Carbon black–polybenzoxazine nanocomposites for high K dielectric applications

This work involves the development of surface functionalized carbon black (FCB) reinforced polybenzoxazine (PBZ) nanocomposites, using a benzoxazine monomer and varying weight percentages of functionalized carbon black (0.5, 1.0, and 1.5 wt%) through ring opening polymerization via thermal cure. Data from the morphological studies indicate that the nanosized FCB particles are homogeneously distributed in the polybenzoxazine matrix. The incorporation of FCB improves the dielectric constant, electrical conductivity, and reduction in resistivity of the resulting FCB–PBZ nanocomposites when compared to neat PBZ. A significant improvement observed in glass transition temperature and thermal stability of resulting FCB–PBZ nanocomposites, when compared to neat PBZ. POLYM. COMPOS., 35:2121–2128, 2014. © 2014 Society of Plastics Engineers     

Synthesis,characterization, and properties of flexible magnetic nanocomposites of cobalt ferrite–polybenzoxazine–linear low‐density polyethylene

A simple method for the preparation of magnetic nanocomposites consisting of cobalt ferrite (CF; CoFe₂O₄) nanoparticles, polybenzoxazine (PB), linear low‐density polyethylene (LLDPE), and linear low‐density polyethylene‐g‐maleic anhydride (LgM) is described. The composites were prepared by the formation of benzoxazine (BA)–CF nanopowders followed by melt blending with LLDPE and the thermal curing of BA. The composites were characterized by X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, universal testing machine measurement, and vibrating sample magnetometry. The composites consisting of LLDPE, PB, and LgM (47.5L–47.5PB–5LgM) exhibited a higher tensile strength (23.82 MPa) than pure LLDPE and a greater elongation at break (6.11%) than pure PB. The tensile strength of the composites decreased from 19.92 to 18.55 MPa with increasing CF loading (from 14.25 to 33.25 wt %). The saturation magnetization of the composites containing 33.25 wt % CF was 18.28 emu/g, and it decreased with decreasing amount of CF in the composite. The composite films exhibited mechanical flexibility and magnetic properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nonisothermal cure kinetics in the synthesis of polybenzoxazine–clay nanocomposites

The ability to understand and model the mechanism of cure kinetics accurately is crucial for the production of thermosetting resin‐based nanocomposites. This article reports on work performed to elucidate an accurate model of cure kinetics for the formation of polybenzoxazine–montorillonite nanocomposites through the use of differential scanning calorimetry with nonisothermal methods, including single‐heating and multiple‐heating methods. The results indicated that both the Kissinger and Ozawa methods for calculating the activation energy gave fairly close results of 115 and 120 kJ/mol, respectively. The reaction order was about 1.31, calculated from the single‐heating method based on the autocatalytic method, and a comparison was made of the dynamic curing behaviors in the syntheses of polybenzoxazine and polybenzoxazine–montorillonite nanocomposites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 194–200, 2003     

Synthesis and properties of BCDA‐based polyimide–clay nanocomposites

Bicyclo[2.2.2]oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride (BCDA)‐based polyimide–clay nanocomposites were prepared from their precursor, namely polyamic acid, by a solution‐casting method. The organoclay was prepared by treating sodium montmorillonite (Kunipia F) clay with dodecyltrimethylammonium bromide at 80 °C. Polyamic acid solutions containing various weight percentages of organoclay were prepared from 4,4′‐(4,4′‐isopropylidenediphenyl‐1,1′‐diyldioxy)‐dianiline and BCDA in N‐methyl‐2‐pyrrolidone containing dispersed particles of organoclay at 20 °C. These solutions were cast on a glass plate using a Doctor's blade and then heated subsequently to obtain nanocomposite films. The nanocomposites were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry, thermal mechanical analysis, dynamic mechanical analysis, polarizing microscopy, scanning electron microscopy, transmission electron microscopy, wide‐angle X‐ray diffraction (WAXD) and thermogravimetric analysis. The glass transition temperature of the nanocomposites was found to be higher than that of pristine polymer. The coefficient of thermal expansion of the nanocomposites decreased with increasing organoclay content. WAXD studies indicated that the extent of silicate layer separation in the nanocomposite films depended upon the organoclay content. Tensile strength and modulus of the nanocomposite containing 1% organoclay were significantly higher when compared to pristine polymer and other nanocomposites. The thermal stability of the nanocomposites was found to be higher than that of pristine polymer in air and nitrogen atmosphere. Copyright © 2007 Society of Chemical Industry     

