Preparation and characterization of novel polydimethylsiloxane composites used POSS as cross‐linker and fumed silica as reinforcing filler

A series of novel polydimethylsiloxane (PDMS) composites were prepared using octa[(trimethoxysilyl)ethyl]‐POSS (OPS) as cross‐linker and fumed silica as reinforcing filler. The cross‐linked networks, morphologies, thermal and mechanical properties of these novel PDMS composites were examined by attenuated total reflection infrared spectroscopy and the extraction/swelling experiment, scanning electron microscope, thermogravimetric analysis, and universal tensile testing machine, respectively. It was found that both the resistance to thermal degradation and mechanical properties of the novel PDMS composites were improved greatly by adding fumed silica. The prominent improvements in resistance to thermal degradation and mechanical properties of novel PDMS composites were likely attributed to the enhanced interaction of PDMS chains and aggregated particles resulted from synergistic effect between POSS and fumed silica. Meanwhile, we also found that the resistance to thermal degradation of the PDMS composites was lowered slightly with the further increment in loading fumed silica, but their mechanical properties were enhanced. The slight decrease in trend of the resistance to thermal degradation of the novel PDMS composites was likely ascribed to the increasing amount of hydroxyl groups resulting from fumed silica. And the improving mechanical properties were mainly attributed to the increasing interaction of PDMS chains and aggregated particles originated from synergistic effect between POSS and fumed silica. POLYM. COMPOS., 34:1041–1050, 2013. © 2013 Society of Plastics Engineers     

Influence of Polyhedral Oligomeric Silsesquioxanes (POSS) on Thermal and Mechanical Properties of Polydimethylsiloxane (PDMS) Composites Filled with Fumed Silica

A series of novel PDMS composites filled with a given amount of fumed silica were first prepared using divinyl-hexa[(trimethoxysilyl)ethyl]-POSS as cross-linker by hydrolytic condensation in the presence of organotin catalyst. The crosslinking reaction, the morphology, thermal behaviors and mechanical properties of the novel PDMS composites were characterized by attenuated total reflection infrared spectroscopy, scanning electron microscope, thermogravimetric analysis and universal tensile testing machine, respectively. It was found that the resistances to thermal degradation, thermo-oxidative decomposition of the novel PDMS composites were greatly improved by incorporation of POSS cross-linker, compared with that of the reference material (MT-1). Meanwhile, we also found that their thermal properties and mechanical properties were gradually enhanced with the further increment in loading amount of POSS cross-linker. The pronounced enhancements in thermal properties and mechanical properties of novel PDMS composites were likely attributed to the increasing interaction of PDMS chains and aggregated particles from synergistic effect between POSS and fumed silica.     

丁苯橡胶/高岭土纳米复合材料的性能

采用熔融共混法和乳液共混法制备了丁苯橡胶／高岭土纳米复合材料,研究了复合材料的分散性能、力学性能和热稳定性能。结果表明,高岭土在橡胶基体中具有良好的分散性。熔融共混法制备的复合材料的力学性能基本接近白炭黑填充橡胶,其热稳定性能明显优于白炭黑填充橡胶。随着纳米高岭土用量的增大,乳液共混法制备的复合材料的拉伸强度先增大后减小,且当纳米高岭土用量为40质量份时,复合材料的综合性能良好。     

Ultrasonic-Assisted Method for the Preparation of Carbon Nanotube-Graphene/Polydimethylsiloxane Composites with Integrated Thermal Conductivity,Electromagnetic Interference Shielding,and Mechanical Performances

Due to the rapid development of the miniaturization and portability of electronic devices, the demand for polymer composites with high thermal conductivity and mechanical flexibility has significantly increased. A carbon nanotube (CNT)-graphene (Gr)/polydimethylsiloxane (PDMS) composite with excellent thermal conductivity and mechanical flexibility is prepared by ultrasonic-assisted forced infiltration (UAFI). When the mass ratio of CNT and Gr reaches 3:1, the thermal conductivity of the CNT-Gr(3:1)/PDMS composite is 4.641 W/(m·K), which is 1619% higher than that of a pure PDMS matrix. In addition, the CNT-Gr(3:1)/PDMS composite also has excellent mechanical properties. The tensile strength and elongation at break of CNT-Gr(3:1)/PDMS composites are 3.29 MPa and 29.40%, respectively. The CNT-Gr/PDMS composite also shows good performance in terms of electromagnetic shielding and thermal stability. The PDMS composites have great potential in the thermal management of electronic devices.     

