Polyester Blends Research Articles

Harnessing extremophilic carboxylesterases for applications in polyester depolymerisation and plastic waste recycling.

The steady growth in industrial production of synthetic plastics and their limited recycling have resulted in severe environmental pollution and contribute to global warming and oil depletion. Currently, there is an urgent need to develop efficient plastic recycling technologies to prevent further environmental pollution and recover chemical feedstocks for polymer re-synthesis and upcycling in a circular economy. Enzymatic depolymerization of synthetic polyesters by microbial carboxylesterases provides an attractive addition to existing mechanical and chemical recycling technologies due to enzyme specificity, low energy consumption, and mild reaction conditions. Carboxylesterases constitute a diverse group of serine-dependent hydrolases catalysing the cleavage and formation of ester bonds. However, the stability and hydrolytic activity of identified natural esterases towards synthetic polyesters are usually insufficient for applications in industrial polyester recycling. This necessitates further efforts on the discovery of robust enzymes, as well as protein engineering of natural enzymes for enhanced activity and stability. In this essay, we discuss the current knowledge of microbial carboxylesterases that degrade polyesters (polyesterases) with focus on polyethylene terephthalate (PET), which is one of the five major synthetic polymers. Then, we briefly review the recent progress in the discovery and protein engineering of microbial polyesterases, as well as developing enzyme cocktails and secreted protein expression for applications in the depolymerisation of polyester blends and mixed plastics. Future research aimed at the discovery of novel polyesterases from extreme environments and protein engineering for improved performance will aid developing efficient polyester recycling technologies for the circular plastics economy.

Advanced Plastic Waste Recycling-The Effect of Clay on the Morphological and Thermal Behavior of Recycled PET/PLA Sustainable Blends.

Bio-based polymers such as poly(lactic acid), PLA, are facing increased use in everyday plastic packaging, imposing challenges in the recycling process of its counterpart polyester poly(ethylene terephthalate), PET. This work presents the exploration of the properties of PET/PLA blends with raw materials obtained from recycled plastics. Several blends were prepared, containing 50 to 90% PET. Moreover, multiscale nanocomposite blends were formed via melt mixing using different amounts and types of nanoclay in order to study their effect on the morphology, surface properties, and thermal stability of the blends. The materials were characterized by X-ray diffraction analysis (XRD), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The nanoclay was found to exhibit a uniform dispersion in the polymer matrix, presenting mainly intercalated structures with some exfoliated at low loading and some agglomerates at high loading (i.e., 10%). The addition of nanoclay to PET/PLA matrices increased the roughness of the blends and improved their thermal stability. Thermal degradation of the blends occurs in two steps following those of the individual polymers. Contamination of rPET with rPLA results in materials having poor thermal stability relative to rPET, presenting the onset of thermal degradation at nearly 100 °C lower. Therefore, important information was obtained concerning the recyclability of mixed PET and PLA waste. The perspective is to study the properties and find potential applications of sustainable blends of recycled PET and PLA by also examining the effect of different clays in different loadings. Therefore, useful products could be produced from blends of waste polyester.

Biodegradable block copolymer as compatibilizer and blend component of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)-based polyester blends

Atactic poly(3-hydroxybutyrate) (PHB)-b-poly(ε-caprolactone) (PCL) diblock copolymer, a type of biodegradable block copolymer (BCP) was selected as compatibilizer for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)/PCL immiscible blends. The additive effect of BCP on the morphologies and mechanical properties was dependent on the blend composition of PHBH/PCL. For 80/20 (w/w) PHBH/PCL blends, the incorporation of BCP did alter their mechanical properties by the increase in elongation at break with increasing BCP amount. However, the addition of BCP for 60/40 (w/w) PHBH/PCL blends were not greatly affected on their morphologies and mechanical properties. When BCP was used as one of binary blend components, the mechanical properties were significantly changed depending on the blend composition. PHBH/BCP blends also showed promising improvement in terms of mechanical performance. Presence of BCP in the ternary and binary blend systems decreased the enzymatic degradation rate by PHB depolymerase.

