Silicone Research Articles

A Study on the Volume Expansion of Vanadium-Based Alloy Powders and Compacts During Hydrogen Sorption

Storing hydrogen in solid metal hydrides provides a safe and efficient storage approach. However, the large volume expansion of metal hydrides during hydrogen absorption imposes substantial stresses on the wall of a hydrogen storage tank. In this study, volume expansion behavior of a V-based hydrogen storage alloy, V61Cr24Ti12Ce3, with body-centered-cubic, was investigated using a self-developed in situ expansion testing device. The lattice expansion of the V61Cr24Ti12Ce3 alloy after full hydrogenation was determined to be 37.85% using X-ray diffraction(XRD). The powder bed, composed of alloy powder with an average size of 3.35 mm in diameter, displays a large volume expansion ratio of 131% at the first hydrogen absorption cycle and 40–45% in the following four cycles. The stable compact bed, made of alloy powders, organic silicone gel, and graphite flakes, shows significantly smaller volume expansion ratio, which is 97% at the first cycle and 21% at the second cycle, and stabilizes at 13% in the following cycles. Also, the compact bed shows similar hydrogen absorption capacity, but faster absorption kinetics compared to the powder bed.

Mechanism Analysis of Bubble Discharge Within Silicone Gels Under Pulsed Electric Field

Silicone gel, used in the packaging of high-voltage, high-power semiconductor devices, generates bubbles during the packaging process, which accelerates the degradation of its insulation properties. This paper establishes a testing platform for electrical treeing in silicone gel under pulsed electric fields, investigating the effect of pulse voltage amplitude on bubble development and studying the initiation and growth of electrical treeing in a silicone gel with different pulse edge times. The relationship between bubbles and electrical treeing in silicone gel materials is discussed. A two-dimensional plasma simulation model for bubble discharge in silicone gel under pulsed electric fields is developed, analyzing the internal electric field distortion caused by the response times of different ions and electrons. Additionally, the discharge current and its effects on silicone gel under pulsed electric fields are examined. By studying the influence of different pulse edge times, repetition frequencies, and temperatures on discharge current magnitude and ozone generation rates, the impact of electrical breakdown and chemical corrosion on the degradation of organic silicone gel under various operating conditions is analyzed. This study explores the macroscopic and microscopic mechanisms of dielectric performance degradation in organic silicone gel under pulsed electric fields, providing a basis for research on high-performance packaging materials and the development of high-voltage, high-power semiconductor devices.

A positionally stable anatomic smooth breast implant

The voluntary recall of textured breast implants due to their association with breast implant-associated anaplastic large cell lymphoma has resulted in the loss of the primary advantage of the textured surface: positional stability. We have engineered a novel soft gel-filled smooth implant with a surface that promotes positional stability without texture, known as the positionally stable smooth implant (PSSI). Miniature anatomically shaped breast implant shells were fabricated from polydimethylsiloxane using 3D-printed molds. The implant shell design incorporates cylindrical wells 1-4 mm in diameter. Implants were filled with commercial breast implant-derived silicone gel. Smooth and textured implants were also fabricated, serving as controls. Six implants per group were implanted subcutaneously into the bilateral rat dorsum. Rotation was measured every 2 weeks for a total of 12 weeks to assess stability. Animals were sacrificed at 4 and 12 weeks, and implant-capsule units were explanted for histological and Micro-computed tomography (MicroCT) analyzes. Four weeks after implantation, PSSI conditions showed tissue ingrowth and conformation to well dimensions, as assessed by histological staining and MicroCT imaging. Twelve weeks post implantation, textured implants and PSSI conditions with larger widths, depths, and well number demonstrated statistically significant increased stability compared to smooth implants (p< 0.05). Tissue ingrowth into shell features occurred by 4 weeks and remained throughout longer time points. No significant differences were found in capsule thickness or collagen content between groups. These results suggest a promising alternative to textured surfaces for inducing implant positional stability.