Reactive melt blending of PS‐POSS hybrid nanocomposites

Hybrid nanocomposites of polystyrene (PS) and methacryl phenyl polyhedral oligomeric silsesquioxane (POSS) were synthesized by reactive melt blending in the mixing chamber of a torque rheometer using dicumyl peroxide (DCP) as a free radical initiator and styrene monomer as a chain transfer agent. The effects of mixing intensity and composition on the molecular structure and morphology of the PS‐POSS hybrid nanocomposites were investigated. The degree of POSS hybridization (α_POSS) was found to increase with the POSS content, DCP/POSS ratio, and rotor speed. For the PS‐POSS materials processed in the absence of styrene monomer, an increase in the α_POSS led to a reduction in the molecular weight by PS chain scission, as a consequence of the free radical initiation. On the other hand, the use of styrene monomer as a chain transfer agent reduces the steric hindrance in the hybridization reaction between POSS and PS, enhancing the degree of POSS hybridization and avoiding PS degradation. The PS‐POSS morphology consists of nanoscale POSS clusters and particles and microscale crystalline POSS aggregates. PS‐POSS with higher α_POSS values and lower amounts of nonbound POSS showed improved POSS dispersion, characterized by smaller interfacial thickness (t) and greater Porod inhomogeneity lengths (l_p). The processing‐molecular structure–morphology correlations analyzed in this study allow the POSS dispersion level in the PS‐POSS materials to be tuned by controlling the reactive melt blending through the choice of the processing conditions. These insights are very useful for the development of PS‐POSS materials with optimized performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure–property relationships in nylon 6 nanocomposites based on octaphenyl‐, dodecaphenyl–POSS,montmorillonite, and their combinations

Binary and ternary nanocomposites were produced by incorporating, via melt compounding, two types of octa‐ and dodecaphenyl substituted polyhedral oligomeric silsesquioxanes (POSS), montmorillonite (MMT), and combinations of POSS with MMT into nylon 6. The tensile, flexural, and dynamic thermo‐mechanical properties of these materials were characterized and their structure–property relationships discussed. The results show that the losses in ductility and toughness experienced after inclusion of MMT into nylon 6 can be balanced out by co‐mixing MMT with the dodecaphenyl–POSS to produce a ternary nanocomposite. This trend however was less pronounced in the ternary MMT/octaphenyl–POSS system. Analysis of the microstructure organization in these materials using XRD and SEM sheds some light on understanding the differences in behavior. Both types of POSS particles mixed alone in nylon 6 were found to be polydisperse (500 nm to a few microns in size) and locally aggregated, yielding materials with similar mechanical performance. The co‐mixing of MMT with the octaphenyl–POSS served to break down the POSS crystal aggregates, enhancing their micro‐mechanical reinforcing action. On the other hand, the POSS crystals were not affected in the MMT/dodecaphenyl–POSS system, which led to improving their toughening ability. POLYM. COMPOS., 36:153–160, 2015. © 2014 Society of Plastics Engineers     

Transparency and water vapor barrier properties of polybenzoxazine‐silica nanocomposites provided with perhydropolysilazane

Poly[6,6′‐(1‐methylethylidene)bis(3,4‐dihydro‐3‐2H‐1,3‐hexylbenzoxazine)] (PB‐hda)‐silica nanocomposites were synthesized with perhydropolysilazane (PHPS) and PB‐hda by ring opening polymerization in one step. Both high transparency and good water vapor barrier property (WVP) are required to be improved in the field of packing and electronic materials, such as OLED, solar cell, and electronic paper. PB‐hda has shown high toughness and high thermal stability. However, it became dark brown and showed a reduction of WVP with increasing curing temperature, which make it difficult to be applied to packing and electronic materials. In this study, we aim to improve transparency and WVP by addition of PHPS into PB‐hda matrix. It was found that nanocomposites showed the improvement of WVP and transparency owing to Si? O? C linkages between PB‐hda and PHPS. In particular, a nanocomposite with 1 wt % of silica showed the most significant improvement in terms of transparency and the WVP. These properties were found to be influenced by the thickness of the combined polymer‐silica layers that formed around the silica particles; these layers were thickest in the 1 wt % sample. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44238.     

