The Construction of Sandbag Microstructure in Polyamide 6/Ethylene-Propylene-Diene Terpolymer/Nanometer Calcium Carbonate Ternary Composite

A sandbag microstructure was constructed in Polyamide 6(PA6)/ethylene-propylene-diene terpolymer (EPDM)/nanometer calcium carbonate (nano-CaCO₃) ternary composites by the addition of maleinated EPDM (EPDM-g-MA) to reduce the interfacial tension between EPDM and PA6 and EPDM and nano-CaCO₃. Scanning electron microscopy (SEM) observation and differential scanning calorimetry (DSC) analysis revealed that the microstructure of the ternary composites evolved from the initial separated EPDM and nano-CaCO₃ dispersion structure to the sandbag structure and finally to the separated dispersion structure again with the increase of EPDM-g-MA content in the elastomer phase. The mechanical results showed the composites with the sandbag microstructure exhibited excellent toughness and stiffness.     

Effect of Maleated Styrene/Ethylene-co-Butylene/Styrene on the Dispersed Particles Size and Mechanical Properties of Polyamide 6/Poly(styrene-co-acrylonitrile)/Poly(styrene-b-(ethylene-co-butylene)-b-styrene) Ternary Blends

In this study, the effect of several parameters, including composition, order of mixing, viscosity, and interfacial tension, on the phase structure and size of dispersed particles of polyamide 6 (PA6)/poly(styrene-co-acrylonitrile) SAN/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) ternary blends was investigated. Moreover, the effect of addition of different ratios of reactive SEBS (maleic anhydride grafted-SEBS) and non-reactive SEBS at a fixed order of mixing and composition of 70/15/15 (PA6/SAN/SEBS + SEBS-g-MAH) on the mechanical properties of ternary blends was examined. Scanning electron microscopy (SEM) micrographs showed that among the studied parameters, interfacial tension and viscosity of dispersed phases were the leading factors in the formation of morphology and size of dispersed droplets. Mechanical results revealed that in contrast to the expectation, formation of core/shell structure of PA6/SAN/SEBS ternary blends did not result in a significant increasing of impact strength. The highest impact strength was achieved when a 50/50 weight ratio of SEBS/SEBS-g-MAH was used.     

Morphology and Mechanical Properties of Polyamide 6/Acrylonitrile-Butadiene-Styrene Blends Containing Carbon Nanotubes

The blends of polyamide 6/acrylonitrile-butadiene-styrene (PA6/ABS), with added styrene-maleic acid copolymer (SMA) compatibilizer, were prepared through melt mixing in an internal mixer. The effects of blend composition and various process conditions, as well as the addition of multi-wall carbon nanotubes (MWCNTs) to the blends, on the morphology and mechanical properties were investigated. The morphology of the blends and blend nanocomposites were observed by scanning electron microscopy (SEM) and analyzed using an image analysis technique. The mechanical behavior of the blends was investigated by tensile and also impact testing. The results showed that the blend composition as well as the processing conditions significantly affected the morphology and mechanical properties of the PA6/ABS blends. Among the various compositions, the blend with 36?wt.% of ABS and 4?wt.% of SMA compatibilizer exhibited the best mechanical properties. Comparing various speeds and times of mixing, it was found that less mixing speed and longer mixing times resulted in the favorable morphology and conditions for achievement of the desired toughness for the polyamide 6. By adding different amounts of MWCNTs to the blends, it was found that the presence of the carbon nanotubes changed the viscosity of the resulting nanocomposite and thus changed the morphology. These nanocomposites also showed an improvement in mechanical properties. The MWCNTs acted as a second compatibilizer, resulting in a synergistic effect on the mechanical properties of the PA6/ABS blend nanocomposites.     

Comparison of Mechanical Properties and Rheological Behavior of Trans-Polyisoprene/Polypropylene and Ethylene Propylene Diene Rubber/Polypropylene Thermoplastic Vulcanizates

The degree of dynamic vulcanization, mechanical properties, rheological behavior, and the ageing-resistant performance of trans 1,4-polyisoprene (TPI)/polypropylene (PP) and ethylene propylene diene rubber (EPDM)/PP thermoplastic vulcanizates with a blend ratio of 60/40 were investigated comparatively. The results showed that TPI had fully dynamically vulcanized when mixed with PP in the Hakke mixer chamber (175°C, 60 rpm) while EPDM had only partly dynamically vulcanized due to its saturated main chain backbone. With increased sulfur content, the torque at the end of the curing curves of the two thermoplastic vulcanizates (TPVs) increased in the curing characteristics measuring process as the degree of crosslinking increased. Comparing the two blends, TPI/PP-TPVs were possessed of a better mobility, a little lower tensile strength and tear strength, a little higher 100% modulus and hardness, and much lower elongation at break. EPDM/PP-TPVs had better ageing-resistant characteristics due to EPDM's saturated main chain backbone.     

