Silicone Rubber Matrix Research Articles

Synergistic flame‐retardant effects between silane coupling agents modified expanded graphite and Pt catalyst in silicone rubber composites

AbstractIn this work, different kinds of silane coupling agents modified expanded graphite (MEG) fillers were successfully prepared and then incorporated into silicon rubber matrix to fabricate flame‐retardant composite materials (SR/MEG). The inserted MEG fillers with siloxane chains exhibited good compatibility with the silicon rubber matrix, which cannot only reduce the negative impact of adding fillers on mechanical properties but also endow the silicon rubber composites with ideal flame retardancy. Subsequently, platinum (Pt) catalyst was incorporated into the SR/MEG composites to prepare SR/MEG/Pt composites, and the synergistic effects of MEG and Pt catalyst on the thermal stability, flame retardancy, and combustion behavior of silicon rubber composites were systematically investigated. The target SR/MEG/Pt composite with appropriate addition of MEG and Pt catalyst can obtain relatively high char residue of 41.9% and limiting oxygen index value of 29.6%, as well as achieve V‐0 rating in the vertical combustion test, owing to the formation of expanded and dense silicon–carbon protective layer under the catalysis of Pt catalyst. Moreover, the cone calorimeter test results showed that the peak of heat release rate and total heat release of SR/MEG composites were further reduced after the addition of an appropriate amount of Pt catalyst, manifesting the good synergistic effect of MEG and Pt catalyst on the flame retardancy performance of silicon rubber. The method proposed herein may provide a promising way for fabricating high‐performance flame‐retardant silicone rubber materials.

In51Bi32.5Sn16.5@SiO2 microcapsules-based composite phase change materials with high thermal conductivity and heat storage density for electronics thermal management

Combining phase change microcapsules and various matrix materials can construct novel composite phase change materials (CPCMs). These composite materials hold immense potential for electronics thermal management, owing to their adjustable heat storage capacity and stable shape. Most previous studies focus on enhancing the thermal conductivity of CPCMs by adding thermally conductive fillers or modifying the microcapsule shells. Nevertheless, achieving both high thermal conductivity and heat storage density simultaneously remains a challenge. In this paper, low melting point alloy (In51Bi32.5Sn16.5) was introduced as core material of the microcapsule to enhance the thermal conductivity, due to its significantly higher thermal conductivity compared to commonly used organic or inorganic phase change materials (PCMs). In51Bi32.5Sn16.5@SiO2 microcapsule was synthesized through the sol-gel polymerization method. Furtherly, a form-stable CPCMs consisting of the microcapsules and silicone rubber (SR) matrix were prepared for electronics thermal management. The In51Bi32.5Sn16.5@SiO2 microcapsules exhibit an impressive thermal conductivity of 13.49 Wm−1 K−1, acting as a dual-functional filler for thermal storage and thermal conduction enhancement. Hence, the CPCMs possess a significantly enhanced thermal conductivity of 0.45 Wm−1 K−1, representing a remarkable improvement of 350 % compared to that of pure SR. In addition, the phase change heat storage density of the CPCMs was as high as 71.73 J/cm3. Notable, the prepared CPCMs demonstrate exceptional heat dissipation performance, resulting in a remarkable 23 °C reduction in chip temperature when applied for thermal management. This study offers a novel perspective on the preparation of microcapsule-based CPCMs for electronics thermal management.

Study on the shielding performance of bismuth oxide as a spent fuel dry storage container based on Monte Carlo simulation

