Hand Mixing Research Articles

Properties of polyurethane foam/natural fibre composite for air conditioning insulation

ABSTRACT This study focuses on the fabrication of a biocomposite with insulating properties suitable for application in refrigeration pipe systems. The objective of this study was to utilise coconut husk and rice husk in a 1:1 ratio as reinforcement for flexible polyurethane foam. Biocomposites were made using hand mixing and casting technique reinforcement ratios of 5%, 10%, 15%, 20%, and 25% weight ratios from reinforcement husks. A thermal resistivity test, along with tensile test and water absorption measurements as a function of fibre content, was conducted according to ASTM standards. The study demonstrated that incorporating coconut and rice husks as reinforcement in polyurethane foam significantly improved the tensile properties of the composite material. The composite reinforced with 25% weight has been found to have highest tensile stress. In contrast, the thermal resistivity is observed to decrease as the fibre content is increased. A maximum thermal resistivity at 5% wt was found from the reinforcement. On the other hand, the amount of water absorption of the polymer compound increases with the increase in weight percentage of natural fibres. Based on these results, Flexible polyurethane foam reinforced with coconut husks and rice husks shows a promising solution for use as insulation for air conditioning pipes.

Comparison of different cementing techniques for cement penetration under tibial component in total knee arthroplasty: a retrospective observational study

PurposeThis study aimed to investigate the differences in cement penetration between cementing techniques in total knee arthroplasty (TKA).Materials and methodsWe retrospectively evaluated knee undergone TKA at our hospital for both preoperative and postoperative computed tomographic (CT) evaluations. Cementing was performed with hand mixing and hand packing (HM group) and with vacuum mixing and cement gun use (VM group). We measured the area under the tibial baseplate (sclerotic and nonsclerotic sides) and compared the mean and maximum depths of cement penetration at each area.ResultsOf the 44 knees evaluated, 20 and 24 knees were in the HM and VM groups, respectively. At the center of the sclerotic side, the mean penetration depths (2.0 ± 0.7 and 2.5 ± 0.7 mm, p = 0.02) and the maximum penetration depths (4.0 ± 0.9 and 5.0 ± 1.6 mm, p = 0.02) were significantly deeper in the VM group than in the HM group. The correlation between preoperative Hounsfield unit values and mean penetration were r = –0.617 (p < 0.01) and –0.373 (p = 0.01) in the HM and VM groups, respectively.ConclusionThe cementing technique of vacuum mixing and using a cement gun allowed for deeper cement penetration compared with the hand mixing and hand packing technique, even in bone sclerotic sites.

Effect of dispersion methods on electromagnetic interference shielding effectiveness and thermal conductivity of graphene bio‐based epoxy composites

AbstractThe electromagnetic interference shielding effectiveness (EMISE) and thermal conductivity (TC) of a graphene bio‐based epoxy composite were investigated in this study. This study aims to evaluate the effects of dispersion methods on the EMISE and TC of graphene bio‐based epoxy composites. Four dispersion methods were applied to disperse graphene: hand mixing, high‐shear mixing, ultrasonication, and ultrasonication with high‐shear mixing. The graphene weightage used in this study are 3, 6, and 9 wt.%. The EMISE was examined at the X‐band frequency. A microstructural analysis was performed using scanning electron microscopy to investigate the fracture surface morphology of the composites. The results revealed that the composite with 9 wt.% graphene exhibited the highest shielding effectiveness and TC, averaging 8.35 dB and 0.3855 W/mK, respectively, for all the dispersion methods. The composite with 3 wt.% graphene dispersed via ultrasonication exhibited the highest absorption loss (2.98 dB). Moreover, the composites with 6 and 9 wt.% graphene dispersed via ultrasonication with high‐shear mixing showed good overall improvement. This finding provides valuable insights into the effect of dispersion techniques on graphene bio‐based epoxy composites and presents a suitable dispersion method for improving the EMISE and TC.Highlights Effect of dispersion methods on EMISE and TC has been investigated. Optimum SEA achieved in 3 wt.% composites dispersed via ultrasonication. Higher wt.% increased the SE and TC of composites. Ultrasonication with high‐shear mixing improved overall results.

