Shrinkage and mechanical properties of unsaturated polyester reinforced with clay and core–shell rubber

Glassy unsaturated polyester (UP) resin was reinforced using an organically modified montmorillonite (OMMT) and toughened with core?Cshell rubber (CSR) particles. The nanostructure, morphology, and deformation mechanism of composite specimens were studied by small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and reflected optical microscopy (ROM). An intercalated nanostructure with partial exfoliation was observed in the UP reinforced by various amounts of OMMT. Locally clustered but globally good CSR particle dispersion in the UP matrix was evident in UP toughened with 5 and 10 wt% CSR particles. Simultaneous presence of OMMT and CSR particles in UP/OMMT/CSR hybrid composites was found to cause partial phase separation with bigger rubber particle agglomerates and lower clay-intergallery height increase. The effects of OMMT and CSR contents on volume shrinkage, impact fracture energy, fracture toughness, and compressive yield strength of UP were investigated. The introduction of OMMT of up to 3?wt% into the UP matrix lowered volume shrinkage to some extent, while further addition increased the shrinkage slightly. In the hybrid nanocomposites, the volume shrinkage decreased to a minimum level of 5.2?% with increases in OMMT level. The impact fracture energy of UP improved with increasing the OMMT level of up to 3?wt%, whereas its further addition decreased the impact fracture energy slightly due to the clay particle agglomeration. The hybrid composites with OMMT level below 3?wt% showed higher impact fracture energy compared to the reinforced UP specimens with the same OMMT levels. Interestingly, a synergism in the fracture toughness (K _IC) was observed in the hybrid composite containing 1?wt% OMMT and 10?wt% CSR particles. The presence of OMMT as reinforcement in the hybrid composites could compensate the lowering of the compressive yield strength caused by low-modulus CSR particles. The clay?Crubber particle interaction in the hybrid systems seems to increase the threshold of shear deformation of the UP matrix to some extent.     

Toughened nylon66/nylon6 ternary nanocomposites by elastomers

The elastomer toughening of PA66/PA6 nanocomposites prepared from the organic modified montmorillonite (OMMT) was examined as a means of balancing stiffness/strength versus toughness/ductility. Several different formulations varying in OMMT content were made by mixing of PA6 and OMMT as a master‐batch and then blending it with PA66 and different elastomers in a twin screw extruder. In this sequence, the OMMT layers were well exfoliated in the nylon alloy matrix. The introduction of silicate layers with PA6 induced the appearance of the γ crystal phase in the nanocomposites, which is unstable and seldom appears in PA66 at room temperature and it further affected the morphology and dispersion of rubber phase resulting in much smaller rubber particles. The incorporation of POE‐g‐MA particles toughened the nanocomposites markedly, but the tensile modulus and strength were both reduced. Conversely, the use of OMMT increased the modulus but decreased the fracture toughness. The nanocomposites exhibited balanced stiffness and toughness. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of cloisite 30B clay and sisal fiber on dynamic mechanical and fracture behavior of unsaturated polyester toughened epoxy network

This study examined the dynamic mechanical properties of sisal fiber reinforced unsaturated polyester (UP) toughened epoxy nanocomposites. The chemical structures changes in Epoxy, UP and UP toughened epoxy (Epoxy/UP) systems were characterized by Proton Nuclear magnetic resonance (¹HNMR) spectroscopy. The morphological alterations of the nanocomposites were analyzed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The untreated, chemically treated fibers, nanoclays, and the fiber reinforced Epoxy/UP nanocomposites were confirmed by FTIR spectrometer. The obtained mechanical results showed that alkali‐silane treated fibers improve the tensile strength (96%) and flexural strength (60%) of the Epoxy/UP nanocomposite than that of Epoxy/UP blend due to the strong interfacial bonding between the sisal fiber and matrix. The fracture toughness (K_IC) and fracture energy (G_IC) of treated sisal fiber reinforced DGEBA/UP/C30B nanocomposites found to be higher than that of untreated sisal fiber nanocomposites. The dynamic mechanical analysis (DMA) reveals that the fiber reinforced Epoxy/UP nanocomposites contains 30 wt% treated fiber and 1 wt% nanoclays, exhibits the highest storage modulus and better glass transition temperature (T_g) among the other kind of systems. The surface morphology of the fibers, fractured surface of the resins and composites were confirmed by scanning electron microscope (SEM). POLYM. COMPOS., 37:2832–2846, 2016. © 2015 Society of Plastics Engineers     

