Foaming and Damping Properties of Ethylene Vinyl-Acetate Copolymer/Polylactic Acid Blends

With ethylene vinyl-acetate copolymer (EVM) and polylactic acid (PLA) blends as the matrix, dicumyl peroxide (DCP) as the curing agent and azodicarbonamide (AC) as the foaming agent, EVM/PLA foamed blends were prepared by compression molding. The effects of different amounts of AC, DCP, and silica, as well as varying foaming time, on the cell structure and damping properties of the EVM/PLA-foamed blends were examined by scanning election microscopy (SEM) and dynamic mechanical analysis (DMA). The results showed that the cell size and damping properties varied little with increasing AC content in the compounds; however, the cell size declined slightly as DCP increased and the damping properties rose slightly, exhibiting an optimum set of properties at 5 phr of DCP. The cell size declined dramatically and damping increased significantly as the foaming time was increased. Moreover, both suddenly increased after 5 min foaming. It was found that the damping properties of the foamed materials increased with decreasing cell size and increasing number of cells. The cell size also decreased and damping properties increased as the silica content was increased. The silica interacted more strongly with EVM than with PLA.     

Mechanical,Thermal, and Rheological Properties of EPDM-graft-methyl Methacrylate and Styrene (EPDM-g-MS)/Methyl Methacrylate-Styrene Copolymer (MS Resin) Blends

EPDM-graft-methyl methacrylate and styrene (EPDM-g-MS) were synthesized by solution graft copolymerization of methyl methacrylate (MMA) and styrene (St) onto ethylene-propylene-diene terpolymer (EPDM). EPDM-g-MS/MS resin blends (MES) tht were prepared by melt blending EPDM-g-MS and methyl methacrylate-styrene copolymer (MS resin). The mechanical properties, compatibility, thermal stabilities and rheological properties of MES were studied by the pendulum impact tester and the tension tester, differential scanning calorimetric (DSC), thermogravimetry analysis (TGA), and the capillary rheometry, respectively. The results showed that EPDM-g-MS had an excellent toughening effect on MS resin; the notched Izod impact strength of MES reached 20.7 kJ/m² when EPDM content in MES was 25 wt%, about 14 times that of MS resin. EPDM-g-MS and MS resin were partially compatible, and the compatibility increased with an increasing MMA/St ratio of EPDM-g-MS. MES had excellent heat-resistance, which increased as the EPDM content in MES and MMA/St ratio of EPDM-g-MS rose. MES melt flow confirmed pseudoplastic flow characteristics. The apparent viscosity (η _a ) of MES decreased with an increasing shearing rate (γ) and temperature, but increased with an increasing EPDM content in MES and MMA/St ratio of EPDM-g-MS. The flow activation energy of MES was lower than that of MS resin.     

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.     

Phase Structure,Thermal, and Mechanical Properties of Polypropylene/Hollow Glass Microsphere Composites Modified with Maleated Poly(ethylene-octene)

Maleated poly(ethylene-octene) (POE-g-MAH), as a compatilizer and toughener, was incorporated in polypropylene/hollow glass microspheres (PP/HGM) binary composites, and the phase structure and thermal and mechanical properties of these composites were investigated. Scanning electron microscopy analysis indicated that the phase structure of ternary composites could be controlled by POE-g-MAH and the surface treatment of HGM. Fourier transform infrared spectroscopy revealed that there was an amidation reaction between the treated HGM and POE-g-MAH during melt compounding. Differential scanning calorimetry suggested that the crystallization and melting behaviors of ternary composites were influenced by phase structure. Evaluation of mechanical properties showed that the amide linkage between the treated HGM and POE-g-MAH was favorable for improving the properties of ternary composites.     

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.     