Exploring optimal cathode composite design for high-performance all-solid-state batteries

All-solid-state batteries (ASSBs) have attracted considerable attention due to their high stability, offering a safer alternative to currently used batteries. Extensive research has been conducted to improve cathode part performance. However, the conventional hand mixing (HM) process results in inhomogeneous particle distribution, causing poor interparticle contact due to uneven stress distribution, and the solution process causes unwanted solid electrolyte (SE) deterioration when using a polar solvent although it ensures uniform SE distribution. To overcome these limitations, based on the design rule considering SE surface coverage of less than 100 %, we propose a cathode/SE composite, showing decent ionic/electronic conductivities, uniform SE distribution, and intimate interparticle contact, achievable through a mass-producible mechanical mixing (MM) process. Unlike the HM cell, the MM cell forms well-defined ionic percolating pathways and shows excellent structural stability. Consequently, the MM cell exhibits improved capacity retention during 1000 cycles and stable cyclability even under the harsh condition of 7 wt% SE. Finite element analysis theoretically demonstrates that uniform electrode and electrolyte currents are responsible for the improved performances including increased cathode utilization efficiency and reduced overpotentials. This study reveals the importance of composite design and uniform SE distribution in developing high-performance ASSBs at a practical cell level.

Aluminum hydrolysis for hydrogen generation enhanced by sodium hydride

Aluminum is the most abundant and promising material for hydrolytic hydrogen generation. It can be easily transported and stored. However, the oxide protective layer around Al limits its hydrolytic activity and hinders practical applications. To solve this problem, NaH is introduced to form the core-shell structure of Al-based NaH solid fuel powder by a simple hand mixing method in an open lab environment. The new core-shell structure of Al-based NaH solid fuel powder showed the best hydrolytic performance among Al-based materials and produced 98 % hydrogen yield at a 1 to 0.9 M ratio of NaH and Al in water. The hydrolytic activity consists of NaH hydrolytic splitting and Al hydrolysis. XRD and SEM analysis confirmed that NaH is the key to supporting complete Al hydrolysis and attaining maximum yield as compared to calcium hydride. Our research endorsed the practical implementation of inexpensive and transportable hydrolytic hydrogen generation materials and offered a new idea for the design of hydrolytic hydrogen generation materials for further development.

Effect of Silanized Zirconium Oxide (ZrO&lt;sub&gt;2&lt;/sub&gt;) Filler on Hardness of Acrylic-Based Denture Teeth

PMMA is used in dentistry as the main matrix for denture manufacture. Dentures are a substitute for natural human teeth which must have mechanical properties and are biocompatible to withstand mastication in the oral cavity. However, PMMA has poor mechanical properties, so it is necessary to add filler to the PMMA matrix. In this study zirconium oxide (ZrO2) was used as a filler because it has good mechanical properties and aesthetics. The aim of this study was to study the effect of adding ZrO2 filler on the hardness and compatibility of denture composites at concentrations ( 0%, 1%, 3%, 5%, and 7%). The bulk composite polymerization method used in the manufacture of dental composites is by mixing powdered materials in the form of PMMA, BPO as an initiator, and ZrO2 filler which has been silanized with liquid materials in the form of MMA monomer and cross-linking agent Ethylene Glycol Dimethacrylate (EGDMA). Mixing powder liquid in this method uses hand mixing in a stainless steel container until it reaches the dough phase and is packed into a mold according to ASTM for Vickers hardness tests. Heat cured polymerization technique was used for the curing process in a water bath at 74°C for 90 minutes and continued at 100°C for 30 minutes. The results obtained in this study, the addition of ZrO2 filler to a concentration of 5% showed an increase in the hardness value up to 37.6 VHN. Keywords: Denture Teeth, Composite Bulk Polymerization, Heat cured Polymerization, Zirconium Oxide

Rigid Polyurethane Foams Modified with Soybean-Husk-Derived Ash as Potential Insulating Materials

