Preparation of polyester resin/graphene oxide nanocomposite with improved mechanical strength

Graphene oxide (GO) has attracted huge scientific interest due to its unique physical and chemical properties as well as its wide‐scale applicability including facile synthesis and high yield. Here, we report preparation of nanocomposites based on GO and unsaturated polyester resin (PE). The synthesized samples were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, and tensile strength measurements. A good dispersion of the GO sheets within the resin matrix was observed from the morphological analysis. A significant enhancement in mechanical properties of the PE/GO composites is obtained at low graphene loading. Around 76% improvement of tensile strength and 41% increase of Young's modulus of the composites are achieved at 3 wt % loading of GO. Thermal analysis of the composite showed a noticeable improvement in thermal stability in comparison to neat PE. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microstructure and mechanical properties of a polyethylene/polydimethylsiloxane composite prepared using supercritical carbon dioxide

A polymer composite of polyethylene (PE) and polydimethylsiloxane (PDMS) was prepared using supercritical carbon dioxide despite the two polymers usually being immiscible and possessing a phase‐separated morphology. This article reports in detail the preparation, microstructure, crystallinity, and mechanical properties of the resulting PE/PDMS composite. The formation mechanism of the PE/PDMS composite consisted of supercritical impregnation of an octamethylcyclotetrasiloxane (D4) monomer and an initiator into a PE substrate followed by in situ polymerization within the substrate. Differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering measurements showed that PE and PDMS were blended at the nanometer level. The PDMS generated in the amorphous region of PE did not affect its crystallinity. Dynamic viscoelastic analyses and tensile tests were used to measure the mechanical properties of the composites including storage and Young's modulus, fracture stress, and strain. These properties were found to depend on the composition of the composite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal expansion and mechanical properties of phenolic resin/ZrW2O8 composites

Phenolic resin/ZrW₂O₈ composites were successfully fabricated and their coefficient of thermal expansion (CTE) as well as mechanical properties was investigated. The CTE of the composites decreases from 46 × 10^–6 to 14 × 10^–6 K^?1 when the ZrW₂O₈ volume fraction increases from 0 to 52 vol %. The CTE of the composites is analyzed by some theoretical models; Schapery's upper bound provides the best estimate of the reduction in CTE. The Barcol hardness of the composites increases with an increase in the ZrW₂O₈ volume fraction. The bending strength of the composites with 19–25 vol % of ZrW₂O₈ fillers shows a maximum value of 130 MPa, which is 45% larger than that of phenolic resin without fillers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Modification of unsaturated polyester resin with bismaleimide

The modification of a commercially available unsaturated polyester resin with 4,4′‐bismaleimidodiphenylmethane is presented. The properties of the modified resins were compared with those of the nonmodified resin, and the resins were characterized in the noncured state and after curing. The results indicate that the addition of bismaleimide to unsaturated polyester resin not only improves its properties but also accelerates the curing reactions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2003–2007, 2001     

Self-healing performance assessment of epoxy resin and amine hardener encapsulated polymethyl methacrylate microcapsules reinforced epoxy composite

In order to study the effect of healing materials viscosity on the self-healing performance of polymer composite, mostly available epoxy resin of viscosity 10–12 Pa.s and amine hardener of viscosity 0.01–0.02 Pa.s were chosen as two different healing materials and successfully encapsulated. Effect of core to shell(c/s) ratio on the synthesis of epoxy microcapsules was investigated and 1:1 c/s ratio is suggested as an ideal ratio to synthesize epoxy capsules. Chemical structure and thermal decomposition patterns of both microcapsules and capsules reinforced composite were analyzed. Tensile strength, impact strength and fracture toughness of capsules reinforced self-healing epoxy composite were evaluated. It was observed that the toughness of epoxy composite increased with the increase in microcapsules concentration. An optimum healing efficiency of 66% was observed with the addition of 7.5 wt% epoxy and hardener microcapsules at equal weight ratio. Stresses developed in the pure epoxy composite crack front were analyzed using Ansys V18.1.     