Polysiloxane encapsulating strategy to enhance the high-temperature electromagnetic wave absorption performance of carbon-rich SiOC ceramics

Carbon-enriched polysiloxane-derived SiOC (C-SiOC) ceramics are promising electromagnetic wave absorption (EMA) materials. However, oxidation and impedance mismatch severely deteriorate their EMA performance at high temperatures. In this study, we used polysiloxane (PSO) to encapsulate the crosslinked precursor of C-SiOC ceramics. After pyrolysis, PSO-derived SiOC-encapsulated C-SiOC (here named PSO-C-SiOC) ceramics were obtained. The PSO-C-SiOC ceramics exhibit an improved oxidation resistance compared with C-SiOC ceramics and basically retain their original dielectric and EMA properties after exposure to air at high temperatures. Moreover, the ceramics can maintain excellent EMA properties at elevated temperatures with good impedance matching. The remarkable high-temperature EMA properties of PSO-C-SiOC ceramics in air are attributed to the protective outer-layer of PSO-derived SiOC ceramic, which enhances oxidation resistance and simultaneously controls the impedance matching. These findings underscore the potential of PSO-C-SiOC ceramics as high-temperature EMA materials.

Spatiotemporal Measurement of Charge at Ceramic Substrate–Silicone Gel Interface in Medium-Voltage Power Modules

Spatiotemporal Measurement of Charge at Ceramic Substrate–Silicone Gel Interface in Medium-Voltage Power Modules

Dynamic covalent bonds enabled robust and self-healing superhydrophobic coatings with multifunctions

Inspired by plants and animals in nature, durable superhydrophobic surfaces have been successfully developed in the past decades. However, the practical application of these superhydrophobic surfaces suffers from poor mechanical and chemical stability after damage or longtime usage. Thus, effective silicone-based polymers are developed to prepare the intelligent self-healing and durable superhydrophobic coatings with multifunctions. The superhydrophobic coatings are composed of dynamic silicone polymers and silica nanoparticles, which can be applicable in various substrates with enhanced water repellency. The abundant hydrogen bonds and reversible B-O covalent bonds in the dynamic silicone polymers enable a strong binding force with the substrate and self-healing nature. Thus, the superhydrophobic coatings exhibit a high contact angle up to 159.3°, and a low sliding angle of 6.9°. Meanwhile, it displays mechanical stability against washing and abrasion damage, and chemical stability in acid and alkaline environment. Especially, it is capable of repairing the superhydrophobicity after damage due to the reversible association/dissociation of dynamic B-O covalent bonds in silicone polymers. In addition, the superhydrophobic cotton fabric shows excellent anti-fouling, self-cleaning, antibacterial property, and can be applied in oil–water separation with high efficiency. This robust and versatile superhydrophobic coatings without containing perfluoro-compounds are promising in commercial textile fishing treatment with low cost.

High-performance flexible sensor with rapidly adjustable sensitivity for wearable electronics

Despite numerous advances in sensor structural design, existing sensors still struggle to achieve rapidly adjustable sensitivity. Here, we utilized a structural design with alternating hard and soft sensor connections, and a lockout device to construct a sensitivity-adjustable sensor (AHS-L). Silicone rubber foams (SF) served as the flexible matrix for fabricating sensors with different hardnesses. Among them, the soft sensor (SRC-ACPF) retained the foam structure, and constructed dual conductive networks both within and on the pore walls, enhancing its resistance sensitivity with a gauge factor (GF) of up to 561.9. In contrast, the SF used in the hard sensor (ASR-PPS) featured a fingerprint-like structure. A conductive network was introduced on the pores and backfilled with liquid silicone rubber to achieve a “soft and hard” distinction from SRC-ACPF. The fingerprint-like structure induced stress concentration during stretching, resulting in high resistance sensitivity for ASR-PPS (GF up to 711.5). This microstructure also amplified contact signals, enabling ASR-PPS to realize intelligent material recognition. Notably, the alternating soft and hard structure of the AHS-L allowed the tensile deformation to be concentrated in the SRC-ACPF. Meanwhile, due to the initial resistance difference, the resistance change in SRC-ACPF has less effect on the overall resistance fluctuation of AHS-L than ASR-PPS. Therefore, a lockout device was introduced to limit the deformation of the SRC-ACPF, allowing the deformation pattern of the AHS-L to be tuned and enabling the sensitivity to be quickly adjusted from low (GF of 3.7 within 0–22% strain, 63.8 within 22–38% strain) to ultra-high (GF of 444.7 within 0–20% strain, 821.2 within 20–46% strain).

