Polybenzoxazine Composites Research Articles

High dielectric, low curing with high thermally stable renewable eugenol‐based polybenzoxazine matrices and nanocomposites

ABSTRACTIn the present work, a new type of bio‐based benzoxazines were prepared by using aniline, N, N‐dimethyl amino propyl amine (DMAPA) and caprolactam modified DMAPA with eugenol. The benzoxazines resulted were characterized for their molecular structure by Fourier transform infrared and nuclear magnetic resonance spectroscopy. The polymerization process of benzoxazines and their thermal behavior were studied by differential scanning calorimetry and thermogravimetric analysis, respectively. Moreover, the effect of chemical blending of the synthesized benzoxazines with conventional benzoxazines [bisphenol A benzoxazine (BPAb) and bisphenol F benzoxazine (BPFb)] and bismaleimide was studied to bring down the polymerization temperature by creating supplementary potential sites for polymerization. Furthermore, to reduce the polymerization temperature, the benzoxazines synthesized in the present study were partially incorporated with 10 wt % of catalysts (4‐hydroxy phenylmaleimide, 4‐amino phenol, and 4‐hydroxy acetophenone). The graphene reinforced polybenzoxazine composites were also prepared by incorporating varying weight percentages (1, 3, 5, 7, and 10 wt %) of graphene oxide to obtain hybrid nanocomposites. From the results obtained, it was observed that the polymerization temperature (Tp) was significantly reduced (more than 31 °C) in both the cases of blends of conventional BPAb and BPFb. It was also observed that the values of the dielectric constant of graphene reinforced hybrid composites are significantly enhanced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47050.

The influence of different chemical treatments on the hemp fiber/polybenzoxazine based green composites: Mechanical, thermal and water absorption properties

This study aims to evaluate the influence of cyclohexane/ethanol, alkali, and silane treatments on the waste hemp fibers and their polybenzoxazine composites. The Fourier transform infrared (FTIR), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) tests were carried out to understand the influence of treatments on the fibers. FTIR results revealed that hemicellulose and lignin of the fibers were removed after washing with cyclohexane/ethanol, and thermal stability of the fibers was improved after the alkali and silane treatments. The consequences of the treatments on the hemp fiber composites were studied by evaluating the mechanical, thermomechanical, thermal, and water uptake properties. The flexural, tensile and impact tests results confirmed that the silane treated fiber composites displayed highest properties than the other treated fiber composites. Furthermore, the stiffness and glass transition temperature of the silane treated fiber composites were also best among the studied composites. Moreover, the thermal stabilities values showed the lowest decline for the silane treated composites; due to the better thermal stability of the silane treated fibers, and lowest water absorption was also recorded for the silane treated fiber composites. The morphological studies confirmed that the silane treated fiber composite had stronger fiber/matrix adhesion interface.

Toughening effect and mechanism of polyamide 12 and modified montmorillonite in polybenzoxazine resin

Abstract The mechanical properties of polybenzoxazine (PBa) resins were improved by adding polyamide 12 (PA12) and modified montmorillonite (OMMT) as additives. The mechanical properties and thermal stability of PBa and resulting PBa composites were investigated using an Instron universal material testing instrument and dynamic mechanical analysis. The morphologies of the fracture surfaces were characterized by scanning electron microscopy. The results of morphological studies showed that PBa/PA12/OMMT composites exhibit significantly improved mechanical properties and thermal stability compared with that of the pristine PBa. When the OMMT content increased to 1 wt%, the fracture toughness (1.36 MPa·m1/2) and the fracture energy (G IC, 315.76 J·m−2) of PBa/PA12/OMMT-1 composites increased by 67.9% and 181.4%, respectively, compared with those of the pristine PBa. The thermal stability properties demonstrated that the storage modulus and glass transition temperature (T g) of PBa/PA12/OMMT composites gradually increased with the addition of OMMT particles. The scanning electron microscopy results indicated that PBa/PA12/OMMT composites possess a toughening mechanism of crack deflection, with a large bulk of voids and debonding induced by PA12 and OMMT clay particles. Moreover, the OMMT might provide microvoid nucleating sites at its surface to release constrains for shear yielding.

