Crystallization,dispersion behavior and the induced properties through forming a controllable network in the crosslinked polyester‐SiO2 nanocomposites

This article describes the synthesis and characterization of two types of benzoxazine monomers based on phenol or bisphenol, aniline, and formaldehyde. Their characterization was achieved by Fourier transform infrared, ¹H-nuclear magnetic resonance, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Lignin polymer was characterized by infrared, DSC, and TGA. The curing behavior of mixtures of benzoxazine monomers and lignin was investigated by DSC. The mass ratios of benzoxazine monomers/lignin of a series of samples were 100 : 0, 95 : 05, 90 : 10, 85 : 15, 80 : 20, 75 : 25, and 70 : 30. The results indicate that the maximum curing temperatures of the mixtures were lower than that of the pure benzoxazine monomers, and that they decreased with increasing contents of lignin in the mixture. The heat of polymerization (ΔH) of the benzoxazine monomers and lignin mixtures as a function of the mass ratio and the structure of the benzoxazine monomers shows no definite trend. The samples were cured according to the following conditions: 170°C/2h + 200°C/2h and analyzed by DSC and TGA. In all the samples, the glass transition temperature of the benzoxazines increased upon mixing with increasing amounts of lignin. The changes may be due to the formation of a more compact network structure in the mixtures. The thermal stability of the isothermally cured resins is found to be dependent on the mass ratio of benzoxazine/lignin and structure of the benzoxazine monomers. The more lignin in the mixture, the higher is the char yield in the mixture. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dynamic mechanical and shape memory properties of copolymers based on o‐allylphenol type benzoxazines and diglycidyl ether of bisphenol‐A

Three benzoxazines based on o‐allylphenol and 1,6‐hexamethylenediamine (HDA) or 4,4′‐diaminodiphenyl methane (DDM) or 4,4′‐diaminodiphenyl ether (DDE) were respectively blended with diglycidyl ether of bisphenol‐A (DGEBA) in various weight ratios followed by thermal polymerization to prepare three series of benzoxazine/DGEBA copolymers. With increasing DGEBA content, the peak temperature of the exothermic peaks in the DSC curves shows a systematic increase for the three series of benzoxazine/DGEBA blends. Each copolymer shows a single glass transition temperature (T_g). As the content of DGEBA is increased, T_g reaches a minimum for the copolymer system based on HDA but a maximum for the two systems based on DDM and DDE. For the same benzoxazine/DGEBA weight ratio, copolymers based on DDM and DDE show high T_g values over those based on HDA. The three series of benzoxazine/DGEBA copolymers exhibit a one‐way dual shape memory effect based on T_g, and the shape memory properties of the copolymers under tensile deformation mode vary with the variation of both diamine bridge structure and DGEBA content. © 2018 Society of Chemical Industry     

Synthesis and characterization of new thermosetting polybenzoxazines with other functional groups in the network

In this work, novel thermosetting systems of high performance based on multi-functional benzoxazines were developed. First, 3-(2-hydroxyethyl)-3,4-dihydro-2H-1,3-benzoxazine (BzOH) and bis(3-(2-hydroxyethyl)-3,4-dihydro-2H-1,3- benzoxazinyl) isopropane (BzPOH) monomers were synthesized by reaction between phenol or bisphenol A, paraformaldehyde, and ethanolamine. Then, BzOH and BzPOH were functionalized with maleic anhydride using a stoichiometric ratio of oxazine: maleic anhydride (1:1) to produce low molar mass species with carboxylic acid groups, named BzFA and BzPFA. The products were characterized by Nuclear Magnetic Resonance (NMR), Size-Exclusion Chromatography (SEC), and Fourier Transform Infrared Spectroscopy (FTIR). BzFA and BzPFA exhibited weight-average molecular weights of 5000 g.mol^?1and 50,000 g.mol^?1, respectively. Mixtures between the new precursors and the conventional benzoxazine (BzBA) derived from bisphenol A and aniline [bis(3-phenyl-3,4-dihydro-2H-1,3benzoxazinyl) isopropane] were prepared. The curing process was studied by FTIR and Differential Scanning Calorimetry (DSC), and viscoelastic, mechanical, thermal, and morphological properties of the materials were also evaluated. Materials obtained exhibited better thermal, viscoelastic and mechanical properties than conventional polybenzoxazine. Scanning Electron Microscope (SEM) measurements indicated homogeneous material surfaces.     

