Search

Branched polyesters based on the polyethylene terephthalate were synthesized by incorporating isophthalic acid (IPA) and trimellitic anhydride (TMA). TMA has the branching agent role. During the esterification step, only terephthalic acid, IPA, and ethylene glycol were reacted and TMA was added at the beginning of the polycondensation step. Reaction progress was studied using water production and mixing torque increase during esterification and polycondensation steps, respectively. Polycondensation time increases with IPA and decreases with TMA. Fourier transform infrared spectroscopy spectrum shows the production of polyester. Randomness and sequence length were studied using 13CNMR. Results reveal that randomness increases with TMA. Crystallinity and morphology of samples were studied using differential scanning microscopy (DSC). DSC thermograms show that samples turn to an amorphous structure by adding IPA and TMA with decreasing glass transition temperature, Tg. X-ray diffraction spectra approve changing nature similar to DSC results. Dynamic light scattering results present that with an increase in TMA, some size-increasing particles were detected. The rheological behavior of samples was studied using RMS. By adding TMA, the elastic behavior of samples changes to viscous behaviors.

Pollution of surface and groundwater resources with antibiotics creates problems for human health, meanwhile, because of development of antibiotic resistance in bacteria. Chlortetracycline (CTC) is a tetracycline antibiotic, for which different removal methods were developed. Therefore, this study evaluated the removal efficiency of CTC from aqueous solutions using a photocatalytic process. In this study, Bi2WO6 was synthesized by microwave method and Ce loaded on Bi2WO6 by wet impregnation method. The prepared photocatalysts were characterized by XRD, FTIR, SEM, BET/BJH, DRS analysis. The degradation of CTC was investigated by the photocatalysis under solar light. Among the photocatalysts, Ce/Bi2WO6 (8%) had the highest CTC degradation efficiency. Response surface methodology (RSM) with central composite design (CCD) was used to investigate pH, time (min), mass of catalyst Ce/Bi2WO6 (8%) (g), and concentration of CTC (mg/L). In optimal conditions at pH 3.19, time 201.07 min, mass of Ce/Bi2WO6 (8%) of 0.05 g, and concentration of CTC 24.99 mg/L the photocatalytic degradation percentages of CTC were found to be 99.99%. Isothermic studies have shown that Fritz–Schlunder isotherms provide the best fit with the least error with experimental data.

In this study, waste jute as a novel nanoadsorbent in order to provide a unique micro-mesoporous structure has been successfully synthesized and fabricated. We prepared the nanoadsorbent through a simple chemical activation procedure at the different C/KOH ratios (1:1, 1:2, 1:3, and 1:4) and regarding C/KOH ratios utilized named waste jute A, waste jute B, waste jute C, and waste jute D (WJ-A, WJ-B, WJ-C, WJ-D). To evaluate the physicochemical characterization of the nanoadsorbents, FESEM, elemental mapping, BET, CHNS, FTIR, and XRD analyses were investigated. The performance of synthesized nanoadsorbents for CO2, CH4, and H2S adsorption was evaluated at the pressure range of 1 to 35 bar and at the temperature of 25 °C. The empirical models were utilized in order to investigate the behavior of adsorbed gases. The selectivity and stability of gas adsorption were also investigated. The nanoadsorbents provided a large surface area (2584 m2/g), and WJ-D sample created the highest pore volume (1.47 cm3/g). Furthermore, WJ-D sample provided an excellent CO2, CH4, and H2S uptake at both 1 bar (CO2: 9.15, CH4: 4.2, and H2S: 19.08 mmol/g) and 35 bars (CO2: 26.18, CH4: 10.06). The results also demonstrated that the selectivity of WJ-B and WJ-D at the rate of 10:90 and 1 bar was 2.03 and 2.87, respectively. The elemental analysis showed that the synthesized nanoadsorbents (WJ-A, WJ-B, WJ-C, WJ-D) were rich enough in terms of functional groups, which contained 87.38, 89.88, 91.84, and 93.34 wt% C; 0.72, 1.34, 1.90, and 1.78 wt% H; and 0.36, 0.94, 1.20, 0.91 wt% N, respectively. The thermodynamic parameters were also calculated and the results confirmed a physisorption and multilayer for the nanoadsorbents used. The large surface area and the micropore structure created of the synthesized nanoadsorbents together with low cost and availability make them a superior adsorbent, and consequently its application for gas adsorption in a large scale could be mainly considered.

Currently dioxide carbon and methane as the most important greenhouse gases are constantly being emitted to the atmosphere. Thus, to reduce the detrimental effects resulting from these gases, they ...

In this work, an intelligent approach is applied for the first time in the modelling and optimization of electrospun Polyacrylonitrile/Poly(Vinylidene Fluoride) (PAN/PVdF) nanofiber properties. A genetic algorithm-based computer code was developed to optimize the architecture of an artificial neural network, by which an accurate model was developed for the prediction of nanofiber diameter, the standard deviation of nanofiber diameter and porosity of electrospun membrane. Electrospinning of polyacrylonitrile/poly(vinylidene fluoride) (PAN/PVdF) was applied to obtain a quantitative relationship between selected electrospinning parameters (namely applied voltage, solution concentration, and PVdF composition) and nanofiber diameter, the standard deviation of nanofiber diameter and porosity of electrospun membrane. The morphology and nanofiber diameter were investigated by field emission scanning electron microscopy (FESM). The range of produced nanofiber diameters was from 116 to 379 nm. It seemed that the nanofiber diameter and standard deviation of nanofiber diameter decrease with PVdF composition and increase with solution concentration. The applied voltage had no important effect on the nanofiber diameters. The porosity of the electrospun membrane decreases with solution concentration and increases with PVdF composition.