For traditional spent fuel shielding materials, due to physical and chemical defects and cost constraints, they have been unable to meet the needs. Therefore, this paper carries out the first discussion on the application and performance of bismuth in neutron shielding by establishing Monte Carlo simulation on the neutron flux model of shielded spent fuel. Firstly, functional fillers such as bismuth oxide, lead oxide, boron oxide, gadolinium oxide and tungsten oxide are added to the matrices to compare the shielding rates of aluminum alloy matrix and silicone rubber matrix. The shielding rate of silicone rubber mixture is higher than aluminum alloy mixture, reaching more than 56%. The optimal addition proportion of bismuth oxide and lead oxide is 30%, and the neutron radiation protection efficiency reaches 60%. Then, the mass attenuation coefficients of bismuth oxide, lead oxide, boron oxide, gadolinium oxide and tungsten oxide in silicone rubber matrix are simulated with the change of functional fillers proportion and neutron energy. This simulation result shows that the mixture with functional fillers has good shielding performance for low energy neutrons, but poor shielding effect for high energy neutrons. Finally, in order to further evaluate the possibility of replacing lead oxide with bismuth oxide as shielding material, the half-value layers and various properties of bismuth oxide and lead oxide are compared. The results show that the shielding properties of bismuth oxide and lead oxide are basically the same, and the mechanical properties, heat resistance, radiation resistance and environmental protection of bismuth oxide are better than that of lead oxide. Therefore, in the case of neutron source strengths in the range of 0.01–6 MeV and secondary gamma rays produced below 2.5 MeV, bismuth can replace lead in neutron shielding applications.

Electro‐bio‐mechanical behavior of graphite nanoplatelets–silicone rubber‐based composites for wearable electronic systems

AbstractAdding graphite nanoplatelets (GNP) into silicone rubber (SR) composites have shown significant potential for wearable electronics, where electrical, mechanical, and tribological properties play a crucial role. This study investigates the effects of incorporating graphite nanoplatelets (GNP) into SR composites and their impact on these key properties. Solution mixing of SR and GNP was performed to confirm good dispersion of the GNP within the SR matrix. The results showed improved tensile strength and modulus while stabilizing the flexibility and stretchability required for wearable electronics. For example, the tensile strength of the composites was 0.86 MPa (control) and increased to 1.18 MPa (5 part per hundred rubber [phr] GNP), and 1.55 MPa (15 phr GNP). Similarly, the stretchability was 177 % (control) and increased to 190 % (5 phr GNP), and 184 % (15 phr GNP). Moreover, the electro‐mechanical tests were studied and the output voltage for the samples were 0.28 milli‐volt (mV) (5 phr GNP), and 0.31 mV (15 phr GNP). Similarly, the output voltage generation was studied through human motions. The results obtained from these biomechanical motions such as thumb pressing were 0.7 mV (5 phr GNP), and 2.7 mV (15 phr GNP). The study finds the potential of GNP‐SR composites as multifunctional materials such as wearable electronics. Overall, this research guides the development of advanced wearable devices, soft robotics, and bio‐inspired electronics with improved performance and durability.

Shape-stabilized phase change materials for thermal energy storage and heat dissipation

Shape-stabilized phase change material (SSPCM) are widely used as energy storage materials due to its advantages of easy preparation and adjustable scale. But the thermal conductivity enhancement of SSPCM still need to be further studied to improve the energy storage efficiency. In this work, silicone rubber (SR)/paraffin@SiO2 (Pn@SiO2)/graphene nanoplates (GNPs) shape-stabilized phase change materials (SPG) with different GNPs content were prepared. Pn@SiO2 and GNPs can be homogeneously dispersed in the SR matrix due to the enhanced interfacial compatibility between Pn@SiO2 and SR. The leakage rate of SPG composites was as low as 0.25% due to the protection of SiO2 shell, SR matrix and GNPs. The SPG composites had excellent thermal storage properties, with the enthalpy about 50 J·g−1. The thermal conductivity of SPG composites was improved with the content of GNPs, the thermal conductivity of SPG reach 0.989 W·m−1·K−1 at a GNPs content of 10 phr. The low hardness of SPG composites above the phase change temperature can provide a more cohesive surface when applied to heat dissipation. The heat dissipation of the SPG composites in electric devices was simulated and demonstrated that the addition of GNPs made the heat dissipation rate of the SPG composites increased significantly. Therefore, the SPG composites can be applied in thermal energy storage and heat dissipation of electronic devices.

