Effect of ortho‐diallyl bisphenol A on the processability of phthalonitrile‐based resin and their fiber‐reinforced laminates

Sluggish and narrow process window of phthalonitrile resin has tremendously limited their wide applications. In this work, a novel phthalonitrile containing benzoxazine (4,4′‐(((propane‐2,2‐diylbis (2H‐benzo [e] [1,3]oxazine‐6,3 (4H)‐diyl) bis(3,1‐phenylene))bis(oxy)) diphthalonitrile, BA‐ph) with ortho‐diallyl bisphenol A (DABPA) was investigated. The processing window of the BA‐ph/DABPA blends were found from 50°C to 185°C, which was significantly broader than that of the pure BA‐ph (120–200°C). The composites were prepared through a curing process involving sequential polymerization of allyl moieties, ring‐opening polymerization of oxazine rings and ring‐forming polymerization of nitrile groups. BA‐ph/DABPA/GF(glass fiber) composite laminates were prepared in this study, and the composite laminate with BA‐ph/DABPA molar ratio of 2/2 showed an outstanding flexural strength and modulus of 560 MPa and 37 GPa, respectively, as well as a superior thermal and thermo‐oxidative stability up to 408 and 410°C. These outstanding properties suggest that the BA‐ph/DABPA/GF composites are suitable candidates as matrices for high performance composites. POLYM. ENG. SCI., 56:150–157, 2016. © 2015 Society of Plastics Engineers     

Curing behavior and processability of BMI/3‐APN system for advanced glass fiber composite laminates

The prepolymers containing bismaleimide (BMI) and 3‐aminophenoxyphthalonitrile (3‐APN) were prepared through simple solution prepolymerization, and the corresponding curing behaviors and processability were investigated by differential scanning calorimetry and dynamic rheological analysis. The results showed that the processability of the prepolymers could be controlled by temperature and time on processing, also depended on the relative content of 3‐APN and BMI. The possible curing reactions of the prepolymers were studied by Fourier transform infrared spectroscopy, which involved the Michael addition between BMI and 3‐APN and self‐polymerization of BMI or 3‐APN. The resulting polymers displayed high thermo‐oxidative stabilities (T_5% > 425 °C) and good adhesion capability. Furthermore, BMI/3‐APN systems were employed to prepare BMI/3‐APN/glass fiber (GF) composite laminates and their morphological, mechanical, and electrical stable properties were also investigated. The BMI/3‐APN/GF laminates exhibited the improvement of the mechanical properties (the maximum flexural strength is 633.5 MPa and flexural modulus is 38.7 GPa) compared with pristine BMI/GF laminates because of the strong interfacial adhesions between GF and matrices, which was confirmed with SEM observations. This study provides a concise strategy for diversifying the preparation of BMI/3‐APN prepolymers to obtain advanced GF composite laminates with various properties which have potential applications in industrial manufacture or electronic circuit, and so on. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43640.     

Mechanical,thermal, electrical,and interfacial properties of high‐performance bisphthalonitrile/polyarylene ether nitrile/glass fiber composite laminates

Bisphthalonitrile (BAPh)/polyarylene ether nitrile end‐capped with hydroxyl groups (PEN‐OH) composite laminates reinforced with glass fiber (GF) have been fabricated in this article. The curing behaviors of BAPh/PEN‐OH prepolymers have been characterized by differential scanning calorimetry and dynamic rheological analysis. The results indicate that with the introduction of PEN‐OH the curing temperature of BAPh has decreased to 229.6–234.8°C and BAPh/PEN‐OH prepolymers exhibit large processing windows with relatively low melt viscosity. The BAPh/PEN‐OH/GF composite laminates exhibit tensile strength (272.4–456.5 MPa) and modulus (4.9–10.0 GPa), flexural strength (507.1–560.9 MPa), and flexural modulus (24.0–30.4 GPa) with high thermal (stable up to 538.3°C) and thermal stabilities (stable up to 475.5°C). The dielectric properties of BAPh/PEN‐OH/GF composite laminates have also been investigated, which had little dependence on the frequency. Meanwhile, scanning electron microscopy results show that the BAPh/PEN‐OH/GF composite laminates display excellent interfacial adhesions between the matrix and GFs. Herein, the BAPh/PEN‐OH matrix can be a good matrix for high‐performance polymeric materials and the advanced BAPh/PEN‐OH/GF composite laminates can be used under high temperature environment. POLYM. COMPOS., 34:2160–2168, 2013. © 2013 Society of Plastics Engineers     

