Preparation and properties of high performance phthalide‐containing bismaleimide modified epoxy matrices

A series of intercrosslinked networks formed by diglycidyl ether of bisphenol A epoxy resin (DGEBA) and novel bismaleimide containing phthalide cardo structure (BMIPP), with 4,4′‐diamino diphenyl sulfone (DDS) as hardener, have been investigated in detail. The curing behavior, thermal, mechanical and physical properties and compatibility of the blends were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), notched Izod impact test, scanning electron microscopy (SEM) and water absorption test. DSC investigations showed that the exothermic transition temperature (T_p) of the blend systems shifted slightly to the higher temperature with increasing BMIPP content and there appeared a shoulder on the high‐temperature side of the exothermic peak when BMIPP content was above 15 wt %. TGA and DMA results indicated that the introduction of BMIPP into epoxy resin improved the thermal stability and the storage modulus (G′) in the glassy region while glass transition temperature (T_g) decreased. Compared with the unmodified epoxy resin, there was a moderate increase in the fracture toughness for modified resins and the blend containing 5 wt % of BMIPP had the maximum of impact strength. SEM suggested the formation of homogeneous networks and rougher fracture surface with an increase in BMIPP content. In addition, the equilibrium water uptake of the modified resins was reduced as BMIPP content increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of modified bismaleimide resins based on phthalide‐containing monomer

A series of bismaleimide resins based on phthalide‐containing monomer have been prepared by the copolymerization reaction of 3,3‐bis[4‐(4‐maleimidophenoxy)phenyl] ‐phthalide (PPBMI), 4, 4'‐dimaleimido diphenylmethane (MBMI) and 2, 2'‐diallyl bisphenol A (DABPA) in different feed ratios. The curing behavior, thermal, mechanical and physical properties and compatibility of all resultant resins were carefully characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), notched Izod impact test, water absorption test and scanning electron microscopy (SEM). DSC investigations showed that with an increase of the weight ratio of PPBMI, the dominating exothermic polymerization temperature (T_p) increased. The glass transitions were observed from DMA thermograms for the cured BMI resins in the temperature range from 277°C to 311°C and decreased with increasing PPBMI content. The TGA results indicated the thermal stability was improved as PPBMI content increased. The investigations of the mechanical properties showed a complicated trend with an increase in PPBMI content. In addition, the equilibrium water uptake of the modified resins was reduced as PPBMI content increased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1084‐1091, 2013     

Preparation and mechanical properties of high‐performance short ramie fiber‐reinforced polypropylene composites

Short ramie fiber (RF) was used to reinforce the polypropylene (PP). The composites were prepared in a twin‐screw extruder followed by injection molding. The experimental results showed that both the strength and the modulus of the composites increase considerably with increasing RF content. The tensile strength and flexural strength are as high as 67 and 80 MPa by the incorporation of ramie up to 30 wt %. To the best of our knowledge, this is one of the best results for short natural fiber‐reinforced PP composites. However, the preparation method in this study is more simple and economic. This short RF‐reinforced PP composites extend the application field for short‐nature fiber‐reinforced PP composites. Morphological analysis revealed that it is the high aspect ratio of the fiber and good interfacial compatibility that result in the high performance of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical enhancement of amine‐functionalized TiO2 reinforced polyimine composites

Polyimine vitrimers are known for their malleability, which endows these materials with properties such as self‐healing, recycling, and reshaping. To enhance the mechanical properties of the polyimine vitrimers, composites were fabricated by incorporating amine‐functionalized TiO₂ microspheres (amTiO₂MS) into polyimine matrix. The pure polyimine matrix and polyimine composites hybridized with TiO₂ microspheres (TiO₂MS) without surface modification were also obtained and examined as the controls in characterization. X‐ray powder diffraction, scanning electron microscopy, and energy dispersive X‐ray spectroscopy were employed to demonstrate the presence and distribution of amTiO₂MS and TiO₂MS in the polyimine matrices. The investigation of mechanical properties of the amTiO₂MS enhanced polyimine composites and control samples indicated that incorporation of amTiO₂MS and TiO₂MS exhibited different characteristic distribution, which strongly affected the performance of the composites. The optimal filling concentration of amTiO₂MS was found to be 3%, with which the microspheres were uniformly distributed in the polyimine matrix. The self‐healing behavior of the polyimine‐amTiO₂‐X was also studied. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46446.     