Influence of fly ash cenospheres on performance of coir fiber‐reinforced recycled high‐density polyethylene biocomposites

Recycled high‐density polyethylene (RHDPE)/coir fiber (CF)‐reinforced biocomposites were fabricated using melt blending technique in a twin‐screw extruder and the test specimens were prepared in an automatic injection molding machine. Variation in mechanical properties, crystallization behavior, water absorption, and thermal stability with the addition of fly ash cenospheres (FACS) in RHDPE/CF composites were investigated. It was observed that the tensile modulus, flexural strength, flexural modulus, and hardness properties of RHDPE increase with an increase in fiber loading from 10 to 30 wt %. Composites prepared using 30 wt % CF and 1 wt % MA‐g‐HDPE exhibited optimum mechanical performance with an increase in tensile modulus to 217%, flexural strength to 30%, flexural modulus to 97%, and hardness to 27% when compared with the RHDPE matrix. Addition of FACS results in a significant increase in the flexural modulus and hardness of the RHDPE/CF composites. Dynamic mechanical analysis tests of the RHDPE/CF/FACS biocomposites in presence of MA‐g‐HDPE revealed an increase in storage (E′) and loss (E″) modulus with reduction in damping factor (tan δ), confirming a strong influence between the fiber/FACS and MA‐g‐HDPE in the RHDPE matrix. Differential scanning calorimetry, thermogravimetric analysis thermograms also showed improved thermal properties in the composites when compared with RHDPE matrix. The main motivation of this study was to prepare a value added and low‐cost composite material with optimum properties from consumer and industrial wastes as matrix and filler. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42237.     

Mechanical,thermal, and viscoelastic response of novel in situ CTBN/POSS/epoxy hybrid composite system

The present study focuses on the preparation of a novel hybrid epoxy nanocomposite with glycidyl polyhedral oligomeric silsesquioxane (POSS) as nanofiller, carboxyl terminated poly(acrylonitrile‐co‐butadiene) (CTBN) as modifying agent and diglycidyl ether of bisphenol A (DGEBA) as matrix polymer. The reaction between DGEBA, CTBN, and glycidyl POSS was carefully monitored and interpreted by using Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). An exclusive mechanism of the reaction between the modifier, nanofiller, and the matrix is proposed herein, which attempts to explains the chemistry behind the formation of an intricate network between POSS, CTBN, and DGEBA. The mechanical properties, such as tensile strength, and fracture toughness, were also carefully examined. The fracture toughness increases for epoxy/CTBN, epoxy/POSS, and epoxy/CTBN/POSS hybrid systems with respect to neat epoxy, but for hybrid composites toughening capability of soft rubber particles is lost by the presence of POSS. Field emission scanning electron micrographs (FESEM) of fractured surfaces were examined to understand the toughening mechanism. The viscoelastic properties of epoxy/CTBN, epoxy/POSS, and epoxy/CTBN/POSS hybrid systems were analyzed using dynamic mechanical thermal analysis (DMTA). The storage modulus shows a complex behavior for the epoxy/POSS composites due to the existence of lower and higher crosslink density sites. However, the storage modulus of the epoxy phase decreases with the addition of soft CTBN phase. The T_g corresponding to epoxy‐rich phase was evident from the dynamic mechanical spectrum. For hybrid systems, the T_g is intermediate between the epoxy/rubber and epoxy/POSS systems. Finally, TGA (thermo gravimetric analysis) studies were employed to evaluate the thermal stability of prepared blends and composites. POLYM. COMPOS., 37:2109–2120, 2016. © 2015 Society of Plastics Engineers     