Preparation and properties of bisphenol A‐based bis‐phthalonitrile composite laminates

A series of bisphenol A (BPA)‐based 2,2‐bis‐[4‐(3,4‐dicyanophenoxy)phenyl]propane (BAPh) prepolymers and polymers were prepared using BPA as a novel curing agent. Ultraviolet–visible and Fourier transform infrared spectroscopy spectrum were used to study the polymerization reaction mechanism of the BAPh/BPA polymers. The curing behaviors were studied by differential scanning calorimetry and dynamic rheological analysis, the results indicated that the BAPh/BPA prepolymers exhibit large processing windows (109.5–148.5°C) and low complex viscosity (0.1–1 Pa·s) at moderate temperature, respectively. Additionally, the BAPh/BPA/glass fiber (GF) composite laminates were manufactured and investigated. The flexural strength and modulus of the composite laminates are 548.7–632.8 MPa and 25.7–33.2 GPa, respectively. The thermal stabilities of BAPh/BPA/GF composite laminates were studied by thermogravimetry analysis. The temperatures at 5% weight loss (T_5%) of the composite laminates are 508.5–528.7°C in nitrogen and 508.1–543.2°C in air. In conclusion, the BAPh/BPA systems can be used as superior matrix materials for numerous advanced composite applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Heat‐distortion temperature of unidirectional polyethylene–glass fiber–PMMA hybrid composite laminates

Unidirectional (UD) composite laminates based on high‐performance polyethylene fibers (PEF) and glass fibers (GF) and their hybrids were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF, 147°C) for 2 h. The heat distortion temperatures (HDT) of the composites were measured and analyzed. The dependency of the HDT correlated with the wettability of the fibers, measured from the contact angle. The HDT of the composites increased with increasing GF content but decreased when PEF was used. An optimum combination of different properties was obtained by using PEF/GF/PMMA hybrid composites, with GF ply/plies on the lower tension side of the UD laminates. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 541–545, 1999     

Characterization of a rigid silicone resin

Silicone resins have been used as binders for ceramic frit coatings and can withstand temperatures of 650°C to 1260°C. Conceptually, silicone resins can potentially be used as matrices for high temperature fiber‐reinforced composites. The mechanical and thermal properties of a commercially available silicone resin, Dow Corning® 6‐2230, were characterized. Neat 6‐2230 resin was found to have inferior room temperature mechanical properties such as flexural, tensile and fracture properties when compared to epoxy. The room temperature flexural properties and short beam shear strength of the silicone/glass composites were also found to be lower than those of epoxy/glass composite with similar glass content. However, the silicone resin had better elevated temperature properties. At an elevated temperature of 316°C, the retentions of flexural modulus and strength were 80% and 40% respectively of room temperature values; these were superior to those of phenolic/glass. Unlike the carbon‐based resins, the drop in flexural properties of the silicon/glass laminates with temperature leveled off with increase in temperature beyond 250°C. The resin weight loss at 316°C in 100 cm³/min of flowing air was small compared to other carbon‐based resins such as PMR‐15 and LaRC TPI. Only Avimid‐N appeared comparable to Dow Corning® 6‐2230.     

