Improvement in mechanical properties of aluminum polypropylene composite fiber

Aluminum particles (Al) were added to polypropylene (PP) in the presence of poly ethylene glycol (PEG) and polypropylene-graft-maleic anhydride to produce composites. The composites were then melt-spun into a mono filament and tested for tensile properties, diameter evenness and morphology. Melt rheological properties of Al/PP composites were studied in linear viscoelastic response regions. It was observed that level of dispersion of aluminum particles within a polypropylene composite fiber could be improved by incorporating polyethylene glycol. The improvement of dispersion led to an improvement in the fibers mechanical properties through a reduction of the coefficient of variation of fiber diameter.     

Warpage and mechanical properties of film insert molded parts with composite substrate

Mechanical properties of chopped carbon fiber (CF) reinforced PC/ABS composites were investigated. Tensile strength and elastic modulus of the composites were enhanced with increasing CF contents. On the contrary, impact strength of the composite was decreased with increasing CF fraction. Film insert molding was introduced in order to improve impact strength. Film insert molded composite specimens have higher impact strength than conventional injection molded composite specimens because inserted film acted as a cushion to absorb the impact energy. Large warpage which was observed after molding and known as a disadvantage of the film insert molded part can be prevented by controlling the amount of filled CFs. Therefore, fiber reinforcement and film insert molding can be applied simultaneously to reduce warpage of the film insert molded part and enhance impact strength of the CF reinforced composite.     

Study on mechanical and thermal properties of fiber-reinforced Epoxy/Hybrid-silica composite

Recently, carbon fiber composites have been widely used as structural reinforcement materials of buildings, replacing reinforcing bars or concrete. And the increase in use of super fibers such as aramid and high strength PE, which is aimed at improving the reinforcement properties, has resulted in a demand for a resin system with excellent mechanical and thermal properties. In this research, a fiber-reinforced composite has been produced by using the super fibers such as carbon fiber or aramid fiber, reinforcement resin and the silica hybrid compound containing epoxy group. This study was carried out to confirm the effect of the silica hybrid on mechanical properties, heat resistance and adhesion strength of a fiber-reinforced epoxy composite, which was produced by blending silica or introducing silica hybrid through covalent bonds. And the silica hybrid containing epoxy group, which may be introduced to the structure of fiber-reinforced epoxy composite through covalent bonds caused by reaction with a hardener, has been used, so that the heat resistance and adhesion strength could be improved.     

Effects of drawing speed and water on microstructure and mechanical properties of artificially spun spider dragline silk

The effects of drawing speed and water on the microstructures and mechanical properties of Araneus Ventricosus spider dragline silk were investigated with polarized Raman spectroscopy and mechanical property tester. The major ampullate silk (MAS), spider dragline silk was made by drawing from major ampullate glands of Araneus Ventricosus spider at the rates of 1, 10, 20, 40, and 110 mm/s, respectively. It was found that MAS silk drawn at 20 mm/s contained the most of β-sheet polypeptides with the high orientation and the least of α-helix. The results also revealed that dragline silk spun at aqueous condition (WDS) had lower content and orientation of β-sheets than those at ambient condition (DDS); the existence of water led to smaller tensile strength at break and initial modulus, but larger tensile strain at break of dragline silk.     

Prediction of mechanical properties of aging B.mori silk fabric based on grey neural network model

This paper presents a grey neural network model for the prediction of mechanical properties of aging B.mori silk fabric. In the experiment, we obtained outdoor natural aging breaking strength of B.mori silk fabric from 8 samples. Then, a grey neural network GNNM (1,1) model is proposed by the means of combining GM (1,1) model with BP artificial neural network to predict mechanical properties of B.mori silk fabric. At the same time, this paper analyzed and compared the GM (1,1) model and GNNM (1,1) model by using prediction error such as the relative percentage error (RPE) and the root mean square error (RMSE). The experimental results show that the RMSE of GNNM (1,1) model is 0.0284 well below 6.1786, which is the RMSE of GM (1,1) model. It indicates the GNNM (1,1) model were better than the normal grey GM (1,1) model, when taken the prediction error as evaluation parameter.     

