Fabrication and characterization of mechano-modulated PET/BPU nanofibrous mats as potential vascular grafts materials

Polyethylene terephthalate (PET)/biomedical polyurethane (BPU) composite nanofibers with modulated mechanical properties are electrospun by varying the weight ratios of PET and BPU polymers in the mixture. The effect of BPU content on the morphology, porosity, thermal properties, and crystalline structures are systematically investigated. It is shown that uniform PET/BPU nanofibers can be formed through optimization. When the content of BPU is low (0?C7 %), better elongation of the nanofibrous mats is obtained with the increase of BPU content, whereas further increasing the BPU polymer (up to 15 %) results in a decreased breaking elongation as well as the mechanical strength of composites. The formed nanofibrous mats may find potential applications in tissue engineering and vascular graft.     

Synthesis and characterization of novel self-colored PET (polyethylene terephthalate) by step-growth polymerization containing dye based on 1,8-naphthalimide group

A novel self-colored polyethylene terephthalate (PET) was synthesized using a synthesized dye, 4-amino-N-propanoic acid-1,8-naphthalimide. For this purpose, the prepared naphthalimide dye was added upon the polycondensation step and then a self-colored PET was prepared by step-growth polymerization. The characterization of synthesized self-colored PET and naphthalimide dye were carried out using TLC, FTIR, ¹HNMR, DSC, UV-visible and Fluorometery. Results indicated that, the novel fluorescent yellow-green PET with appropriate properties was obtained. The glass transition temperature of self-colored PET was 70 °C and it was measured by differential scanning calorimeter, which revealed that addition of dye to the chains of polymer did not affect the context of glass transition of polymer. UV-visible spectrum indicated that, 99 percent of dye was incorporated in polymer chains chemically. Furthermore, the intrinsic viscosity of self-colored PET was 0.556 dl/g and molecular weight of polymer was around 35000 (g/mol) and measured using the viscometer technique.     

Woven Kenaf/Kevlar Hybrid Yarn as potential fiber reinforced for anti-ballistic composite material

Woven Kenaf/Kevlar Hybrid Yarn is the combination of natural and synthetic fibers in the form of thread or yarn. The yarn is weaved to form a fabric type of fiber reinforced material. Then, the fabric is fabricated with epoxy as the resin to form a hybrid composite. For composite fabrication, woven fabric Kenaf/Kevlar hybrid yarn composite was prepared with vacuum bagging hand lay-up method. Woven fabric Kenaf/Kevlar hybrid yarn composite was fabricated with total fiber content of 40 % and 60 % of Epoxy as the matrix. The fiber ratios of Kenaf/Kevlar hybrid yarn were varied in weight fraction of 30/70, 50/50 and 70/30 respectively. The composites of woven fabric Kenaf/Epoxy and woven fabric Kevlar/Epoxy were also fabricated for comparison. The mechanical properties of five (5) samples composites were tested accordingly. Result has shown that of value of strength and modulus woven fabric Kenaf/Kevlar Hybrid Yarn composite was increased when the Kevlar fiber content increased. Therefore, among the hybrid composite samples result showed the woven fabric Kenaf/Kevlar Hybrid Yarn composites with the composition of 30/70 ratio has exhibited the highest energy absorption with 148.8 J which 28 % lower than Kevlar 100 % sample. The finding indicated there is a potential combination of natural fiber with synthetic fiber that can be fabricated as the composite material for the application of high performance product.     

Studies on the ternary blends of liquid crystalline polymer and polyesters

Thermotropic liquid crystalline polymer made up of poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate) (PET) 8/2 copolyester, poly(ethylene 2,6-naphthalate) (PEN) and PET were mechanically blended to pursue the liquid crystalline phase of ternary blends. Complex viscosities of blends decreased with increasing temperature and PHB content. DSC thermal analysis indicated that glass transition temperature (Tg) and melting temperature (Tm) of blends increased with increasing PHB content. Both tensile strength and initial modulus increased with raising PHB content and take-up speed of monofilaments. In the WAXS diagram, only PEN crystal reflection at 2Θ=15.5^o appeared but PET crystal reflection was not shown in all compositions. The degree of transesterification and randomness of blends increased with blending time but sequential length of both PEN and PET segment decreased.     