石墨烯/羟基磷灰石复合材料力学性能的数值研究

为了研究石墨烯/羟基磷灰石复合材料力学性能（弹性模量和泊松比）,开发了石墨烯/羟基磷灰石复合材料的随机分布模型自动生成算法及相应的计算程序;建立石墨烯/羟基磷灰石复合材料的有限元模型,计算添加不同质量分数的石墨烯对复合材料力学性能的影响,通过与实验数据对比验证算法的有效性.结果表明：添加0.25%~1.25%（质量分数）的石墨烯可使复合材料的弹性模量增加12%~50%,表明添加少量石墨烯即能有效地改善羟基磷灰石的力学性能.     

Preparation of Silicon Carbide Nanoparticle/Butadiene Rubber/Silane Nanocomposites; Structural,Mechanical, Tribological and Thermal Properties

Silicon carbide nanoparticles (nano-SiC), in the amounts of 0, 3, and 5 parts per hundred of rubber (phr), were employed in a butadiene rubber (BR) based compound as a potential commercial rubber and the structure, mechanical, tribological and thermal properties of the samples were investigated. The use of 3 phr of nano-SiC, especially in the presence of silane, increased the crosslink density and improved the tensile strength (35%) and elongation at break (64%) of the BR. In addition; the abrasion resistance of the BR was improved about 120% and the coefficient of friction increased. Scanning electron microscopy (SEM) images revealed the use of silane resulted in an appropriate dispersion of the nano-SiC and improvement of its interaction with the matrix. The use of nano-SiC, especially with silane, increased the initial thermal decomposition temperature of the BR and decreased its rate of degradation.     

Morphological,Thermal and Mechanical Properties of Compatibilized Nylon 6/ABS Blends

Super‐tough nylon 6/ABS blends were prepared by using styrene/acrylonitrile/maleic anhydride co‐polymer (SAM) as a compatibilizer. The variations in morphology, mechanical behavior, and crystallinity associated with the reaction of the SAM with the nylon were characterized. The results showed that the addition of SAM to nylon 6/ABS blends enhanced the interfacial adhesion between nylon 6 and ABS, and this led to the decrease of ABS domain size and the improvement of mechanical properties of their blends. Moreover, it could be found that the crystallinity and phase morphology changed with the variation of SAM.     

Thermal and Mechanical Properties of Poly(lactic acid)/Modified Carbon Black Composite

Poly(ethylene glycol) (PEG) was added as a plasticizer to the composite of poly(lactic acid) (PLA) and a modified carbon black (MCB). Among the three different molecular weight (M_n = 1000, 2000, 6000) PEGs used, PEG2000 promoted crystallization of PLA and enhanced the nucleation activity of MCB more efficiently than the other two. The crystallization rate of PLA/PEG2000/3 wt% MCB composite was three times that of PLA. Although a small decrease in tensile strength and modulus of elasticity of the composite was found as the PEG content increased, the elongation at break of the PLA/PEG/MCB composites significantly improved. When the PEG2000 content was 15 wt%, the elongation at break of the blend was 90%, 4.5 times that of the neat PLA.     

Effects of Viscosity Ratio on Morphological,Rheological and Mechanical Properties of PP/PBT Melt Spun Alloy Fibers

Phase morphology formation plays an important role in the mechanical properties of polymer alloy fibers. The development of the blend morphology depends not only on the intrinsic properties of the component polymers but also on extrinsic factors such as viscosity ratio, λ, in the melt spinning process. The effects of blend component viscosity ratio on the morphological, rheological, and mechanical properties of polypropylene/poly(butylene terephthalate) (PP/PBT) melt spun alloy fibers were investigated. Accordingly, two kinds of PP as matrix phase and two kinds of PBT as dispersed phase, with various melt viscosity, were physically mixed and then blended during the extrusion step of melt spinning. SEM micrographs and rheological and mechanical properties evaluations showed that the morphology of PP/PBT alloy fibers strongly depend on the viscosity ratio, λ. Finer diameter PBT fibrils were observed for Viscosity ratios less than 1 (λ < 1) compared to samples with λ > 1. The best mechanical properties in alloy fiber samples were obtained for the viscosity ratio closest to unity (sample with λ = 0.9). The lowest differences among measured complex viscosities at various shear rates (0.1, 10, and 100 s^?1) were also observed in samples with λ = 0.9. The results showed that the mechanical properties of alloy fiber samples are affected not only by morphological properties observed at different viscosity ratios but also by the properties of the individual polymer components.     