Manufacturing technique and mechanical properties of polylactide acid net/chitosan composite membrane

Guided tissue regeneration is an important treatment for periodontal diseases, as it helps periodontal tissues to regenerate. This study aims to evaluate the influence of different procedures for gelation on the mechanical properties of low melting-point polylactic acid (LPLA) net/chitosan composite membranes. After immersion in a chitosan solution, LPLA nets undergo different steps of gelation and freeze-drying, forming the porous LPLA/Chitosan composite membranes. The tensile strength, swelling, degradation and water content of the resulting membranes are then evaluated. According to the experimental results, different sequences for gelation influence the tensile strength and swelling ratio, but do not significantly influence the water content ratio and contact angle.     

Optimization of molecular structure of polythiophene-graft-PMMA for effective compatibilization of SAN/MWCNT composite with superior mechanical properties

A new compatibilizer, P3HT-g-PMMA with controlled graft density and degree of polymerization of PMMA graft, has been synthesized for preparation of poly(styrene-co-acrylonitrile) (SAN)/multi-walled carbon nanotube (MWCNT) composites with superior mechanical properties. Fluorescence emission and Raman spectra reveal that the π-π interaction between polythiophene backbone of the compatibilizer and the surface of MWCNT is more effective as the graft density of PMMA in the compatibilizer is decreased while the degree of polymerization of PMMA is increased. Since FE-SEM observation also shows that the use of compatibilizer with higher degree of polymerization of PMMA graft yields well-dispersed MWCNTs in composites, it is concluded that the compatibilizer with lower graft density and higher degree of polymerization of PMMA graft is the most effective for reinforcing SAN with MWCNT.     

Enhanced mechanical and thermal properties of carbon fiber composites with polyamide and thermoplastic polyurethane blends

In this article, we demonstrated the preparation of carbon-fiber-reinforced composites using a polyamide 6 (PA6)/thermoplastic polyurethane (TPU) blend, in which the addition of TPU resulted in superior mechanical performances and increased thermal stability. According to various characterization techniques, these results are attributed to an enhanced adhesion and a homogeneous dispersion of long-carbon-fibers (LCFs) with TPU sizing in blended polymer matrix. Above all, dynamic-mechanical thermal analysis (DMTA) measurements clearly show that the dynamic storage modulus (E') of the blend composites is increased by threefold with temperature ranges below and above the glass transition temperature. The presence of LCFs in TPU systems induces effective fiber orientation, exhibiting simultaneous improvements in the tensile strength, flexural strength, and thermal stability.     

Structure and properties of silk fibroin modified cotton

In this research, a novel cotton fiber with a silk fibroin (SF) coating was prepared by the oxidation of a cotton thread with sodium periodate and subsequent treatment in a solution of silk fibroin. The structures of both the oxidized cotton samples and the SF modified cotton samples were investigated by Fourier transform infrared (FT-IR) in combination with X-ray photoelectron spectroscopy (XPS) analysis. Other performances such as surface morphology and breaking strength were also studied. The results indicated that the weight of the oxidized cotton samples increased during SF treatment, while that of the un-oxidized cotton (pure cotton) samples reduced after SF treatment. Compared with the pure cotton samples, the oxidized cotton clearly showed a characteristic absorption band at 1730 cm⁻¹ due to the stretching vibration of the C=O double bond of the aldehyde group. After being treated with the SF solution, the oxidized cotton fiber showed a weakened characteristic absorption band at 1730 cm⁻¹ and a new absorption band at round 1540 cm⁻¹, suggesting the formation of C-N bond between aldehyde groups in the oxidized cotton and primary amines in the silk fibroin. The results were also confirmed by XPS analysis. Compared with the oxidized cotton samples, the SF treated cottons had relatively smooth surfaces, similar breaking strength, and the improved wrinkle recovery angles. The results in this research suggest that cotton based materials with protein coating can be achieved without using any other crosslinking agents by the method introduced.     

