Effect of Silane Coupling Agent and Compatibilizer on Properties of Short Rossells Fiber/Poly(propylene) Composites

Rossells fiber reinforced polypropylene composites were prepared by melt mixing. The fiber content was 20 wt%. Octadecyltrimethoxysilane (OTMS) and maleic anhydride grafted polypropylene (MAPP) were used to improve the adhesion between poly(propylene) (PP) and the fiber. The mechanical, rheological, and morphological properties, and heat distortion temperature (HDT) of the composites were investigated. Tensile strength, impact strength, flexural strength and HDT of MAPP modified PP composites increased with an increase in MAPP content. However, no remarkable effect of MAPP content on the Young's modulus of the composites was found. OTMS resulted in small decreases of tensile strength and Young's modulus, and increase in impact strength. Scanning electron micrographs revealed that MAPP enhanced surface adhesion between the fiber surface and PP matrix.     

Mechanical and morphological properties of injection-molded rice husk polypropylene composites

In this work, the investigation of the physical, mechanical, and morphological properties of the rice husk flour/polypropylene composites was performed utilizing various filler loadings and coupling agent. Five levels of filler loading (35, 40, 45, 50, and 55 wt%) were designed. In addition, to help the interaction between fiber and polypropylene matrix, struktol coupling agent was added to the composites. All of tensile strength, Young's modulus, flexural strength, flexural modulus, and impact strength properties of the composites were carried out. Moreover, the 50 wt% filler-loaded composites had optimum tensile strength, flexural strength, and flexural modulus, whereas the 35 wt% of filler loading case was the best regarding Young's modulus, flexural strength, flexural modulus, and impact strength. Furthermore, the scanning electron microscope results demonstrate that as filler loading increases, more voids and fiber pullout occur.     

Bio-Based Nanocomposites of Cellulose Acetate and Nano-Clay with Superior Mechanical Properties

Summary: Bio-based nanocomposites were manufactured by melt intercalation of nanoclays and cellulose acetate (CA) with and without plasticizer. Glycerol triacetate (triacetin) as plasticizer up to 30 mass%, and different types of organo-modified and unmodified montmorillonites (MMTs) as filler were used. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were used to study clay dispersion, intercalation/exfoliation, and structure of the composites. XRD and TEM revealed very good dispersion and exfoliation of modified clay throughout the CA matrix. While for unmodified clay agglomeration and poor dispersion but an intercalated structure was observed. The mechanical properties of injection moulded test bars were determined by a tensile experiment giving tensile strength, Young's modulus and elongation at break. Adding plasticizer facilitated the processing and up to 20 mass%, increased the tensile strength, Young's modulus and elongation at break as well. Higher amount of plasticizer diminished the tensile properties except elongation showing a slight increase. In all plasticized composites, organo-modified clay improved the tensile strength and at the same time, young's modulus and elongation almost remained constant. On the other hand, plasticized CA compounded with unmodified clay revealed lower properties. In a particular case, compounding of unplasticized CA with unmodified clay resulted in superior mechanical properties with a novel structure. So that, in optimum percentage –5 mass%- of unmodified clay, tensile strength and young's modulus increased significantly by 335% and 100%, to 178 MPa and 8.4 GPa, respectively. This is a dramatic improvement in strength and stiffness of CA. Adding organo-modified clay resulted in a little improvement in tensile properties. SEM pictures of the optimum composite showed a core/shell structure with high orientation in the shell part. It is supposed that this behaviour is caused by the interaction between CA hydroxyl groups and free cations existing in the galleries of unmodified clay.     

