Preparation and properties of some thermosets derived from allyl‐functional naphthoxazines

A series of novel naphthoxazine monomers containing allyl functionalities were synthesized from the reaction of 1‐naphthol, 2‐naphthol, and 1,5‐dihdroxynaphthalene with allylamine and formalin. Another series of naphthoxazines were similarly prepared by using aniline instead of allylamine for comparison. The chemical structures of these novel monomers were confirmed by IR, ¹H NMR, and elemental analysis. DSC of the aniline‐ based naphthoxazines showed an exotherm due to the ring‐opening polymerization of oxazine. For allylamine‐based naphthoxazines, two exotherms were observed. The first exotherm is attributed to the thermal crosslinking of the allyl group and the second is due to the ring‐ opening polymerization of oxazine. The thermal cure of the allylamine‐based naphthoxazine monomers gave thermoset resins with novel structure comprising of polynaphthoxazine with extended network via the polymerization of allyl functionalities. Dynamic mechanical analyses and thermogravimetric analyses showed that the thermosets derived from allyl‐ functional naphthoxazines have high T_g's and stable storage moduli to higher temperature as well as better thermal stability than that of aniline‐based naphthoxazines. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3769–3777, 2006     

Synthesis,characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites

organoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (T_g) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry     

High‐performance nanocomposites derived from allyl‐terminated benzoxazine and octakis(propylglycidyl ether) polyhedral oligomeric silsesquioxane

In this study, we used the Mannich condensation of bisphenol A, formaldehyde, and allylamine to synthesize a allyl‐terminated benzoxazine (VB‐a), which can be polymerized through ring opening polymerization. We used this VB‐a monomer, blended with octakis(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OG‐POSS), to prepare polybenzoxazine/POSS nanocomposites. Differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy revealed that the mechanism of the crosslinking reaction leading to the formation of the organic/inorganic network involved two steps: (i) ring opening and allyl polymerizations of VB‐a and (ii) subsequent reactions between the in situ‐formed phenolic hydroxyl groups of VB‐a and the epoxide groups of OG‐POSS. Dynamic mechanical analysis revealed that the nanocomposites had higher mechanical properties than did the control VB‐a. In the glassy state, nanocomposites containing less than 10 wt % POSS displayed enhanced storage moduli; those of the nanocomposites containing greater than 10 wt % POSS were relatively low, due to aggregation, as determined using scanningelectron microscopy. Thermogravimetric analysis indicated that the nanocomposites possessed greater thermal stability than that of the pure polymer. FTIR spectroscopic analysis revealed the presence of hydrogen bonding between the siloxane groups of POSS and the OH groups of the polybenzoxazine. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Use of allyl‐functional benzoxazine monomers as replacement for styrene in vinyl ester resins

New vinyl ester systems are prepared using allyl‐functional benzoxazine monomers, 3‐allyl‐6‐methyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazine (pC‐ala) or bis(3‐allyl‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazin‐6‐yl)methane (BF‐ala), as reactive diluents for vinyl ester resins derived from an epoxy resin, diglycidyl ether of bisphenol A, instead of using styrene. Different initiators are used to investigate the copolymerization of allyl function from pC‐ala with vinyl function from vinyl ester resin prepolymer. The temperature dependence of viscosity is studied to demonstrate the retention of processability of the new vinyl ester resins. Dynamic mechanical and thermogravimetric analyses are used to investigate the dynamic mechanical properties and thermal stability of the new resins. Copyright © 2012 Society of Chemical Industry     

双马来酰亚胺改性苯并噁嗪树脂的力学性能及摩擦性能

苯并噁嗪(BOZ)树脂作为一种新型的热固性PF(酚醛树脂),具有诸多优异性能,但其韧性和耐磨性较差。以AE-BMI(含烯丙基醚的双马来酰亚胺预聚体)为改性剂制备AE-BMI/BOZ改性树脂,并对其力学性能和摩擦性能进行了研究。结果表明:适量的AE-BMI对BOZ树脂具有明显的增韧增强作用,并且其耐磨性也明显提高;当w(AE-BMI)=15%时,AE-BMI/BOZ改性体系的弯曲强度(125.53 MPa)和冲击强度(11.57 kJ/m2)分别比纯BOZ体系提高了57%和60%,并且其摩擦因数(0.27)和磨损率[18.50×10-6mm3/(N.m)]分别比纯BOZ体系降低了15.6%和50.6%。     