Synthesis and characterization of vinyl‐polyhedral oligomeric silsesquioxanes‐reinforced silicone resin with three‐dimensional cross‐linking structure

A novel thermal stability and highly transparent silicone resin‐type material was prepared via hydrosilylation of vinyl‐polyhedral oligomeric silsesquioxanes (POSS)‐grafted methylhydrosilicone oil and vinylmethylsilicone oil in the presence of Karstedt catalyst. The morphology, mechanical property, thermal stability, optical transmittance, thermal‐oxidation resistance of the vinyl‐POSS‐reinforced silicone resins were systematically investigated. Scanning electron microscopy showed that the vinyl‐POSS‐reinforced silicone resins had good compatibility with polydimethylsiloxane (PDMS) systems. The mechanical analysis and thermo gravimetric analysis indicated that the mechanical properties and thermal stability increased with increasing quantity of vinyl‐POSS. However, the optical transmittance increased with the increasing amount of vinyl‐POSS rather than decreased. In addition, the incorporation of vinyl‐POSS did not improve the thermal resistance of the PDMS polymers. The product has the potential application for LED packaging. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42187.     

Morphology and rheological behaviors of poly(ethylene terephthalate) nanocomposites containing polyhedral oligomeric silsesquioxanes

Poly(ethylene terephthalate) (PET)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared by in situ polymerization. Light scattering measurement suggested that there is significant change in molecular weight arising from gel formation by chemical crosslinking during polymerization. The thermal decomposition temperatures of the composites measured at 5 wt % weight loss were 5–10°C higher than that of PET. There is no significant change in other thermal properties. Scanning electron microscopy observations suggest that there is obvious phase separation in PET/POSS composites, composites containing 1 wt % of disilanolisobutyl and trisilanolisobytyl‐POSS show fine dispersions of POSS (30–40 nm in diameter), which arise from strong interfacial interactions between POSS and PET during polymerization. The viscosity of the composites increased with the addition of POSS. The observation of a plateau region of composites containing 1 wt % of POSS in the plot of log G′ vs. log G″ indicates strong interfacial interactions between POSS and PET. Sixty‐three percent and 41% increase in tensile strength and 300 and 380% increase in modulus were achieved in the composites containing 1 wt % of disilanol‐ and trisilanol‐POSS, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of blending sequence on the structure and properties of poly(vinyl chloride)/chicken eggshell powder composites

The effect of the blending sequence of poly(vinyl chloride)/chicken eggshell powder (PVC/ESP) composites on the processing, mechanical properties, morphology, and thermal decomposition were investigated. The compounding of composites was done by using a Rheomix mixture internal mixer at 180°C and a rotor speed of 30 rpm for 10 min to allow the mixing torque to reach a steady state. The mechanical and morphological properties of PVC/ESP composites under different blending sequences have been characterized by a lightweight tensile tester and scanning electron microscopy. The thermal stability and thermal analysis of the composites were performed by thermogravimetric and differential scanning calorimetric analysis. Good interfacial adhesion between filler and matrix in composites prepared via blending sequence 2 has improved the tensile strength and thermal stability of the PVC/ESP composite compared with blending sequence 1 as proved from scanning electron microscopy results on the tensile fracture surface of the composites. Thermogravimetric analysis results show that blending sequence 2 exhibited higher thermal stability comparable with blending sequence 1. In addition, the differential scanning calorimetric analysis results illustrate that the composites prepared via blending sequence 2 exhibit higher melting and crystallization temperature values compared with composites prepared via blending sequence 1. J. VINYL ADDIT. TECHNOL., 23:298–304, 2017. © 2015 Society of Plastics Engineers     

Epoxidized pine oil‐siloxane: Crosslinking kinetic study and thermomechanical properties