Dynamic mechanical analysis of randomly oriented short bagasse/coir hybrid fibre-reinforced epoxy novolac composites

Hybrid composites of epoxy novolac reinforced with short bagasse fibres and short coir fibres were prepared. The mechanical and dynamic mechanical properties of these bagasse-coir hybrid fibres reinforced epoxy novolac composites were investigated with reference to different layering patterns of the composites. The tensile properties of the tri-layer composites are recorded higher than those of the bi-layer composites, whereas the flexural properties of the tri-layer composites are lower than bi-layer composites. The tensile strength of the intimate mix composite is comparable with trilayer composite having bagasse as skin material. The effect of layering pattern on storage modulus (E′), damping behavior (tan δ), and loss modulus (E″) was studied as a function of temperature and frequency. The E′ values of the bi-layer composites are recorded lower than those of tri-layer (bagasse/coir/bagasse) and intimately mixed hybrid composites. The minimum E′ value is obtained for the composites made with coir as skin layer. Bi-layer composite shows maximum damping property. The theoretical modeling showed good correlation with experimental results at above glass transition temperature (T _g ), while theoretical model deviates experimental data at lower T _g . The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites.     

Mechanical properties,morphology and dynamic mechanical properties of LGF/TPU/SAN composites

A series of the long glass fiber reinforced thermoplastic polyurethane elastomers and poly (styrene-acrylonitrile) (LGF/TPU/SAN) composites with different contents of long glass fiber were prepared by using self-designed impregnation device. Dynamic mechanical properties of TPU/SAN matrix reinforced with 10, 20 and 30 % by weight long glass fibers have been investigated by using dynamic mechanical thermal analysis (DMA). The results indicated that the content of long glass fiber and scanning frequency had some influence on dynamic mechanical properties and glass transition of LGF/TPU/SAN composites. In addition, the Arrhenius relationship has been used to calculate the activation energy of a-transition of the LGF/TPU/SAN composites. SEM demonstrates the relatively good dispersion of the long glass fiber in the TPU/SAN matrix. In addition, Effects of the content of long glass fiber on mechanical properties of the LGF/TPU/SAN composites are investigated.     

Long term performance study of glass reinforced composites with different resins under marine environment

For marine structural applications which poses significant challenges to the choice of materials due to presence of corrosive seawater, polymer matrix based fiber reinforced composites are increasingly becoming the material of choice. However the performance properties of composites are greatly influenced by the moisture absorbed by the composite. In the current study, the long term performance is assessed by determining the amount of moisture absorbed and the reduction of mechanical properties over 12 months in a simulated sea-water environment at different temperatures. Three commonly used thermoset resins with different chemistry such as unsaturated polyester (USP), epoxy resin (EP) and vinylester (VE) are chosen. The effect of fiber reinforcement on the long term performance is investigated. A suitable method for manufacturing glass reinforced composite with good interfacial bonding and high volume fraction is also developed in current study. It is observed that vinylester plaques and composites absorb lesser moisture compared to USP and Epoxy systems resulting in lesser reduction in flexural strength and making the best performing among polymers studied. It is also found that sea-water diffusion into the composite follows non-Fickian behaviour and diffusion relaxation model fits well with the experimental data and corresponding model parameters are evaluated.     

Bending properties of carbon/glass and carbon/aramid fabric composites with various stacking structures by the VARTM method

In this paper, the bending properties of woven carbon/glass and carbon/aramid fabric-reinforced polymer laminates is studied using a combination of experimental analysis and fracture observation. Six types of each hybrid composite were manufactured by lamination of the carbon/aramid fabric and carbon/glass fabric using VARTM. Bending behaviors were fundamentally evaluated for the six types of monolithic composites laminated by the same fabric. The objective was to achieve a good bending strength by effective combination of composite structures using limited amounts of a raw material. It was shown that the bending property was different, depending on the type of fiber, lamination structure, and the number of layers.     

Effects of cross-linking on mechanical and physical properties of agricultural residues/recycled thermoplastics composites

Maleated graft polyolefins as cross-linking agents (CAs) are widely used to improve properties of wood thermoplastic composites made by melt extrusion process. In this study, novel CAs, free isocyanate group (NCO)-terminated urethane pre-polymers (UPs) were synthesized and used in manufacturing wheat straw (WS)/recycled polyethylene (PE) composites. The composites using polymeric diphenylmethane diisocyanate (pMDI) as a CA were also made in comparison. The relationship between composite properties and the level of CA and its content as well as the composite density and hot pressing time were investigated based on wood based board processes. The results show that the internal bonding (IB) strength, the IB after soaked in boiling water for 2 h (2hWIB), the modulus of rupture (MOR), the modulus of elasticity (MOE) and the 24 h thickness of swell after absorption of water (24hTS) of the composites are significantly improved with increased CA contents and composite densities. The optimal hot pressing time is 1.1 min/mm at 180°C. The cross-linking function is attributed to the reaction between free NCOs of CA molecules with hydroxyls of WS and the moisture in the raw materials, as well as the interaction between weak polar chain segments in the CA molecules to the non-polar PE. It is highly feasible to manufacture high quality composite using WS and recycled PE as raw materials when cross-linked with just 2.5% of UPs.     