Development of Biocomposites from Agro Wastes for Low Dielectric Applications

The present work is attempting to synthesize and characterizations of a novel carbazole core containing cardanol based benzoxazine monomer from carbazole core containing aromatic diamine, cardanol and paraformaldehyde. In addition, carbazole core containing cardanol based benzoxazine polymer and various weight percentages of amine functionalized rice husk ash incorporated carbazole core containing cardanol based polybenzoxazine composites were prepared. The prepared polymer and its composites were characterized by FTIR, XRD, DSC, TGA and dielectric studies. The various studies confirm that the composites show increased Tg, higher char yield and better thermal stability compared to carbazole core containing cardanol based benzoxazine polymer. In addition to that the composites show significant decrease in the dielectric constant values than the neat cardanol based polybenzoxazine. The surface morphology and the distribution of rice husk ash in carbazole core containing cardanol based polybenzoxazine composites are confirmed by SEM and TEM analysis. Hence, the present study has attempted to prepared eco-friendly value added carbazole core containing cardanol based polybenzoxazine products for low dielectric constant applications by making use of biowaste for both matrix and reinforcement preparation to form biowaste based composites. Schematic representation for the preparation of carbazole core containing cardanol based benzoxazine monomer, polybenzoxazine and biobased polybenzoxazine composites

Effect of gamma irradiation on properties of ultrafine rubbers as toughening filler in polybenzoxazine

Three types of ultrafine fully vulcanized powdered rubbers (UFRs), i.e. natural rubber (NR), carboxylated nitrile-butadiene rubber (XNBR), and carboxylated styrene-butadiene rubber (XSBR) were prepared by combined technology between gamma irradiation for crosslinking and spray drying. The effects of doses in a range of 0–250 kGy on swelling ratio, crosslink density, and thermal stability of UFRs were investigated. Smaller particle size of UFRs was obtained at higher dose. A decrease in the swelling ratio and an increase in crosslink density were well corresponded to crosslinking effect related with absorbed dose. The increase in dose was also found to improve thermal performance of URFs. The influence of irradiated UFRs on impact resistance and glass transition temperature (Tg) of polybenzoxazine composites was also evaluated. The highest impact resistance of the composites belonged to the composite filled with irradiated UFXNBR at 200 kGy. While the significantly enhanced Tg of the composite was obtained by an addition of irradiated UFRs with higher doses, i.e. Tg = 173 °C for the composite filled with irradiated UFXNBR at 250 kGy. As a consequence, the UFRs can be used to effectively modify thermal and mechanical properties, especially impact resistance of polybenzoxazine composites.

Novel glass fabric-reinforced polybenzoxazine–silicate composites with polyvinyl butyral for high service temperature applications

The aim of this study is to develop novel glass fabric-reinforced polybenzoxazine–silicate composites with enhanced performances, which can overcome the disadvantages related to the low crosslink density of glass fabric-reinforced polybenzoxazine composites.

Impacts of hemp fiber diameter on mechanical and water uptake properties of polybenzoxazine composites

The waste hemp fibers (HF) were alkali treated; then shredded, ball milled, and sieved. The 20, 40, and 80mesh collected HF was reinforced in polybenzoxazine. The effects of fiber diameter and vol.% loading on tensile, impact, flexural and water uptake properties of composites have been studied. On 30 vol.% loading of 20mesh HF, an increase of 91%, 43%, 168%, 137%, and 73% in tensile strength, flexural strength, impact strength, tensile modulus, and flexural modulus, respectively. The additional enhancement was observed in all mechanical properties as fiber diameter was reduced from 311.5±42.9 to 198.3±40.7μm (20–80mesh). The similar behavior was confirmed by Halpin-Tsai model. The water uptake was also increased as vol.% loading increased and HF diameter decreased, 28.2% higher water uptake was observed on 20 vol.% loading as the diameter was reduced from 20 to 80mesh.