Preparation of nanocomposites of thermosetting resin from benzoxazine and bisoxazoline with montmorillonite

The thermosetting resin from 2,2′‐(1,3‐phenylene)‐bis(4,5‐dihydro‐oxazoles) (PBO) and bis(3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine)isopropane (BZ) was prepared, and it was found that the thermal property of the final resin was affected greatly by the content of PBO. The nanocomposite from the thermosetting resin from BZ and PBO (molar ratio of PBO to BZ, 0.8 : 1) (PBZ–PBO) and organically modified montmorillonite (OMMT) was prepared by melt method. Differential scanning calorimetry showed that on the introduction of OMMT, the onset curing temperature of the copolymerization of BZ and PBO decreased. The X‐ray diffractometer and transmission electron micrograph characterization of the dispersion of OMMT in the PBZ–PBO matrix suggested that exfoliation structure of OMMT was achieved. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher T_g values than the PBZ–PBO resin and pristine polybenzoxazine, and storage modulus of the nanocomposites was maintained up to higher temperature with the increasing OMMT content. Dynamic thermogravimetric analysis showed that the dispersion of clay nanolayers in the PBZ–PBO copolymer gave better thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4741–4747, 2006     

4,4′‐Bismaleimidodiphenyl methane modified novolak resin/titania nanocomposites: Preparation and properties

4,4′‐Bismaleimidodiphenyl methane modified novolak resin/titania nanocomposites were prepared by the sol–gel process of tetrabutyl titanate in the presence of 4,4′‐bismaleimidodiphenyl methane modified novolak resin prepolymers with acetyl acetone as a stabilizer. These nanocomposite materials were characterized by Fourier transform infrared analysis, dynamical mechanical analysis, thermogravimetric analysis, transmission electron microscopy, and field emission scanning electron microscopy. Nanometer titania particles were formed in the novolak resin matrix, and the average original particle size of the dispersed phase in the nanocomposites was less than 150 nm, but particle aggregates of larger size existed. The introduction of the titania inorganic phase with a nanoscale domain size did not improve the glass‐transition temperature of the nanocomposites but lowered the thermal resistance of the material because of the incomplete removal of acetyl acetone coordinated with tetrabutyl titanate, and it improved the modulus of the material at lower temperatures (<200°C) but lowered the modulus at higher temperatures (>250°C). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 52–57, 2006     

Cure kinetic study of organoclay‐unsaturated polyester resin nanocomposites by using advanced isoconversional approach

Curing behavior of an unsaturated polyester (UP) resin containing 3 wt % Cloisite 10A (UP/10A) and 3 wt % Cloisite 30B (UP/30B) catalyzed with methyl ethyl ketone peroxide (MEKP) as initiator and promoted by cobalt naphthenate as accelerator was investigated by dynamic differential scanning calorimetry (DSC) at heating rates of 2, 2.5, 3, and 3.5°C min⁻¹. X‐ray diffraction and transmission electron microscopy were utilized to evaluate the morphology of UP/10A and UP/30B nanocomposites. Kinetic parameters of cure reactions were evaluated using the advanced isoconversional method. The addition of nanoclay resulted in a decrease in the activation energy of the redox reaction compared to that of the neat UP resin. The pre‐exponential factor of the redox reaction for UP/10A and UP/30B was less than that of the neat UP. Results showed an increase in the concentration of styrene between Cloisite 10A platelets leading to a decrease in the intralayer styrene content. The high concentration of styrene between nanoclay layers may lead to the formation of polystyrene chains grafted on the alkyds chains. This homo‐polymerization was also observed in the variation of activation energy of UP/10A specimen versus the degree of conversion for 0.42 ≤ α ≤ 0.6 which is very close to the activation energy of free radical homo‐polymerization of styrene. POLYM. COMPOS., 34:1824–1831, 2013. © 2013 Society of Plastics Engineers     

Synthesis,polymerization, and properties of the allyl‐functional phthalonitrile

A novel bisphthalonitrile monomer containing allyl groups (DBPA‐Ph) had been synthesized via the reaction of diallyl bisphenol A (DBPA) and 4‐nitrophthalonitrile. The chemical structure of DBPA‐Ph was confirmed by ¹HNMR, ¹³CNMR, and FTIR spectroscopy. The curing behaviors and processability of DBPA‐Ph were studied by differential scanning calorimetry (DSC) and dynamic rheological analysis. The monomer manifested a two‐stage thermal polymerization pattern. The first stage was attributed to the polymerization of allyl groups and the second to the ring‐form polymerization of cyano groups. The result of dynamic rheological analysis indicated the monomer had wide curing window and the self‐catalyzed curing behavior. DBPA‐Ph polymers were prepared from the thermal polymerization with short curing time, showing high glass transition temperature (>350°C) and attractive thermal decomposition temperature (>430°C). The outstanding glass transition temperature, desirable thermo‐oxidative stabilities, good processability and sound process conditions could provide more applications to the DBPA‐Ph polymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41203.     

