Study on Steady Shear,Morphology and Mechanical Behavior of Nanocomposites based on Polyamide 6

Nanocomposites of two different grades of polyamide 6 (PA6) with organically modified nanoclay were prepared via melt compounding in a twin‐screw extruder. The rheological behavior, morphology and mechanical properties of the nanocomposites were studied using a capillary rheometer, x‐ray diffraction (XRD), tapping‐mode atomic force microscopy (AFM), and tensile and flexural tests. XRD patterns indicate that the organically modified layered silicate was well dispersed in the PA6 matrix. From the AFM images the surface roughness of PA6 slightly increases with addition of organoclay. The rheological studies showed that the prepared nanocomposites have shear thinning behavior, obeying the power law equation. Addition of organoclay increases the shear stress and shear viscosity. At high rate of shear deformation the viscosity of nanocomposites are comparable to those of the pure polyamides. The activation energy of flow decreases with increasing nanoclay content. For most of the prepared nanocomposites the activation energy values increase with increasing shear rate. The tensile strength and flexural modulus and strength of the nanocomposites increase with increase of nanoclay content, but the extension at yield decreases with increasing clay loading.     

Nonisothermal Crystallization Kinetics of Nylon 66/Montmorillonite Nanocomposites

Polyamide 66(PA66)/montmorillonite nanocomposites were prepared via direct melt compounding. The nonisothermal crystallization of PA66 and PA66/MMT nanocomposites were investigated by differential scanning calorimetry. The results show that MMT platelets play a competing role in the crystallization process of nylon 66. On the one hand, they can act as a nucleator for the PA66 matrix, accelerating the crystallization rate; on the other hand, they retard the crystal/spherulite growth, especially for nanocomposites with higher MMT content. The analysis results using Jeziorny and Mo equations verify the dual actions of the nucleation and the obstruction of crystallization of MMT in the PA66 matrix. Kissinger's method was used to obtain the activation energy of the crystallization process; the results confirm that the incorporation of MMT causes the above actions.     

Effects of Blend Ratio on Rheology,Morphology, Mechanical and Oil-Resistant Properties in Chlorinated Polyethylene Rubber and Copolyamide Blends

The elastomeric chlorinated polyethylene (CPE) blended with a low melting point copolyamide (PA6/PA66/PA1010, PA) was prepared by a melt mixing technique. The mixing characteristics of the blends were analyzed from the rheographs. The influence of copolyamide (PA) content on the morphology, mechanical properties, crystallization and oil-resistance, and the addition of compatibilizers on the mechanical properties were also systematically investigated. Morphological examinations clearly revealed a two-phase system in which CPE/PA blends exhibit a cocontinuous morphology for 50/50 composition, and the continuous phase of PA turns into a disperse phase for 70/30, 80/20, and 90/10. There is a distinct interface between the two phases. The mechanical properties, crystallization, and oil-resistance have a strong dependence on the amount of PA. The blends with higher proportions of PA have superior mechanical properties; they are explained on the basis of the morphology of the blend and the cystallinity of PA. In addition, compatibilizers, including chlorinated polyethylene-graft-copolyamide (CPE-G-PA), chlorinated polyethylene-graft-maleic anhydride (CPE-G-MAH), ethylene-n-butyl acrylate-monoxide (EnBACO), and ethylene-n-butyl acrylate-monoxide-graft-maleic anhydride (EnBACO-g-MAH) were added into the blends. Tensile strength and elongation at break go through a maximum value at a compatibilizer resin content (on the basis of the total mass of the blend) of 20 wt% while the PA content is 30 wt%.     

Influences of Carbon Nanotube Networking on the Conductive,Crystallization, and Thermal Expansion Behaviors of PA610-Based Nanocomposites

The electrical, crystallization and thermal expansion behaviors of polyamide 610 (PA610)/multi-walled carbon nanotube (CNT) nanocomposites prepared by melt mixing were investigated. Electron microscopy (Scanning Electron Microscopy and Transmission Electron Microscopy) revealed that a good dispersion of CNT and CNT network was obtained in the PA610 matrix. Addition of CNT to PA610 matrix led to polymer nanocomposites exhibiting higher electrical conductivity and lower thermal expansion. The network of CNT in the PA610 matrix, which can be tuned by the loading of CNT and the melt isothermal treatment, was found to play an important role in reducing thermal expansion and achieving higher conductivity. Furthermore, it was shown that significant reduction in thermal expansion in PA610/CNT nanocomposites was due to both thermally insensitive CNT and formation of CNT network.     