Investigation of polymerization of benzoxazines and thermal degradation characteristics of polybenzoxazines via direct pyrolysis mass spectrometry

Polymerization of benzoxazines and thermal degradation mechanisms of polybenzoxazines were investigated using the direct pyrolysis mass spectrometry (DP‐MS) technique. The benzoxazine structures were based on phenol and aniline and on bisphenol‐A and methylamine or aniline. Polymerizations of the benzoxazines were carried out by curing them at elevated temperatures without addition of initiator or catalyst. DP‐MS data showed the presence of chains generated by opposing polymerization reaction pathways indicating quite complex structures for the polybenzoxazines under investigation. Thermal decomposition of polybenzoxazines was started by the cleavage of methylamine or aniline linkages. It was determined that polybenzoxazines based on phenol were more stable than the corresponding bisphenol‐A‐based polybenzoxazines, while those based on methylamine were more stable than the corresponding polybenzoxazines incorporating aniline. Thus, it can be concluded that the presence of bulky groups decreased the extent of crosslinking which in return decreased the thermal stability. Copyright © 2012 Society of Chemical Industry     

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

In 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 (T_p) 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.     

微波固相法合成苯并恶嗪及其共混树脂的性能

邻位二烷基取代苯胺与苯酚和多聚甲醛经100 W微波辐照20 min反应得到了5种苯并恶嗪单体,将其中邻位为甲基和乙基取代的苯胺型苯并恶嗪与双酚A型苯并恶嗪(BAF)共混,采用红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)、示差扫描量热仪(DSC)、动态机械分析(DMA)、热失重分析仪(TGA)、粘度仪和介电阻抗仪研究了共混树脂的粘温性、热性能及介电性能。结果表明,邻二甲基苯胺型苯并恶嗪(2m6m-BZ)与BAF以物质的量比3∶7共混的体系100～250℃下粘度<500 mPa.s,其固化后热性能接近固化后的纯BAF树脂,且介电常数<3.9,介电损耗低于0.003 5,优于其它共混树脂。     

Benzoxazine monomers based on aromatic diamines and investigation of their polymerization by rheological and thermal methods

In the present article with the aim to find new polybenzoxazines with improved thermal properties, new benzoxazine monomers based on phenol and the following aromatic diamines were synthesized: 3,4′-oxydianiline (P-3,4′oda); o-tolidine (P-ot); m-tolidine (P-mt) and 4,4′-(1,3-phenylenedioxy)dianiline (P-tper) and their comparison with the previously known benzoxazines based on 4,4′-diaminodiphenylmethane (P-ddm); 4,4′-oxydianiline (P-4,4′-oda) and 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (P-bapp). The dependence of the thermal and rheological characteristics on the structure of benzoxazine monomers based on various diamines was estimated and possible methods for their processing were identified. All the polybenzoxazines obtained in this work have high char yield and reduced flammability. It was found that the structure of the diamine can have a fundamental effect on both the rheological properties and heat resistance of polybenzoxazines. The benzoxazine monomers P-ddm, P-tper and P-4,4′oda retain viscosity up to 1 Pa s. at 110°C for 2 h, the P-tper monomer with a resorcinol bridge has about five times lower viscosity compared to the P-bapp monomer with a bisphenol A bridge. Polybenzoxazines based on the monomers P-ddm, P-mt, P-bapp and P-tper show excellent thermal stability with a temperature of 10% weight loss above 400°C. In particular, T_g of P-3,4′oda and P-mt monomers is relatively high (202 and 239°C, respectively), while P-ot's is unusually low (115°C), which may be caused by the specific effect of the substituents in the aromatic ring of the amine and their position.     

Synthesis of a novel benzoxazine precursor containing phenol hydroxyl groups and its polymer

A novel benzoxazine precursor containing phenol hydroxyl groups was synthesized from bisphenol A, 4,4′‐diaminodiphenyl methane, and formaldehyde with a molar ratio of 2:1:4. The benzoxazine precursor was characterized with Fourier transform infrared, proton nuclear magnetic resonance, and size exclusion chromatography. The curing reaction was monitored by the gel time, differential scanning calorimetry, and Fourier transform infrared. The obtained polybenzoxazine showed high thermal stability and a high glass‐transition temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Design of thermosetting polymeric systems based on benzoxazines modified with maleic anhydride

A novel benzoxazine (BzPFA) with carboxylic acid groups in its structure was synthesized in a two‐step process. First, BzPOH monomer was obtained from bisphenol A, paraformaldehyde, and ethanolamine with an initial molar ratio 1:4:2. Then, BzPOH was reacted with maleic anhydride using a stoichiometric 1:1 ratio of oxazine ring:maleic anhydride to produce a mixture of oligomeric species named BzPFA. The products were characterized by nuclear magnetic resonance, size‐exclusion chromatography, and Fourier transform infrared spectroscopy. BzPFA presented a weight‐average molecular weight of 50,000 g mol^?1. Mixtures of the novel precursor and the conventional benzoxazine based on bisphenol A (BzBA) (60:40 and 40:60 weight ratios) were prepared and three different curing conditions were considered in order to study the effect of BzPFA on curing and final properties. Blends exhibited improved properties respect to BzBA even at relatively low curing temperatures. These results can be associated to the network crosslinked by ester bonds that promotes a high rigidity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46183.     

