Octaphenylsilsesquioxane Research Articles

Enhancing the flame retardancy of polycarbonate through the synergistic effect of 1,3‐Benzenedisulfonate acid dipotassium salt and phenyl polysiloxanes

AbstractAs the application of polycarbonate (PC) in various fields continues to expand, the requirements for its flame retardancy are becoming increasingly stringent. To enhance the flame retardancy of PC, employing multi‐element synergistic effects and developing novel flame retardants are considered as vital strategies. This work introduces a blend of 1,3‐Benzenedisulfonic acid dipotassium salt (KSP) and three types of phenyl polysiloxanes, namely Octaphenylcyclotetrasiloxane (P4), Octaphenylsilsesquioxane (OPS), and ladder‐like Polyphenylsesquioxane (L‐PPSQ), into PC to create composites. The thermal stability and combustion properties of these composites were characterized using thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests. Composites with phenyl polysiloxanes achieved a UL‐94 V‐0 flame retardant rating for 1.6 mm thickness sample and reduced the peak heat release rate by 30%–45%. PC composites with 3% OPS and 0.03% KSP achieved optimal performance, howing a LOI of 34.5%, a 45.4% reduction in peak heat release, and a 40.5% reduction in total smoke release. The flame‐retardant mechanism was analyzed using scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and pyrolysis‐gas chromatography‐mass spectrometry (Py‐GC‐MS).

Synthesis of Sulfonated Phenylsilsesquioxanes Guided by Machine Learning.

Sulfonated octaphenylsilsesquioxane (SPOSS) has garnered significant interest due to its unique structural properties of containing the -SO3H group and its wide range of applications. This study introduces a novel approach to the synthesis of SPOSS, leveraging machine learning algorithms to explore new recipes and achieve higher -SO3H functionality. The focus was on synthesizing SPOSS with 2, 4, 6, and 8-SO3H functional groups on the phenyl group, marked as SPOSS-2, SPOSS-4, SPOSS-6, and SPOSS-8, respectively. The successful synthesis of SPOSS-8 was achieved by 5 training outputs based on the recipes of 21 sets of low-functionality (<4) SPOSS. The structure of SPOSS was confirmed using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and time-of-flight mass spectrometry (MALDI-TOF MS). Machine learning analysis revealed that K2SO4 is an important additive to improve the functionality of SPOSS. A synthetic mechanism was proposed and validated that K2SO4 participated in the reaction to generate sulfur trioxide (SO3), a sulfonating agent with high reactivity. SPOSS shows thermal stability superior to octaphenylsilsesquioxane (OPS) according to thermogravimetric analysis (TGA) and TG-FTIR.

Thermal stability and decomposition kinetics of polybenzoxazine and oligomeric polyhedral octaphenyl silsesquioxane nanocomposites

AbstractIn this study, the impact of octaphenyl polyhedral oligomeric silsesquioxane (POSS) on the thermal stability of polybenzoxazine resin at 1, 3, and 5 wt% POSS loading through dynamic thermogravimetric analysis (TGA) at heating rates of 10, 20, 30 and 40°C min−1 was investigated. Besides, the decomposition kinetics of polybenzoxazine resin (PBZ) and various nanocomposites were studied using Kissinger, Friedman, Flynn‐Wall‐Ozawa (FWO) and Coats‐Redfern (CR) models and also, the activation energies of samples were calculated. At first, benzoxazine monomer was synthesized and then nanocomposites were prepared via solution mixing method. The qualitative dispersion of nanoparticles in benzoxazine resin was examined through the utilization of scanning electron microscopy and x‐ray diffraction experiments. The results showed that the addition of nanoparticles improved the thermal stability of PBZ resin specially at 1 wt% POSS loading and at higher POSS content the thermal stability of the resin decreased. As determined by TGA, the char yield of resin was enhanced by 2.6% upon the addition of 1 wt% nanoparticles. In addition, in 1 weight percent of nanoparticles, as the heating rate rose from 10 to 40°C min−1, the Integral Program Decomposition Temperature (IPDT) has increased by about 260°C, and this increase is about 183°C compared to the resin, and also elevating the heating rate, Td (5%) and Td (10%) weight loss of samples shifted to higher temperatures. The degradation mechanism of the resin and nanocomposites was evaluated through Kissinger, Friedman, FWO and CR models. The results displayed that the addition of 1 wt% nanoparticles increased the activation energy (Ea) values of the nanocomposites compared to that of neat resin and above this filler content, the Ea values decreased. The findings derived from the FWO model indicated that the inclusion of a 1 wt% filler raised the Ea values of the first and second stages of PBZ resin decomposition from 136–200 and 151–214 kJ mol−1 to 148–210 and 180–228 kJ mol−1, respectively.