Aliphatic–aromatic copolyesters based on polybutylene adipate (PBA) and polyethylene terephthalate (PET) prepolymers were synthesized via the two-step melt polycondensation method. The existence of four sequences, namely, butylene adipate (BA), ethylene adipate (EA), butylene terephthalate (BT), and ethylene terephthalate (ET) was approved using 1HNMR spectra. Subsequently, the distribution of the sequences was calculated. The mean BA sequence length decreased markedly with increasing BHET molar ratio in the feed. Thermal properties were investigated using differential scanning calorimetry (DSC) and indicated that incorporating BHET decreases the melting point and crystallinity. Isothermal crystallization experiments show that increase in BHET content decreases the crystallization rate at constant degree of supercooling and same crystal structure. The formation of polymorphic crystals in tetrapolymers was approved by wide-angle X-ray diffraction (WAXD) patterns. Pure α-form crystals were developed after annealing at 27 °C for one month in PBA. Nevertheless, the same annealing conditions led to the development of mixed α- and β-form crystals in copolyesters with up to 15 mol% BHET. Increase of BHET content in the PBAET copolyesters causes decrease in the crystallinity and increase in the β-form crystals. Hence, increase in the elongation at break and decrease in the modulus of elasticity and yield strength of the samples were observed. The hydrolysis degradation rate in alkaline solution first increased, then decreased, and finally remained unchanged with increasing the amount of aromatic comonomer.

Transdermal drug delivery systems have overcome many limitations of other drug administration routes, such as injection pain and first-pass metabolism following oral route, although transdermal drug delivery systems are limited to drugs with low molecular weight. Hence, new emerging technology allowing high molecular weight drug delivery across the skin—known as ‘microneedles’—has been developed, which creates microchannels that facilitate drug delivery. In this report, drug-loaded degradable conic microneedles are modeled to characterize the degradation rate and drug release profile. Since a lot of data are available for polylactic acid-co-glycolic acid (PLGA) degradation in the literature, PLGA of various molecular weights—as a biodegradable polymer in the polyester family—is used for modeling and verification of the drug delivery in the microneedles. The main reaction occurring during polyester degradation is hydrolysis of steric bonds, leading to molecular weight reduction. The acid produced in the degradation has a catalytic effect on the reaction. Changes in water, acid and steric bond concentrations over time and for different radii of microneedles are investigated. To solve the partial and ordinary differential equations simultaneously, finite difference and Runge–Kutta methods are employed, respectively, with the aid of MATLAB. Correlation of the polymer degradation rate with its molecular weight and molecular weight changes versus time are illustrated. Also, drug diffusivity is related to matrix molecular weight. The molecular weight reduction and accumulative drug release within the system are predicted. In order to validate and assess the proposed model, data series of the hydrolytic degradation of aspirin (180.16 Da)- and albumin (66,000 Da)-loaded PLGA (1:1 molar ratio) are used for comparison. The proposed model is in good agreement with experimental data from the literature. Considering diffusion as the main phenomena and autocatalytic effects in the reaction, the drug release profile is predicted. Based on our results for a microneedle containing drug, we are able to estimate drug release rates before fabrication.

Functionalized poly(butylene succinate) (PBSS), prepared via sulfonation of poly(butylene fumarate) (PBF), was successfully applied as a novel polymeric dopant for polyaniline (PANI). To obtain a conductive and degradable PANI:PBSS complex, the aniline monomers were polymerized in the presence of a negatively charged polyelectrolyte template (PBSS). The prepared polymers were characterized through proton nuclear magnetic resonance (1HNMR), Fourier transform infrared (FT-IR), ultraviolet–visible spectroscopy (UV–visible spectroscopy), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), X-ray diffraction (XRD) and electrical conductivity measurements. The hydrolytic degradation of PANI:PBSS was also investigated based on FT-IR analysis and weight loss. Based on the results, the semi-crystalline structure of PBF was changed to an amorphous structure in PBSS and PANI:PBSS. The PANI morphology in the presence of the small dopant (HCl) was granular, while it changed into a fibrillar shape in the presence of the macromolecular dopant. The electrical conductivity of PANI:PBSS (28.6 S/m) was slightly smaller than that of the HCl-doped PANI (48.4 S/m). The alkaline solution could hydrolytically degrade PANI:PBSS and after 10 days, a weight loss of 45% was observed.

A novel material that obtained through combining a biodegradable polymer with a conductive polymer, has been successfully developed by graphene oxide (GO). For the first time, unsaturated poly(butylene fumarate) grafted reduced GO (PBF:RGO) was synthesized via in-situ polymerization method and simultaneous in-situ thermal reduction of GO. It was modified through post-polymerization modification to form sulfonated poly(butylene succinate) grafted reduced GO (PBSS:RGO). Then, PBSS:RGO was incorporated as a polymeric dopant in the synthesis of polyaniline (PANI) to prepare the conductive and anticorrosive compound. Functionalizable PBF and PBF:RGO along with functional PBSS and PBSS:RGO were characterized by 1HNMR. Thermal and crystallization properties of PBF and PBF:RGO were studied using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) with Avrami and Tobin models. Further investigation of crystallinity and dispersion of graphene sheets in the polymer matrix was carried out by X-ray diffraction (XRD). PBF:RGO exhibits higher thermal stability, higher crystallization rate, and lower crystallinity compared with pristine PBF. Final composites (PANI:PBSS and PANI:RGO:PBSS) were also characterized through Fourier transform infrared (FT-IR), contact angle analysis, electrochemical impedance spectroscopy (EIS) and electrical conductivity measurements. PANI:RGO:PBSS indicates a higher conductivity, higher inhibition efficiency and more hydrophilicity than PANI:PBSS.

