Tan Delta Values Research Articles

Polyurethanes Synthesized with Blends of Polyester and Polycarbonate Polyols—New Evidence Supporting the Dynamic Non-Covalent Exchange Mechanism of Intrinsic Self-Healing at 20 °C

Polyurethanes (PUs) synthesized with blends of polycarbonate and polyester polyols (CD+PEs) showed intrinsic self-healing at 20 °C. The decrease in the polycarbonate soft segments content increased the self-healing time and reduced the kinetics of self-healing of the PUs. The percentage of C-O species decreased and the ones of C-N and C=O species increased by increasing the polyester soft segments in the PUs, due to higher micro-phase separation. All PUs synthetized with CD+PE blends exhibited free carbonate species and interactions between the polycarbonate and polyester soft segments to a somewhat similar extent in all PUs. By increasing the polyester soft segments content, the storage moduli of the PUs decreased and the tan delta values increased, which resulted in favored polycarbonate soft segments interactions, and this was related to slower kinetics of self-healing at 20 °C. Although the PU made with a mixture of 20 wt.% CD and 80 wt.% PE showed cold crystallization and important crystallinity of the soft segments, as well as high storage moduli, the intercalation of a small amount of polycarbonate soft segments disturbed the interactions between the polyester soft segments, so it exhibited self-healing at 20 °C. The self-healing of the PUs was attributed to the physical interactions between polycarbonate soft segments themselves and with polyester soft segments, and, to a minor extent, to the mobility of the polymeric chains. Finally, the PUs made with 40 wt.% or more polyester polyol showed acceptable mechanical properties.

Experimental investigation on the thermal characteristics of Kevlar/hemp intraply hybrid composites: Influence of various weaving designs

In this work, several weaving designs of intra-ply woven fabric Kevlar/hemp fiber (KHE) reinforced epoxy hybrid composites are developed and their thermal characteristics are examined. Thermogravimetric analysis showed that intra-ply hybrid of plain and basket weave designs possessed highest thermal stability. The different weaving patterns of KHE hybrid composites have no effect on the glass transmission temperature (Tg) value as inferred from the differential scanning calorimetry results. The thermomechanical analysis clearly demonstrates the superior dimension stability of the hybrid composites with basket weave. Dynamic mechanical analysis reveals that twill weave KHE have exhibited the maximum storage modulus (2021 MPa), loss modulus (210 MPa) and lower tan delta (0.3090) values compared to all other composites. Based on the obtained results, it is denoted that all the fabricated KHE hybrid composites displayed improved thermal performance. It may be suitable for applications in thermal insulation panels, fire-resistant clothing, and automotive underbody shields.

Evaluation of rheological properties of soft lining materials with different composition under various temperatures

PurposeThe aim of this in vitro study was to evaluate the changes the rheological properties of some soft lining materials, to compare the rheological properties and viscoelastic behaviour at different temperatures.Materials and methodsFive soft lining materials (acrylic and silicone based) were used. the storage modulus (G’), loss modulus (G”), tan delta (tan δ) and complex viscosity (η’) were chosen and for each material, measurements were repeated at 23, 33 and 37 °C, using an oscillating rheometer. All data were statistically analyzed using the Mann Whitney U test, Kruskal Wallis test and Conover’s Multiple Comparison test at the significance level of 0.05.ResultsSoft lining materials had different viscoelastic properties and most of the materials showed different rheological behavior at 23, 33 and 37 °C. At the end of the test (t¹5), at all the temperatures, Sofreliner Tough M had the highest storage modulus values while Visco Gel had the highest loss Tan delta values.ConclusionsThere were significant changes in the rheological parameters of all the materials. Also temperature affected the initial rheological properties, and polymerization reaction of all the materials, depending on temperature increase.Clinical implicationsTemperature affected the initial rheological properties, and polymerization reaction of soft denture liner materials, and clinical inferences should be drawn from such studies conducted. It can be recommended to utilize viscoelastic acrylic-based temporary soft lining materials with lower storage modulus, higher tan delta value, and high viscosity in situations where pain complaint persists and tissue stress is extremely significant, provided that they are replaced often.