The interface structure of nano-SiO2/PA66 composites and its influence on material's mechanical and thermal properties

The PA66-based nanocomposites containing surface-modified nano-SiO₂ were prepared by melt compounding. The interface structure formed in composite system was investigated by thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The influence of interface structure on material's mechanical and thermal properties was also studied. The results indicated that the PA66 chains were attached to the surface of modified-silica nanoparticles by chemical bonding and physical absorption mode, accompanying the formation of the composites network structure. With the addition of modified silica, the strength and stiffness of composites were all reinforced: the observed increase depended on the formation of the interface structure based on hydrogen bonding and covalent bonding. Furthermore, the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed that the presence of modified silica could affect the crystallization behavior of the PA66 matrix and lead to glass transition temperature of composites a shift to higher temperature.     

Polyamide 6/modified Carbon Black Nanocomposites Prepared via In Situ Polymerization

Polyamide 6/modified carbon black (PA6/MCB) composites were prepared via in-situ ring opening polymerization of caprolactam in the presence of dispersed carboxyl group modified carbon black (MCB). The dispersion of MCB in the PA6 matrix, nonisothermal crystallization and melting behaviors, and volume resistivity of the composites were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and a resistivity meter, respectively. The results indicated that MCB dispersed well in the PA6 matrix. When the MCB content was 5 wt%, the MCB particles were of a nanoscale. The conductivity percolation threshold of the PA6/MCB composites was 8 wt% due to the good dispersion of MCB in the PA6 matrix. The addition of MCB elevated the cold crystallization temperature of PA6, reflecting the effectiveness of MCB as nucleating agents. However, the MCB decreased the crystallization enthalpy of PA6 during both heating and cooling processes.     

Studies on the Blends of Polyamide66 and Thermoplastic Polyimide

The influence of the content of thermoplastic polyimide (TPI) on the structure and properties of polyamide66 (PA66)/TPI blends was studied. The results indicated that the addition of TPI showed little influence on the mechanical properties of the PA66/TPI blends, and the melting and crystallization behavior of the TPI/PA66 blends was not changed obviously. However, the addition of a small quantity of TPI significantly improved the heat resistance, and lowered the friction coefficient and the wear rate of the blends in comparison with pure PA66.     

Preparation and Characterization of Linear Low Density Polyethylene/Carbon Nanotube Nanocomposites

Linear low‐density polyethylene (LLDPE)/multiwalled carbon nanotube (MWNT) nanocomposites were prepared via melt blending. The morphology and degree of dispersion of nanotubes in the polyethylene matrix were investigated using scanning electron microscopy (SEM). Both individual and agglomerates of MWNTs were evident. The rheological behavior and mechanical and electrical properties of the nanocomposites were studied using a capillary rheometer, tensile tester, and Tera ohm‐meter, respectively. Both polyethylene and its nanocomposites showed non‐Newtonian behavior in almost the whole range of shear rate. Addition of carbon nanotubes increased shear stress and shear viscosity. It was also found that the materials experience a fluid‐solid transition below 1 wt% MWNT. Flow activation energy for the nanocomposites was calculated using an Arrhenius type equation. With increasing nanotube content, the activation energy of flow increases. A decrease of about 7 orders of magnitude was obtained in surface and volume resistivity upon addition of 5 wt% MWNT. In addition, a difference between electrical and rheological percolation thresholds was observed. The results confirm the expected nucleant effect of nanotubes on the crystallization process of polyethylene. A slight increase in Young's modulus was also observed with increasing MWNT content.     

Morphological and Rheological Properties of Poly(Trimethylene Terephthalate)/Maleic Anhydride Grafted Poly (Ethylene-Octene)/Organoclay Ternary Nanocomposite

Poly(trimethylene terephthalate) (PTT)/poly(ethylene-octene) POE-g-MA/organoclay ternary nanocomposites were prepared using melt blending in order to simultaneously improve the toughness and stiffness of PTT. The phase morphology and dispersion of organoclay were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM). The melt rheological behavior of the ternary nanocomposites was determined by plate/plate rheological measurements. XRD and TEM analysis indicated that the ternary nanocomposites contained exfoliated nanoparticle when a small amount of organoclay (1 part per hundred) was added. The high aspect ratio of the organoclay platelets induced the average size of the dispersed domain to become smaller. Melt rheological studies revealed that the ternary nanocomposites exhibited strong shear thinning behavior and showed good processability.     