Fracture behavior of thermoplastic polyolefin/clay nanocomposites

A thermoplastic polyolefin (TPO) containing 70 wt % styrene–ethylene–butadiene‐styrene‐g‐maleic anhydride and 30 wt % polypropylene and its nanocomposites reinforced with 0.3–1.5 wt % organoclay were prepared by melt mixing followed by injection molding. The mechanical and fracture behaviors of the TPO/clay nanocomposites were investigated. The essential work of fracture (EWF) approach was used to evaluate the tensile fracture behavior of the nanocomposites toughened with elastomer. Tensile tests showed that the stiffness and tensile strength of TPO was enhanced by the addition of low loading levels of organically modified montmorillonite. EWF measurements revealed that the fracture toughness of the TPO/clay nanocomposites increased with increasing clay content. The organoclay toughened the TPO matrix of the nanocomposites effectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(ester‐amine) hyperbranched polymer as toughening and co‐curing agent for epoxy/clay nanocomposites

The marriage between hardness and flexibility of epoxy resins (improved toughness) is a desired feature, which broads their application in various industrial fields, especially for high impact resistance purposes. Accordingly, this work aims to improve toughness properties of epoxy resin (Epon‐828)/Ancamine (curing agent) system using amino‐terminated hyperbranched poly(ester‐amine) [Poly(PEODA‐NPA)] (HP) as toughening and/or co‐curing agent, in presence of organo‐modified Montmorillonite clay (OMMT) as a reinforcing filler. HP was synthesized via Michael addition reaction of poly(ethylene glycol) diacrylate (PEODA) to N‐methyl‐1,3‐propanediamine (NPA). Chemical structure and molecular weight of HP were elucidated using infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) techniques, respectively. Epoxy/OMMT nanocomposites toughened with HP (at different concentrations) showed remarkable improvement in their toughness without any adverse effect on the other physico‐mechanical properties. The optimum concentration of HP and OMMT was found to be 20 wt % and 1–3 wt% of the epoxy resin, respectively. The extent of exfoliation and dispersion of OMMT platelets within the epoxy cured films was assessed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. In addition, thermal gravimetric analyses (TGA‐DTA) of epoxy/OMMT nanocomposites toughened with HP showed a slight increase in their decomposition temperature, particularly at low OMMT loading. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Toughening of unsaturated polyester resins with core–shell rubbers

The effects of core–shell rubbers (CSRs) as tougheners on the fracture properties of unsaturated polyester (UP) resins during curing at 110°C are investigated. CSRs were synthesized by two‐stage soapless emulsion polymerizations; the soft core was made from rubbery poly(n‐butyl acrylate), whereas the hard shell was made from methyl methacrylate, ethylene glycol dimethacrylate, and various concentrations of glycidyl methacrylate. Depending on the content of glycidyl methacrylate in the CSR shell and the amount of CSR added to the UP, the fracture properties of the CSR‐toughened UP resins varied. The experimental results are explained by an integrated approach of measurements of the static phase characteristics of a styrene/UP/CSR system, the reaction kinetics, the cured sample morphology, the glass‐transition temperatures, and the fracture toughness with differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, and dynamic mechanical analysis. Finally, the toughening mechanism for the CSR‐toughened UP resins is also explored. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of mixing protocols on impact modified poly(lactic acid) layered silicate nanocomposites