Photoacoustic and plasmaelastic waves propagation in semiconductor medium heated by pulsed excitation with magnetic field effect

Semiconductor materials play a crucial role in the fields of science, engineering, and technology due to their high importance. In this work, photoelastic (PE) deformations due to the photonically excited processes are studied according to the photogenerated carriers (plasma waves) during the recombination processes. A photoacoustic theoretical model for the optically excited Silicon (Si) polymer material under the effect of magnetic field is introduced. The coupled between the acoustic and plasm-thermomechanical waves is considered. The governing equation according to the photo-thermoelasticity theory with acoustic pressure is derived. The optoelectronic and thermoelastic properties of semiconductor material are taken into account. The analytical expression of the main physical fields (temperature, mechanical stress, displacement, carrier density, and acoustic pressure) is obtained mathematically using the harmonic wave technique. The theoretical results are represented graphically due to the strength of the magnetic field in two and three dimensions (2D and 3D) and some comparisons are investigated.

Vertically aligned liquid metal thermal pad with excellent electromagnetic shielding and ultra-high compressibility

With the increasing integration level of modern electronics, flexible highly thermally conductive and electromagnetic interference shielding (EMI) materials were urgently demanded in electronic devices. Traditionally carbon or solid metal fillers are widely used as a reinforcement to fabricate a flexible thermally conductive and EMI shielding materials. However Due to the trade-off between mechanical and thermal properties, it is difficult to further improve the performance of solid filler/polymer composites. Here in this work based on the intrinsic excellent electrical and thermal conductivity of liquid metal (LM), we embedded the LM network structure vertically in the silicone gel and fabricated a vertically aligned LM(VALM) composites. Compared to the randomly dispersed LM composites, VALM composite exhibits high through plane thermal conductivity (κ⊥: 6.08 W/m·K) and excellent EMI shielding efficiency (SE) (minimum and maximum EMI SE for VALM2 were 33.2 dB and 39.5 dB). In addition, due to the fluidic nature of LM, composite materials exhibit excellent softness and flexibility (compression modulus of 0.56 MPa). Practical heat dissipation test results and EMIS efficiencies demonstrate usefulness of VALM composite in next-generation electronics.

Axial Load Test Procedure of Short Bored Pile Foundation Model in the Field for Tip Support Bearing Study

Axial load testing on short drilled pile foundation models in the field requires several criteria to be met, including: depth of the tip support layer, adjustments to the capacity and arrangement of the test equipment so that it can still refer to the testing standards. In order for the axial working load on the foundation model to be carried only by the toe bearing resistance, the frictional resistance of the blanket is eliminated through lubrication with liquid silicone. The toe bearing resistance is mobilized at large deformations from 18%d to 30%d. The load test tip bearing resistance value is only about half of the empirically calculated tip bearing resistance.

Spreading of Dynamically Crosslinked Polydimethylsiloxane Drops

ABSTRACTDynamically crosslinked polymer networks, characterized by non‐permanent bonds, offer unique viscoelastic properties that can be used for various applications such as self‐healing coatings and reusable adhesives. This study investigates the spreading behavior of a silicone polymer network with dynamic imine bonds, focusing on the relationship between material properties and spreading dynamics. We prepare polydimethylsiloxane (PDMS) networks with varied rheological properties by adjusting the ratio of amine and aldehyde groups and curing conditions. The spreading of PDMS spherical drops is investigated on surfaces with different surface energies, with the process quantified by measuring the contact length and height over time. Our findings reveal that higher modulus spheres spread more slowly, and that the spreading length increases more on high energy surfaces. This research could provide insights for developing coatings and adhesives with tunable properties by studying the interaction between transiently‐crosslinked polymers and substrates during spreading.

