Resin Blends Research Articles

Mechanical and Structural Properties of Polyhydroxybutyrate as Additive in Blend Material in Additive Manufacturing for Medical Applications.

Today, additive manufacturing (AM) is considered one of the vital tenets of the industry 4.0 revolution due to its high productivity, decentralized production and rapid prototyping. This work aims to study the mechanical and structural properties of polyhydroxybutyrate as an additive in blend materials and its potential in medical applications. PHB/PUA blend resins were formulated with 0 wt.%, 6 wt.%, 12 wt.% and 18 wt.% of PHB concentration. Stereolithography or an SLA 3D printing technique were used to evaluate the printability of the PHB/PUA blend resins. Additionally, from FESEM analysis, a change was observed in PUA's microstructure, with an additional number of voids spotted. Furthermore, from XRD analysis, as PHB concentration increased, the crystallinity index (CI) also increased. This indicates the brittleness properties of the materials, which correlated to the weak performance of the tensile and impact properties. Next, the effect of PHB loading concentration within PHB/PUA blends and aging duration towards the mechanical performance of tensile and impact properties was also studied by using analysis of variance (ANOVA) with a two-way method. Finally, 12 wt.% of PHB/PUA was selected to 3D print the finger splint due to its characteristics, which are compatible to be used in finger bone fracture recovery.

Optimization of PET Particle-Reinforced Epoxy Resin Composite for Eco-Brick Application Using the Response Surface Methodology

Brick is a common building material that is used in society for constructing buildings. A viable environmental strategy to lessen the amount of plastic waste involves the inclusion of plastic trash in building materials. Globally, there is a severe issue with the disposal of plastic garbage in landfills. The primary and secondary carbon bonds that are formed in plastic packaging wastes can severely contaminate the environment. Hence, managing plastic waste to generate new and useful items is essential. One of the most practical ways to safeguard the environment is to manufacture eco-bricks from PET waste and epoxy resin. Additionally, as there is no combustion involved in the production of this eco-brick; it does not harm the environment. Eco-brick can be defined as a novel concept and approach to waste management and recycling. Eco-bricks have many advantages, such as easy availability and being environmentally friendly. This study aimed to improve the composition of the eco-brick using a mixture of epoxy resin and PET particles. In this study, a mathematical modelling technique called the Response Surface Method (RSM) was designed using the Central Composite Design (CCD). Variable input factors were used to develop eco-bricks such as mixture ratio (10–90%), particle size (1–5 mm), and drying time (1–7 days), whereas the variable response included the compressive strength. The complete experimental design was developed using Design Expert 11 software, and simulation experiments with 17 sets of parameters were generated. The microstructural characteristics of the eco-brick were examined using SEM. The results of the experiments indicated that the most optimised parameters that could be used for eco-brick application were: a PET particle size of 1.1 mm, a mixing ratio of 89.9%, and a curing time of 6.9 days. Earlier research that was conducted regarding the production of eco-bricks using a PET particle and epoxy resin mixture showed that these materials had a high potential to boost compressive strength. The quadratic model was used as the basis for the regression analysis for generating the response equations. Since the difference between the experimental and anticipated values was less than 5%, it was concluded that the results of the experimental and predictive tests showed good agreement. The model used in this study yielded noteworthy outcomes. As a result, the suggested statistical model can offer a clear understanding of designing experiments and variables that affect the production of eco-brick using a blend of PET particles and epoxy resin.

Intelligent Eucommia ulmoides Rubber/Ionomer Blends with Thermally Activated Shape Memory and Self-Healing Properties.

Intelligent Eucommia ulmoides rubber (EUR) and ionomer Surlyn resin (SR) blends were prepared and studied in this manuscript. This is the first paper to combine EUR with SR to prepare blends with both the shape memory effect and self-healing capability. The mechanical, curing, thermal, shape memory and self-healing properties were studied by a universal testing machine, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), respectively. Experimental results showed that the increase in ionomer content not only improved mechanical and shape memory properties but also endowed the compounds with excellent self-healing ability under the appropriate environmental conditions. Notably, the self-healing efficiency of the composites reached 87.41%, which is much higher than the efficiency of other covalent cross-linking composites. Therefore, these novel shape memory and self-healing blends can expand the use of natural Eucommia ulmoides rubber, such as in special medical devices, sensors and actuators.

