Polybenzoxazine Matrix Research Articles

High thermal and mechanical properties enhancement obtained in highly filled polybenzoxazine nanocomposites with fumed silica

Highly filled polybenzoxazine nanocomposites filled with nano-SiO2 particles were investigated for their mechanical and thermal properties as a function of filler loading. The nanocomposites were prepared by high shear mixing followed by compression molding. A very low A-stage viscosity of benzoxazine monomer gives it excellent processability having maximum nano-SiO2 loading as high as 30wt% (18.8vol%) with negligible void content. Moreover, thermal analysis of the curing process of the compound of the PBA-a/nano-SiO2 composites was found to be autocatalytic in nature with average activation energy of 79–92kJmol−1. Microscopic analysis (SEM) performed on the PBA-a/nano-SiO2 composite fracture surface indicated a nearly homogeneous distribution of the nano-scaled silica in the polybenzoxazine matrix. In addition, the enhancement in storage modulus of the nano-SiO2 filled polybenzoxazine composites was found to be significantly higher than that of the recently reported nano-SiO2 filled epoxy composites. The dependence of the nanocomposites’ modulus on the nano-SiO2 particles content is well fitted by the generalized Kerner equation. Furthermore, the relatively high micro-hardness of the PBA-a/nano-SiO2 composites up to about 600MPa was achieved. Finally, the substantial enhancement in the glass transition temperature (Tg) of the PBA-a/nano-SiO2 composites was also observed with the ΔTg up to 16°C at the nano-SiO2 loading of 30wt%. The resulting PBA-a/nano-SiO2 composite is a highly attractive candidate as coating material in electronic packaging or other related applications.

Highly filled graphite polybenzoxazine composites for an application as bipolar plates in fuel cells

ABSTRACTHighly filled graphite polybenzoxazine composites as bipolar plate material for polymer electrolyte membrane fuel cell (PEMFC) are developed. At the maximum graphite content of 80 wt % (68 vol %), storage modulus was increased from 5.9 GPa of the neat polybenzoxazine matrix to 23 GPa in the composite. Glass transition temperatures (Tg) of the composites were ranging from 176°C to 195°C and the values substantially increased with increasing the graphite contents. Thermal conductivity as high as 10.2 W/mK and electrical conductivity of 245 S cm−1 were obtained in the graphite filled polybenzoxazine at its maximum graphite loading. The obtained properties of the graphite filled polybenzoxazine composites exhibit most values exceed the United States department of energy requirements for PEMFC applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3909–3918, 2013

Nanocomposites of polybenzoxazine and exfoliated montmorillonite using a polyhedral oligomeric silsesquioxane surfactant and click chemistry

In this study, an exfoliated montmorillonite was introduced into a benzoxazine matrix—prepared from paraformaldehyde, aniline, and phenol—to form polymer/exfoliated clay nanocomposites. Wide-angle X-ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, transmission electron microscopy, and contact angle measurements revealed the structures and thermal and mechanical properties of these polybenzoxazine/clay nanocomposites; the montmorillonite was exfoliated into nanoparticles (single sheets or layers) that were dispersed in the polybenzoxazine matrix. The incorporation of the exfoliated montmorillonite improved the polymer’s glass transition and thermal decomposition temperatures, mechanical properties, and surface hydrophobicity.

Preparation and properties of cardanol-based polybenzoxazine/SiO2hybrids by sol-gel technique

A new cardanol-based benzoxazine monomer containing a hydroxyl group (CBZ) was synthesized and characterized by FT-IR and 1H NMR spectroscopy. The formation mechanism of cardanol-based polybenzoxazine/SiO2 hybrids from CBZ and tetraethoxysilane (TEOS) by sol-gel technique was invested by FT-IR analysis. FT-IR and SEM confirmed that there were many SiO2 particles formed and embedded in the cardanol-based polybenzoxazine. A phase separation occurred when the ratio (wt) of TEOS to CBZ was not less than 3 : 5. TGA results illuminated the thermal stability and char yield of cardanol-based polybenzoxazine could be enhanced due to the formation of SiO2 particles in the polybenzoxazine matrix. Incorporation of SiO2 could improve the surface de-wetting and anti-ultraviolet properties of the films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Miscibility, Microstructure, and Thermal and Dielectric Properties of Reactive Blends of Dicyanate Ester and Diamine-Based Benzoxazine