Kinetics modeling of carbon‐fiber‐reinforced bismaleimide composites under microwave and thermal curing

This article focuses on the analysis of the curing kinetics of carbon‐fiber‐reinforced bismaleimide (BMI) composites during microwave (MW) curing. A nonisothermal differential scanning calorimetry (DSC) method was used to obtain an accurate kinetic model. The degree of curing, chemical characterization, and glass‐transition temperature of the resin and composites cured by thermal and MW heating were analyzed with DSC, Fourier transform infrared spectroscopy, and dynamic mechanical analysis. The experimental results indicate that MW accelerated the crosslinking reaction of the BMI resin and had different effects on the reaction processes, especially for the glass‐transition temperature and chemical bonds. However, the curing reaction rate of the BMI resin decreased when the carbon fibers were added to the BMI resin during thermal and MW curing. According to the experimental results, the curing kinetic model of the BMI composite was used to provide a theoretical foundation for MW curing analysis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43770.     

Carbon fiber‐reinforced gelatin composites. I. Preparation and mechanical properties

Composites were made from carbon fibers and gelatin using a solvent‐casting or solution‐impregnation technique. Relationships between the fiber volume fraction (Vf), glycerol (plasticizer) content, gelatin content, fiber form, and mechanical properties (tensile strength and modulus, elongation at break, and shear strength) of the composites were investigated. In long carbon fiber gelatin composite (C_L/Gel), tensile strength, modulus, and shear strength increased steadily with the Vf. In the case of a short carbon fiber gelatin composite (C_S/Gel), an initial improvement in tensile strength and modulus was followed by a reduction, whereas the shear strength improved with the Vf and then reached a constant value. The elongation decreased with the Vf for both composites. It is shown that C_L/Gel had higher values of strength, modulus, and elongation than did C_S/Gel at any Vf level. The effects of glycerol and gelatin contents on the mechanical properties of the composites were found to be much less significant as compared to the Vf. According to scanning electron microscopic observation of the fracture surfaces, the fibers were uniformly distributed in the gelatin matrix, but the interfacial adhesion between the gelatin matrix and the carbon fibers was not very good for both composites. Fiber surface modification would be necessary to further improve the mechanical properties of the two composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 987–993, 2000     

Preparation and properties of an oxide fiber‐reinforced silica matrix composite

Oxide (Nextel? 440) fiber‐reinforced silica composites, with the density and porosity of 1.97 g/cm³ and 21.8%, were prepared through sol‐gel. Their average flexure strength, elastic modulus, shear strength, and fracture toughness at room temperature were 119.7 MPa, 25.6 GPa, 10.8 MPa, and 4.0 MPa·m^1/2, respectively. The composites showed typical toughened fracture behavior, and distinct pullout fibers were observed at the fracture surface. Their mechanical properties were performant up to 1000°C, with the maximum flexural strength of 132.2 MPa at 900°C. Moreover, the composites showed good thermal stability, even after thermal aging and thermal shock at elevated temperatures.     

Influences of different gravity environments on the curing process and cured products of carbon‐nanotube‐reinforced epoxy composites

The influences of different gravity environments on the curing process and the cured products of carbon‐nanotube‐reinforced epoxy composites were investigated in this study. Different gravity environments were simulated with a superconducting magnet on the basis of which resin matrix composites with different amino‐functionalized multiwalled carbon nanotube (NH₂‐MWCNT) concentrations of 0.1, 0.3, 0.5, and 1 wt % were tested. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, thermomechanical analysis (TMA), thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and three‐point bending tests were used to analyze the characteristics of different curing processes and cured products. From the results, we observed that the curing rate of the epoxy composites was influenced by different gravity values, and there was anisotropy in the NH₂‐MWCNT‐reinforced epoxy composites cured in the simulated microgravity environment. More effects of gravity on the curing process and cured products could be obtained through detailed experiments and discussion; this is important and fundamental for improving and enhancing the properties of composite materials used in different gravity environments. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41413.     

