Difunctional Benzoxazine Research Articles

Fire-safe composites made from bio-derived and difunctional benzoxazine hybridized matrix reinforced with Pistachio shell particles

Fire-safe composites made from bio-derived and difunctional benzoxazine hybridized matrix reinforced with Pistachio shell particles

High-Thermal Stable Epoxy Resin through Blending Nanoarchitectonics with Double-Decker-Shaped Polyhedral Silsesquioxane-Functionalized Benzoxazine Derivatives.

A series of di-functional benzoxazine (BZ) monomers was synthesized, specifically the double-decker silsesquioxane (DDSQ) cage structure (DDSQ-BZ). Comparative analyses were conducted between DDSQ-BZ monomers and the most commonly utilized bisphenol A-functionalized bifunctional benzoxazine (BPA-BZ) monomer. DDSQ-BZ compounds possess better thermal properties such as high char yield and high thermal decomposition temperature (Td10) after thermal ring-opening polymerization (ROP) because the inorganic DDSQ cage nanostructure features a nano-reinforcement effect. In addition, blending inorganic DDSQ-BZ compounds with epoxy resin was explored to form organic/inorganic hybrids with enhanced thermal and mechanical properties following thermal ROP. The improvement in mechanical properties is primarily attributed to the network structure formed by the cross-linking between DDSQ-BZ and the epoxy resin during thermal ROP, as well as hydrogen bonding interactions formed between the hydroxyl groups generated during thermal ROP and the Si-O-Si bonds in the DDSQ structure.

Development of Hybrid Composite Utilizing Micro-Cellulose Fibers Extracted from Date Palm Rachis in the Najran Region.

Environmental effects can be reduced by using renewable resources in various applications. The date palm fibers (DPF) used in this study were extracted from waste date ranches of the Najran region by retting and manual peeling processes. The biocomposites were developed by reinforcing the silane-treated DPF (SDPF) at different wt.% in eugenol phthalonitrile (EPN) and difunctional benzoxazine (BA-a) copolymer. The impact strength, tensile, flexural, and dynamic mechanical properties and thermogravimetric analysis were evaluated to understand the mechanical, thermomechanical, and thermal properties. Results confirmed that 30 wt.% SDPF-reinforced poly (EPN/BA-a) composites produced the highest mechanical and thermomechanical properties, and were considered optimized SDPF reinforcement. Furthermore, hybrid composites with 30 wt.% SDPF and 15 wt.% silane-treated glass fibers (SGF) reinforcement having different lamination sequences were also studied. The lamination sequences showed a significant impact on the mechanical and thermomechanical properties, as properties were further enhanced by adding a core layer of SGF in hybrid composites. However, the thermal properties of SDPF/SGF laminates were higher than SDPF biocomposites, but the SGF lamination sequence did not produce any impact. According to the limiting oxygen and heat resistance indexes, the developed SDPF/SGF laminates are self-extinguishing materials and can be used in temperature-tolerant applications up to 230 °C.

Development of chopped glass fiber composites with difunctional benzoxazine and bio‐based phthalonitrile copolymer: A study of mechanical and thermomechanical properties

AbstractThe randomly‐oriented glass fibers (GF) reinforced composites with Bisphenol A–amine based benzoxazine (BA‐a) and bio‐based eugenol‐based phthalonitrile (EPN) copolymer were developed by an isothermal compression molding technique. The silane coupling agent‐treated GF (TGF) reinforced composites showed much better impact strength as compared to as‐received GF reinforced composites. A rise of 95.2 MPa, 5.5GPa, 69.1 MPa, and 2.5GPa in flexural strength, flexural modulus, tensile strength, and Young's modulus were observed, respectively. The DMA results confirmed that the storage modulus (E') and glass transition temperature (Tg) were gradually increased and the damping factor decreased as the TGF reinforcement was raised from 0 to 40 wt%. E' and Tg values were 3.09 GPa and 27°C, respectively, higher than the recorded values for the neat copolymer. The 40 wt% TGF reinforced poly(BA‐a/EPN) composite showed the maximum thermal stability values of 475.4, 507.3°C, and 75.43% for T5, T10, and Yc, respectively. The LOI values confirm that the TGF/copolymer composites have self‐extinguishing properties.