This study discusses the miscibility, microstructure, and the thermal and dielectric properties of the reactive blends of dicyanate ester of bisphenol A and diamine-based benzoxazine. DSC and IR were applied to monitor the curing reactions of the reactive blends. Three reactions were observed in the curing reactions: the first is the cyclotrimerization of cyanate ester, producing the triazine structure; the second is the coreaction between the triazine structure and benzoxazine, forming alkyl isocyanurate and diphenyl ether linkages, followed by the further reaction of the isocyanurate linkage; and the third is the ring-opening of benzoxazine. The coreaction decomposes the polycyanurate structures and brings parts of the polycyanurate structures into the polybenzoxazine matrix. Thus, a miscible blend can be achieved in all compositions, as judged by the single composition-dependent Tg in the dynamic mechanical and thermal mechanical analyses. The experimental data also show that the dimensional stability ...

Heteronucleobase-functionalized benzoxazine: synthesis, thermal properties, and self-assembled structure formed through multiple hydrogen bonding interactions

In this study we prepared a new class of thymine (T)-functionalized polybenzoxazine (PBZ) through the Michael addition of T to a new acryloyl-functionalized [(3-phenyl-3,4-dihydro-2H-benzooxazin-6-yl)methyl acrylate]benzoxazine (PA-ac) monomer and subsequent polymerization. We used 1H and 13C nuclear magnetic resonance spectroscopy and Fourier transform infrared (FTIR) spectroscopy to confirm the chemical structure of this new monomer and then employed differential scanning calorimetry (DSC) and FTIR spectroscopy to study the curing behavior of the new PBZ. The presence of the strongly self-complementary, multiply hydrogen-bonded T units in the PBZ matrix significantly enhanced its thermal stability, as evidenced from DSC traces and thermogravimetric analyses. Transition electron microscopy and wide-angle X-ray diffraction data provided evidence for the self-assembly of the PBZ occurring through self-complementary multiple hydrogen bonding of its T units.

Benzoxazine-functionalized multi-walled carbon nanotubes for preparation of electrically-conductive polybenzoxazines

Functionalization of multi-walled carbon nanotubes (MWCNTs) has been carried out using benzoxazine-containing compound (BPA-FBz) and polymer (PFBz) as modifiers through Diels–Alder reaction. The benzoxazine-functionalized MWCNTs (MWCNT-FBz and MWCNT-PFBz) have been characterized with Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analyzer, and high-resolution transmission electron microscopy. MWCNT-FBz and MWCNT-PFBz are thermally cross-linkable nanomaterials and could be fabricated with press molding and other thermal-forming processes. The cross-linked pellets of MWCNT-FBz and MWCNT-PFBz show surface electrical conductivities of 0.05 S cm−1. Moreover, nanocomposites have also been prepared from BPA-FBz and MWCNT-FBz. The nanocomposites have shown high electrical conductivities (about 7 × 10−5 S cm−1) and good mechanical strength. The attractive properties have been attributed to the good compatibility between the polybenzoxazine matrix and MWCNT-FBz, as the benzoxazine groups of MWCNT-FBz could copolymerize with BPA-FBz in the preparation of nanocomposites.

Preparation and thermal properties of multiwalled carbon nanotube/polybenzoxazine nanocomposites

AbstractIn this study, we prepared nanocomposites comprising multiwalled carbon nanotubes (MWCNTs) and polybenzoxazine (PBZ). The MWCNTs were purified through microwave digestion to remove most of the amorphous carbon and metal impurities. After purification, MWCNTs were treated with H2SO4/HNO3 (3 : 1) to introduce hydroxyl and carboxyl groups onto their surfaces. Raman spectroscopy revealed the percentage of nanotube content improved after prolonged microwave treatment, as evidenced by the decrease in the ratio of the D (1328 cm−1) and G (1583 cm−1) bands. For the untreated MWCNTs, the ID/IG ratio was 0.56. After microwave treatment for 40 min, the value decreased to 0.29, indicating that the percentage of nanotube content improved. Dynamic mechanical analyses (DMAs) revealed that the storage moduli and the Tgs of the MWCNTs/PBZ nanocomposites were higher than that of the pristine PBZ. This is due to the nanometer‐scale MWCNTs restricting the motion of the macromolecular chains in the nanocomposites. Transmission electron microscopy (TEM) image revealed that the MWCNTs were well dispersed within the PBZ matrix on the nanoscale when the MWCNT content was less than 2.0 phr. The coefficient of thermal expansion (CTE) of the nanocomposites decreased on increasing the MWCNTs content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of Interaction between Transition Metal Oxides and Nitrogen Atoms on Thermal Stability of Polybenzoxazine