Effect of processing conditions on physical properties of 3‐aminophenoxyphthalonitrile/epoxy laminates

To develop high performances of polymer composite laminates, differential scanning calorimetry and dynamic rheological analysis studies were conducted to show curing behaviors of 3‐aminophenoxyphthalonitrile/epoxy resin (3‐APN/EP) matrix and define cure parameters of manufacturing processes. Glass fiber reinforced 3‐APN/EP (GF/3‐APN/EP) composite laminates were successfully prepared through different processing conditions with three parameters such as pressures, temperatures, and time. Based on flexure tests, dynamic mechanical analysis, thermal gravimetric analysis, and scanning electron microscope, the complementary catalytic effect of the three processing parameters is investigated by studying mechanical behavior, thermomechanical behavior, thermal behavior, and fracture morphology of GF/3‐APN/EP laminates. The 50/50 GF/3‐APN/EP laminates showed a significant improvement in flexural strength, glass transition temperature (T_g), and thermal stability with favorable processing parameters. It was also found that the T_g and thermal stability were significantly improved by the postheated treatment method. The effect of manufacturing process provides a new and simple route for the polymer–matrix composites application, which indicates that the composites can be manufactured at low temperatures. But, they can be used in a high temperature environment. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39746.     

Influence of thermo‐oxidative aging on the dynamical mechanical properties and thermal degradation kinetics of glass fiber‐reinforced PA10T composites

Unveiling the fundamental thermal‐oxidative aging mechanism and thermal degradation kinetics of the poly(decamethyleneterephthalamide) (PA10T)/ glass fiber (GF) composites under different aging temperatures (160°C, 200°C, and 240°C) for 0–50 days will facilitate the understanding of the interaction between matrix PA10T and GF. The results revealed that the decrease of mechanical properties referring to tensile strength, flexural strength and notched impact strength, and the occurrence of debonding phenomenon between PA10T matrix and GF were increasingly obvious after longer aging time at higher aging temperature. At the same time, the decline of crystalline was mainly ascribed to the thermal‐oxidative aging effect, which triggered the deterioration of mechanical properties of PA10T/GF composites. Accordingly, the enhancement of rigidity were probably attributed to the higher temperature aging effect with the aging time prolonging in PA10T/GF composites, while the interfacial debonding between GF and resin matrix obviously occurred with the increase of aging time. In a word, it is believed that investigating the fundamental thermal‐oxidative aging of PA10T/GF composites would be beneficial to optimize and control the service life and applications of materials. POLYM. ENG. SCI., 59:643–656, 2019. © 2018 Society of Plastics Engineers     

Phthalonitrile-carbon fiber composites

Phthalonitrile polymers offer promise as matrix materials for advanced composite applications. The phthalonitrile monomer is readily converted to a highly crosslinked thermosetting polymer in the presence of thermally stable organic amine catalysts. Rheometric studies were conducted to elucidate the optimum amine concentration for composite formulations. High quality composite panels were processed in an autoclave using unsized IM7 carbon fibers. Mechanical properties of the phthalonitrile/carbon composite are either better than or comparable to the state-of-the-art PMR-15 composites. Dynamic mechanical analysis reveal that samples postcured at elevated temperatures (375°C) do not exhibit a glass transition temperature up to 450°C and also retain °90% of their initial modulus at 450°C. Flame resistance of phthalonitrile/carbon composites, evaluated by cone calorimetric studies, excels over that of other polymeric composites for marine applications. The composites also show low water uptake, <1% after exposure to water for 16 months.     

Bio-resourced eugenol derived phthalonitrile resin for high temperature composite

Eugenol (EG) is an abundant renewable compound that has been widely used in the synthesis of bio-based thermosetting resin, but there are few reports on the phthalonitrile (PN) resin derived from EG. In this study, a new kind of bio-based PN resin (MEG-PN) derived from EG derivative was successfully synthesized. PN is a traditional class of high-performance thermosets with poor processability for its ultra-high melting point and curing temperature. The MEG-PN resin possesses excellent processability: its melting temperature is much lower (77°C), and it can be cured at a moderate temperature (281°C) in the absence of curing agents. The cured MEG-PN resin exhibited great heat resistance according to its 5% weight loss temperature at 448°C and its char yield percentage as high as 75.6% at 800°C under nitrogen. The properties of the carbon-fiber reinforced MEG-PN composite were comparable to those of petroleum-based PN resins: the glass transition temperature was around 397°C; the flexural strength and modulus were as high as 756 MPa and 119 GPa, respectively. Overall, a bio-based PN thermoset with great comprehensive performance was synthesized possessing the potential in the application of advanced composite.     

