Iranian Polymer Journal最新文献

Abstract

Patterned polyethylene films are mandatory products in the rubber tire industry. They are used as protective lining to prevent contamination of the rubber. This pattern geometry (2D and 3D) prevents the rubber from sticking to each other. The film is desired to be homogeneous, precise in thickness, and have sufficient mechanical strength. The speed and the temperature of the pattern-forming machine are among the factors that determine this relationship between the thickness of the film and its mechanical properties for sustainable quality production. In this study, the effect of the speed and the temperature of the pattern machine on the pattern thickness during the creation of the pyramid-shaped pattern applied on a 100 ± 5 µm thick polyethylene film were examined. Four different machine speeds (24, 26, 28, and 30 m/min) and three different temperatures (100, 110, and 120 °C) were studied as variables. The impact of parameters on film thicknesses and tensile properties was assessed. Film thickness varied from ~ 375 to ~ 340 µm at higher machine speed, strength-at-break values decreased from 28 to 22 MPa, and elongation values dropped from 575 to 437% with the increment in speed. On the other hand, at higher temperatures, thickness rose from ~ 360 to ~ 390 µm, and elongation values reduced from 440 to 410%. Within the scope of the experimental studies, it was observed that the film thickness changes and the mechanical properties can be controlled by changing the line speed or process temperature.

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Developing an effective flame retardant for cotton is urgently needed to minimize the life and property loss caused by fire hazard. Here, diphosphonate system flame retardant, the ammonium salt of 1-hydroxyethylidene-1,1-diphosphonic acid (AHEDPA) is obtained by reacting urea with etidronic acid (or HEDPA), which is newly synthesized from acetic acid, phosphorus oxychloride and phosphorous acid. We predicted the suitable conditions of phosphorylation reaction for enhancing grafting rate of AHEDPA on cotton fibers, and revealed the mechanism of reaction using dicyandiamide as an accelerant. Through the Fourier transform infrared spectra and scanning electron microscopy analysis, it was found that AHEDPA with P = O(ONH₄⁺)₂ functional groups could be combined with –OH groups of cellulose, creating the P−O−C and P−NH₂ bonds. Limiting oxygen index, vertical flame test and cone calorimetric measurements were carried out on the untreated and treated cotton fabric samples with AHEDPA at different concentrations, demonstrating that the flame retardant cotton fabric with excellent washing durability were successfully obtained. Through the thermogravimetric analysis, it was confirmed that the cotton fabrics treated with AHEDPA exhibited a promotion of dehydration in cellulose and thus an increase of char formation rate, thereby protecting the substrate (cotton) from heat and fuel. The newly proposed method could enhance the grafting rate of cotton and remarkably improved the flame retardancy and durability of cotton fabrics, highlighting a wide prospect in production of flame retardant clothes.

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The present investigation focuses on elucidating the novel impact of both carbon nanotubes (CNTs) and multi-walled carbon nanotubes (MWCNTs) on thermal behavior and crystallization kinetics of isotactic polypropylene (PP) composites. Our primary objective is to unveil the distinctive influence of these nanotubes on PP crystallization and its thermal properties, paving the way for tailored applications in high-performance materials. Incorporating CNTs led to a noteworthy elevation in crystallization temperature without significantly altering the polymer melting point. Furthermore, our findings revealed an increased critical cooling rate in correlation with higher CNT concentrations, representing a crucial parameter for nucleation effectiveness, independent of CNT load and crystallization temperature. The study demonstrated CNTs' specific role in expediting the α-phase development in PP during isothermal crystallization experiments. Additionally, the investigation into MWCNTs within PP nanocomposites highlighted a pivotal percolation threshold at 0.5% (by weight) MWCNTs. Below this threshold, enhancements in physical properties were observed without requiring a compatibilizer. Augmented interfacial area between PP and MWCNTs notably enhanced PP's thermal stability, particularly evident at elevated temperatures, with heat-treated fibers exhibiting a distinct, narrow melting peak at 170 °C. These novel discoveries significantly advance our understanding of how CNTs impact PP crystallization and underscore the development of superior PP nanocomposites endowed with heightened thermal properties, catering to targeted applications demanding superior performance.