Functions and Opportunities of Sports Textiles - A Review

Sports textiles have about 10% contribution in the world’s technical textile market as compared to different textiles where individual textile has reactive importance to others. There are many essential features of sports textiles required to manufacture from textile materials. Smart textiles made for sports apparel are designed as per the needs of athletes. Fabrics used in making sports apparel are basically from natural and synthetic fibres. The class players choose fabric science for their costume for controlling and recording temperature, sweat and movement of muscles for better performance. Supporting thermoregulatory mechanisms is the main purpose of functional textiles, which improves performance. €mart textiles in sports have potential in reducing and eliminating injuries and risk of over exercising. During the period of COVID-19 outbreak, the market has not shown any significant growth. The main advantage of using cotton fibre in making fabrics for sports garments is its breathability. In sports garments manufacturing, an alternative to polyester fibres is a material made from nylon or blend of polyester.

Investigating how the dye colour is impacted when chemically separating polyester-cotton blends

Blended textile fabrics with dyed cotton and polyester (PET) fibres intimately mixed are extensively used in the textile industry. Separating and recycling these blends cannot be performed by conventional mechanical or chemical recycling processes, and this is contributing significantly to the global textile waste problem. Here we demonstrate an approach to separate coloured cotton and polyester blends, and the dye is retained in the separated polyester and cotton components. The separation was achieved via chemical dissolution of cotton using a co-solvent system of ionic liquid and dimethyl sulfoxide, from which regenerated cellulose fibres could be directly wet spun. The polyester component was left intact and recovered via filtration. The recovered products were characterised for thermal, chemical, mechanical, colour strength, and morphological properties.

Development of insecticide-impregnated polyester/cotton blend fabric and assessment of their repellent characteristics against Cimex lectularius and dengue vectors Aedes albopictus and Aedes aegypti

BackgroundPersonal protection measures using insecticide-treated fabric is one of the most effective strategies to prevent the bites of hematophagous insects. Many countries have had success treating fabrics with pyrethroids on an individual level.MethodsIn the current study, a new combination of insecticides, alpha-cypermethrin (ACP) and deltamethrin (DET), has been impregnated on fabric composed of a 50:50 blend of polyester and cotton. Residual and morphological analysis was performed along with the evaluation of physical parameters. Biological evaluations were performed to check the repellency, knockdown, and mortality of insecticide-impregnated fabric (IIF) against bed bugs (Cimex lectularius) using Petri plate assay and mosquitoes (Aedes aegypti and Aedes albopictus) using cone bioassay.ResultsThe results showed the repellency of IIF to be 56.6% for C. lectularius and a knockdown percentage of 53.3% and 63.3% for Ae. aegypti and Ae. albopictus, respectively. A > 80% mortality was found for both species of mosquitoes up to 20 cycles of washing with no significant difference (P > 0.05). From high-performance liquid chromatography (HPLC) analysis, the reduction in the contents of ACP and DET after subsequent washes can be correlated with the overall decrease in bioefficacy. ACP and DET remaining in unit gram of fabric after 20 wash cycles were found to be 5.4 mg and 3.1 mg, respectively. By examining the fabric’s surface morphology using scanning electron microscope (SEM) and utilizing energy-dispersive x-ray (EDX) analysis, it was possible to identify the presence of insecticides that were adhered to the fabric. Differential scanning calorimetry (DSC) showed distinctive endothermic peak of insecticide at 98.3 ºC, whereas no change in thermal behavior was observed from thermo-gravimetric analysis (TGA). Furthermore, the physical attributes of IIF provide conclusive evidence for its firmness.ConclusionAll experimental findings were consistent with the potential use of IIF as a bed bug- and mosquito-repellent fabric to be used against hematophagous infestations. This fabric can serve as a potential strategy to control vector-borne diseases like dengue, malaria, trench fever, etc.Graphical

Poly(Lactic Acid) / Polyester Blends: Review of Current and Future Applications

Poly (lactic acid) (PLA) is a promising polymer with its value and potential due to its sustainability, low carbon footprint, and being a superior bio-based polymer compared to other bioplastics. Since it is also a compostable aliphatic polyester, has been frequently subjected to research.
 Researchers have conducted studies on the compatibility of PLA, which is a bio-based, biodegradable, and compostable, renewable polymer, with traditional petrochemical-based polymers, especially polyesters such as polybutylene terephthalate (PBT), and polyethylene terephthalate (PET). It is highly important that applications of PLA/polyester blends will ensure that the materials developed are not only economically and sustainable but also can meet current and future appropriate needs. PLA-based materials have some disadvantages such as slow biodegradation rate, high cost, and low toughness, and to eliminate mentioned drawbacks generally blends are prepared with petroleum-based polymers.
 In this review, information about the perspectives with studies for PLA/polyester blends; approaches to the subject, potential application areas, and contributions for the future were given.

