Iranian Polymer Journal
Year:2022 | Volume:31 | Issue:10|Papers Count:11

Polymeric nanocomposites are strong alternatives for filled polymers (containing fillers) or blends. Due to certain properties, such as high Young’, s modulus, good tensile strength and carbonic nature, it is more economical to use nanotubes instead of metals. Although nanotubes do not interact easily with other materials, chemical modifications can still make them to interact favorably with other materials. Uniform distribution and improved adhesion of nanotubes are important issues that must be paid attention for successful synthesis of nanocomposites. The main goal of the present work is to make a uniform distribution and proper interaction between the PU matrix and CNTs. Therefore, carboxylic functional groups were created on the surface of nanotubes using acid and plasma treatment methods and the properties of resulting nanocomposites were studied. FTIR results corroborated that the micro-phase separation values increased by 7% in acid-modified and 3% in plasma-modified nanocomposites compared to its unmodified counterpart. The frequency sweep analysis proved that the surface modification of CNT promotes the non-terminal behavior and viscosity upturn at low frequencies and this effect was more noticeable in acid-treated samples compared to plasma-treated ones. The DMA analysis results confirmed that surface modification at low content of CNT decreases the Tg of a soft segment-rich phase, whereas at higher content of CNT, surface modification increases this value. Electrical conductivity measurement illustrated that the electrical percolation threshold in acid-modified nanocomposites was decreased by 35% and in plasma-modified nanocomposites by 19% compared with its untreated counterpart.

Present work reports the synthesis of phosphorus-containing imine derivative of vanillin for application in the flame-retardant (FR) polyurethane (PU) coatings. The multifunctional vanillin–, imine–, phosphorus (VEDAP) compound involved a two-stage synthesis in which the first stage contained the imine formation by the reaction of vanillin (a biobased compound) and ethylenediamine (EDA). The latter stage continued with the incorporation of phosphorus moiety into the compound. The synthesized compound was incorporated into a commercial PU 2-pack formulation with different concentrations and coated onto the mild steel panels. The chemical structures of the intermediates were confirmed using Fourier-transform infrared (FTIR) spectroscopy, determination of the hydroxyl values, and nuclear magnetic resonance (NMR) spectroscopy. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results revealed an increase in the degradation temperatures of the VEDAP containing coatings and the char yield. The heat resistance index temperatures (THRI) showed significant improvement in thermal stability with increasing concentration of VEDAP. The change in the coating formulations' crystallinity was studied using X-ray diffraction (XRD) method. The mechanical properties almost retained even for higher loading of VEDAP while biobased content apparently increased with increasing concentrations of VEDAP. The flame-retardant properties were checked using the limiting oxygen index (LOI) and UL-94 vertical burning test. The VEDAP has remarkably imparted flame retardancy with the highest LOI value of 29 with no dripping and self-extinguishing behavior within 10 s.

Polymer membranes based on natural polymer chitosan (CH) and variable content of carbon nanotube-titanium dioxide (CNT-TiO2) composites were prepared by solvent casting at room temperature. The interest in natural polymers is enormous due to the depletion of oil and natural gas resources. Furthermore, the use of biodegradable biopolymers reduces the environmental impact of the disposal and avoids the long-term degradation of synthetic polymers. The thermal, morphological and electrochemical properties of the membranes were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarized optical microscopy (POM) and complex impedance spectroscopy. The obtained results revealed a predominantly semi-crystalline morphology and a satisfactory ionic conductivity. The sample with the highest conductivity was CH-20CNT-TiO2-0. 05, which attained 1. 22 , × , 10–, 4 S cm−, 1 at 90 º, C. The significant effect of glycerol as a plasticizer on the conductivity of the materials was studied. The combination of Pt-based catalysts with TiO2 led to a conductivity increase (90 , × , 10–, 3 S cm−, 1 at 90 °, C). The conductivity measurements in the obtained composites allowed some evidence to be considered for the influence of CNT-TiO2 in the transfer of current through the CH matrix. The encouraging properties (conductivity, thermal behaviour, morphology) of the samples lead us to suggest the incorporation of these materials as electrolytes in solid electrochemical devices. Composite membranes that are environmentally friendly and have attractive properties are developed for energy conversion device applications.

This study focuses on replacing carbon black (CB), a non-renewable widely used filler with known environmental threats, by waste mica (WM) in natural rubber (NR) vulcanizates. Two series of CB and WM-filled NR composites were prepared by varying from 0 to 60 pphr at 15 intervals. NR/WM vulcanizates marked slow curing rates with prolonged curing times and better scorch safety. The comparison of the physico-mechanical properties indicated WM could not establish an equal degree of rubber-filler interactions similar to CB, which may be ascribed to large particle sizes and uneven filler distribution in NR. De-bonded WM particles seen in scanning electron microscope images provided evidence for poor interfacial adhesions. The variation in properties showed a similar trend while there was wide a difference in those properties of both types of higher filler loading. Damping properties of the vulcanizates revealed lower skid and rolling resistance of NR/WM vulcanizates compared to their counterpart irrespective of the filler loading. Resilience and thermal conductivity properties suggested that NR/WM vulcanizates possessed improved heat build-up and heat insulation properties. Overall results suggested that WM has the potential to replace CB in NR compounds at low filler loadings.