The effects of PHB-g-MA types on the mechanical, thermal, morphological, structural, and rheological properties of polyhydroxybutyrate biopolymers

This study investigates the grafting of polyhydroxybutyrate (PHB) chains with maleic anhydride (MA) in concentrations ranging from 5 % to 10 % by weight. This process was conducted during microwave treatment and using a reactive extruder, employing benzoyl peroxide (BPO) as the initiator. The impact of these methods on PHB's overall properties was thoroughly investigated. In the study, PHB–g–MA was incorporated into neat PHB via the extrusion process at a 5 % loading rate. Notably, the mechanical properties exhibited an increase in the presence of PHB–g–MA, likely due to morphological improvements in the neat PHB, as indicated by morphological characterization. X-ray diffraction results indicated crystallinity percentages increase with the addition of MA. Differential scanning calorimetry revealed minimal variation in melting and crystallization temperatures when PHB–g–MA was included. Both storage and loss moduli were enhanced by the incorporation of PHB–g–MA, and the blends exhibited consistent tan delta values. Regarding rheological properties, the storage and loss moduli of PHB blends containing PHB–g–MA blends were observed to rise with rising frequency values. Based on these results, the microwave process was identified as the most effective method for grafting.

Dynamic Viscoelastic Properties of Kenaf Fiber Reinforced Shape Memory Polymer Composites

This paper comprehensively investigates the dynamic viscoelastic behavior of shape memory polymer composites (SMPCs) reinforced with different weight percentages of kenaf fiber (KF) ranging from 0%, 5%, 10%, 15%, 20%, 30% and 40%. The dynamic mechanical behavior of these composites was characterized using dynamic mechanical analysis (DMA) over a range of temperatures. The objective was to determine the optimal fiber content of KF as reinforcement in SMPCs, specifically on viscoelastic response, storage modulus, loss modulus, damping and glass transition behaviour. The results revealed a clear correlation between the KF contents and the dynamic mechanical properties of SMPCs. The storage modulus significantly improves at higher KF content, particularly at elevated temperatures. Additionally, a quantitative assessment of coefficient C demonstrates strong interfacial bonding between fibers and the matrix in samples 30KF and 40KF. These samples also exhibit higher loss modulus and lower tan delta values, providing evidence for the efficacy of KF in enhancing composite properties. Moreover, higher KF contents induce a shift in the glass transition temperature, signifying enhanced in fiber-matrix interaction and thermal stability. The Cole-cole further demonstrates that at higher KF content, the sample surpasses Neat SMPU, presenting compelling evidence of improved matrix-fiber bonding. Statistical analysis through one-way analysis of variance (ANOVA) substantiates the statistical significance of the dynamic mechanical properties across the different weight percentages of KF-SMPCs. Based on these findings, 30KF is the optimal fiber content, balancing mechanical enhancement and feasible fabrication. This decision is grounded in challenges encountered at 40KF, where ensuring composite homogeneity becomes complex. This study contributes to the growing body of knowledge on utilization of natural fibers in development of advanced polymer composites while maintaining eco-sustainability.

Effect of ionizing radiation on mechanical and damping properties of phenyl‐vinyl‐methyl‐polysiloxane elastomers cured with platinum