Fabrication of Single Wall Carbon Nanotubes-Based Poly(vinyl butyral) Nanocomposites with Enhanced Mechanical and Thermal Properties

In this research, poly(vinyl butyral) (PVB)/single wall carbon nanotubes (SWCNT) composites were prepared via solution blending method. Dispersion degree of SWCNT in the composites was characterized by Scanning Electron Microscopy (SEM) and mechanical properties were measured with tensile testing. Thermal degradation of composites was investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). SEM analysis confirmed good dispersion of the nanotubes in the PVB. The tensile tests showed significant increases in mechanical properties such as exceptional improvement in tensile strength, Young's modulus and flexibility for the composites compared to PVB at low SWCNT content.The TGA curves indicated that adding SWCNT improved the thermal stability of the PVB significantly and the degradation of the polymer matrix shifted to the higher temperatures. For the sample containing 0.6 wt%, an increase of 171% in modulus and a 258.4% enhancement of tensile strength were achieved. Also, elongation at break increased 28.7% at this loading. In fact, intrinsic properties of nanotubes caused enhancement of strength and flexibility simultaneously. Also, for this composite, T_onset and T_max enhanced remarkably and weight loss reduced greatly and residue at 600°C increased to high values. These results are promising for application of the PVB in industry.     

Mechanical properties and morphology for polypropylene composites filled with microencapsulated red phosphorus

The effects of the microencapsulated red phosphorus (MRP) content and specimen thickness on the mechanical properties of the filled polypropylene (PP) composites were studied at room temperature. The results showed that the influence of the MRP on the tensile and impact properties of the composites was significant, and the Young's modulus and impact strength of the composites increased nonlinearly while the tensile strength decreased slightly with increasing the MRP weight fraction; the tensile elongation at break increased outstandingly when the MRP weight fraction was less than 2% and then decreased with increasing the MRP weight fraction. Furthermore, the impact fracture surface was examined by scanning electronic microscope. The results suggested that the toughening effect was attributed to the absorption of impact fracture energy by the microencapsulated layer. Copyright © 2014 John Wiley & Sons, Ltd.     

Tensile and flexural properties of polypropylene composites filled with highly effective flame retardant magnesium hydroxide

The reinforcing effects of highly effective flame retardant magnesium hydroxide (FMX) content on the tensile and flexural properties of filled polypropylene (PP) composites were investigated within the FMX weight fraction range from 5 to 60 wt%. It was found that the Young's modulus and flexural modulus increased approximately linearly while the tensile yield strength and tensile fracture strength decreased slightly with increasing the FMX weight fraction. When the FMX weight fraction was lower than 20%, the tensile elongation at break decreased considerably, and then decreased slightly; the flexural strength increased when the FMX weight fraction was lower than 30%, and then decreased slightly. The tensile properties increased with increasing rate of tension. Moreover, the tensile yield strength of the composites was estimated using an equation proposed in previous work, and good agreement was shown between the predicted and the measured data.     

Mechanical,thermal and morphological properties of poly(ε‐caprolactone)/zein blends

Blends of poly(ε‐caprolactone) (PCL) with zein (PCL/zein) in different proportions (100/0, 75/25, 50/50, 25/75 and 0/100 wt% containing 5 wt% glycerol) were compared based on their mechanical properties (tensile strength, elongation at break, and Young's modulus), and on their thermal properties, the latter determined by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The morphology of the materials was studied by scanning electron microscopy (SEM). Blends of PCL/zein showed reduced tensile strength and elongation at break, but increased Young's modulus compared to the pure polymers, in agreement with the DMTA and SEM results. These findings indicated that PCL and zein were incompatible. TGA showed that the thermal stability was enhanced by the addition of zein to PCL, whereas SEM showed a poor interfacial interaction between the polymers. Copyright © 2004 John Wiley & Sons, Ltd.     