Mechanical Properties,Rheology, and Crystallization of Epoxy-Resin-Compatibilized Polyamide 6/Polycarbonate Blends: Effect of Mixing Sequences

Blends of polyamide 6 (PA6)/polycarbonate (PC)/epoxy resin (EP) were melt blended with three different mixing sequences. Their mechanical properties, crystallization, and rheological behaviors, as well as the morphology, were investigated via mechanical testing, differential scanning calorimetry (DSC), dynamic rheometry, and scanning electron microscopy (SEM). It was noted that the mixing sequences affected the distribution of EP in the PA6 matrix, as well as the reactivity of EP with PA6 and PC. Mechanical testing showed that the blends prepared by the first (S₁, blending PA6, PC, and EP simultaneously) and second mixing sequences (S₂, blending PC with a premixture of PA6/EP) had higher notched Izod impact strengths due to the formation of PA6-EP-PC block copolymer (named as the AEC structure) during compounding, as evidenced by the results of dynamic rheology and SEM. Whereas for the third sequence (S₃, blending PA6 with a premixture of PC/EP), EP could barely react with PA6 and PC, leading to little formation of AEC structure, which resulted in a poor notched Izod impact strength of the blends. The incorporation of EP actually acted as a plasticizer to improve the elongation at break of the S₃ blends. In addition, the DSC results and SEM observations showed that there were distinct differences in the crystallization and morphology of the samples prepared by the different mixing sequences.     

Effect of Abrasives on Three-Body Abrasive Wear Behaviour of Particulate-Filled Polyamide66/Polypropylene Nanocomposites

Polyamide66/polypropylene (PA66/PP) blend, graphite (Gr)-filled PA66/PP composite and nanoclay (NC)-filled PA66/PP nanocomposites were prepared by twin screw extrusion and injection molding. Three-body abrasive wear behaviour of the injection moulded composites was carried out using a rubber wheel abrasion wear tester. In this study, angular silica sand and quartz particles of size ranging from 200 to 250 μm were used as dry and loose abrasives. The tests were carried out for 150, 300, 450 and 600 m abrading distances at a constant load of 36 N. It was observed that inclusion of particulate fillers in PA66/PP have significant influence on wear under varied abrading distances for different abrasive particles. Further, it was found that NC-filled PA66/PP nanocomposite exhibited lower wear rate compared to Gr filled ones for different abrasive particles. In addition, the worn surfaces of the samples were examined by scanning electron microscopy (SEM) and the morphology was also discussed.     

Preparation and Properties of Polyamide/Polyethylene/Near Infrared Reflective Pigment Composites

The effect of the addition of NIR (near infrared reflective pigment filler, nickel antimony titanium yellow rutile) into the polyamide/metallocene-based polyethylene elastomer (mPE) blends on increasing the infrared reflection of PA6 (Polyamide 6) and limiting the thermal heat accumulation in light of environmental and energy conservation concerns was examined. The NIR was included in mPE or mPE-g-MA (maleic anhydride) to form NmPE or NmPE-g-MA masterbatches, respectively, which were used in combination with polyamide 6 (PA6) to prepare PA6/NmPE or PA6/NmPE-g-MA composites. The dispersed domains of mPE modifier were larger in dimension in comparison with those of the corresponding counterparts using mPE-g-MA as the NIR carrier due to the increased interfacial interactions of the anhydride groups of the MA and the amine groups in PA6. NIR tended to increase the crystallization temperature of PA6 of up to 3°C through the nucleation role of the NIR for the NmPE-filled samples. However, this increment was diminished at higher mPE-g-MA content for the NmPE-g-MA-filled samples, suggested to be due to the interaction of mPE-g-MA and PA6 impeding the chain mobility for crystallization growth, offsetting the nucleation role of NIR. The NmPE-g-MA modified samples resulted in the highest improvement in Young’s modulus compared with the NmPE modified samples. An increase of 2 times in the impact strength occurred for PA6/NmPE(60 phr) sample, which increased to a value of 80?±?5 (J/m). However, a non-break behavior was observed for the PA6/NmPE-g-MA samples at higher modifier contents. The values of infrared reflection increased significantly, indicating the effectiveness of NIR to improve the reflection properties of the prepared composite systems.     