AbstractIn this study, phenyl‐vinyl‐methyl‐polysiloxane (PVMQ) elastomers were cured with a Pt catalyst and irradiated with different doses (0–80 kGy) using electron beams. Before irradiation studies, rheological analyses were carried out for the three different Platinum‐A (PtA)/Platinum‐B (PtB) ratios by using a Moving Die Rheometer. End of rheological and mechanical analyses 1/2 PtA/PtB ratio was chosen for irradiation studies. To examine the effect of absorbed dose on the mechanical properties of platinum‐cured PVMQ (Pt‐PVMQ) elastomers, stress–strain behavior, stress relaxation, and energy‐damping behavior at static conditions were investigated by cyclic compression analyses. The effect of absorbed dose on the stiffness, permanent deformation, and crosslink densities of Pt‐PVMQ elastomers was also examined. For the identification of the effect of irradiation on the vibration‐damping properties of Pt‐PVMQ elastomers, dynamic mechanical properties were investigated by using an elastomer testing system, and variation of transmissibility, stiffness, and tan delta values with frequency were examined. As a result of this study, the effect of ionizing radiation on the mechanical and dynamic properties of PVMQ elastomer cured with platinum catalyst has been revealed, and it has been shown that some of these properties can be altered with ionizing radiation. The results obtained in this study also showed that Pt‐PVMQ elastomers have higher damping properties than the damping behavior of Pt‐VMQ elastomers, and these Pt‐PVMQ elastomers can be defined as high damping systems.

Unraveling viscoelastic properties of Philippine Mahogany and manufactured acoustic guitar for improving acoustic performance of materials

The acoustic conversion efficiency is one of the parameters used to assess the acoustic performance of a material, which is dependent on the values of tan delta and complex modulus. Studies so far have been conducted looking at tan delta and complex modulus [1], but the specific components of these, which are the storage and loss modulus, and how it affects the tan delta and complex modulus, and therefore acoustic conversion efficiency has yet been studied. Moreover, the effect of heat treatment on the storage and loss modulus, which is more affected by the process have yet been explored. This study aims to characterize the dynamic mechanical properties of Philippine Mahogany, to gain some insights on tuning the acoustic performance of materials for musical instruments, as well as to gain insights on the effect of heat treatment on these properties, composition and to compare it to that of a manufactured guitar. Dynamic Mechanical Analysis (DMA) and Thermogravimetric analysis (TGA) were used to accomplish these objectives. The DMA results showed that storage modulus, loss modulus, complex modulus, and tan delta decreased upon heat treatment, while the sample from guitar showed highest storage modulus, loss modulus, and complex modulus, and lowest tan delta. The TGA results showed minute differences in composition between treated and untreated samples. However, this provided explanation on the difference in the mechanical properties of the samples. Noteworthy, even with tan delta <0.1 for both samples, storage modulus wasn’t dominating the tan delta for both. This study showed the importance of looking at the storage and loss modulus components in improving the acoustic performance of materials as well as the effect of heat treatment on Philippine Mahogany.

Effects of an MDP-based surface cleaner on dentin structure, morphology and nanomechanical properties

ObjectiveTo analyze the effect of Katana™ Cleaner (KC) in nanomechanical and triboscopic properties of etched dentin. MethodsDentin disks from human third molars were prepared. Two main groups of study were established in function of the etching conditioning, phosphoric acid (PA) and Clearfil SE Bond primer (CSEB). Four subgroups were tested within each group: i) untreated dentin (UD), ii) etched dentin (ED) [(PAED/CSEB)], iii) etched dentin contaminated with saliva (PAED+S)/(CSEB+S), and iv) etched and contaminated dentin treated with KC (PAED+S+KC)/(CSEB+S+KC). Nano-DMA testing and imaging, atomic force microscopy (AFM) analysis and nanoroughness (SRa) measurements were obtained. Field emission scanning electron microscopy (FESEM) images were also acquired. ResultsPhosphoric acid etched dentin samples and those specimens contaminated with saliva (PAED+S) attained the highest SRa values, that decreased after Katana™ Cleaner application (PAED+S+KC). In the group of dentin treated with CSEB primer, all subgroups performed similar, except in CSEB+S that attained the highest SRa values. The treatment with KC restored the original values of complex modulus of the untreated dentin. KC application produced the lowest and the highest tan delta values on PAED and CSEB groups, respectively. ConclusionKatana™ Cleaner provided equally mature dentin surfaces after any of the etching methods. Tan delta increased when Katana™ Cleaner was applied on the dentin surface previously etched and contaminated with saliva, regardless the kind of etchant, thus facilitating the dissipation of energy for elastic recoil during loading. Clinical significanceKatana™ Cleaner application after saliva contamination originated similar low roughness levels, regardless the type of etching method. Both complex and storage moduli were similar, after Katana™ Cleaner application, in any case.