EFFECT OF PROCESSING METHOD ON THE IMPACT STRENGTH OF POM/TPU/CaCO3 TERNARY COMPOSITES

Polyoxymethylene （POM）/elastomer/filler ternary composites were prepared, in which thermoplastic polyurethane （TPU） and inorganic filler, namely, CaCO3, were used to achieve balanced mechanical properties of POM. The dispersion and phase morphology of POM/elastomer/filler composites were found to depend largely on processing method, CaCO3 content in masterbatch and the filler size. Two processing methods were employed to prepare POM/elastomer/filler ternary composites. One is called the one-step method, in which elastomer and the filler directly melt blended with POM matrix. The other is called the two-step method, in which the elastomer and the filler were mixed to get masterbatch first, which was then melt blended with pure POM of different content. The effect of phase morphology and processing method on impact strength was investigated. It was found that the two-step method results in an increase in impact strength but not for the one-step method. Additionally, the impact strength of POM ternary composites decreases with the increase in the size of CaCO3 particles.     

Toughening polylactide by dynamic vulcanization with castor oil and different types of diisocyanates

Dynamic vulcanization of polylactide (PLA) with castor oil (CO) and three different diisocyanates, namely 4,4′-diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), was performed to study the effect of diisocyanate type on the vulcanization process and on the morphology as well as mechanical properties of the PLA/CO-based polyurethane blends. The reactivity of the three diisocyanate followed the order of MDI > HDI > IPDI when reacting with castor oil. Interfacial compatibilization between PLA and the CO-based polyurethane occurred when the less reactive HDI and IPDI was used. Among all the blends, PLA/CO-IPDI showed the finest morphology and the best toughening efficiency. Incorporation of 20 wt% CO-IPDI increased the elongation at break and notched impact strength of PLA by 47.3 and 6.6 times, respectively. Cavitation induced matrix plastic deformation was observed as the toughening mechanism for the PLA blends with CO-based polyurethane. The effect of CO-IPDI content on the morphology and mechanical properties of PLA was studied in detail. The particle size of dispersed CO-IPDI and the elongation at break increased gradually, the tensile strength and Young's modulus decreased gradually, while the impact strength first increased and then decreased with increasing CO-IPDI content from 5 to 30 wt%. The maximum impact strength appeared for the blends with 20 wt% CO-IPDI.     

Synthesis and Characterization of Polyester-Based Nanocomposite

Recently, unsaturated polyester resin (UPR) and silica nanocomposite prepared by mechanical process is the one of the promising composite materials. In this study, the effects of silica as filler on mechanical, thermal, and morphological properties of unsaturated polyester-based composite were investigated. Mechanical properties such as tensile strength, elongation and Young's modulus increase with the addition of silica nanoparticle up to 1.0 wt%, and then decrease, over 1.0 wt%. Morphological surface of composite reveals that well-dispersed silica in the matrix occurred in low concentration. However, increasing of silica concentration causes aggregation of particles. Enhancement of mechanical properties strongly corresponds to strong adhession force of silica with the matrix and it influnced by well-disperse silica particles on the whole surface of composite. Thermal characterization and analysis of major functional group of the composites were also performed and described in this paper.     

Preparation and characterization of polyoxymethylene‐copolymer/hydroxyapatite nanocomposites for long‐term bone implants

In this work, new polyoxymethylene (POM)/hydroxyapatite (HAp) nanocomposites for long‐term bone implants have been obtained via extrusion and injection molding processes and characterized by differential scanning calorimetry (DSC), temperature‐modulated DSC (TMDSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide‐angle X‐ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and tensile mechanical and in vitro stability tests. Based on the DSC results, it was found that the degree of crystallinity increases for POM/0.5% HAp sample and decreases for POM/1.0% HAp and POM/2.5% HAp. SEM and TEM observations for POM/HAp nanocomposites indicated that the dispersion of HAp in the polymer matrix was uniform and the diameter of the HAp particles was less than 100 nm for most of them. Young's modulus increases with increasing HAp concentration, whereby elongation at break decreases. On the contrary, HAp concentration does not have a significant influence on the tensile strength. TG results show that for POM/0.5% HAp, POM/1.0% HAp, and POM/2.5% HAp, thermal stability slightly increases in comparison to pure POM, whereas for POM/5.0 HAp and POM/10.0% HAp, lower thermal stability was observed. In vitro data reveal that with an increase of HAp content, bioactivity of nanocomposites increases; a good in vitro chemical stability of POM and POM nanocomposites was confirmed. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation and cryogenic mechanical properties of epoxy resins modified by poly(ethersulfone)