New biodegradable and biocompatible composites are continuously developed for biomedical applications (e.g., from drug delivery devices to tissue engineering scaffolds). Properties of such systems may depend on their morphology and structure, which are attained after their processing, and therefore, the study of the crystallization kinetics has a particular relevance. The crystallization kinetics of hydroxyapatite-filled poly(butylene terephthalate-co-alkylene dicarboxylate)s has been studied under non-isothermal conditions, using a wide range of cooling rates and different kinetic models. Based on our results, nanohydroxyapatite (nHAp) particles were found to effectively act as additional nucleation sites for poly(butylene terephthalate-co-succinate) (PBST), giving rise to an increased crystallization rate with respect to pure PBST. However, the overall growth rate of HAp nanocomposites decreased compared to the corresponding homopolymers with longer aliphatic dicarboxylic acids (i.e., adipic and sebacic acid derivatives). In order to clarify this point, the activation energy for non-isothermal crystallization was evaluated using the Friedman method and significant differences were observed, suggesting a disturbing effect of nanoparticles on the motion of molecular chains that hindered their capability to reach the growing crystallization front. Isoconversional methods provided a good understanding of the kinetics of the crystallization process and significant information regarding the activation energy, relative crystallinity, and global and local Avrami exponents.

Non-Einstein rheology behavior is developed by using Polystyrene soft nanoparticles (PS-SNPs) in order to reduce viscosity and therefore the flow-ability of nano-composite during molding. PS-SNPs are synthetized by intramolecular crosslinking where the synthetized PS-SNPs’ diameter is kept smaller than the diameter of epoxy chains to result the viscosity reduction through non-Einstein like behavior which is confirmed by DLS measurements. Also rheometric mechanical spectrometer (RMS) test showed about 50% viscosity reduction and the thermodynamic analysis showed that no phase separation will occur during curing process which is usual in epoxy/PS nano-composites. Also the effect of SNPs on epoxy crosslinking kinetic is studied by implementing non-isothermal differential scanning calorimetry (DSC). Using model-free approach to investigate the kinetic itself and its parameters, we have found that the activation energy is lowered by adding SNPs. Also as more conversion took place, the reduction of pre-exponential factor (showing the collision of reacting groups) occurred due to the linear growth of epoxy at early stages of the conversion and network growth is triggered at more conversions. These phenomena propose that for non-Einstein like behavior the polymer matrix molecular weight should be either more than critical molecular weight of entanglement or comparable with molecular weight among entanglements.

In the present study, a novel N-S rich nanoporous carbon based on jute thread waste (JW) as a prevalent cellulosic biomass in order to remove CO2 and H2S from gaseous stream has been successfully synthesized and fabricated. For this end , we synthesized a series of jute-derived nanoporous carbon (JW-NC) samples with different KOH/C ratios (i.e., 3, 4 and 5), synthesis temperatures (i.e., 700, 800 and 900 °C) and times (i.e., 60, 90 and 120 min). The results indicated that JW-NC nanoadsorbents have been mainly composed of carbon nanofibers, and provided high surface area (up to 2579.55 m2/g) with excellent pore volume (up to 1.50 cm3/g). As experimentally investigated JW-NC nanoadsorbents displayed an extra-high CO2 and H2S adsorption capacity at 1 bar (8.05 mmol/g for CO2 and 17.19 mmol/g for H2S), 10 bar (20.53 mmol/g for CO2 and 29.26 mmol/g for H2S) and 35 bar (30.36 mmol/g for CO2 and 40.41 mmol/g for H2S). The results obtained by the density functional theory (DFT) method showed that the Pyrrolic-N atoms affect the pores significantly and play an important role for gas adsorption in all cases. However, the presence of S atoms around Pyrrolic-N atoms in the pores could change the adsorption mechanisms, from which the chemisorption of H2S (Ead = −336.28 kJ.mol−1) changed interestingly to physisorption (Ead = −23.92 kJ.mol−1) as increased S/N ratio of the adsorbent. To sum up, the high gas adsorption capacity, along with excellent cyclic performance and superior preferential gas adsorption, make JW-NC nanoadsorbents as a viable and cost-effective candidate for large-scale natural gas purification.

A proportional-derivative (PD) fuzzy controller was presented to temperature control of a polycondensation reactor. Synthesis of various polyesters and copolyesters were conducted using devised controller. This controller uses reactor temperature error as well as its derivative. The desired jacket temperature had uncertainty due to be affected by noise and disturbance. This uncertainty is modeled using fuzzy numbers, and a fuzzy trajectory was achieved for desired reactor temperature. Then, a generalized Takagi-Sugeno (GTS) fuzzy controller was designed. An adaptation algorithm was included in the controller. Compared to conventional proportional-integral-derivative (PID) controllers, experimental results presented a very good performance to control reactor temperature of in-situ polymerization of polyesters. Although the PID controller finally controlled the temperature with an accuracy of ±6 °C, the temperature overshoot was around 20°C that could completely degrade the polymer. However, fuzzy PD contro...