In this study, a novel approach to toughen biobased epoxy polymer with different types of siloxanes was explored. Three different modified siloxanes, e.g., amine‐terminated polydimethyl siloxane (PDMS‐amine), glycidyl‐terminated polydimethyl siloxane (PDMS‐glycidyl), and glycidyl‐terminated polyhedral oligomeric silsesquioxane (POSS‐glycidyl) were used as toughening agents. The curing and kinetics of bioepoxy was investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The mechanical, thermal, and morphological properties of the cured materials were investigated. Rheological characterization revealed that the inclusion of POSS‐glycidyl slightly increased the complex viscosity compared to the neat resin. The morphology of the cured bioresin was characterized by transmission electron microscopy and scanning electron microscopy. The inclusion of POSS‐glycidyl to bioepoxy resin resulted in a good homogeneity within the blends. The inclusion of PDMS‐amine or PDMS‐glycidyl was shown to have no effect on tensile and flexural properties of the bioresins, but led to a deterioration in the impact strength. However, the inclusion of POSS‐glycidyl enhanced the impact strength and elongation at break of the bioresins. Dynamic mechanical analysis showed that the siloxane modified epoxy decreased the storage modulus of the bioresins. The thermal properties, such as decomposition temperature, coefficient of linear thermal expansion, and heat deflection temperature were improved by inclusion of POSS‐glycidyl. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42451.     

Mechanical and film formation behavior from PDMS/NaY zeolite composite membranes

In this study, polydimethylsiloxane (PDMS) and NaY zeolite doped composite membranes were prepared for the films varying from 0 to 15 NaY zeolite wt %. All the membranes were characterized by attenuated total reflectance–Fourier transform infrared (FTIR), X-ray diffraction, scanning electron microscopy, thermogravimetry/differential thermal analysis methods. The FTIR spectral results showed that there is physical interaction existing between the PDMS matrix and NaY zeolite. Additionally, film formation from the pure PDMS and PDMS/NaY composites were investigated by photon transmission technique. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. The NaY zeolite added films led to the significant improvement in the mechanical properties that both the tensile strength and Young's modulus increased three times. Thermal properties of the films were also investigated and the addition of NaY zeolite into the PDMS matrix could significantly improve the thermal stability of the composite membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48549.     

Preparation and characterization of acrylic latex/nano‐SiO2 composites

Acrylic/nano‐silica composite latexes were prepared by blending via high shear stirring (SS) or ball milling (BM) and in situ polymerization (IS). For comparison, composites filled with micro‐silica were also prepared. The mechanical and optical properties of the polymers formed by the composite latex filled with nano‐ or micro‐silica were investigated using an Instron testing machine, by dynamic mechanical analysis, ultraviolet–visible spectrophotometry and transmission electron micrography. The results showed that SS and BM methods could obtain better nanocomposite latex and polymers than the IS method, characterized by better dispersion of nanoparticles, higher tensile strength and T_g for SS and BM than for IS. The increase in absorbance and reduction in transmittance of UV (290–400 nm wavelength) were observed as nano‐silica content increased, whereas the UV absorbance or transmittance basically were kept unchanged for the composites filled with micro‐silica. © 2002 Society of Chemical Industry     

Effect of silane integrated sol–gel derived in situ silica on the properties of nitrile rubber

Nitrile rubber/silica composites are prepared by a sol–gel process using tetraethoxysilane as precursor in the presence of γ‐mercaptopropyltrimethoxysilane as a silane coupling agent. Here, we follow a novel processing route where the silica particles are generated inside the rubber matrix before compounding with vulcanizing ingredients. The effect of in situ generated silanized silica on the properties of the rubber composite has been evaluated by studying curing characteristics, morphology, mechanical and dynamic mechanical properties. Enhanced rubber–filler interaction of these composites is revealed from stress–strain studies and dynamic mechanical analysis. Excessive use of silane shows an adverse effect on mechanical properties of the composites. Due to finer dispersed state of the in situ silica and enhanced rubber–filler interaction, the mechanical properties and thermal stability of the composites are improved compared to corresponding ex situ processed composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40054.     