Enhanced mechanical and thermal properties of hybrid graphene nanoplatelets/multiwall carbon nanotubes reinforced polyethylene terephthalate nanocomposites

The effects of graphene nanoplatelets (GNP) and multiwall carbon nanotube (MWCNT) hybrid nanofillers on the mechanical and thermal properties of reinforced polyethylene terephthalate (PET) have been investigated. The nanocomposites were melt blended using the counter rotating twin screw extruder followed by injection molding. Their morphology, mechanical and thermal properties were characterized. Combination of the two nanofillers in composites formulation supplemented each other which resulted in the overall improvement in adhesion between fillers and matrix. The mechanical properties and thermal stability of the hybrid nanocomposites (PET/GNP1.5/MWCNT1.5) were significantly improved compared to PET/GNP3 and PET/MWCNT3 single filer nanocomposites. However, it was observed that GNP was better in improving the mechanical properties but MWCNT resulted in higher thermal stability of Nanocomposite. The transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed uniform dispersion of the hybrid fillers in PET/GNP1.5/MWCNT1.5 nanocomposites while agglomeration was observed at higher filler content. The MWCNT prevented the phenomenal stacking of the GNPs by forming a bridge between adjacent GNP planes resulting in higher dispersion of fillers. This complimentary geometrical structure is responsible for the significant improvement in the thermal stability and mechanical properties of the hybrid nanocomposites.     

Enhanced mechanical and dielectric properties of poly(vinylidene fluoride)/polyurethane/multi-walled carbon nanotube nanocomposites

Multi-walled carbon nanotubes (MWNTs) nanocomposites with the polymer matrix composed of blends of poly(vinylidene fluoride) (PVDF) and polyurethane (PU) were prepared via functionalization of 3,4,5-triflouroaniline (TFA) on MWNTs. The MWNTs/polymer nanocomposites showed a dominantly enhanced elongation due to incorporation of PU molecules in PVDF matrix and the improved MWNTs dispersion in the polymer matrix resulting from functionalization of MWNTs with TFA. The functionalization of TFA on MWNTs was confirmed by the measurements of Raman, FT-IR spectra, SEM, and TEM images. In addition, the dielectric constant of nanocomposites increased with an increase of TFA-functionalized MWNTs in PVDF/PU/MWNTs nanocomposites. The polymer blend nanocomposites incorporating MWNTs may be available as an alternative potential route for the actuator materials.     

Flame retardancy,Thermal and mechanical properties of Kenaf fiber reinforced Unsaturated polyester/Phenolic composite

Unsaturated polyester (UP) resin has been blended with phenolic resin (PF) resole type at various ratios to obtain a homogeneous blend with improved flame resistance compared to its parent polymers. The polymer blend was reinforced with 20 wt% kenaf using hand lay out technique. Fourier transform infrared spectroscopy (FT-IR) was used to characterize changes in the chemical structure of the synthesized composites. The thermal properties of the composites were investigated using thermogravimetric analysis (TGA). The thermal stability of UP/PF kenaf composites co-varies with the PF content, as shown by the degradation temperature at 50 % weight loss. The char yield of the composites increases linearly with PF content as shown by the TGA results. The flammability properties of the composites were determined using the limiting oxygen index (LOI) and UL-94 fire tests. The LOI increased with the PF content while the composites exhibit improved flame retardancy as demonstrated by UL-94 test. The mechanical and morphological properties of the composites were determined by tensile test and scanning electron microscopy (SEM), respectively. The tensile strength and the Young’s modulus of the blend/composites slightly decreased with increasing PF content albeit higher than PF/kenaf fiber composites.     