Two novel eugenol-based difunctional benzoxazines: Synthesis and properties

Two novel eugenol-based difunctional benzoxazine monomers, named E-pea and E-dda, were successfully synthesized with a solvent-less method from eugenol, paraformaldehyde, 4,7,10-trioxa-1,13-tridecanediamine and 1,12-dodecanediamine. Their molecular structures were verified with Fourier Transform Infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Their curing behaviors were studied using differential scanning colorimetry (DSC) and FTIR techniques and a possible polymerization mechanism was proposed. Thermogravimetric analysis (TGA) was adopted to study the thermal stability of two polybenzoxazines, revealing that the fully polymerized E-pea and E-dda (denoted as PE-pea and PE-da) were both fairly thermostable with a char yield of 46.0 wt% at 800 ℃. Finally, contact angle tests manifest that the surface free energy (SFE) of PE-dda film was as low as 16.88 mJ/m2 while that of PE-pea film was 28.56 mJ/m2. Such an obvious increase in PE-pea’s SFE value is mainly caused by the inherent hydrophilicity of ether bonds.

Development of bio-based benzoxazines coated melamine foam for oil-water separation

Mono and di-functional benzoxazines were developed based on both sustainable bio-based cardanol and less hazardous synthetic bisphenol-F using mono and di amino derivatives with paraformaldehyde under appropriate experimental conditions. The molecular structure of the developed benzoxazines was confirmed using FTIR and 1HNMR spectra. The ring opening polymerization of developed benzoxazines was studied using differential scanning calorimetry to ascertain their cure behaviour. The hydrophophic and oleophhilic behaviour of benzoxazines coated melamine foam developed in the present work were ascertained from the values of water contact angle determined using goniometer. The optimum concentration required to transform hydrophilic melamine foam in to hydrophobic/oleophilic nature was studied using varying weight percentage amount of benzoxazines as coating material. Based on the results of water contact angle obtained for 25 wt%, 50 wt%, 75 wt% and 100 wt% of benzoxazine coated on melamine foam, it was ascertained that 50 wt% of benzoxazine was required to obtain maximum water contact angle. The values of water contact angle obtained for 50 wt% of C-a, C-l, C-s, C-h, C-i, BF-l and BF-s are 150˚,153˚,155˚,153˚,158˚,150˚and152˚respectively. It was also noticed that, among the different benzoxazines coated melamine foam, 50 wt% C-i possesses the highest value of water contact angle of 158˚. The oil (engine oil, mineral oil and soybean oil) absorption capacity of different polybenzoxazines coated melamine foam was obtained in the range between 85 and 95 times based on the weight of melamine foam. It is concluded from the results obtained, the materials developed in the present work has great utility in the field of oil/water separation and environmental pollution control.

Investigation on the role of the alkyl side chain of cardanol on benzoxazine polymerization and polymer properties

Cardanol is a bio-phenol used in the field of polybenzoxazine (polyBZ) due to its abundance, low cost, effectiveness, and ease of reaction. Its impact on the polymerization kinetic of benzoxazine as well as on the thermal stability has been hereby investigated. To this aim, three di-functional benzoxazine monomers (BZ) are synthesized by bridging with ethylene diamine either two phenols (di-phenol), one phenol and one cardanol (asymmetric card-phenol), or two cardanol moieties (di-cardanol). FT-IR measurements show that the presence of the cardanol aliphatic chain modifies the formation of hydrogen bonding network. These differences are highlighted in the chemorheology of polymerization, where the di-phenol BZ monomer shows an early vitrification explained by the formation of a high degree of H-bonding interactions during curing. An important feature of benzoxazines reactions, highlighted in this study, is that vitrification does not stop the polymerization process. Cardanol long alkyl side chain can cause a plasticizing effect and induces a lower degree of polymerization. This is observed through the decrease of the glass transition temperature (Tg) and the apparition of a β relaxation for cardanol-based polymers. Interestingly, the thermal stability is significantly improved for cardanol-based polyBZ, which can be the result of H-bonds reorganization in the system due to the cardanol aliphatic chains.

A conjugated alkyne functional bicyclic polybenzoxazine with superior heat resistance

ABSTRACTA difunctional benzoxazine (coPh‐apa) with a conjugated alkyne group is synthesized by the oxidative coupling reaction from a monocycle‐benzoxazine (Ph‐apa) containing an alkyne group. A model compound, 1,4‐diphenylbutadiyne (coPa), is used to study the curing reaction process of coPh‐apa by DSC, Fourier transform infrared spectroscopy, and 13C NMR, and the results suggest that the conjugated alkyne groups are involved in the crosslinking reaction via the trimerization reaction of the conjugated alkynyl groups and the Diels–Alder reaction. Furthermore, thermal properties of the polybenzoxazine are studied by dynamic thermomechanical analysis and thermogravimetric analysis. A glass‐transition temperature (Tgs) of as high as 412 °C and a char yield of 75.6% at 800 °C under nitrogen are obtained with the aid of the conjugated alkyne groups. Its excellent heat resistance dominates most thermosetting resins and will serve for heat shields. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1587–1592

Exploring Structure⁻Property Relationships in Aromatic Polybenzoxazines Through Molecular Simulation.