Reduced erosion and its erosion reducing mechanism of gun propellants by octaphenylsilsesquioxane

Low erosion high-energy propellant is one of the research directions to extend the weapon's life and improve the weapon's capability. In this study, energetic propellants containing different corrosion inhibitors were designed and prepared. Close bomb tests and semi-confined bomb experiments were used to investigate the burning and erosion properties of the propellants. The mechanism of erosion-reducing of titanium dioxide (titania, TiO2), talc, and octaphenylsilsesquioxane (OPS) on the propellant was comparatively analyzed. The results show that OPS has the lowest burning rate and the longest burning time, and a minimized loss of fire force, with the best effect of explosion heat reduction. The erosion reduction efficiency of OPS is twice that of TiO2 and talc. The mechanism analysis shows that the decomposition and heat absorption of OPS can effectively reduce the thermal erosion effect and carbon erosion, and the gas produced can reduce the loss of chamber pressure and form a uniformly distributed nano-SiO2 protective layer. This solid-state high-efficiency organosilicon erosion inhibitor is an important guide for designing high-energy low-erosion gun propellants.

Silicon Hybrid EPDM Composite with High Thermal Protection Performance.

The effects of octaphenylsilsesquioxane (OPS), fumed silica, and silica aerogel on the thermal insulation properties of ethylene propylene diene monomer (EPDM) rubber were studied. On this basis, two kinds of fillers with good performances were selected to study the thermal insulation of an EPDM full-formula system. The results show that the addition of fumed silica or silica aerogel had a positive effect on the thermal insulation performance of EPDM rubber and its composite. A 30 wt% silica aerogel can be well dispersed in the EPDM rubber system and with a lower thermal conductivity compared with fumed silica. EPDM composite with 23.4 wt% fumed silica can produce more char residues at 1000 °C than at 500 °C in a burn-through test and formed the compact and porous char at 1000 °C, which had a lowest thermal conductivity. EPDM composite with fumed silica cannot be burned through 1000 °C burning, and comparison with silica aerogel revealed that it achieved the lowest back temperature and had a temperature of 388 °C after 800 s.

Adaptive Multi‐Site Gradient Adsorption of Siloxane‐Based Protective Layers Enable High Performance Lithium‐Metal Batteries

AbstractLow Coulombic efficiency and significant capacity decay resulting from an unstable solid electrolyte interphase (SEI) and dendritic growth pose challenges to the practical application of lithium‐metal batteries. In this study, a highly efficient protection layer induced by octaphenylsilsesquioxane (OPS) with LiFSI salt is investigated. The OPS exhibits a strong adsorption energy with lithium, its multi‐site gradient adsorption ability enables the simultaneous capture of 8 Li+ and the uniform regulation of Li ion flux. Moreover, the mechanical strength and electronic insulation of the OPS layer induces Li deposition under the protection layer and effectively inhibits lithium dendrite growth. Such a protection layer contributes to the stable and dendrite‐free performance of a lithium‐metal battery employing LiNi0.8Co0.1Mn0.1O2 (NCM811) as a cathode and an ultrathin OPS‐protected lithium foil (20 µm) as the anode. A remarkable capacity retention of 91.4% is achieved after 300 cycles at 1C. The OPS‐protected Li anodes and NCM811 are also tested in combination with a Li1.5Al0.5Ge1.5(PO4)3 solid electrolyte, showing extended cyclability up to 300 cycles with an average Coulombic efficiency of 99.58% and capacity retention of 85.7%.