Using loofah reinforced chitosan-collagen hydrogel based scaffolds in-vitro and in-vivo; healing in cartilage tissue defects

The herein article aims to report a new scaffold design as a loofah-reinforced chitosan-collagen hydrogel composite scaffold with three different cross-linker concentrations (0.1, 0.3, and 0.5 wt. /v%). From the analyses, the scaffold crosslinked with 0.5% genipin; collagen-chitosan hydrogel scaffold reinforced with loofah (L-CCol5) was found to be suitable for further in vitro and in vivo studies due to its interconnected porous structure, water content (∼ 97%) and tan delta (0.221 at 1 Hz) values comparable to that of cartilage tissue. In vitro analyses depicted that the L-CCol5 scaffold supported rabbit mesenchymal stem cells (rMSCs) adhesion and proliferation with its non-cytotoxic feature. Moreover, in vivo cartilage healing studies were performed using New Zealand male rabbits in three groups: empty control, cell-free scaffold, and rMSCs-laden scaffold. The elastic moduli of these three groups were 0.69, 0.90, and 1.18 MPa, respectively. Besides, microcomputer tomography (MicroCT) scannings supported the in vivo biomechanical analyses as cell-laden scaffolds showed better osteochondral healing. It can be concluded that the L-CCol5 scaffold could be a promising construct in osteochondral tissue engineering applications. The findings revealed that osteochondral remodeling precedes articular cartilage, providing insight into tailored therapeutic approaches, disease progress, and treatment consequences.

The Applicability of Very Low Frequency Diagnostic Testing in the Evaluation of Thermally Aged Stator Coil

In this study, stator coils were aged under thermal stress and changes in insulation condition with the aging cycles were evaluated using diagnostic tests. Diagnostic tests such as partial discharge measurement and tan delta and capacitance measurements were performed at 50 Hz, 1 Hz and 0.1 Hz (very low frequency). The results obtained from this study demonstrate the possibility of evaluating the signs of thermal aging in a stator insulation system with very low frequency tests. Partial discharge parameters like peak apparent charge magnitude and integrated charge per cycle along with tan delta and capacitance tip-up values were used to evaluate the stator insulation condition. Diagnostic test results showed an identical trend with aging cycles at all the chosen test frequency, i.e. 50 Hz, 1 Hz and 0.1 Hz, which indicates that testing at 0.1 Hz is suitable for insulation condition evaluation. Further, the tip-up values have shown distinct variations, especially at 0.1 Hz indicating significant thermal degradation in a stator coil.

Flexural, impact, and dynamic mechanical analysis of glass fiber/ABS and glass fiber/carbon fiber/ABS composites

AbstractIn this study, a hybrid manufacturing technique was proposed to fabricate composites of acrylonitrile butadiene styrene (ABS) with Bidirectional woven glass fiber mat (GF)/ABS and GF/Bidirectional woven carbon fiber mat (CF)/ABS. The composites were fabricated using fused deposition modeling 3D printing, followed by hot compression molding, and their flexural, impact, and dynamic mechanical behaviors were examined. Results indicated that composites with GF and ABS combinations had shown the highest maximum flexural strength (64.46 MPa) and impact strength (0.089 J/mm2). The hybrid composites showed intermediate performance between ABS and GF/ABS composites, with higher flexural strain before failure than ABS and GF/ABS. A comprehensive analysis utilizing scanning electron microscopy was carried out to evaluate the adhesion characteristics of the fiber‐matrix interface in impact‐tested samples. Dynamic mechanical analysis showed that GF/ABS composites had offered superior E′, E″, and tanδ than the hybrid configuration. The peak tan delta values obtained from ABS, GF/ABS, and GF/CF/ABS composites were utilized to determine their respective glass transition temperatures. The observed values for ABS, GF/ABS, and GF/CF/ABS composites were 109.65, 69.95, and 71.5°C, respectively. Some potential applications for the composites fabricated in this study could include the development of lightweight and strong components for aerospace or automotive industries.