A series of commercial difunctional benzoxazine monomers are characterized using thermal and thermo-mechanical techniques before constructing representative polymer networks using molecular simulation techniques. Good agreement is obtained between replicate analyses and for the kinetic parameters obtained from differential scanning calorimetry data (and determined using the methods of Kissinger and Ozawa). Activation energies range from 85 to 108 kJ/mol (Kissinger) and 89 to 110 kJ/mol (Ozawa) for the uncatalyzed thermal polymerization reactions, which achieve conversions of between 85% and 97%. Glass transition temperatures determined from differential scanning calorimetry and dynamic mechanical thermal analysis are comparable, ranging from BA-a (151 °C, crosslink density 3.6 × 10−3 mol cm−3) containing the bisphenol A moiety to BP-a, based on a phenolphthalein bridge (239 to 256 °C, crosslink density 5.5 to 18.4 × 10−3 mol cm−3, depending on formulation). Molecular dynamics simulations of the polybenzoxazines generally agree well with empirical data, indicating that representative networks have been modelled.

Copolymerization of mono and difunctional benzoxazine monomers with bio-based phthalonitrile monomer: Curing behaviour, thermal, and mechanical properties

The eugenol based phthalonitrile (EPN) monomer was successfully copolymerized with mono and difunctional benzoxazine (P-a and BA-a) monomers via concerted catalysis polymerization. The loading of EPN in benzoxazine monomers was varied from 10 to 40 wt% and impacts of loading on thermal, thermomechanical and mechanical properties were studied. The FTIR analysis confirmed that both poly(P-a/EPN) and poly(BA-a/EPN) copolymers can be completely cured without the addition of curing additive. The addition of the bio-based EPN monomer enhanced the curing peak temperatures and reduced the curing reaction enthalpies. Initially, OH groups were produced from the oxazine ring opening polymerization of benzoxazine and they enhanced the curing of EPN. The thermal stabilities, as well as the stiffness and Tg of the copolymers, were much higher as compared to the neat polymers. Highest values were seen on the 40 wt% loading of EPN monomer in the copolymers. Moreover, the difunctional benzoxazine based copolymer showed higher enhancements in the properties as compared to the mono-functional benzoxazine based copolymer. The decline was seen in the flexural properties as EPN monomer contains the flexible chain in the structure. The morphological changes supported all the claims for the copolymers. The prepared copolymers can be used as a high performance thermosetting resin.

A Smart Latent Catalyst Containing o-Trifluoroacetamide Functional Benzoxazine: Precursor for Low Temperature Formation of Very High Performance Polybenzoxazole with Low Dielectric Constant and High Thermal Stability

A novel difunctional benzoxazine with o-trifluoroacetamide functionality has been synthesized via Mannich condensation. The chemical structure of synthesized monomer has also been confirmed by 1H, 13C, and 19F nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The ring-opening polymerization of the resin and the subsequent conversion of the freshly generated polybenzoxazine into polybenzoxazole are studied by FT-IR and differential scanning calorimetry (DSC). In addition to the advantage of low polymerization temperature as other reported o-amide benzoxazines, the o-trifluoroacetamide benzoxazine also exhibits an unexpected lower benzoxazole formation temperature. Furthermore, the resulting fluorinated polybenzoxazole derived from the benzoxazine monomer possesses the combined excellent properties of facile synthesis, easy processability, low dielectric constant, high thermal stability, and long shelf life, evidencing its potential applications in microelect...

Effect of methyl position on the dynamic mechanical and shape‐memory properties of cresol‐based polybenzoxazines

ABSTRACTThree difunctional benzoxazines were synthesized from cresol isomers (o‐, m‐, and p‐methylphenols), 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane, and formaldehyde. The ring‐opening polymerization temperature decreases in the order of ortho‐, para‐, and meta‐positions of methyl group for the benzoxazine monomers, whereas the glass transition temperature increases in the order of ortho‐, para‐, and meta‐positions of methyl group for the resultant polybenzoxazines. In addition, the polybenzoxazines exhibit one‐way dual‐shape‐memory behavior in response to changes in temperature, and the shape‐memory effects are evaluated by tensile and bending tests with a temperature program based on glass transition temperature. The o‐ and p‐cresol‐based polybenzoxazines exhibit higher shape‐memory performance than their m‐cresol‐based analogue/counterpart. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45443.