Poly(lactic acid)/2 wt % organomodified montmorillonite (PLA/OMMT) was toughened by an ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) rubber. The ternary nanocomposites were prepared by melt compounding in a twin screw extruder using four different addition protocols of the components of the nanocomposite and varying the rubber content in the range of 5–20 wt %. It was found that both clay dispersion and morphology were influenced by the blending method as detected by X‐ray diffraction (XRD) and observed by TEM and scanning electron microscopy (SEM). The XRD results, which were also confirmed by TEM observations, demonstrated that the OMMT dispersed better in PLA than in E‐MA‐GMA. All formulations exhibited intercalated/partially exfoliated structure with the best clay dispersion achieved when the clay was first mixed with PLA before the rubber was added. According to SEM, the blends were immiscible and exhibited fine dispersion of the rubber in the PLA with differences in the mean particle sizes that depended on the addition order. Balanced stiffness‐toughness was observed at 10 wt % rubber content in the compounds without significant sacrifice of the strength. High impact toughness was attained when PLA was first mixed with the clay before the rubber was added, and the highest tensile toughness was obtained when PLA was first compounded with the rubber, and then clay was incorporated into the mixture. Thermal characterization by DSC confirmed the immiscibility of the blends, but in general, the thermal parameters and the degree of crystallinity of the PLA were not affected by the preparation procedure. Both the clay and the rubber decreased the crystallization temperature of the PLA by acting as nucleating agents. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41518.     

Mechanical properties and fracture behavior of high-performance epoxy nanocomposites modified with block polymer and core–shell rubber particles

The mechanical properties, thermomechanical properties, and fracture mechanic properties of block-copolymer (BCP), core–shell rubber (CSR) particles, and their hybrids in bulk epoxy/anhydride system were investigated at 23 °C. The results show that fracture toughness was increased by more than 268% for 10 wt % BCP, 200% for 12 wt % of CSR particles, and 100% for hybrid systems containing 3 wt % of each, BCP and CSR. The volume content of nanoparticles influences the final morphology and thus influences the tensile properties and fracture toughness of the modified systems. The toughening mechanisms induced by the BCP and CSR particles were identified as (1) localized plastic shear-band yielding around the particles and (2) cavitation of the particles followed by plastic void growth in the epoxy polymer. These mechanisms were modeled using the Hsieh et al. approach and the values of G_Ic of the different modified systems were calculated. Excellent agreement was found between the predicted and the experimentally measured fracture energies. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48471.     

PPR/OMMT纳米复合材料的EWF参数与力学性能

以马来酸酐接枝无规共聚聚丙烯(PPR-g-MAH)为相容剂,采用熔融插层法制备了无规共聚聚丙烯(PPR)/有机蒙脱土(OMMT)纳米复合材料,通过对PPR/OMMT纳米复合材料的基本断裂功(EWF)的表征,并结合它们的拉伸性能和冲击强度的测试分析,探讨了PPR/OMMT纳米复合材料的断裂机理和塑性变形机理,以及OMMT用量对PPR断裂强度和拉伸强度的影响;SEM观察揭示了OMMT在PPR基体中的分散性程度随含量的增加变差。结果表明:在PPR-g-MAH的作用下OMMT能有效提高PPR/OMMT的拉伸强度,OMMT质量分数低于4%时,PPR/OMMT纳米复合材料的冲击强度(Gc)、比基本断裂功(we)和塑性变形能力均得到提高。PPR/OMMT纳米复合材料的we和Gc具有相似的变化趋势,且Gc总是大于we。     

Unsaturated polyester‐toughened epoxy composites: Effect of sisal fiber on thermal and dynamic mechanical properties