Comparative Investigations on Fracture Toughness and Damping Response of Fabric Reinforced Epoxy Composites

Studies were conducted to observe the effect of fracture toughness and damping response on fabric reinforced epoxy polymer composites. The samples of glass fabric, kevlar fabric and carbon fabric having 15wt%, 25wt%, 35wt%, 45wt% and 55wt % fabric content were prepared and tested following ASTM standards. Fracture toughness, peak load and increase in energy absorption are determined for the fabric-epoxy composites. Effect of temperature on storage modulus, loss modulus and tan delta values for various percentages of fabric epoxy composites are noticed and corresponding damping response behaviour is determined. The results revealed that reduction in strength at higher percentage of fabric content is due to improper bonding between fabric and epoxy resin. Higher peak load values and increased values of energy absorption are observed at lower percentage of fabric content. Kevlar fabric proves to be beneficial for specific energy absorption capability. Strength retention capability at higher temperature is far better for carbon fabric epoxy combinations. Composites with lower fabric content retain much higher temperature and peak load. Also the experimental findings are in close proximity with that of theoretical results.

Kajian Teknis Pemeliharaan Transformator Arus Pada Gardu Induk Pltu Tanjung Awar – Awar Babat

The current transformer is an electric power instrumentation device that functions to change a higher current value to a lower value for protection and measurement purposes. Field conditions and service life cause the current transformer to decrease and not function. Therefore, it is important to do this research to determine the current condition of the current transformer. The method used to obtain current transformer quality indicators is the insulation resistance test method and the tangent delta test method. The results of testing the insulation resistance of current transformers at GI Tanjung Awar Awar Babat in 2020-2021 using the VDE standard (Catalogue 228/4) and IEEE std 43-2000 show that the insulation resistance value of all current transformers has increased by an average of 81900Ω from the previous period but, this value is still in good criteria, namely 170 + 1 MΩ and there is an increase in the current transformer grounding resistance test from the previous period with an average of 0.176 however, according to the PLN book 605.K/DIR/2010 the results of the ground resistance test have good criteria. of &lt; 1. Based on ANSI C 57.12.90 and IEEE C57.152-2013 standards, the tan delta test results are still in good condition because the tan delta value is not more than 0.5%. Current transformer tan delta testing in 2020-2021 has decreased, indicating that the insulation performance of current transformers in 2021 is better than in 2020.

Understanding the interfacial interaction of TiO2 nanoparticles filled glass fiber/epoxy composites through dynamic mechanical analysis

ABSTRACT In a multi-component system, the interfacial interactions between the various components trigger the behavior of the composite under external loading and thus determine the bulk properties of the material. In the present work, composite laminates made from TiO2 modified epoxy reinforced with glass fiber are subjected to thermal loading and the effort is made to analyze the interfacial interactions through the experimental values of storage modulus, loss modulus and tan delta. The loading of TiO2 nanoparticles in the epoxy resin is varied to also understand the effect of nanoparticle addition on the interfacial interactions through DMA. The addition of TiO2 nanoparticles helped to increase the storage and loss modulus by improving the rigidity of the polymeric chain. To understand the effect of varying the loading of TiO2 nanoparticles and to gauge the optimum wt.% addition of such nanoparticle, Tan delta, the degree of entanglement and the coefficient of the effectiveness of the nanofiller is found and the results indicate that the laminates successfully withstand the applied thermal load when the TiO2 loading is kept at 2 wt.%. This optimum nanoparticle loading wt.% is further validated through the adhesion factor which is found with the help of Tan delta values.