Synthesis and characterization of a novel class of low temperature cure Benzoxazines

A series of a novel class of low cure benzoxazines (BZ-1 to BZ-12) based on phenol, bisphenol-A, bisphenol-F mixture and 4, 4 isomers of bisphenol-F were synthesized using aniline, N, N-dimethyl amino propyl amine (DMAPA) and caprolactam (CPL) modified DMAPA. The molecular structure of benzoxazine monomers was characterized by ¹H NMR, FT-IR, and LC mass spectrometry analysis. DSC and TGA analysis were carried out to study the polymerization process and stability of benzoxazines respectively. Among the benzoxazine systems studied, PBZ-5 is found to possess the reasonably lower cure temperature with good char yield, T_max and Tg values. The catalytic effect on curing behavior of BZ-5 with different types of catalysts such as mono hydroxy (C₁-C₆), polyhydroxy (C₇-C₉) and acidic catalysts (C₁₀ to C₁₃) was studied and discussed in detail. Among the catalysts used, 4,4-thiobisphenol (C₇) was found to be the most effective catalyst towards the ring opening polymerization and in turn lowers the cure temperature (amount, acidity, basicity and structural compatibility of the catalysts) than that of other catalysts (C₂-C₁₃). In addition, the catalytic behavior of starting materials (bisphenol-A and bisphenol-F) towards benzoxazines BZ-5, BZ-6, BZ-8 and BZ-9 were also studied and it can be found that bisphenol-A/F also acts as an effective catalyst which can bring down the cure exotherm to a significant extent.     

Flexible polybenzoxazine thermosets containing pendent aliphatic chains

The rich chemistry of polybenzoxazines allows a wide range of molecular structure design by using appropriate starting materials. A new class of polybenzoxazines has been developed from benzoxazine monomers containing pendent long aliphatic chains. The monomers have been synthesized by the reaction of phenol or bisphenol A with two different long‐chain aliphatic amines. The chemical structure of the monomers was confirmed by ¹H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The polymerization behavior of the monomers studied by differential scanning calorimetry shows exothermic peaks due to the ring‐opening polymerization of benzoxazine monomers centered at 247–255 °C. Dynamic mechanical analysis indicated that the glass transition temperatures T_g were in the range 81–92 °C. The thermal stability of the polymers was also examined by thermogravimetric analysis, demonstrating that the weight loss temperatures decreased in comparison with that of traditional polybenzoxazine. Copyright © 2011 Society of Chemical Industry     

Dynamic mechanical and shape memory properties of polybenzoxazines based on aminopropyl‐terminated siloxanes

Four siloxane‐containing benzoxazine monomers and telechelic benzoxazine oligomers were synthesized from 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane, α,ω‐bis(3‐aminopropyl)polydimethylsiloxane, phenol, o‐allylphenol, and formaldehyde. The length of the siloxane segment affects the polymerization reaction of the benzoxazine monomers and telechelic benzoxazine oligomers. The dynamic mechanical properties of the corresponding polybenzoxazines depend primarily on the structure of phenol and the length of the siloxane segment. The polybenzoxazines exhibit one‐way dual‐shape memory behavior in response to changes in temperature. The thermally induced shape memory effects of the polybenzoxazines were characterized by bending and tensile stress–strain tests with a temperature program based on their glass transition temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44121.     