One of the most popular polymeric materials in the building and construction industry is rigid polyurethane foam (RPUF). In order to reduce the number of expensive chemical components, various fillers are used in the RPUF industry. The aim of this work was to investigate the influence of the biomass originated filler soybean-husk-derived ash on the structure and properties of composite RPUF. Firstly, polyurethane foams were obtained using hand mixing and casting techniques. Composite foams contained 5, 10, 15, and 20 wt. % of the filler. Secondly, the obtained composite materials were analyzed considering their cellular structure using optical microscopy and image processing software. All samples were composed of mostly pentagonal, regular-in-shape cells. Their diameters ranged between 100 and 70 µm. The chemical structure of the foams was investigated using infrared spectroscopy. No chemical interactions between matrix and filler were detected. Mechanical testing was performed in order to evaluate the mechanical performance of the materials. Both compressive strength and Young’s modulus were comparable and equaled approx. 130 kPa and 2.5 MPa, respectively. Wettability analysis indicated a hydrophobic nature of the materials. The obtained results suggested that the cellular and chemical structure of the polyurethane matrix was not affected by the filler incorporation.

Experimental analysis of bearing capacity of soil with the addition of processed E-waste

Soil is the base material for any construction, for the stability of a structure, it is compulsory that the soil used should certainly meet engineering requirements. If not satisfied soil is neglected or certain additives are mixed to enhance the engineering properties of soil. Those additives are known as stabilizers. They are added to natural soil to make it more stable. In recent years utilization of waste in soil has gained attention. In the present experimental study, Soil samples were prepared from the soil near a lake in Lambhua from the region Sultanpur, Uttar Pradesh. This paper shows the outcome of the experimental program done to determine the effect of different dosages of processed E-waste mainly PCB (Printed Circuit Board) in clayey soil (CH). Random hand mixing added different proportions of E-Waste (2%, 5%, 8%, and 10%) to the natural soil. The performance of E-waste with soil was determined with the help of these tests; Atterberg’s limit, Specific Gravity, and California Bearing Ratio (CBR). These experiments were done to identify the amount of enhancement in the strength properties of the soil with respect to the parent soil. From the results, it was found that the bearing capacity of the soil enhances with the addition of processed E-waste.

Effect of imperfect cure on tensile bond measurement

This paper quantifies variability in tensile bond measurement due to incomplete mixing within the nozzles of manual gun epoxy dispensers. Controlled pull-off tests were conducted using an MTS machine and steel substrates were tested to minimize variations in bond line thickness. The pull-off tensile force was evaluated after 1, 2, 3, 7, 14 and 28 days. In each of these six series, five identically prepared specimens were tested. The average coefficient of variation was below 0.10; where it was higher, investigations showed that the epoxy had not mixed thoroughly inside the nozzle. The average 7-day cure tensile bond from identically tested hand mixed epoxy specimens was over 19% higher with lower variability. Hand mixing is recommended in preparation and bonding of pull-off dollies.

Direct milling: Efficient, facile, and green method for processing fibrillated cellulose/polymeric nanocomposites with boosted thermomechanical and rheological performance

Bringing biobased nanomaterials into polymer manufacturing is essential to enhance polymers' properties and address the challenges posed by plastic waste. Using polymers such as polyamide 6 (PA6) in advanced industries, e.g., automotive sector, has been impeded as a direct consequence of their inability to meet the required mechanical properties. Herein, we utilize bio-based cellulose nanofibers (CNFs) to enhance the properties of PA6 by green processing, with no footprint on the environment. We address the issue of the dispersion of the nanofillers in polymeric matrices and demonstrate direct milling (cryo-milling and planetary ball milling) to facilitate a thorough integration of the components. Nanocomposites incorporating 1.0 wt% CNF, processed by pre-milling followed by compression molding, are shown to possess a storage modulus of 3.8 ± 0.2 GPa, Young's modulus of 2.9 ± 0.2 GPa, and ultimate tensile strength of 63 ± 3 MPa (all measured at room temperature). To show the superiority of direct milling in achieving these properties, other frequent approaches used to disperse CNF in polymers, such as solvent casting and hand mixing, are meticulously investigated and compared for the performance of their resulting specimens. The ball-milling method is demonstrated to provide PA6-CNF nanocomposites with excellent performance, better than solvent casting, with no associated environmental concerns.