In the present study, the mechanical and thermal properties of sisal fiber‐reinforced unsaturated polyester (UP)‐toughened epoxy composites were investigated. The sisal fibers were chemically treated with alkali (NaOH) and silane solutions in order to improve the interfacial interaction between fibers and matrix. The chemical composition of resins and fibers was identified by using Fourier‐transform infrared spectroscopy. The UP‐toughened epoxy blends were obtained by mixing UP (5, 10, and 15 wt%) into the epoxy resin. The fiber‐reinforced composites were prepared by incorporating sisal fibers (10, 20, and 30 wt%) within the optimized UP‐toughened epoxy blend. Scanning electron microscopy was used to analyze the morphological changes of the fibers and the adhesion between the fibers and the UP‐toughened epoxy system. The results showed that the tensile and flexural strength of (alkali‐silane)‐treated fiber (30 wt%) ‐reinforced composites increased by 83% and 55%, respectively, as compared with that of UP‐toughened epoxy blend. Moreover, thermogravimetric analysis revealed that the (alkali‐silane)‐treated fiber and its composite exhibited higher thermal stability than the untreated and alkali‐treated fiber systems. An increase in storage modulus and glass transition temperature was observed for the UP‐toughened epoxy matrix on reinforcement with treated fibers. The water uptake behavior of both alkali and alkali‐silane‐treated fiber‐reinforced composites is found to be less as compared with the untreated fiber‐reinforced composite. J. VINYL ADDIT. TECHNOL., 23:188–199, 2017. © 2015 Society of Plastics Engineers     

Essential work of fracture (EWF) analysis for short glass fiber reinforced and rubber toughened nylon‐6

The effect of fiber content on the fracture toughness of short glass fiber reinforced and rubber toughened nylon‐6 has been investigated using the essential work of fracture (EWF) analysis under both quasi‐static and impact rates of loading. Under quasi‐static loading rate, matrix plastic deformation played a major role. Addition of 10 wt% of short glass fibers into a rubber toughened nylon‐6 matrix improved the fracture toughness substantially. This is due to the synergistic effect that comes from matrix yielding and fiber related energy absorption such as fiber debonding, fiber pull‐out and fiber fracture. With further increasing the glass fiber content, up to 20 and 30 wt%, even though plastic deformation could still take place on the fracture surfaces, the depth of the fracture process zones was much smaller when compared with the system with 10 wt% of glass fibers. The reduction in fracture process zone caused the reduction in fracture toughness. Under impact loading rate, the unreinforced blend still fractured in a ductile manner with gross yielding in the inner fracture process zone and the outer plastic zone. The unrein‐forced blend therefore possesseed higher fracture toughness. For the fiber reinforced blends, the matrix fractured in brittle manner and so fracture toughness of the reinforced blends decreased dramatically. The impact fracture toughness increased slightly after incorporation of a higher weight percentage of glass fibers.     

球磨法制备POE-g-MAH/OMMT增韧母粒及其对PA6增韧改性

通过球磨法制备马来酸酐接枝(乙烯-辛烯)共聚物(POE-g-MAH)／有机化蒙脱土(OMMT)增韧母粒,并将其用于尼龙(PA)6的增韧改性.结果表明,球磨法制备的POE-g-MAH/OMMT增韧母粒尺寸比较均匀,有少量POE-g-MAH进入OM MT片层之间,导致OMMT片层间距有所增加.POE-g-MAH/OMMT增...     

New toughened polypropylene/organophilic montmorillonite nanocomposites

A new toughened polypropylene (PP)/organophilic montmorillonite (OMMT) nanocomposite was obtained by melt intercalation extrusion in a twin‐screw extruder without any compatibilizer. The nanocomposites were characterized by transmission electron microscopy (TEM) observation, melt flow rate (MFR) testing, mechanical properties measurement, melting and crystallization behaviors, and thermal stability determination. TEM images revealed the existence of intercalated OMMT layers dispersed throughout the PP matrix. A clear reduction in MFR was observed as the OMMT content increased. The yield strength, elongation at yield, and initial modulus of the PP/OMMT nanocomposites increased slightly as the result of the reinforcement of the OMMT nanofiller. The ultimate value of notched impact strength of the nanocomposites was over twofold that of neat PP after incorporation with 4 wt % OMMT; meanwhile, the heat deflection temperature values showed that the thermal stability increased a little. This is a new approach for preparation for the production of a toughened PP material with a high thermal stability and rigidity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Solid‐state mechanical properties of polypropylene/nylon 6/clay nanocomposites