A thermoplastic, poly(ethersulfone) (PES) was used to modify a bisphenol‐F based epoxy resin cured with an aromatic diamine. The initial mixtures before curing, prepared by melt mixing, were homogeneous. Scanning electron microscopy (SEM) micrographs of solvent‐etched fracture surfaces of the cured blends indicated that phase separation occurred after curing. The cryogenic mechanical behaviors of the epoxy resins were studied in terms of tensile properties and Charpy impact strength at cryogenic temperature (77 K) and compared to their corresponding behaviors at room temperature (RT). The addition of PES generally improved the tensile strength, elongation at break, and impact strength at both RT and 77 K except the RT tensile strength at 25 phr PES content. It was interesting to observe that and the maximum values of the tensile strength, elongation at break, and impact strength occurred at 20 phr PES content where a co‐continuous phase formed. Young's modulus decreased slightly with the increase of the PES content. Moreover, the tensile strength and Young's modulus at 77 K were higher than those at RT at the same composition, whereas the elongation at break and impact strength showed the opposite results. Finally, the differential scanning calorimetry analysis showed that the glass transition temperature (T_g) was enhanced by the addition of PES. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 612–624, 2008     

Investigation of sub‐micron size cenosphere fillers and filler loading on the mechanical and tribological peculiarity of polyester composites

This paper investigates the effect of sub‐micron size cenosphere filler and filler loading on mechanical and dry sliding wear property of polyester composites. Composites are fabricated by filling with 10 and 20 wt% of 800 and 200‐nm size of cenosphere filler particles. Neat polyester composite is also prepared for comparison analysis. Dry sliding wear test is conducted for these composites over a range of sliding distance with different sliding velocities and applied loads on a pin‐on‐disc wear test machine. Taguchi methodology and analysis of variance (ANOVA) is used to analyze the friction and wear characteristics of the composites. The artificial neural network (ANN) approach is implemented to the friction and wear data for corroboration. In this work, mechanical properties of composites such as hardness, tensile strength, tensile modulus, flexural strength, and compressive strength revealed that mechanical properties and wear resistance of the composites increase with a decrease in the particle size. The measured Young's moduli are comparable to standard theoretical prediction models. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand the dominant wear mechanisms. Finally, optimal factor settings are determined using a genetic algorithm (GA). Copyright © 2017 John Wiley & Sons, Ltd.     

Effects of Modified MMT on Mechanical Properties of EVA/MMT Nanocomposites and Their Foams

In this study, nanocomposites of poly(ethylene-co-vinyl acetate) with two kinds of organically modified montmorillonite (OMMT) were prepared by melt intercalation. Their structures and mechanical properties were characterized by X-ray diffraction (XRD) and tensile test respectively. Especially, foaming of these nanocomposites mixed with chemical blowing agent was carried out through compression molding. Influences of OMMT on foaming ratio and mechanical properties were investigated by density test, tensile test and tear test. Results revealed that both kinds of OMMT with proper content increased tensile strength and Young's modulus of nanocomposites without a compromise of elongation at break. For foaming, OMMTs apparently improved foaming ratio and in particular, one of them can improve tear strength, tensile strength, Young's modulus and elongation although the density was decreased.     