Acid-sensitivity and physical properties of polymethylmethacrylate and polyurethane films containing polymeric styryl dye

Solution-cast films of polymethylmethacrylate (PMMA) and polyurethane (PU) containing polymeric styryl dye up to 5% by weight were prepared to investigate their acid-sensitivity and mechanical and thermal properties. Original red samples due to styryl dye turned out yellow very rapidly as they were exposed to acid vapor of hydrochloric acid or p-toluenesulfonic acid. According to UV/VIS spectroscopic measurements, characteristic peak intensities near 430 nm and 520 nm increased or decreased relatively with exposed amounts of acid, respectively. Both PMMA and PU samples showed uniform color distribution due to a good miscibility between polymer and dye which can be evidenced by measurements of glass transition temperature. No significant difference in acid-sensitivity was found between PU and PMMA except relative absorbance. However, dependence of their mechanical properties on dye content was somewhat different with PU or PMMA. In case of PMMA, modulus and breaking stress increased up to about 50% with increasing dye content, whereas those of PU samples showed only slight increase. It was ascribed to whether the matrix polymer was in the glassy or rubbery state.     

Conductive polymer-coated threads as electrical interconnects in e-textiles

An organic polymer electrical interconnect is demonstrated. The ionomer mixture poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS; 1:2.5, w:w) was cast onto silk fibers from a 50:50 (v:v) ethylene glycol solution by a dip-coating process. Dynamic mechanical analysis (DMA) results show that Young’s modulus and mechanical strength are maintained during the coating process from acidic solution (pH ∼1). DMA dynamic temperature scans reveal two new thermal transitions once PEDOT:PSS is applied to the silk fiber, and they are assigned to the glass transition temperature (59 °C) and melting point (146 °C) of the ionomer pair. Electrical conductivities of 8.5 S/cm were achieved with four cycles of the dip-coating process, only 10x less than Ag-coated thread control samples. SEM imaging of the PEDOT:PSS-coated fibers show slight texturing to the fibers due to the coating, as well as significant charging in the uncoated samples when compared to PEDOT:PSS-coated samples. The conductive fibers fabricated by this process were successfully applied as electrical interconnects in flexible, fully functional 555 timer circuits stitched into fabric substrates.     

Hybrid effect in the mechanical properties of jute/rockwool hybrid fibres reinforced phenol formaldehyde composites

This research work was concerned with the evaluation of the effect of fibre content on the mechanical properties of composites. Composites were fabricated using jute/phenol formaldehyde (PF), rockwool/PF, and jute/rockwool hybrid PF with varying fibre loadings. Jute and rockwool fibre reinforced PF composites were fabricated with varying fibre loadings (16, 25, 34, 42, 50, and 60 vol.%). The jute/rockwool hybrid PF composites were manufactured at various ratios of jute/rockwool fibres such as 1:0, 0.92:0.08, 0.82:0.18, 0.70:0.30, 0.54:0.46, 0.28:0.72, and 0:1. Total fibre content of the hybrid composites was 42 vol.%. The results showed that tensile strength of the composite increased with increasing fibre content up to 42 vol.% over which it decreased for jute and rockwool fibre reinforced PF composites. Flexural strength of the composite was noted to peak at a fibre loading of 42 vol.% for jute/PF composites, and 34 vol.% for rockwool/PF composites. Impact strength of jute/PF composites increased with increasing fibre loading but that of rockwool/PF composites decreased at higher (>34 vol.%) fibre loadings. Tensile, flexural, and impact strengths of jute/PF composites were found to be higher than those of rockwool/PF composites. The maximum hardness values were obtained 42 vol.% for jute/PF composite, and 34 vol.% for rockwool/PF composite. Further increase in fibre loading adversely affected the hardness of both composites. For jute/rockwool hybrid PF composites, tensile and impact strengths decreased with increasing rockwool fibre loading. The maximum flexural strength of jute/rockwool hybrid PF composites was obtained at a 0.82:0.18 jute/rockwool fibre ratio while maximum hardness was observed at a 0.28:0.72 jute/rockwool fibre ratio. The fractured surfaces of the composites were analysed using scanning electron microscope in order to have an insight into the failure mechanism and fibre/matrix interface adhesion.     