Sustainable production of recycled rubber waste composites with various epoxy systems: A comparative study on mechanical and thermal properties

In this study, ethylene-propylene-diene monomer rubber (EPDM) and tire waste powder (TW) were selected as filling materials for toughening various epoxy matrices, lowering composite materials costs and converting these wastes into valuable resources. Two types of bisphenol-A epoxy resins (ER1 and ER1diluted), and three types of epoxy resin blend systems with ER1diluted, CTBN rubber modified (ER2), and polyurethane modified (ER3) epoxies in 1:1 wt ratio were used as matrices. The effects of the rubber ratio and type, also the epoxy matrix on the composite properties were investigated. The TW composites' mechanical and thermal properties were higher than those of the EPDM composites. The best results for resin mixtures were obtained with ER3. The most suitable filling ratio of EPDM and TW varied between 20% and 30% by weight, depending on the matrix type. TW addition increased the impact strength of the ER1diluted and ER3-ER1diluted epoxy matrices. In terms of mechanical properties, the low ambient temperature was found to be more suitable than an aqueous medium.

Synthesis and optimization for shape memory behaviour of 4D printed GNPs reinforced shape memory photopolymer composite

PurposeShape memory materials are functional materials having a good number of applications due to their unique features of programmable material technology such as self-stretching, self-assembly and self-tightening. Advancements in today’s technology led to the easy fabrication of such novel materials using 3D printing techniques. When an external stimulus causes a 3D printed specimen to change shape on its own, this process is known as 4D printing. This study aims to investigate the effect of graphene nano platelet (GNPs) on the shape memory behaviour of shape memory photo polymer composites (SMPPCs) and to optimize the shape-changing response by using the Taguchi method.Design/methodology/approachSMPPCs are synthesized by blending different weight fractions (Wt.%) of flexible or soft photopolymer (FPP) resin with hard photopolymer (HPP) resin, then reinforced with GNPs at various Wt.% to the blended PP resin, and then fabricated using masked stereolithography (MSLA) apparatus. The shape memory test is conducted to assess the shape recovery time (T), shape fixity ratio (Rf), shape recovery ratio (Rr) and shape recovery rate (Vr) using Taguchi analysis by constructing an L9 orthogonal array with parameters such as Wt.% of a blend of FPP and HPP resin, Wt.% of GNPs and holding time.FindingsSMPPCs with A3, B3 and C2 result in a faster T with 2 s, whereas SMPPCs with A1, B1 and C3 result in a longer T with 21 s. The factors A and B are ranked as the most significant in the Pareto charts that were obtained, whereas C is not significant. It can be seen from the heatmap plot that when factors A and B increase, T is decreasing and Vr is increasing. The optimum parameters for T and Vr are A3, B3 and C2 at the same time for Rf and Rr are A1, B3 and C1.Research limitations/implicationsFaster shape recovery results from a higher Wt.% of FPP resin in a blend than over a true HPP resin. This is because the flexible polymer links in FPP resin activate more quickly over time. However, a minimum amount of HPP resin also needs to be maintained because it plays a role in producing higher Rf and Vr. The use of GNPs as reinforcement accelerates the T because nanographene conducts heat more quickly, releasing the temporary shape of the specimen more quickly.Originality/valueThe use of FPP and HPP resin blends, fabricating the 4D-printed SMPPCs specimens with MSLA technology, investigating the effect of GNPs and optimizing the process parameters using Taguchi and the work was validated using confirmation tests and regression analysis, which increases the originality and novelty.

Effect of GNPs and resin blend on tear resistance of 4D printed shape memory photopolymer composite