Toughening of epoxy resin with functionalized core‐sheath structured PAN/SBS electrospun fibers

Core‐sheath structured electrospun fibers with styrene‐butadiene‐styrene (SBS) block copolymer as a rubbery core and polyacrylonitrile (PAN) as a hard sheath were prepared by coaxial electrospinning, and used to improve the toughness of epoxy resin. The surface of the fibers was aminated by reacting PAN with diethylenetriamine to improve the interfacial interaction between the fibers and epoxy. Scanning and transmission electron microscopies confirm the core‐sheath structure of the PAN/SBS fibers. The Charpy impact energy is increased by the addition of electrospun fibers. When the content of aminated core‐sheath fibers is 4 wt %, the Charpy impact energy is increased by 150%. Dynamic mechanical analysis shows that the glass transition temperature of epoxy is not decreased by the addition of core‐sheath fibers. The high impact resistance is attributed to the rubbery core of the fibers that can absorb and dissipate impact energy, and the chemical bonding between the fibers and epoxy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41119.     

环氧树脂/ABS复合材料的制备及性能表征

以环氧树脂为基体,苯乙烯-丙烯腈-丁二烯（ABS）树脂为增韧剂,制备了环氧树脂/ABS复合材料,讨论了增韧剂对复合材料的热性能和机械性能的影响。结果表明,ABS的添加可提高复合材料的断裂韧性。扫描电镜结果显示,基体的剪切屈服和橡胶颗粒的微孔洞是ABS增韧环氧树脂的主要增韧机理。     

环氧树脂/碳化硅复合材料的热性能及韧性

采用碳化硅作为增强剂制备了环氧树脂/碳化硅复合材料,考察了复合材料的热学及力学性能。实验结果表明,碳化硅的添加使环氧树脂的玻璃化温度提高。当碳化硅添加质量分数为3%时,复合材料的韧性与纯环氧树脂相比提高了35%。     

Mechanical properties of woodflour/linseed oil resin composites

The purpose of this project was to obtain new composites using filler and resin obtained from renewable resources, combining low cost and good mechanical properties. The matrix consisted of a polyester resin synthesized from linseed oil and further crosslinked with styrene in a peroxide‐initiated reaction. Composite materials made from the unsaturated polyester/styrene thermoset and containing various percentages of woodflour were prepared and tested. The relationships between the filler content, porosity fraction, and mechanical properties of the materials were evaluated. The bending modulus and strength of the composites were significantly higher than that of the matrix. Simple models were successfully applied in the analysis of the mechanical properties of the materials. The porosity effect was also considered in the model predictions. The results of the mechanical and dynamic mechanical tests, the scanning electron micrographs of surface fractures, and the adhesion parameter calculated from the strength models all indicated that there was a strong interfacial interaction between matrix and filler. Copyright © 2005 Society of Chemical Industry     

Manufacture and characterisation of a low cost carbon fibre reinforced C/SiC dual matrix composite

A porous two-dimensional C/C composite was produced via the polymer pyrolysis route using phenolic resin as the matrix precursor and polyacrilonitrile- (PAN-) or pitch-based carbon fibres as reinforcement. The resulting C/C composites were then densified using a modified polysilane followed by pyrolysis to convert the polymer into silicon carbide, sealing the pores in the C/C composite. Aiming to increase the ceramic yield of the infiltrated polysilane and to reduce its volumetric shrinkage during pyrolysis the polymer’s curing behaviour was modified by catalytic addition of 0.1% dicobaltoctacarbonyl [Co₂(CO)₈]. The densification procedure is very efficient in sealing cracks in the C/C composite with SiC. The obtained carbon fibre reinforced C/SiC dual matrix composites were subjected to flexural tests and dynamic mechanical analysis. The flexural and visco-elastic properties of the composite are dominated by the strength of the fibre/matrix interface rather than by the fibre strength or modulus. A correlation between the mechanical loss factor (tan δ) and the fracture behaviour of the composite is suggested.     