Microporous-micronucleus composite structure endowing heterogenous polyamide 6 with low-temperature toughness, low dielectric constant, fire retardancy and antibacterial activity

Utilizing the difference in compatibility and phase transition among PA6, monoglyceride (MG), octaphenylsilsesquioxane (OPS) and zinc diethylphosphinate (ZDP), a PA6 composite with microporous-micronucleus structure is simulated and designed. Due to the passivation micro-cracks effect of microporous-micronucleus structure, the MG/OPS/ZDP/PA6 composite exhibits excellent low-temperature impact strength (5.58 kJ m−2, 203.3% higher than neat PA6 at −170 °C). The nano-gap and nano-cage OPS endows the MG/OPS/ZDP/PA6 with low dielectric constant (2.95 at 100 Hz). The thermal insulation effect of micropores and the synergistic effect of OPS and ZDP in the micronucleus lead to the high flame retardancy of MG/OPS/ZDP/PA6. Meanwhile, the MG on the inner surface of the micropore and the ZDP in the micronucleus endow a dual antibacterial activity. This work provides a guideline for the construction of microporous-micronucleus structure to realize the functional design of composite.

Flame retardant polycarbonate with ultralow loading 1,3-benzenedisulfonate

Polycarbonate (PC) is one of the major engineering plastics. For the flame retardant PC, there are still obstacles to the development of high performance thin-walled PC. 1,3-Benzenedisulfonic acid dipotassium salt (KSP) was successfully synthesized by the electrophilic reaction of octaphenylsilsesquioxane (OPS) with excess chlorosulfonic acid (ClSO3H), and the structure of KSP was characterized using Fourier-transform infrared (FTIR), nuclear magnetic resonance (NMR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) measurements. PC/KSP composites with different KSP contents were prepared. It is obtained that the PC with only 0.01 wt% KSP exhibits superior flame retardant properties: the thin-walled PC (1.1 mm) sample reached UL-94 Vertical burn tests V-0 rating, the peak heat release rate (p-HRR) decreased by 16.2% and the limiting oxygen index (LOI) increased to 32.5%, while maintaining the mechanical properties. By analyzing the condensed-phase and gas-phase products during the thermal degradation of the PC/KSP composites, it is demonstrated that KSP can promote the early decomposition of PC into carbon and rapidly form a stable carbon layer to protect the internal substrate during combustion.

Molecular‐level fabrication strategies for the POSS cross‐linked polybenzoxazines

AbstractIn order to study the dispersion and compatibility of polysilsesquioxane (POSS) with different functional groups in benzoxazine resin, four different polysilsesquioxane/polybenzoxazine (POSS/PBZ) composites are prepared based on 3‐phenyl‐3,4‐dihydro‐2H‐benzoxazine (PHa), unreactive Octaphenylsilsesquioxane (OPS), Mercaptopropyl‐isobutyl silsesquioxane (SPOSS) containing one reactive sulfhydryl group, Aminopropyl‐isobutylsilsesquioxane (NPOSS) containing one reactive amino group and Octa (aminophenyl) silsesquioxane (OAPS) containing eight reactive amino groups, respectively. Scanning electron microscope (SEM), transmission electron microscope (TEM), and transmission electron microscope with probe corrector (AC‐TEM) are used to investigate compatibility. The results indicate that OAPS have very good compatibility and interaction with benzoxazine in the molecular level based on the microstructure. Besides, molecular and mesoscopic dynamic simulations (MesoDyn) also confirms OAPS and PHa have the best compatibility based on the micro and mesoscopic aspects. Then their properties of thermal stability and glass transition temperature (Tg) are identified by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. While OAPS is beneficial to increase the initial decomposition temperature (T5%) of PBZ by 26 °C and the Tg by 16 °C, comparing with pure PHa. However, NPOSS and SPOSS aggregate into micron‐sized silicon spheres, and OPS precipitates and deposits on the bottom of the resin, which could weaken the property of their thermal stability.

