Papers by Keyword: Thermal Properties

Abstract: The objective of this work is to investigate the feasibility of including seaweed filler to enhance the structural properties of PBAT bio-composites. The study involves evaluating the suitability of various applications by conducting assessments of tensile performance, thermal characteristics, and microstructure analysis. In a mini-Rheomixer, different weight percentages (0wt%, 10wt%, 20wt%; 30wt% and 40wt%) seaweed fillers were mixed into a commercial biodegradable poly (butylene adipate-co-terephthalate) (PBAT) matrix to produce bio-composite materials. Using a standard closed-mold hot press, five types of bio-composites were fabricated (PBAT, SW10, SW20, SW30 and SW40). It was observed that the addition of seaweed filler reduced the crystallinity of the bio-composites. The incorporation of seaweed altered the matrix's thermal stability. Furthermore, scanning electron micrographs of fractured surfaces of bio-composites revealed that the seaweed filler adhered more strongly to the PBAT matrix. No interfacial gaps or evidence of particle pullout from the matrix were discovered. The enhanced characteristics of the PBAT/seaweed bio-composites make them suitable for manufacturing pharmaceutical components and medical panels.

Abstract: Thermosetting epoxy polymers are widely employed as matrices for fabricating fibre-reinforced composites due to their exceptional strength and stiffness. However, the inherent brittleness of epoxy and its generally low fracture toughness impose limitations on their utilization in high-end applications. To address this challenge, the incorporation of micro-and nanoscale fillers emerges as a promising strategy for enhancing the durability of epoxy. MXene belonging to a versatile family of 2D transition-metal carbides, carbonitrides, and nitrides, offer superior physical and mechanical characteristics, making them ideal candidates for creating multifunctional polymer nanocomposites. In this study, MXene nanosheets (specifically Ti₃C₂T_x) were introduced at concentrations ranging from 0.1% to 0.5% by weight, and their dispersion in the epoxy-hardener mixture was achieved through ultrasonication. Remarkably, the incorporation of 0.5 wt. % MXene led to an 8°C increase in the glass transition (Tg) temperature and a 5°C elevation in the crystallisation temperature at 0.3 wt. % loadings. However, at higher MXene concentrations, these values exhibited a decrease. Overall, the mechanical characteristics of the nanocomposites demonstrated improvement. This enhancement is attributed to the effective distribution of MXene within the epoxy matrix, contributing to an overall enhancement of the material's properties.

Abstract: Bacterial nanocellulose (BNC) is a natural polymer gel with unique properties that are suitable for developing advanced film applications such as edible coating and packaging. However, transforming BNC gel into a suspension and applying it as a film still lacks knowledge of the condition and method since BNC film performance depends on many parameters caused by the transformation process. This work studied two important primary variables, the number of homogenization cycles and the BNC concentrations, for transforming BNC gel into aqueous suspension using a microfluidizer to homogenize nanofibers and water medium. The BNC films obtained from the suspensions were examined for their properties, i.e., morphology, crystallinity index, optical, thermal, and mechanical properties. The results explored that the number of homogenization cycles had a non-significant impact on the characteristics and properties of BNC suspension and film. A significant improvement in film properties was found when using a higher BNC concentration at 1% w/v compared with 0.5% w/v at the equivalent number of homogenization cycles (40 cycles). The degradation temperature of this film increased by 13%, and Young’s modulus and tensile strength increased more than twice compared with the 0.5% w/v sample, increasing from 0.3 to 0.7 MPa and from 9 to 19 kPa, respectively. This finding would benefit the further development of BNC film for coating and packaging applications.

Abstract: The main aim of the research work is to develop a sustainable vitrimer composite that can be easily recyclable and reusable carbon fibre for secondary applications. Vitrimer materials provide opportunities for recycle thermosets and CFRP composites, however, the retained properties of composite still limit their applications. In this research work, the focus is to investigate material properties of vitamer/carbon fiber composite and the retained properties after recycling of the same. A vitrimer material has been developed using an epoxy (EP) matrix and bio-based curing agent and citric acid (CA), and finally reinforced with carbon fibre. The vitrimer materials were prepared with varying ratios of acid to the epoxy ratio between 0.30 and 0.40 to prepare the best performance vitrimer. Fourier transform infrared (FTIR) spectrometry was conducted in Transmittance mode over a range of wavelengths from 400 to 4000 cm^-1. The mechanical testing carried out at room temperature under tensile loading. Results found that the Vitrimer composite could be effectively dissolved in DMF, enabling the recovery of the carbon fibers. The results of the study indicate that the EP/CA vitrimers exhibit thermomechanical properties that are comparable to those of the epoxy vitrimer cured using a petroleum-based curing agent. The most important results that demonstrate the use of EP/CA vitrimers may be a promising alternative to traditional epoxy composites in various applications.

Abstract: The current study proposes to investigate the thermal, wettability and mechanical properties of a low temperature SnBi solder. The main aim is to investigate the performance of the SnBi solder alloy with different Bi composition. The study also establishes the relationship between melting temperature, spreading area and tensile stress of the SnBi with different Bi composition at different low reflow temperatures. The thermal and wettability tests are conducted experimentally, while the mechanical test will be analysed via finite element analyses (FEA). The single shear lap test method was adopted for the simulation. The thermal properties of the SnBi solder are investigated using the differential scanning calorimeter (DSC). The reflow temperature selected ranges from 160 °C to 220 °C to accommodate the purpose of low temperature soldering. Wetting test results showed that spreading area of Sn48Bi solder alloy increased to 28.1 and 42.88 at 180 °C and 210 °C respectively. The increase in the Bi composition reduced the tensile strength regardless of the increase of the reflow temperature. The preliminary results commend the characteristics of the SnBi solder as a possible alternative to the Pb solder.