To investigate the interaction of transition metal oxides with polybenzoxazine and their influence on the thermal degradation mechanism of polybenzoxazine, transition metal oxides Y2O3, La2O3, Pr6O11, and Gd2O3 were added to benzoxazine monomer based on p-cresol and aniline to prepare polybenzoxazine composites. The chemical structures and final polymerization extent of polybenzoxazine and its composites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and differential scanning colorimetry (DSC). The molecular weights of these cured samples were determined by gel permeation chromatography (GPC). The influence of transition metal oxides on the thermal properties of polybenzoxazine matrix was investigated using dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), thermogravimetric analyzer interfaced with Fourier transform infrared spectroscopy (TG-IR), and (pyrolysis-gas chromatography-mass spectrometry) Py-GC-MS. The results show that transition metal oxides can form coordination interactions with the nitrogen atoms of polybenzoxazine. The coordination interaction can anchor the aniline and make the molecular weights of polybenzoxazine matrix increase, which delays evaporation of aniline during thermal degradation, improves the char yield at 800°C, and increases the glass transition temperatures (Tg) of polybenzoxazine composites.

Synthesis and characterization of benzoxazine resin-SiO 2 hybrids by sol-gel process: The role of benzoxazine-functional silane coupling agent

Sol-gel process has been used to incorporate silica nanoparticles into polybenzoxazine matrix to form polybenzoxazine-silica hybrids. The hybrids have been synthesized by the reaction of bisphenol A/aniline type benzoxazine monomer (BA-a) and tetraethoxysilane as precursor for silica nanoparticles. Triethoxysilane-functional benzoxazine monomer was also prepared from γ-aminopropyltriethoxysilane, phenol and paraformaldehyde, and has been used as silane coupling agent to improve the adhesion between polybenzoxazine matrix as organic domain and silica nanoparticles as inorganic domain. Differential scanning calorimetry (DSC) and FT-IR are used to study the polymerization behavior of benzoxazine monomer in the presence of silica nanoparticles over different temperature range. Dynamic mechanical analysis indicates that the coupling agent is very effective to increase the T g and the storage modulus of the hybrids. Thermogravimetric analysis also shows the thermal stability of neat polybenzoxazine matrix is improved by the inclusion of silica nanoparticles.

The co-curing process of a benzoxazine-cyanate system and the thermal properties of the copolymers

Investigations confirmed the co-reactions between oxazine rings and triazine rings formed a crosslinking network composed of triazine rings as part of the polybenzoxazine matrix. The copolymers have higher initial storage modulus compared to polycyanate ester and exhibit better thermal stabilities than the polybenzoxazine.

Preparation of polybenzoxazine–Ni–Zn ferrite magnetic nanocomposite and its magnetic property

The synthesis of a new type, high performance polybenzoxazine–ferrite nanocomposite has been reported. A simple aqueous solution based method was developed for preparation of several compositions of Ni1–xZnxFe2O4 (x=0.20–0.60) nanopowders using metal nitrates and EDTA. Benzoxazine monomer was prepared by employing a solvent less method using aniline, paraformaldehyde and bisphenol A as starting materials. Polybenzoxazine–ferrite nanocomposites were prepared by using a solvent casting method followed by thermal curing. The synthesised powders, monomer, polymer and the resultant composites were characterised by using thermogravimetric analysis and differential scanning calorimeter, surface area and pore size analyser, scanning electron microscope (SEM) and transmission electron microscope. X-ray diffraction spectra of the powders revealed the formation of single phase Ni–Zn ferrite, with average crystallite size of about 20–30 nm. Transmission electron microscopy micrographs confirmed the average ferrite particle size as ∼30 nm while SEM morphology showed a uniform dispersion of nanoferrite particles in the polybenzoxazine matrix. Room temperature magnetic properties of pure ferrite nanopowders as well as polybenzoxazine–ferrite nanocomposites were measured with a vibrating sample magnetometer.