Polymeric materials are used as ideal carriers for drug delivery applications due to their excellent physicochemical properties, however, the controlled preparation and drug release behavior of cross-linked polymeric microspheres are still open to discussion. Hexacyclotriphosphazene (HCCP), as one of the prominent members of polyphosphazene, can be easily treated with many monomers to produce micro/nanospheres. In this research work, cross-linked poly(cyclotriphosphazene-co-resveratrol) (PCTPRS) microspheres were prepared by the precipitation reaction of HCCP and resveratrol (RSV). The apparent peak at 961 cm−, 1 in FTIR spectra of the microspheres revealed that the polymerization between RSV and HCCP was successful. The TGA results showed that the increase in thermal properties was owing to the highly cross-linked structure of the microspheres. The XRD patterns showed the amorphous nature of the microspheres compared to the monomers. The obtained SEM micrographs dictated that the HCCP: RSV mole ratio had a significant impact on the size of the microspheres. The PCTPRS microspheres were used as carriers for the drug loading and release study of the anti-cancer model drug camptothecin (CPT). The drug loading efficiency of the PCTPRS microspheres was found to be 89. 9 mg/g. Whereas the release study revealed that 53. 0% of CPT was released at pH 4. 0 and 37. 5% at pH 7. 4 from the drug-loaded microspheres after 11 days.

The influence of autoclave cure vacuum on the microstructure and mechanical properties was studied for a woven carbon fiber/epoxy resin composite laminate, AS4/8552S. The laminates were cured at vacuum pressures varied from 0 to –,0. 08 MPa. Their corresponding thickness, density, resin volume fraction, fiber volume fraction, and void content were established accordingly as a function of vacuum pressure. The combined loading compression and short beam shear mechanical tests were determined at 120 °, C. The results showed that thickness, density, laminate compressive strength (LCS), and interlaminar shear strength (ILSS) varied exponentially with applied vacuum pressure and reached a steady state at the applied vacuum of –,0. 04 MPa. However, applying this vacuum level improved thickness, density, fiber volume fraction, and void content by approximately 42. 10, 50. 97, 46. 69 and 99. 84%, respectively, compared to that found without a vacuum bag. Pearson's correlation analysis revealed linear variation in ILSS and LCS modulus with density, fiber volume fraction, void content and between laminate compressive modulus (LCM) and density. One-way ANOVA statistical analysis showed that the most critical parameters affecting ILSS are density and void content. It is also shown that all physical microstructural parameters affect LCS, whereas density and fiber volume fraction are the most significant parameters affecting LCM.

A study was conducted to develop a high damping elastomeric nanocomposite for constrained layer damping (CLD) arrangement to reduce structural vibration at a low weight penalty. Hence, an organically modified montmorillonite (OMMT) clay was used as reinforcement at loadings of 2, 5, 10 and 20 phr in nitrile rubber/polyvinyl chloride (NBR-PVC) 70/30 (w/w) blend to obtain a series of nanocomposites. Montmorillonite clay was selected since it is a natural mineral and hence environmentally friendly. The nanocomposites were evaluated for morphology, dynamic viscoelastic properties in frequency scale and vibration damping efficacy as a CLD on an aluminum strip (Oberst Beam) by modal response. The experimental damping was compared to two theories by Nakra and Torvik, and found to be in better agreement with that by Torvik in general between 300 and 600 Hz. There are deviations from both theories below and above this range. The dynamic viscoelasticity and vibration damping were related to the uniformity of dispersion and extent of intercalation/exfoliation of OMMT. The nanocomposite with 5phr OMMT showed best filler distribution and less agglomeration. The average CLD loss factor increased from 0. 08 for unfilled vulcanizate to about 0. 135 with 5 phr OMMT and 0. 145 for 20 phr OMMT. The enhancement of damping at such low OMMT content compared to the unfilled vulcanizate is possibly due to additional frictional damping by the plate type nanoclay under dynamic strain similar to the Rayleigh or Coulomb damping. There was no direct correlation between loss modulus of the material and structural damping.