Effect of Phase Arrangement on Solid State Mechanical and Thermal Properties of Polyamide 6/Polylactide Based Co-polyester Blends

The main goal of this work is to correlate morphological parameters of the binary blend of polyamide 6 (PA6) and a polylactide (PLA) based biodegradable co-polyester blend (BioFlex) (scanning electron microscopy, solvent extraction method) with the solid-state mechanical properties (stress strain analysis) as well as thermal (differential scanning calorimetry) and selected physico-chemical characteristics (Fourier transform infrared spectroscopy and water uptake analysis). The blends of PA6/BioFlex were prepared in ratios of 100/0, 90/10, 75/25, 60/40, 50/50, 40/60, 25/75, 10/90 and 0/100 in wt.%. The occurrence of co-continuous morphology was observed within the range of 40 to 60 wt.% of BioFlex. Furthermore, the results show that the co-continuous morphology of PA6/BioFlex blends significantly affected both tensile (E modulus) and thermal properties (melting enthalpy) of the blends. In the case of the tensile properties, the effect of the morphological arrangement was strongly dependent on the deformation range. The presence of BioFlex in the blends reduced the crystallizability of PA6 noticeably. Co-continuous structure formation was observed to have a significant effect on the melting enthalpy of the blend. Composition morphology dependent responses were observed in the case of the FTIR and water uptake studies.     

Flowability and Mechanical and Thermal Properties of Nylon 6/Ethylene bis-Stearamide/Carboxylic Silica Composites

Nylon 6 (PA 6)/ethylene bis-stearamide (EBS)/SiO₂- carboxylic acid-functionalized silica nanoparticles (COOH) composites were prepared by in-situ polymerization of caprolactam. SiO₂-COOH was used to enhance the compatibility between SiO₂ and PA 6 matrix. For comparison, pure PA 6 and PA 6/EBS composites were also prepared via the same method. The PA 6/EBS/SiO₂-COOH composites with low content of EBS and SiO₂-COOH had greater melt-flow index (MFI) (the value of MFI increased by 50%–80%) than the pure PA 6. The results of mechanical properties showed almost no decrease in the tensile strength of PA 6/EBS/SiO₂-COOH composites, with the bending strength decreasing by 17%–21%. However, the Izod impact strength of the PA 6/EBS/SiO₂-COOH composites was greatly improved compared with pure PA 6, which indicated that the toughness of PA 6/EBS/SiO₂-COOH had been greatly improved. The morphology of Izod impacted fractured surfaces of PA 6/EBS/SiO₂-COOH was observed by scanning electron microscopy. The results revealed that the PA 6/EBS/SiO₂-COOH composites presented a typical ductile fracture behavior with large amounts of long and large strip-like cracks. When the content of SiO₂-COOH was 0.2 wt%, the SiO₂-COOH particles were uniformly dispersed over the entire body of the PA 6 matrix. The results from differential scanning calorimetry indicated that the melting point (T_m), degree of crystallinity (X_c), and crystallization temperatures (T_c) of PA 6/EBS/SiO₂-COOH composites were lower than the pure PA 6.     

Long-Term Hydrothermal Aging Behavior and Aging Mechanism of Glass Fibre Reinforced Polyamide 6 Composites

Long-term hydrothermal aging of polyamide 6 (PA6)/glass fibre (GF) composites was conducted and the effects of the GF on variations of structure and properties of the composites with aging time were investigated. It was found that the first stage of aging was a Fickian process and corresponded to the physical absorption of water until equilibrium, resulting in a slight change of reduced viscosity and chemical structure of the PA6. The water diffusing process was slowed down slightly by addition of the GF. The second stage of aging was the initiation process of hydrolytic degradation of PA6, resulting in a rapid decrease of reduced viscosity and an increase of end group content. In the final stage of aging, the relative weight gain (W_r) dropped, the reduced viscosity decreased and the end groups increased slowly. The degradation rate and carbonyl index of PA6 increased with increasing GF content, and the increasing rate of end groups concentration of the composites was higher than that of pure PA6 during the aging process, indicating addition of GF accelerated the hydrolysis degradation and oxidative aging of PA6. In mechanical property tests, compared with unaged samples of the composites which underwent matrix rupture around the matrix-fiber interfacial layer, for aged samples several smooth fibres without coatings were pulled out and the interfacial debonding was the main failure mode, causing severe deterioration in mechanical properties. The hydrolytic degradation activation energy (E_a) was calculated through a method based on the Arrhenius model by considering both temperature and humidity as environment factors; with increasing GF content, E_a decreased, indicating that the addition of GF made PA6 easier to degrade.     