PurposeThe tear strength (Ts) is a significant property for any kind of soft polymeric material such as rubber, elastomer, viscoelastic material and its composites, to quantify the suitability of a material for any shape memory applications. Many times, the soft elastomeric polymer material has to be capable enough to deform to a maximum extent of displacement but at the same time, it has to withstand the maximum load without fail. Along with shape recovery properties (i.e. the ability to recover its shape from programmed to the original), the success of the shape memory cycle is mainly depending on its stiffness and strength. It has to resist tear during stretching (i.e. programming stage) as repeatedly subjected to deformation, and, hence, it is important to study the tear behaviour for shape memory polymers (SMPs) and their composites. The purpose of the work is to investigate the effect of parameters on Ts of 4D printed specimen using Taguchi method.Design/methodology/approachThe objective of the work is to tailor the Ts of SMPs by reinforcing the graphene nano particles (GNPs) in a blended photopolymer (PP) resin with flexible PP and hard PP resin. In this study, a total of nine experiments were designed based on the L9 orthogonal array (OA) using the design of experiments (DOEs). All the shape memory photopolymer composite’s (SMPPCs) specimens are fabricated using masked stereolithography (MSLA), also known as resin three-dimensional printing (R3DP) technique.FindingsSpecimens are tested using universal testing machine (UTM) for maximum tear force (Fmax) and displacement (δ) caused by tearing the specimen to evaluate the strength against the tear. The results showed that the Wt.% of resin blend highly influenced both Fmax and δ, while GNPs also had an impact on δ. The specimens are offering more tear resistance for those specimens blended with less Wt.% of flexible PP at the same time the specimens enable more δ for those specimens reinforced with 0.3 Wt.% GNPs at 10-s exposure time. The optimum combinations are A1, B1 and C3 for the Fmax and Ts and at the same time A1, B3 and C3 for δ.Research limitations/implicationsTo customise the tear resistance of SMPPCs using MSLA 3 D printing, this study suggested a blend of PP resins reinforced with GNPs. This opens up a new path for creating novel, inexpensive multi-functional 4-dimensional (4D) printed parts.Originality/valueThe use of flexible PP and hard PP resin blends, fabricating the SMPPCs specimens using 3 D printed MSLA technology, investigating the effect of GNPs, resin blend and exposure time, optimizing the process parameters using Taguchi and the work were all validated using confirmation tests and regression analysis using test train method, which increases the originality and novelty.

High-performance thermosets for additive manufacturing

Additive manufacturing (AM) has come a long way since its initial inception. Previously considered a fast prototyping method, it offers significant benefits for use as a method of producing user-end parts that are limited in quantity, customizable, and/or complicated geometries. For AM to be considered in high-performance applications, such as automotive and aerospace, we must consider AM technology and the available and compatible printing materials. Typically only thermoset plastic resins are capable of meeting high-performance specifications, such as sufficiently high strength, stiffness, and toughness, as well as excellent chemical and environmental resistance. This review presents a broad overview of the available high-performance thermoset chemistries and formulations, i.e., resin blends. The base resin chemistries that are covered are: vinyl, epoxy, imides, cyanate ester, urethanes, benzoxazine, and click chemistries (e.g., Michael addition). Subsequently, more application-relevant blends of these base resins are discussed. Each section focuses on resin details such as reaction mechanisms, typical monomer structure, mechanical properties, and applications specific to AM. The review is organized as follows. We begin with an introduction on the state-of-the-art, the challenges still faced by the field, and a benchmark definition of “high performance.” This is followed by a discussion of the available AM technologies for thermoset printing, with a focus on their advantages and disadvantages. Next, we cover the details of different resin chemistry, followed by their blends. The following section details the difficulties in developing AM technologies that allow for the incorporation of fillers, such as rheological modifiers and reinforcements. The review ends with a perspective on the future of AM technologies that would bridge the gap between pure resin printing and the much needed composite printing for high-performance applications.

Miscibility and Optimization of the Liquid Rubber Content in the Resins of Light-Cured Dental Composites

Fracture toughness is one of the main factors influencing the durability of light-cured composites used for dental restorations and fillings. One of the methods of increasing the fracture toughness is the modification of the matrix with liquid acrylonitrile-free liquid rubber. This study aimed to assess the miscibility of acrylonitrile-free liquid rubber with a blend of resins and their stability over time, and to determine the optimal amount of liquid rubber (LR) in the blend due to mechanical properties. Two blends of dimethacrylate resins were used: resin "F" composed of BisGMA (60 wt.%), TEGDMA (20 wt.%), BisEMA (10 wt.%) and UDMA (10 wt.%), and "C" resin containing BisGMA (40 wt.%), TEGDMA (40 wt.%), BisEMA (10 wt.%) and UDMA (10 wt.%). The modifier Hypro® 2000X168LC VTB liquid rubber was used in at 1%, 2%, 3%, 4%, 5%, 10%, 15% and 20% by weight in the resin blend. The miscibility was assessed by microscopy. The fracture toughness, flexural strength and Young's modulus were determined in the bending test. The results showed that the solubility of the liquid rubber depends on the ratio of BisGMA/TEGDMA in the resins. In resins with 40 wt.% TEGDMA, the LR solubility was as high as 5%, while resins with 20 wt.% TEGDMA, the liquid rubber did not dissolve. The LR-resin mixtures showed good time stability, and no changes in the size or morphology of the rubber domains were found after 24 h of mixing. The maximum fracture toughness (2.46 MPa m1/2) was obtained for 5 wt.% LR in resin F and for 15 wt.% LR in resin C (2.53 MPa m1/2). The modification with liquid rubber resulted in an exponential reduction in both flexural strength and Young's modulus. The analysis of the results of the mechanical tests allowed us to determine the optimal amount of LR for both resins. For resin F it was 5.4 wt.%, and for resin C it was 8.3 wt.%. It can be stated that the optimal amount of liquid rubber increases with its solubility in the resin.