Evaluation of Mechanical Properties of Epoxy/Nanoclay/Multi-Walled Carbon Nanotube Nanocomposites using Taguchi Method

This paper reports the improvement of the mechanical properties of epoxy/nanoclay/multi-walled carbon nanotube (MWNT) nanocomposites prepared by the solution casting method for a range of pre-cure temperatures (room temperature, 50, and 70 °C), cure temperature (120, 130, and 140 °C), nanoclay content (0.5, 1.0, 1.5 wt%) and content of MWNT (0.2, 0.6, 1.0 wt%) for three levels. The influence of these parameters on the mechanical properties of epoxy/nanoclay/MWNT has been investigated using Taguchi's experimental design. The output measured responses are the tensile properties (tensile modulus, tensile strength and strain at break), impact strength and fracture toughness. From the Analysis of Mean (ANOM) and Analysis of Variance (ANOVA), MWNT content, pre-cure temperature and cure temperature had the most significant effects for the impact strength with contribution percentages of 38%, 28% and 23% respectively. However, for the fracture toughness and strain at break, the enhancements of properties come from the nanoclay content (59%), MWNT content (18%) and pre-cure temperature (23%). While the improvement in tensile strength was influenced by nanoclay and MWNT content, the cure temperature has a stronger effect on the tensile modulus. In this respect, Taguchi method points to the Taguchi method, in this way, points to the dominant parameters and gives the optimum parameter settings for each mechanical property. Confirmation experiments were performed with the optimum parameter settings and the mechanical properties were measured compared with the predicted results.     

Tailoring of interface of polypropylene/polystyrene/carbon nanofibre composites by polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene

Mechanical and physical properties of polypropylene (PP)/polystyrene (PS) blend, PP/PS/polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) ternary blend and their composites with carbon nanofibers (CNF) were investigated. Composites of ternary blend exhibited superior properties compared to those of binary blends. Mechanical performance of nanocomposites was intimately related to their phase morphology. PP/PS/SEBS/0.1 wt% CNF hybrid composites exhibited excellent impact strength (Four-fold increase compared to PP/PS blend) and ductility (12-fold increase in elongation at break, with respect to PP/PS blend). Moreover, these composites displayed good tensile strength and modulus (15% increase in Young's modulus, compared to PP/PS/SEBS blend) and are suitable for various end-use applications including automobile applications. Although crystallinity of PP phase is decreased by the incorporation of CNF, thermal stability of the composites remained almost unaffected. Contact angle measurements revealed that ternary composites exhibited maximum hydrophobicity.     

Fabrication of Bioactive Polyoxymethylene Nanocomposites for Bone Tissue Replacement

Summary: Stearic acid modified nano hydroxyapatite (n-SHA) filled polyoxymethylene (POM) nanocomposites were prepared by melt mixing method for bone tissue replacement and regeneration applications. Contact angle measurements of POM nanocomposites were carried out to understand the effect of n-SHA addition on the hydrophobicity of nanocomposites. The mechanical properties like tensile strength, Young's modulus and elongation at break were found to be increased significantly by the incorporation of n-SHA into the POM matrix. The bone-bonding ability of the nanocomposites was evaluated by examining the apatite formation on their surface after soaking in simulated body fluid (SBF) and apatite formation was studied by atomic force microscopy (AFM). The protein adhesion studies revealed the enhanced biocompatibility of the nanocomposites due to the presence of n-SHA nanofillers on the surface and it provides favorable binding sites for protein adsorption. The significant improvement in the biocompatibility as well as mechanical, thermal and hydrophobic properties of the POM nanocomposites makes it a potential future material for bone implantation.     

Morphology control of poly(lactic) acid/polypropylene blend composite by using silanized cellulose fibers extracted from coir fibers

The objective of this work is the use of cellulose fibers extracted from coir fibers as Janus nanocylinders to suppress the phase retraction and coalescence in poly(lactic) acid/polypropylene bio-blend polymers via prompting the selective localization of cellulose fibers at the interface using chemical modification. The untreated and modified cellulose fibers extracted from coir fibers using a silane molecule (tetraethoxysilane) were used as reinforcement and as Janus nanocylinder at two weight contents (2.5 wt% and 5 wt%) to manipulate the morphology of the bio-blends. Their bio-composites with PLA-PP matrix were prepared via melt compounding (at PLA/PP: 50/50). The treatment effect on component interaction and the bio-composites properties have been studied via Scanning electron microscopy, infrared spectroscopy, and differential calorimetry analysis. The mechanical and rheological properties of nanocomposites were similarly assessed. Young's modulus and tensile strength of PLA-PP nanocomposites reinforced by silanized cellulose fibers show a great enhancement as compared to a neat matrix. In particular, there was a gain of 18.5% in Young's modulus and 11.21% in tensile strength for silanized cellulose fiber-based bio-blend composites at 5 wt%. From the rheological point of view, it was found that the silanized cellulose fibers in PLA-PP at both fibers loading enhances the adhesion between both polymers leading to tuning their morphology from sea-island to the continuous structures with the appearance of PLA microfibrillar inside of bio-composites. This change was reflected in the relaxation of the chain mobility of the bio-blend composites.