A three-step in situ polymerzition method was used to synthesize short-segmented block copolymers of poly(butylene succinate-co-butylene fumarate)/nano hydroxyapatite nanocomposites. The nanocomposites were characterized by 1H NMR and Fourier transform infrared spectroscopy. The bond formed between nanohydroxyapatite and polymer led to a good particle dispersion which was studied using scanning electron microscopy (SEM). The thermal and crystallization properties of nanocomposites were calculated via differential scanning calorimetry and X-ray diffraction, indicating the formation of the complete crystals with two different sizes. Producing nanofiber from nanocomposites was done using the electrospinning method. According to SEM results, nanofibers were continuous and bead-free and those produced from nanocomposites had larger fiber diameter compared to the neat copolyester. In contrast to tensile strength, elastic modulus, hydrolytic degradability, and hydrophilicity of the resulted nanofiber which were ...

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.

Thermal stability and degradation kinetics have been studied for a series of aliphatic-aromatic copolyesters where the terephthalate content was varied between 30 mol-% and 70 mol-%. Succinate, adipate and sebacate were considered as the aliphatic dicarboxylate unit. All copolyesters were synthesized with a perfect random distribution by a thermal transesterification process from the corresponding homopolyesters. A complex degradation was deduced for all copolymers taking into account the increment of the activation energy with conversion. In fact, thermogravimetric curves showed a minor decomposition process in the low conversion region that was more significant for the succinate derivative and specifically for that having the lowest aromatic content. The sebacate derivative was characterized by the presence of an additional and minor decomposition process that took place at the highest conversion. All copolyesters were defined by a major decomposition process, which has similar values of activation energy regardless of the method used to calculate them (e.g. Kissinger, KAS or Friedman methodologies). This decomposition reaction followed a A4 Avrami-Erofeev mechanism when Coats-Redfern and Criado methodologies were applied. In summary, all the studied copolymers thermally decompose following a complex process but in all cases the main degradation step corresponds to a similar degradation mechanism.

In this project we performed a theoretical study of the electrospinning process. The electrospinning process typically consists of two phases. For the first part, we have studied Feng's model (2003) and used Phan-Thien Tanner (PTT) rheological model instead of Giesekus model which was used by Feng. A theoretical model for the jet is derived by using a thin filament approximation, and the resulting differential equations are solved numerically. For the second part of the jet, the basis of the modeling is the bead-spring approach first proposed by Reneker et al. (2000) and we added the evaporation effect to Reneker's model. The three dimensional equations describing the dynamics of the bending of electrospun jets are derived and the calculated behavior is compared with experimental observations of jets.

A combination of elastic poly(butylene succinate-co-ethylene terephthalate) and rigid nano-hydroxyapatite were used to prepare an in-situ synthesized nanocomposite mimicing bone structure. The microstructure, morphology and dispersion of nanoparticles in the nanocomposites were studied using 1H-NMR, SEM and TEM, respectively. Then, electrospinning method was used to produce nanofiber matrix with lowest fiber diameter. Presence of chemical bonds among nanoparticles and polymer leads to the excellent particle dispersion and solution phase stability. SEM results show that continuous and bead-free nanofibers were produced and incorporating nanoparticle slightly increased fibers diameter. Elastic modulus, tensile strength, crystallinity, hydrophilicity and hydrolytic degradability of resulted nanofiber increased with nanoparticle but elongation at break slightly decreased. Proliferation and osteogenic differentiation of human mesenchymal stem cell significantly improved by introducing nanoparticle which indicate that electrospun nanofibers could be used as scaffolds for bone tissue engineering. This article is protected by copyright. All rights reserved.

Bending instability in electrospinning jet motion is the main cause of irregular collection of nanofibers on the collector. This instability forces the jet to go on a conical solenoid like motion, and produce a magnetic field which stabilizes the jet. In this paper, ViziMag software was used to calculate the produced magnetic field through simulating jet motion and investigate some influential parameters including voltage and tip to target distance on field strength. Then, the mechanism of applying external magnetic field in magnetic field-assisted electrospinning (MFAES) was investigated based on the summation of simulated jet magnetic field lines and external magnets drawn by ViziMag software. The magnetic field produced due to electrospinning jet was too small to have any effect on jet alignment but the main cause of alignment in MFAES was collecting the charged jet exactly on the field lines of external magnets which act similar to iron fillings.

Short-segmented block copolymers of poly(butylene succinate-co-butylene fumarate) were synthesized and their crystallinity and crosslinking behavior were investigated. 1H NMR was used to characterize the microstructure and composition of the copolyesters. Molecular weight determination was performed using gel permeation chromatography. Based on the DSC results all copolyesters were crystalline and the degree of crystallinity of the copolymers did not change with butylene fumarate mole fraction due to co-crystallization of the butylene succinate and butylene fumarate groups. Crosslinked copolyesters showed a lower crystallization rate and degree of crystallinity while the crystallization temperature shifted to higher temperatures compared with uncrosslinked copolyesters due to the formation of nucleating agents by crosslinkages. Photo-DSC was used to investigate the crosslinking kinetics for UV-initiated photo-curing. Three kinetics parameters including the rate constant (k) and the orders of the initiation and propagation reactions (m and n, respectively) were determined for the quenched and unquenched copolymers. © 2016 Society of Chemical Industry