Low dielectric and high thermal conductivity epoxy nanocomposites filled with NH2‐POSS/n‐BN hybrid fillers

Hybrid fillers of mono‐amine polyhedral oligomeric silsesquioxane/nanosized boron nitride (NH₂‐POSS/n‐BN) were performed to fabricate NH₂‐POSS/n‐BN/epoxy nanocomposites. Results revealed that the dielectric constant and dielectric loss values were decreased with the increasing addition of NH₂‐POSS obviously, but increased with the increasing addition of BN fillers. For a given loading of NH₂‐POSS (5 wt %), the thermal conductivities of NH₂‐POSS/n‐BN/epoxy nanocomposites were improved with the increasing addition of n‐BN fillers, and the thermal conductivity of the nanocomposites was 1.28 W/mK with 20 wt % n‐BN fillers. Meantime, the thermal stability of the NH₂‐POSS/n‐BN/epoxy nanocomposites was also increased with the increasing addition of n‐BN fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41951.     

Synthesis and characterization of polyurethane/polybenzoxazine‐based interpenetrating polymer networks (IPNs)

Sequential interpenetrating polymer networks (IPNs), based on polyurethane and polybenzoxazine, were synthesized. Fourier Transform infrared spectrometry was employed to monitor the formation kinetics, which indicated that only physical bonding existed in the resulting IPNs. Morphological investigations revealed a lightly phase separation behaviour in all of the IPNs studied. © 2003 Society of Chemical Industry     

Synthesis and characterization of linseed oil‐based nanocomposites

The nanocomposites from conjugated linseed oil, acrylic acid, and divinylbenzene are synthesized using modified montmorillonite clay and characterized for thermal properties. The wide angle X‐ray diffraction results clearly show the distortion of the platy nanolayers of the nanofiller in the polymer matrix as the peak due to the clay disappears in the nanocomposite samples. The dynamic mechanical analysis results show the enhanced storage modulus and transition temperature compared with the pristine polymer. At the glass transition temperature, the storage modulus of nanocomposites is in the range of 17–79 MPa, whereas the pristine polymer shows a storage modulus of 2.1 MPa. The melting peak temperature ranges from 230 to 260°C, which is further confirmed by thermogravimetric analysis (TGA) results. The samples are stable up to 200°C and show a two‐stage degradation. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Non‐isothermal crystallization kinetics of PEG plasticized PLA/G‐POSS nanocomposites

In this study, the non‐isothermal crystallization kinetics of epoxy functionalized poly(hedral oligomeric silsesquioxane) (G‐POSS) reinforced plasticized or unplasticized poly(lactic acid) (PLA) was investigated. Poly(ethylene glycol) (PEG) was used as plasticizer at a constant content of 10% by weight. A micro‐compounder was used to prepare PLA/G‐POSS, PLA/PEG, and PLA/PEG/G‐POSS nanocomposites. G‐POSS content was varied as 1, 3, 7, and 10 wt%. Avrami, Ozawa, and combined Avrami‐Ozawa kinetic models were implemented to understand the non‐isothermal crystallization behavior of aforementioned nanocomposites. Moreover, the nucleation activity of G‐POSS particles was investigated in terms of Dobreva and Gutzow models. The data for kinetic analysis were obtained through differential scanning calorimeter. It was found that the crystallization rate of both plasticized and unplasticized PLA nanocomposites increased with the addition of G‐POSS. It was highlighted that G‐POSS is an effective nucleating agent for plasticized and unplasticized PLA nanocomposites. In parallel, these findings were in good agreement with activation energies obtained from Friedman model. In addition, all kinetic results were supported by polarized optical microscopy. POLYM. COMPOS., 38:1378–1389, 2017. © 2015 Society of Plastics Engineers     

Synthesis and characterization of new reducing agent based on methylmethacrylate‐vinylpyridene copolymer–clay nanocomposites