Reinforcement of waste hemp fibres in aromatic diamine-based benzoxazine thermosets for the enhancement of mechanical and thermomechanical properties

ABSTRACTNatural fibres (NFs) have been successfully reinforced in polymer matrices to strengthen the properties of the polymers. The polybenzoxazine thermosets are facing instable mechanical properties due to the high brittleness, herein, waste hemp fibres (WHF) reinforced polybenzoxazine composites are prepared. Effects of WHF volume % loading on curing, thermomechanical, mechanical, and thermal properties are studied. FTIR results confirmed that WHF rich in −OH groups increased the ring-opening of oxazines and reduced curing temperature. In addition, an increase of 223%, 111%, 64%, and 253% in impact, tensile strength, flexural and Young's modulus, respectively, were recorded after loading optimum concentration (30 vol. %) in composites. Considerable enhancements were also seen in the thermomechanical properties on optimum loading, double stiffness and 26°C increase was recorded in the glass transition temperature. Nonetheless, the decline was observed in thermal stabilities, T5% and Yc were 24°C and 1.4 % lower, respectively, than neat poly(P-ddm).

Formulation and Manufacturing of Polybenzoxazine Composites

Polybenzoxazines offer excellent properties regarding mechanical performance, chemical stability, good flame resistance and low water absorption. High curing temperatures of benzoxazine monomers, however, impede the processing of composites. Therefore, this contribution presents a formulation of polybenzoxazines with the aim to reduce the curing temperature and facilitate Out of Autoclave (OoA) oven processes. This is accomplished by copolymerizing benzoxazine monomers with a poly(ε-caprolactone) based plasticizer yielding a resin exhibiting viscosities and reduced curing temperatures suitable for a vacuum infusion as well as compression process. Air void free composites were manufactured successfully featuring temperature dependent mechanical behavior.

Catalytic effect of exfoliated zirconium phosphate on the curing behavior of benzoxazine

In this paper, the effects of α-zirconium phosphate (i.e., α-ZrP) on the thermal curing of bisphenol A‐based benzoxazine (Ba) was studied by preparing resin systems consisting of Ba and α-ZrP (Ba/α-ZrP). The thermal curing behavior and mechanism of Ba/α-ZrP were investigated by differential scanning calorimetry (DSC) and in-situ Fourier transform infrared spectroscopy (in situ FTIR). The curing kinetics of Ba and Ba/α-ZrP were investigated by non-isothermal DSC. In situ FTIR results revealed that the addition of α-ZrP accelerated the curing process of Ba. The apparent activation energy (E) of Ba and Ba/α-ZrP gradually increased with the extent of the curing process (α). The thermal stability and flame resistance properties of the polybenzoxazine (PBa) system were investigated by thermogravimetric (TGA) and microscale combustion calorimetry (MCC) analyses. These techniques revealed that the incorporation of α-ZrP was very efficient in improving the thermal stability and flame retardance of the PBa composite.

Synthesis and characterization of cardanol based fluorescent composite for optoelectronic and antimicrobial applications

The present study attempted to prepare para phenylene diamine functionalized multiwalled carbon nanotube (f-MWCNT) incopoarated polymer of a new pyrene core containing cardanol based benzoxazine (PyCBz) composite (f-MWCNT-PPyCBz). For this, a new monomer of pyrene core containing cardanol based benzoxazine (PyCBz) was synthesized through solventless method and its structure was confirmed using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (1H &13C) and MALDI mass. In addition, multiwalled carbon nanotube (MWCNT) was functionalized using para phenylene diamine that acted as effective filler for preparation the composite materials. The curing behavior and thermal stability of para phenylene diamine functionalised multiwalled carbon nanotube (MWCNT) incopoarated pyrene core containing cardanol based polybenzoxazine(PPyCBz) composites were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Antimicrobial studies were also carried out using Streptococcus pyogens, Bacillus cereus, Staphylococcus aureus and Escherichia coli. In short, the obtained f-MWCNT/PPyCBz nanocomposites possess high dielectric constant, good antibacterial and photo luminescent properties, which may find optical, antimicrobial and high dielectric applications.