Mechanical properties and viscoelastic behavior of basalt fiber‐reinforced polypropylene

In the present article, a series of commercial‐grade polypropylenes (PP) filled with different contents of short basalt fibers were studied. This composite material presented deterioration of both mechanical characteristics, for example, stress and strain at yield with increasing of the fiber content. On the other hand, the impact strength was fourfold higher than that of unfilled PP. A poor adhesion between the PP matrix and the basalt fibers was detected. This is why interfacial interactions were promoted by the adding of poly(propylene‐g‐maleic anhydride) (PP‐g‐MA). It was observed that the tensile properties of the obtained materials and their impact strengths increased significantly with increasing of the amount of PP‐g‐MA in the blend. The adhesion improvement was confirmed by scanning electron microscopy as well. Fourier transform infrared spectroscopy was applied to assess if any chemical interactions in the system PP/PP‐g‐MA/basalt fibers exist. Dynamic mechanical thermal analysis data showed an increase of the storage modulus with increasing fiber content. The conclusion was made that the modification of the PP matrix led to a higher stiffness but its value remained constant, irrespective of the PP‐g‐MA content. With increasing fiber content, damping in the β‐region decreased, but increase of the coupling agent content restored its value back to that of PP. The loss modulus spectra presented a strong influence of fiber content on the α‐relaxation process of PP. The position of the peaks of the above‐mentioned relaxation processes are discussed as well. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 523–531, 1999     

Fluorinated bismaleimide resin with good processability,high toughness,and outstanding dielectric properties

In this study, novel fluorinated bismaleimide (BMI) resins were prepared by the copolymerization of 2,2′‐bis[4‐(4‐maleimidephenoxy)phenyl]hexafluoropropane (6FBMP) and diallyl hexafluorobisphenol A (6FDABPA) to enhance their dielectric properties. The dielectric properties of the resins were investigated in the frequency range 7–18 GHz through a cavity method. Through the incorporation of a hexafluoroisopropyl group with the polymer chain, the dielectric constant (ε) was effectively decreased because of the small dipole and the low polarizability of the carbon‐fluorine (C? F) bonds. The 6FBMP/6FDABPA resin possessed excellent dielectric properties, with ε being 2.88 and the dielectric loss being 0.009 at 10 GHz and 25°C. In comparison with the 4,4′‐bismaleimidodiphenylmethane (BDM)/2,2′‐diallyl bisphenol A (DABPA) resin, the glass‐transition temperature (T_g) of 6FBMP/6FDABPA decreased. The flexible ether group in the long chain of 6FBMP was considered to disrupt chain packing and cause a decreased crosslinking density and a lower T_g. 6FBMP/6FDABPA showed a similar thermal decomposition temperature and good thermal properties like the BDM/DABPA resin, whereas the impact strength of the 6FBMP/6FDABPA resin was almost 1.6 times higher than that of the BDM/DABPA resin. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42791.     

Preparation and properties of novel,flexible, lead‐free X‐ray‐shielding materials containing tungsten and bismuth(III) oxide

Novel, flexible, lead‐free X‐ray‐shielding composites were prepared with a high‐functional methyl vinyl silicone rubber (VMQ) matrix with W and Bi₂O₃ as filler materials. To verify the advanced properties of the lead‐free material, composites with the same mass fraction of PbO were compared. With the X‐ray energy ranging from 48 to 185 keV, the W/Bi₂O₃/VMQ composites exhibited higher X‐ray‐shielding properties. As the filler volume fraction decreased, the tensile strength, elongation, tear strength, and flexibility of the W/Bi₂O₃/VMQ composites increased. The Shore hardness of the W/Bi₂O₃/VMQ composites had a maximum value of 46.6 HA and was still very flexible. With decreasing filler volume fraction, the water‐vapor transmission performances of the W/Bi₂O₃/VMQ composites increased, and the W/Bi₂O₃/VMQ composites also showed better water‐vapor permeability. The heat‐transfer properties of the W/Bi₂O₃/VMQ composites increased with increasing W content, and when the W content exceeded 70 wt %, the thermal conductivity of the W/Bi₂O₃/VMQ material was about 70.45% higher than that of the PbO/VMQ composite. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43012.     