New nanocomposites of poly(butylene succinate-co-ethylene terephthalate)/nano hydroxyapatite were synthesized using two-step in situ polycondensation. The composition, microstructure, morphology and dispersion of nanoparticles in the nanocomposites were studied using proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that presence of nano hydroxyapatite catalyzes the reaction and there is a chemical bond between nanoparticles and polymer which leads to a good particle dispersion but it doesn’t affect molecular sequence length. Nanocomposites’ thermal properties evaluated by differential scanning calorimetry (DSC) and X-ray diffraction (XRD), showed that crystallinity and crystallite size slightly decrease with the nanoparticles weight fraction. Moreover, the elastic modulus slightly increases and tensile strength and elongation at break decrease with the nanoparticles weight fraction according to dynamic mechanical thermal analysis (DMTA) and tensile analysis. Introducing nano hydroxyapatite increases the hydrolytic degradability dramatically because of the presence of hydrophilic nanoparticle and lower crystallite size.

There is a need to develop biodegradable polymers with tunable physical, mechanical, and biochemical properties. The objective of this work was to investigate the effect of chain microstructure and fumarate content on material properties of poly(butylene succinate-co-fumarate) (PBS-BF) copolymers synthesized by a three-step method of separate esterification of succinic acid (SA) and fumaric acid (FA) with butylene glycol (BG) followed by polycondensation of bis(4-hydroxy butyl) succinate (BS) and bis(4-hydroxy butyl) fumarate (BF) pre-homopolyesters. The material properties of the synthesized PBS-BF were compared with those of PBSF copolymers synthesized by a two-step method of esterification of SA and FA with BG followed by polycondensation. The synthesized copolymers were pressed and slowly or rapidly cooled into sheets and crosslinked with UV irradiation. The molecular and microstructure of the copolymers were characterized by 1H NMR, viscometry, and wide-angle x-ray diffraction. For a given fumarate fraction, the degree of randomness of PBS-BF copolymers was less than PBSF but PBS-BF degree of randomness increased with polycondensation reaction time of PBS and PBF pre-homopolyesters. The crosslinked copolymers were characterized with respect to gelation, thermal and mechanical properties, and degradation. Melting (Tm) and crystalline (Tc) temperatures of poly(butylene succinate) (PBS) increased by copolymerization with BF and the increase was proportional to the copolymer fumarate fraction. The rapidly-cooled and crosslinked PBS-BF30 copolymer with 30% fumarate fraction had highest modulus of 393 MPa and lowest elongation at break of 1.3% among all copolymers whereas the rapidly-cooled and uncrosslinked PBSF10 copolymer with 10% fumarate fraction had lowest modulus of 303 MPa and highest elongation at break of 160%. The uncrosslinked PBS polymer had 31% weight loss after 24 weeks whereas the slowly-cooled and crosslinked PBS-BF30 copolymer with 30% fumarate fraction had

Nanocomposites of polyamide 66 (PA66) with layered silicate and silica (SiO2) nanoparticles were prepared via in situ interfacial polycondensation method. Hexamethylenediamine (HDMA) and adipoyl chloride (AdCl) were reacted in a two-phase media. Montmorillonite (NaMMT) and silica nanoparticles were added to reacting media. Preparation of PA66 and its nanocomposites were studied using Fourier transform infrared spectroscopy. Dispersion of nanoparticles was studied using X-ray diffraction and transmission electron microscopy. The results show that two structures were achieved using two kinds of nanoparticles. Silica nanoparticles were partially exfoliated, while NaMMT nanoparticles were hybrid intercalated–exfoliated in nanocomposite samples. Thermal properties of samples were investigated by differential scanning calorimetry. The results suggest that crystallinity is heterogeneous in the presence of nanoparticles. Kinetic of crystallization was studied by means of Avrami equation, based on the kinetic parameters, spherulites are produced. Results were reported for nanocomposites containing 2 and 4% of nanoparticles. Avrami equation parameter, n, shows that spherulite crystallization occured in the samples. Addition of nanoparticles decreases n first, then n increases with nanoparticle content.

A novel fibrous polymer electrolyte membrane was produced based on polymethyl methacrylate/polyacrylonitrile (PMMA/PAN) blend. This was achieved through optimization in the loadings of the two polymers and electrospinning method. Consequently, the effect of PMMA on the ionic conductivity was assessed. A quantitative relationship between ionic conductivity and the important parameters including voltage, solution concentration, and PMMA content was determined. The response surface method (RSM) was employed to obtain the quantitative relationship and to determine the ion conductivity of PAN/PMMA electrospun membrane. Analysis of variance technique was used to study the importance of parameters and their interactions. A regression model was applied to determine the most influential factors on the ionic conductivity and to find the maximum ionic conductivity of the electrolyte membrane as an optimal result. The average fiber diameter was in the range of 206–367 nm, and the membranes were associated with high porosities between 50 and 91 %, and the electrolyte uptakes were in the range of 285–460 %. For all samples, the ionic conductivity of gel polymer electrolytes at 25 °C was above the 1 mS/cm. The ionic conductivity changed with the voltage directly and with the solution concentration inversely. According to the results, the ionic conductivity showed its dependency with the PMMA content, increasing with the PMMA content up to 50 % and smoothly decreasing with PMMA further increases. Some important interactions between the parameters were also detected.