Use of maleated castor oil as biomodifier in unsaturated polyester resin/fly ash composites

Maleated castor oil (MACO) was prepared and was used as biomodifier in unsaturated polyester resin (UPE)/fly ash composites. The prepared MACO was characterized for its molecular weight and viscosity. MACO was blended with UPE in three different ratios like 5, 10 and 15 wt%. Fly ash was incorporated in the blend matrix (10 wt%) and curing was done by free radical polymerization. MACO was polymerized and crosslinked with UPE in situ during the formation of the composites. The cured matrix therefore formed an interpenetrating polymer network and the enhancement in properties was significant. Incorporation of 5 wt% MACO was most effective compared to 10 and 15 wt%, when the impact strength increased by 52% without any loss in modulus. The glass transition temperature also shifted to a higher temperature indicating strong intercomponent bonding in this set of composites.     

Preparation and characterization of iptycene polymer/SWCNT nanocomposites

To enhance the strength while retaining the ductility of triptycene polyester, triptycene polyester/SWCNT nanocomposites were prepared. First, two different types of triptycene polyesters containing triptycenes that differ in size were synthesized and their mechanical and thermal characteristics were studied. Thermal analysis showed that the polyester containing the larger triptycene posed as a bigger hindrance factor to polymer chain-packing, resulting in lower crystallinity. Although the presence of triptycene interfered the packing of polymer chains, the increased size and amount of triptycene enhanced the thermal stability of the polymer. For the smaller sized triptycene-polyester/SWCNT composites, higher SWCNT content increased the stiffness and strength of the composite, but at the expense of the ductility. The increase in SWCNT content in the larger-sized triptycene polyester/SWCNT composites somewhat decreased the stiffness as well as the ductility of the polymer.     

Investigation of jute-lignin-poly (3-hydroxybutyrate) hybrid biodegradable composites with low water absorption

This study developed a novel PHB-lignin-jute biodegradable composite with preferable mechanical properties and low water absorption. The appearances of fracture surface of composites were analyzed by scanning electron microscope. The result suggested a Gaussian-like distribution of the size particles supporting the presence of lignin with a radius smaller than 0.5 μm. According to X-ray diffraction, the presence of lignin and jute fibers was decreased the crystallization of PHB. Moreover, the glass transition temperature of PHB increased, and the endotherm during glass transition was decreased. The maximum tensile strength and modulus of composites were obtained with 30 wt% jute fiber contents and 4 wt% lignin contents. The presence of jute fibers was largely increased the water absorption of composites. However, the presence of lignin was effectively decreased the water absorption of composites at saturation levels.     

Physical properties of polymer composite: Natural rubber glove waste/polystyrene foam waste/cellulose

The polymer composite was prepared from the wastes of natural rubber glove (NRG) and polystyrene foam (PSF) blended with cellulose from sugar cane leaves via the laminate method. The NRG and PSF were firstly dispersed in toluene under continuous stirring. Then, maleic anhydride (MA) was added into the mixture. Effects of blend ratio and of MA content (0.5-15%, w/w) on physical properties of the polymer composite were investigated. The toluene resistance of the polymer blend was improved after adding MA and cellulose. The highest toluene resistance was achieved when using 12% cellulose. The chemical reactions of MA with polymer blend and with composite were confirmed by ATR-FTIR. The hardness of the polymer blend and composite increased as a function of PSF. In addition, their impact strength increased with increasing NRG and cellulose contents.     