Investigation on properties of autoclave aerated concrete using different pre-curing and curing techniques

AAC (Autoclave aerated concrete) is a porous and lightweight concrete that is produced through the molding process and can be used to make blocks, cladding, and flooring by autoclaving a variety of raw materials. The primary focus of this work is to assess various pre-curing and curing methods for AAC blocks. Autoclave curing is used in the conventional process of manufacturing AAC blocks, which increases the overall manufacturing cost of AAC blocks. For the production of AAC block, coarse aggregates are not used. The density of the AAC block ranges from 600 to 800 kg/m3. For achieving lesser density, cement, fly ash, sand, and aluminum powder was used. The chemical reaction between aluminum powder and lime in presence of water is exothermic and releases hydrogen gas in the form of bubbles, which results in a lower density. In the present study, various mixture design of AAC block was developed consisting of fly ash, cement, lime, aluminum powder, and water. Samples for determining the mechanical properties of AAC were developed using various mixing methods such as hand mixing, pan mixing, and high-speed hand-drill mixing. The impact of several curing techniques, including air drying and water curing, on the compressive strength and density of the AAC block was examined. Sodium chloride and calcium nitrate were used to increase the setting time of the AAC block. The compressive strength of the AAC block was obtained in the range of 0.2 to 1.5 Mpa and the density of the block was obtained between 512.3 kg/m3 to 750.2 kg/m3. The compressive strength of AAC obtained after autoclave curing is more than the compressive strength obtained after air curing as well as water curing. An attempt has been made in the present investigation to develop AAC blocks without using an autoclave process, so that overall production cost of AAC blocks can be reduced.

Automatic dispersion, defect, curing, and thermal characteristics determination of polymer composites using micro-scale infrared thermography and machine learning algorithm

Infrared thermography is a non-destructive technique that can be exploited in many fields including polymer composite investigation. Based on emissivity and thermal diffusivity variation; components, defects, and curing state of the composite can be identified. However, manual processing of thermal images that may contain significant artifacts, is prone to erroneous component and property determination. In this study, thermal images of different graphite/graphene-based polymer composites fabricated by hand, planetary, and batch mixing techniques were analyzed through an automatic machine learning model. Filler size, shape, and location can be identified in polymer composites and thus, the dispersion of different samples was quantified with a resolution of ~ 20 µm despite having artifacts in the thermal image. Thermal diffusivity comparison of three mixing techniques was performed for 40% graphite in the elastomer. Batch mixing demonstrated superior dispersion than planetary and hand mixing as the dispersion index (DI) for batch mixing was 0.07 while planetary and hand mixing showed 0.0865 and 0.163 respectively. Curing was investigated for a polymer with different fillers (PDMS took 500 s while PDMS-Graphene and PDMS Graphite Powder took 800 s to cure), and a thermal characteristic curve was generated to compare the composite quality. Therefore, the above-mentioned methods with machine learning algorithms can be a great tool to analyze composite both quantitatively and qualitatively.

Bio‐based polyurethane‐graphene composites for adhesive application

AbstractNatural oil‐based polyurethanes are prepared through solvent‐less and easily processable approach for adhesive applications. The polyurethane is optimized through varying the volume fractions of the precursors which was then confirmed through the different analyses to achieve the better combination for composite formation with graphene. The graphene‐polyurethane composites are processed in a simple hand mixing process with different graphene loadings and the role of the addition of graphene is studied using different analyses. The addition of graphene and the interaction with the polymer is well established through structural and thermal studies. The increase in the mechanical property with the addition of graphene to adequate amount at room temperature confirms better interfacial interaction with the polymer. The maximum peel strength obtained for the PU is around 1.05 N/mm, which supports the applicability of the prepared material for adhesive‐based applications.

The mechanical and thermal behaviour of unsaturated polyester matrix (UPM) composite filled with pistachio shell particles (PSP)

This investigation focuses to study the effect of the content of micro scale natural pistachio shell particles on the mechanical and thermal properties of unsaturated polyester matrix composites. The composite of polyester resin reinforced with 10, 20, 30 and 40 wt% PSP was made by hand mixing followed by compression molding. Several mechanical properties viz. tensile strength, flexural strength, impact strength are examined to understand the behaviour of composite material. The thermo-gravimetric analysis of the prepared composites is conducted. The field emission scanning electron microscope is used to investigate the surface morphology of the fabricated composite. The end result from the observation discovers that, the properties of the composites are improved. The maximum tensile, flexural and impact strength is resulted at 40, 40 and 10 wt% respectively.