Study on BMI modified allyl‐functional novolac resin/silica cloth composites: Effect of allylation degree on thermal and mechanical properties

A series of allyl‐functional novolac resin with various allylation degree, from 32.4 to 114.6%, were synthesized and then blended reactively with 4,4′‐bismaleimide biphenyl methane (BMI) at a weight ratio of 2.50:1 to get BMI‐modified allyl‐functional novolac (BMAN) resins. BMAN resins were used as matrix resin to fabricate BMAN/Silica cloth composites by compression molding process. Heat‐resistant properties of the composites were evaluated by means of dynamic mechanical analysis. The results indicated that thermal resistance of the composites increased as allylation degree of BMAN resins increased. Mechanical properties of the composites, including interlaminar shear strength (ILSS) and flexural strength at room temperature and 300°C, were determined, and the results showed that with increase in allylation degree of matrices the ILSS and flexural strength values of composites at room temperature decreased, but the values of ILSS and flexural strength at 300°C increased. Scanning electron microscope morphology analysis of fracture surface for composites revealed that tough interphase was responsible for the better mechanical properties of the composites based on lower allylation degree resins. POLYM. COMPOS., 28:180–185, 2007. © 2007 Society of Plastics Engineers     

Copolymerizing behavior and processability of allyl‐functional bisphthalonitrile/bismaleimide system

A prepolymer constituted with bisphthalonitrile containing allyl groups (DBPA‐Ph) and 4, 4′‐bis‐(maleimidodiphenyl)methane (BMI) was prepared. The reaction between DBPA‐Ph and BMI was characterized with FTIR. The copolymerization behavior and processability of DBPA‐Ph/BMI prepolymer was studied by differential scanning calorimetry (DSC) and dynamic rheological analysis. The results of DSC indicated that the DBPA‐Ph/BMI system presented two‐stage thermal polymerization attributing to the ene reaction between allyl moieties and maleimide at low temperature (around 263°C) and the ring‐form polymerization of cyano moieties at high temperature (around 332°C), respectively. The results of dynamic rheological analysis indicated, with the introduction of BMI, the curing properties of DBPA‐Ph/BMI system improved. The DBPA‐Ph/BMI copolymers were prepared with relatively shorter curing time and shown high glass transition temperature (>350°C). The DBPA‐Ph/BMI/glass fiber composite laminates were prepared and exhibited relatively better mechanical properties (>440 MPa) and satisfactory thermal properties (>440°C). The outstanding glass transition temperature, better processability, desirable thermal and thermo‐oxidative stabilities demonstrated the introduction of BMI would contribute to the application of DBPA‐Ph. POLYM. COMPOS., 38:1591–1599, 2017. © 2015 Society of Plastics Engineers     

Preparation and properties of novel hybrid resins based on acetylene‐functional benzoxazine and polyvinylsilazane

A serial of addition‐curable hybrid resins for resin matrix of advanced composites are prepared by thermal prepolymerization between acetylene‐functional benzoxazine(BZ) and polyvinylsilazane(PSN) with various weight ratios. Processing capability of BZ‐PSN resin is investigated by measuring viscosity. Cure behavior is investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FT‐IR) spectra. Thermal property of cured BZ‐PSN resin is investigated by Thermogravimetric analysis (TGA) and Dynamic mechanical analysis (DMA). BZ‐PSN resin shows a low viscosity of 40–180 mPa·s between 60 and 90°C, and maintains the low viscosity for 6 h, indicating that the resin is suitable for resin transfer molding (RTM) process to fabricate composites. DSC results show that BZ‐PSN resin can be cured completely at about 250°C without adding any other curing additives. FT‐IR shows the reaction between BZ and PSN take place. TGA shows that thermal stability of cured BZ‐PSN resin is increased with the content of polyvinylsilazane increasing both in nitrogen and in air. DMA shows cured hybrid resins have excellent thermal properties. The excellent processability and thermal properties suggest that BZ‐PSN resin is a promising candidate for resin matrix of advanced composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3794–3799, 2013     