The mechanical and thermomechanical properties as well as microstructures of polypropylene/nylon 6/clay nanocomposites prepared by varying the loading of PP‐MA compatibilizer and organoclay (OMMT) were investigated. The compatibilizer PP‐MA was used to improve the adhesion between the phases of polymers and the dispersion of OMMT in polymer matrix. Improvement of interfacial adhesion between the PP and PA6 phases occurred after the addition of PP‐MA as confirmed by SEM micrographs. Moreover, as shown by the DSC thermograms and XRD results, the degree of crystallinity of PA6 decreased in the presence of PP‐MA. The presence of OMMT increased the tensile modulus as a function of OMMT loading due to the good dispersion of OMMT in the matrix. The insertion of polymer chains between clay platelets was verified by both XRD and TEM techniques. The viscosity of the nanocomposites decreased as PP‐MA loading increased due to the change in sizes of PA6 dispersed phase, and the viscosity increased as OMMT loading increased due to the interaction between the clay platelets and polymer chains. The clay platelets were located at the interface between PP and PA6 as confirmed by both SEM and TEM. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of nanocomposite by adding of Tunisian nanoclay in unsaturated polyester matrix: mechanical and thermal study

Unsaturated Polyester (UP) resin is widely used for many applications such as reinforced plastic (FRP) and polymer composites. However, these materials suffer from their low mechanical and thermal properties. For enhancing their performance, researchers have used Tunisian montmorillonite (MMT) for manufacturing of unsaturated polyester-montmorillonite (UP-MMT) nanocomposite synthesized by dispersing the UP resin into the silicate layers of MMT. The MMT has been modified ammonium quaternary as organic cation (OMMT). Test results, supported by mechanical testing, X-ray diffraction, thermal analysis (DSC and TGA) and transmission electron microscopy, indicated that the mechanical properties and the thermal stability of unsaturated polyester with OMMT nanocomposite (UP/OMMT) are better than those of pure UP. The degradation temperature increased by 78 °C with the addition of organic modification, and SEM micrographs show good dispersion of modified montmorillonite in the polymer matrix. Tensile strength is increased by 81 % for the UP/OMMT nanocomposite.     

Studies on thermal degradation and flame retardant behavior of the sisal fiber reinforced unsaturated polyester toughened epoxy nanocomposites

Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant, and morphological behavior of the UP toughened epoxy (Epoxy/UP) were systematically studied. The chemical structures of Epoxy, UP, and Epoxy/UP systems were characterized using Proton Nuclear magnetic resonance (¹HNMR) and Fourier transform infrared (FTIR) spectra. The homogeneous dispersion of nanoclay within the polymer matrix was analyzed using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) analysis. Incorporation of sisal fibers and C30B nanoclays within Epoxy/UP system resulted in an increase in the mechanical, thermal, and flame retardance properties. Thermogravimetric analysis (TGA) has been employed to evaluate the thermal degradation kinetic parameters of the composites using Kissinger and Flynn‐Wall‐Ozawa methods. Cone calorimeter, UL‐94, and LOI tests revealed a reduction in the burning rate of the matrix with the addition of fibers and nanoclays. The results showed that the treated fiber reinforced nanocomposites had higher thermal stability and better flame retardant properties than the treated fiber reinforced composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42068.     