The main purpose of this research was the prediction of reverse osmosis (RO) membranes performances, including separation factor, pure solvent flux, and total flux. The modified surface force-pore flow is a mathematical and mechanism base model that has predicated the performances of RO membranes appropriately better than others. The equations of this model are complex and nonlinear, which should be solved by an advanced numerical method eventually. In this research, the radial basic function (RBF) network, which is an exclusive typical of artificial neural network (ANN) and an association of radial functions into a single hidden layer, was implemented for the predication of RO membrane performances. The input data of the network were the parameters of this mathematical model and some experimental data which had been obtained from four different types of RO membranes. About 80% of the total experimental data were implemented for the training of data-set and the remaining 20% were used for the test...

A series of novel random copolymers of poly(butylene succinate-co-ethylene terephthalate) were synthesized and characterized in terms of thermal and mechanical properties, crystallinity and biodegradability. The composition and microstructure of the prepared copolyesters were characterized by 1H NMR and 13C NMR, respectively. It was seen that the PBS sequence length decreases with ethylene terephthalate content. All copolymers are semi-crystalline and crystallinity and crystallite size decrease slightly with the comonomer content up to 10%, but the introduction of 20% comonomer leads to decrease the crystallinity up to 29%. The melting temperature of copolyesters decreases with the comonomer content according to the Baur’s equation that indicates only PBS blocks crystallize and crystallite size is decreased with the comonomer content. It was also investigated that the elastic modulus also decreases slightly with the comonomer content. However, the elongation at break increases by 500% due to the decrease in crystallite size and crystallinity. Incorporating non-biodegradable aromatic comonomer has a little effect on copolyester degradability because of the randomness and lower crystallite size. Open image in new window

Electrospun poly(acrylonitrile) fibrous membrane (PAN-EFM) is prepared and enhanced by adding poly(methyl methacrylate)(PMMA) and subsequently minimizing the average diameter of the PAN/PMMA blend fibers. Electrospinning of the 50/50 wt% PAN/PMMA solution is carried out with the aim of the simultaneous presence of both polymers on the fiber surface. Their presence in exterior surface is confirmed using the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique next to the leaching of PMMA with acetone. The process parameters are optimized in four stable modes with the average diameter decreasing from 445 to 150 nm. Mechanical strength of the membrane is measured and reported. Comparing the sample electrochemical properties of the EFMs reveals that the addition of PMMA increases ionic conductivity from 1.02 to 3.31 mS cm−1 and reduces interfacial resistance from ~1000 to ~400 Ω. It is also demonstrated that the ~300-nm reduction in average diameter of the blend fibers increases ionic conductivity from 3.31 to 5.81 mS cm−1 and reduces interfacial resistance from ~400 to ~200 Ω.

Polyacrylonitrile (PAN)- and polymethylmethacrylate (PMMA)-blended nanofibers produced using electrospinning and mat morphology were studied. The response surface method was exploited to optimize the diameter and its standard deviation of electrospun PAN/PMMA non-woven membranes. The diameter and its standard deviation were related to the solution concentration, applied voltage, and PMMA composition. The morphology of nanofibers was studied by means of field emission scanning electron microscopy. The importance of parameters and their interactions was investigated through the analysis of variance. The nanofibers' diameter increased with solution concentration and decreased with applied voltage. The data showed that the diameter of nanofibers decreased up to 50% with PMMA composition, and then increased with further increase of PMMA composition. Some important interactions between the parameters were detected.

Polyacrylonitrile/poly (vinylidene fluoride) fibrous membranes were prepared by electrospinning of PAN and PVdF solution and were soaked in 1 M lithium perchlorate (LiClO4) in ethylene carbonate (EC)/diethyle carbonate (DEC) (1:1 wt.%) solution in order to prepare polymer electrolyte membranes. Response surface method (RSM) was used to obtain a quantitative relationship between selected electrospinning parameters, i.e., applied voltage, solution concentration, and PVdF content. The measured response is ionic conductivity of electrolyte membranes. The Box–Behnken method was applied to design of experiments. Importance of parameters in the model was determined by analysis of variance (ANOVA). The model was used to find the maximum ionic conductivity of electrolyte membranes as optimum result. The morphology of fibers was investigated by field emission scanning electron microscopy (FESEM). FESEM results show that the PAN/PVdF membrane has interconnected multifibrous layers with ultrafine porous structure that leads to a high ionic conductivity and efficient lithium ion transport. Produced fibrious membranes show uniform morphology. Average fiber diameter lies between 116 and 379 nm, and membranes have high porosity of 48–90 % and electrolyte uptake of 303–493 %. The polymer electrolyte membranes show good ionic conductivity in the order of 10−3 S cm−1 at ambient temperature. Ionic conductivity decreases with increase of solution concentration and increases with increase of PVdF composition. Voltage has no significant effect on ionic conductivity of the membranes. The model predicted the maximum ionic conductivity of 7.98 mS cm−1 when the voltage was set at 21.57 kV, the solution concentration set at 14.02 wt.%, and the PVdF composition set at 69.48 wt.%.

