applications. Four needle-punched nonwovens were developed and used with and without chloropropyltriethoxysilane (CPTS) treatment as polyester matrix fillers. Eight composite panels were made using the resin transfer molding machine process and compared to the matrix panel in terms of physical, mechanical, thermal, and climate resistance. The produced composite materials have smooth surfaces and provide consumers with four different aesthetically pleasing finishes. The physical results reveal that the UPalm/Wool and UPalm/Polyester nonwovens lower matrix density from 1223.3 Kg/m3 to 1022.3 and 1040.7 Kg/m3, respectively. The SEM images show that palm fibers are more adherent to the matrix after being treated with an alkaline/bleaching solution. This adhesion is also improved after nonwovens are treated with the CPTS precursor. The composite reinforced with CPTS-treated TPalm/Polyester nonwoven has the highest tensile strength and modulus (72.1 MPa and 3.76 GPa), which are 127% and 36% greater than those of the polyester matrix, respectively. The matrix's flexural strength and modulus are also enhanced by 148% and 59%, respectively, after reinforcing with CPTS-treated TPalm/Polyester nonwoven. The use of TPalm/Wool and TPalm/Polyester nonwovens as polyester matrix fillers reduces their thermal conductivity from 0.125 W/(m.K) to 0.081 and 0.095 W/(m.K), respectively. Moreover, the climate aging results indicate that composites reinforced with CPTS-treated nonwovens are more stable to climate, implying their applicability and durability in automotive interior applications. [ABSTRACT FROM AUTHOR]

Two types of polymer waste materials, poly(ethylene terephthalate) (PET) and polycarbonate based Colombian Resin (CR-39), were used for the designing of fully recycled composite materials. Waste PET was employed for the synthesis of thermoset unsaturated polyester resin (UPR), while CR-39 was used as reinforcement in the UPR matrix. Prior to mixing, CR-39 particles were subjected to oxidation and chemical activation using acids/base and ethanol amine, respectively. The effect of the modifier type and variable loading of the activated CR-39 particles on mechanical and dynamic-mechanical properties of the corresponding composites was investigated. The greatest improvement in the tensile and flexural strength of UPR resin was achieved with the composite containing 0.5 wt% of amine activated filler particles, 96.0% and 62.2%, respectively. The Arrhenius equation was used to calculate the activation energy for glass transition from dynamic mechanical properties measured at various frequencies. The activation energy of the main transition for UPR resin and composites were calculated to be 173 and 350 kJ·mol−1 indicating that reinforcement results in an increase in the energy barrier to macromolecules viscoelastic relaxation. In addition, erosion resistance was studied during exposure of samples to cavitation tests. According to the obtained results, these materials can be applied in construction and mining industry. [ABSTRACT FROM AUTHOR]

Two types of alumina particles, commercial (c-Al2O3) and iron doped (Fe-Al2O3), were functionalized with 3-(aminopropyl)trimethoxysilane (one-step) and two-step consecutive process, i.e. firstly using 3-(aminopropyl)trimethoxysilane followed by methyl ester of linseed oil (biodiesel) to produce Al2O3ATPMS-BD reinforcement, respectively. The effect of modifier type and variable amount of alumina particles on the dynamical and mechanical properties of unsaturated polyester resin–based composites was studied. The highest improvement of the tensile strength and micro Vickers hardness, 78.1 and 163%, respectively, was obtained at 1.0 wt% of Fe-Al2O3APTMS-BD addition. The obtained multifunctional composites can be potentially applied in construction and mining industries. [ABSTRACT FROM AUTHOR]

This research article investigated the notch sensitivity of two different glass fibre architectures, namely short and 2D plain-woven glass fibres reinforced with unsaturated polyester and epoxy matrix composites fabricated by the hand lay-up technique. This was carried out through open hole tension tests at different ratios of the specimen hole diameter to the specimen with three different values (0.1, 0.2, 0.5) compared to the unnotched specimen. The notch sensitivity of these composites was evaluated using the residual tensile strength by the application of Whitney–Nuismer Mathematical Model. The results showed that by using polyester matrix, the notch sensitivity of composites reinforced with plain-woven glass fibre is higher than that of short glass fibre at different D/W ratios. On the other hand, on testing epoxy matrixes, the notch sensitivity of composites reinforced with plain-woven glass fibre is lower than that of short glass fibre at different D/W ratios. [ABSTRACT FROM AUTHOR]