Design and laboratory performance of reactive cold patching materials containing epoxy/unsaturated polyester blends

Currently, cold patching materials (CPMs) have become a preferred choice for pothole repair on asphalt pavements in cold and wet weather, to timely restore pavement serviceability and improve traffic safety. However, the survival time of conventional asphalt-based CPMs is not satisfactory, and volatile and toxic components in emulsified or dissolved asphalt are more easily leached to cause water and air pollution, while advanced CPM that can achieve a longer repair longevity may be more cost-effective and environmentally friendly in the long term. The main objective of this paper is to develop a pollution-free, economical and high-performance CPMs to repair asphalt pavement potholes more effectively and sustainably. Specifically, a low viscosity, high toughness and low temperature curing epoxy resin (ER) binder was designed and the unsaturated polyester was selected adaptively. On this basis, the mix proportion of epoxy/unsaturated polyester-based mixture was designed and its performance of the mixture during construction and service was investigated. The results show that epoxy/unsaturated polyester mixture (EUPM) with the optimal material composition possessed excellent high temperature rutting resistance, low temperature deformation performance and water stability. The cold patching materials using EUPM and epoxy resin as the interface agent had excellent repair effect and adapted to a certain humid environment. The study proved the feasibility and advantages for the investigation utilizing EUPM as cold patching materials in asphalt pavement maintenance.

Optimization of Polyolefin-Bonded Hydroxyapatite Graphite for Sustainable Industrial Applications

As a means of introducing environmental responsibility to industrial applications, the usage of biobased composite materials has been encouraged in recent years. Polymer nanocomposites utilize polyolefins increasingly as a matrix, owing to the diversity in their features and prospective applications, even though typical polyester blend materials, such as glass and composite materials, have garnered greater attention from researchers. The mineral hydroxy-apatite, or Ca10(PO4)6(OH)2, is the primary structural component of bone and tooth enamel. Increased bone density and strength result from this procedure. As a result, nanohms are fabricated from eggshells into rods with very tiny particle sizes. Although there have been many papers written on the benefits of HA-loaded polyolefins, the reinforcing effect of HA at low loadings has not yet been taken into account. The purpose of this work was to examine the mechanical and thermal characteristics of polyolefin-HA nanocomposites. These nanocomposites were built out of HDPE and LDPE (LDPE). As an extension of this work, we investigated what would happen when HA is added to LDPE composites at concentrations as high as 40% by weight. Carbonaceous fillers, including graphene, carbon nanotubes, carbon fibers, and exfoliated graphite, all play significant roles in nanotechnology owing to the extraordinary enhancements in their thermal, electrical, mechanical, and chemical properties. The purpose of this study was to examine the effects of adding a layered filler, such as exfoliated graphite (EG), to microwave zones that might have real-world applications for their mechanical, thermal, and electrical characteristics. Mechanical and thermal properties were significantly enhanced by the incorporation of HA, notwithstanding a minor decrease in these attributes at a loading of 40% HA by weight. A higher load-bearing capability of LLDPE matrices suggests their potential usage in biological contexts.

Electrical characterization and sensing capabilities of self-assembly multi-scale multi-phase graphene-based composites

The addition of graphene particles to a thermoset resin strongly enhances its electrical properties, opening the use of such system for damage and strain tracking. This increase is, however, proportional to the amount and purity of the graphene particles, usually at high costs. Using a high amount of filler leads to a decrease in processability as well as a possible drop in mechanical properties. In order to reduce the quantity needed for conduction with few-layer graphene (FLG), a self-assembly network of graphene particles in the polymeric structure was created using blends of unsaturated polyester and polycaprolactone, using FLG and fibreglass reinforcement. The DC and AC electrical conductivities were strongly enhanced by the coupled effect of phase separation and fibre preform, effectively reducing the percolation threshold. An impressive shift was measured from 8.2 wt% of graphene for the neat resin to 1.4 wt% of graphene for the optimized composition. These materials also showed strong strain sensing capabilities at low applied voltage. Therefore, these systems are reliable and cost effective candidates for self-sensing and damage tracking application.