True Molecular Composites: Unusual Structure and Properties of PDMS-MQ Resin Blends

Poly(dimethyl siloxane)-MQ rubber molecular composites are easy to prepare, as it does not require a heterophase mixing of ingredients. They are characterized by perfect homogeneity, so they are very promising as rubber materials with controllable functional characteristics. The manuscript reveals that MQ resin particles can significantly, more than by two orders of magnitude, enhance the mechanical properties of poly(dimethyl siloxane), and, as fillers, they are not inferior to aerosils. In the produced materials, MQ particles play a role of the molecular entanglements, so rubber molecular weight and MQ filler concentration are the parameters determining the structure and properties of such composites. Moreover, a need for a saturation of the reactive groups and minimization of the surface energy of MQ particles also determine the size and distribution of the filler at different filler rates. An unusual correlation of the concentration of MQ component and the interparticle spacing was revealed. Based on the extraordinary mechanical properties and structure features, a model of the structure poly(dimethyl siloxane)-rubber molecular composites and of its evolution in the process of stretching, was proposed.

Pengaruh nilai K-value dan Penambahan Filler terhadap Kualitas Kulit Sintetis berbasis Polivinil Klorida

Synthetic leather is generally made using polyvinyl chloride or polyurethane resins by coating method. The balance between quality and production costs of the final product is influenced by the selection of the right material composition. Polyvinyl chloride resins are available in a variety of k-values, while fillers are often added to modify mechanical characteristics and lower the costs. The aim of this study was to examine the effect of the k-value of polyvinyl chloride blend and the amount of filler on the quality of synthetic leather. Plastisol is prepared by mixing resin, primary plasticizer, secondary plasticizer, and stabilizer according to the formulation. PVC resin blend with different k-values and certain amount of filler (10, 20, 30 and 40 phr) were used. The quality of the samples was tested using adhesion strength, tensile strength, and elongation at break testing according to ASTM D751-06. The results showed that resins blend with different k-values could be used to obtain the desired quality. The value of the adhesion strength, tensile strength and elongation at break will approach the characteristics of the larger part of the resin. The homogeneity of plastisol because of resin blend also needs attention, especially if the k-value difference between two resin is too large. Meanwhile, the use of calcium carbonate as filler in general will reduce the test results obtained.

Investigation of the modes of action for phosphorous flame retardants in a fully waterborne sugar-based epoxy resin

A fully waterborne epoxy system was prepared from waterborne sorbitol-based epoxy resin cured with an alkylated polyalkylene polyamine hardener. The flame-retardant property was accomplished by the application of different additive phosphorous flame retardants (FRs). Phosphonate polyol and ethyl ethylene glycol phosphate which are in the liquid phase, and two FRs in the form of fine-grained particles; aluminium diethyl phosphinate (AlPi), ammonium polyphosphate (APP). The flame-retardant epoxy resin blends were prepared at the same levels of phosphorus content. The results are very promising as the self-extinguishing behaviour was observed at 3%P for all the investigated FRs and at 1%P in the case of APP. Limiting oxygen index (LOI) values were practically good for all FRs and extremely improved in the case of APP. LOI was 48% for the APP sample at 3%P content. Furthermore, this blend showed the best results in the forced flaming conditions as the total heat release in cone calorimetry measurements (THR) decreased by 43% and the peak of heat release rate (pHRR) decreased by 65% with more elongated burning compared to the reference SPE matrix. The efficient solid-phase FR effect of APP was confirmed by scanning electron microscopic (SEM) and attenuated total reflection-infrared spectrometry (ATR-IR) analysis of the residual char after cone calorimetry measurements.

