جستجوی مقالات مرتبط با کلیدواژه "polymer" در نشریات گروه "شیمی"

Pyrolysis of natural rubber (NR) is environmentally friendly solution as a clean recycling process. The pyrolysis of cis-1,4-polyisoprene is studied with a focus on the quantity and quality of final products from experimental and theoretical aspects. Although many researches have been conducted on the experimental pyrolysis of NR, but little information is available about the theoretical part of this process. For experimental pyrolysis, a small-scale science lab quasi-reactor was used and residue after pyrolysis was indetified by FT-IR and GC-MS analyses. The ReaxFF molecular dynamic simulations as a novelty method are performed at different temperatures. Increasing of temperature promotes the dissociation of chemical bond between the monomers. It was found that, at the beginning of the simulations, the C–C bonds between monomers break and form C5. This result is in consistent with experimental observations. Also, the main gas product is CH4. The fragmentation paths involve the breakage of C-H and C-C bonds. It means that, the C-C bond of side methyl groups in the main chain is broken, subsequently, methyl radical formed. Then, several C-H bonds breakings conducting to form H free radicals, Next, CH3 and H free radicals combine to form CH4 molecule.

This study reported a multiphased nanocomposite based on the carbonaceous periwinkle shell (CPS) and styrofoam (C8H8) decorated with titanium dioxide (TiO2). A sol-gel protocol at mild conditions was adopted to synthesize the multiphased photocatalyst known as (CPS/C8H8/TiO2) for the photodegradation of toxic methylene blue dye. All the synthesized multiphased nano photocatalysts were characterized and investigated by a high-resolution transmission electron microscope, Scanning electron microscope-energy dispersive x-ray, x-ray diffraction and atomic force microscopy. The x-ray diffractogram confirmed a successful synthesis of multiphased photocatalyst while the high-resolution transmission electron microscope showed the nano aggregates and nano-dispersion of titanium dioxide. The multiphased roughness of the composites was detected by atomic force microscopy which verified the electron trapping ability. In contrast, the scanning electron microscope˗energy dispersive x-ray analyses showed homogenous structure and spatial aggregation enabling efficient utilization of electrons. Ultraviolet-visible diffuse reflectance confirmed a blue shift having a bandgap of 2.8 ev within 300-400 nm. An optimum 99% photodegradation of methylene blue dyes (20 mg/L) was obtained at 100 mL for 0.5, 1.0, and 2.0 wt% at a 278-min irradiation time. The experimental findings are a promising approach to developing a cheap and stable multiphased nanocomposite with promising abilities for dye wastewater effluent treatments

This article explores the insights provided by infrared (IR) spectroscopy into the optical properties and surface morphology of polyethylene (PE) polypropylene (PP), and polyvinyl chloride (PVC) films. Notably, IR spectroscopy can identify absorption lines attributed to various functional groups in addition to those associated with lower-density linear polyethylene. The specific characteristics of IR spectra for linear low density polyethylene are influenced by polymer processing conditions, branching, and monomer content. Moreover, the IR spectrum of PVC offers valuable information about its molecular structure and composition. Comparatively, polypropylene (PP) films exhibit higher absolute light transmission in the ultraviolet and visible spectrum when contrasted with films based on PE and PVC. The utilization of atomic force microscopy (AFM) and IR spectroscopy reveals that heat-induced decomposition and subsequent cooling do not impact the surface roughness or thickness of the films, confirming the retention of structural and electrophysical attributes.

Plasticizers is a type of organic materials that can be enhanced to polymers for improving their several characteristics; for example, mechanical properties and pliantness. Plasticizers are veritably significant for the construct of polymeric membrane for potentiometric methods, a significant type of sensors for electrochemical methods. The suitable application of plasticizers in the formulation of membranes for preparing electrodes. The character of the plasticizer effects fundamental operation pointers of the ion-selective membrane electrodes; for example, slope, selectivity, and the area of linear reply. A plasticizer in the membrane formulation has to be well-matched with the ionophore and polymer and have a small solubility and an upper lipophilicity in solution as aqueous. The selection of the high-quality plasticizer for the improvement of a membrane special to an accurate ion ordinarily includes experimental assessments to discover the ionophore with the plasticizer having suitable response properties of the ion-selective electrodes are acquired. Some instances of choosing good suited plasticizer for the formulation of selective electrodes responsive have been given for organic and inorganic ions.