Mechanical,thermal, and conductivity performances of novel thermoplastic natural rubber/graphene nanoplates/polyaniline composites

Conventional polymer blending has a shortcoming in conductivity characteristic. This research addresses the preparation of conductive thermoplastic natural rubber (TPNR) blends with graphene nanoplates (GNPs)/polyaniline (PANI) through melt blending using an internal mixer. The effect of PANI content (10, 20, 30, and 40 wt %) on the mechanical and thermal properties, thermal and electrical conductivities, and morphology observation of the TPNR/GNPs/PANI nanocomposites was investigated. The results showed that the tensile and impact properties as well as thermal conductivity of nanocomposite had improved with the incorporation of 3 wt % of GNPs and 20 wt % of PANI as compared to neat TPNR and reduced with further increase of the PANI content. It was observed that the GNPs and PANI acted as a critical component to improve the thermal stability and electrical conductivity of the TPNR/GNPs/PANI nanocomposites. The most improved conductivity of 5.22 E-5 S/cm was observed at 3 wt % GNPs and 40 wt % PANI. Variable-pressure scanning electron microscopy micrograph revealed the good interaction and distribution of GNPs and PANI within TPNR matrix at PANI loadings lower than 30 wt %. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48873.     

微滴乳液聚合制备PDMS/SiO2纳米复合材料

采用超声分散的方法,以少量八甲基环四硅氧烷(D₄)对硅溶胶粒子进行表面接枝改性。然后在改性硅溶胶存在下,以十二烷基苯磺酸(DBSA)为乳化剂兼催化剂进行D₄的微滴乳液聚合,得到聚硅氧烷(PDMS)/二氧化硅(SiO₂)纳米复合乳液。采用FTIR、TGA、纳米粒度仪、TEM和拉力机分别对样品进行了表征。结果表明:采用超声分散的方法,能够有效地实现硅溶胶粒子的表面改性。通过微滴乳液聚合得到的复合乳胶粒是聚合物包覆二氧化硅粒子的核壳结构形态。SiO₂的引入提高了有机硅复合膜力学性能,增强了热稳定性。     

Preparation of dynamically vulcanized thermoplastic elastomer nanocomposites based on LLDPE/reclaimed rubber

Dynamically vulcanized thermoplastic elastomers nanocomposites (TPV nanocomposites) based on linear low density polyethylene (LLDPE)/reclaimed rubber/organoclay were prepared via one‐step melt blending process. Maleic anhydride grafted polyethylene (PE‐g‐MA) was used as a compatibilizing agent. The effects of reclaimed rubber content (10, 30, and 50 wt %), nanoclay content (3, 5, and 7 wt %), and PE‐g‐MA on the microstructure, thermal behavior, mechanical properties, and rheological behavior of the nanocomposites were studied. The TPV nanocomposites were characterized by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy (SEM), differential scanning calorimeter, mechanical properties, and rheometry in small amplitude oscillatory shear. SEM photomicrographs of the etched samples showed that the elastomer particles were dispersed homogeneously throughout the polyethylene matrix and the size of rubber particles was reduced with introduction of the organoclay particles and compatibilizer. The effects of different nanoclay contents, different rubber contents, and compatibilizer on mechanical properties were investigated. Increasing the amount of nanoclay content and adding the compatibilizer result in an improvement of the tensile modulus of the TPV nanocomposite samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Liquid polyoctahedral silsesquioxanes as an effective and facile reinforcement for liquid silicone rubber

Acrylo polyoctahedral silsesquioxanes (POSS), a liquid POSS derivative with reactive C=C double bond, is used to modify addition-cured liquid silicone rubber (LSR) as an effective nanofiller for the first time. Significant enhancements on mechanical properties are obtained. With addition of only 1.5 parts per hundred rubbers (phr) of acrylo POSS to fumed silica-strengthened silicones, the Young's modulus and ultimate tensile strength are increased by 432% and 66%, respectively, and the hardness of resulting LSR composites is improved as well. Proton nuclear magnetic resonance and Fourier transform infrared spectroscopies prove the efficient hydrosilylation between Acrylo POSS and hydrosiloxane directly. The thermal stability and morphology investigations also confirm that POSS is covalently incorporated into the network of silicone rubber. The increment of crosslink density is proved by extraction and swelling experiment and dynamic mechanical analysis. It can be envisioned that this simple and effective method could help produce high performance silicone rubber composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46996.     