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Here in, new nitrogen and sulfur co-doped carbon quantum dots (N,S-CQDs)/polyurethane (PU) nanocomposites have been prepared as efficiently sensitive and selective fluorescent sensors to detect mercury ions. At first, N,S-CQDs as fluorescent nanoparticles, 1, 2-bis (4-isocyanatophenoxy) ethane and bis (2-hydroxy ethyl) terephthalate (BHET) containing two hydroxyl groups were synthesized. The N,S-CQD_S nanoparticles were synthesized through microwave-assisted carbonization of PU wastes at the presence of sulfuric acid and thiourea. Then, new fluorescent polyurethane nanocomposites were synthesized through an in situ polymerization reaction between new fabricated diisocyanate, BHET and 5 and 10% (w/w) of the N,S-CQDs nanoparticles. The N,S-CQDs/PU-a (6a) and N,S-CQDs/PU-b (6b) nanocomposites containing 5 and 10% (w/w) of fluorescent nanoparticles showed a broad concentration range of 0–250 and 0–200 µM of mercury ions with quenching efficiencies (η) of 95% and 97%, respectively. The limit of detection (LOD), limit of quenching (LOQ), and quenching constant (K_sv) of two nanocomposites were calculated. According to the obtained results, the N,S-CQDs/PU-b nanocomposite (6b) exhibited better performance in Hg⁺² sensing because of lower LOD and LOQ and higher K_sv at lower concentrations of mercury ions. Therefore, an increase in the fluorescent nanoparticles loaded in the nanocomposite, led to an enhancement of the selectivity of mercury (II) ions and sensitivity to its detection. The N,S-CQDs/PU-b nanocomposite (6b) exhibited the LOD, LOQ, and K_sv values at 2.03 µM, 6.77 µM, and 6694.6 M⁻¹, respectively. So, the synthesized N,S-CQDs/PU-b nanocomposite (6b) is an excellent sensor for mercury ions.

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The catalytic effect of titanium dioxide nanoparticles (n-TiO₂) on the thermal properties and the decomposition kinetics of the double-base nitrocellulose (NC)/nitroglycerin (NG)/diaminoglyoxime (DAG) propellants were verified by thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) analysis techniques. There were no visible changes in the degradation peak of DSC traces (around 2–5 °C) after the addition of n-TiO₂ to the propellant. The thermokinetic and thermodynamic parameters of the propellants were computed using the equations of Ozawa–Flynn–Wall, Coats Redfern, Starink and Kissinger. The nanocomposites revealed the single-stage thermal decomposition mechanism while the control sample decomposed as two-stage mechanism. The composites containing 1% and 3% (by weight) of n-TiO₂ showed lower and higher E_a values compared to the pure sample, respectively. This exhibited the catalytic effect of n-TiO₂ on the decomposition process at 1% and 3% (by weight) of n-TiO₂. The lower values of self-accelerating decomposition temperature (T_SADT) and critical ignition temperature (T_b) for the nanocomposites imply their higher sensitivity compared to the pure propellant. The entropy and enthalpy of the decomposition processes increased after adding n-TiO₂ into the pure sample. The positive values of (Delta H^ne) and (Delta G^ne) confirmed that the processes are non-spontaneous. Moreover, the kinetic modeling methods showed that the presence of n-TiO₂ changes the mechanism functions and the kinetic equations of the thermal degradation.

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Long-lasting anti-fouling membrane of polyvinylidene fluoride (PVDF) requires covalently bonded hydrophilic units, which faces challenges like multi-step treatments yet uneven modification due to heterogeneous reaction. For that, grafting hydrophilic polymer chains onto PVDF through homogeneous reaction was reported in this work. First, PVDF was dehydrofluorinated in solution by adding a small amount of ammonia water to generate C=C double bonds, and then vinyl-monomer of N-vinyl pyrrolidone (NVP) or vinyl acetate (VAc) was evenly grafted through heterogeneous reaction to provide hydrophilic side chains. The successful syntheses of the graft copolymers were confirmed using Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The grafting degrees have been controlled by the feeding amounts of the monomers. Moreover, the reaction mixture of PVDF-g-PVP was used as additive to prepare hydrophilic PVDF membrane, while the graft copolymer PVDF-g-PVAc was directly prepared into hydrophilic membrane. Water contact angles and bovine serum albumin adsorption capacities of the membranes were measured to evidence the improvements in their hydrophilicity and fouling resistance, and the porosities and water fluxes were determined to indicate their potential. The results suggest that the PVDF graft copolymers synthesized through the homogeneous reaction may find promising application in membrane field.