Enhanced dielectric breakdown strength and thermal conductivity of silicone gel composites with high-electron-affinity silicon Dioxide/Cationic Polymer/Nano-diamond

In order to address the contradiction that breakdown strength and thermal conductivity of materials are difficult to improve simultaneously, we report a novel calcined silicon dioxide/cationic polymer/nano-diamond (SD*@ND) filler with high electron affinity via self-assembled in-situ polymerization, electrostatic interaction and calcination technique. Subsequently, the calcined SD*@ND fillers are intercalated into the silicone gel to achieve a concurrent enhancement of electrically insulating properties and thermal conductivity of composites. For example, breakdown strength and thermal conductivity of the silicone gel composites with 20 wt% calcined SD*@ND are 17.97 kV/mm and 0.557 W/m·K, respectively. These results are remarkably higher than those (16.77 kV/mm, 0.211 W/m·K) of silicone gel usually used as a commercial packaging material of power devices. Meanwhile, it also shows excellent high-temperature electrically insulating properties. This work provides a scalable approach to developing a novel silicone gel composites with high performance.

Achieving enhanced thermal conductivity and low dielectric constants using double-oriented fluorinated graphene skeleton in silicone gel composites

The dielectric properties and thermal conductivity of composites are often contradictory. To improve the thermal conductivity, the filler content needs to be increased, which often contributes to the high dielectric constant of the material. Inspired by the layout of community buildings, in this study, silicone gel/double-oriented fluorinated graphene skeleton composites were prepared, which solved the difficulty in assembling fluorinated graphene in situ into a three-dimensional continuous network structure. This greatly improved the thermal conductivity and reduced the dielectric constant of the silicone gel while maintaining a low filler content and the insulating properties. In addition, based on the reconstruction of a real three-dimensional body, the mechanism by which the skeleton improved the material performance was analyzed using finite element simulation. The vertical and horizontal thermal conductivity of the silicone gel/double-oriented fluorinated graphene skeleton composites reached 3.34 W/(m·K) and 2.65 W/(m·K), respectively, and the dielectric constant dropped to 80 % of that of pure silicone gel. This provided a new way to synergistically improve the dielectric properties and thermal conductivity of insulating materials, and has great application potential as a thermal interface material in next-generation electronic devices.

Paradigms in periorbital scar management

Periocular scarring following surgery or trauma is of great aesthetic and functional concern and is difficult to predict. In today’s era, with increasing scientific knowledge and technological advances, both physicians and their patients are highly concerned with minimizing scar appearance as a rising number of patients feel disappointed with their scars and are frequently seeking help for functional and aesthetic improvement. Although various non-surgical and surgical treatment strategies are available it is still difficult to improve excessive scarring. Thus, the importance of thorough knowledge of eyelid anatomy and heal­ing mechanisms along with appreciation of wound closure techniques like placing the sutures at natural cosmetic subunit junctions and along relaxed skin tension lines (RSTLs) in order to achieve scar camouflage and to ensure decreased tension on the wound cannot be more emphasised. Periorbital area should be tackled by the oculoplasty surgeons in view of their distinct anatomy and close proximity to the eye.Scars are commonly treated with a combination of non-surgical techniques, including watchful waiting, scar massage, pressure therapy, silicone gel sheeting, topical or intralesional injections, cryotherapy, laser therapy or radiotherapy. Surgical approaches include pincushioning debulking, direct scar excision, broken line closure techniques, scar lengthening procedures (Z plasty, V-Y/Y-V advancement) and scar excision with lid reconstruction. Mastery of this content is essential for consistent operative success. For good cosmetic and functional outcomes, scar revision techniques should be thoughtfully tailored to the individual and scar subtype.

3D printing molding of UV‐curing liquid silicone rubber by UV follow curing

AbstractSilicone rubber is renowned for its excellent mechanical properties and high biocompatibility. 3D printing enables the realization of more complex structures and the development of more flexible and diverse functions, providing more opportunities and a more comprehensive range of applications in aerospace, biomedical, flexible wearable, soft robotics, and other fields. However, silicone rubber is often hindered by poor rheology and low curing efficiency, which significantly affects the forming performance of the parts. Therefore, this study introduces a UV‐follow curing method for direct ink writing (UFC‐DIW) utilizing UV‐curable silicone rubber. First, a kind of liquid silicone rubber (UV‐LSR) capable of rapid curing under UV light was synthesized, both its curing kinetics and rheological behavior were thoroughly investigated. Then, UV‐LSR inks with lower shear stress were printed using the UFC‐DIW method. A comparative analysis was conducted between the overall structure produced via UFC‐DIW and parts molded through postprinting integral curing methods. The results show that while parts cured postprinting exhibit deformation correlated with printing height, those fabricated using UFC‐DIW maintain structural integrity without deformation. It demonstrates that the UFC‐DIW method can effectively improve the formability of the parts.