Methylmethacrylate (MMA)‐vinylpyridine (VP) copolymer‐montmorillonite (MMT) nanocomposites were prepared, by direct interaction of sodium montmorillonite with various copolymers of MMA‐VP, using different ratios of VP. The interaction occurred through ion exchange between sodium cations in MMT and pyridinium ions in the copolymers. The resulting composites were reacted with lithium aluminum hydride forming the supported reagents. The structure of the resulting composites, as determined by elemental analysis, Infrared spectroscopy, and X‐ray diffraction, consisted of the insertions of MMA‐VP macromolecules between lamellar layers. Because of cooperative formation of electrostatic bonding the copolymers were strongly fixed to the inorganic surfaces. The absence of observable transition in the thermogram, using differential scanning calorimetry, confirmed the copolymer sandwiching between the inorganic layers. The thermal stability of nanocomposites was investigated by thermogravimetry analysis. The dispersion of the MMT particles in the polymer matrix was confirmed using scanning electron microscopy. The effectiveness of these materials has been examined in the reduction of potassium ferricyanide. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis and characterization of UV-cured epoxy acrylate/POSS nanocomposites

In this study, epoxy acrylate (EA)/vinyl-polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared through in situ polymerization and by UV-curing technique. The vinyl-POSS monomers were added to EA matrix by physically blending at loadings between 0 wt.% and 15 wt.%. The microstructure of the EA/vinyl-POSS composites was studied by X-ray diffraction (XRD) measurements, and the result indicated that the separate POSS domains were present in EA/POSS composites. Aggregates were observed in the nanocomposites by SEM and the EDS results indicated that there were vinyl-POSS molecules existing in the EA matrix. TEM images further proved there were both POSS aggregates and monomers dispersed in the EA matrix. The kinetics of the photopolymerization was investigated by real time FTIR spectroscopy. The DSC analysis showed that the increasing POSS content caused a decrease on the composite's glass transition temperature. TGA measures confirmed that the degradation mechanism of EA was not affected by POSS and the nanocomposites thermal stability was slightly improved with the increasing of POSS loadings. It can be seen that the degradation rate slowed down with the increasing of POSS content and the 50% mass loss temperature of EA/POSS hybrids all increased conspicuously relative to plain EA.     

Preparation of VB‐a/POSS hybrid monomer and its polymerization of polybenzoxazine/POSS hybrid nanocomposites

A benzoxazine monomer (VB‐a) containing an allyl groups was synthesized through the Mannich condensation of bisphenol A, formaldehyde, and allylamine (bisphenol‐A and allylamine as VB‐a). This monomer was then reacted with polyhedral oligomeric silsesquioxane (POSS) through hydrosilylation, followed by thermal curing to form poly(VB‐a)/POSS hybrid nanocomposites. The curing behavior of the nanocomposites was monitored using Fourier transform infrared spectroscopy (FTIR), and their thermal and morphological properties were investigated through thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and scanning electron microscopy. DMA revealed that the glass transition temperatures of the poly(VB‐a)/POSS nanocomposites were higher than that of the pristine poly(VB‐a), presumably because the POSS cages effectively hindered the motion of the polymer chains. TGA confirmed that the thermal degradation temperatures and char yields of the polybenzoxazines increased after incorporation of the POSS moieties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

New aramid‐based nanocomposites: Synthesis and characterization

New type of nanocomposites containing various proportions of montmorillonite in aromatic polyamide was prepared via solution intercalation method. Aramid chains were synthesized by reacting 4,4′‐oxydianiline with isophthaloyl chloride in N,N′‐dimethyl acetamide. Dodecylamine was used as swelling agent to change the hydrophilic nature of montmorillonite into organophilic. Appropriate amounts of organoclay were mixed in the polymer solution using high‐speed mixer for complete dispersion of the clay. Thin films cast from these materials after evaporating the solvent were characterized by XRD, TEM, mechanical, thermal, and water absorption measurements. The structure and morphology of the nanocomposites determined by XRD and TEM revealed the formation of exfoliated and intercalated clay platelets in the aramid matrix. Mechanical data indicated improvement in the tensile strength and modulus of the nanocomposites with clay loading up to 6 wt%. The glass transition temperature increased up to 12 wt% clay content and thermal stability amplified with increasing clay loading. The water absorption reduced gradually as a function of organoclay and approached to zero with 20 wt% organoclay in the aramid. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Synthesis of s‐triazine‐based hyperbranched polyurethane for novel carbon‐nanotube‐dispersed nanocomposites