     

Effects of flower-like ZnO nanowhiskers on the mechanical, thermal and antibacterial properties of waterborne polyurethane

A novel waterborne polyurethane/flower-like ZnO nanowhiskers (WPU/f-ZnO) composite with different f-ZnO content (0-4.0 wt%) was synthesized by an in-situ copolymerization process. The f-ZnO consisting of uniform nanorods was prepared via a simple hydrothermal method. In order to disperse and incorporate f-ZnO into WPU matrix, f-ZnO was modified with γ-aminopropyltriethoxysilane. Morphology of f-ZnO in WPU matrix was characterized by scanning electron microscope. The properties of WPU/f-ZnO composites such as mechanical strength, thermal stability as well as water swelling were strongly influenced by the f-ZnO contents. It was demonstrated that appropriate amount of f-ZnO with good dispersion in the WPU matrix significantly improved the performance of the composites. The mechanical property was enhanced with an increase of f-ZnO content up to the optimum content (1 wt%) and then declined. Incorporation of f-ZnO enhanced the water resistance of the composites remarkably. It was amazing to observe that the thermal degradation temperatures of the composites initially decreased significantly and then leveled off with content increase of f-ZnO, which was different from the results of other WPU composite systems reported. Antibacterial activity of WPU/f-ZnO composite films against Escherichia coli and Staphylococcus aureus was also tested. The results revealed that the antibacterial activity enhanced with the increasing f-ZnO content, and the best antibacterial activity was obtained at the loading level of 4.0 wt% f-ZnO.     

Water absorption and enzymatic degradation of poly(lactic acid)/rice starch composites

Poly(lactic acid) (PLA) composites consisting of PLA, rice starch (RS) (0–50 wt%) and epoxidised natural rubber (ENR50) were compounded by a twin-screw extruder and compression moulded into dumbbell specimens. Tensile tests were performed to characterize the mechanical properties of the PLA/RS composites. Morphological studies were done on the tensile fractured surface of the specimens by using scanning electron microscopy (SEM). Twenty weight percent of RS achieved a good balance of strength and stiffness. Beyond 20 wt% loading of RS, the tensile strength and elongation at break of PLA decreased drastically. This may be attributed to the agglomeration of RS, which could then act as stress concentrator. The incorporation of ENR50 increased the tensile strength and elongation at break of the PLA/RS composites remarkably, owing to the elastomeric behaviour and compatibilisation effects of ENR50. Interestingly, the morphology of PLA/RS composites transformed to a more ductile one with the addition of ENR. The kinetics of water absorption of the PLA/RS composites conforms to Fick's law. The M_m and D values are dependent on the RS and ENR concentrations. The tensile properties of the PLA/RS composites deteriorated after water absorption. The retention-ability and recoverability of the PLA/RS composites are relatively low, attributed to the hydrolysis of PLA, degradation of the PLA–RS interface and leaching of the RS particles. In addition, the tensile properties of PLA/RS composites decreased drastically upon exposure to enzymatic degradation. Extensive pinhole and surface erosion on the PLA/RS composites indicate high degree of hydrolysis. Whilst the addition of ENR leads to some improvements in tensile properties, nevertheless, it enhanced the biodegradability of the PLA/RS composites when exposed to water and -amylase enzymatic treatments.