Cage‐shaped octaphenyl silsesquioxane with micro‐nano dispersibility for strengthening intumescent flame retardancy in polypropylene composites

AbstractIn this work, a silicon‐, phosphorus‐, nitrogen‐containing flame retardant system was constructed via the combination of the caged organic octaphenyl silsesquioxane (OPS) and an intumescent flame retardant (IFR) composed of piperazine pyrophosphate and melamine polyphosphate. Compared with the IFR mixture alone, the designed OPS/IFR system simultaneously endowed polypropylene (PP) with a higher charring flame‐retardant effect and better mechanical properties under the same loading amount. With only 0.5 wt% OPS and 19.5 wt% IFR in PP, both 3.2 mm‐ and 1.6 mm‐thick flame‐retardant composite reached UL 94 V‐0 level, while the sample with IFR only passed the 3.2 mm‐thick UL 94 V‐0 rating. Moreover, compared with IFR, OPS/IFR with a specific mass ratio also performed higher limited oxygen indexes, improved anti‐dripping behavior in the glow‐wire test, and suppressed the heat and smoke release to a larger extent of PP composite. The main mechanism was that a phosphorus/silicon synergistic charring effect occurred in PP composites during the combustion, thus forming more compact char layers with rich phosphorus/silicon compounds. The investigation of the multielement OPS/IFR system also disclosed a more effective flame retardant working way in PP through synergistic charring effect. Meanwhile, due to the mico‐nanoscale dispersibility of OPS in PP, the constructed composites kept higher mechanical performances compared with the sample loaded with IFR alone.

Analysis on the caged structure of polyhedral oligomeric dodecaphenyl silsesquioxane and its condensation mechanism

Polyhedral oligomeric dodecaphenyl silsesquioxane (DPS) and octaphenyl silsesquioxane (OPS) are two kinds of caged inorganic-organic hybrids and high thermal stable compounds. Concerning the caged structure of DPS, there remain some inconformity among researchers’ conclusions. Some researchers hold that the structure is in the shape of a gem containing 4 tetragons and 4 pentagons, while other articles consider the structure to be a cyclic ladder with 6 tetragons and 2 hexagons. In this paper, the correct structure of DPS is found to be gem‑like, deduced by detailed NMR spectra analysis and Euler's formula calculation, and proved by a single crystal diffraction pattern. A simulation calculation by Materials Studio (MS) proves that the gem‑like structure (Etotal=41.57 kcal·mol-1) is more stable than the cyclic ladder-like one (Etotal=43.37 kcal·mol-1). For the DPS and OPS, the distances between adjacent phenyl groups are considered to influence the chemical shifts of H, C and Si atoms in NMR due to shielding effects, deshielding effects and electron densities. The cyclic tetramer with Etotal=20.40kcal·mol-1 is proved to be the stable cyclic oligomeric phenyl silsesquioxanes with the smallest polymerization degree by the simulations. The linear dimer with Etotal=14.49 kcal·mol-1 is proved to be the stable linear oligomeric silsesquioxanes with the smallest polymerization degree. A condensation mechanism of DPS and OPS is proposed based on the simulation results.