Enzyme‐catalyzed copolymerization of oxiranes with dicarboxylic acid anhydrides

Ring‐opening copolymerizations of the oxiranes glycidyl phenyl ether (GPE) and diglycidyl ether of bisphenol A (DGEBA) with a dicarboxylic acid anhydride [methyl hexahydrophthalic anhydride, nadic anhydride, maleic anhydride (MA), or itaconic anhydride (IA)] were carried out with the lipases Candida cylindracea (CCL), Lipozyme TL‐IM (LIM), and Novozyme 435 (N435) as catalysts. The CCL‐catalyzed reaction of DGEBA with MA or IA (at a 1:2 molar ratio) at 80°C resulted in only partial curing. We monitored the reactions by Fourier transform infrared spectroscopy and by following the changes in the intensities of carbonyl stretching frequencies of the anhydride and ester groups. The reactivity of the oxirane group in GPE was higher than that in DGEBA; this may have been due to the higher viscosity of DGEBA. The reactivities of the enzymes for the copolymerization of the oxiranes and dicarboxylic acid anhydride were in the order LIM > CCL > N435. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 697–704, 2005     

同分异构双酚F型苯并噁嗪的研究

分别以同分异构体混合型双酚F和对位双酚F为原料,通过溶液法制备出双酚F型苯并噁嗪。利用傅里叶变换红外光谱(FTIR)、核磁共振氢谱(1H NMR)、凝胶渗透色谱法(GPC)、示差扫描量热法(DSC)、动态热力学分析(DMA)和热重分析(TGA)对2种双酚F型苯并噁嗪中间体的结构、固化行为及其固化物的性能进行了研究。结果表明双酚F中的同分异构体对苯并噁嗪的性能存在影响。对位双酚F型苯并噁嗪的成环率、固化物耐热性和热稳定性均高于同分异构混合双酚F型苯并噁嗪。     

Studies on thermal behavior of imidazole diamine based benzoxazines

The objective of the present work is to develop a novel type of structurally modified benzoxazines with improved performance characteristics using imidazole core based diamine with formaldehyde and different types of phenolic compounds in order to utilize them for high‐performance applications. In this work, an attempt has been made to bring down the polymerization temperature of the benzoxazine monomers, which is one of the most deficient factor restrict the applications of benzoxazines, when used in the form of adhesives, sealants, encapsulants, and matrices with other substrates, though they possess numerous advantages and valuable properties than those of other available thermosets. In this context, in this study, two approaches have been adopted to bring down the polymerization temperature, viz., (i) the development of structurally modified benzoxazine monomers with imidazole core and (ii) an incorporation of varying nature of chemical compounds as catalysts, to lower the polymerization temperature and to enhance the thermal stability and char yield. Three types of benzoxazines were developed using imidazole core based diamine with monohydric phenols and formaldehyde, at appropriate conditions. The molecular structure of benzoxazines was confirmed from Fourier transform infrared spectroscopy and ¹H‐nuclear magnetic resonance analysis. From data, it was observed that the imidazole diamine based benzoxazines prepared from 1‐naphthol exhibits lower curing temperature of about 192 °C than that of other samples studied in this work. In addition, the influencing effect of catalysts viz., 4‐hydroxy acetophenone, 4‐hydroxy benzaldehyde, 4‐hydroxyphenyl maleimide, and thiodipropionic acid (TPA) on thermal properties of benzoxazines also was studied. Among the catalysts, it was found that the TPA is the most efficient catalyst. In the case of imidazole diamine based benzoxazines prepared from cyanophenol, the TPA reduces value of polymerization temperature (T_p) from 217 to 167 °C. The thermogravimetric analysis indicates that thermal stability of the benzoxazines are improved to a significant extent when 10 wt % catalysts were incorporated into the system. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46562.     

Different parameters controlling the initial solubility of two thermoplastics in epoxy reactive solvents

The influence of different factors on the miscibility of diglycidyl ether of bisphenol A (DGEBA)/thermoplastic blends was studied. DGEBA/poly(ether imide) (PEI) blends exhibited upper critical solution temperature behavior. The addition of a trifunctional epoxy [triglycidyl para‐amino phenol (TGpAP)] increased the miscibility window. The addition of diamines as hardeners could also increase [4,4′‐methylene‐bis(3‐chloro‐2,6‐diethylaniline) (MCDEA)] or decrease (4,4′‐diaminodiphenylsulfone) the miscibility window. DGEBA/poly(ether sulfone) (PES) blends showed lower critical solution temperature behavior. The addition of TGpAP had an effect similar to that for PEI blends, but the presence of MCDEA as a hardener decreased the miscibility of epoxy/PES blends. The modeling of the cloud‐point curves was performed with the Flory–Huggins equation (Flory, P. J. Principles of Polymer Chemistry; Cornell University Press: Ithaca, NY, 1953; p 672) according to the procedure developed by K. Kamide, S. Matsuada, and H. Shirataki (Eur Polym J 1990, 26, 379), with the interaction parameter used as the fitting parameter. A phenomenological model that takes into account the molar mass of DGEBA and the amount of TGpAP is proposed and is found to predict the cloud‐point temperature of any TGpAP/DGEBA/PEI blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1385–1396, 2002     