Properties of epoxy molding compound according to the pretreatment method of an amino‐silane coupling agent on epoxy or phenol resin

An amino‐functional silane coupling agent, which is an important component for epoxy molding compound (EMC), has been used by diverse methods, such as integral addition into a mixed powder and pretreatment on silica or on resin. However, the homogeneous dispersion of the amino‐functional silane coupling agent in mixed powder is limited with integral addition, and the possibility of white gel formation, sometimes causing gate blocking during the transfer‐molding process, due to the aggregation of silica with the coupling agent cannot be completely removed by it. The pretreatment of the amino‐functional silane coupling agent on silica has been adopted as an alternative process, but the process is expensive and limited in mass production. Although the pretreatment of the coupling agent on resin as another method has also been used by some EMC manufacturing companies, it has hardly been known in which resin phase, the epoxy or hardener, the silane coupling agent should be pretreated for better mechanical properties of EMC. In this study, the pretreatment of the amino‐functional silane coupling agent on epoxy or phenol resin, essential components of EMC, has been investigated with respect to the reaction during the pretreatment and the properties of EMC according to the different pretreatment methods. In the case of the pretreatment on epoxy, the amino‐functional silane coupling agent rapidly forms an adduct with epoxy via a ring‐opening reaction, whereas its alkoxy groups are well preserved. The glass‐transition temperature and flexural strength of the EMC by the application of the pretreatment method on epoxy are lower than those by the pretreatment on phenol. It is thought that the degree of linkage between the resin matrix and silica becomes lower because of the confinement of aminopropyltriethoxy silane (APTS) within the epoxy matrix through an irreversible reaction with epoxy in advance. In the case of the pretreatment on phenol, most of the alkoxy groups in the coupling agent are assumed to be replaced with protonic nucleophiles such as phenol, generating an equivalent amount of alcohol. Because the adduct between the phenol and amino‐functional silane coupling agent can be easily regenerated during the manufacturing process, it is thought that the pretreatment method of APTS on phenol helps APTS disperse well within EMC. Actually, the glass‐transition temperature and flexural strength of EMC by the application of the pretreatment method on phenol are higher than those by the integral addition method and the pretreatment on epoxy. However, they become lower as the degree of reaction of silane with phenol increases. The pretreatment of the amino‐functional silane coupling agent on phenol shows lots of advantages over the previous methods. From the viewpoint of the process, the homogeneous dispersion of the coupling agent can be obtained with consistency, and the possibility of white gel formation can also be completely removed by it. From the perspective of properties, through a controlled pretreatment on phenol resin, better mechanical properties of EMC can be obtained than those through the pretreatment on epoxy. In addition, the pretreatment process on phenol is simple and feasible for mass production. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2171–2179, 2006     

Toughened epoxy resin matrix for a membrane shell by wet filament winding

A toughened epoxy resin matrix was obtained with a reactive toughening agent and methyl hexahydrophthalic anhydride as a curing agent. The mechanical properties of the modified epoxy resin and its glass‐fiber‐reinforced composites were investigated systematically. The modified epoxy resin matrix possessed many good properties, including a high flexural strength (138 MPa), high elongation at break (5.2%), low viscosity, long pot life at room temperature, and good water resistance. In addition, the glass‐fiber‐reinforced composites showed a high strength conversion ratio of the glass fiber (86.7%) and good fatigue resistance. The results demonstrated that the modified epoxy resin matrix is very suitable for applications in reverse osmosis membrane shell products fabricated with wet filament winding for water treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of various polyurethanes on the mechanical and structural properties of an epoxy resin