Preparation and properties of melt‐blended polylactic acid/polyethylene glycol‐modified silica nanocomposites

One commercial type of fumed silica modified with methoxy polyethylene glycol (mPEG) plasticizer was incorporated into polylactic acid (PLA) biobased polymer to improve its performance. The modification on silica was confirmed through Fourier transform infrared spectra, nuclear magnetic resonance, and TGA assessments. The grafting percentage of mPEG onto silica was about 19.8 wt %. Transmission electron microscope revealed a similar degree of dispersion for control silica and modified silica‐filled PLA nanocomposites. Not much difference in the glass transition temperatures at various silica contents was found for PLA/control silica systems from the differential scanning calorimetry measurement, but the glass transition temperature of PLA/modified silica nanocomposite at 10 phr of modified silica showed up to 11°C decrement. It was suggested that the mPEG plasticizer efficiently plasticized the PLA matrix through the enhanced segmental mobility of PLA chains. Young's modulus of PLA was about 2133 ± 53 MPa, and the value for the nanocomposite increased to 2547 ± 54 MPa at 10 of phr control silica mainly due to the reinforcing effect from nanoparticles. For modified silica, Young's modulus decreased at various silica contents. The elongation at break for modified silica‐filled cases was higher than that of control silica‐filled cases. These results were attributed to the plasticizing effect of surface modifier. Optical transmittance for pristine PLA was generally in a similar order as PLA/control silica and modified silica cases at various silica contents. The results agreed with the morphology observation as well. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermomechanical properties of arylamine‐based benzoxazine resins alloyed with epoxy resin

Effects of epoxy resin on various arylamine‐based benzoxazine resins, i.e., aniline (BA‐a), m‐toluidine (BA‐mt), and 3,5‐xylidine (BA‐35x), have been investigated. Processing windows of BA‐35x, BA‐mt, and BA‐a were found to be widened with the amount of the epoxy. Gel points of benzoxazine‐epoxy resin mixtures can be predicted by an Arrhenius equation, e.g., gel time of BA‐35x and epoxy mixture at 70:30 mass ratio can be estimated by t_gel = 0.7012 × 10^?7 exp (10.563/T). Glass transition temperature (T_g) of BA‐a and BA‐mt alloyed with epoxy exhibited a synergistic behavior with the maximum T_g value at the benzoxazine‐epoxy composition of 80:20 mass ratio. However, in the BA‐35x and epoxy mixture, the decreasing trend in T_g from 241°C to 223°C with an addition of epoxy was observed. Furthermore, flexural strength and strain‐at‐break of those alloys were found to increase with increasing amount of the epoxy while modulus increased with the polybenzoxazine mass fraction. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Preparation and properties of phosphorus‐ and silicon‐modified phenolic resin with high ablation resistance

In order to further improve the ablation resistance of common phenolic resins, a modified phenolic resin containing phosphorus and silicon (SPPR) was synthesized and the corresponding properties were evaluated. With phosphorus and silicon involved in the macromolecule, SPPR showed excellent flame retardancy and obviously enhanced value (44.8%) of the limiting oxygen index. The thermal stability and charring performance of SPPR were greatly improved, with maximum decomposition temperature of over 500 °C and carbon yield of 60.1% in nitrogen. Differential scanning calorimetry indicated that the curing temperature shifted from 157 °C for the conventional phenolic resin to 182 °C for SPPR. Moreover, an improvement of impact strength from 4.3 to 16.5 kJ m^?2 confirmed that incorporation of flexible Si? O chain had a noticeable effect on the mechanical properties of SPPR. Such a modified phenolic resin has promising application prospects serving as an ablation material with high performance. © 2019 Society of Chemical Industry     

Preparation and characterization of organoclay‐rubber nanocomposites via a new route with skim natural rubber latex