The effect of the incorporation of silica nanoparticles on structural relaxation and curing kinetics of unsaturated polyester resin was investigated. The evaluations were made monitoring the curing behavior of the neat unsaturated polyester resin and the resin containing 3 wt% SiO2 nanoparticles using dynamic differential scanning calorimetry at heating rates of 2, 2.5, 3, and 3.5℃ min−1. Results revealed a salient increase in the redox activation energy of the unsaturated polyester resin containing silica, while the activation energy of thermal decomposition of peroxide did not show any change. On the interface of nanoparticles and matrix resin, the dissociation reaction of cobalt naphthenate reduced the effect of the promoter. Differential scanning calorimetry was also used to estimate the average size of cooperative rearrangement region of the nanocomposite. Results revealed the possible grafting of unsaturated polyester onto the nanoparticle surface. The attractive interaction between the matrix and nanoparticle hindered segmental relaxation of the polymer chains. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate the potential of encapsulated unsaturated polyester resin toward introduction of temperature-triggered healing functionality in a representative cycloaliphatic epoxy matrix. Unsaturated polyester resin was encapsulated in poly(urea–formaldehyde) shell by dispersion polymerization technique which resulted in the formation of free-flowing microcapsules (diameter ∼130 ± 49 µm) with a core content 58 ± 4%. Calorimetric studies confirmed the chemical activity of the encapsulated unsaturated polyester resin, which spontaneously polymerized in the presence of a free radical initiator, 2,2′-azobis(2-methylpropionitrile), at temperature as low as 80°C. Temperature-triggered healing of epoxy-microcapsule composites was performed at 110°C and the healing efficiency was quantified as the ratio of impact strength of healed and virgin specimens. The healing efficiency was found to increase with the increasing amount of microcapsule in the formulation and reached a maximum (100 ± 2%) at 20% (w/w) loading. Fractographic analysis of the surface revealed the flow pattern of chemically active resin from the ruptured microcapsules, which subsequently cured in the presence of 2,2′-azobis(2-methylpropionitrile) pre-dispersed in the matrix. [ABSTRACT FROM AUTHOR]

In recent years, a few research studies have been published on the blending of unsaturated polyester and phenolic resins for the purpose of improving the fire properties of unsaturated polyester resins. However, there has been no published study on the cure and strain monitoring of unsaturated polyester/phenolic blends during composite manufacturing. In this study, non-crimp triaxial glass fabric preforms were infused with the unsaturated polyester/phenolic blends, and the strain developments inside the composites were monitored using fibre Bragg grating sensors, as the long and complex curing stages were progressing at different temperatures. Strain-free fibre Bragg grating sensors and also thermocouples were utilised for temperature monitoring and compensation in order to obtain true strain developments and residual strains. The results were associated with a study presenting the cure analyses of unsaturated polyester/phenolic blends. The unsaturated polyester and the phenolics were found to be incompatible and exhibited different curing mechanisms in the blends, which were also observable in the strain development results. This paper has been the first attempt to (i) process these novel resin systems in the vacuum infusion process and (ii) monitor the long, complex and high-temperature cure cycles and the strain developments in the vacuum infusion process using fibre Bragg gratings. [ABSTRACT FROM AUTHOR]

This study presents the cure kinetics and cure modelling of an ambient curing unsaturated polyester (UP) resin system for its cure simulation in the vacuum infusion (VI) process. The curing of the UP resin system was investigated using differential scanning calorimetry (DSC). The dynamic DSC test measurements were conducted to find out the ultimate heat of reaction and enable experimental conversion determination for the isothermal curing. The empirical autocatalytic cure kinetics model incorporating the Arrhenius law represented the cure behaviour. The results of the cure kinetics study, the cure model, the material properties and the boundary conditions were the inputs in PAM-RTM software for the simulation of the degree of cure and the exothermic temperature during the infusion and the room temperature curing stages. The simulation results were compared with experimentally measured data. A vacuum infusion (VI) experiment involving a non-crimp glass fibre preform was performed in order to monitor the curing using thermocouples and validate the temperature simulation result. It was shown that the degree of cure and the exothermic temperature of a room temperature curing thermoset resin system during the VI process could be predicted through the steps of this study. [ABSTRACT FROM AUTHOR]

This paper presents the complex phenomena occurring during the wetting of natural fibers with epoxidized soybean oil/polyester in terms of contact angle and surface energy. The fibers are treated with various reagents to improve the wetting behavior. The observations demonstrate that NaOH treatment removes hemicelluloses and other impurities to a greater extent as observed through Fourier transform infrared spectroscopy and scanning electron microscopy. Besides, it is further noted that there is a considerable amount of increase in surface area of the exposed cellulose that aids in enhancement of wettability characteristics. Conversely, there is a formation of virtual layer on the fiber when treated with silane and isocyanate. An evaluation indicates coherence for silane and isocyanate-treated fiber when expressed in terms of contact angle and surface energy. Moreover, isocyanate-treated fiber exhibits good wetting in epoxidized soybean oil resin which may be attributed to change in polarity. Thermogravimetric analysis studies reveal that there is an appreciable enhancement in thermal stability for all the treatments. [ABSTRACT FROM AUTHOR]