Polyurethanes (PURs) obtained from poly(ethylene glycol)s (PEGs) and polyoxypropylene diols (POPDs) of different molecular weights were used as modifiers of diglycidyl ether of bisphenol A. The impact strength, critical stress intensity factor, stress, and strain during three‐point bending were measured as functions of the PUR type and content. Scanning electron microscopy and infrared spectroscopy were employed for the structure and morphology analysis. The addition of 10 or 15% PUR to the epoxy resin resulted in the most enhanced mechanical properties. However, a modifier loading higher than 15% led to decreases in the impact strength, critical stress intensity factor, and flexural strength. Moreover, shorter flexible segments in PUR obtained from lower molecular weight PEG led to stronger composites, whereas composites containing PUR based on lower molecular weight POPD with long flexible segments exhibited higher toughness and strain at break and lower impact strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermomechanical and electroactive behavior of a thermosetting styrene‐based carbon black shape‐memory composite

A thermosetting styrene‐based shape memory polymer (SMP) filled with nanoscale (30 nm) carbon black are prepared to reinforce the thermomechanical performances and realize the high‐efficient electronic actuation at macro scale due to the carbon–carbon network morphology at nano/micro scale. The elastic modulus of this thermosetting SMP composite is significant strengthened and can maintain at 1–2.5 GPa at around the room temperature, which is suitable for used as a structural material. The electronic resistivity decreases sharply at a quite low percolation threshold range (2–5%), and maintains at a relatively low and stable level of electronic resistivity. Furthermore, the electronic resistivity also exhibits relative stability in terms of the resistivity–temperature–time relationship and the evolution of resistivity upon heating–cooling cycles. This shape memory styrene‐based composite is suitable to be used as an electroactive functional material in realistic engineering. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45978.     

Nano‐carbon black filled Lyocell fiber as a precursor for carbon fiber

In this work, Lyocell fibers filled with various amounts of carbon black were prepared. Wide angle X‐ray diffraction (WAXD) results showed that carbon black filled Lyocell fibers still had a cellulose II crystal structure and kept the characteristic peak of carbon black at the same time. The results of mechanical properties showed a slight reduction in the carbon black filled Lyocell fiber. Moreover, the heat stabilities of the carbon black filled Lyocell fibers showed no obvious change. The residue of carbon black filled Lyocell fiber at 1000°C was higher than that of Lyocell fiber, implying higher carbon yield could be obtained for the carbon black filled Lyocell precursor. Scanning electron microscopy (SEM) experiments showed that the surface and the cross section of carbon black filled Lyocell fiber were smooth and round, which are consistent with the carbon fiber precursor. The WAXD pattern of carbon black filled Lyocell‐based carbon fiber was different from that of Lyocell‐based carbon fiber. The addition of carbon black transfers the diffraction peak of carbon fiber while keeping the characteristic structure of carbon black. The results of mechanical properties of carbon fibers show that, if an appropriate amount of carbon black was chosen, carbon fiber with better properties than Lyocell‐based carbon fiber could be obtained by using the carbon black filled Lyocell fibers as the precursor. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 65–74, 2006     

Transfer function and working principle of a pressure/temperature sensor based on carbon black/silicone rubber composites

Pressure/temperature sensitive silicon rubber (SR) filled with carbon black (CB) was prepared by a liquid mixing method. The transfer function of a pressure/temperature sensor based on CB/SR was derived by general effective media theory. The results show that the transfer functions coincided well with the experimental data, and the negative pressure coefficient of the resistance/positive temperature coefficient of resistance are shown. The working principles of these two kinds of sensors are different. The working principle of the pressure sensor based on CB/SR was related to the volume fraction of CB. With increasing volume fraction of CB, the working principle of this kind of pressure sensor varied from a piezo‐resistive effect to a strain effect. In addition, the working principle of the temperature sensor based on CB/SR was that the resistivity changed with temperature; this was not related to the volume fraction of CB. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42979.     