The Mechanical Properties,Compatibility, and Thermal Stabilities of POE-Graft-Methyl Methacrylate and Acrylonitrile(POE-g-MAN)/ Styrene-Acrylonitrile Copolymer (SAN Resin) Blends

POE-graft-methyl methacrylate and acrylonitrile (POE-g-MAN) was prepared by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto polyethylene-octene copolymers (POE) with suspension polymerization. POE-g-MAN/SAN resin blends (AOMS) were prepared by blending POE-g-MAN with styrene-acrylonitrile copolymer (SAN resin). The mechanical properties, compatibility, and thermal stabilities of AOMS were studied. The notched impact strength of the blends reached 54.0 kJ/m² when the AN/(MMA + AN) ratio (f_AN) of POE-g-MAN, benzoyl peroxide dosage, and POE content in AOMS were 15 wt%, 1.0 wt%, and 25 wt%, respectively. Transmission electron microscopy analysis showed that the highest toughness occurred when the size of POE-g-MAN particles and the surface-to-surface inter-particle distance were proper. Scanning electron microscopy analysis indicated that the AOMS fracture surface had plastic flow visible, which looked like a fibril morphology when the AN/(MMA + AN) ratio (f_AN) of POE-g-MAN was 15 wt%. The toughening mechanism of AOMS was shear yielding of the matrix, which endowed AOMS with remarkable toughness. Dynamic mechanical thermal analysis showed that the compatibility of the POE phase and SAN phase improved after graft copolymerization of MMA and AN onto POE. When the grafting chain polarity was appropriate, the miscibility between POE-g-MAN and SAN resin was the best. Thermogravimetry analysis showed that thermal stability of AOMS increased with increasing AN units in POE-g-MAN.     

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%.     

Dispersion Properties of Photonic Crystal Fiber: Comparison by Scalar and Fully Vectorial Effective Index Methods

The development of analysis and simulation of propagation characteristics of photonic crystal fiber (PCF) using scalar and fully vectorial effective index methods are described. As a result, we report how the fundamental space filling mode, guided mode and dispersion of the PCF depends on its structural parameters like its normalized air hole spacing, center-to-center spacing of the air holes in the photonic crystal or pitch and radius of the unit cell. Normalized frequency parameter V_eff as a function of normalized wavelength for various relative air hole sizes is obtained to estimate the dispersion characteristics of PCF. It is observed that wavelength of zero dispersion, ultraflattened dispersion response and high negative dispersion remarkably differ from two different effective index methods.     

On Localization of Clay Nanoparticles in Polypropylene/poly(Lactic Acid) Blend Nanocomposites: Correlation with Mechanical Properties

Two polypropylene (PP)/polylactide (PLA)/clay ternary nanocomposite systems, i.e. PP-rich and PLA-rich ones, each containing various amounts of one of two types of clay, were prepared by one step melt compounding in a twin screw extruder. The microstructures of the developed systems were correlated with tensile and impact properties. A theoretical calculation using wetting coefficients was used for predicting the clay nanoparticles localization in the blends. The nanoparticles were almost completely located within the PLA phase in both the PP-rich and PLA-rich systems, in good agreement with the predictions. Addition of a compatibilizer led to localization of the nanoparticles at the interfaces of the blends. From the wide angle X-ray scattering (WAXS) spectra it was concluded that the incorporation of clay led to intercalated structures in the both systems. The increase in impact toughness of the compatibilized blend nanocomposites, with respect to the uncompatibilized ones, was attributed to the weakened interfacial debonding in the presence of the interfacial-localized nanoparticles.     