Non-Isothermal Crystallization Kinetics of Polyamide 6/h-Boron Nitride Composites

Hexagonal boron nitride nanosheets were mixed with polyamide 6 to fabricate polymer-based composites by using a solution blending method. The nonisothermal crystallization behaviors of the as-prepared composites were investigated via differential scanning calorimetry. Results showed that the peak temperature of the exothermic crystallization curve was moved to lower temperature with increase in the cooling rate. At the same cooling rate, the peak temperature of the pure polyamide 6 was lower than those of the composites. Moreover, the crystallization rate increased gradually with increase in the cooling rate. In addition, at the cooling rates of 5 or 10°C min^?1, the crystallization rate of pure polyamide 6 was higher than those of all compositions of the composites. However, at the cooling rates of 20 or 40°C min^?1, the crystallization rate decreased first and then increased with increase in the fillers loading. The crystallization mechanism was between one-dimensional and two-dimensional during the crystallization process.     

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.     

Rheology,Crystallization, Mechanical and Barrier Properties of Polyamide 6/66 Nanocomposites with Exfoliated Organoclays

Nylon copolymer/clay (NC) nanocomposites were prepared using PA6/66 as a matrix and organoclay as a nanofiller through a two-step melt-compounding method. It was shown that the organoclay flakes were well exfoliated and dispersed in the PA6/66 matrix. With increasing content of organoclay, the apparent shear viscosity and the entrance pressure drop of the NC nanocomposites decreased whereas the corresponding shear activation energy increased, suggesting that the NC nanocomposites were suitable to be used in shear-flow rather than extension-flow related processes. Investigations of the crystallization behaviors of the NC nanocomposites indicated that the organoclay addition was capable of facilitating the γ-form crystal formation, which is suggested to be due to the restriction effect of the organoclay on the PA6/66 chain motion during the crystallization. Compared to the neat PA6/66, the tensile strength and elongation at break of the NC nanocomposites were both enhanced at an appropriate content of the organoclay. In addition, the NC nanocomposites exhibited enhanced barrier properties due to the high specific surface area and the homogeneous dispersion of the organoclay.     

The Mechanical and Tribological Properties of Aramid (Twaron) Fabric/Polytetrafluoroethylene Composites

A series of composites with Twaron fabric as reinforcement and polytetrafluoroethylene (PTFE) as matrix were fabricated with various contents of PTFE, viz. 30, 40, 50, 60, and 70 vol%. The Rockwell hardness and tensile strength of the composites were tested according to the corresponding standards. The composites were also evaluated for their tribological behaviors on an MPX-2000A friction and wear tester. The worn surface and wear debris of the composites were observed by scanning electron microscopy (SEM) and the mechanism is discussed. The PTFE content in the composites had a great influence on both the mechanical and tribological properties. The composite with 40 vol% PTFE provided the proper wetting of the fibers and the best load transfer efficiency and, hence, showed the best mechanical properties and tribological behaviors.     

Dynamic Mechanical and Dielectric Properties of Ethylene Vinyl Acetate/Carbon Nanotube Composites

A comparative study of the dielectric and mechanical properties of ethylene vinyl acetate copolymer (EVA) filled with various concentrations of pristine and modified carbon nanotubes is reported. The surface of the carbon nanotubes was modified with 4-(2-(cholesteryloxycarboxy)ethyl) phenyl to improve the interaction of the filler with the block copolymer matrix. The improved interaction and the better dispersion of the modified carbon nanotubes (mMWCNTs) were demonstrated by a detailed study of the EVA molecular mobility through dynamic mechanical analysis and broadband dielectric relaxation spectroscopy. The storage modulus of the nanocomposite with 6 wt.% of mMWCNTs at ?50°C was enhanced by 103%, whereas for the nanocomposite with the same amount of unmodified filler, the storage modulus was only enhanced by 76% compared to the pure elastomeric matrix. This difference is more pronounced in the rubbery region in which the storage moduli were increased by 117% and 48% for the composite with the modified and unmodified fillers, respectively. The morphologies of the nanocomposites were studied with scanning and transmission electron microscopies to demonstrate the dispersion of the mMWCNTs within the EVA matrix.     

