The effects of residual polymerization solvent on the physical properties of poly(2‐cyano‐p‐phenylene terephthalamide)

Poly(2‐cyano‐p‐phenylene terephthalamide) (CY‐PPTA) was obtained by the polycondensation of terephthaloyl dichloride and 2‐cyano‐p‐phenylene diamine in the mixture of N‐methyl‐2‐pyrrolidone (NMP) and calcium chloride (CaCl₂). Washing the polymerized product with water and drying at the elevated temperature inevitably left a small amount of polymerization residues which could be eliminated only by additional washing with acetone. The thermogravimetric and ¹H‐/¹³C‐NMR analyses revealed that the residues were largely composed of NMP which existed as a complex with the polymer. The complex was broken up between 200 and 300 °C and evolved 5 wt % of gaseous products, which had an adverse effect on the physical properties of as‐spun CY‐PPTA fibers obtained by dry jet‐wet spinning. The heat treatment of the as‐spun fibers including residual NMP exhibited some porous morphology on the fiber surface due to the evolved gases. However, the existence of the residual NMP had little effect on the intrinsic viscosity and liquid crystalline phase behavior of the polymer. Both rheological and optical properties exhibited the critical concentration at 3 wt % with the clear schlieren texture of nematic liquid crystalline phase. The inclusion of residual NMP decreased dynamic viscosity and yield stress. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43672.     

Synthesis and properties of homopolyamide and copolyamides fibers based on 2,6‐bis(p‐aminophenyl)benzo[1,2‐d;5,4‐d′]bisoxazole

A novel aromatic homopolyamide with benzobisoxazole units in the main chain was synthesized with 2,6‐bis(p‐aminophenyl)benzo[1,2‐d;5,4‐d′]bisoxazole and terephthaloyl chloride by low temperature solution polycondensation, the inherent viscosity of which was 1.98 dL/g. The diamine and p‐phenylendiamine with terephthaloyl chloride were used to synthesize the copolyamides. The structures of homopolyamide and copolyamides were characterized by IR spectra, elemental analysis, and wide‐angle X‐ray diffraction. Wide‐angle X‐ray diffraction measurements showed that homopolyamide and copolyamides were predominantly crystallinity. The results of thermal analysis indicated that the thermal stabilities of the copolymer increased with an increase of the molar fraction of benzobisoxazole in the copolymers. The thermal stability of the copolyamides with decomposition temperatures (at 10% weight loss) above 570°C was better than that of poly(p‐phenylene terephthalamide) (PPTA). Fibers of homopolyamide and copolyterephthalamides were spun from lyotropic liquid crystal dope in 100% H₂SO₄. When compared with PPTA fibers prepared under the same conditions, the tensile strengths of copolyamides fibers improved by 20–33% with tensile strengths of 1.81 GPa, tensile moduli of 76 GPa, and elongations at break of 3.8–4.1%, which indicated that copolyamides fibers had outstanding mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New block copolymers. 1. Synthesis and characterization of an (a–b)n type block copolymer

A new (A–B)_n type block copolymer has been synthesized by polycondensation of acidchloride terminated poly(ethylene-terephthalate) with amine-terminated butadiene acrylonitrile rubber (ATBN). The acid chloride terminated poly(ethylene-terephthalate) was synthesized by reacting terephthaloyl chloride with ethylene glycol using N,N-dimethyl formamide as the solvent. The resulting polymer was characterized by nitrogen analysis, IR and NMR spectroscopy. The solubility characteristics, solution viscosity behaviour, crystallinity, and phase characteristics of the polymer have been studied.     

Mesomorphic polyblends of poly(p-phenylene terephthalamide) and poly(4,4′-terephthanilide adipamide)

A simultaneous dissolution of two lyotropic polyamides, poly(p-phenylene terephthalamide) (PPTA) and poly(4,4′-terephthanilidc adipamide) (PTAd), in a concentrated H₂SO₄ (1 to 1.5% wt) produced an isotropic single phase solution. The crystallinity of PPTA/PTAd blends confirmed formation of a mesomorphic polyblend to the molecular level. With increasing concentration, solutions of these PPTA/PTAd blends in 100% H₂SO₄ showed a sequential phase change typical of a single lyotropic polymer. Further, the ternary solution exhibited a wider biphase range than both binary solutions of PPTA/100% H₂SO₄ and PTAd/100% H₂SO₄. Dry-jet wet spinning of anisetropic solution of this ternary composition with a PTAd weight fraction less than 0.5 enabled us to obtain PPTA/PTAd blend fibers. Including a PTAd weight fraction of 0.1-0.15 reduced both the orientation angle and fibrillation. The particular blend fiber with a PTAd weight fraction of 0.15 exhibited a synergistic effect on the mechanical properties.     