PEEK composite resin with enhanced intumescent flame retardancy loaded with Octaphenylsilsesquioxane and nano calcium carbonate and its application in fibers

This study reported a novel strategy of introducing nano Calcium Carbonate (nCC) and Octaphenylsilsesquioxane (OPS) simultaneously into poly ether ether ketone (PEEK) as the intumescent flame retardants for the first time to address the melt flowage and drop in the fire. Good dispersion of nCC and OPS in the PEEK matrix was observed. The nanocomposites displayed lower thermal decomposition rate and higher residual chars compared with those of pristine PEEK. Cone calorimeter tests showed that the peak heat release rate, smoke production rate and the total smoke production of 5%OPS/5%nCC/PEEK decreased by 47.54%, 55.00% and 30.61%, respectively. Furthermore, the combustion mechanism of PEEK and its nanocomposite was investigated by TG-MS, which showed that nCC and OPS had a synergistic flame retardant effect. Finally, as an application verification, the PEEK nanocomposite fiber was prepared and its flame retardant properties were basically the same as the PEEK nanocomposite material, proving its huge application potential in high-performance flame retardant fabrics. This work is expected to pave the pathway about the novel eco-friendly flame retardancy and open a new avenue to develop PEEK nanocomposites.

Effect of polyhedral oligomeric silsesquioxane on combustion performance of HTPB propellants

HTPB-based (hydroxyl‑terminated polybutadiene) propellants containing aluminum and ammonium perchlorate (AP) were prepared with 1 wt% polyhedral oligomeric silsesquioxanes (POSS) and Fe2O3, respectively. The influences of POSS compounds on combustion performance of HTPB propellants were investigated. Four POSS compounds, octa (phenyl) silsesquioxane (OPS), octa (nitrophenyl) silsesquioxane (ONPS), octa (dinitrophenyl) silsesquioxane (ODNPS) and octa (aminophenyl) silsesquioxane (OAPS) were used. Their compatibility with the HTPB propellant components were tested by DSC analysis. Their combustion heats of and sensitivities were measured by oxygen bomb calorimeter and friction and impact tests, respectively. The results show that ODNPS and ONPS belong to low sensitive energetic compounds. The POSS compounds have good compatibility with the components of HTPB propellant. The burning rates of the HTPB propellants were measured in combustion chamber with transparent window under pressure. The combustion behaviors of the propellants under atmospheric pressure were recorded using high-speed camera. The condensed-phase combustion products were collected and studied through the SEM observation, XRD analysis and particle size measurements. The POSSs can increase the burning rates of HTPB propellants. With the ODNPS, the burning rate of HTPB propellant is similar to that of Fe2O3. The addition of the OPS, OAPS and Fe2O3 reduces the combustion heats of propellants, while with ONPS and ODNPS, the combustion heats are close to that of the HTPB propellant. POSS compounds can promote the combustion of aluminum in the propellants, inhibit the agglomeration of aluminum particles in the combustion process, and reduce the size of condensed phase products. These should correlate to the formation of the nano carbon layers from the POSS compounds in combustion of the propellants.

Mechanical and flame‐retardant properties and thermal decomposition of vinyl ester resin modified by different phenyl silsesquioxanes

The mechanical properties and fire resistance of vinyl ester resin (VER) composites containing cage‐shaped octaphenyl silsesquioxane (OPS), incompletely cage‐shaped phenyl silsesquioxane (PhT7POSS), and ladder‐shaped phenyl silsesquioxane (PPSQ) were investigated. The POSS structure and dispersion have a great influence on the mechanical properties, thermal stability, and decomposition process of VER composites. The bending strength at break and modulus of the VER‐POSS composites were enhanced obviously, especially for VER‐PPSQ composite and VER‐OPS composite, respectively. In addition, PhT7POSS‐based VER composites revealed the lower values of the peak heat release rate, total heat release, and total smoke release in cone calorimetry tests due to the formation of dense carbon/silica protective layers that acted as a barrier to heat and mass transfer. Moreover, the flame‐retardant mechanisms of condensed phase and gas phase were also investigated in detail. These results illustrate VERs modified by OPS, PhT7POSS, and PPSQ are providing an applicable method to fabricate the composites with excellent flame‐retardant and mechanical properties.