High‐Performance Polybenzoxazine Nanocomposites Containing Multifunctional POSS Cores Presenting Vinyl‐Terminated Benzoxazine Groups

AbstractWe have prepared a new class of polybenzoxazine/POSS nanocomposites through the reactions of a multifunctional vinyl‐terminated VBa‐POSS with a VBa monomer at various compositional ratios. The incorporation of the silsesquioxane core units into the polybenzoxazine matrix significantly hindered the mobility of the polymer chains and enhanced the thermal stability of these hybrid materials. Increasing the POSS content in these hybrids improved their thermal and mechanical properties, relative to those of the neat polybenzoxazine, because of hydrogen bonding between the siloxane groups of the POSS core units and the OH groups of the polybenzoxazine moieties, as adjudged using FTIR spectroscopy. magnified image

Synthesis and characterization of polyhedral oligomeric silsesquioxane (POSS) with multifunctional benzoxazine groups through click chemistry

We prepared a new class of polybenzoxazine-POSS nanocomposites with network structures through thermal curing of multifunctional benzoxazine groups of POSS (OBZ-POSS), which was synthesized from octa-azido functionalized POSS (OVBN3-POSS) with 3,4-dihydro-3-(prop-2-ynyl)-2H-benzoxazine (P-pa) via a click reaction. Incorporation of the silsesquioxane core into the polybenzoxazine matrix could significantly enhance the thermal stability of these hybrid materials. For these nanocomposites, the POSS nanoparticles in the hybrids were improved their thermal properties with 2,2-bis(3,4-dihydro-3-methyl-2H-1,3-benzoxazine)propane (BA-m) and P-pa polybenzoxazine, analyzed via TGA analyses. In addition, the incorporation of the POSS led to the formation of an inorganic protective layer on the nanocomposite’s surface. Contact angle data provided positive evidence to back up this hypothesis that the incorporation of the POSS units would decrease the surface energy property. In addition, the low glass transition temperature of poly(4-vinyl pyridine) and polycarbonate thin films, which lack liquid resistance, could possess low surface free energy after modification with OBZ-POSS due to low temperature curing of this new compound.

Investigations on the cure chemistry and polymer properties of benzoxazine–cyanate ester blends

Thermosetting polymer blends composed of bisphenol A based benzoxazine (BA-a) and cyanate ester (BACY) were prepared via co-curing of benzoxazine with cyanate ester. DSC results manifested a multiple curing pattern with associated heat of reaction implying a co-reaction between oxazine moiety and cyanate group. The catalysis during the co-curing of blend was ascribed to the cycloaddition reaction between the two groups followed by the ring-opening of benzoxazine and cyclotrimerisation of cyanate ester. The spectral and analytical data supported the possibilities of further polymerization through the insertion of the phenolic OH of polybenzoxazine to cyanate group to form the intermediate iminocarbonate, which further induce curing of cyanate ester to form polycyanurate. A co-reacted network composed of triazine ring as a part of polybenzoxazine matrix is postulated. The co-reaction temperature diminished with increase in cyanate ester content in the blend. A single T g was observed in DMTA of the cured matrix that implied a linked homogeneous matrix containing both triazine and polybenzoxazine. This was substantiated by the TGA, DTA and SEM behavior of the cured polymer. The modulus of the cured blend was higher than those of the component resins of the blend. The co-reaction with cyanate ester enhanced the high temperature stability of polybenzoxazine.

Dielectric Properties Enhancement in Polybenzoxazine Composite at Multi-Frequency Range

This research proposed a novel nano barium strontium titanate (BST) powder- polybenzoxazine composite as a new dielectric material. In this work, the dielectric properties of a surface-treated BST powder-polybenzoxazine composite were studied. The surface of the BST powders were modified by using three different chemicals: 3-aminopropyl-trimethoxysilane, benzoxazine monomer and phthalocyanine. The distribution of the BST powders in the polybenzoxazine matrix was observed by SEM. The dielectric constants of the composites with a function of frequency (1 kHz–10 MHz) were investigated. It was found that the composites with modified BST powders showed good distribution in the polybenzoxazine matrix, and the dielectric constants were also much enhanced than those with untreated BST powders. In comparisons among the three modification methods, the composite with the silane coupling modified BST powder showed significantly in dielectric constant improvement while the composite with the benzoxazine and phthalocyanine modified BST powders displayed lower dielectric loss due to the modified powder dispersed well in the polybenzoxazine matrix.