TPC溶液加料低温溶液缩聚合成PPTA的研究

本文详细研究了采用对苯二甲酰氯(TPC)溶液加料(双溶液法)低温溶液缩聚合成聚对苯二甲酰对苯二胺(PPTA)的各种工艺条件对产物对数比浓粘度的影响。结果表明,盐的用量、吡啶的用量和单体浓度与TPC粉末加料具有相同的规律性。由于TPC溶液加料工艺的影响,单体摩尔比、TPC分步加料的使用、溶液放置时间及溶剂在TPC和对苯二胺(PPD)溶液配制时的分配比例等具有其特殊的规律性。在优选的条件下,TPC溶液加料工艺和固体粉末加料工艺一样,可以获得较高对数比浓粘度的PPTA。     

Dynamic rheological properties and microstructures of liquid-crystalline poly(<Emphasis Type="Italic">p</Emphasis>-phenyleneterephthalamide) solutions in the presence of single-walled carbon nanotubes

The rheological properties and microstructures of both poly(p-phenylene terephthalamide)/sulfuric acid(PPTA/H₂SO₄) and poly(p-phenylene terephthalamide)/ single-walled carbon nanotubes/sulfuric acid (PPTA/SWNT/H₂SO₄) dopes were investigated with flat plate rotational rheometer, polarized optical microscope and differential scan calorimeter. The results showed that, the two types of dopes presented typical shear thinning behaviour even at low frequencies, at various temperatures as well as at all polymer concentrations, and that the relationships between complex viscosity and freqency and between zero shear viscosity and weight average molecular weight implied the tight PPTA chain contacts, somewhat the feature of flexible polymer entanglements. The protonation due to concentrated sulfuric acid allowed SWNT to be well dispersed in PPTA/SWNT/H₂SO₄ dopes. At the concentrations of SWNT, approximately over 0.2 wt%, a novel type of single phase nematic liquid crystal was formed. The dopes can be used to fabricate high performance fibers by dry-jet wet spinning process.     

Removal of dyes by poly(p-phenylene terephthamide)/polyvinylidene fluoride hollow fiber in-situ blend membranes

In order to obtain the compatible poly(p-phenylene terephthalamide) (PPTA)/polyvinylidene fluoride (PVDF) blend membranes, the casting solution was synthesized via the in situ polycondensation process and flat sheet blend membranes were successfully prepared through the immersion precipitation phase inversion method in our previous study. In this study, the polycondensation solution was directly used as the spinning dope to fabricate PPTA/PVDF hollow fiber in-situ blend membrane by the dry-wet spinning technique. Hollow fiber membranes were employed to remove the dyes including Congo red (CR) and methylene blue (MB) from the dyeing liquor. Effects of operation conditions on dye rejection and membrane water flux were investigated. With the increase of operation pressure, feed concentration and feed temperature, dye rejection rates gradually decreased, but the rejection value of CR and MB still remained above 99.5%. On the contrary, the permeation water flux basically increased. During the continuous dye filtration of 300 min, hollow fiber membrane can maintain high dye rejection rates and stable water flux. The combination method of physical backwashing and chemical cleaning can effectively alleviate membrane fouling and recover membrane water flux. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48569.     

Polymer composite of rigid and flexible molecules: Blend systems of poly(p-phenylene terephthalamide) and ABS resin

Homogeneous coagulant of poly(p-phenylene terephthalamide) (PPTA) and ABS resin was obtained by pouring the dimethylsulfoxide solution of N-sodium PPTA and ABS into acidic water. Transmission electron microscopic observation proved that PPTA was dispersed in the matrix in a form of microfibril with a diameter of 10–30 nm. The T_g of the resin component in ABS shifted to higher temperatures with increasing fraction of PPTA. Stress-strain behavior of the polymer composite showed increased tensile modulus and strength with addition of PPTA. The transition temperature from brittle to ductile fracture, however, shifted to higher temperature resulting in lower extensibility. Incorporation of the block copolymer of PPTA and polybutadiene into ABS improved the ultimate extensibility, i.e., increased toughness was provided compared with the simple composite systems of ABS and PPTA microfibrils. Scanning electron microscopic observation showed that the polymer composite made with the block copolymer generated many crazes upon deformation, while the composite with PPTA homopolymer fractured without remarkable craze formation. Thus, a new type of thermoplastic with improved mechanical properties was obtained by use of PPTA block copolymer as compatibilizer.     