Thermal Stability, Flammability and Mechanical Performances of Unsaturated Polyester-Melamine Resin Blends and of Glass Fibre-Reinforced Composites Based on Them.

A novel blend of unsaturated polyester (UP) resin with an inherently flame-retardant and char-forming melamine formaldehyde (MF) resin has been prepared with the aim of reducing the flammability of the former. MF resin, sourced as a spray-dried resin, was dissolved in diethyleneglycol solvent; the dissolved resin and the UP-MF blend were autocured by heating under conditions normally used for curing UP, i.e., room temperature for 24 h and post-curing at 80 °C for 12-24 h. The cured UP-MF blends, although heterogeneous in nature, were rigid materials having fire performances superior to those of the cured UP alone. The blends also burned, but with a much reduced smoke output compared with that from UP. Although the heterogeneity of the blends helped in improving the fire performances of the blends in terms of the MF domains forming a semi-protective char, acting as thermal barriers for the adjoining UP domains, and hence reducing their thermal degradation, the mechanical properties of composites based on them were impaired. Nevertheless, whilst UP/MF blends may not be suitable for use as matrices in glass-reinforced composites in load-bearing applications, they may lend themselves to applications as fire-retardant gel coats, especially in view of their low-smoke, char-forming attributes.

Studies on the reactivity of epoxy/polyol/isocyanate blend resins and the properties of epoxy/polyurethane composites

AbstractEpoxy resin (ER) is one of the most widely used synthetic resins, and the improvement of its toughness is an important issue. In this study, Epon 828 is used as ER resin, polytetramethylene ether glycol (PTMG) and liquefied wood (LW) are used as polyol, and IPDI, H12‐MDI, Desmodur N, and Desmodur L are used as isocyanate. The influence of polyurethane resin (PU) composition on the reactivity of ER/polyol/isocyanate blended resin and the properties of ER/PU composite are investigated. The results show that the mixture of ER/PTMG/IPDI has greater reactivity, followed by ER/PTMG/Desmodur N, while ER/PTMG/Desmodur L has lower reactivity. In the structure of ER/PU blended resin composites, ER and PU resins not only form a physical interpenetrating structure, but also undergo a copolymerization crosslinking reaction. The modulus of elasticity of ER/PU composites prepared with trifunctional Desmodur L and Desmodur N is greater than that of bifunctional IPDI and H12‐MDI, while those with LW as polyol is greater than that of PTMG as the raw material.

Preparation and Properties of Epoxy Resin and Polyurethane Blend Resin-Based Low-Infrared-Emissivity Coatings

A low-infrared-emissivity composite coating with outstanding mechanical properties and low glossiness was prepared by using an epoxy resin and polyurethane blend modified resin, flake brass powder, the silane coupling agent KH560, and a dispersant as an adhesive, a functional pigment, and interface modifiers, respectively. The effects of the mass ratios of epoxy resin and polyurethane, the addition amount of flake brass powder, the addition amount of KH560, and the addition amount of dispersant on the coating performance were systematically discussed. The results show that the coating has lower emissivity (0.424) and glossiness (28.8) when the mass ratio of epoxy resin to polyurethane is 6:4 and the addition amount of brass powder is 50 wt%. Using KH560 to modify the interface structure of the coating, KH560 can form chemical bond with the resin matrix and flake brass powder so as to obviously improve the impact strength and flexibility of the coating. The addition of the dispersant can obviously enhance the dispersion state of the flake brass powder in the coating and thus enhance the reflection intensity of infrared light for the coating, such that the emissivity of the coating is obviously reduced. When the addition amount of KH560 is 7 wt% and the addition amount of the dispersant is 9 wt%, the coating has the optimal emissivity (0.332), glossiness (9.0), adhesion strength (grade 1), impact strength (50 kg·cm), and flexibility (1 mm) at the same time. The above mentioned low-infrared-emissivity coating has an important application prospect in the field of infrared stealth for various aircraft.

TEGDMA-Functionalized Dicalcium Phosphate Dihydrate Resin-Based Composites Prevent Secondary Caries in an In Vitro Biofilm Model.