s‐Triazine‐based hyperbranched polyurethanes (HBPUs) with different hard segments were synthesized by A₂ + B₃ approach. Various kinds of multiwalled carbon nanotube (MWNT) nanocomposites with HBPU were prepared to investigate an impact of hyperbranched polymer on dispersion of MWNTs in the polymer matrix and the resulting properties of nanocomposites. Synthesized HBPUs were characterized using FTIR and NMR measurements. The highly branched structures were found very effective in enhancing the pristine MWNT dispersion in the polymer matrix. As a result, the MWNT‐reinforced HBPU nanocomposites showed a steep increase in the yield stress and modulus and enhanced shape memory effect with an increase of hard segment and MWNT loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rheological behavior and mechanical properties of PVC/MAP‐POSS nanocomposites

The polyhedral oligomeric silsesquioxanes which contains methylacryloylpropyl groups (MAP‐POSS) was synthesized. The MAP‐POSS/PVC nanocomposites were prepared. The influences of composition, shear rate' shear stress on melting rheological behavior of MAP‐POSS/PVC nanocomposites were discussed. The dynamic mechanical properties, mechanical properties, and morphology were determined by DMA, material tester and SEM, respectively. The result shows that the plastic times decreases and melt viscosity increases with increasing MAP‐POSS content. The n has a maximal value at 5 wt% MAP‐POSS content, but have best impact strength at 3%. MAP‐POSS can use as process aid and impact aid of PVC at appropriate contents. POLYM. COMPOS., 31:1822–1827, 2010. © 2010 Society of Plastics Engineers.     

Structure–property relationship of polyimides based on pyromellitic dianhydride and short‐chain aliphatic diamines for dielectric material applications

Most polyolefins that are used for dielectric materials exhibit a low dielectric constant and operating temperatures up to 70°C. Polyimides offer a means to a higher dielectric constant material by the introduction of a polar group in the polymer backbone and are thermally stable at temperatures exceeding 250°C. A common dianhydride, pyromellitic dianhydride (PMDA), is reacted with various short‐chain diamines to produce polymers with high imide density. Homopolymers and copolymers synthesized had dielectric constants ranging from 3.96 to 6.57. These materials exhibit a dielectric constant twice that of biaxially oriented polypropylene and therefore a twofold increase in capacitance as well as maintaining low dissipation factors that are acceptable for this application. The experimental dielectric constants of these materials are also compared to density functional theory calculations and exhibit a close relationship. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1276‐1280, 2013     

Processing and characterization of epoxy–anhydride‐based intercalated nanocomposites

A study of the kinetic and thermal characterization of an epoxy resin (DGEBA) polymerized with a methyl tetrahydrophthalic anhydride reinforced with montmorillonite‐layered silicates is presented. The nanoreinforcement used was compatibilized by exchanging the cations between the silicate layers with alkylammonium salts, containing long hydrocarbon chains. The aim of this study was to develop new nanocomposites based on thermoset resins with improved thermal stability, suitable for electronic applications. Differential scanning calorimetry was used here to produce the polymerization kinetics data, while thermogravimetric analysis was used to evaluate the effects of the nanoreinforcements on the thermal stability and to analyze the degradation kinetics. Unexpected strong effects of the nanocomposite on the polymerization kinetics of the epoxy–anhydride system were detected and evaluated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2532–2539, 2003     

Development of wood‐substituted composites from highly filled polybenzoxazine–phenolic novolac alloys

Highly filled wood‐substituted composites from matrices based on polymer alloys of benzoxazine resin (BA‐a) and phenolic novolac resin using Hevea brasiliensis woodflour as a filler were developed. The results reveal that phenolic novolac resin can significantly reduce the curing temperature of the neat benzoxazine resin, thereby minimizing the degradation of woodflour filler during processing. The limiting oxygen indices (LOIs) of all the BP alloys were above the self‐extinguishable limit i.e. >26. In addition, the LOI values were found to moderately increase whereas the rate of burning decreased as the novolac fraction in the resin mixtures increased. Furthermore, a solvent resistance experiment and thermogravimetric analysis revealed that the suitable phenolic novolac content should not exceed 20 wt%, to avoid the presence of unreacted phenolic in the alloy networks. The outstanding mechanical performance of the resulting wood composites is attributed to the strong interfacial interaction between the BP alloys and the woodflour filler. POLYM. ENG. SCI., 47:140–149, 2007. © 2007 Society of Plastics Engineers