A combination of elastic poly(butylene succinate-co-ethylene terephthalate) and rigid nano-hydroxyapatite were used to prepare an in-situ synthesized nanocomposite mimicing bone structure. The microstructure, morphology, and dispersion of nanoparticles in the nanocomposites were studied using proton nuclear magnetic resonance (

In the present study poly (butylene sebacate- co -terephthalate)s having different compositions were synthesized with a high yield and a random distribution by thermal transesterification of poly (butylene sebacate) and poly (butylene terephthalate) homopolymers. The copolymer with the highest comonomer ratio was the least crystalline sample, although the melting peaks corresponding to both, sebacate and terephthalate-rich phases were still observable in calorimetric heating runs. This copolymer was associated with interesting thermal and mechanical properties, as the maximum melting point was higher than 100 °C and the storage modulus was also high (i.e. 1.1 × 10 9 N/m 2 and 1.7 10 8 N/m 2 were determined just before and after the main glass transition temperature of −12 °C). As all studied samples were thermally stable up to temperatures clearly higher than the fusion temperature, they could be easily processed. Increasing the terephthalate content of the copolymers resulted in higher hydrophobicity, which had a minor influence on cell adhesion and proliferation of both fibroblast-like and epithelial-like cells. Hydrolytic and enzymatic degradability were assessed and the effect of composition and crystallinity on the degradation rate was investigated. Molecular weight measurements during exposure to a hydrolytic media indicated a first order kinetic mechanism during the initial stages of degradation before reaching a limiting molecular size, which was indicative of solubilization. The most amorphous sample appears as a highly promising biodegradable material since it showed a significant weight loss during exposure to all selected degradation media, but also exhibited good performance and properties that were comparable to those characteristic of polyethylene.

Random copolyesters having 1,4-butanediol units were synthesized from a transesterification process between homopolymers constituted by aliphatic dicarboxylates (i.e. succinate, adipate or sebacate) and the aromatic therephthalate derivative, as verified by NMR spectroscopy. Biodegradability of resulting copolyesters was studied via enzymatic hydrolysis using Pseudomonas cepacia lipase at pH = 7.2 and 37 °C. Kinetics of degradation showed that in all cases the degradation rate decreased after 19 days of exposure. The observed glass transition temperatures, T g, of the random copolyesters showed a non-linear dependence on composition, a feature that was explained in terms of the internal stiffening effect of butylene terephthalate units. Copolymers with higher aliphatic (i.e. 50 and 70 mol-%) and methylene (i.e. adipate and sebacate units) contents showed double melting peaks in DSC thermograms. These copolyesters resulted in two different crystalline rich phases after melt-crystallization and subsequent cooling. The ratio between these phases logically depended on the predominant aliphatic or aromatic dicarboxylate content. The copolymers initially crystallized via the aromatic units through a heterogeneous nucleation and a spherulitic growth. The presence of aliphatic dicarboxylate units hindered the beginning of the crystallization process, but the overall growth kinetic constant was similar for all samples. The secondary nucleation constants were determined and showed higher values for samples with higher adipate and sebacate contents.

Composite nanofibers of polyacrylonitrile/multi-wall carbon nanotubes (PAN/MWCNTs) were prepared via electrospinning. Samples contained 0, 0.5, 1, 2, 3, and 3.5 wt% of MWCNTs. The viscosity and electrical conductivity of electrospinning solutions were measured. Results revealed that, with the addition of multi-wall carbon nanotubes, viscosity was increased and electrical conductivity was improved. Rheological behavior was studied using two different viscometers. Moreover, morphology and diameters of the composite nanofibers were studied by scanning electron microscopy (SEM) and nanofiber diameter distributions were presented. SEM micrographs showed that by adding MWCNTs, the average diameter of nanofibers was increased. Furthermore, the effect of MWCNTs on glass transition temperature, T g, was investigated using differential scanning calorimetry (DSC) technique. The results showed that T g was increased with the addition of MWCNTs. In addition, Fourier transform infrared spectroscopy (FTIR) results showed that MWCNTs can affect the orientation ability of polymer chains. The effects of adding salt, increasing voltage and changing the tip-to-collector distance on the morphology and diameters of composite nanofibers were examined. The electrical conductivity results of electrospun mats were measured by a two-probe method. Electrical conductivity was increased by addition of MWCNTs and its behavior followed the percolation theory. Finally, it was observed that mats with smaller diameters have higher electrical conductivity.

Electrospinning of polyacrylonitrile/poly(vinylidene fluoride) (PAN/PVdF) was applied using Box–Benkhen experimental design to obtain a quantitative relationship between selected electrospinning parameters (namely applied voltage, solution concentration, and PVdF composition) and nanofiber diameter and standard deviation of nanofiber diameter. Important parameters in the model were determined by analysis of variance (ANOVA). The model was consequently used to find the optimal conditions that yield the minimum PAN/PVdF nanofiber diameter. The morphology and nanofiber diameter were investigated by field emission scanning electron microscopy (FESM). The range of produced nanofiber diameters was from 116 to 379 nm. It was concluded that the nanofiber diameter tended to increase with solution concentration and decrease with PVdF composition. The applied voltage had no significant effect on the nanofiber diameters. Nanofibers with smaller standard deviation in diameter could be obtained at lower solution concen...