Synthesis and characterization of novel optically active poly(amide–imide)s containing N,N′‐(pyromellitoyl)‐bis‐L‐valine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) was reacted with L ‐valine in a mixture of acetic acid and pyridine (3:2) at room temperature, and then was refluxed at 90–100 °C, N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid was obtained in quantitative yield. The imide–acid was converted to N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid chloride by reaction with thionyl chloride. Rapid and highly efficient synthesis of a number of poly(amide–imide)s was achieved under microwave irradiation using a domestic microwave oven by polycondensation of N,N′‐(pyromellitoyl)‐bis‐L ‐valine diacid chloride with six different derivatives of 5,5‐disubstituted hydantoin compounds in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. A suitable organic medium was o‐cresol. The polycondensation proceeded rapidly, compared with conventional melt polycondensation and solution polycondensation and was almost completed within 8 min, giving a series of poly(amide–imide)s with inherent viscosities in the range 0.15–0.36 dl g^?1. The resulting poly(amide–imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, elemental analysis, inherent viscosity (η_inh) measurements, solubility testing and specific rotation measurements. The thermal properties of the poly(amide–imide)s were investigated by using thermogravimetric analysis. Copyright © 2004 Society of Chemical Industry     

High strength and high toughness aromatic polyamide fiber. I. Preparation and properties of block poly(p-phenylene and 4,4′-diphenyl ether terephthalamide) fiber

High strength and high toughness organic fibers can be prepared by molecular design of a suitable block copolymer with mixed segment of rigid and flexible molecular chains. In this paper, the synthesis of fiber forming high molecular weight block copolymer of poly(p-phenylene terephtalamide) (PPTA) and poly(4,4′-diphenyl ether terephthalamide) (DPETA) was studied by the low temperature solution polycondensation method. The high molecular weight block copolymer could be obtained in the mixed solution of 1,3-dimethyl1-2-imidazolidone (DMI) and N,N′-dimethyl acetamide (DMAc) in the presence of triethylamine. The copolymer structures were characterized by elemental analysis and IR spectra. The thermal stability of the block copolymer was better than that of PPTA homopolymer and the ordered copolymer. The wet spinning of the block copolymer was performed using the reaction solution as the spinning dope. The maximum tensile strength and elongation were observed for the filament containing 50% PPTA. The block copolymer had high strength and high Yound's modulus but had a low elongation compared with the ordered copolymer.     

Viscosity of polystyrene solutions expanded with carbon dioxide

The viscosity of solutions of polystyrene (PS) in decahydronaphthalene (DHN) was measured in the presence of carbon dioxide (CO₂) with a moving‐piston viscometer. The effects of the CO₂ pressure (0–21 MPa), polymer concentration (1–15 wt %), temperature (306–423 K), and polymer molecular weight (126 and 412 kDa) on the viscosity were investigated. In the absence of CO₂, the increase in the viscosity with increasing polymer concentration was approximately exponential in concentration and was well described by the Martin equation. All the data fell on a single line when the relative viscosity was plotted against cM^0.50 (where c is the concentration of the polymer in solution and M is the molecular weight of the polymer). The viscosity of the polymer solution decreased with increasing CO₂ pressure under otherwise constant conditions. For a given CO₂ pressure, the viscosity reduction was greatest when the relative viscosity was high in the absence of CO₂, that is, for high‐molecular‐weight polymer, high polymer concentrations, and low temperatures. Reductions in the relative viscosity of almost 2 orders of magnitude were observed in some cases. The viscosity of solutions of PS in DHN also was measured in the presence of sulfur hexafluoride (SF₆). At a given pressure, SF₆ was about as effective as CO₂ in reducing the solution viscosity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 540–549, 2006     

Synthesis and properties of aromatic polyesters and brominated polyesters derived from α,α′-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene

The interfacial polycondensation technique was used for the preparation of polyarylates and brominated polyarylates. Polyarylates and brominated polyarylates were prepared by mixing a solution of diacid chloride such as terephthaloyl chloride, isophthaloyl chloride, or their mixture in dichloromethane with an aqueous alkaline solution of ,-bis(4-hydroxyphenyl)-1,4(or 1,3)-diisopropylbenzene or ,-bis(4-hydroxy-3,5-dibromophenyl)-1,4(or 1,3)-diisopropylbenzene using triethylbenzylammonium chloride as the phase transfer agent. Moderate to high molecular weight polyarylates with _inh up to 1.27 dL/g were obtained, and most of them could be cast into tough and flexible films depending on the polymer composition. In general, polymers containing more 1,3-isomer or isophthaloyl chloride moieties gave transparent and flexible films and had lower glass transition temperatures and higher solubility. Although these polymers have two isopropylidene linkages in their repeating units, they still exhibit moderately high thermal stability and show no obvious weight loss before 400 °C. The introduction of bromine on the polymer backbone caused a decrease of inherent viscosity, crystallinity, and thermal stability of the polyarylates, while causing an increase in glass transition temperature and a great enhancement of fire retardancy.     

Facile synthesis of novel optically active poly(amide‐imide)s containing N,N′‐(pyromellitoyl)‐bis‐l‐phenylalanine diacid chloride and 5,5‐disubstituted hydantoin derivatives under microwave irradiation

Pyromellitic dianhydride (1,2,4,5‐benzenetetracarboxylic acid 1,2,4,5‐dianhydide) (1) was reacted with L‐phenylalanine (2) in a mixture of acetic acid and pyridine (3 : 2) at room temperature, then was refluxed at 90–100°C and N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid (3) was obtained in quantitative yield. The imide‐acid (3) was converted to N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid chloride (4) by reaction with thionyl chloride. Rapid and highly efficient synthesis of poly(amide‐imide)s (6a–f) was achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of N,N′‐(Pyromellitoyl)‐bis‐L ‐phenylalanine diacid chloride (4) with six different derivatives of 5,5‐disubstituted hydantoin compounds (5a–f) in the presence of a small amount of a polar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly, compared with the conventional melt polycondensation and solution polycondensation, and was almost completed within 10 min, giving a series of poly(amide‐imide)s with inherent viscosities about 0.28–0.44 dL/g. The resulting poly(amide‐imide)s were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of FTIR spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility test and specific rotation. Thermal properties of the poly(amide‐imide)s were investigated using thermal gravimetric analysis (TGA). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 516–524, 2004     

A study of interfacial polycondensation in a continuous reaction system

A study was made of the interfacial polycondensation of nylon 6–10 in a continuous reaction system since no previous detailed work of this type was reported in the literature. An experimental stirred-flow reactor was used to determine both yield and intrinsic viscosity (molecular weight) as functions of reactant ratio (sebacoyl chloride/hexamethylenediamine) and Reynolds number. It was found that mass transfer was the controlling factor in the reaction system. The yield as a function of Reynolds number correlated directly with the behavior of mass transfer coefficient. In addition, reactant ratio effects on yield were shown to relate to change in organic phase volume. Intrinsic viscosity was a maximum in the same reactant ratio range as for batch and continuous cascade systems studied earlier. Intrinsic viscosity behavior was also shown to relate to mass transfer. The j_D data for the reactor systems were also determined. These values were shown to correlate if normalized for reactant ratio.     

Synthesis of some new polyhydrazides by direct polycondensation in ionic liquid and their metallization through transition metal complexation

A series of new polyhydrazides has been synthesized via direct polycondensation of benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxylic acid (BBDA) with dihydrazides in ionic liquids (ILs) as a new class of solvents, which have interesting properties, such as nonvolatility, high ionic concentration, good thermal stability, and nonflammability. Direct polycondensation is successfully proceeded in ILs and triphenyl phosphite (condensing agent) without any additional extra components, such as LiCl and pyridine, using in similar reactions in ordinary (IL can act as both solvent and catalyst). The polyhydrazides have been obtained in quantitative yield and their intrinsic viscosities ranged from 0.21 to 0.47 dL g^?1. The polyhydrazides were characterized by means of IR, ¹H‐NMR, inherent viscosity (η_inh), solubility test, TGA, DSC, CHN analysis, and ultraviolet λ_max. They could be thermally converted into the corresponding poly(1,3,4‐oxadiazole)s approximately in the region of 210–330°C, as evidenced by the TGA thermograms. The polymers were readily soluble in several organic polar solvents, such as DMAc, N,N‐dimethylformamide, dimethylsulfoxide, N‐methyl‐2‐pyrrolidone and could be cast into flexible films. The polymer were metallized via complexation with various transition metal. The complexes were investigated by X‐ray diffraction, IR, and UV spectrophotometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal study on phenyl,hepta isobutyl‐polyhedral oligomeric silsesquioxane/polystyrene nanocomposites