Multifunctionality of MWCNT and TiC hybrid filler silicone composite for energy harvesting and strain sensing

AbstractThe flexible silicone elastomer‐conductive composite was developed with enhanced energy harvesting and strain sensing. A hybrid nanofiller system with multi‐walled carbon nanotubes (MWCNTs) and titanium (IV) carbide (TiC) was used as reinforcing agents for the elastomer. The 4 MWCNT +5 TiC composite has 1.34 MPa tensile strength, 136.85% higher than unfilled silicone rubber (SR) matrix. The unfilled sample has a 1.558 MPa compressive modulus, while 4 MWCNT +5 TiC has 3.87 MPa. The machine and finger presses were utilized to test the energy harvesting of the composite. With greater cyclic stability, the 4 MWCNT +5 TiC sample performed exceptionally well in the machine press in the output voltage range of around 120 mV. Among the thumb presses, 2 MWCNT +5 TiC yielded the best results, with a voltage of about 100 mV. The 3 MWCNT +5 TiC sample produced 9044% more energy than the single filler 3 phr MWCNT sample from our previous work. Higher MWCNT content enhanced composite stiffness, making finger pressing harder and decreasing energy output. The strain sensing test on the 4 MWCNT +5 TiC composite showed high gauge factors (GF = 7.532 and 23.944) and good linearity (R2 = 0.909 and 0.939) over a strain range of Δε = 0%–14% and 14%–22%. Silicone composites' mechanical, energy harvesting, and strain sensing performance improved greatly with the MWCNT and TiC hybrid fillers. These composites could be used in self‐powered wearable electronics, machine or structural deformation monitoring, and human motion sensing.Highlights A stretchable device was developed with improved energy harvesting and strain sensing. Rubber composites were fabricated from MWCNTs, TiC hybrid fillers, and SR matrix. The energy harvesting was 9044% higher for hybrid filler compared to MWCNT as the only filler. Robust strain sensing properties with a gauge factor of 23.9, linearity of 0.91, and relaxation time of 0.1 s. The final composites are useful for self‐powered wearable electronics, health monitoring, and human motion sensing.

Influence of chromium oxide nanoparticles and fiber fillers on silicone rubber nanocomposite

The development of polymer composites, considering the environmental issues, is aimed for minimizing the industrial content. New environmental-friendly nanocomposites, based on silicone rubber matrix and different concentrations of natural fiber/chromium oxide fillers, are prepared for the first time. The microstructural analysis confirms the successful obtaining of microfibers after treatment and chromium oxide nanoparticles and the formation of the final composite. The nanocomposites achieved improved physical and mechanical properties due to the dual effect of both fillers and attachment to the matrix. The 1% optimized nanocomposite achieved the highest modulus, dielectric properties, hydrophobicity, and surface stability. The effect of exposure to weathering conditions was studied. The characterization sentence asserts the preparation of a novel silicone rubber nanocomposite with improved properties, along with the environmental impact, regarding the dual effect of natural fiber waste and chromium oxide nanoparticles.

Experimental Study and Mechanism Analysis of Composite Insulator Chalking in Extra-High Voltage (EHV) Transmission Line

The chalking of composite insulators is referred to a kind of abnormal aging of the silicone rubber sheds. It has serious adverse effects on the long-term operation of the insulators, but the mechanism behind its generation and development remains unclear. In order to deeply understand the phenomenon of composite insulator chalking, this paper took chalked composite insulators operating on extra-high voltage (EHV) AC 500 kV as samples for research. Appearance inspection, hydrophobicity test and tensile stress test were performed on the samples to determine the change of their surface properties after chalking. It is found that a layer of white powder was formed on the surface of the sheds, the hydrophobicity level of which come to a range from HC1 to HC4, and the tensile stress tolerance and mechanical strength of the silicone rubber decreased significantly. Further, XPS analysis, FTIR detection, and TG analysis were carried out to explore the microscopic process inside the material during its chalking. The results show that the oxidation reaction of Si-C bond transforms the composition of silicone rubber, bringing damage to its apparent performance; the generation of strong polar groups such as –C=O group is the main reason for the decrease in the flexibility of the silicone rubber structure and then the formation of a powdered layer; and above all, the chalking process is based on a series of chemical decomposition reactions, in which the decomposition of polydimethylsiloxane (PDMS) as silicone rubber matrix plays a predominant role, and the decomposition of aluminum hydroxide (ATH) serves as a secondary.