A study on sleep posture analysis using fibre bragg grating arrays based mattress

Prolonged sleeping postures or unusual postures can lead to the development of various ailments such as subacromial impingement syndrome, sleep paralysis in the elderly, nocturnal gastroesophageal reflux, sore development, etc Fibre Bragg Gratings (a variety of optical sensors) have gained huge popularity due to their small size, higher sensitivity and responsivity, and encapsulation flexibilities. However, in the present study, FBG Arrays (two FBGs with 10 mm space between them) are employed as they are advantageous in terms of data collection, mitigating sensor location effects, and multiplexing features. In this work, Liquid silicone encapsulated FBG arrays are placed in the head (E), shoulder (C, D), and lower half body (A, B) region for analyzing the strain patterns generated by different sleeping postures namely, Supine (P1), Left Fetus (P2), Right Fetus (P3), and Over stomach (P4). These strain patterns were analyzed in two ways, combined (averaging the data from each FBG of the array) and Individual (data from each FBG was analyzed separately). Both analyses suggested that the FBGs in the arrays responded swiftly to the strain changes that occurred due to changes in sleeping postures. 3D histograms were utilized to track the strain changes and analyze different sleeping postures. A discussion regarding closely related postures and long hour monitoring has also been included. Arrays in the lower half (A, B) and shoulder (C, D) regions proved to be pivotal in discriminating body postures. The average standard deviation of strain for the different arrays was in the range of 0.1 to 0.19 suggesting the reliable and appreciable strain-handling capabilities of the Liquid silicone encapsulated arrays.

Fabrication of microspore-structured replica-mediated silicone polymers for inhibition of cellular adhesion and biofilm formation

Fabrication of microspore-structured replica-mediated silicone polymers for inhibition of cellular adhesion and biofilm formation

Aminopropyltriethoxysilane-modified MXene for remarkably enhancing tracking resistance and flame retardancy of silicone rubber

The preparation of silicone rubber with excellent tracking resistance and flame retardancy is of great significance for application in high-voltage electrical insulation. Unfortunately, to date there lacks an effective strategy to simultaneously endow silicone rubber with satisfied tracking resistance and flame retardancy. In this work, aminopropyltriethoxysilane-modified MXene (APTES-MXene) was prepared by dehydrative condensation between the Si-OH in the hydrolyzed aminopropyltriethoxysilane (APTES) and the hydroxyl groups in MXene. The APTES-MXene was homogeneously dispersed in addition-cure liquid silicone rubber (ALSR). The effects of APTES-MXene on the tracking resistance and flame retardancy of ALSR were investigated. Incorporating 0.175 phr APTES-MXene and 15 ppm Pt catalyst enabled ALSR to pass 1A4.5 level, with a low erosion rate of only 0.29 %, indicating a significantly improved tracking resistance. Meanwhile, the 0.175 phr APTES-MXene also endowed ALSR a UL-94 V-0 rating and the limiting oxygen index (LOI) value reached 32.8 %. It was found that APTES-MXene and Pt catalyst synergistically promoted ALSR forming ceramic layer at elevated temperature. The mechanism for APTES-MXene improving the tracking resistance of ALSR was also proposed. This work provided new insights for high performance high-voltage insulation silicone rubber.

Synthesis and Evaluation of High-Temperature Resistant Polymer Plugging Agent for Water-Based Drilling Fluids.