Poly(ethylene terephthalate) (PET) from off-grades of industrial manufacturers was partially and thoroughly depolymerized in order to synthesize PET oligomers and bis(hydroxyethyl) terephthalate (BHET), respectively. Design of experiments and analysis of variance (ANOVA) were applied for optimization of samples. Effects of reaction time, volume of glycol, catalyst concentrations, and particle size of off-grade PET were investigated. The optimal conditions to synthesize PET oligomers (3–8 repeating units) were glycol/PET molar ratio of 1, a weight ratio (catalyst to PET) of 0.5 wt%, using granule-shape. On the other hand, a reaction time of 180 min, a weight ratio (catalyst to PET) of 0.25 wt%, and glycol/PET molar ratio of 5 were obtained as the suitable conditions of BHET production. Then, endcapped PET oligomers, as a compatibilizer for preparing PET nanocomposites, were produced via reaction between maleic anhydride/phthalic anhydride (MA/PhA) composition. The combination of reaction time of 106 min and PhA/MA molar ratio of 0.85 produced the best results based on d-spacing and peak shift of nanocomposite samples. Moreover, the reaction of MA and BHET from glycolyzation of PET was successfully performed at 160°C and 190°C for 8 h. The optimum conditions were compared with a synthesized PET. POLYM. ENG. SCI., 54:417–429, 2014. © 2013 Society of Plastics Engineers

Neat poly(trimethylene terephthalate) (PTT) and PTT/modified organoclay nanocomposite with various amounts of clay were synthesized by a two-step procedure. Terephthalic acid (TPA) was reacted with 1,3-propanediol (1,3-PDO) in the esterification step. Then, polycondensation reaction resulted in the formation of PTT in the presence of tetra buthyl titanate (Ti(OC4H9)4) as a catalyst. Commercially available organoclay (Cloisite 30B) was modified using 3-aminopropyltriethoxysilane via a silylation reaction. Thermal stability of modified clay was studied by means of thermal gravimetric analysis (TGA) that showed 10% less weight loss than Cloisite 30B. PTT/organoclay nanocomposites with 0.5, 1 and 2 wt% of modified organoclay were prepared by in situ polymerization. Synthesized polyesters were characterized by Fourier-transform infrared spectroscopy and proton-nuclear magnetic resonance spectroscopy (1H-NMR). Number average molecular weights were determined by 1H-NMR and a new Mark–Houwink equation is reported for highly pure dichloroacetic acid as solvent at 25°C. Polymer’s morphology was examined with x-ray diffraction and transmission electron microscopy. It was observed that clay layers were not accumulated. Thermal properties and crystallization behavior were investigated by differential scanning calorimetry and TGA. Crystallization temperature ( Tc) of nanocomposites increased about 6°C compared to neat PTT that reflects greater overall crystallization. Modified Averami Equation was used to describe crystallization kinetics and crystal size was studied using polarized optical microscopy. It was observed that crystal size reduces with nanoclay content. PTT mostly is used as polymeric fiber. Hence, dyeability of neat PTT and nanocomposites was investigated using a spectrophotometer. About 32% increase in color uptake was determined.

Poly(ethylene terephthalate) (PET) from off grades of industrial manufacturer was partially and thoroughly depolymerized using excess glycol to synthesize PET oligomers and bis(hydroxyethyl) terephthalate (BHET), respectively. Design of experiments and analysis of variance were applied for optimization of samples. Effects of reaction time, volume of glycol, catalyst concentrations and particle size of off grade PET on the yield of products were investigated based on the design of experiments. Thermal analysis of glycolyzed products is performed by differential scanning calorimetry. The optimum samples were also well characterized by Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy (proton nuclear magnetic resonance spectroscopy and carbon nuclear magnetic resonance spectroscopy). The optimal conditions to synthesize PET oligomers were glycol/PET molar ratio of 2 with no catalyst using granule-shape PET for a 120-min glycolysis reaction time. Desired oligomer repeating units were 3–8. On the other hand, a reaction time of 180 min, weight ratio (catalyst to PET) of 0.25 wt% and glycol/PET molar ratio of 5 were obtained as the suitable conditions of BHET production. Then, end capped PET oligomers, as a compatiblizer for preparing PET nanocomposites, were produced via reaction between maleic anhydride and phthalic anhydride (MA/PhA) composition. The combination of reaction time of 106 min and PhA/MA molar ratio of 0.85 produced the best results based on d-spacing and peak intensity of nanocomposite samples. Moreover, the reaction of MA and BHET from glycolyzation of PET was successfully performed at 160°C and 190°C for 8 h.

Random poly(ethylene-co-1,4-cyclohexylenedimethylene terephthalate) and poly(ethylene-co-1,4-cyclohexylenedimethylene terephthalate)/organoclay nanocomposites were synthesized via in situ polymerization of terephthalic acid, ethylene glycol, 1,4-cyclohexane dimethanol, and aminosilane-modified Cloisite30B. An amorphous copolyester was produced with incorporating 30 mol% of 1,4-cyclohexane dimethanol in glycol part. Samples were characterized using Fourier transform spectroscopy, nuclear magnetic resonance, 13C-NMR and 1H-NMR, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, thermal gravimetric analysis, and dynamic mechanical thermal analysis. Intrinsic viscosities of samples were in the 0.51–0.55 dL/g range. A commercial organoclay was modified prior to add into the reactor. 1H-NMR and 13C-NMR spectra were applied to determine cis: trans isomer ratio of 1,4-cyclohexane dimethanol in polymer chains, Molar ratio of 1,4-cyclohexane dimethanol: ethylene glycol in polymer chains, degree of randomness, mean length of sequences, Mn, and Mark–Houwinks equation parameters. X-ray diffraction results of nanocomposites, including 0.5 and 1 wt% of organoclay, showed no peak in small angles, hence, modified organoclay presented exfoliated structure in polymer matrix. Differential scanning calorimetry analyses revealed that all samples were amorphous. Oxygen, nitrogen, and carbon dioxide diffusion rates in samples were investigated. Nanocomposite, including 3 wt% of organoclay, has about 60% less permeability in comparison to neat copolyester.