Improving high heat flux ablation resistance of silicone rubber composites by laying low-areal-density carbon fiber fabrics

To meet the thermal protection requirements under stress or high heat flux environments in advanced space vehicles, it is imperative to enhance the ablation resistance of flexible silicone rubber-based materials. In this study, low-areal-density carbon fiber fabric with distinctive mesh-like feature was introduced to build a high-strength char layer to improve the thermal protection capability. Under high heat flux (3.52 MW/m2), with the number of fabrics in the samples from 0 to 9, the compressive strength of the char layer reaches 9.400 MPa, developing by an impressive 134.65 %. In addition, the strong oxidation-resistant ceramization products converted from the silicone rubber matrix during ablation forms a skin-core structure with the fiber bundles, which conducive to prevent oxidative damage to the fabric. Further, the evolution of the char layer under different heat flux was revealed to assess the influence of fabric reinforcement on the ablation performance. In contrast to the composite without fabric (3.52M-0L), the fabric reinforced sample (3.52M-9L) with the best ablation resistance showed a decrease of 13.93 % in linear ablation rate and 30.43 % in mass ablation rate under the 3.52 MW/m2 heat flux. This study provides guidance for the design of flexible thermal protection materials with exceptional ablative resistance to withstand more severe operational environments.

Constant Magnetic Field as a Tool for Modification of the Properties of Polymer Composites with Silicone Rubber Matrix

The aim of this research was to obtain new polymer composites with a silicone rubber matrix, having favorable mechanical and functional properties. They contained admixtures in the amount of 10% by weight of expanded graphite (EG) or birch bark (BB). Additionally, some composites contained magnetic particles in the form of carbonyl iron in the amount of 20% by weight. The tensile strength, water absorption, frost resistance, surface contact angle, and free surface energy were examined. Microscopic images were taken using the SEM method and the content of some elements in selected microareas was determined using the EDXS method. In the study, a constant magnetic field with magnetic induction B was used, by means of which the properties and structure of polymer composites were modified. Scientific research in the field of polymers is the driving force behind the progress of civilization. Smart materials are able to respond to external stimuli, such as magnetic fields, with significant changes in their properties. The magnetic field affects not only chemical reactions, but also the crystallographic structure and physicochemical properties of the final products. Owing to their unique properties, such materials can be used in the space industry, automotive industry, or electrical engineering.

Effects of uniaxial tensile strain on the release of small molecules from silicone rubber

AbstractSilicone rubber materials may be subject to mechanical strains which can affect the transport properties of small molecules loaded in the materials such as plasticizers and active molecules, hence deteriorating their intended mechanical properties or affecting their performance as carriers of active molecules. Therefore, it is important to understand the effects of mechanical strains on transport of small molecules in the silicone rubber matrix. In this work, silicone rubber sheets loaded with 2 wt% triacetin were stretched and held at four different lengths up to 125% engineering strain. The mass transfer coefficients and diffusion coefficients of triacetin in the strained silicone rubber were determined by monitoring the release of triacetin using headspace gas chromatography–mass spectrometry. It was found that there was no significant change of diffusion coefficient as the applied strain increased, which might result from two microstructure changes that had conflicting effects on diffusion: chain orientation and free volume deformation.

