Polyether-segmented nylon hemodialysis membranes. IV. Membrane morphologies and permeability characteristics of dialysis membrane composed of poly(ethylene oxide)-segmented Ny69/M10

Dialysis membrane was prepared by a phase inversion method using a new polyether-segmented nylon which dissolves in common organic solvents such as dimethylsulfoxide. The polyether-segmented nylon contained poly(ethylene oxide) block and nylon block (random copolyamide: Ny69/M10) prepared by sebacic acid, azelaic acid, m-xylenediamine, and hexamethylenediamine. The morphologies and permeability characteristics of the membranes were investigated. It was shown by scanning electron microscope observation that the membrane had a fingerlike structure when dimethylsulfoxide was used as a polymer solvent, and a spongelike structure when an additive such as calcium chloride was added to the polymer solution. The high permeability for the solutes such as urea and vitamin B₁₂ were observed in comparison with the polyether-segmented Ny610 membranes prepared by a phase inversion method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1731–1737, 1997     

Polyether-segmented nylon hemodialysis membranes. II. Morphologies and permeability characteristics of polyether-segmented nylon 610 membrane prepared by the phase inversion method

The relationships between the morphologies and the permeability characteristics as dialysis membrane of polyether-segmented nylon 610 (PE-Ny610) have been investigated. PE-Ny610 used are poly(propylene oxide) (PPO)-segmented nylon 610 containing 25 wt % PPO (PPO-Ny610) and poly(ethylene oxide) (PEO)-segmented nylon 610 containing 15 wt % PEO (PEO-Ny610). The morphologies in the cross section of the membranes exhibit the cellular porous structures due to liquid-liquid phase separation. On the other hand, the structures of the surfaces are mainly composed of the crystalline spherulite due to liquid-solid phase separation. These morphologies are little affected by the composition ratio of the coagulant, calcium chloride/methanol/water mixture. PEO-Ny610 membranes have shown superior membrane performances to the PPO-Ny610 membrane. The effect of PEO content in PEO-Ny610 on the adhesion of platelet onto the PEO-Ny610 film surface was investigated and it is concluded that PEO-Ny610 having > 10 wt % PEO shows a good nonthrombogenicity equal to PPO-Ny610. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1713–1721, 1997     

Synthesis of nylon 6,6 copolymers with aromatic polyamide structure

In this article, flexible nylon 6,6 was reinforced with rigid‐chain aromatic polyamides based on poly(4,4′‐diphenylsulfone terephthalamide) (PSA), poly(p‐diphenyl oxide terephthalamide) (POA), poly(p‐diphenylmethane terephthalamide) (PMA), and isophthaloyl chloride (IPC). Various high molecular weight block copolyamides were synthesized by solution polymerization using p‐aminophenylacetic acid (p‐APA) as a coupling agent. Their thermal properties show that the block copolyamides exhibit higher values of T_g and T_m and better thermal stability than those of nylon 6,6, especially the IPC‐modified nylon 6,6. The order of increased thermal properties of copolyamides is IPC > POA > PMA > PSA. From wide‐angle X‐ray diffraction patterns, it was found that nylon 6,6 has two diffraction peaks, that is, 2θ = 20.5° and 23°, while the multiblock copolymers showed only one at 2θ = 20°, indicating a different crystal structure. It was found that the mechanical properties of the IPC‐modified nylon 6,6 were improved more than those of the semirigid copolyamides. The order of tensile strength was IPC > PSA > PMA > POA, but for elongation, it was POA > PMA > PSA > IPC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2167–2175, 2001     

Polyether-segmented nylon hemodialysis membranes. I. Preparation and permeability characteristics of polyether-segmented nylon 610 hemodialysis membrane

The effect of the coagulation condition in the phase inversion method on the permeability characteristics of poly(propylene oxide) or poly(tetramethylene oxide)-segmented nylon 610 (PPO-Ny610 or PTMO-Ny610) hemodialysis membranes, the stability of the membrane performance, and the mechanical strength were investigated. The polymers were dissolved in a solvent such as formic acid and methanol saturated with calcium chloride, and thus PPO-Ny610 and PTMO-Ny610 membranes were prepared using formic acid and a calcium chloride/methanol/water mixture as a polymer solvent and a coagulant, respectively. It is concluded that PPO-Ny610 membrane has better permeability characteristics than PTMO-Ny610 membrane, and possesses additional properties for hemodialysis membranes such as mechanical properties and permeability stability in the drying and sterilizing processes. Furthermore, the blood compatibilities of PPO-Ny610 and PTMO-Ny610 membranes were superior to regenerated cellulose membranes on the basis of the result of platelet adhesion test. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1703–1711, 1997     