Electrospun form-stable phase change composite nanofibers consisting of capric acid-based binary fatty acid eutectics and polyethylene terephthalate

The four binary fatty acid eutectics of capric-lauric acid (CA-LA), capric-myristic acid (CA-MA), capric-palmitic acid (CA-PA), and capric-stearic acid (CA-SA) were firstly prepared as solid-liquid phase change materials (PCMs); then, the composite phase change nanofibers consisting of CA-based binary fatty acid eutectic and polyethylene terephthalate (PET) were fabricated by electrospinning for thermal energy storage. The maximum mass ratios of fatty acid eutectics versus PET in the nanofibers could reach up to 2/1. The FE-SEM images revealed that the composite nanofibers possessed smooth and cylindrical morphological structure having diameters of about 100–300 nm. The fatty acid eutectic could be uniformly distributed in the three-dimension network structure of the PET nanofibers. The FT-IR results indicated that the fatty acid eutectic and PET had no chemical reaction and exhibited good compatibility with each other. The DSC measurements showed that the prepared composite nanofibers had appropriate phase transition temperatures (about 5–38 °C) based upon climatic requirement, whilst the phase change temperatures and the enthalpy values of the composite nanofibers could be adjusted by changing the contents and the types of binary fatty acid eutectics in the nanofibers. The TGA results suggested that the onset thermal degradation temperatures and charred residues at 700 °C of the composite nanofibers were lower than those of pure PET nanofibers, but higher than those of fatty acid eutectic, which were caused by the fact that the PET had better thermal stability than fatty acid eutectic.     

Evaluation of mechanical properties of jute/glass/carbon fibers reinforced hybrid composites

A study on the tensile and flexural properties of jute-glass-carbon fibers reinforced epoxy hybrid composites in inter-ply configuration is presented in this paper. Test specimens were manufactured by hand lay-up process and their tensile and flexural properties were obtained. The effects of the hybridization, different fibers content and plies stacking sequence on the mechanical properties of the tested hybrid composites were investigated. Two-parameter Weibull distribution function was used to statistically analyze the experimental results. The failure probability graphs for the tested composites were drawn. These graphs are important tools for helping the designers to understand and choose the suitable material for the required design and development. Results showed that the hybridization process can potentially improve the tensile and flexural properties of jute reinforced composite. The flexural strength decreases when partial laminas from a carbon/epoxy laminate are replaced by glass/epoxy or jute/epoxy laminas. Also, it is realized that incorporating high strength fibers to the outer layers of the composite leads to higher flexural resistance, whilst the order of the layers doesn’t affect the tensile properties.     

Coir fiber reinforced polypropylene composite panel for automotive interior applications

In this study, physical, mechanical, and flammability properties of coconut fiber reinforced polypropylene (PP) composite panels were evaluated. Four levels of the coir fiber content (40, 50, 60, and 70 % based on the composition by weight) were mixed with the PP powder and a coupling agent, 3 wt % maleic anhydride grafted PP (MAPP) powder. The water resistance and the internal bond strength of the composites were negatively influenced by increasing coir fiber content. However, the flexural strength, the tensile strength, and the hardness of the composites improved with increasing the coir fiber content up to 60 wt %. The flame retardancy of the composites improved with increasing coir fiber content. The results suggest that an optimal composite panel formulation for automotive interior applications is a mixture of 60 wt % coir fiber, 37 wt % PP powder, and 3 wt % MAPP.     

Interfacial localization of multiwalled carbon nanotubes in immiscible blend of poly(ethylene terephthalate)/polyamide 6

In this study, multiwalled carbon nanotubes (MWCNTs) were confined or localized in an immiscible blend of poly(ethylene terephthalate)/polyamide 6 (PET/PA6). A co-rotating twin-screw extruder and melt-compounding were used to prepare nanocomposites of PET/PA6 (60/40, w/w) and MWCNTs with various MWCNT contents in the range 0.001–2 phr. The raw, unfunctionalized MWCNTs were used as fillers. A remarkable change in the morphology of the blend happened on the basis of the amount of MWCNTs added to the blend: the PET phase converted into the PA6 phase at a certain MWCNT content. Although the PA6 phase was formed as a domain phase in the PET matrix in blends containing less than 0.01 phr of MWCNTs, the PET phase suddenly became discontinuous because of phase conversion in the PA6 matrix in blends containing 0.01 and 0.05 phr of MWCNTs. In the blends containing more than 0.1 phr of MWCNTs, the initial morphology was recovered, that is, the PET phase became the matrix phase again. Moreover, in the recovered state, the of the PA6 domain was much larger in the blends containing more than 0.1 phr of MWCNTs than it was in the composites that did not contain any MWCNTs and in those that contained 0.001 phr of MWCNTs. The MWCNTs, on the other hand, selectively located at the interface of the PET and PA6 phases. The rheological, electrical, and crystallization behaviors of the blends were also investigated to study the effects of the concentration of MWCNTs on the structure of the prepared composites.