Isotactic polypropylene (iPP), in connection with its good processability, provides a matrix of composites applied in many industries. An influence of additives on iPP supermolecular structure, and consequently on its properties, should not be overlooked. The matter of inappropriate adhesion between a non-polar iPP matrix and polar fillers tends towards analyses and implementations of new kinds of coupling agents, e. g., polar polymeric waxes. Moreover, the presence of waxes in the composite matrix will change the MFR and may affect the iPP crystallization. To this day, literature has confirmed some beneficial effects observed during the application of polymer (e. g., polyethylene or polypropylene) waxes in the iPP composites technology, but did not demonstrate the result of its presence on iPP nucleation and crystallization. In the current paper, we focused on the simultaneous influence of lignocellulosic filler and coupling agent on crystallinity of iPP. Various research methods were applied, such as: WAXS, DSC, FTIR or PLM. Two oxidized polyethylene waxes (acid numbers: 23 and 89, respectively), as well as commercial non-oxidized polyethylene wax, were used as coupling agents. We found that an addition of 3% (by wt) of PE waxes drastically changes the processing parameters of the composites. The influence of waxes was observed in changes of crystallization kinetics, melting temperatures and in the degree of crystallinity. The percentage of crystalline phase in materials was decreased each time after waxes application. Moreover, the shear stress applied during crystallization changed the PE waxes role on iPP crystallization in WPC composite. The beneficial effect of flowing rapeseed straw powder was decreased by the presence of PE waxes.

Various adsorption materials are widely used in the treatment of heavy metal wastewater and dye wastewater because of their good adsorption properties. Here, polyethyleneimine (PEI)-modified chitosan magnetic hydrogels were prepared through a chemical co-precipitation method using glutaraldehyde as the cross-linking agent. The functional groups and structures of the hydrogels were characterized by Fourier-transform infrared spectroscopy and X-ray diffraction phase analysis, respectively. The surface structures were characterized by scanning electron microscopy. The magnetic parameters including hysteresis loops of the hydrogel were measured. Heavy metal adsorption experiments showed that the synthesized magnetic hydrogel had good adsorption properties for heavy metals, and saturated adsorption of Pb2+, Ni2+, and Cu2+ reached 100. 32, 105. 98, and 128. 96 mg g−, 1, respectively. Studies of isothermal adsorption and adsorption kinetics showed that the adsorption process follows a pseudo-second-order kinetics model adsorption, as the Langmuir isothermal adsorption. Selective adsorption of heavy metal ions by a magnetic hydrogel showed that Pb2+, Ni2+, and Cu2+ had obvious competitive adsorption (on the order of Cu2+ , > , Ni2+ , > , Pb2+). The cyclic adsorption of metal ions showed that the magnetic hydrogel could be reused by 0. 02 mol L−, 1 EDTA-2Na desorption. The hydrogel retained its good adsorption properties, and the removal rate of Pb2+, Ni2+, and Cu2+ was still more than 85% after 4 cycles. The PEI-modified chitosan magnetic hydrogel adsorbent thus had broad application prospects for the treatment of heavy metal wastewater.

Polypropylene (PP)/postconsumer recycled poly(ethylene terephthalate) (rPET) blend has gained much attention as an environmentally friendly and economical material in various industrial applications. The aim of this study is to improve the properties of PP/rPET blend with talc, glass fiber, and carbon fiber mixture to be included by twin-screw extrusion followed by injection molding. Maleic anhydride grafted polypropylene (PP-g-MA) and chain extender (Joncryl ADR 4368) were used as the coupling agent. The effects of various coupling agents were evaluated in terms of the mechanical, morphological, electrical, and thermal properties of the PP/rPET hybrid composites. The mechanical properties of the composites were characterized by tensile and Charpy impact tests. Scanning electron microscopy (SEM) was used to assess the fracture surface morphology and the dispersion of the filler. The thermal properties of the composites were characterized using differential scanning calorimeter (DSC), heat deflection temperature (HDT), and Vicat softening temperature (VST) tests. The results showed that the composites morphology was dramatically affected by the addition of coupling agent. Tensile and impact strength increased in the presence of coupling agent of the composite due to the improved interaction at the interface of polymers. HDT and VST of the composite were increased significantly in the presence of PP-g-MA.

Amputation is a surgical operation to remove a part or limb from the body due to some major illness, birth defect, accidents, vascular disease, surgery, etc. The number of amputee patients is increasing day by day all over the world and in most cases they cannot afford the imported legs because these legs are expensive and heavy. Hence the present review article explains the development of light weight and cost-effective biocomposites for prosthesis limb applications. The details of the performance of exiting biomaterials for knee prostheses application have been explained, and their advantages, disadvantages, and limitation of their uses have been analyzed. To explore patients’,satisfaction, design analysis of prosthetic limb components has been discussed to provide better suitability, stability, and comfortability for stable movement of adaptive legs. This review also discusses the factors that affect the performance of the prosthetic limb. Fiber-reinforced composites are the best suited and promising biomaterials for prosthetic limb application due to greater flexible design and lighter weight that provide higher specific strength and stiffness compared to conventional biomaterials. Due to the rapid increase in patients, the availability and cost of biomaterials are the major issues and problem in achieving cost-effective prosthesis for weaker people as well as for short-term usages. Therefore, to meet the current challenge, naturally derived biocomposites are the best promising and suited biomaterials for developing prosthesis sockets due to their availability, lighter weight, more cost-effective, more biocompatible, and biostable compared to other existing materials, providing good specific strength and stiffness.