Enhancement of hydrophobic properties of HTV silicone rubber by CF4 plasma treatment

In this paper, a superhydrophobic surface of silicone rubber was fabricated by plasma treatment method. Modification of the surface chemistry under CF4 atmosphere at different times (3, 5, and 7 min) and powers (50, 75, and 100 W) of plasma process has been investigated. A superhydrophobic surface with contact angle of 151.3° was obtained for plasma treated sample at 100 W for 7 min. X-ray photoelectron spectroscopy (XPS) results indicated that the surface fluorination of silicone rubber increased as the time and power of plasma exposure increased. Investigation of the F 1s and Si 2p spectra approved the formation of F-C and F-Si bands. Also, the roughness of the surface increased from about 42 nm for untreated to 55 nm for treated sample (7 min at 100 W) due to the emergence of the ceramic fillers in degraded silicone rubber matrix after plasma treatment. Both of the surface fluorination and roughness increment are the reasons of superhydrophobicity properties. Examination of the hydrophobic recovery by surface contamination method indicated that a contact angle of 101° was recovered after 9 days.

Conformal BN coating to enhance the electrical insulation and thermal conductivity of spherical graphite fillers for electronic encapsulation field

Herein, we provided a structural design strategy of constructing boron nitride (BN) conformal coating on the surface of the spherical graphite (SG) particles via precursors deposition and high-temperature pyrolysis method to achieve improved electrical insulation. The dissolved and reprecipitated BN precursors were uniformly deposited on the surface of polydopamine-modified SG through strong adhesion and hydrogen bonding of polydopamine. Then, the homogeneous and dense BN ceramic coating was formed on the surface of SG via slow pyrolysis at high temperature. The complete encapsulation of BN coating prevents the SG particles directly contacting with each other in the silicon rubber (SR) matrix to retain electrical insulation of SR composites. Furthermore, the BN coating flattens the uneven surface of SG so that the fillers are better infiltrated by the SR matrix. The small specific surface area of SG@BN filler particles is beneficial to significantly reduce the generation of the filler/matrix interfaces and weaken phonons scattering, thus decreasing the thermal boundary resistance. As a result, the thermal conductivity of prepared SG@BN/SR composites is up to 3.65 W m−1 K−1, which is 20.2-fold of that of pure SR with 0.18 W m−1 K−1. And the SG@BN/SR composites exhibit a satisfactory breakdown voltage of 5.6 kV mm−1, which is much higher than 1.1 kV mm−1 for the original SG/SR composites. This strategy is worth using for reference to extend the application of graphite-type fillers in the electronic encapsulation field.

Intercalation of silsesquioxane surfactant in layered double hydroxide for silicone rubber composites: Enhancing interfacial interactions toward improvement of mechanical, thermal, and gas barrier properties

AbstractThe incorporation of two‐dimensional layered metal hydroxides (LDHs) into nonpolar silicone rubber (SR) is not yet universal, mainly because of their originally hydrophilic surface and limited interlamellar galleries that make nanoparticle dispersion and intercalation of polymer segments more difficult. In this work, we develop a modified Ca‐Mg‐Al LDH form by conjugating the ternary Ca‐Mg‐Al LDH with silsesquioxane (SQ) surfactants containing benzoic acid moieties and polyethylene glycol chains via an in‐situ intercalation process. The bulky anions conjugation to the hydroxide layers dictated both the surface hydrophobicity and interlayer spacing of the modified Ca‐Mg‐Al LDH, enabling strong inter‐constituent interactions within the nanocomposites as well as extensive polymer penetration after incorporation into the SR matrix. The SR/modified LDH nanocomposites show excellent thermal stability and satisfactory mechanical properties due to the homogeneous dispersion and good compatibility of modified Ca‐Mg‐Al LDH. Moreover, we have observed that the shear‐induced orientation of the nano‐layered particles upon application of stress imparts a more notably decreased SR/LDH‐SQ‐40 gas transmission rate (reduced by 55% with respect to that in the unstretched composite films). This result also corroborates the better interfacial bonding and highly efficient load transfer between silsesquioxane‐modified LDH and polymer in melt extrusion mixing of such composites.Highlights Modified Ca‐Mg‐Al LDH with increased layer spacing and reduced hydrophilicity. Modifier enhanced the interfacial adhesion between Ca‐Mg‐Al LDH and SR matrix. SR/modified LDH showed excellent thermal stability and mechanical properties. Orientation and exfoliation enhanced gas barrier properties of SR/modified LDH.

