Synthesis and study of some newer polyamides for semipermeable membrane

A series of novel polyamides was prepared by low temperature solution polycondensation of N-(p/m-aminobenzoyl aminoacetyl)-N'-(4/3-aminobenzoyl) hydrazine with different diacid chlorides in dry N,N-Dimethylacetamide (DMAC). The properties of the polyamides for membrane processing were studied with the help of infrared spectra, inherent viscosity, differential thermal, and thermogravimetric analysis. The inherent viscosities were measured in concentrated sulfuric acid at 25±5°C and were in the range of 0.35–0.89 dL/g. The thermogravimetric data in air indicate that the initial decomposition temperature was in the range of 175–200°C. The polymer melt temperature (T_m) and glass transition temperature (T_g) were in the range of 230–450°C and 153.3–300°C, respectively.     

Nucleophilic Displacement Polymerlzation of N,N'-BIS(p-Chlorobenzylidine)-4, 4'-Diaminodiphenyl Ether with Sodium Sulfide

A novel poly(Schiff-base sulfide) polymer was synthesized by nucle-ophilic displacement polymerization of N,N'-bis(p-chlorobenzylidine)-4, 4'-diaminodiphenyl ether with sodium sulfide in anhydrous condition. The resulting polymer was soluble in some aprotic solvents having inherent viscosity of 0.18 dL/g in dimethylacetamide at 30°C. The monomer and the polymer were characterized by elemental analysis, infrared, and ¹H NMR (nuclear magnetic resonance) spectroscopy. The thermal characteristics of the polymer were also studied by thermo-gravimetric analysis and differential scanning calorimetry. The temperature of 10% weight loss, glass transition temperature (T _g). and crystalline melting point (T _m) of the polymer were found to be 420, 91.89, and 38575°C respectively.     

Enhancement of the mechanical properties and thermostability of poly(vinyl alcohol) nanofibers by the incorporation of sodium chloride

The mechanical properties and thermostability of poly(vinyl alcohol) (PVA) nanofiber mats have been obviously improved by the incorporation of sodium chloride (NaCl). The tensile properties including tensile strength and modulus of membranes with an addition of 1.0 wt % NaCl increased from 2.51 to 4.22 MPa and 33.0 to 176.30 MPa, respectively, more than 160 and 700% of those of the electrospun pure PVA membranes. Moreover, thermogravimetric analysis showed that the initial decomposition temperature (T_i) and the half decomposing temperature (T_50%) of PVA nanofibers with the addition of NaCl were at least 26 and 59 °C higher than that of pure PVA nanofibers, respectively, indicating a strong interaction between the PVA and the salt ions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45981.     

Synthesis of highly refractive and transparent poly(arylene sulfide sulfone) based on 4,6-dichloropyrimidine and 3,6-dichloropyridazine

A highly refractive and transparent poly(arylene sulfide sulfone) (PASS) containing pyrimidine (or pyridazine) unit has been developed. The polymer was prepared by a polycondensation reaction of 4,4′-dimercaptodiphenyl sulfone (DMDPS) and 4,6-dichloropyrimidine (DCPM) (or 3,6-dichloropyridazine (DCPD)). They showed good thermal stabilities such as a relatively high glass transition temperature of 193–202 °C and a 5% weight loss temperature (T_5%) of 370–372 °C. The optical transmittance of the polymer at 450 nm is higher than 81%. The heterocycles unit and plural –S– linkages provides the polymer with a high refractive index of 1.737–1.743 at 633 nm and a low birefringence of 0.003–0.004.     

Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester

Interpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N₂ (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T_5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (T_max) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min^?1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure. © 2003 Society of Chemical Industry     

Thermal degradation of polymethacrylic ester containing bisphenol-S

Thermal degradation of polymethacrylic ester containing bisphenol-S, poly(BPS-M), was investigated under nitrogen and air atmosphere at various heating rates. Ozawa's method was used to calculate the kinetic parameters, activation energy, preexponential factor and reaction order. Thermodegradation of the polymer occurs in one or two stages in nitrogen and air, respectively. The temperature at the start of intense degradation (T_start) and the temperature corresponding to a 50% mass loss (T_50%) were found to be 300 and 402°C, respectively, at a heating rate of 10°C min^?1 in nitrogen. Larger sample masses have a larger temperature interval (ΔT) and a greater mass loss (ΔW). The kinetic order of degradation is unity both in nitrogen and air. The direct pyrolysis mass spectrum of the polymer shows one degradation peak. The most important degradation process under inert atmosphere is the loss of carbon dioxide, phenol and sulphur dioxide. A possible mechanism for thermal decomposition of poly(BPS-M) is proposed based on the product analyses.     

Influence of polymerization conditions on the viscosity and yield of poly(phenylene sulfide ether)

High molecular weight poly(phenylene sulfide ether) (PPSE) was successfully synthesized by reaction of 4,4′‐dihydroxy diphenyl sulfide with 4,4′‐dichloro diphenyl sulfide in N‐methyl‐2‐pyrrolidone (NMP). The influence of polymerization conditions on the intrinsic viscosity and yield of PPSE was investigated and the optimized reaction condition was concluded. Reactions at about 180°C for 6 h along with sodium benzoate as an additive and monomer concentration of 0.588 mol/L NMP were found to produce the highest intrinsic viscosity (0.55 dL/g). Longer reaction time and/or higher temperature reduced the intrinsic viscosity and yield of the resulting product, probably due to side reactions, such as reductive dehalogenation and chemical degradation. X‐ray diffraction indicated that the polymer possessed of orthorhombic cell and had a high crystallinity of 65.8%. The high molecular weight PPSE is a crystalline polymer with T_m of 252°C and T_mc of 224°C. The polymer shows good chemical resistance, but is soluble in organic amide, halo‐hydrocarbon and oxohydrocarbon solvent at a temperature over 150°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of proton exchange membranes by radiation-induced grafting of alpha methyl styrene–butyl acrylate mixture onto polyetheretherketone (PEEK) films

Radiation-induced graft copolymerization of alpha methyl styrene (AMS)–butyl acrylate (BA) mixture onto poly(etheretherketone) (PEEK) was carried out to produce copolymer films which were subsequently sulfonated to develop proton exchange membranes. The characterization of membranes was carried out with infrared spectroscopy (FTIR), differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction analysis (XRD), contact angle and electron probe microanalysis (EPMA). The presence of sulfonic acid groups within the polymer matrix was confirmed by FTIR. The crystallinity of membranes decreased significantly upon sulfonation process. The melting temperature of the membranes also decreased as compared to the virgin and the grafted films. At the same time, glass transition temperature (T _g) of membranes increased as the grafting increased. Virgin film showed stable thermogram up to ~500 °C while the grafted film had two-step degradation pattern. Sulfonation introduced one additional decomposition range in the membrane. Contact angle images showed the hydrophilic nature of the membrane surface. The EPMA showed the presence of the sulphur across the membrane matrix in a homogenous manner. The membranes showed low resistivity of 62 Ω cm for the graft level of 27 %.     

Nitrocellulose-based hybrid materials with T7-POSS as a modifier: effective reinforcement for thermal stability,combustion safety,and mechanical properties