Non‐Isothermal Crystallization Kinetics of PA6/Attapulgite Composites Prepared by Melt Compounding

The non‐isothermal crystallization behaviors of neat polyamide 6 (PA6) and PA6/attapulgite (ATB) composites were examined using differential scanning calorimetry. The results show that ATB acts as a nucleator for PA6 matrix, accelerating the crystallization, and simultaneously obstructs the crystallization especially for the composites with higher ATB content. The analysis results using the Jeziorny and Liu equations verify the dual actions of the nucleation and the obstruction of crystallization of the ATB in the PA6 matrix. Kissinger's method is employed to obtain the activation energy of the crystallization processes; the results further indicate that the addition of ATB may also cause the above actions. It is speculated that there is a very complicated crystallization mechanism in the PA6/ATB composites based on the analysis of Avrami exponents obtained by the Jeziorny model.     

Effect of Compatibilizer Content on the Shear and Extensional Rheology of Polypropylene/Clay Nanocomposites

The shear and extensional rheology of polypropylene (PP)/organoclay nanocomposites in the presence of various maleic anhydride grafted polypropylene (PP-g-MA) compatibilizer concentrations were investigated. The PP nanocomposites were prepared via direct melt intercalation in an internal mixer. The structures of the nanocomposites were characterized by X-ray diffraction (XRD) and scanning electron microscopy. It was found that both the compatibilized and uncompatibilized nanocomposites could form an intercalated structure. However, the organoclay particles can disperse well only in the compatibilized systems. The linear viscoelastic properties, including the storage modulus G′ and complex viscosity η* were very sensitive to the microstructure of the nanocomposites. The extensional viscosities of PP nanocomposites were enhanced under a low deformation rate with increasing compatibilizer content and displayed a lack of superposition for different strain rates. It was proposed that the lack of superposition might originate from the formation of a three-dimensional organoclay network, which decreased in its complexity and strength as the deformation rate increased.     

Rheological and Mechanical Characterization of Multi-Walled Carbon Nanotubes/Polypropylene Nanocomposites

The rheology and morphology of multi-walled carbon nanotube (MWNT)/polypropylene (PP) nanocomposites prepared via melt blending was investigated. The minor phase content of MWNT varied between 0.25 and 8 wt%. From morphological studies using a scanning electron microscopy technique a good dispersion of carbon nanotubes in the PP matrix was observed. The rheological studies were performed by a capillary rheometer, and mechanical properties of the nanocomposites were studied using a tensile and flexural tester. Both PP and its nanocomposites showed non-Newtonian behavior. At low shear rates the addition of MWNT content causes an increase in viscosity; however, viscosity is less sensitive to addition of MWNT content at higher shear rates. Flow activation energy for the nanocomposites was calculated using an Arrhenius type equation. From this calculation it was concluded that the temperature sensitivity of nanocomposites was increased by increasing of nanotube content. An increase in tensile and flexural moduli and Izod impact strength was also observed by increasing the MWNT content. From rheological and mechanical tests it was concluded that the mechanical and rheological percolation threshold is at 1.5 wt%.     

Preparation and Properties of Polyamide 66/Organo‐Vermiculite Nanocomposites

Polyamide 66/organo‐vermiculite (OVMT) nanocomposites with different clay loadings were prepared via melt mixing using a twin‐screw extruder. The vermiculite was premodified with hexadecyl trimethylammonium bromide by ball milling. The resultant polyamide 66/OVMT nanocomposites possessed an exfoliated structure as confirmed by both wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM). Mechanical property tests showed that the tensile strength, flexural modulus, and flexural strength of these nanocomposites increased dramatically with the OVMT loading, and the Charpy impact strength and fracture toughness decreased. In addition, the heat distortion temperature of the nanocomposites showed an obvious increase compared with pure polyamide 66. Finally, differential scanning calorimetry (DSC) results showed that the crystal structure and crystallization behaviors of the nanocomposites are different from those of polyamide 66.     