Structural and mechanical properties of needle‐punched nonwoven reinforced composites in erosive environment

Polypropylene‐based needle‐punched nonwoven reinforced epoxy composites have been fabricated and were evaluated for their thermomechanical response and dry erosion performance. The erosive wear investigations were carried out using silica sand particles as erodent with varying impact velocity, angles of impingement, fiber content, and stand‐off‐distance as the operating variables. Design of experiments (DoE) approach‐based Taguchi analysis was carried out to establish the interdependence of operating parameters and erosion rate. Impingement angle and impact velocity have been found to be the most significant determinants of erosive wear performance of such nonwoven reinforced composites. The composites were also observed to be appreciably resistant to impact content and indentations in addition to exhibiting the absence of any storage‐modulus decay till 60°C accompanied with a nominal increase in the primary transition temperature as revealed from loss‐tangent peaks. The composite with 30 wt % and 40 wt % of nonwoven materials have shown the highest and lowest erosion rates, respectively. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM) and their possible erosion mechanisms are discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology,thermal and mechanical properties of glass fiber‐reinforced crosslinkable poly(arylene ether nitrile)

Crosslinkable poly(arylene ether nitrile)/glass fiber (PEN/GF) composites with high thermal stabilities and mechanical properties were prepared by a economically and environmentally viable method of melt extrusion and injection molding. The feasibility of using PEN/GF composites was investigated by evaluating its morphological, rheological, thermal, and mechanical properties. The morphology shows a good dispersion and strong interfacial interaction between PEN and GF. Thermal studies reveal that the thermal stabilities of PEN/GF are improved significantly with increase of GF content. Mechanical investigation manifested that GFs have strengthening effect (increase in flexural, tensile, and impact strength) on the mechanical performance of PEN composites. Most importantly, crosslinking reaction of PEN/GF composites can further improve their mechanical performances, because a couple of GFs are agglomerated by thermal motion and strong interfacial adhesion and the local agglomeration does not break the global uniform distribution. This work shows that both the enhancement of GF content and the crosslinking reaction of PEN/GF composites are two key factors influencing the thermal and mechanical properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Heat‐damage assessment of carbon‐fiber‐reinforced polymer composites by diffuse reflectance infrared spectroscopy

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to assess the effects of heat damage on carbon‐fiber‐reinforced polymer composites. Moisture‐saturated graphite–epoxy laminates with a quasi‐isotropic lay‐up were heat‐damaged above their upper service temperatures. The loss of matrix‐dominated mechanical properties due to heat exposure was investigated in the laboratory under environmental testing conditions with mechanical tests, ultrasonic C‐scanning, and DRIFT spectroscopy. The reduction of the mechanical strength of the composite materials was accompanied by an increase in the carbonyl band integral and a decrease in the phenyl ratio and hydroxyl and hydrocarbon band integrals, as shown by the DRIFT spectra. DRIFT was confirmed to be more effective than ultrasonic inspection in evaluating the extent of heat damage, and a good correlation was found between the mechanical test results and DRIFT spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1222–1230, 2005     

Investigation of mechanical properties of alumina nanoparticle‐loaded hybrid glass/carbon‐fiber‐reinforced epoxy composites

This research work investigates the tensile strength and elastic modulus of the alumina nanoparticles, glass fiber, and carbon fiber reinforced epoxy composites. The first type composites were made by adding 1–5 wt % (in the interval of 1%) of alumina to the epoxy matrix, whereas the second and third categories of composites were made by adding 1–5 wt % short glass, carbon fibers to the matrix. A fourth type of composite has also been synthesized by incorporating both alumina particles (2 wt %) and fibers to the epoxy. Results showed that the longitudinal modulus has significantly improved because of the filler additions. Both tensile strength and modulus are further better for hybrid composites consisting both alumina particles and glass fibers or carbon fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39749.     

Strength,permeability, and durability of hybrid fiber‐reinforced concrete containing styrene butadiene latex

Hybrid fiber‐reinforced concrete (HFRC) is examined in this study. Two types of synthetic fibers were considered: polyvinyl alcohol fiber/macro synthetic fiber (PVA/MSF) and polypropylene fiber (PP)/MSF. Styrene butadiene latex was added at 0%, 5%, 10%, and 15% of the cement weight. Tests carried out for the study included compressive strength, flexural strength, chloride ion penetration, abrasion resistance, and impact resistance. The results demonstrated that higher latex contents improved the dispersibility of the fibers because of the increased workability of the HFRC and the improved adhesion. Formation of a latex film improved the strength, permeability resistance, abrasion resistance, and impact resistance. PVA/MSF HFRC had better properties than PP/MSF HFRC. This was attributed to stronger hydrogen bonding by the hydrophilic PVA fibers, which led to superior resistance to micro‐cracking and crack propagation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

High‐performance polymeric materials with greatly improved mechanical and thermal properties from cyanate ester/benzoxazine resin reinforced by silane‐treated basalt fibers