Novel nitrocellulose (NC)-based hybrid materials with self-synthesized heptaphenyltricycloheptasiloxane trihydroxy silanol (T₇-POSS) as a modifier were prepared using a “one-step” chemical cross-linking process. To comprehensively demonstrate the superiority of the modifier, hybrid materials with different contents of T₇-POSS were assessed. The gel content was measured, and the chemical structure and composition of the T₇-POSS-NC hybrid materials were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) results showed that the thermal stability of the T₇-POSS-NC hybrid materials increased with the T₇-POSS content. Typically, when 12.3 wt.% T₇-POSS was incorporated into the NC, the decomposition temperature based on 50% weight loss (T_50%) was delayed from 183.3 °C to 243.5 °C, the maximum weight loss rate (WLR_max) decreased markedly from 432.9%/min to 1.3%/min, and the char residues increased from 1.4% to 26.0%. The scanning electron microscopy (SEM) results of the char residues indicated that the introduction of T₇-POSS led to the formation of a sufficient and compact char layer. Notably, the incorporation of T₇-POSS improved not only the combustion safety according to micro-scale combustion calorimeter (MCC) results but also the mechanical prop-erties due to the formation of cross-linking networks and the good distribution of T₇-POSS particles, which was confirmed by SEM and energy-dispersive spectroscopy (EDS).     

Preparation and characterization of hyperbranched polymer modified montmorillonite/chlorinated butyl rubber damping composites

In this work, Na⁺‐montmorillonite (MMT) was modified by hyperbranched polymer (HBP) and grafted with hindered phenol to improve the damping and other properties of the chlorinated butyl rubber (CIIR) composites. The hyperbranched polymer‐modified montmorillonite (HBP‐OMMT) was prepared by organic montmorillonite (OMMT) that was obtained from the cation exchange reaction between MMT and silane quaternary ammonium salt. The main characterization methods were Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, X‐ray diffraction, scanning electron microscopy, energy dispersive spectrometer, and thermogravimetric (TG) analysis. The basal spacings of MMT, OMMT, and HBP‐OMMT were 1.47, 2.94, and 4.09 nm, respectively. The onset and center temperatures of decomposition (T_?5% and T_max) of HBP‐OMMT were improved from 301 and 369 °C to 332 and 398 °C, respectively. The CIIR damping composites were prepared by mechanical blending of HBP‐OMMT with pure CIIR. The tensile strength and elongation at break of the composites were improved from 5.4 MPa and 890% to 7.6 MPa and 1066%. From TG curves, T_?5% and T_max were increased from 297.4 and 406.0 °C to 323.3 and 410.5 °C, respectively. The dynamic mechanical analysis results showed that tan δ rose from the original 1.20 to 1.44 with the addition of HBP‐OMMT. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43645.     

Preparation of Iron Sulfide Nanomaterials from Iron(II) Thiosemicarbazone Complexes and Their Application in Photodegradation of Methylene Blue

Iron sulfide nanomaterials were prepared by the solvothermal decomposition of two single source precursors i.e. [FeCl₂(cinnamtscz)₂] (1) (cinnamtscz?=?cinnamaldehyde thiosemicarbazone) and [FeCl₂(benztscz)₂] (2) (benztscz?=?benzaldehyde thiosemicarbazone) at different temperatures of 230 and 300 °C in the presence of oleylamine. Powder X-ray diffractometry shows the formation of the pyrrhotite phase at both reaction temperatures. The solvothermal decomposition of [FeCl₂(cinnamtscz)₂] and [FeCl₂(benztscz)₂] at 230 °C produced iron sulfide nanoparticles in the form of spheres. When the temperature was increased to 300 °C, particles in the form of hexagons and nanorods were obtained. Furthermore, the photocatalytic activities of all the four iron sulfide nanomaterials were tested for the degradation of methylene blue under visible light irradiation. Amongst all the materials, nanospheres of iron sulfide obtained by the solvothermal decomposition of [FeCl₂(benztscz)₂] at 230 °C showed the highest photocatalytic efficiency (88.40%).     