This study evaluated the efficacy of experimental TEGDMA-functionalized dicalcium phosphate dihydrate (T-DCPD) filler-based resin-based composites (RBC) in preventing caries lesions around the restoration margins (secondary caries, SC). Standardized Class-II cavities were made in sound molars with the cervical margin in dentin. Cavities were filled with a commercial resin-modified glass-ionomer cement (RMGIC) or experimental RBCs containing a bisGMA-TEGDMA resin blend and one of the following inorganic fractions: 60 wt.% Ba glass (RBC-0); 40 wt.% Ba glass and 20 wt.% T-DCPD (RBC-20); or 20 wt.% Ba glass and 40 wt.% T-DCPD (RBC-40). An open-system bioreactor produced Streptococcus mutans biofilm-driven SC. Specimens were scanned using micro-CT to evaluate demineralization depths. Scanning electron microscopy and energy-dispersive X-ray spectroscopy characterized the specimen surfaces, and antimicrobial activity, buffering effect, and ion uptake by the biofilms were also evaluated. ANOVA and Tukey's tests were applied at p < 0.05. RBC-0 and RBC-20 showed SC development in dentin, while RBC-40 and RMGIC significantly reduced the lesion depth at the restoration margin (p < 0.0001). Initial enamel demineralization could be observed only around the RBC-0 and RBC-20 restorations. Direct antibiofilm activity can explain SC reduction by RMGIC, whereas a buffering effect on the acidogenicity of biofilm can explain the behavior of RBC-40. Experimental RBC with CaP-releasing functionalized T-DCPD filler could prevent SC with the same efficacy as F-releasing materials.

Mechanical properties of epoxy resin toughened with cornstarch

Abstract We investigated the effect of starch modification on the mechanical properties of phenolic epoxy resin (EP). Corn starch admixture of 2.5, 5, 7.5, and 10 wt% were added into the EP. The tensile strength, elongation at break, and elastic modulus of different corn starch contents were compared. The containing of corn starch showed a positive effect on the toughness of the epoxy but showed little effect on strength when the additive content was less than 10 wt%. The strength and elastic modulus increased first and then decreased with the increase in starch content and reached their maximum values at a content of 2.5 wt%. The enhancement effect might be due to corn starch’s mechanical properties, dispersibility, and interfacial interaction. With the increase in starch content, starch granules quickly contact each other, causing self-aggregation sedimentation and a decrease in strength and elastic modulus. The scanning electron micrographs of the toughened EP specimens showed ductile failure because of the starch particles. The surface morphology of the blend resin specimens was full of staggered and stepped cracks caused by the shearing damage, which is shown by obvious plastic fracture characteristics with plastic deformation ability. The initiation of micro-cracks in the EP matrix was induced by the incorporation of starch particles, which caused localized stepped shear damage in the matrix. More energy would be absorbed during this process, and the toughness of the EP would be enhanced. It is recommended that the best corn starch content should be 2.5 wt% to obtain excellent strength and good toughness.

The 3D Printability and Mechanical Properties of Polyhydroxybutyrate (PHB) as Additives in Urethane Dimethacrylate (UDMA) Blends Polymer for Medical Application.

The integration of additive manufacturing (3D printing) in the biomedical sector required material to portray a holistic characteristic in terms of printability, biocompatibility, degradability, and mechanical properties. This research aims to evaluate the 3D printability and mechanical properties of polyhydroxybutyrate (PHB) as additives in the urethane dimethacrylate (UDMA) based resin and its potential for medical applications. The printability of the PHB/UDMA resin blends was limited to 11 wt.% as it reached the maximum viscosity value at 2188 cP. Two-way analysis of variance (ANOVA) was also conducted to assess the significant effect of the varied PHB (wt.%) incorporation within UDMA resin, and the aging duration of 3D printed PHB/UDMA on mechanical properties in terms of tensile and impact properties. Meanwhile, the increasing crystallinity index (CI) of X-ray diffraction (XRD) in the 3D printed PHB/UDMA as the PHB loading increased, indicating that there is a strong correlation with the lower tensile and impact strength. FESEM images also proved that the agglomerations that occurred within the UDMA matrix had affected the mechanical performance of 3D printed PHB/UDMA. Nonetheless, the thermal stability of the 3D printed PHB/UDMA had only a slight deviation from the 3D printed UDMA since it had better thermal processability.