In-situ reactive compatiblization modified poly(l-lactic acid) and poly (butylene adipate-co-terephthalate) blends with improved toughening and thermal characteristics

Triglycidyl isocyanurate (TGIC) with multifunctional epoxy is used for reactive compatibilization of Poly (l-lactic acid) (PLLA)/Poly (butylene adipate-co-terephthalate) (PBAT) blends. Interfacial tension, FTIR and SEM results show that TGIC has greater affinity and stronger reactivity with PBAT. The mixing sequence of PLLA/PBAT/TGIC blends has a significant impact on the compatibility. The TGIC and PBAT are reactive blended first, followed by the PLLA, which is most advantageous to produce a substantial amounts of branched copolymers PLLA-g-PBAT at the interface for the (PBAT/4%T) /PLLA blend. The considerable improvement of interfacial compatibility and the thickening of interfacial layer promote the stress transfer from the matrix to the dispersed PBAT phase. In comparison to PLLA/PBAT blend, the breaking elongation of (PBAT/4%T)/PLLA blend is raised by 25.6 times up to 164.2 % and the tensile strength is enhanced up to 32.1 MPa. The present work offers valuable perspectives on how to encourage the efficient application of reactive compatibilizers with epoxy groups in polyester blends.

The effect of polyethylene glycol sorbitan monostearate on the morphological characteristics and performance of thermoplastic starch/biodegradable polyester blend films

Although thermoplastic starch (TPS) has been developed to mitigate greenhouse gas emissions and environmental and health-related impacts from plastics, high moisture sensitivity and poor mechanical properties limited its practical applications. Blending TPS with biodegradable polyesters, i.e., poly(lactic acid) (PLA) and poly(butylene succinate-co-butylene adipate) (PBSA), is an alternative approach; however, the compatibility among polymer phases needs to be improved. Here, polyethylene glycol sorbitan monostearate (Tween 60), an amphiphilic surfactant, was proposed to improve the compatibility and performance of the TPS/PLA/PBSA 40/30/30 blend. The concentration of Tween 60 varied in the range of 0.5–2.5 wt%. The blends were fabricated using an extruder through two different melt-mixing routes, i.e., direct mixing and masterbatch mixing, and then converted to film using a blown film extrusion line. Tween 60 could improve compatibility between TPS dispersed phase and PLA/PBSA matrix, resulting in increased tensile strength, extensibility, impact strength, thermal stability, and water vapor and oxygen barrier properties of the ternary blend. In addition, better performance of the blend was obtained from the direct mixing route. Tween 60 could thus be considered a potential compatibilizer for the TPS/PLA/PBSA blend film, which can be further used as a biodegradable packaging material.

Degradation of bio-based film plastics in soil under natural conditions

The degradation of bio-based plastic materials in field soil under natural conditions was investigated in this study. Three bio-based plastics materials, which contained polylactide (PLA) with polybutylene adipate terephthalate and additives (PLA_1), PLA-based polyester blend with mineral filler (PLA_2), and polybutylene succinate with mineral filler (PBS_1) in the form of the film, were subjected to soil burial biodegradation processes. The experiments were carried out in a climate with an average annual temperature of 9.4 °C, in winter and summer periods for one year. The degradation of the materials was evaluated by macro- and microscopic observations, weight loss, thermogravimetric analysis, and tensile test. Macroscopic observation indicated that changes in the color of film surface were visible for samples PBS_1 after 12 months of degradation. Using microscopic inspection the erosion of surface samples PLA_1 and PBS_1 after 12 months was observed. Mass loss of samples PLA_1 and PLA_2 after one year of degradation were below 0.6 %. Moreover, for PBS_1 sample, mass loss was equal to 4.3 %. Based on the obtained results of the mass loss, a description of the degradation kinetics was proposed, showing the changes in the thickness of the tested polymer over time. The thermal stability of the samples PLA_1 and PLA_2 decreased during the degradation process by 16.1 and 2.6 °C, respectively, and for PBS_1 increased by 1.7 °C. Tensile strength at break after 12 months of degradation decreased for sample PLA_1 and PLA_2 by 27.3 and 5.8 %, respectively, and increased for sample PBS_1 by 28.2 % compare to unexposed sample.