A study on high-performance poly(azo-pyridine-benzophenone-imide) nanocomposites via self-reinforcement of electrospun nanofibers

In this study, initially high molecular weight poly(azo-pyridine-benzophenone-imide) (PAPBI) has been fabricated using facile approach. Uniformly aligned electrospun PAPBI and PAPBI/multi-walled carbon nanotube (MWCNT) nanofibers were then produced via electrospinning of desired solutions. Self-reinforcement technique was used to fabricate PAPBI-based nanofiber reinforced films. Uniform dispersion, orientation and adhesion between carbon nanotubes and polymer improved the physical properties of resulting nanocomposites. Fourier transform infrared spectroscopy was used to identify the structures of polymer and self-reinforced nanocomposite films. Scanning and transmission electron microscopy showed that the electrospun PAPBI/MWCNT nanofibers were uniformly aligned and free of defects. Moreover, polyimide matrix was evenly coated on the surface of electrospun nanofibers, thus, preventing the fibers from bundling together. Samples of 1–3 wt% of as-prepared electrospun nanofibers were self-reinforced to enhance the tensile strength of the films. Films of 3 wt% PAPBI/MWCNT nanofiber-based nanocomposite showed higher value in tensile strength (417 MPa) relative to 3 wt% PAPBI nanofibers (361 MPa) reinforced film. Tensile modulus of the PAPBI/MWCNT system was also significantly improved (19.9–22.1 GPa) compared with PAPBI system (13.9–16.2 GPa). Thermal stability of PAPBI/MWCNT nanofibers reinforced polyimide was also superior having 10 % gravimetric loss at 600–634 °C and glass transition temperature 272–292 °C relative to the neat polymer (T ₁₀ 545 °C, T _g 262 °C) and PAPBI nanofiber-based system (T ₁₀ 559–578 °C, T _g 264–269 °C). New high-performance self-reinforced polyimide nanocomposites may act as potential contenders for light-weight aerospace materials.     

Buckypapers of 4,4′-oxydianiline-modified polyvinylchloride and functional nano-filler obtained by resin infusion method

This study provides information on the fabrication and characterization of polyvinylchloride (PVC) buckypaper composite using resin infusion method. PVC modified with 4,4′-oxydianiline (ODA) was infiltrated through buckypapers made of purified multi-walled carbon nanotubes (P-MWCNTs) and functionalized MWCNTs (F-MWCNTs). The increases in P-MWCNT and F-MWCNT contents were investigated on the physical properties of BP-PVC-ODA/PEG (polyethylene glycol)/P-MWCNT and BP-PVC-ODA/PEG/F-MWCNT buckypaper composites. Fourier transform infrared spectroscopy was used for the functional group confirmation which proved the PVC modification and functionality of MWCNTs. The scanning electron micrographs of BP-PVC-ODA/PEG/F-MWCNT showed that intercalation of cross-linked polymer with nanotube produced a polymer-coated F-MWCNT mesh. The maximum degradation temperature (T _max) of functional composite BP-PVC-ODA/PEG/F-MWCNT 0.05 (484 °C) was higher than that of non-functional BP-PVC-ODA/PEG/P-MWCNT 0.05 (473 °C). The glass transition temperature (T _g) of BP-PVC-ODA/PEG/F-MWCNT 0.05 was 225 °C, while BP-PVC-ODA/PEG/F-MWCNT 0.03 yielded a lower T _g of 214 °C. Tensile strength of the functional buckypaper was also found to increase to 37.3 MPa with filler loading. According to X-ray diffraction, the amorphous character of buckypaper showed a trend towards crystal formation with filler loading. P-MWCNT-based buckypaper showed an electrical conductivity up to 4.12 × 10^?1 S/cm; lower than the electrical conductivity of functional buckypaper (1.98 S/cm). The results demonstrated that the resin infusion technique was a successful method to achieve high performance buckypapers compared with F-MWCNTs.     