Abstract: Natural fibers have garnered considerable attention from researchers and academics alike due to their eco-friendly nature and sustainability. These fibers are being explored for their potential use in polymer composites. The use of natural fiber-reinforced polymer composite materials is rapidly increasing in both industrial and fundamental research applications due to their renewable, low, and biodegradable properties. In order to reduce the CO₂ emissions, the building energy consumption and preserve the natural sand. The present study involved conducting an analysis of the results obtained from the experimental investigation where five mixtures of typha fiber sand, and cement (MHC0, MHC5, MHC10, MHC15 and MHC20)) were utilized to make Typha-concrete. The experimental mixtures being examined and the results indicate that the density of the samples diminishes in proportion to the incorporation of typha fiber, while the thermal conductivity is enhanced. In addition, the characteristics of lightweight structures can be attributed to the generated specimens, which have been determined by their documented compressive strength. Based on the results of RILEM's functional classification analysis, it can be concluded that Typha-concrete meets the mechanical and thermal requirements of construction materials, making it a feasible option for both structural and insulating concrete applications.

Abstract: An experimental study was carried out to evaluate the feasibility of using concrete compositions containing waste wood for structural and non-structural building applications. First, the inert and wood aggregates used in the composite design were characterized. Five compositions containing a reference, 50% and 100% of wood particles were then produced and characterized in terms of physical and mechanical performance (e.g., apparent density, abrasion, compressive strength, and flexural strength). The selected specimens were used for additional experimental tests. These included water absorption and thermal tests. Increasing wood waste content considerably lower compressive and flexural strengths while improving the thermal insulation quality of wood waste-cement composite. The durability assessment of selected compositions further showed that the abrasion resistance of manufactured specimen decreased by adding wood waste in the cement matrix while there was an increase of the capillarity absorption coefficients. It appears that the incorporation of waste wood particles into mortars decrease their thermal conductivities to 0.3 W/mK. The use of wood waste treated by a lime solution improves the studied properties.

Abstract: This research paper investigates the effect of the addition of carbon nanotubes (0.5 and 1.0% by weight) on crystallisation procedure in isotactic polypropylene. The study found that the crystallisation temperature increased with increasing nanotube content, while the crystallisation of polymers did not substantially change. The critical cooling speed, at which PP does not crystalize, increases with the increase in carbon nanotube content. Using the critical cooling speed and nanotube content, a nucleation effectiveness parameter was developed, that is not dependent on the crystallisation temperature or the CNT load. The study also found that carbon nanotubes only speed up the development of α-phase in isothermal crystallisation experiments. The control fibers had a shrinkage of 27% to 160°C, while the shrinkage of the composite fibers was less than 5%. The melting temperature of PP and its nanocomposites was approximately 150 to 152°C. However, the values for the degree of crystallinity of the nanocomposites rose along with the CNT content.

Abstract: Virgin high-density polyethylene (vHDPE), recycled (rHDPE), and mixed vHDPE/rHDPE matrices and wood plastic composites based on these mixtures + 50 wt.% of plywood sanding dust (PSD) and 3 wt.% coupling agent maleated polyethylene (MAPE) physical-mechanical properties (tensile, flexural strength and modulus, impact strength, and microhardness) were investigated. It was observed that all defined properties depend on the content of rHDPE in the pure polymer matrix and corresponding WPCs. Tensile strength and modulus decreased a bit, but flexural modulus actually had no changes. At the same time, a decrease in impact strength and a significant increase (up to 2 times) in microhardness are observed. From all the investigated matrices, the most perspective seems to be the matrix with a vHDPE/rHDPE ratio of 75/25, whose mechanical properties are acceptable for the preparation of the WPCs based on plywood sanding dust. The compatibilization possibilities tests of different mixed matrices done by the DSC method in the air showed that the mixed vHDPE/rHDPE compositions compatibility is sufficiently good at different proportions. For all mixed matrices, only one relatively symmetric band with one peak of melting was observed. Differential scanning calorimetry (DSC) tests in an inert environment showed that during the first heating cycle, HDPE components are only partially compatible (two peaks of melting temperatures are possible to fix). On the contrary, after the cooling and crystallization processes, during the second heating of the same sample, these two bands completely merge, and like in the air, only one maximum melting temperature peak was observed. The values of thermal oxidation temperature and melting temperature are the highest for virgin vHDPE but the lowest for rHDPE. The values of all corresponding parameters of mixed matrices reduce proportionally with an increase in rHDPE content in the mixtures.

Abstract: Magnesium alloys are highly desirable for weight critical applications owing to their high weight to strangth ratio. However, their poor formability at room temperature limits their widespread use in industrial applications. In this study, we invstigate the hot deformation behaviour of AZ31 and AZ31-0.7% Ca magnesium alloys and explore their microstructural and thermal properties. Our findings reveal that dynamic recrystallization during hot deformation leads to successful grain refinement in the AZ31 alloy, resulting in a normal grain size distribution. In contrast, the AZ31-0.7% Ca alloy shows bimodal grain size distribution due to the addition of calcium. Additionally, the number and size of β-Mg₁₇Al₁₂ particles were found to increase with the addition of a small amount of calcium. These particles are responsible for the discontinuous precipitation phenomenon, which strongly influences microstructural changes during hot rolling. Our study provides valuable insights into the dynamic recrystallization and discontinuous precipitation phenomena of magnesium alloys, which can aid in the development of novel alloys with improved formability and mechanical properties.