Mechanical properties of unsaturated polyester/epoxidized palm oil/Kenaf fibre composite at different styrene content

Polyester resin (UPE) is petroleum-based polymer that most generally utilized as matrix system in fibre-reinforced plastic (FRP) products due to its high properties per price ratio. Currently, researchers are interested in partial blends of UPE resin with vegetable oil reinforced with natural fibre to produce renewable and sustainable composite products. However, the mechanical properties of this new blending bio-composite are highly related to the curing and crosslinking process of the UPE resin; which contributed by the styrene concentration as the crosslinking agent. Thus, this research aims to investigate the effect of styrene contents on the mechanical and thermal properties of unsaturated polyester (UPE)/epoxidized palm oil (EPO)/kenaf composites. The kenaf fibres were initially treated with an alkaline solution, and the composites were prepared by the direct mixing method and fabricated by hand lay-up technique. In this research, the amount of EPO and styrene varied at 0, 10, 20, 30 wt% and 25, 35, and 45 %, respectively. The characterization of found that increasing styrene content in UPE/EPO/kenaf composites improved the crosslinking and chemical interactions in the composites. In addition, increasing styrene content also improved the tensile modulus, tensile strength, Izod impact strength and elongation at break of the UPE/EPO/kenaf composites.

The antimicrobial, physical, and chemical properties of a riboflavin-loaded dental resin intended for antimicrobial photodynamic therapy

BackgroundDental caries remain a significant global health challenge. Unfortunately, current dental materials lack sufficient antimicrobial power to address the pathogenic species involved in this disease. In this study the potential to load a dental resin blend (RB) with riboflavin (B2) for use in an antimicrobial photodynamic therapy (aPDT) approach was investigated. MethodsB2 was added to our experimental RB (0.1 - 10 wt%). Upon investigating the degree of conversion and specimen integrity of the RB as a function of B2 concentration, it was determined that loading should be restricted to 0.1, 1.0, and 1.5 wt%. Subsequent investigation included water sorption (WS) and solubility (SL), as well as shear bond strength (SBS) and flexural strength (FS) of the specimens after 24 h and 28-day water storage. Lastly, the antimicrobial response of Streptococcus mutans (S. mutans) biofilm following 6 h growth and 60 s of blue LED light (1.3 J/cm2) in an aPDT-based approach was measured. Results and conclusionsAdding up to 1.5 wt% B2 had minimal impact on the FS or SBS of the RB. However, aging for 28-days notably increased the FS by as much as 50% for the 1.5 wt% B2-loaded RB. In addition, adding 1.5 wt% B2 resulted in a significant reduction in WS/SL of the RB. Lastly, while adding B2 did not change the antimicrobial response, this was an initial study under these conditions and future investigation will seek to optimize light parameters to produce a more agonistic response. Overall, a riboflavin-loaded dental resin shows significant promise for utilization in restorative dentistry with aPDT.

Preparation, characterization, and curing kinetics of elevated and cryogenic temperature-resistant epoxy resin composites

The elevated-and-cryogenic temperature resisting composites were prepared using tetrafunctional (AG-80) and bifunctional (E-42) epoxy resin blend as the matrix, polyetheramine (D400), and m-xylylene diamine (MXDA) as hybrid curing agents, silane coupling agent (KH-560) as a toughening agent, and micron-sized silicon oxide particles as fillers. The curing kinetics of the composites was investigated by differential scanning calorimetry (DSC), the effect of reaction temperature on the resin system's viscosity, the variation of gel time with temperature, and the heat resistance of the resin system were tested by thermogravimetric analysis. The apparent activation energy and reaction level of the curing reaction was calculated, the curing process was developed, and the elevated and cryogenic mechanical properties set at different times were tested. The results showed that the resin system's viscosity decreased with increasing temperature, 40 °C was determined as the optimum operating temperature, and the heat resistance of the composite was good. The gel time test developed a strategy of pre-curing by vacuum at 40 °C and curing at 60 °C. The compressive strength of the resin system was 99.55 MPa and 159.12 MPa after placing at −196 °C and 160 °C for 4 h, respectively. This study presents a theoretical basis for the curing process and optimization of curing parameters for elevated and cryogenic resistant modified epoxy resin composite and provides a potential application for its future in-situ utilization in deep space exploration and lunar construction.