Polyvinylidenefluoride/Poly(styrene-butadiene-styrene)/Silver Nanoparticle-grafted-Acid Chloride Functional MWCNTs-Based Nanocomposites: Preparation and Properties

A new type of nanofiltration membranes was synthesized using solution blending polyvinylidine fluoride (PVDF) and poly(styrene-butadiene-styrene) with acid chloride-modified multi-walled carbon nanotubes (MWNTs-COCl) and acid chloride-modified nanotbes-grafted-silver nanoparticles (MWNTs-COCl-Ag). SEM of PVDF/SBS-MWCNTs-COCl-Ag nanocomposite membranes showed polymer-coated Ag particles grafted on the surface. Tensile testing depicted the enhanced mechanical stability of PVDF/SBS-MWCNTs-COCl-Ag membranes around 18.8–22.4 MPa relative to PVDF/SBS-MWCNTs-COCl (10.1–13.3 MPa). 0.1 wt.% MWCNTs-COCl-Ag also enhanced the water permeability of membrane. Moreover, acid chloride-modified MWCNTs and Ag nanoparticles enhanced thermal properties to T₀ of 358°C, T₁₀ of 476°C and T_max around 599°C.     

Preparation,analysis, and isothermal crystallization behavior of poly[1,3‐bis(aminomethyl)cyclohexamethylene oxamide]

Poly[1,3‐bis(aminomethyl)cyclohexaneoxamide] (PBAC2) was synthesized using 1,3‐bis(aminomethyl)cyclohexane (BAC) and dibutyl oxalate (DO) via spray/solid‐state polycondensation (SSP). The structure of the synthesized polyoxamide was confirmed by ¹H‐nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy. The weight average molecular weight (M_w) of the polyoxamides prepared was 1.35 × 10⁵. The polyoxamides showed excellent thermal properties with glass transition temperature (T_g) of 150 °C, melting temperature (T_m) of 318 °C, crystallization temperature(T_c) of 253 °C, and initial degradation temperature (T_d) of 417 °C suggesting higher thermal stability than commercial polyamide 6 (T_d = 378 °C). Kinetic studies of PBAC2 predicted a two‐dimensional crystal growth. X‐ray diffraction powder diffraction suggested that the polymer has high crystallinity. A saturated water absorption of 2.8 wt % was recorded for the new polyoxamide, giving it a competitive edge for applications in civil aviation, reinforced plastics, and electronics industry where precise dimensional stability and high thermal resistance properties are a priority. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46345.     

Synthesis and optoelectronic properties of polyimides with naphthyldiphenylamine chromophores

In the previous work, we reported that the β-selectivity, morphology and tensile behavior of isotactic polypropylene (iPP) can be efficiently tuned by the combination of controlling the melt structure status (namely, creation ordered structure by tuning the fusion temperature T_f) and the addition of β-nucleation agent (β-NA, tradename WBG-II, concentration 0.01 wt%), which was called “Ordered Structure Effect” (OSE). This study further investigates the dynamic crystallization and melting behavior of β-iPP with a different melt structure status by differential scanning calorimentry (DSC) and non-isothermal crystallization kinetics. The results revealed that under all the cooling rates studied (2, 5, 10, 20 and 40 °C/min), the crystallization temperature on the cooling curves increased gradually with the decrease of T_f; meanwhile, when the T_f was in the temperature range of 168–186 °C where the OSE occurs (defined as Region II), the crystallization activation energy ΔE was found to be evidently lower, compared with that when the T_f was higher than 186 °C or lower than 168 °C. The results of the subsequent heating showed that the occurrence of the OSE can be observed at all the cooling rates studied; the location of the Region II was constant when the cooling rate varied. Low cooling rate encouraged the formation of more β-phase triggered by OSE. Moreover, the role of OSE on the β-α recrystallization was comparatively studied by tuning the end temperature of recooling (T_end) after held at T_f, and it was found that the OSE encouraged the formation of β-phase with high thermal stability at the low temperature part of Region II, while enhancing the β-crystal with relatively low thermal stability at the high temperature part of Region II.     