Tuning the interlaminar shear strength and thermo-mechanical properties of glass fiber composites by incorporation of (3-mercaptopropyl) trimethoxysilane-functionalized carbon black

The incorporation of functionalized nanoscale fillers into traditional glass fiber/unsaturated polyester (GF/UPE) composites provides a more robust mechanical attributes. The current study demonstrates the potential of 3-mercaptopropyl trimethoxysilane (MPTS)-functionalized carbon black (f-CB) for enhancing the thermo-mechanical properties of GF composites. The composites infused with 1, 3 and 5 wt% of pristine and MPTS-functionalized CB were fabricated by hand lay-up and hot press processing. Tensile testing, interlaminar shear strength (ILSS) testing and dynamic mechanical analysis were used to evaluate the performance of nanocomposites. Fourier transform infrared spectroscopy validated the MPTS functionalization of CB. Pristine CB-loaded nanocomposites exhibited marginal improvement in ultimate tensile strength (UTS), ILSS and thermo-mechanical properties. However, with the addition of f-CB, the improvement in all the studied properties was more substantial. The inclusion of 5 wt% f-CB increased the elastic modulus and UTS by 16 and 22%, respectively, whereas the ILSS was enhanced by 36%, in comparison to the neat GF composite. The scanning electron microscope analysis of fractured ILSS samples revealed better fiber-matrix adhesion and compatibility in f-CB-loaded nanocomposites. At the same filler weight percentage, the storage modulus at 25 °C was ~ 19% higher than that of neat composite. The f-CB inclusion resulted in increment of T _g by ~ 13 °C over the T _g of neat GF/UPE composite (~ 109 °C). These improvements were due to the chemical connection of f-CB to the UPE matrix and GF surface. With such improvements in thermal and mechanical properties, these nanocomposites can replace the conventional GF composites with prominent improvements in performance.     

Highly processable ternary systems based on benzoxazine,epoxy, and phenolic resins for carbon fiber composite processing

Effects of resin compositions in ternary systems of benzoxazine, epoxy, and phenolic novolac resins on processability, and thermomechanical properties of their carbon fiber‐reinforced composites are investigated. At suitable range of resin mass ratios, the ternary mixtures can provide a relatively wide processing window ranging from 50 to 200°C by maintaining their low A‐stage viscosity for a relatively long time which is crucial in the fiber preimpregnating process. Furthermore, relatively long shelf‐life of the ternary mixtures stored at room temperature (～ 30°C) up to 270 days is obtained with minimal effect on their processability. The optimum mass ratio of B : E : P was determined to be 3 : 6 : 2, i.e., BEP362 resin. Finally, the carbon fiber composite based on BEP362 was found to exhibit substantial enhancement in its mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of quasi‐carbonization processing parameters on the mechanical properties of quasi‐carbon/phenolic composites

In this work, quasi‐carbon fabrics were produced by quasi‐carbonization processes conducted at and below 1200°C. Stabilized polyacrylonitrile (PAN) fabrics and quasi‐carbon fabrics were used as reinforcements of phenolic composites with a 50 wt %/50 wt % ratio of the fabric to the phenolic resin. The effect of the quasi‐carbonization process on the flexural properties, interfacial strength, and dynamic mechanical properties of quasi‐carbon/phenolic composites was investigated in terms of the flexural strength and modulus, interlaminar shear strength, and storage modulus. The results were also compared with those of a stabilized PAN fabric/phenolic composite. The flexural, interlaminar, and dynamic mechanical results were quite consistent with one another. On the basis of all the results, the quasi‐static and dynamic mechanical properties of quasi‐carbon/phenolic composites increased with the applied external tension and heat‐treatment temperature increasing and with the heating rate decreasing for the quasi‐carbonization process. This study shows that control of the processing parameters strongly influences not only the mechanical properties of quasi‐carbon/phenolic composites but also the interlaminar shear strength between the fibers and the matrix resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dynamic mechanical study on unidirectional polyethylene fibers-PMMA and glass fibers-PMMA composite laminates