Green route extraction of TPA monomer from poly cotton fibre: A sustainable recovery approach

Poly-cotton fiber, a blend of polyester and cotton fiber, plays a significant role in the textile industry, with nearly 60% of Poly (ethylene Terephthalate) or PET being utilized for this purpose. However, the effective recovery of PET from textile waste remains a pressing concern, underscoring the importance of adopting greener methods over conventional ones. In this context, phase transfer catalysts have emerged as a promising novel approach in green chemistry. For instance, the use of Tetrabutylammonium bromides as catalysts in the alkaline hydrolysis process facilitates the separation of PET and recovery of TPA with an impressive 95% recovery rate at a relatively low temperature of 100°C. The escalating pace of industrialization coupled with evolving fashion trends has led to a substantial increase in poly-cotton waste generation. Consequently, focusing on the recovery of monomers for reuse not only addresses environmental concerns but also aligns with the fundamental principles of green chemistry, promoting sustainability within the textile sector. Thus, exploring and implementing innovative techniques like phase transfer catalysis can significantly contribute to mitigating environmental impacts while fostering efficient resource utilization in textile production.

Biodegradable polyester blends containing multifunctional substances of plant origin

The research aimed to develop polyester materials based on biodegradable polymers (blends of polylactide PLA and poly(hydroxybutyrate) PHB) with additives of plant origin. Substances such as chlorophyll, -carotene, tannic acid and comparative Magenta KeyplastTM dye have been added as stabilisers and dyes of polymer blends.The samples were subjected to thermooxidation and UV aging. Based on changes in mechanical properties, the ageing coefficients K of the composition were calculated. In addition, the colour change was analysed. Thermal transformations of the samples were also determined by differential scanning calorimetry in order to determine the glass transition temperature, melting and crystallisation of materials, as well as to compare the resistance to thermal oxidation of polymeric composition.Chlorophyll, -carotene and tannic acid increased resistance to thermal oxidation of PLA/PHB blends (higher oxidation temperatures in the DSC analysis, indicating a higher resistance to thermal oxidation). Materials with chlorophyll, -carotene and Magenta organic dye had higher ageing coefficientsand, thus, better resistance to degradation. The sample containing -carotene showed a significant colour change under the influence of heat and UV ageing.Concerned the short ageing time of the samples, which may have been insufficient to analyse the degradation process of polymer compositions and the effects of plant stabilising substances. In the future, the ageing time of materials can be extended, and other types of degrading factors can be used.Practical implications include the possibility of using PLA/PHB blends as packaging materials. Adding substances of plant origin allowed obtaining colorful, visually attractive materials, similar to the Magenta dye dedicated to using in polymers. Moreover, the additives allowed control of the degradability of the samples.The originality of the research was the preparation of PLA/PHB polyester blends with the addition of plant substances as multifunctional agents (stabilisers and dyes).

Evaluation of Air Permeability of Knitted Fabrics at Various Washing Intervals

The air permeability of fabrics is one of the most important factors to be considered in making comfortable clothing for consumers. It helps to transport moisture in the form of vapours from the inner skin to the outer environment. This study aims at determining the rate of airflow through the prepared knitted fabrics after various washing intervals. Circular knitted fabrics with 100% cotton and a blend of cotton and polyester having a ratio of 70% / 30% were made by setting different construction parameters. Prepared fabrics were evaluated for their air permeability by following the ASTM D737-1996 test procedure. Then these fabrics were laundered with standard procedure and evaluated after various intervals. It was concluded from the obtained results that construction parameters such as kind of polymer, loop length, hairiness, yarn count, number and size of pores and their distribution play a major role in determining the air permeability of knitted fabrics. Moreover, an increase in washing cycles also reduces the airflow through the fabric.

Reactive biodegradable extruded blends of thermoplastic starch and polyesters

Poly(butylene succinate) (PBS) and poly(butylene adipate co-terephthalate) (PBAT) are biodegradable polymers applied as alternative materials to non-biodegradable plastics. They have adequate mechanical properties to be used on an industrial scale, but their high cost is a limiting factor. Using thermoplastic starch (TPS) as the main component of the matrix is an alternative to producing low-cost materials. This work aimed to develop PBAT/PBS/TPS biodegradable films by blown extrusion, combining the most attractive properties of each polymer: the ductility of PBAT, the tensile strength of PBS, and the biodegradability and low cost of TPS. PBS/PBAT/TPS (20/10/70 wt%) sample achieved the best balance between hardness, ductility, and strength, with an elongation at break of 32%, a tensile strength of 6 MPa, and Young's modulus (YM) of 56 MPa. Citric acid acted as a multifunctional compound, increasing tensile strength and elongation at break and decreasing YM for all films. It increased the opacity and degree of crystallinity of the films but did not influence the color. FTIR did not indicate chemical reactions between the constituents, and the SEM showed higher compatibility between TPS/PBAT than with PBS. Our work proposed a well-known manufacturing process that allows scaling up the production of biodegradable films.