Metal-Filled Epoxy Composites: Mechanical Properties and Electrical/Thermal Conductivity

Abstract

The mechanical properties and the electrical and thermal conductivity of composites based on an epoxy polymer (EP) filled with dispersed copper (Cu) and nickel (Ni) were studied. It was shown that the electrical conductivity of the composites demonstrated percolation behavior with the values of the percolation threshold being 9.9 and 4.0?vol.% for the EP-Cu and EP-Ni composites, respectively. Using the Lichtenecker model, the thermal conductivity of the dispersed metal phase in the composites, λ_f, was estimated as being 35?W/mK for Cu powder and 13?W/mK for Ni powder. It was shown that introduction of the filler in EP led to a decrease in the intensity of the mechanical loss tangent (tan δ) peak that was caused by the existence of an immobilized polymer layer around the filler particles which did not contribute to mechanical losses. Using several models the thickness of this layer, ΔR, was estimated. The concept of an “excluded volume” of the polymer, V_ex, i.e. the volume of the immobilized polymer layer, which does not depend on the particle size and is determined solely by the value of the interaction parameter, B, was proposed.     

Preparation and Combustion Behavior of Polyamide 6/Polypropylene/Clay Nanocomposites

Polyamide 6(PA 6)/Polypropylene (PP) blends as well as PA 6/PP/clay composites were prepared by melt compounding. The distribution of clay was characterized by transmission electron microscopy. The combustion surface morphology as well as product composition after burning were studied by scanning electron microscopy along with electro-probe microanalysis. Moreover, the flame retardance and thermal stability were evaluated by a cone calorimeter together with thermogravimetric analysis. The results showed that the clay was selectively located in the PA6 phase. It is proposed that, in the presence of clay, the combustion surface changed from a branch-shaped structure to a compact carbonaceous–silicate structure. When the clay content was 3 phr, the layered silicates became enriched on part of the surface and formed an island-like structure; the islands displayed a loose cinders structure with much higher silicon content, in contrast to a branch-shaped surface with low silicon content of the surrounding polymer substrate. As the clay content continued to increase, the char covered most of the combustion surface and more clay accumulated on the burning surface. In addition, the clay particles promoted the formation of the carbonaceous–silicate structure. The peak of the heat release rate of the PA6/PP blend decreased with increasing addition of clay and the thermal stability of the PA6/PP blend also improved.     

The Structure and Properties of Polyamide/Liquid Crystal Polymer Blends

Melt blended polyamide (PA)/liquid crystal polymer (LCP) blends were prepared and their structures and properties were studied. The tensile strength and impact strength of the PA/LCP blends increased with increasing small amount of LCP content. Compared with a pure PA sample, there was a 17.7% increase in the tensile strength and a 45.5% increase in the impact strength when the LCP content was less than 10%. On the other hand, the Vicat softening temperature decreased with increasing the LCP content. Differential scanning calorimetry (DSC) showed that small addition of LCP was beneficial to increase the crystallinity of PA component for PA/LCP blends and the melting peak for the PA component of PA/LCP blends shifted to lower temperature with increasing LCP content. Scanning electron microscopy (SEM) displayed a layered structure existing in the injection moldings of PA/LCP blends with the LCP crystals having a preferred orientation along the melt flow direction in the sub-skin, shearing layer, and core region. The increased crystallinity of PA component and preferred orientation structure of LCP phase were beneficial to increase the mechanical properties of the PA/LCP blends.     

Investigation of Network Structure and Dynamic Mechanical Properties of Peroxide-Cured Ethylene Propylene Diene Rubber

The effect of peroxide and co-agent amount on the cure behavior, network structure, and dynamic mechanical properties of ethylene-propylene elastomers were studied by moving die rheometer, equilibrium swelling and dynamical mechanical measurements. The increase in peroxide and co-agent concentrations resulted in an increase in total cross-link density, C_tot. The model calculation results based on torque measurements considered the changes in C_tot as a function of peroxide and co-agent content; it linearly depended on initial peroxide content when the co-agent content was constant. The torque measurements were also carried out to investigate the cross-linking efficiencies of the peroxide and the co-agent triallyl isocyanurate (TAIC); the efficiencies were evaluated as 77–95% and 33%, respectively, but the use of TAIC didn't affect the scorch time and rate constants of EPDM compounds significantly. The incorporation of TAIC into the network enhanced the network heterogeneity, the glass transition temperature shifted towards higher temperature and the peak values of the loss factor gradually decreased, both of which were caused by restricted segmental mobility due to the increase in cross-link density.     