Unidirectional (UD) composite laminates based on glass fibers (GF) and high-performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature and then heated at 55°C (well below the softening point of PEF) for 2 hrs. The viscoelastic behavior of the composite was studied through dynamic mechanical analysis at different volume fractions of fibers. Several parameters such as storage modulus (E′), loss modulus (E″), and loss factor or damping efficiency (tan ∂) were determined to be between 40 and 160°C in a resonant frequency mode. All the properties were compared between the two composite laminates. It was found that the shift of the glass transition temperature (T_g) due to incorporating fibers was higher in the case of a PEF-reinforced composite than that of a GF-reinforced composite at the same volume fraction of fibers. It was also observed that the efficiency of both the composites decreases with the increase in the volume fraction of fibers. © 1996 John Wiley & Sons, Inc.     

Design of the phthalonitrile‐based composite laminates by improving the interfacial compatibility and their enhanced properties

Phthalonitrile containing benzoxazine (BA‐ph) and cyanate ester (CE) were chosen as the thermosetting matrix and the glass fiber (GF) reinforced laminates formed at low temperature were designed. The polyarylene ether nitriles containing pendent carboxyl groups (CPEN) was selected to modify the interfacial interaction between the resin matrix and GFs. Two methods of introducing CPEN were compared and the effects of CPEN on curing behaviors and properties of the composites were investigated. Results showed that with the CPEN, exothermic peaks shifted to lower temperature and curing temperatures of BA‐ph/CE decreased slightly. The mechanical and thermal properties of GF‐reinforced composites were discussed and the results indicated that the composites of modified GFs with CPEN exhibited outstanding mechanical properties, higher glass transition temperature (T_g > 290 °C) than that of composites composed of CPEN mixed with BA‐ph/CE. Moreover, GF‐reinforced composites showed stable dielectric constants (3.8–4.5) and low dielectric loss (0.005–0.01), which were independent of the frequency. In sum, the various methods of the introduction of CPEN in the GF‐reinforced composites may provide a new route to prepare improved composites, meanwhile, composites with outstanding processability and excellent mechanical and thermal properties are expected to be widely applied in the fields of high‐performance structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45881.     

Pultruded fiber-reinforced polyurethane-toughened phenolic resin. II. Mechanical properties,thermal properties,and flame resistance

A novel process has been developed to toughen phenolic resin by polyurethane for fiber-reinforced pultruded composites. The mechanical properties of the composites (tensile strength, flexural strength, and notched Izod impact strength) approach maximum values at 10 wt% of the blocked polyurethane content. The fabricated composites show good mechanical properties and possess low void fraction. Notched Izod impact strength of the composite (with 5 wt% polyurethane content) increases by more than 30% compared to the virgin composite. The thermogravimetric analysis (TGA) showed that the temperature for the 5% weight loss of the phenolic/polyurethane copolymer decreases with the increasing of the polyurethane content; however, the thermal degradation temperature is still higher than 350°C. Differential scanning calorimetric analysis (DSC) showed that the onset point of copolymer is 20°C higher than that of the virgin one. The presence of the blocked polyurethane may hinder the polymerization of phenolic resin. The modified composite shows excellent dimensional stability. The copolymer composite also possesses good fire resistance. © 1996 John Wiley & Sons, Inc.     

Processing robustness for a phenylethynyl‐terminated polyimide composite

The processability of a phenylethynyl‐terminated imide resin matrix (PETI‐5) composite was investigated. Unidirectional prepregs were made through the coating of an N‐methylpyrrolidone solution of an amide acid oligomer (PETAA‐5/NMP) onto unsized IM7 fibers. Two batches of prepregs were used: one was made by the National Aeronautics and Space Administration in house, and the other was from an industrial source. The composite processing robustness was investigated with respect to the prepreg shelf life, the effect of B‐staging conditions, and the optimal processing window. The prepreg rheology and open hole compression (OHC) strengths were not to affected by prolonged ambient storage (i.e., up to 60 days). Rheological measurements indicated that the PETAA‐5/NMP processability was only slightly affected over a wide range of B‐stage temperatures (from 250 to 300°C). The OHC strength values were statistically indistinguishable among laminates consolidated under various B‐staging conditions. An optimal processing window was established with response surface methodology. The IM7/PETAA‐5/NMP prepreg was more sensitive to the consolidation temperature than to the pressure. A good consolidation was achievable at 371°C (700°F)/100 psi, which yielded a room‐temperature OHC strength of 62 ksi. However, the processability declined dramatically at temperatures below 350°C (662°F), as evidenced by the OHC strength values. The processability of the IM7/PETI‐5 prepreg was robust. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3212–3221, 2006     