As the exploration and development of deep wells have emerged as a key option to extract more oil and gas resources trapped underneath, high-temperature formations impose stringent requirements on the thermal stability of plugging agents used in water-based drilling fluids. In this work, β-cyclodextrin, with its unique conical toroidal rigid stable structure and internal hydrophobic and external hydrophilic special adsorption capacity, was first grafted with maleic anhydride to prepare a silicone polymer and then copolymerized with dimethyldiallylammonium chloride (DMDAAC) in the presence of coupling agent vinyltriethoxysilane (A151) and cross-linking divinylbenzene (DVD) to finally obtain a high-temperature resistant plugging agent (AMMD). Subsequently, the molecular structure was evidenced and the performance of AMMD was examined in the polysulfonate-base fluid via a series of tests including high-temperature high-pressure filtration loss, sand tray plugging, and drilling fluid displacement, and the results were compared with the counterpart Soltex under the same conditions. The optimal synthesis conditions for the plugging agent were found as total monomer concentration of 25%, initiator mass fraction of 1% (based on the mass of monomers), monomer feed ratio of m (DVD):m(A151):m(DMDAAC):m(MD) of 15:3:2:15, pH value of 10, reaction temperature of 75 °C, and reaction time of 4 h. FT-IR spectra indicated that the monomers used to prepare AMMD were successfully involved in the reaction for the design of the plugging agent structure. TGA showed that AMMD has a total weight loss of about 35.98% in the range of 284 to 453 °C. Moreover, the addition of 3%AMMD into the base fluid produced a 4.38-fold and 3.8-fold filtration loss control over 60 min at 200 °C using 400 and 800 mD sand trays, respectively, which were comparatively higher than the commercially available Soltex (ca. 3.72-fold and 3.14-fold, respectively, using 400 and 800 mD). This then contributed to AMMD's superior plugging performance in drilling fluid based on the drilling fluid displacement experiment, implying that AMMD could find potential use as a plugging agent in polysulfonate drilling fluid under severe geothermal conditions.

Synthesis, Characterization and Study of Thermal Properties of New Silicone Polymers and Their Nanocomposites

الهدف من الدراسه تحضير فئه جديده من بوليمرات السليكون P1-P4 والتي تمت على اساس استحدام ثنائي مثيل ثنائي كلورو سيلان((DCDMS مع بعض المركبات العضويه التي تحتوي مجاميع الهيدروكسيل الطرفيه والتي حضرت لاول مره M1-M4، بأستخدم البلمره التكثيفيه .كما تم تحضير متراكباتها النانويهP′1-P′4 بوجود جسيمات الفضه النانويه (Ag-NPs) باستخدام طريقة صب المحاليل. شخصت جميع التراكيب للمونمرات والبوليمرات المحضره باستخدام مطيافية FTIR و H1NMR (لبعض البوليمرات) مما سمح بتحديد المجموعات الوظيفية الفعاله للمونومرات وبوليمرات السيليكون. اجريت التحاليل الحراريه الوزنيه TGAوالمسح المسعري التفاضلي DSC لتقييم السلوك الحراري وتاثير وجود جسيمات الفضه النانويهAgNPs .اظهرت نتائج التحليل الحراري ان وجود حلقات الفنيل اظهرت استقرارحراري لبوليمرات السيليكون النقية P1-P4 وان اقحام جسيمات الفضه النانويه بوزن 7 ٪ اظهرت تحسن في الاداء الحراري للمتراكبات النانويه P′1-P′4 مقارنة ببوليمرات السليكون النقيه، ممايعني ان درجة الحراره لفقدان الوزن TGA كانت اعلى لمعظم المتراكبات النانويه P′1-P′4 مقارنة الى بوليمرات السليكون النقيه ، حيث ازدادت درجة الحراره لفقدان الوزن TGA للبوليمر P2 من 127 الى 196 للمتراكبه التانويه P′2 ،وهذا قد بعود الى ملئ الفراغات الحره بين السلاسل البوليمريه بواسطة جسيمات الفضه النانويه .استخدمت تقنية حيود الاشعه السينيه XRD لتشخيص وجود جسيمات الفضة النانويه حيث اظهرت XRD وجود الفضه بحجم نانوي يتراوح بين 20-30 نانوميتر بالاضافه الى دراسة شكل وحجم جسيمات الفضه يتقنية مجهر القوة الذريه وكما تم دراسة مورفولجية السطح باستخدام تقنية مجهر المسح الالكتروني والذي اظهرنوعا ما سطح موحد للمتراكبه النانويه.