Mechanical and Tribological Properties of Self-Reinforced Polyphenylene Sulfide Composites

25%, 50%, and 75% polyphenylene sulfide (PPS) long fiber reinforced PPS resin were prepared by a hot pressing method. Neat resin PPS and PPS fiber samples were also prepared to compare with the self-reinforced PPS composites. The reinforcing fibers were preheat treated at 240°C for 24 h. The tribological properties of the self-reinforced PPS composites against an AISI 1045 steel ring were determined by a block on ring type friction tester. Differential scanning calorimetry (DSC) results indicated that a higher degree of crystallinity was retained in the self-reinforced PPS composites than in neat PPS resin after hot pressing. Therefore, the addition of PPS fiber improved both the mechanical and tribological properties of PPS resin significantly. Dynamic mechanical analysis (DMA) demonstrated that the PPS fibers increased the glass transition temperature (Tg) of the PPS resin. SEM images of the fracture surfaces indicated that the toughness of the samples increased with increasing PPS fiber content. Additionally, PPS fibers improved the tribological properties of PPS resin by significantly reducing the friction coefficient and wear rate.     

Study on the Morphological and Mechanical Properties of Nylon 6/ABS/Nano-SiO2 Composites

The mechanical properties and morphology of the composites of nylon 6, acrylonitrile-butadiene-styrene (ABS) rubber, and nano-SiO₂ particles were examined as a function of the nano-SiO₂ content. A mixture with separation and encapsulation microstructures existed in the nylon 6/ABS/nano-SiO₂ at lower nano-SiO₂ content, and ABS and nano-SiO₂ improved the toughness synergistically, while obvious agglomeration appeared at higher nano-SiO₂ content and the impact strength decreased. Moreover, the addition of nano-SiO₂ particles also affected the dispersion of the rubber phase, resulting in the appearance of smaller rubber particles. The deformation and toughening mechanisms of the composites were also investigated; they resulted from rubber voiding, crack forking, and plastic deformation of the matrix.     

Effect of Wood Flour on the Curing Behavior,Mechanical Properties,and Water Absorption of Natural Rubber/Wood Flour Composites

The preparation of natural rubber/wood flour (NR/WF) composites and the influence of WF content, modification, and particle size on the vulcanizing behavior, mechanical properties, and water absorption of NR/WF composites are described. Results show that the addition of WF into NR delayed the scorching time and vulcanizing time of NR. The appropriate WF contents can improve the mechanical properties of NR. However, the overloading of WF destroys the mechanical properties of NR. The addition of WF increased the water absorption of NR. The silicone couple agents that were used to modify the WF had little effect on the water absorption of NR/WF composites. Decreasing the WF particle size enhanced the water absorption of NR/WF composites because the water-absorbing surface area increased with decreasing WF particle size. The water absorption of sisal-fiber-filled NR-based composites was larger than that of the WF-filled NR-based composites. A useful equation, w=ktⁿ , was inferred from the water absorption results to calculate the water absorption (w) of the NR/WF composites as a function of time (t), where k was a constant concerning the compounds’ character that was primarily determined by the WF's character and n was the power of time that was related to the NR's inherent character, such as cross-linking density, and primarily determined the water absorption rate.     

Effect of Inorganic Fillers on Morphology and Mechanical Properties of PA66/POE-g-MAH/Filler Composites

Composites of polyamide 66 (PA66)/maleic anhydride grafted poly(ethylene-co-octene) (POE-g-MAH)/nano-calcium carbonate (nano-CaCO₃) and PA66/POE-g-MAH/talc were prepared by a one-step blending method. Morphology, crystallization, and mechanical properties of the composite materials were characterized with respect to different amounts of both inorganic fillers, nano-CaCO₃ and talc. Results showed that the tensile yield strength and tensile modulus of the composites were increased remarkably with introduction of nano-CaCO₃ or talc, but the notched impact strength was significantly lowered for both kinds of composites. Mechanical properties exhibited little difference between the PA66/POE-g-MAH/nano-CaCO₃ and PA66/POE-g-MAH/talc composites both for the different shapes and sizes of nano-CaCO₃ and the flake-like talc. Results of scanning electron microscopy exhibited agglomeration of the fillers. Differential scanning colorimetry analysis suggested that introduction of the inorganic fillers cause the crystallinity of PA66 to decrease by heterogeneous nucleation. The study provides a basic investigation on polymer/elastomer/rigid filler composites.