Investigation of gamma shielding parameters of VMQ/W/TiO2 polymer composites

Vinyl Methyl Silicone Rubber (VMQ) matrix with Tungsten (W) and Titanium dioxide (TiO2) as multi-filler materials was studied with varying Tungsten content (0, 30, 50, 70 phr (parts per hundred rubber)) and investigated for gamma radiation shielding applications. The mass attenuation coefficient of VMQ/W/TiO2 composites for 80, 356 and 662 keV were obtained using XCOM database. Various radiation shielding parameters, such as the linear attenuation coefficient, half-value layer, tenth-value layer and relaxation length were evaluated using the values of mass attenuation coefficient and density. It is found that the attenuation coefficient increases with increase in filler density, whereas the HVL, TVL and relaxation length of the composites found to decrease. The mass attenuation coefficient and HVL of VMQ/70W/30 TiO2 phr are found to be 2.88 cm2/g and 0.1 cm for 80 keV gamma rays. The results confirm that the examined shielding parameters are associated with photon energies and chemical composition. Hence, the performance of VMQ/W/TiO2 rubber based composites show superior shielding properties and the experimental results are found to be better than barite at 356 & 662 keV and slightly lower than lead and barite at 80 keV.

An experimental investigation on the matrix dependent rheological properties of MRE

The rheological properties of magnetorheological elastomers are influenced by magnetically sensitive fillers and the elastomer matrix. The ability to respond to an external magnetic field is imparted by the fillers, while the load-bearing capability is determined by the matrix type. In this paper, the effect of matrix material on the properties of magnetorhological elastomer is explored experimentally. Carbonyl iron particle content is varied by 0%, 15% and 25% by volume to produce magnetorheological elastomer samples using natural rubber, silicone rubber and nitrile butadiene rubber matrices. Forced transmissibility test approach was employed to evaluate the field induced variations in the dynamic stiffness and loss factor of magnetorheological elastomers. The dynamic stiffness of nitrile butadiene rubber is the highest, while that of silicone rubber is the lowest. Addition of carbonyl iron particles significantly improves stiffness, although these gains depend on the properties of unfilled matrix. The addition of 25% by volume of carbonyl iron particle increased the dynamic stiffness of a silicone rubber matrix based magnetorheological elastomer by 67.78%, while the similar change in magnetorheological elastomer with nitrile butadiene rubber matrix was 38.58%. The field dependent response of magnetorheological elastomers is governed by the matrix and ferromagnetic filler concentration. These qualities are higher in magnetorheological elastomer with a low initial dynamic stiffness matrix and lower in magnetorheological elastomers with a stiffer matrix.

Simultaneous improvements in the flame retardancy and neutron shielding properties of silicone rubber through gadolinium phenylphosphonate–boron nitride heterostructures

In this study, a novel flame-retardant and neutron-shielding additive was fabricated by the in-situ co-precipitation of gadolinium phenylphosphonate (GdPP) on boron nitride (BN) nanosheets. The resulting BN-GdPP heterostructures were incorporated with silicone rubber (SR) to produce a radiation protection composite. BN-GdPP/SR exhibited excellent mechanical properties, flame retardancy, smoke suppression, and thermal neutron shielding properties. The limiting oxygen index and UL-94 rating of BN-GdPP/SR were 34.19% and V-0, respectively. The peak heat release rate, total heat release, and total smoke production of BN-GdPP/SR decreased by 40.82%, 39.76%, and 32.60%, respectively, compared with those of pristine SR. The flame retardancy and smoke suppression were attributable to the synergistic effects between BN and GdPP. Moreover, owing to the homogeneous dispersion and horizontal orientation of BN-GdPP in the SR matrix, the tensile strength, thermal neutron shielding rate, and cross section of BN-GdPP/SR were 6.26 MPa, 89% (for 6 mm thickness), and 4.16 cm−1, respectively. This work provides a promising strategy for preparing high-performance multifunctional radiation shielding materials.