Mechanistic Insights into the Synthesis of Fully Condensed Polyhedral Octaphenylsilsesquioxane

Summary of main observation and conclusionA comprehensive study on the efficient one‐pot synthesis of polyhedral octaphenylsilsesquioxane (OPS) is reported via the hydrolytic condensation of phenyltrimethoxysilane (PTMS) in the presence of basic catalyst to investigate the specific synthesis mechanism. The synthetic reactions are monitored with real time infrared (RTIR) spectroscopy. Then RTIR coupled with 29Si nuclear magnetic resonance spectroscopy (NMR) and matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF‐MS) are used to monitor the reactions and identify the intermediary species during the reaction. The rapid hydrolysis of PTMS is detected by RTIR. Contrary to previous reports, the ladder‐like structured species are identified as intermediates during the reaction process. It is suggested that formation of caged T8 OPS is realized through the chain break and rearrangement of the ladder‐like phenyltrimethoxysilanes. Accordingly, a scheme from hydrolysis of the PTMS to formation of the OPS is provided.

Crystallization and flame‐retardant properties of polylactic acid composites with polyhedral octaphenyl silsesquioxane

To develop environmental‐friendly and flame‐retarded polymer composites, bio‐based polylactic acid (PLA) was loaded with thermally stable polyhedral octaphenyl silsesquioxane (OPS). Pure PLA and PLA/OPS composites with the OPS of 1, 3, 5, and 10 wt% were prepared by extrusion and injection molding, respectively. The scanning electron microscopy (SEM), polarized optical microscope (POM), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and thermal gravimetric analysis (TGA) were used to analyze the dispersion of the OPS in the PLA matrix and the effects of OPS on the crystallization and thermal stability properties of PLA/OPS composites, respectively. Limited oxygen index (LOI) and cone calorimeter (CONE) measurements were used to study flame retardancy of PLA and PLA/OPS composites. In order to study the flame‐retardant mechanism, the char residues were investigated by SEM, Fourier transform infrared spectra (FTIR), and X‐ray photoelectron spectroscopy (XPS). TGA‐FTIR was used to analyze the gaseous products of their thermal decomposition. The results show that the OPS particles were submicron in the PLA and could increase the crystallization rate of PLA and form small‐sized secondary α‐form crystalline compared with the pure PLA spherulite. The PLA and OPS decomposed individually in the PLA/OPS composites by TGA. According to the LOI tests, the PLA with the OPS loading exhibited very small reduction of LOI. However, the CONE tests indicated that the OPS could improve the flame retardancy of the PLA by means of low peak heat release rate and average heat release rate. It was obtained that the degree and type of the PLA crystalline for the pure PLA and PLA/OPS affect their flame retardancy. In the max thermal decomposition stage of PLA and PLA/OPS, their gaseous products were similar; at high temperatures, the PLA/OPS produced simple and clear gaseous products of PLA with solid SiO2 in the gas phase.

Covalent grafting of fluoride-encapsulating silsesquioxane F−@Ph8T8 onto glassy carbon

Covalent immobilization of fluoride-encapsulating octaphenyl silsesquioxane F−@Ph8T8 on glassy carbon (GC) was achieved using a new ambifunctional grafting agent, iodomethyltrimethylsilane TMSCH2I. This grafting method did not require any pre-grafting functionalization of the Ph-trimmed substrate; instead, the GC interface was anodically covered with CH2I groups whose ensuing reduction in the presence of F−@Ph8T8 resulted in the covalent grafting of the phenyl silsesquioxane cage onto the GC surface via the CH2 linker(s). The resulting ionic interface can be used to detect exposure to Li+- and H+-containing media. The proposed electrochemical process offers a general method for covalent binding of two (poly)aromatic substrates by a methylene bridge.