Investigation on Rubber-Modified Polybenzoxazine Composites for Lubricating Material Applications

Effects of liquid amine-terminated butadiene-acrylonitrile (ATBN) on the properties of bisphenol-A/aniline-based polybenzoxazine (PBA-a) composites were investigated. Liquid ATBN decreased gel time and lowered curing temperature of the benzoxazine resin (BA-a). The PBA-a/ATBN-based self-lubricating composites resulted in substantial enhancement regarding their tribological, mechanical, and thermal properties. The inclusion of the ATBN at 5% by weight was found decreasing the friction coefficient and improved wear resistance of the PBA-a/ATBN composites. Flexural modulus and glass transition temperature of the PBA-a composite samples added the ATBN was constant within the range of 1-5% by weight. A plausible wear mechanism of the composites is proposed based on their worn surface morphologies. Based on the findings in this work, it seems that the obtained PBA-a/ATBN self-lubricating composites would have high potential to be used for bearing materials where low friction coefficient, high wear resistance, and modulus with good thermal property are required.

Thermal and Mechanical Properties of Acrylonitrile-Butadiene Rubber Modified Polybenzoxazine as Frictional Materials

Frictional composites based on polybenzoxazine (PBA-a) and acrylonitrile-butadiene rubber (NBR) are developed in this study. Mechanical, thermal and tribological properties of the PBA-a/NBR composites at 0, 2, 5, 10 and 15wt% of NBR particle contents are evaluated. Curing behaviors of the NBR-benzoxazine molding compounds are examined by differential scanning calorimetry to show an exothermic peak of about 222°C compared with that of the benzoxazine resin, i.e. 232°C suggesting curing acceleration of the benzoxazine resin due to the presence of the NBR particles. The storage modulus of the NBR-filled PBA-a is observed to systematically decrease from 5.2 GPa of the neat PBA-a to 2.8 GPa with an addition of 15wt% of the rubber particles. Glass transition temperature (Tg) of the composites evaluated by dynamic mechanical analysis increases with increasing of NBR particle contents, i.e. from 172°C for PBA-a to 186°C for PBA-a/15wt% NBR. Furthermore, the friction coefficients of the composites with 2wt% NBR are determined to be 0.603 for static type and 0.528 for kinetic type. Those values are improved from the value of 0.597 and 0.475 for unmodified polybenzoxazine, respectively. Therefore, the obtained outstanding properties, i.e. storage modulus, glass transition temperature and friction coefficient make the polybenzoxazine composites highly attractive to be utilized as friction materials.

Studies on graphene oxide–reinforced polybenzoxazine nanocomposites

In the present work, different weight percentages (1, 3, and 5 wt%) of benzoxazine-functionalized graphene oxide (FGO) were reinforced with polybenzoxazine (PBZ) matrix by means of ring-opening polymerization. The resulting nanocomposites were characterized for their thermal, mechanical, dielectric, and optical properties using different analytical techniques. From the results of these studies, it was observed that the 5 wt% FGO-reinforced PBZ composite shows an improved glass transition temperature, thermal stability, and dielectric constant to the extent of 18%, 39%, and 197%, respectively, when compared with those of neat PBZ matrix. Furthermore, 5 wt% FGO-reinforced PBZ composite also exhibits an enhanced ultraviolet shielding efficiency (88%), with improved tensile strength (52%) compared with those of neat PBZ matrix. The enhanced properties may be due to homogeneous and uniform distribution of FGO into the PBZ matrix, which was confirmed from scanning electron microscopic and high-resolution transmission electron microscopic images. Data obtained from these studies indicate that the developed nanocomposites with high dielectric constant can be used in the form of coatings, sealants, and encapsulates for high-performance dielectric as well as antistatic applications.

Synthesis and characterization of new polybenzoxazines from renewable resources for bio‐composite applications