The effect of grafted caged silica (polyhedral oligomeric silesquioxanes) on the properties of dental composites and adhesives

With the emergence of commercial grafted caged silica (Polyhedral Oligomeric Silesquioxanes, POSS) having a three-dimensional (3D) morphology with peripheral functionality, new opportunities have been created for formulating dental adhesives and composites with enhanced mechanical and physical properties. The objective of the present study was to investigate the properties obtained by incorporating grafted caged silica into acrylate based dental composite and adhesive systems. Two commercial POSS materials (methacrylated and octaphenyl grafted) were added to dental restorative-glass-filled pre-polymers, based on BisGMA (bis-phenol A-glycidyldimethacrylate), HEMA (2-hydroxyethylmethacrylate) and TEGDMA (tetraethylglycidylmethacrylate). The nanostructured organic/inorganic hybrid compounds exhibited enhanced mechanical and thermal properties in cases where the POSS added was in concentrations up to 2 wt%. Beyond this threshold concentration, properties decreased due to agglomeration. In the case of the acrylated POSS, the T _g increased by 5°C, the composite compressive strength by 7%, and the bond shear strength by 36% and the shrinkage was reduced by 28% compared with neat dental composites and adhesives. Furthermore, in the case of octaphenyl grafted POSS, the compressive strength was reduced by 20%, the adhesive shear bond strength decreased by 49% and the shrinkage was reduced by 67%. It was concluded that the type of the grafted functional group of the caged silica was the dominant factor in nano-tailoring of improved dental composites and adhesives.     

Nanosilica as dry bonding system component and as reinforcement in short nylon‐6 fiber/natural rubber composite

Nanoscale silica was synthesized by acid hydrolysis of sodium silicate using dilute hydrochloric acid under controlled conditions. The synthesized silica was characterized by SEM, BET adsorption, and XRD. The particle size of silica was calculated to be 13 nm from the XRD results and the surface area was found to be 295 m²/g by BET method. This synthesized nanosilica was used in place of conventional silica in HRH (hexamethylenetetramine, resorcinol and silica) bonding system for natural rubber/Nylon‐6 short fiber composite. Nanosilica was also used as reinforcing filler in natural rubber/Nylon‐6 short fiber hybrid composite. Mechanical, thermal, and dynamic mechanical properties of the composites were evaluated. The introduction of the nanosilica in hybrid composites improved the tensile strength, modulus, and tear strength through improved interaction with the matrix which is facilitated by the higher surface area. Abrasion loss and hardness were also better for the nanosilica composites. Resilience and compression set were adversely affected. The hybrid composites showed anisotropy in mechanical properties. Peak rate of thermal decomposition decreased and temperature of initiation of thermal degradation increased with silica content, indicating improved thermal stability of the hybrid composites. The storage modulus and loss modulus showed two‐stage dependence on frequency at higher fiber loading. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polylactide/nano and microscale silica composite films. I. Preparation and characterization

Polylactide (PLA)/silica composite films were prepared by two methods: blending nanoscale colloidal silica sol and sol–gel. The nano and microscale silica particles, respectively, were well dispersed in PLA when observed using scanning electron microscopy and transmission electron microscope. The mechanical and thermal stability of composite films were measured before and after hydrolysis by Instron and thermogravimetric analysis. The fillers increase tensile strength, Young's modulus, thermal stability, and hydrolysis resistance with increasing silica content. The nanoscale particles exhibit better effects than the microscale ones. The activation energy, E_a, of thermal decomposition is also simulated by the Kissinger and Ozawa equation. The results also show that the thermal stability is increased by the incorporation of silica particles and is lowered by hydrolysis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009