Study of Viscoelastic Behavior and Mechanical Characteristics of Graphene-Filled ABS Composites

Acrylonitrile-Butadiene-Styrene (ABS) thermoplastic composites were reinforced with graphene fillers for three different weight ratios of 0.3%, 0.6%, and 0.9%. The compounding was prepared using a twin-screw extruder, and the specimens were made using an injection molding machine. The thermal gravimetric analysis (TGA)study revealed that the thermal stability of ABS composites was improved (~7%) by adding graphene fillers in pure ABS.The tensile and flexural strength of the ABS/grapheme composites was maximumwith the addition of 0.6 wt% graphene fillers. But the impact strength was reduced (~42%) for the addition of graphene fillers of more than 0.6 wt%. The stiffness of pure ABS was enhanced by more than ~27% with the addition of graphene fillers. It was found from a Dynamic Mechanical Analysis(DMA) study that the storage modulus and Tan Delta values of the composites were improved compared to pure ABS. The storage modulus was increased by more than ~70% over a wide range of temperatures. The addition of graphene fillers in the ABS matrix improved the glass transition temperature (increased from 110 ̊C to 118 ̊C). Scanning Electron Microscope (SEM) images confirmed the homogeneous mixing of the ABS matrix and the graphene fillers, and better dispersion was noticed with 0.6 wt% of graphene fillers.

Dexamethasone and zinc loaded polymeric nanoparticles reinforce and remineralize coronal dentin. A morpho-histological and dynamic-biomechanical study.

To investigate the effect of novel polymeric nanoparticles (NPs) doped with dexamethasone (Dex) on viscoelasticity, crystallinity and ultra-nanostructure of the formed hydroxyapatite after NPs dentin infiltration. Undoped-NPs, Dex-doped NPs (Dex-NPs) and zinc-doped-Dex-NPs (Zn-Dex-NPs) were tested at dentin, after 24h and 21 d. A control group without NPs was included. Coronal dentin surfaces were studied by nano-dynamic mechanical analysis measurements, atomic force microscopy, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and Student-Newman-Keuls multiple comparisons (p<0.05). At 21 d of storage time, both groups doped with Dex exhibited the highest complex, storage and loss moduli among groups. Zn-Dex-NPs and Dex-NPs promoted the highest and lowest tan delta values, respectively. Dex-NPs contributed to increase the fibril diameters of dentin collagen over time. Dentin surfaces treated with Zn-Dex-NPs attained the lowest nano-roughness values, provoked the highest crystallinity, and produced the longest and shortest crystallite and grain size. These new crystals organized with randomly oriented lattices. Dex-NPs induced the highest microstrain. Crystalline and amorphous matter was present in the mineral precipitates of all groups, but Zn and Dex loaded NPs helped to increase crystallinity. Dentin treated with Zn-Dex-NPs improved crystallographic and atomic order, providing structural stability, high mechanical performance and tissue maturation. Amorphous content was also present, so high hydroxyapatite solubility, bioactivity and remineralizing activity due to the high ion-rich environment took place in the infiltrated dentin.

Tan-delta plateau in vitrimer-like polyurethanes

• Tan delta plateau (TDP) over a long temperature range is revealed in a vitrimer-like polyurethane. • The TDP is rather stable at different frequencies and oscillation strains. • Gradual dissociation right after melting is identified as the reason for TDP. • The time–temperature equivalence of the dissociation process is confirmed. A vitrimer-like polyurethane is investigated for its Tan-delta plateau phenomenon (i.e., a quasi-steady high Tan-delta value over a long temperature range). It is concluded that this plateau is associated with cross-linking dissociation, but on the condition that this dissociation process should be over a long temperature range and right after a melting transition. While this plateau is rather stable at different oscillation strains and frequencies, the time–temperature equivalence of the dissociation process is confirmed to be applicable to this material.

Copper and cobalt doped bioactive glass-fish dermal collagen electrospun mat triggers key events of diabetic wound healing in full-thickness skin defect model