In this work, PP+CdS/ZnS transparent hybrid polymer nanocomposites were synthesized and studied. The nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive (EDS), and UV-spectroscopy analysis. It was found that the bandgap of PP+1%CdS/ZnS; PP+3%CdS/ZnS, and PP+5%CdS/ZnS; PP+10%CdS/ZnS nanocomposites is 5.2 eV, 5.1 eV, 4.6 eV, respectively. SEM analysis showed that the ZnS and CdS nanoparticles are evenly distributed in the polymer matrix. Furthermore, the average size of nanoparticles in the PP+3%CdS/ZnS, PP+5%CdS/ZnS nanocomposite is 40-54 nm, 29-56 nm, respectively. Photoluminescence properties of hybrid PP+CdS/ZnS nanocomposites were also investigated. It was established that introduction of ZnS and CdS semiconductor nanoparticles into the polypropylene matrix leads to expanding the region of the spectral sensitivity of hybrid nanocomposites. The photosensitivity of PP+CdS/ZnS nanocomposite films was also investigated.

Stabilization of polypropylene (PP) against thermal oxidation, due to the susceptibility of this commodity polymer to oxidation, is of great importance from both scientific and industrial points of view. The present work aimed at preparing a new polymeric antioxidant for polypropylene, which has no tendency toward migration from the polymer. Accordingly, a diacid (phenylmalonic acid), which has a labile hydrogen atom and can act as a hydrogen donor antioxidant, was polymerized with 1,4-phenylenediamine to render a polyamide. Occurrence of the reaction was confirmed by FT-IR spectroscopy, differential scanning calorimetry (DSC), gel permeation chromatography and thermogravimetric analysis (TGA). The synthesized polyamide was melt-mixed with PP and its uniform distribution in the matrix was verified by the yellowness index measurements. Oxidation onset temperature and oxidative induction time of the samples using DSC proved that the additive enhances stability of the polymer remarkably in melt state. However, its stabilization efficiency is not as outstanding as that of SONGNOX 1010; a conventional antioxidant for PP. But oven ageing experiments followed by FT-IR spectroscopy revealed that the synthesized antioxidant amends thermo-oxidative stability of the polymer in solid state with an eminent efficiency which is even better than that of SONGNOX 1010. Furthermore, its remarkable stabilization activity was proved by DPPH method. Finally, the synthesized polyamide’s potential, as an efficient antioxidant for PP, especially in the long-term stabilization, was assigned to the presence of the two different hydrogen donor groups, i.e. allylic and amine hydrogen atoms, in the molecular structure of the new antioxidant.

Stabilization of polypropylene (PP) against thermal oxidation during its melt processing and service life, due to its susceptibility to oxidation, is of great importance from both scientific and industrial points of view. The present work was devoted to synthesize a new antioxidant for polypropylene through esterification reaction between thymolphthalein and stearic acid. The occurrence of the reaction was confirmed by Fourier transform infrared (FT-IR) spectroscopy, size exclusion chromatography and melting point measurements. The reaction product was proved to be a mixture of thymolphthalein mono- and di-stearate. It was also shown that the esterification of thymolphthalein, in addition to lowering its polarity, lessens its melting point significantly from 246 to 186 °C, hence, helping the synthesized additive to be mixed with the polymer more favorably in comparison to thymolphthalein. Differential scanning calorimetry demonstrated that the new additive improves stability of the polymer in melt state, significantly. Moreover, oven ageing experiments revealed that the additive stabilizes the polymer against oxidation outstandingly in solid state and its efficiency is comparable to that of SONGNOX 1010, which is a powerful commercially used antioxidant for the polymer.