Morphology,Rheology, and Mechanical Properties of Polylactide/Poly(Ethylene-co-octene) Blends

Polylactide (PLA)/poly(ethylene-co-octene) (POE) blends containing ethylene-glycidyl methacrylate copolymer (EGMA) as a compatibilizer were prepared by melt blending. An immiscible, two-phase structure with POE dispersed in the PLA matrix was observed by scanning electron microscopy. It was found that the POE particle size was significantly decreased by the addition of EGMA, and the POE particle size and distribution decreased with the increase of the compatibilizer content up to 2% EGMA, beyond which the POE particle size and distribution remained unchanged. The reactions between the epoxy groups of EGMA and carboxylic or hydroxyl groups of PLA were elucidated by the Fourier transform infrared spectroscopy. Rheological results showed that the G′(ω), G″(ω), and complex viscosity of PLA/POE blends significantly increased at low frequencies with the addition of EGMA. The failure mode changed from brittle fracture of the neat PLA to ductile fracture of the PLA/POE blends.     

The Effect of Talc on the Mechanical,Crystallization and Foaming Properties of Poly(Lactic Acid)

Poly(lactic acid) (PLA)/talc composites containing different contents of talc were prepared by melt blending. Multiple properties of the prepared composites were investigated including mechanical, rheological and crystallization as well as foaming properties. Tensile test results indicated that the mechanical properties of the composite with 3% wt. talc showed significant reinforcement and toughening effect. When the talc content reached 10%, Young's modulus of the composite was increased by 35% compared with pure PLA. The morphological results showed that the talc layers were partially delaminated and uniformly dispersed in the PLA matrix at low loading. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) results indicated that 3% wt. talc significantly increased the crystallinity of the PLA matrix. The thermogravimetric analysis (TGA) results demonstrated that the thermal stability of PLA/talc composites was enhanced as well. Moreover, talc at low loading could act as a plasticizer in the polymer flow, which was investigated by rheological tests. The batch foaming experiments revealed that 3% wt. talc loading had the most notable heterogeneous nucleation effect, with the cell size decreasing from 15.4 μm for neat PLA to 8.5 μm and the cell density increasing by 298%.     

Mechanical,Biodegradation and Morphological Properties of Sisal Fiber Reinforced Poly(Lactic Acid) Biocomposites

Sisal fiber-reinforced poly(lactic acid) (SF/PLA) biocomposites were prepared by melt mixing and subsequent compression molding. The effect of fiber content and sodium hydroxide (NaOH) concentration, used for the fiber mercerization, on the properties of the biocomposites was investigated. It was found that the SFs had a large potential for improving the mechanical properties of the biocomposites. The tensile strength and impact strength increased linearly up to a fiber content of 20%, and then decreased due to the fiber agglomeration. The water absorption was enhanced with increasing the SF content owing to the SFs containing an abundance of hydroxyl groups. The biodegradability of the SF/PLA biocomposites increased similarly. Furthermore, the mercerization led to an increase of the mechanical properties of the biocomposites, which normally depended on the fiber-matrix adhesion. The mercerization had competing effects on the water absorption and biodegradability, including not only the positive function of the improved hydrophilicity of the mercerized-SF but also the negative role of the increase of fiber-matrix interfacial adhesion. Overall, the optimum SF load for mechanical properties was 20?wt% due to a good balance between the reinforcement and distribution of the SFs, whereas the 6% NaOH concentration was optimal owing to the resulting fibers yielding the highest mechanical properties and acceptable water resistance and biodegradability.     