The F···H Hydrogen Bonding Effect on the Dynamic Mechanical and Shape‐Memory Properties of a Fluorine‐Containing Polybenzoxazine

A fluorine‐containing difunctional benzoxazine is synthesized by hydrosilylation of a monofunctional benzoxazine based ono‐allylphenol andp‐fluoroaniline. Besides the intramolecular and intermolecular hydrogen bonding associated with the nitrogen and oxygen atoms in the oxazine ring, specific self‐complementary intermolecular ArF···HO hydrogen bonding is formed in the polymerization of the benzoxazine, which leads to the resultant polybenzoxazine possessing a broad glass transition temperature range and showing two not well‐separated transitions. Based on the two glass transition temperatures, the polybenzoxazine exhibits triple‐shape‐memory behaviors by manipulating temperature and strain in the shape fixing process under tensile and bending modes. The dynamic mechanical and shape‐memory properties of the polybenzoxazine are influenced by the combined effect of the cross‐linking density and the ArF···HO hydrogen bonding.image

Shape memory polybenzoxazines based on polyetheramine

Five difunctional benzoxazines were synthesized from polyetheramine, phenol, o-allylphenol, o-cresol, p-cresol, m-cresol, and formaldehyde. The substituent groups decrease the ring-opening polymerization to present the ascending order of meta-, para-, and ortho-positions in comparison to the unsubstituted phenol-based benzoxazines. The dynamic mechanical properties of the resultant polybenzoxazines depend on the structure of the starting phenols. The polybenzoxazines exhibit one-way dual-shape memory behavior in response to changes in temperature, and the shape memory effects are evaluated by tensile stress–strain and bending tests with a temperature programme based on glass transition temperature.

Synthesis and characterization of difunctional benzoxazines from aromatic diester diamine containing varying length of aliphatic spacer group: Polymerization, thermal and viscoelastic characteristics

A series of four novel diamine-based benzoxazines containing aliphatic spacer groups in their structures were synthesized by the condensation of formaldehyde, phenol and aromatic diester diamine obtained by reduction of their precursor dinitro compounds. The four aromatic diamines synthesized are ethane-1,2-diyl bis (4-aminobenzoate), butane-1,4-diyl bis (4-aminobenzoate), hexane-1,6-diyl bis (4-aminobenzoate), and octane-1,8-diyl bis (4-aminobenzoate). The chemical structures of diamine benzoxazines are confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance spectroscopy (1H and 13C NMR). The curing properties with respect to the basic benzoxazine structure of the monomer were studied by differential scanning calorimetry (DSC). The softening points, onset of cure temperatures and the heat of polymerization have all decreased with increasing spacer length. DSC of polybenzoxazines indicated decrease of glass transition temperature (Tg) with increasing spacer length. The thermal behavior of polybenzoxazines was studied by thermo gravimetric analysis (TGA). Higher Td5 and Td10 values were obtained by polybenzoxazines with longer spacer groups but an inversion in thermal stability was observed after Td10. The derivative thermo gram of polybenzoxazine indicated a two stage degradation process due to chain cleavage at Mannich bridge as well as breakdown of polymer chain respectively. The char yield at 700°C has decreased with increasing spacer length from 47% to 27%. The mechanical properties of glass cloth coated polybenzoxazines were evaluated with dynamic mechanical analysis (DMA). The storage modulus of the composite laminate of polybenzoxazine has increased with increasing spacer group which could be due to improvement in adhesion between fibers and resin with increasing flexibility of the resin.

Thermally stable polybenzoxazines via ortho-norbornene functional benzoxazine monomers: Unique advantages in monomer synthesis, processing and polymer properties

Monofunctional and difunctional benzoxazines with ortho-norbornene functionality have been synthesized via Mannich condensation. The structure of synthesized monomers has been confirmed by 1H nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR). The ortho-norbornene functional benzoxazine resins show excellent features both in the synthesis of benzoxazine monomers and the properties of the corresponding thermosets. The benzoxazines containing norbornene groups can polymerize with multiple polymerization mechanisms rather than the single mechanism common to traditional 1,3-benzoxazine resins. The polymerization mechanisms are monitored by in situ FT-IR and differential scanning calorimetry (DSC). Activation energy of polymerization is also studied by DSC. Moreover, the thermoset derived from the difunctional benzoxazine monomer exhibits high thermal stability with the glass transition temperature of 365 °C and a high Td5 of 463 °C.