This present article investigates the effect of silane‐treated basalt fibers (TBFs) on the morphological, mechanical and thermal properties of cyanate ester/benzoxazine (CE/BOZ) resin composites. The characterization was made using a scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), flexural test, impact strength (IS) test, microhardness test, dynamic scanning calorimetry, and thermogravimetric analysis. The mechanical test results inferred the distinctive improvements in the values of the flexural strength and modulus, IS, and microhardness of the CE/BOZ composites. The thermal stabilities in terms of the T_g, T_5%, T_10%, and T_HRI were appreciably improved and were higher than those of the pure CE/BOZ resin. Data from the SEM and FTIR tests ascertained the good dispersion and adhesion between the TBFs and the resin matrix, which might be behind the significant enhancement in the ultimate performances of the composites, with respect to the distinguished properties of BFs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46283.     

Preparation and characterization of graphene oxide reinforced PVA film with boric acid as crosslinker

PVA films were prepared through aqueous solution method, and boric acid (BA) as well as graphene oxide (GO) was added to improve the mechanical and thermal properties. It was found that 5 wt % BA could increase the tensile strength threefold (from 23.3 to 67.7 MPa), and the incorporation of 0.2 wt % GO would provide additional percentage growth of 30% (from 67.7 to 88.5 MPa). Moreover, an enhancement of thermal stability of PVA film was found when BA or GO filler was added. The reinforcement mechanisms of both BA and GO were investigated, and a competitive phenomenon that the addition of BA would influence the reinforcement effect of GO sheets was found. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42000.     

Preparation and properties of APPSSQ‐like/polyimide hybrid composites

Hydrolysis and condensation proceeded to generate 3‐aminopropyl polysilsesquioxane‐like (APPSSQ‐like) particles from 3‐aminopropyl triethoxysilane. An APPSSQ‐like particle includes two domains: crosslinking Si? O? Si networks inside and 3‐aminopropyl groups outside the particle. The APPSSQ‐like/polyimide (APPSSQ‐like/PI) hybrid composites were prepared from a solution of poly(amic acid) (PAA, polyimide precursor) and APPSSQ‐like particles using N,N‐dimethylacetamide as a solvent. Scanning electron microscopy (SEM) showed that the APPSSQ particle sizes were about 100 nm, and there was no obvious phase separation between the APPSSQ‐like particles and the PI matrix in the fracture surfaces of the hybrid films. Owing to the highly crosslinked Si? O? Si networks inside the APPSSQ‐like particles, the APPSSQ‐like/PI hybrid composites possessed desired properties such as improved thermal resistance and reduced coefficients of thermal expansion (CTE). The presence of covalent bonds between the APPSSQ‐like particles and the PI molecules improved the compatibility between these two components. Thus, the tensile strength increased with the APPSSQ‐like content, and the elongation at break also slightly increased with the APPSSQ‐like content. The initial tensile and storage moduli of the APPSSQ‐like/PI hybrid composites increased with the APPSSQ‐like content, which indicates that the mechanical properties of these hybrid composites were enhanced by the incorporation of the APPSSQ‐like content in the PI matrix. Furthermore, the glass transition temperatures of these composites increased with the APPSSQ‐like content because the adhesion between the APPSSQ‐like particles and the PI molecules restricts the PI chains' mobility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2865–2874, 2003     

Thermal,mechanical properties,and low‐temperature performance of fibrous nanoclay‐reinforced epoxy asphalt composites and their concretes

Epoxy asphalt (EA) concretes have been widely used in the pavement of orthotropic steel bridge decks. The objective of this study was to figure out the enhanced effects of natural fibrous attapulgite (ATT) as a reinforced nanofiller in ATT/EA nanocomposites through a comparison of the properties of the composites with a series of various nanoclay loadings. The rheological properties, glass transition, thermal stability, mechanical properties, and morphology of the ATT/EA composites were characterized. Furthermore, the low‐temperature flexibility of the ATT/EA concretes was investigated. The test results show that the addition of ATT had no significant effect on the rotational viscosity of EA in the initial stage of the curing reaction. In addition, the ATT/EA composites showed better performance than the neat one in thermal stability with a higher glass‐transformation temperature. The tensile strength and elongation at break of the ATT/EA composites at a loading of 0.5 wt % ATT were 21 and 22% higher than those of the neat EA. The addition of ATTs also enhanced the low‐temperature flexibility of the EA concretes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41694.