Skim natural rubber latex (SNRL) is a protein rich by‐product obtained during the centrifugal concentration of natural rubber (NR) latex. A new method to recover rubber hydrocarbon and to obtain nanocomposites with organoclay (OC) was investigated. The approach involved treatment of SNRL with alkali and surfactant, leading to creaming of skim latex and removal of clear aqueous phase before addition of OC dispersion. Clay mixed latex was then coagulated to a consolidated mass by formic acid, followed by drying and vulcanization like a conventional rubber vulcanizate. X‐ray diffraction (XRD) studies revealed that NR nanocomposites exhibited a highly intercalated structure up to a loading of 15 phr (parts per hundred rubber) of OC. Transmission electron microscopy studies showed a highly exfoliated and intercalated structure for the NR nanocomposites at loadings of 3–5 phr organically modified montmorillonite (OMMT). The presence of clay resulted in a faster onset of cure and higher rheometric torque. The rubber recovered from skim latex had a high gum strength, and a low amount of OC (5 phr) improved the modulus and tensile strength of NR. The high tensile strength was supported by the tensile fractography from scanning electron microscopy. Thermal ageing at 70°C for 6 days resulted in an improvement in the modulus of the samples; the effect was greater for unfilled NR vulcanizate. The maximum degradation temperature was found to be independent of the presence and concentration of OC. The increased restriction to swelling with the loading of OC suggested a higher level of crosslinking and reinforcement in its presence. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3277–3285, 2006     

Preparation and characterization of polysiloxane‐modified epoxy resin aqueous dispersions and their films

Polysiloxane‐modified epoxy resin aqueous dispersions were prepared by the reaction of amino‐polysiloxane (APS) with a graft epoxy resin that was synthesized with a diglycidyl ether of bisphenol A type epoxy resin and styrene/acrylic acid. The measurements of the epoxy values and FTIR spectra confirmed that this reaction really took place. The modified aqueous dispersion exhibits high viscosity, small particle size, and nearly the same surface tension as the unmodified one. Therefore, this indicates that the siloxane segments could be encapsulated into graft epoxy resin particles during the water dispersion process. For APS‐modified films, the thermal stability and water resistance are remarkably enhanced. Furthermore, lowering of the hardness and surface tension for these films was also observed and the surface composition was measured by X‐ray photoelectron spectroscopy. The experimental data indicate that the siloxane segments easily migrate onto the surface during the film formation process and finally enrich on the surface of the APS‐modified film. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 880–885, 2005     

Microcompounding of organoclay–ABS/PA6 blend‐based nanocomposites

In this study, acrylonitrile–butadiene–styrene (ABS) and polyamide‐6 (PA6) were blended in the presence of an olefin‐based compatibilizer and organoclays. The effects of ABS to PA6 ratio, clay content, and screw speed of the microcompounder were examined by performing morphological (i.e., XRD, SEM, and TEM) and tensile tests. The average aspect ratio of the clay platelets after processing was obtained by applying semiautomatic image analysis method. SEM analysis showed that addition of the compatibilizers to the ABS/PA6 blend system resulted in a decrease in diameter of dispersed phase when one of the phases was continuous. The addition of 5 wt% compatibilizer altered the dispersed morphology to cocontinuous morphology when the weight percentage of ABS was equal to that of PA6. The results of XRD analysis implied that clays were exfoliated in the presence of PA6. It was observed in TEM micrographs that clays were selectively dispersed in PA6 phase. Aspect ratio of the platelets increased as the PA6 content increased. Moduli of the nanocomposites were improved by enriching blend with PA6 and increasing screw speed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Crown ether‐modified clays and their polystyrene nanocomposites

Crown ether‐modified clays were obtained by the combination of sodium and potassium clays with crown ethers and cryptands. Polystyrene nanocomposites were prepared by bulk polymerization in the presence of these clays. The structures of nanocomposites were characterized by X‐ray diffraction and transmission electron microscopy. Their thermal stability and flame retardancy were measured by thermogravimetric analysis and cone calorimetry, respectively. Nanocomposites can be formed only from the potassium clays; apparently the sodium clays are not sufficiently organophilic to enable nanocomposite formation. The onset temperature of the degradation is higher for the nanocomposites compared to virgin polystyrene, and the peak heat release rate is decreased by 25% to 30%.     

New thermosetting resin from terpenediphenol‐based benzoxazine and epoxy resin

Terpenediphenol‐based benzoxazine was prepared from terpenediphenol, formaline, and aniline. Curing behavior of the benzoxazine with 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 properties of the cured resin both from neat resins and from reinforced resins with fused silica were evaluated, respectively. The cured resins showed good heat resistance, mechanical properties, electrical insulation, and especially water resistance, compared with the cured resin from bisphenol A type novolac and epoxy resin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2266–2273, 1999