The Effects of Morphological Properties of Henequen Fiber Irradiated by EB on the Mechanical and Thermal Properties of Henequen Fiber/PP Composites

The aim of this study was to investigate the effects of electron beam (EB) irradiation on the morphological properties, crystallinity and surface area of henequen fiber and on the mechanical and thermal properties of henequen fiber reinforced polypropylene (PP) composites. The structure of henequen fiber was characterized by X-ray diffraction, mercury porosimetry and BET surface area analysis. The EB irradiation of 10 kGy led to the increasing of crystalline and surface pore area of henequen fiber, which contributed to the number of interlocking places with PP. From the results of tensile and impact strength tests, the highest value was observed for the composite reinforced with the henequen fiber treated with EB dose of 10 kGy, decreasing overall as EB dose increased. This tendency was also shown by coefficient of thermal expansion (CTE) measurements, but the value of CTE decreased until 50 kGy, meaning that a large total surface area can provide many interlocking places and so improve adhesion between fiber and matrix. Therefore, it can be concluded that the optimum pore surface area by 10 kGy irradiation contributes to successful mechanical interlocking between fiber and matrix and consequently enhances the mechanical and thermal properties of the composites.     

Mechanical Properties and Flow Behavior of Polymers for Enhanced Oil Recovery

The mechanical properties and flow behavior in porous media of three different polymer systems including a hydrophobically modified acrylamide-based copolymer (HMSPAM), a partially hydrolyzed polyacrylamide (HPAM), and a polysaccharide (xanthan gum) were evaluated to establish their functional differentiation as mobility control agents in enhanced oil recovery (EOR). The rheological properties of the polymers were described by the power-law model to investigate their non-Newtonian behavior. The first normal stress difference (N₁) and Weissenberg number (W_e) were also used to compare their elastic properties. The experimental results showed that, at comparable shear viscosity, HMSPAM exhibited significant elasticity compared to HPAM and xanthan gum. Shear resistance tests indicated that all of the polymers experienced an extra stress when converging into a capillary tube due to the “entrance effect.” Xanthan gum was the most mechanically stable polymer. Moreover, HMSPAM showed the superior reformability which was quantified by the regained viscosity with relaxation time. This could be explained by the rapid re-association of the hydrophobic interactions. Sandpack flood tests indicated that HMSPAM rendered extremely high mobility control ability during polymer flooding suggesting its potential in EOR. However, this polymer also experienced significant retention within the porous media (potential injectivity and plugging problems), which may be attributed to the formation of bulky associative polymer networks. In this work, UV spectrometry was employed to monitor the concentration of the produced polymer solutions and quantify the polymer retention within porous media. This analytical approach offers great reliability and simplicity. It was concluded that the use of a particular polymer system depends on the oil reservoir conditions and the target EOR application.     

Thermoplastic Elastomers Based on Natural Rubber/Polypropylene Blends: Effect of Blend Ratios and Dynamic Vulcanization on Rheological,Thermal, Mechanical,and Morphological Properties

Thermoplastic elastomers (TPEs) based on natural rubber (NR)/polypropylene (PP) with different blend ratios were prepared and studied. The TPEs were obtained by dynamic vulcanization of NR/PP using a sulfur (S)/N-tert-butyl-2-benzothiazolesulphenamide (TBBS) and tetramethylthiuram disulphide (TMTD) curative system during processing in the melt state in an internal mixer equipped with cam rotors. Rheological, thermal, mechanical, dynamic, and morphological properties of the TPEs prepared were investigated. Based on this study a mechanism for the NR crosslinking was proposed where the sulfur vulcanization occurs through radical substitution in the forms of polysulfide bridges. The dynamic vulcanization process increases the stiffness of the NR phase in the TPEs and modifies the rheological and thermal behavior of the system compared to the behavior of the basic material PP. The crosslinked NR particles restrict the spherulitic growth and the regular arrangement of the spherulites of PP phase, decreasing the crystallinity degree. On the other hand, a reduction of mobility of the chain segments was also observed and, consequently, an increase of the T_g values. NR/PP TPEs with high content of NR showed superior mechanical performance compared to the uncrosslinked NR/PP blends in terms of tensile strength, Young's modulus and hardness. An increase of approximately 320% in Young's modulus values was obtained for the NR70/PP30 TPE compared to NR70/PP30. Morphological studies revealed the formation of large aggregates of NR domains in NR/PP TPEs which increased in size with an increase of the rubber content.