Nanocomposites of poly(l-lactide) and surface modified magnesia nanoparticles: Fabrication, mechanical property and biodegradability

A novel nanocomposite based on biodegradable poly(l-lactide) (PLLA) was prepared by the incorporation of surface modified magnesia (g-MgO) nanoparticles using a solution casting method. The mechanical properties, biodegradable properties and protein adhesion behavior of the g-MgO/PLLA nanocomposites were investigated. Scanning electron microscopy (SEM) results showed that g-MgO nanoparticles could comparatively uniformly disperse in PLLA matrix. The addition of g-MgO nanoparticles to PLLA matrix improved the tensile strength and elastic modulus, whereas reduced the elongation at break. The mass loss results showed that the nanocomposites with higher g-MgO content had faster degradation rates. The in vitro pH value determination results indicated that the g-MgO nanoparticles could neutralize effectively the lactic acid resulting from the degradation of PLLA. The g-MgO/PLLA nanocomposites exhibited enhanced protein adsorption, i.e., with the increase of g-MgO content, the amount of protein adsorption increased. The (5 wt%)g-MgO/PLLA nanocomposites adsorbed 33% more protein than the pure PLLA.     

Preparation and Rheological Characteristics of Ethylene‐Vinyl Acetate Copolymer/Organoclay Nanocomposites

Ethylene‐vinyl acetate copolymer (EVA) with 40 wt.% vinyl acetate content (EVA40)/organoclay nanocomposites were prepared using a melt intercalation method with several different clay concentrations (2.5, 5.0, 7.5, and 10.0 wt.%). X‐ray diffraction confirmed the formation of exfoliated nanocomposite in all cases with disappearance of the characteristic peak corresponding to the d‐spacing of the pristine organoclay. Transmission electron microscopy studies also showed an exfoliated morphology of the nanocomposites. Morphology and thermal properties of the nanocomposites were further examined by means of scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA), respectively. Rheological properties of the EVA40/organoclay nanocomposites were investigated using a rotational rheometer with parallel‐plate geometry in both steady shear and dynamic modes, demonstrating remarkable differences with the clay contents in comparison to that of pure EVA40 copolymer.     

Influence of Surfactant Functional Groups on Morphology and Rheology of Polypropylene/Organoclay Nanocomposites

Three surfactants, with the same long alkyl tail but varying in functional groups, were selected to modify two pristine clays with different cation exchange capacities (CEC). Each of the modified clays was melt-mixed with polypropylene (PP) to prepare nanocomposites. The microstructure of the resultant nanocomposites was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and rheological techniques. The results showed that the surfactant structure had remarkable effects on the morphology and shear rheology of the nanocomposites based on the high-CEC organoclay: use of benzyl functional groups led to the highest extent of intercalation and highest enhancement of shear properties, while use of 2-hydroxyethyl groups had the opposite effect. Nanocomposites based on low-CEC organoclay all exhibited poor dispersion and their shear behavior was changed only slightly in comparison to the polymer matrix. In the case of extensional rheology, strain hardening was observed only in the two nanocomposites containing surfactants with 2-hydroxyethyl groups, regardless of the dispersion state of the nanoparticles.     

Synthesis of poly(butylene succinate) nanocomposites via in-situ interlayer polymerization: thermo-mechanical properties and morphology of the hybrid fibers

A series of poly(butylene succinate) (PBS) nanocomposites with the organoclay C₁₂PPh-Mica were synthesized by using the in-situ interlayer polycondensation of 1,4-butanediol with succinic acid. The PBS nanocomposites were melt-spun to produce monofilaments with various organoclay contents and draw ratios (DRs). The thermo-mechanical properties and morphologies of the PBS nanocomposites were determined using differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray diffraction, transmission electron microscopy, and a universal tensile machine. Some of the clay particles were found to be well dispersed in the PBS matrix, with some agglomerated at a size level greater than approximately 20 nm. The thermal degradation properties of undrawn PBS hybrid fibers were found to improve with increasing clay content. The ultimate tensile strengths and initial moduli of the hybrid fibers increased with increasing clay content at DR = 1. However, the ultimate strengths were found to decrease markedly with increases in DR from 1 to 6. In contrast to the trend for the tensile strengths, the initial moduli of the hybrid fibers increased only slightly with increases in DR up to 6.