Effects of wet-spinning conditions on structures,mechanical and electrical properties of multi-walled carbon nanotube composite fibers

A series of composite fibers composed of multi-walled carbon nanotube (MWCNT) and poly(vinyl alcohol) (PVA) are prepared by varying co-flowing wet-spinning conditions such as spinning geometry and PVA concentration, which affect aligning shear stress for MWCNTs during the wet-spinning. Then, structural features, mechanical and electrical performances of MWCNT/PVA composite fibers are investigated as a function of the aligning shear stress of the wet-spinning process. SEM images of the composite fibers exhibit that MWCNTs are wetted effectively with PVA chains. Polarized Raman spectra confirm that the alignment of MWCNTs is enhanced along the composite fiber axis with increasing the aligning shear stress of the spinning process. Accordingly, initial moduli and tensile strengths of the composite fibers are significantly increased with the increment of the aligning shear stress. In addition, it is found that electrical conductivities of MWCNT/PVA composite fibers increase slightly with the aligning shear stress, which is associated with the formation of efficient electrical conduction paths caused by well-aligned MWCNTs along the composite fiber axis.     

Protective rigid fiber-reinforced polyurethane foam composite boards: Sound absorption,drop-weight impact and mechanical properties

Polyurethane foam has been develocped for years. In the past, the most study is focused on one function of Polyurethane foam including noise absorption, thermal protection, and mechanical impact as well as cushioning properties, and thus interdisciplinary functions of these foam boards become an innovation research. Therefore, the objective of study is to develop the multifunctional protective composite boards which are suitable for diversified environments. In this study, the carbon fibers (CF) and glass fibers (GF) are used as reinforcements for PU composite boards which are denoted as CFR-PU and GFR-PU respectively. The composite boards are made with different thickness and different contents of reinforcing fibers. The drop-weight impact test adopts a circular drop weight that falls from a certain height in order to observe the deformation mechanism of the boards. Different fracture modes that are caused by the bursting, compression, drop-weight impact, and puncture resistance tests are then examined. The test results indicate that the CFR-PU and GFR-PU fiberreinforced composite boards have a satisfactory impact load of 90 % and a favorable absorption coefficient at a certain frequency, and also have improved mechanical properties.     

Preparation and properties of Nano-TiO2 photo-catalytic silk respirator paper

In order to obtain paper respirator with dust resistance performance and antibacterial property, silk photo-catalytic respirator paper was made by loading nano-TiO₂ photo-catalyst on silk based respirator paper. The pore structure, surface topography and TiO₂ distribution, and the filtration performance of silk respirator paper were studied by using a pore size meter (PSM), a field emission scanning electron microscope (FESEM), and a filter tester, respectively. In addition, the antibacterial property of silk respirator paper was also investigated. The results showed that the pore structure and filtration performance of silk respirator paper could be controlled by changing the degree of beating of silk pulp and the basis weight of silk paper. Silk respirator paper of 45 g/m² made from silk pulp having beating degree of 85 ^oSR had high filtration efficiency and appropriate filtration resistance. Nano-TiO₂ particles were mainly attached to the surface of silk paper, and the loading of nano-TiO₂ photo-catalyst resulted in a slight decrease in filtration resistance and filtration efficiency of silk respirator paper. It, however, improved the antibacterial property of silk respirator paper effectively.     

Buckling analysis of laminated composite plates submitted to compression after impact

The aim of this work is the experimental evaluation of the residual strength of composite laminates under compression after low velocity impact. Different kinds of delaminations, partial, embedded and through-the-width, were studied. Carbon-fibre reinforced epoxy composite was used and the experimental tests were performed on [0]₁₆, [0, 90, 0, 90]_2S and [0_i, 90_i]_s with i=2, 3, 4, 5, using a drop-weight-testing machine. The impacted plates were inspected by the ultrasonic C-Scan to evaluate the size and the shape of the delamination. Results show that the presence of delamination decreases the compressive strength. The stacking sequence and laminate thickness were verified to have a remarkable influence on the value of the residual compressive strength, and play an important role on the observed buckling failure modes.     