Low-density PDMS foams by controlled destabilization of thixotropic emulsions

In the current study we demonstrate a method of preparation of low-density polydimethylsiloxane (PDMS) foams from emulsions by using water-based thixotropic fluids as porogens. Aqueous dispersions of synthetic hectorite clay and nanocellulose were used as thixotropic fluids, enabling the preparation of fine emulsions in bulk form with the droplet size down to few tens of microns by simple hand mixing. Contrary to conventional emulsion templating where stabilization of emulsion is required, a strategy was developed for obtaining foams by using controlled destabilization of an emulsion, induced during the curing of the PDMS matrix phase by adding a carefully selected surfactant in optimized concentration. This strategy enables the preparation of bulk PDMS foams with interconnected porosity in a range of density values, fast and deformation-free drying and uniform porous structure with a range of mechanical properties. Clay microplatelet with clearly defined shape and with mass in the nanogram range is retained in spherical pores as the porogen is removed by evaporation. Foams with density down to 0.353 g/cm3 and thermal conductivity of 0.0745 W/m * K were prepared. Elastic modulus of the prepared foams ranged from 0.156 to 0.379 MPa, a reduction of 94.3–86.3% as compared to pure nonporous PDMS.

Cement and Clay Bricks Reinforced with Coconut Fiber and Fiber Dust

For generations, Sri Lankans use cement bricks and clay bricks as common building materials in the construction field. This study investigates the feasibility of improving the strength while lowering the mass and thermal conductivity of bricks by adding coconut fiber or coconut fiber dust as a reinforcing material. Each reinforcing material is used in both clay and cement bricks. The mixtures are prepared according to varying volume ratios of the raw materials used. Coconut fibers are combed and cut into 4-5 cm pieces and dry coconut fiber dust is sieved using a 4 mm sieving mesh. The mixture is prepared by hand mixing and the traditional processes are replicated in making the bricks. Tests are carried out to understand the variation of mass, compressive strength, thermal conductivity, and water absorption of the reinforced bricks in comparison to bricks with no reinforced material. The cement brick reinforced with coconut fiber achieves the expected results in the compressive strength test and thermal conductivity test but underperformed when comparing masses and water absorption. Clay bricks reinforced with coconut fiber dust show impressive results in compressive tests and with the addition of dust, the appearance seems to have changed. It is observed that reinforcing cement bricks with coconut fiber could double the compressive strength along with a 5% reduction in mass. Reinforcing clay bricks with coconut fiber dust increases its compressive strength by over 70% while decreasing the mass by over 30 %. The study proves that it is feasible to use reinforced coconut fiber or coconut fiber dust to improve the properties of both clay and cement bricks, while clay bricks reinforced with coconut fiber are an exception.

Chemical Immersion Effects on Wear Property of Epoxy Reinforced Copper Powder Composites

In this research, the effect of chemical solutions: (sulfuric acid H2SO4, sodium hydroxide NaOH) at (5 M) and distilled water were studied on some mechanical properties. Especially the wear resistance by pin-on-disk and hardness properties for neat epoxy composite and (epoxy - copper powder) composite. That has been prepared by hand mixing (weight ratio = 20%). The samples were immersed in these chemical solutions for different periods (7, 14, and 30) days. Then the hardness by the Shore D method was measured before and after immersion of the samples in acidic, neutral, and alkali solutions. Whereas the hardness was measured by the Vickers method for the wear disk. Wear rate was measured for all samples. The results showed that the neat epoxy composite was more affected by the alkali solution, followed neutral solution, and then the acidic solution by increasing the radius of wear disk (3, 5, 7, 9, and 11) cm, t= 15 min. and the load 5 N. In contrast to the composite material that was more affected by the alkali solution than the acid, neutral solution.

Effect of Water-Solid Mixing Sequence and Crystallization Water of Calcium Sulphate on the Hydration of C3A.