Reinforcement of polybenzoxazine matrix with organically modified mica

AbstractNovel polybenzoxazine–clay hybrids were prepared by the in situ polymerization of the typical benzoxazine monomer, bis(3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (B‐a) in the presence of aminolauric acid‐modified mica (ALA‐mica). Various ratios of ALA‐mica were dispersed into solutions of B‐a in N,N‐dimethylacetamide, followed by casting into film form. The hybrids were thermally cured up to 230°C, affording transparent nanocomposite films up to 10 wt% of mica loadings. The cure behavior was monitored by both IR and differential scanning calorimetry, indicating the catalytic effect of the modified mica. The morphology of the nanocomposites was studied by XRD, showing a featureless pattern, which suggests the disordered dispersion of mica into polybenzoxazine matrix. The dynamic mechanical properties of some hybrids show that the nanocomposites have higher storage modulus over the whole temperature range than the neat polybenzoxazine. Thermogravimetric analysis results confirmed that the thermal stability and char yield of polybenzoxazine resin increased apparently by hybridization with mica corresponding to the mica content. POLYM. COMPOS., 28:680–687, 2007. © 2007 Society of Plastics Engineers

Multiwalled carbon nanotube/polybenzoxazine nanocomposites: Preparation, characterization and properties

A novel nanocomposite composed of polybenzoxazine (PBZ) and multiwalled carbon nanotubes (MWNT) was prepared successfully. The surface modification of MWNT, including nitric acid modification followed by toluene-2,4-diisocyanate (TDI) treatment, introduced hydroxyl, carboxyl, and isocyanate groups on the MWNT surface. The surface carboxyl groups catalyzed the ring-opening reaction of benzoxazine and thus decreased the curing temperature of the system. The isocyanate groups reacted with the phenolic hydroxyl groups generated by the ring opening of benzoxazine resulting in the significant improvement of the adhesion between PBZ and MWNT. Dynamic mechanical analyses indicated the increase of storage modulus as well as T g by the addition of MWNT into PBZ. A well dispersed modified-MWNT on nanoscale level inside PBZ matrix was observed by TEM and SEM.

Synthesis and characterization of polybenzoxazine networks nanocomposites containing multifunctional polyhedral oligomeric silsesquioxane (POSS)

A new class of polybenzoxazine/POSS nanocomposites with network structure is prepared by reacting multifunctional benzoxazine POSS (MBZ-POSS) with benzoxazine monomers (Pa and Ba) at various compositional ratios. Octafunctional cubic silsesquioxane (MBZ-POSS) is used as a curing agent, which is synthesized from eight organic benzoxazine tethers through hydrosilylation of vinyl-terminated benzoxazine monomer (VP-a) with octakis(dimethylsiloxy)silsesquioxane ( Q 8 M 8 H ) using a platinum complex catalyst (Pt-dvs). Incorporation of the silsesquioxane core into polybenzoxazine matrix could significantly hinder the mobility of polymer chains and enhance the thermal stability of these hybrid materials. For these nanocomposites, increasing the POSS content in the hybrids is expected to improve its thermal properties with respect to the neat polybenzoxazine. The morphology feature is useful to explain the thermal property changes ( T g and T d) and AFM images show that the presence of POSS aggregation in larger scales occurs at higher POSS contents. The reason of the heterogeneous phase separation may be from the less compatibility of the inorganic silsesquioxane core with organic benzoxazine species and the homopolymerization of MBZ-POSS. In the course of the formation of the polybenzoxazine/POSS hybrids, POSS particles were separated from the polybenzoxazine rich region, leading to POSS rich domains in the range of 50–1000 nm.

High performance wood composites from highly filled polybenzoxazine

AbstractHighly filled systems prepared by compression molding of Hevea brasiliensis woodflour filled polybenzoxazine composites with high mechanical properties and reduced water uptake has been developed. The effects of percent filler content and particle size of woodflour on the obtained composite's properties were examined. The low melt viscosity of BA‐a type polybenzoxazine allows substantial amount of woodflour to be easily incorporated into the composites. The results showed that mechanical properties from dynamic mechanical analysis and flexural test at filler content below the optimum filler packing show approximately linear relationship with filler loading. The outstanding compatibility between the woodflour and the polybenzoxazine matrix is evidently seen from the large improvement in the composite's Tg and char yield. Scanning electron micrographs of the composite also reveals substantially strong interface between the woodflour filler and the polybenzoxazine matrix. Water absorption of the composites is greatly reduced with increasing the amount of polybenzoxazine due to the inherent low water absorption of the matrix. The polybenzoxazine is; therefore, a highly attractive candidate as high performance lignocellulosic binder or adhesive and other related applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1240–1253, 2006