Renewable natural resources such as eugenol, furfurylamine, stearylamine, and jute fiber were used to prepare polybenzoxazine composites. The purity of eugenol which is extracted from clove was confirmed by gas chromatography. FTIR, 1H, and 13C NMR spectroscopic analysis were used to determine the structure of eugenol and the benzoxazine monomers namely 6‐allyl‐3‐furfuryl‐8‐methoxy‐3,4‐dihydro‐2H‐1,3‐benzoxazine (EF‐Bz) and 6‐allyl‐3‐octadecyl‐8‐methoxy‐3,4 dihydro‐2H‐1,3‐benzoxazine (ES‐Bz) synthesized from it. The curing analysis from differential scanning calorimetric analysis shows that the onset of curing is shifted to lower temperature (161°C) for EF‐Bz, when compared with ES‐Bz (174°C). The thermal stability analyzed from thermogravimetric analysis shows that the polybenzoxazine EF‐Pbz has higher thermal stability (T5% = 361°C) with that of ES‐Pbz (T5% = 313°C). The storage modulus, tensile, and flexural strength of the EF‐Bz/Jute fiber composite show high value when compared with ES‐Bz/Jute fiber composites. POLYM. COMPOS., 37:1821–1829, 2016. © 2014 Society of Plastics Engineers

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.

Flammability and thermomechanical properties of dianhydride-modified polybenzoxazine composites reinforced with carbon fiber

Composites based on carbon fiber (CF) and benzoxazine (BA-a) modified with PMDA were investigated. The flammability of the carbon fiber composites was examined by limiting oxygen index (LOI) and UL-94 vertical tests. The LOI values increased from 26.0 for the CF/ poly(BA-a) composite to 49.5 for the CF-reinforced BA-a/PMDA composites as thin as 1.0 mm and the CFreinforced BA-a/PMDA composites were also achieved the maximum V-0 fire resistant classification. Moreover, the incorporation of the PMDA into poly(BA-a) matrix significantly enhanced the Tg and the storage modulus (E’) values of the CF-reinforced BA-a/PMDA composites rather than those of the CF/poly(BA-a). The Tg values and storage moduli of the obtained CF-reinforced BA-a/ PMDA composites were found to have relatively high value up to 237 � C and 46 GPa, respectively. The CFreinforced BA-a/PMDA composites exhibited relatively high degradation temperature up to 498 � C and substantial enhancement in char yield with a value of up to 82%, which are somewhat higher compared to those of the CF/poly(BA-a) composite, i.e., 405 � C and 75.7%, respectively. Therefore, due to the improvement in flame retardant, mechanical and thermal properties, the obtained CF-reinforced BA-a/PMDA composites exhibited high potential applications in advanced composite materials that required mechanical integrity and selfextinguishing property. POLYM. COMPOS., 34:2067– 2075, 2013. V C 2013 Society of Plastics Engineers

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

Effects of glass-to-rubber transition on the temperature, load and speed sensitivities of nano-ZrO2 reinforced polybenzoxazine

In the present work, nano ZrO2 reinforced polybenzoxazine composites were produced. The friction behaviors of ZrO2–polybenzoxazine nanocomposites were evaluated on a chase friction material test machine. An attempt was made to examine the variation of storage modulus, loss modulus and glass-to-rubber transition on the effect of the temperature, load and speed sensitivity of ZrO2–polybenzoxazine nanocomposites. The results revealed that the temperature and load sensitivity of nanocomposites increased with the increasing of load and temperature. This behavior was speculated to be due to the effect of the temperature dependence of modulus in the surface topography and strength. But speed sensitivity varies with the temperature, due to the effect of temperature dependence of viscoelastic response in the energy dissipation.

Influence of La2O3 on the Thermal Stability of Polybenzoxazine: Effect of Substituted Groups

Four kinds of benzoxazine monomers were synthesized, using phenol and aniline, 4-methylaniline, 4-nitroaniline, or 3-nitroaniline as starting materials. La2O3 was incorporated into the benzoxazines to prepare polybenzoxazine composites. The polybenzoxazines and their composites were analyzed through Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and TGA–FTIR. The results revealed that La2O3 can improve the thermal stability of aniline-based polybenzoxazine (Pa) and 4-methylaniline-based polybenzoxazine (Pa-pC) due to the delay of evaporation of the amine compounds during their thermal degradation process. However, La2O3 did not influence the thermal stability of polybenzoxazines based on 4-nitroaniline (Pa-pN) or 3-nitroaniline (Pa-mN), mainly resulting from the introduction of the nitro group remarkably changing the thermal degradation processes of Pa-pN and Pa-mN, producing a great deal of CO2 and H2O in their degradation gases, while amine and phenolic compounds gases were hardly detected.