New thermosetting resin from poly(p‐vinylphenol) based benzoxazine and epoxy resin

Poly(p‐vinylphenol) (VP) based benzoxazine was prepared from VP, formaline, and aniline. The curing behavior of the benzoxazine with the epoxy resin and the properties of the cured resin were investigated. Consequently, the curing reaction did not proceed at low temperatures, but it proceeded rapidly at higher temperatures without a curing accelerator. The reaction induction time or cure time of the molten mixture from VP based benzoxazine and epoxy resin was found to decrease, compared with those from conventional bisphenol A based benzoxazine and epoxy resin. The curing reaction rate of VP based benzoxazine and epoxy resin increased more than that of conventional bisphenol A based benzoxazine and epoxy resin. The properties of the cured resin from neat resins and from reinforced resins with fused silica were evaluated. The cured resins from VP based benzoxazine and epoxy resin showed good heat resistance, mechanical properties, electrical insulation, and water resistance compared to the cured resin from VP and epoxy resin using imidazole as the catalyst. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 555–565, 2001     

Resin transfer molding of natural fiber reinforced polybenzoxazine composities

Kenaf fiber is incorporated in a polybenzoxazine (PBZX) resin matrix to form a unidirectionally reinforced composite containing 20 wt% fiber by a resin transfer molding technique. Two types of benzoxazine monomer are synthesized and used as resin mixtures: Benzozazines based on bisphenol‐A/aniline (BA‐a) and phenol/aniline (Ph‐a). The effects of varying BA‐a:Ph‐a ratio in the resin mixture and curing conditions on mechanical properties of pure PBZX resin and kenaf/PBZX composites are studies. The Flexural strength of the pure PBZX resin increases with increasing ratio of BA‐a:Ph‐a, curing temperature and curing time, but the impact strength increases only slightly. PBZX resin has lower water absorption and higher flexural modulus, when compared with unsaturated polyester (UPE) resin. PBZX composites with 20 wt% fiber content have lower flexural and impact strengths, but higher moduli compared with UPE composites with the same fiber content.     

Synthesis and properties of a novel bio‐based benzoxazine resin with excellent low‐temperature curing ability

A novel bio‐based benzoxazine resin (diphenolic acid/furfurylamine benzoxazine resin, PDPA‐F‐Boz) was prepared by using bio‐based diphenolic acid, furfurylamine and paraformaldehyde as raw materials. The structure of DPA‐F‐Boz monomer was characterized by Fourier transform infrared spectroscopy, ¹H NMR and ¹³C NMR, and then its curing reaction and the thermal stability of the cured PDPA‐F‐Boz were analyzed. Compared with the traditional fossil‐based benzoxazine (bisphenol A/aniline benzoxazine, BPA‐A‐Boz) and the bio‐based benzoxazine (diphenolic acid/aniline benzoxazine, DPA‐A‐Boz), DPA‐F‐Boz monomer showed the lowest curing temperature, and PDPA‐F‐Boz had the highest residual char ratio at 800 °C and the lowest degradation rate at the peak temperature. Meanwhile, the total heat release, peak heat release rate and heat release capacity of PDPA‐F‐Boz were much lower than those of PBPA‐A‐Boz and PDPA‐A‐Boz. Thus, PDPA‐F‐Boz showed excellent low‐temperature curing ability and thermal stability. © 2019 Society of Chemical Industry     

Preparation and characterization of highly thermostable polyisocyanurate foams modified with epoxy resin

A series of epoxy resin–modified polyisocyanurate (EP‐PIR) foams with oxazolidone (OX) rings and isocyanurate (IS) rings have been successfully prepared by the reaction of polymethylene polyphenyl isocyanate (PAPI) and diglycidyl ether of bisphenol‐A (DGEBA). Fourier transform infrared spectroscopy and differential scanning calorimetry are performed to investigate the influence of curing temperature on the chemical structure of EP‐PIR foams. The results indicate that low temperature is beneficial to the formation of the IS ring, and high temperature is in favor of the OX ring. The influence of the mole ratio of [PAPI]/[DGEBA] on the mechanical properties and thermal stability has also been studied. With the increase of [PAPI]/[DGEBA], the specific compressive strength shows a maximum of 0.0135 ± 0.0003 MPa m³/kg. The optimized mole ratio of [PAPI]/[DGEBA] is around 2.5 to reach the better mechanical and thermal properties, and the glass‐transition temperature is as high as 323.5°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43085.