Synthesis and characterization of polyurethane rigid foams from polyether polyols with isosorbide as the bio-based starting agent

In this study, with the isosorbide as bio-based starting agent, a series of bio-based polyether polyols with different hydroxyl values were synthesized and used to prepare polyurethane rigid foams (PURF). The structures of as-synthesized polyols were studied by FT-IR and ¹H NMR methods. The thermal properties, mechanical properties, microscopic morphology, thermal conductivity and dimensional stability of PURF have been characterized by several physico-chemical and ASTM methods. The initial decomposition temperature T_5% and the maximum decomposition temperature T_max for PURF from isosorbide-based polyols with 458 mg KOH/g hydroxyl value are about 312 °C and 354 °C, improved 61 °C and 75 °C comparing with the PURF from 1,2-propanediol-based polyols. The maximum compressive strength of PURF from isosorbide-based polyols is 141 kPa, comparing with 118 kPa of PURF from 1,2-propanediol-based polyols. Meanwhile, the dimensional stability of PURF from isosorbide-based polyols has been improved twofold, and the water absorption was obviously reduced by 50%. All these results suggest that polyols of isosorbide-based starting agent should be promising feedstock for PURF with high performance.     

Dielectric relaxations in poly [2,2-propane-bis-(4-phenyl thiocarbonate)]

The dielectric relaxation properties of poly[2,2-propane-bis-(4-phenyl thiocarbonate)] (PTC) have been studied. The existence of crystallinity, which can be eliminated by quenching, is detected. The degree of crystallinity of polymer samples was determined by differential scanning calorimetry in order to investigate the effect of this factor on the dielectric behaviour of this polymer. The thermal degradation of the samples was studied by thermogravimetry. The degradation of the polymer begins before the glass transition temperature T_g. The dielectric spectrum is complex showing several relaxation phenomena. With increasing temperature a γ relaxation can be observed at - 100°C (5 kHz). The activation energy obtained from an Arrhenius plot (lnfvs T^?1) is 6 kcal mol^?1. At 160°C the α relaxation which is associated with the glass transition temperature T_g is detected. The dielectric behaviour of this poly(thiocarbonate) is compared with the corresponding poly(carbonate).     

Synthesis and characterization of electro-optic waveguide material polyurethane-imides

The electro-optic (EO) polymers of Y-type polyurethane-imides (PUI-1 and PUI-2) were synthesized by reaction of monomer azo-based chromophores, phenyl diisocyanate and aromatic dianhydride, based on polycondensation mechanism. Molecular structure characteristics for the polymers were evidenced by ¹HNMR, FTIR, elemental analysis and gel permeation chromatography. The polymers exhibited a glass transition temperature (T_g) of 185 °C and 192 °C and a temperature of 5% weight loss at 256 °C and 325 °C and showed EO coefficient, γ₃₃, of 43 pm/V and 51 pm/V at 1550 nm wavelength. A type of single-mode embedded PUI polymeric inverted rib waveguide Mach-Zehnder (MZ) interferometer electro-optic modulators was fabricated and measured, and exhibiting favorable electro-optical modulation response and the average propagation loss of the waveguide was less than 2.0 dB/cm at 1550 nm. The experimental results indicated that the PUI were promising candidates for the preparation of comprehensive performance excellent EO polymer waveguide materials, due to their large nonlinear optic effects, thermal stability, good processability and low optical propagation loss.     

Role of Electronic Factor in Soot Oxidation Process Over Tunnelled and Layered Potassium Iron Oxide Catalysts

This paper describes the investigations of the catalytic activity in soot oxidation over well-defined iron oxide based materials. The nanostructuration of iron oxide by potassium into tunnelled (KFeO₂) and layered (K₂Fe₂₂O₃₄) ferrites and the surface promotion with CeO₂ results in the marked increase in the catalytic activity (decrease of the ignition temperature down to 210 °C and T _10 % to 310 °C). The measurements of the catalysts work function showed that both nanostructuration and surface promotion with ceria of the best KFeO₂ phase led to increase of the electron availability (decrease of the work function). Strong correlation of the catalytic activity in soot combustion of the Ce–K–Fe–O systems with the work function value was revealed for the first time in the model studies, and can be used as a guideline for optimisation of the real catalytic filters.