A comparative study concerning the thermal stability of polystyrene (PS) and three polyhedral oligomeric silsesquioxane/polystyrene (POSS/PS) nanocomposites of formula R₇R′(SiO_1.5)₈/PS (where R = isobutyl and R′ = phenyl), at various (3, 5, and 10%) POSS concentration was carried out in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of POSS and the experimental filler concentration in the obtained compounds, determined by ¹H NMR spectroscopy, was in all cases slightly higher than that in the reactant mixtures. Inherent viscosity (η_inh) determinations indicated that the average molar mass of polymer in the nanocomposites was practically the same than neat PS and were in agreement with calorimetric glass transition temperature (T_g) measurements. The temperature at 5% mass loss (T_5%) and the activation energy (E_a) of degradation process of synthesized nanocomposites were determined and compared with each other and with those of unfilled PS. On the basis of the results from thermal and IR spectroscopy characterizations, nanocomposite with 5% of molecular filler appears the most thermally stable. The results were also compared with literature data on similar PS‐based nanocomposites. POLYM. COMPOS., 2013 © 2013 Society of Plastics Engineers     

Novel optically active poly(amide‐imide)s with tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine moieties by microwave‐assisted polycondensation

Rapid and highly efficient synthesis of novel poly(amide‐imide)s (PAIs) were achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4′‐carbonyl‐bis(phthaloyl‐L ‐alanine) diacid chloride [N,N′‐(4,4′‐carbonyldiphthaloyl)] bisalanine diacid chloride (1) with six different derivatives of tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine compounds (2a–2f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly and was almost completed within 10 min, giving a series of PAIs with inherent viscosities of about 0.25–0.45 dL/g. The resulting PAIs were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility test, and specific rotation. Thermal properties of the PAIs were investigated using thermogravimetric analysis. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2416–2421, 2001     

Electrically conductive composite of polyaniline and poly (p-phenylene/diphenyl ether-terephthalamide)

In order to improve the flexibility and the anti-static properties of poly-(p-phenylene-terephthalamide) (PPTA), the copolymer of p-phenylene diamine, p,p′-diaminodiphenyl ether and terephthaloyl chloride (PPDTA) was synthesized. This copolyamide PPDTA was mixed with electrically conductive polyaniline (PAn) in concentrated sulphuric acid solution, and was processed to form film, or fibre, of the new composite PAn/PPDTA with high strength and good electrical conductivity. The composite is a lyotropic liquid crystalline polymer with electrical conductivity 10^?1 S/cm. The surface morphology of the PAn/PPDTA composite consists of an oriented fibre-like texture.     

Synthesis of novel optically active poly(ester‐imide)s with benzophenone linkages by microwave‐assisted polycondensation

A new simple and rapid polycondensation reaction of 4,4′‐carbonyl‐bis(phthaloyl‐L ‐alanine)diacid chloride [N,N ′‐(4,4′‐carbonyldiphthaloyl)]bisalanine diacid chloride with several diphenols, such as bisphenol‐A, phenolphthalein, 1,8‐dihydroxyanthraquinone, 4,4′‐dihydroxybiphenyl, 1,5‐dihydroxynaphthalene and hydroquinone, in the presence of a small amount of a polar organic medium such as o‐cresol was performed using a domestic microwave oven. The polycondensation reaction proceeded rapidly and was almost complete within 12 min to give a series of poly(ester‐imide)s with inherent viscosities of about 0.35–0.58 dl g⁻¹. The resulting poly(ester‐imide)s were obtained in high yield and are optically active and thermally stable. All the above compounds have been fully characterized by IR spectroscopy, elemental analysis, inherent viscosity (η_inh), solubility test and specific rotation. Thermal properties of the poly(ester‐imide)s have been investigated using thermal gravimetric analysis (TGA). © 2000 Society of Chemical Industry     

聚对苯二甲酰对苯二胺降解性研究

通过测量不同条件下聚对苯二甲酰对苯二胺(PPTA)溶液的比浓对数黏度,分析在PPTA纺丝前可能引起聚合物降解的因素,这些因素包括纺丝液浓度、残余的CaCl2、N-甲基-2-吡咯烷酮、水分和氢氧化钙等,最终得到水分和氢氧化钙对PPTA的降解影响很大,其余影响较小的结论。同时,分析了降解前后聚合物的结构和性能,发现降解结果是部分端胺基被氧化成硝基。