Effect of silk protein fibers on properties of thermoplastic rice starch

Biodegradable polymer was prepared as thermoplastic starch (TPS). Due to poor mechanical properties and high water absorption of TPS, thermoplastic rice starch (TPRS) was modified by reinforcing with natural silk protein fibers, as an alternative choice of fiber reinforcement. Different contents and lengths of silk fibers were varied and used as the reinforcement. Internal mixer and compression molding machine were used to mix and shaped the TPRS/silk composites. It was found that stress at maximum load and Young??s modulus of the TPRS/silk composites significantly increased with the incorporation of silk fibers. Water absorption of the TPRS/silk composites was also dropped by the addition of silk fibers. Moreover, thermal degradation temperatures of the TPRS/silk composites shifted to higher temperatures by the inclusion of the silk fibers. Functional group analysis and X-ray diffraction patterns were analyzed by FI-IR and XRD techniques, respectively. Furthermore, color measurement, morphology and biodegradation by soil burial test were carried out for different TPRS/silk composites.     

Dye-resist properties of reactive dye-resist agents in acid dyeing of silk

The dye-resist effect of reactive dye-resist agents in acid dyeing of silk was investigated. The dye-resist agent containing dichlorotriazine achieved a higher resist effectiveness than others since they make a charge barrier against diffusion in the silk fiber periphery due to the high reactivity of dichlorotriazine group. Especially, the increase in the number of ionic groups in acid dyes leads to better electrostatic repulsion of reactive dye resist agent treated silk and thus improves the resist effectiveness. However, the hydrophobicity effect of acid dyes on the dye-resist properties was relatively minor.     

Antibacterial properties and color fastness of silk fabric dyed with turmeric extract

The use of non-toxic and eco-friendly natural dyes on textiles has received much attention due to the increased environmental awareness in order to avoid some hazardous synthetic dyes. In the present study, an eco-friendly approach was developed to impart color and antibacterial properties to silk fabrics dyed with turmeric extract as a non-toxic natural colorant. The natural colorant was extracted from Curcuma Longa rhizome. Copper sulfate, ferrous sulfate and potassium aluminium sulfate were applied in a pre-metallization process as mordanting agents. Antibacterial properties of treated fabrics were evaluated against common pathogenic bacteria, Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). The effects of dye concentration and mordant types on the obtained color hues, antibacterial efficiency and color fastness of the fabrics were investigated. The results indicated that mordanted and dyed fabrics possessed desirable antibacterial properties. Complete antibacterial activity of the treated fabrics was obtained with 3 %owf (on weight of the fabric) copper sulfate. It was also shown that increasing the dye concentration could lead to a more efficient antibacterial activity on the mordanted dyed fabrics. An optimum level of the antibacterial activity was observed in the sample treated with 30 %owf of turmeric. Furthermore, the results of CIE L*, a*, b* values, FTIR, washing, light and rubbing fastnesses of the dyed fabrics were reported. The mordanted dyed silk fabrics exhibited desirable color fastness properties. These studies proved a direct relationship between the degree of antibacterial activity of the fabrics treated with turmeric and the metals ion concentration.     

Preparation of poly(acrylonitrile)-grafted silk fibers with antibacterial properties

This study is focused on investigating the feasibility of using silver(I) ions loaded poly(acrylonitrile)-grafted silk fibers as antibacterial dressing material. The optimum grafting conditions for ceric ammonium nitrate induced graft-copolymerization of acrylonitrile onto silk fibers were found to include initiator concentration of 35 mM, catalyst HNO₃ concentration of 0.40 M and initiation time of 10 min. The poly(acrylonitrile)-grafted silk fibers were loaded with silver(I) ions by equilibration method. The resulting fibers were investigated for their biocidal action against E. coli, by using zone inhibition and colonies counting method.