Synthesis, curing kinetics and thermal properties of novel difunctional chiral and achiral benzoxazines with double chiral centers

Novel difunctional chiral and achiral benzoxazine monomers were synthesized from the reaction of bisphenol A with paraformaldehyde and primary amines, including S-(+)-3-methyl-2-butylamine and rac-(±)-3-methyl-2-butylamine, by solventless method. The chemical structures of chiral and achiral benzoxazines were identified by fourier transform infrared, nuclear magnetic resonance (1H NMR and 13C NMR). The curing behavior and non-isothermal curing kinetics of chiral and achiral benzoxazine monomers were investigated by differential scanning calorimeter (DSC). Isoconversional methods based on Friedman and Kissinger–Akahira–Sunose were applied to analyze the curing process of chiral and achiral benzoxazines. The thermal properties of cured polymers were characterized by DSC and thermogravimetry. The results suggested that the optical purity and stereo-configuration for chiral and achiral benzoxazines have definite influence on curing behavior and thermal properties despite the same chemical structure. Chiral benzoxazine displayed typical characteristics of difunctional benzoxazines. Achiral benzoxazine showed distinctly double peaks in DSC exotherms due to the presence of racemic and mesomeric isomers. The thermal properties of achiral polybenzoxazine were slightly higher than those of chiral polybenzoxazine, and were much higher than those of other bisphenol A-C3–C8 linear aliphatic amine-based polybenzoxazines because of tight packing, low free volume, and abundant intramolecular and intermolecular hydrogen bonds in network structure of polymers.

Highly durable polymer electrolyte membranes at elevated temperature: Cross-linked copolymer structure consisting of poly(benzoxazine) and poly(benzimidazole)

For polymer electrolyte membrane fuel cell (PEMFC) applications at elevated temperature (>100 °C), a series of cross-linked benzoxazine–benzimidazole copolymer, P(HFa-co-BI), membranes are prepared by casting a solution of poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI) and di-functional benzoxazine monomer, 6,6′-(hexafluoroisopropylidene)bis(3-phenyl-3,4-dihydro-2H-benzoxazine) (HFa), in N,N-dimethylacetamide prior to stepwise heating to 250 °C. The films are also viable to manufacture to large quantities and area by roll-to-roll coating. The resulting cross-linked copolymer, P(HFa-co-BI), membranes are found to be thermally and mechanically stable. Although the proton conductivity values of P(HFa-co-BI) membranes are smaller than that of the PBI membrane, their cell performance (0.68 V at 0.2 A cm−2 at 150 °C) is close to that of PBI membrane and their long-term durability (ca. 3116 cycles on in situ accelerated lifetime mode of load cycling testing) is found to be far superior to the PBI membrane.

Polymerization of p-cresol, formaldehyde, and piperazine and structure of monofunctional benzoxazine-derived oligomers

By using a secondary amine, e g. piperazine, a Mannich base polymer, having similar structure to the traditional polybenzoxazine, is synthesized. Unlike all the reported polybenzoxazines that are colored, the white polymer shows good thermal property that is close to the degradation temperature of the polybenzoxazine derived from difunctional benzoxazine monomers. 31P NMR spectroscopy in combination with facile phosphorus derivatization and previous model compound studies are utilized to clarify the structures of piperazine-based systems as well as the main chain and end group of traditional polybenzoxazines.

Benzoxazine Miniemulsions Stabilized with Polymerizable Nonionic Benzoxazine Surfactants

For the first time, the concept of polymerizable nonionic benzoxazine surfactants is described. Different target structures with varying hydrophobic−lipophilic balance (HLB) values were synthesized and successfully tested for the miniemulsification of two N-aliphatic and N-aromatic benzoxazine resins. As a model system, the difunctional benzoxazine surfactant bis(3,4-dihydro-2H-3-(polypropyleneoxide-block-polyethyleneoxide-1,3-benzoxazinyl)isopropane (B2000) was analyzed in detail via FT-IR, 1H NMR, surface tension measurements, and thermal analysis such as DSC and TGA. Additional to the colloidal stability of the benzoxazine miniemulsions, investigations focused on the surfactant copolymerization behavior and compatibility with other resins. It was found that despite the observed slow homopolymerization the described surfactants easily undergo copolymerization with the model benzoxazine resins.