Preparation of binary and hybrid epoxy nanocomposites containing graphene oxide and rubber nanoparticles: Fracture toughness and mechanical properties

Binary and hybrid epoxy nanocomposites modified with graphene oxide (GO) and core–shell rubbers (CSR) were synthesized via the solvent-exchange method. X-ray diffraction analysis and scanning electron microscopy of the samples showed a homogeneous dispersion of GO and CSR in the epoxy matrix. The tensile modulus and tensile strength of the samples modified with CSR decreased continuously with increasing CSR content; however, with the addition of only 0.05 phr GO to the neat epoxy and rubber-modified epoxy, these properties significantly increased. The use of GO and CSR individually improved the fracture toughness, but the impact of GO was greater. The simultaneous use of GO and CSR improved both the fracture toughness and the mechanical properties. Our investigation of the toughening mechanism indicated that crack deflection–bifurcation, crack pinning, and particle debonding–pullout in the presence of GO nanosheets and limited rubber particle cavitation contributed to fracture toughness improvement in the hybrid systems. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46988.     

Rubber toughening of nylon 6 nanocomposites

The rubber toughening of nylon 6 nanocomposites prepared from an organoclay was examined as a means of balancing stiffness/strength versus toughness/ductility. Nine different formulations varying in montmorillonite, or MMT, and maleated ethylene/propylene rubber or EPR-g-MA rubber content were made by mixing of nylon 6 and organoclay in a twin screw extruder and then blending the nanocomposites with the rubber in a single screw extruder. In this sequence, the MMT platelets were efficiently dispersed in the nylon 6 matrix. The MMT platelets did not penetrate into the rubber phase. The addition of clay affected the dispersion of the rubber phase resulting in larger and more elongated rubber particles. The tensile properties and impact strength of these toughened nanocomposites are discussed in terms of the MMT and rubber contents and morphology. There is a clear trade-off between stiffness/strength versus toughness/ductility.     

Surface modification effects of core–shell rubber particles on the toughening of poly(butylene terephthalate)

We toughened poly(butylene terephthalate) (PBT) by loading core–shell rubber (CSR) type impact modifiers, consisting of a rubbery poly(n‐butyl acrylate) core and a rigid poly(methyl methacrylate) shell. To optimize the dispersion of CSR particles into the PBT matrix during melt compounding, the shell surface was modified with different grafting ratios of glycidyl methacrylate (GMA) reactive with PBT chain ends. In PBT blends with a 20 wt % CSR loading, the dispersed rubbery phases showed discernible shapes depending on the grafted GMA content, from predetermined spheres with 0.25 ± 0.05 μm diameters to their aggregates in the 2–3 μm diameter range. As a result, the interparticle spacing (τ) could be controlled from 0.25 to 4.0 μm in the PBT blends containing the fixed rubber loading. The Izod impact strengths of these samples increased significantly below τ = 0.4 μm. Additional thermal and morphological analyses strongly supported the hypothesis that the marked increase in toughness of the blends was related to less ordered lamellar formation of the PBT matrix under the confined geometry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhanced toughness of zirconia ceramics with graphene platelets consolidated by spark plasma sintering

Graphene platelets reinforced zirconia (GPLs/ZrO₂) composites were prepared by spark plasma sintering in the present work. The effects of GPLs content on the densification route, microstructure feather, mechanical properties, and aging behaviors of such composites were investigated. In spite of the impeding effect of GPLs, high relative density of 98% was achieved for the composites owing to the uniform dispersion of GPLs. The addition of GPLs contributed to enhanced fracture toughness of the composites; when the added content was 1.0 wt.%, its fracture toughness reached up to 8.6 MPa·m^1/2. Also, aging behavior of the GPLs/ZrO₂ composites was investigated at 134°C for 24 hours. The monolithic ZrO₂ ceramic and GPLs/ZrO₂ composites presented residual ratio of 55% and 72% in fracture toughness, respectively. Thus, the incorporation of GPLs inhibited phase transformation from tetragonal phase to monoclinic phase of zirconia.