The wounds arising out of underlying hyperglycemic conditions such as diabetic foot ulcers demand a multifunctional tissue regeneration approach owing to several deficiencies in the healing mechanisms. Herein, four different types of electrospun microfibers by combining Rohu fish skin-derived collagen (Fcol) with a bioactive glass (BAG)/ion-doped bioactive glass, namely, Fcol/BAG, Fcol/CuBAG, Fcol/CoBAG, and Fcol/CuCoBAG was developed to accelerate wound healing through stimulation of key events such as angiogenesis and ECM re-construction under diabetic conditions. SEM analysis shows the porous and microfibrous architecture, while the EDX mapping provides evidence of the incorporation of dopants inside various inorganic-organic composite mats. The viscoelastic properties of the microfibrous mats as measured by a nano-DMA test show a higher damping factor non-uniform tan-delta value. The maximum ultimate tensile strength and toughness are recorded for fish collagen with copper doped bioactive glass microfibers while the least values are demonstrated by microfibers with cobalt dopant. In vitro results demonstrate excellent cell-cell and cell-material interactions when human dermal fibroblasts (HDFs) were cultured over the microfibers for 48 h. When these mats were applied over full-thickness diabetic wounds in the rabbit model, early wound healing is attained with Fcol/CuBAG, Fcol/CoBAG, and Fcol/CuCoBAG microfibers. Notably, these microfibers-treated wounds demonstrate a significantly (p < 0.01) higher density of blood vessels by CD-31 immunostaining than control, Duoderm, and Fcol/BAG treated wounds. Mature collagen deposition and excellent ECM remodeling are also evident in wounds treated with fish collagen/ion-doped bioactive glass microfibers suggesting their positive role in diabetic wound healing.

ANALISIS PENGUJIAN TAN DELTA PADA TRANSFORMATOR ARUS DI GITET TASIKMALAYA BAY PENGHANTAR BANDUNG SELATAN-1

Current transformers are essential for substation protection. It converts large currents into smaller currents that are used for measurement and triggering protection systems. Errors in the conversion of electric current can lead to measurement inaccuracies and protection system failures. Improper maintenance and use can shorten the life of the transformer and also lead to earlier system failure. One of the tests applied is the tan delta test to determine the loss coefficient of the insulating material. A decrease in insulation quality increases the tan delta value. The capacitance value is also measured in the tan delta test. An increased capacitance value indicates the paper insulation has been damaged. Generally, damaged insulation causes a short circuit between capacitor layers which is characterized by an increase in capacitance value. By using the GST-Ground method with the Megger Delta 4110 measuring instrument, the tan delta results of the R, S, and T phases in the southern send bay of Bandung-1 GITET Tasikmalaya are 0.42%, 0.47%, and 0.45%. The results of independent calculations are phase R, S, T are 0.29%, 0.28% and 0.31%. From both results, the current transformer can be said to be feasible to operate because the tan delta value is below 1% which is the operational standard of the current transformer.

Influence of Farming System and Forecrops of Spring Wheat on Protein Content in the Grain and the Physicochemical Properties of Unsonicated and Sonicated Gluten.

The potential for enhancing the spring wheat protein content by different cultivation strategies was explored. The influence of ultrasound on the surface and rheological properties of wheat-gluten was also studied. Spring wheat was cultivated over the period of 2018–2020 using two farming systems (conventional and organic) and five forecrops (sugar beet, spring barley, red clover, winter wheat, or oat). The obtained gluten was sonicated using the ultrasonic scrubber. For all organically grown wheat, the protein content was higher than for the conventional one. There was no correlation between the rheological properties of gluten and the protein content in the grain. Gluten derived from organically grown wheat was more elastic than those derived from the conventional one. Sonication enhanced the elasticity of gluten. The sonication effect was influenced by the forecrops. The most elastic gluten after sonication was found for organic barley and sugar beet. The lowest values of tan (delta) were noted for conventional wheat and conventional oat. Cultivation in the monoculture gave gluten with a smaller susceptibility to increase elasticity after sonic treatment. Sonication promoted the cross-linking of protein molecules and induced a more hydrophobic character, which was confirmed by an increment in contact angles (CAs). Most of the organically grown wheat samples showed a lower CA than the conventional ones, which indicated a less hydrophobic character. The gluten surface became rougher with the sonication, regardless of the farming system and applied forecrops. Sonication treatment of gluten proteins rearranged the intermolecular linkages, especially disulfide and hydrophobic bonds, leading to changes in their surface morphology.