Tricalcium aluminate (Ca3Al2O6: C3A) is the most reactive clinker phase in Portland cement. In this study, the effect of the sequence of mixing of C3A with gypsum and water on the hydration kinetics and phase assemblage is investigated. Three mixing sequences were employed: (i) Turbula mixing of C3A first with gypsum and then with water (T-mix); (ii) Hand mixing of C3A with gypsum before mixing with water (H-mix); (iii) Pre-mixing gypsum with water and then with C3A (P-mix). The results suggest that there is a considerable difference in the hydration kinetics and hydrate phase assemblage, particularly during the initial stages of hydration. P-mix promotes a higher degree of hydration in the initial minutes and considerably influences the main peak in the calorimetry curve of C3A hydration. Effects of calcium sulphate with different amounts of crystallisation water (anhydrite, hemihydrate and gypsum) on C3A hydration are also investigated, and it is found that the water of crystallisation does not have a significant impact on the kinetics of reaction or the formed hydrate phase assemblage.

Spatially-resolved chemical and mechanical examination of adhesive mixing efficiency with ATR-IR and Martens hardness

In this work, a new combined approach to investigate the quality of mixed and cured 2-component epoxy adhesives will be proposed. The spatially-resolved attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) on a microscale and Martens hardness were used to investigate the chemical and mechanical properties respectively the performance of mixed 2-component epoxy adhesives. Therefore, the measurement principle was proved on samples with different proportion of the adhesive hardener. The results show that the difference in hardener proportion has a significant effect on the measurable epoxy concentration and the Martens hardness. In a second step the testing methods were applied to differently mixed adhesive samples to investigate the mixing homogeneity. The mixing methods used were hand mixing, a static mixer, an asymmetrical dual centrifuge and a novel mixing method based on power ultrasound. With a spatially-resolved representation of the ATR-FTIR and Martens hardness test results it is possible to distinguish between different mixed samples and to analyze the mixing quality. It was shown that the resolution and the sensitivity of the ATR-FTIR spectroscopy and the Martens hardness method allow to evaluate the mixing homogeneity of the used 2-component epoxy adhesives. Furthermore, the correlation of the non-destructive ATR-FTIR and hardness test results with destructive lap shear test of adhesive joints was investigated. By this, it was shown, that also the mechanical properties of adhesive joints are affected by the proportion of hardener and the used mixing method and correspond with the ATR-FTIR spectroscopy and Martens hardness.

Fabrication of High Toughness Silk Fibroin/Tungsten Disulfide Nanoparticles Hybrid Fiber and Self-Heating Textile by Wet Spinning

Traditionally, silkworm silk has been used to make high-quality textiles. Nevertheless, various wastes from silkworm silk textiles that are no longer used are increasing, which is also causing considerable waste and contamination. This issue is causing widespread concern in countries that use more silk. Regenerated silk fibroin (RSF) fibers have been shown to be fragile and tender, which prohibits RSF from being widely used as a structural component. Therefore, enriching the function of silk and enhancing the RSF mechanical properties are important directions to expand the comprehensive utilization of silk products. In the present research, wet spinning was used to create a series of RSF/tungsten disulfide (WS2) nanoparticles (NPs) hybrid fiber having distinct WS2 nanoparticles concentrations. It was discovered that the temperature of hybrid fibers containing 0.8 wt% RSF/WS2 nanoparticles might climb from 20.4°C to 85.6°C in 1 min and 108.3°C in 10 min after being exposed to simulated sunlight for a period of one minute and ten minutes. It also had certain antibacterial activity and thermal stability. Fabrics created by hand mixing had outstanding photothermal characteristics under natural sunlight. Furthermore, adding WS2 nanoparticles might increase the tensile properties of hybrid fibers, which could be caused by the reality that the blending of WS2 nanoparticles inhibited the self-assembly of β-sheets in RSF reaction mixture in a dosage-dependent way, as evidenced by the fact that RSF/WS2 nanoparticles hybrid fibers had lesser β-sheets material, crystalline nature, and crystalline size. The above performance makes the RSF/WS2 nanoparticles hybrid fibers promising candidates for application in photothermal fabrics as well as military clothing.