Preparation and Characterization of Polyhedral Octaphenylsilsesquioxane Modified Castor oil based Polyurethane

Vegetable oil-based polyurethanes were synthesized using castor oil (CO) as feedstock, which were characterized by their environmental friendly and renewable properties. Aiming to compensate for shortcomings of these materials, a series of polyurethane/polyhedral octaphenylsilsesquioxane (OPS) hybrids with different OPS contents were prepared by physical mixing in the solutions. Thereafter?chemical structure?morphology and thermal properties of hybrids were characterized through Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA), tensile test techniques and static contact angle. The results show that the hybrid polyurethanes display both enhanced glass transition temperatures (Tg), initial decomposition temperature (Td5) and tensile strength with low OPS contents. While with high contents?these values decline with the severe aggregation of nano-particles as shown in the SEM images. Meanwhile, the hybrid polyurethanes displayed enhanced surface hydrophobicity as the contact angle with water revealed

Rheological behavior of polycarbonate/ultrafine octaphenyl silsesquioxane (OPS) composites

ABSTRACTPolycarbonate (PC)/ultrafine polyhedral oligomeric octaphenyl silsesquioxane (OPS) composites were prepared by melt mixing method. The morphology and rheological behavior of PC/ultrafine OPS composites were investigated by scanning electron microscopy (SEM) melt indexer, high pressure capillary rheometer, and strain‐controlled rheometer. The SEM results show that ultrafine OPS is dispersed in PC as the size of submicron and has a good dispersion in PC matrix, and a certain extent compatibility between PC and ultrafine OPS is found. OPS aggregation is found through the cross section at high ultrafine OPS content. The results of melt flow index (MFI) and capillary rheometer indicate that ultrafine OPS can effectively decrease the apparent viscosity and improve the flow property and processability of PC matrix as a lubricant. The oscillatory rheological analysis indicates that the storage modulus increases with increasing OPS content, and the appeared platform of storage modulus exhibits the solid‐like behavior and the formation of three‐dimensional network in the composites. The complex viscosity of PC/OPS composite shows a quasi‐Newtonian regime at low OPS content and a typical shear‐thinning behavior at high OPS content. The Cole–Cole, Han, and van Gurp plots show that ultrafine OPS particle is compatible with PC at low content (≤3 wt %), and interaction between particle and particle is the major factor when OPS at high content (≥6 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43638.

Polyhedral oligomeric silsesquioxane/silica/polydimethylsiloxane rubber composites with enhanced mechanical and thermal properties

ABSTRACTComposites of polydimethylsiloxane (PDMS) rubber modified by three kinds of polyhedral oligomeric silsesquioxanes (POSSs) as well as fumed silica were prepared through solution blending and then open two‐roll mill blending with curing agent. Subsequently, the influences of POSS on mechanical and thermal properties of the resulting composites were investigated in detail. The addition of POSS significantly enhanced the tensile strength and elongation at break of the composite but lowered the tensile modulus, which could be ascribed to the interruption of silica–silica and silica–PDMS interactions. Octamethylsilsesquioxane (OMS)/silica/PDMS and octaphenylsilsesquioxane (OPS)/silica/PDMS composites did not show desirable mechanical and thermal properties. Nevertheless, heptaphenylvinylsilsesquioxane (VPS)/silica/PDMS composite with 5 wt % VPS exhibited enhanced glass transition temperature (Tg), mechanical properties, and thermal stability. Further studies revealed that more VPS unfavorably affected properties of the composite. Scanning electron microscope and X‐ray diffraction demonstrated that owing to the grafting reaction, 5 wt % VPS in the rubber matrix could form microcrystal domains the most effectively. Thus, the improved mechanical properties and thermal stability just resulted from the the formation of microcrystal domains and the increase in stiffness of PDMS chains because of the graft of VPS onto PDMS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42173.