Mechanical and thermal enhancements of benzoxazine‐based GF composite laminated by in situ reaction with carboxyl functionalized CNTs

An easy and efficient approach by using carboxyl functionalized CNTs (CNT‐COOH) as nano reinforcement was reported to develop advanced thermosetting composite laminates. Benzoxazine containing cyano groups (BA‐ph) grafted with CNTs (CNT‐g‐BA‐ph), obtained from the in situ reaction of BA‐ph and CNT‐COOH, was used as polymer matrix and processed into glass fiber (GF)‐reinforced laminates through hot‐pressed technology. FTIR study confirmed that CNT‐COOH was bonded to BA‐ph matrices. The flexural strength and modulus increased from 450 MPa and 26.4 GPa in BA‐ph laminate to 650 MPa and 28.4 GPa in CNT‐g‐BA‐ph/GF composite, leading to 44 and 7.5% increase, respectively. The SEM image observation indicated that the CNT‐COOH was distributed homogeneously in the matrix, and thus significantly eliminated the resin‐rich regions and free volumes. Besides, the obtained composite laminates showed excellent thermal and thermal‐oxidative stabilities with the onset degradation temperature up to 624°C in N₂ and 522°C in air. This study demonstrated that CNT‐COOH grafted on thermosetting matrices through in situ reaction can lead to obvious mechanical and thermal increments, which provided a new and effective way to design and improve the properties of composite laminates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of polyarylene ether nitriles on processing and mechanical behaviors of phthalonitrile‐epoxy copolymers and glass fiber laminated composites

A series of copolymers and glass fiber composites were successfully prepared from 2,2‐bis [4‐(3,4‐dicyanophenoxy) phenyl] propane (BAPh), epoxy resins E‐44 (EP), and polyarylene ether nitriles (PEN) with 4,4′‐diaminodiphenyl sulfone as curing additive. The gelation time was shortened from 25 min to 4 min when PEN content was 0 wt % and 15 wt %, respectively. PEN could accelerate the crosslinking reaction between the phthalonitrile and epoxy. The initial decomposition temperatures (T_i) of BAPh/EP copolymers and glass fiber composites were all more than 350°C in nitrogen. The T_g of 15 wt % PEN glass fiber composites increased by 21.2°C compared with that of in comparison with BAPh/EP glass fiber composite. The flexural strength of the copolymers and glass fiber composites reached 119.8 MPa and 698.5 MPa which increased by 16.6 MPa and 127.3 MPa in comparison with BAPh/EP composite, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Tris-benzil crosslinked polyphenylquinoxalines

Polyphenylquinoxalines (PPQ) were crosslinked with a tris-benzil comonomer, to alleviate the inherenthigh temperature thermoplasticity, and evaluated as matrices in graphite reinforced composites. The room temperature flexural strength/modulus of Modmor IJ laminates were as high as 245,000 psi/16,6 × 10⁶ psi. Essentially 100 percent retention of ambient mechanical properties was obtained at 371°C using a PPQ matrix from the fully-crosslinked polymer prepared from 4,4′-bis(4″-oxybenzilyl) benzil (BOBB) and 3,3′-diaminQbenzrdine. The degree of high temperature thermoplasticity in the composite was found to be more closely related to the final postcure temperature than to the BOBB crosslink density. The thermoplasticity essentially disappeared when the BOBB comonomer-PPQ laminates were postcured at 482–510°C in nitrogen. Substitution of DMAC for the commonly used m-cresol solvent system allowed facile preparation of prepreg to fabricate low-void laminates and NOL rings.