Preparation and characterization of the modulus intermediate layer in carbon fiber/epoxy composites by depositing sepiolites

An important aspect in development of multi‐scale reinforced composites is their mass production which can be easily realized. In this article, the sepiolites (Si12O30Mg8(OH)4(OH2)4·8H2O) are directly deposited onto the surface of JH‐T800 carbon fibers for the first time with no need for removal of the commercial sizing agent. The sepiolites adhering to the carbon fibers are uniformly distributed with random orientation, and participated in the formation of high modulus intermediate layer encompassing the carbon fiber. After the deposition of sepiolites, the interfacial shear strengths (IFSS) of the carbon fiber/epoxy composites are significantly improved as shown in single‐fiber composite fragmentation tests. Compared to the commercial carbon fiber composites, the sepiolite‐deposited fiber composites also exhibit obvious improvement in the interlaminar shear strength and flexural strength. As a new kind of multi‐scale reinforcement with industrial application value, the sepiolite‐deposited carbon fibers can further raise the level of mechanical properties of the existing carbon fiber reinforced composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43955.     

The compressive property of a fiber-reinforced resin beetle elytron plate and its influence mechanism

To develop composite material beetle elytron plates (BEPs), short basalt fiber-reinforced epoxy resin BEPs with hollow trabeculae and honeycomb walls were fabricated exploratively. Through comparison with honeycomb plates (HPs) with the same wall thickness, the basic mechanical performance, failure mode and influence mechanism were studied via out-of-plane compression tests. The results show that compared with HPs, the specific strength and energy consumption per volume of BEPs can be at least 18% and 112% higher, respectively; however, the increase is less than half that of BEPs made of ductile materials. The former is due to the synergistic mechanism of the trabecular-honeycomb structure in the BEP core layer, which endows the composite BEPs with better ductility than HPs, while the latter is caused by the prominent brittleness of the composite material used in this study. Additionally, the height-to-thickness ratio of the plate honeycomb wall in this article is not large enough. Thus, the core has great rigidity and fails to buckle in experiments; instead, shear failure of the core material occurs. This study reveals for the first time the mechanical compression properties and failure mechanism of brittle material BEPs and shows a direction for developing BEPs in similar material types.     

Impact of titanium and silica/titanium fumed oxide nanofillers on the elastic properties and thermal decomposition of a polyester resin

The impact of nanoparticles of titanium (rutile) and silica–titanium fumed oxide (STO) on both the acoustic properties and thermal decomposition of a styrene‐crosslinked unsaturated polyester resin were studied with the methods of ultrasonic probing and thermal decomposition mass spectrometry at filler loadings ranging from 0.5 to 5.0%. It was shown that the elastic modulus, Poisson's ratio, and thermal resistivity in the titanium‐filled nanocomposites increased at small loadings of about 0.5%, whereas in the STO‐filled nanoparticles, the decreases in the parameters at loadings of up to 1.5% was replaced by some increases at higher loadings of up to 5.0%. Distinctions in the concentration dependences of the elastic parameters and the thermal decomposition intensity for both fillers could be explained by the features of the polymer–particle interactions because of the differences in both the number of active sites located on the particle's surface and the polymer structure within interface regions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42010.     

Damage analysis of composites reinforced with Alfa fibers: Viscoelastic behavior and debonding at the fiber/matrix interface

In this article, we first review state‐of‐the‐art experimental techniques and measurements to characterize the mechanical properties of anisotropic vegetal alfa fibers, epoxy‐resin, and the behavior of the interphase between the matrix and alfa fibers. Second, we conduct experimental tests to determine the mechanical properties of fibers, resin, and the interphase. Third, we carry out a series of finite element simulations to predict damage initiation and to estimate crack propagation in alfa‐fiber/epoxy‐resin (AFER) composites. Different tests to determine the longitudinal Young's modulus of alfa fibers and epoxy resin as well as nanoindentation tests to obtain the transverse stiffness of the fibers are presented. Experimental results from the characterization are introduced in a micromechanical model to estimate, using the concept of the energy release rate (ERR), the matrix crack, and its interaction with interfacial debonding. The wettability problems in the preparation of vegetable composites and their effect on fiber‐matrix interfacial debonding are also addressed. The analysis of the damage behavior of AFER composites demonstrates that under load transverse to the fiber axis, a crack initiated in the matrix is propagated perpendicular to the direction of the load. Near the interface, the ERR decreases and this energy is higher in the presence of interfacial debonding areas generated by problems of fiber wettability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43760.