Investigations of Shape Deformation Behaviors of the Ferromagnetic Ni-Mn-Ga Alloy/Porous Silicone Rubber Composite towards Actuator Applications.

Ferromagnetic shape memory alloys (FSMAs), which are potential candidates for future technologies (i.e., actuators in robots), have been paid much attention for their high work per volume and rapid response as external stimulation, such as a magnetic field, is imposed. Among all the FSMAs, the Ni-Mn-Ga-based alloys were considered promising materials due to their appropriate phase transformation temperatures and ferromagnetism. Nevertheless, their intrinsic embrittlement issue and sluggish twin motion due to the inhibition of grain boundaries restrict their practicability. This study took advantage of the single-crystal Ni-Mn-Ga cube/silicone rubber composite materials to solve the two aforementioned difficulties. The single-crystal Ni-Mn-Ga cube was prepared by using a high-temperature alloying procedure and a floating-zone (FZ) method, and the cubes were verified to be the near-{100}p Ni-Mn-Ga alloy. Various room temperature (RT) curing silicone rubbers were utilized as matrix materials. Furthermore, polystyrene foam particles (PFP) were used to provide pores, allowing a porous silicone rubber matrix. It was found that the elastic modulus of the silicone rubber was successfully reduced by introducing the PFP. Additionally, the magnetic field-induced martensite variant reorientation (MVR) was greatly enhanced by introducing a porous structure into the silicone rubber. The single-crystal Ni-Mn-Ga cube/porous silicone rubber composite materials are considered to be promising materials for applications in actuators.

Facile preparation of smart nanocomposite adhesive with superhydrophobicity and photoluminescence

Smart photoluminescent nanocomposite adhesive was developed toward simple commercial manufacturing of long-persistent luminescent and hydrophobic applications. The prepared photoluminescent glue was able to continue emitting light after turning the illumination source off even after being in the dark for up to 1.5 h. Lanthanide-doped strontium aluminum oxide (LSAO) nanoparticles (NPs) dispersed in liquid silicone rubber (SR) was prepared to function as nanocomposite glue for various surfaces. Using nano-scaled particles, LSAO was uniformly disseminated without agglomeration in the silicone rubber matrix, enabling the produced nanocomposite glue to transmit light. For the applied glues, there is an excitation peak determined at 365 nm, and an emission peak determined at 518 nm. Depending on the LSAO ratio, the photoluminescence spectra displayed either afterglow phosphorescence or fluorescence. Photochromism was monitored from transparent to greenish under UV irradiation and greenish-yellow in darkness. The glued samples benefit from enhanced superhydrophobicity and scratch resistance due to LSAO NPs embedded in the silicone rubber matrix. The glueed LSAO@SR nanocomposite showed high durability and resistance to light damages. This research established the feasibility of mass-producing smart glue for various uses such as building safety directed signs and smart windows.

High ablation-resistant silicone rubber composites via nanoscale phenolic resin dispersion

High ablation-resistant silicone rubber composites exhibit significant potential for solid rocket engine ablation coating applications. However, the low char yield of silicone rubber restricts its real-world usage. Herein, silicone rubber with nanoscale dispersed Novolac-type phenolic resin particles (novolac-silicone rubber, NSR) is synthesized. The introduction of dynamic urethane bonds is crucial for achieving nanoscale dispersion of the phenolic resin, as it leads to both improved mechanical strength and enhanced char yield. In addition, the NSR-based composite materials demonstrate linear and mass ablation rates of 0.1440 mm/s and 0.0466 g/s, respectively, representing reductions of 44.19 % and 17.81 % compared with their conventional silicone rubber counterparts. Moreover, unlike the traditional physical blending approach, the nanoscale dispersion in this work is achieved by introducing a dihydroxypropyl-terminated silicone oil-novolac phenolic resin block copolymer to the silicone rubber matrix. The enhanced structural compatibility is proven to be pivotal for the improved performance of NSR. This work provides new routes for the synergistic improvement of the ablation resistance and mechanical properties of silicone rubber composites.