Controlled curing of resole phenol formaldehyde/unsaturated polyester blends and applying for steel–steel adhesive

AbstractPolymer blending technique is a promising solution for solving some critical industrial problems by gaining new desired properties for the newly formed materials. Blending various ratios of resole phenol formaldehyde (RPF)/unsaturated polyester (USPE), 10, 20, 30, to 90 wt %, were processed to optimize the mixing conditions by controlling time, temperature, and ratio of blending. In addition, the curing conditions of touch dry, full curing, shelf life, hardness and the steel–steel adhesive were investigated. The blend ratio RPF/USPE (70:30) was selected as an optimized sample at 150°C for 50 min. It was characterized by Fourier transform infrared spectroscopy, dynamic mechanical analysis, scanning electron microscopy, X‐ray diffraction, thermogravimetric analysis, and differential scanning calorimeter. The curing process and the interactions between RPF and USPE were studied. Durability with artificial weather aging was evaluated visually and by measuring hardness which confirmed the prepared material is fit for outdoor uses. This work introduces a strategy to control the curing process, enhance the shelf life and adhesion properties for steel–steel adhesives based on RPF/USPE blends.

Ylang-ylang (Cananga odorata) essential oils with flora odorants enhanced active function of biodegradable polyester films produced by extrusion

Ylang-ylang (Cananga odorata) essential oils (EO) has several active components with flora odorants which are compatible with several foods and desserts. Incorporation of Ylang-ylang EO into biodegradable polymers potentially produce functional packaging, releasing desirable aroma which is attractive to consumers. This research aimed to enhance active function of biodegradable polyester blend films namely polybutylene adipate-co-terephthalate (PBAT) and polybutylene succinate (PBS) using cast extrusion with Ylang-ylang EO. Characterizations of the film include morphology, relaxation, infrared absorption and packaging properties. Adding EO gave a smoother microstructure and surface topography and modified the crystal lattice of the PBS phase. Infrared absorption indicated EO-polymer interaction involving C–H stretching vibration. Polymer relaxation influenced transport of gas molecules through PBAT/PBS/EO matrices. Decreased α-relaxation temperature suggested plasticization effects of the amorphous PBAT phase by EO, increasing oxygen and water vapor permeability by 2.52 and 1.16 times, respectively. Polymer relaxation and crystallinity influenced transport of non-polar oxygen through PBAT/PBS/EO matrices. Moreover, films containing EO effectively delayed fungal growth in pandan pudding and layered pudding by more than 3 days due to the release of volatiles that exhibited antifungal activities. Findings suggested potential of Ylang-ylang EO incorporated biodegradable films to produce active packaging for aroma release, extending product shelf-life.

Identification of the fracture surface of thermoset polyester due to bending load

In this research, an attempt was made to improve the brittle nature of the Unsaturated Polyester (UP) polymer which cannot undergo plastic deformation to be improved to become more resilient by adding Thermoset Vinyl Ester and Methyl Methacrylate (MMA). To show the change in the toughness of the polyester material, a test is carried out to provide a tensile load and a flexural load until the material breaks This work reports the successful fabrication of polyester blends by mixing vinyl esters with different percentages. The test shows that there is a linear relationship between the shape of the fracture surface due to bending loads and observations through SEM which are directly related to the flexural stress properties with the fracture surface morphology. The mixture of polyester with 40% vinyl ester showed the highest flexural stress of 126.88 MPa while for pure polyester of 49.71 MPa this showed an increase of 255.24% compared to pure polyester. This shows that the addition of vinyl ester to polyester resulted in an increase in the toughness of the polyester, but for 100% vinyl ester the return stress decreased by 56.50 MPa. This indicates that due to the breaking of some of the polyester chain networks causes a decrease in the structural stiffness, which results in an increase in the plastic deformation zone fraction.