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Minor and severe burn injuries are common and highly complicated pathology causing huge mortality and costly wound treatment protocols. In this work, an injectable microgel assembly was developed to accelerate burn wound healing rate and quality where the network formation occurred after injection of the precursor on the wound bed. Poly(hexamethylene biguanide) (PHMB), an amine-containing antibacterial polymer, was synthesized and functioned as a linker of microgels by the addition of a specific deep eutectic solvent (DES) as a catalyst for particles connection. The major function of the eutectic mixture was to assist in the cross-linking of the microgels; however, it could play as an antibacterial agent against Gram + bacteria. The THDES was prepared by the reaction of arginine with ascorbic acid (Asc), and glycerol ([DES]_Arg/G,A), two of which are known as the components involved in the wound healing process. Depending on the PHMB concentration, the microgel assembly experienced a gel-to-sol transition under shear stresses ranging from 10⁴ to 10⁵ Pa and exhibited much stronger antibacterial activities as the fraction of PHMB increased. Application of the developed hydrogel promoted healing of the infected burned rat, enhanced re-epithelialization, and attenuated the formation of fibrotic scar tissue.

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This paper provides a thorough investigation of the mechanical, thermal and morphological properties of polypropylene homopolymer (HPP) reinforced with unmodified minor mineral fuller’s earth (UMMFE) to comprehend and evaluate the properties over conventional polypropylene. UMMFE was characterised by FTIR, TGA, SEM and particle size analysis. HPP/UMMFE composites were prepared on a co-rotating twin-screw extruder with a varied content ranging from 0 to 5% (by weight). The dispersibility of HPP and UMMFE was analyzed using scanning electron microscopy (SEM). Mechanical tests showed an increment of 14% in the tensile modulus for HPP5, in which UMMFE demonstrated a strong reinforcing effect to sustain stress, also resulting in improved tensile strength-at-yield by 13%. Also the flexural modulus increased, showing a 28% rise from 1652 MPa (HPP) to 2122 MPa (HPP5). It was found that UMMFE particles in the HPP matrix affected the interfacial properties of the composites. The comparative investigation of thermogravimetric analysis (TGA) also revealed that the thermal stability of the composites reinforced with UMMFE at 5% (by weight) increased by approximately 56.37%. HPP/UMMFE composites exhibited optimum performance at 5% (by weight) clay loading. This study aims to use UMMFE clay as a potential filler in various sectors of application like automobile, manufacturing, construction, packaging and act as a cushion in the scenario of scarcity of material.

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The present study focuses on the mechanical and erosive wear properties of functionally-graded polymer materials (FGPMs) and functionally-graded hybrid composites. Polyester resin is used as a polymeric matrix, while titanium dioxide (TiO₂) and aluminum (Al) as particles and glass fiber (GG) as fiber reinforcements are used in the composites. The samples are fabricated through the lay-up lamination technique. Initially, four-layered FGPMs were fabricated using TiO₂ and Al particles individually in weight percentages varying from 2 to 8% (by wt). Then, four-layered hybrid functionally-graded composites were prepared using 2–4% (by wt) Al and TiO₂ along with two layers of glass fibers. A comparison among functionally-graded materials and functionally-graded hybrid materials in terms of mechanical strength (tensile, flexural and interlaminar) and erosion behavior is evaluated on a universal testing machine and air jet erosion testing apparatus, respectively. The improved tensile strength is shown by aluminum-based functionally-graded and hybrid functionally-graded composites owing to their greater ductility. Nevertheless, titanium dioxide-based functional- graded and hybrid functional-graded composites exhibited greater flexural strength due to their high hardness. From the erosion results, Al and TiO₂ functional-graded composites revealed semi-ductile and semi-brittle behavior, respectively. Moreover, hybrid functional composites display altered material behavior at their extreme layers. Two layers of glass fiber (GG) with Al (2.4% by wt) filler functional composite achieved 1.91% maximum tensile strength compared to Al (2, 4, 6, 8% by wt) filler composite.

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