Viscose fabric-reinforced unsaturated polyester composites were successfully prepared through vacuum infusion process. Unidirectional viscose fabric was modified by two different organosilane coupling agents and by acetylation treatment. The main objective was to study the influence of fabric treatment on the mechanical and water absorption properties of the composites. Flexural, tensile and impact properties of composites were studied. The results from mechanical testing of composites pointed out that 3-aminopropyltriethoxy silane treatment increased the flexural and impact strengths of the composites with respect to untreated fabric composite. The impact strength of 3-aminopropyltriethoxy silane-treated fabric composites almost doubled compared to the value of untreated fabric composite. Among all the composites under study, those with fabrics treated by 2 vol% 3-aminopropyltriethoxy silane in ethanol/water (95:5) solution exhibited significant improvement in water uptake resistance. An unsaturated polyester gelcoat and topcoat were applied as the outer surface on the composites with untreated fabric. This was done in order to investigate the visual surface appearance and evaluate the gelcoat and topcoat effect on water absorption after accelerated water immersion test. The regenerated cellulose fibre as reinforcement shows high potential to be used as an alternative for natural bast fibres, especially, when toughness of material matters. Chemical treatment of regenerated cellulose fibres could result in improvement in properties of polymer composites, considering that the appropriate treatment method is selected for the corresponding fibre–matrix system. [ABSTRACT FROM PUBLISHER]

In this paper, the influence of different submicron-scaled particles (zinc oxide, titanium dioxide, or silica) on mechanical and thermo-mechanical properties of unsaturated polyester matrix composites reinforced with glass fabric was investigated. Surface morphology of obtained composites was also examined. At first inorganic particles were mechanically dispersed into unsaturated polyester resin system as per the calculated weight ratio (2 or 4 wt% of polymer matrix). For prepared liquid dispersions viscosity was measured. Composites were produced by using hand lay-up method and contained 39–41 wt% of glass fibers. The flexural and dynamic mechanical analyses were carried out for each group of fabricated polyester/glass composites. All results were compared with the control samples (without submicron particles). It was found that addition of 2 wt% ZnO or TiO2 to unsaturated polyester resin enhanced the flexural strength and flexural modulus of composites. Dynamic mechanical analysis showed the increase of storage and loss modulus. Similar effect of submicron-scaled inorganic particles on Tg value of composites was observed. The scanning electron microscopic analysis of prepared composites showed good dispersion of submicron particles in polymer matrix and generally absence of voids was also observed. [ABSTRACT FROM AUTHOR]

The present work deals with the valorization of the lignin. The lignin is a by-product of the black liquor of the paper industry, which has a very complex composition structure. In this study, this lignin is obtained from the Alfa grass (Stipa Tenacissima L, also named Esparto grass). A composite material with polymer matrix (unsaturated polyester) reinforced with the lignin at various proportions has been elaborated and a comparison of its mechanical and physico-chemical characteristics to another type of composite material constituted of polymer matrix (unsaturated polyester) reinforced with Alfa fibers has been achieved. The characterization of these composites materials is based on tensile as well as thermal degradation tests under isothermal conditions. In order to explain the deviation from the linear profile (weight losses), a mathematical model has been used to show that the degradation energy is the same for all temperature ranges. This model allowed us to calculate the activation energy (48 kJ/mole.K), which corresponds to the process of off-gassing, break of macromolecular chains and weight loss. [ABSTRACT FROM PUBLISHER]

With successful applications in every other field, composites have been used in making boats, offshore structures and various marine structural applications for past few decades, owing to their superior strength-to-weight ratio and performance-to-cost ratio. Usually, marine environment poses serious challenges to the choice of materials due to the presence of corrosive seawater which significantly decreases their life-time. Slowly, nanocomposites are increasingly becoming popular because of nanoscale effects, large interface area and strong interfacial interactions between nanoparticles and polymer. In the present study, Silicon dioxide nanofillers were used as additive in order to enhance the barrier property of composites against water diffusion and hence to prevent it from mechanical degradation. Being one of the most commonly used resin for making composites, unsaturated polyester was chosen for study. Resistance to sea-water diffusion and water absorption rate was studied while varying parameters like ambient temperature and salinity of water. It was observed that the presence of nanoparticles significantly decreases the maximum water uptake and moisture diffusivity in the composite. It was also found that as the salinity of sea-water increases and temperature decreases, degradation due to water absorption decreases. [ABSTRACT FROM AUTHOR]