Phase inversion membranes with an organized surface structure from mixtures of polysulfone and polysulfone—poly(ethylene oxide) block copolymers

Phase inversion precipitation of a polysulfone and polysulfone—poly(ethylene oxide) block copolymer solution yields a membrane with an organized surface structure. The poly(ethylene oxide) block of the polysulfone—poly(ethylene oxide) block copolymer segregates to the surface of the membrane. Measurement of the ¹H T_1ρ of the component materials, X-ray photoelectron spectroscopy, and differential scanning calorimetry reveal the organized surface structure of the membrane. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1353–1358, 1997     

Toughening of nylon 6 with grafted rubber impact modifiers

Recent work has shown that nylon 6/acrylonitrile–butadiene–styrene (ABS) blends can be made tough by the addition of some polymer additives that are chemically reactive with nylon 6 and physically compatible with the styrene-acrylonitrile copolymer (SAN) phase of ABS. Imidized acrylic polymers (IA) represent a successful example of such additives that improve the dispersion of ABS in the nylon 6 matrix and render the blends tough. This article examines the possibility of toughening nylon 6 with ethylene/propylene/diene elastomer grafted with SAN copolymer (EPDM-g-SAN). This EPDM-g-SAN consists of 50% rubber and 50% SAN by weight. However, it was found that the same IA that works well to disperse ABS materials of similar rubber content is not as effective for EPDM-g-SAN, primarily because the EPDM forms the continuous phase, not SAN, and, thus, interfaces with nylon 6 during melt blending. Maleated elastomers like maleic anhydride grafted ethylene–propylene copolymer (EPR-g-MA) and styrene–(ethylene-co-butylene)–styrene triblock copolymer (SEBS-g-MA) were more effective for dispersing EPDM-g-SAN in the nylon 6 matrix than IA. Various mechanisms that improve the dispersion are discussed. © 1995 John Wiley & Sons, Inc.     

Investigations on nylon 4 membranes. Synthesis and transport properties. I. Synthesis of nylon 4 polymer

The synthesis of nylon 4 (polypyrrolidone) by the anionic polymerization of 2-pyrrolidone through the use of the CO₂/potassium pyrrolidonate catalyst system for use in preparing polymer membranes for separation purposes was investigated in detail. The effects of the quantity of CO₂, the potassium pyrrolidonate catalyst, and the reaction temperature on the yield and molecular weights of the nylon 4 were studied. At reaction temperatures of 50°C and a reaction time of 120 hr, a yield of 50.9% with intrinsic viscosity of 4.42 (corresponding to M_n of 108,200 and M_w of 135,850) was obtained. The molecular weight distributions of the nylon 4 were determined by gel permeation chromatography (GPC) using m-cresol as the eluting solvent and were found to have a relatively narrow distribution.     

Synthesis and properties of nylon 6 modified with various aromatic polyamides

In this study, flexible nylon 6 was reinforced by the following rigid-chain aromatic polyamides: poly (m-phenylene isophthalamide) (PmIA), poly(4,4′-diphenylsulfone terephthalamide) (PSA), poly( p-diphenyloxide terephthalamide) (POA), and poly(p-diphenylmethane terephthalamide) (PMA). Various high-molecular-weight block copolyamides were synthesized by solution polymerization using p-aminophenylacetic acid (p-APA) as a coupling agent. Their thermal properties have shown that the block copolyamides exhibit higher T_g and T_m and better thermal stability than those of nylon 6, especially PmIA-modified nylon 6. The order of their thermal properties of aromatic modified nylon 6 copolyamides is PmIA > PMA > POA > PSA. Besides, the T_g and T_m of multiblock copolyamides are higher than those of triblock copolyamides. From the wide-angle X-ray diffraction pattern, it is found that the triblock copolyamides have two diffraction peaks (i.e., 2θ = 20.5 and 24°). However, the multiblock has only one at 2θ = 20°, indicating a different crystal structure for multiblock copolyamides. This can be further confirmed from scanning electron microscopy. It shows that the triblock copolyamides are a dispersed phase structure, although the multiblock copolyamides exhibit a homogeneous texture rather than an aggregated one. For the mechanical properties, it is found that the multiblock copolyamides have a more significant reinforcing effect than the triblock copolyamides. Also, the order of their physical properties of aromatic modified nylon 6 copolyamides, such as tensile strength, is PmIA > PMA > POA > PSA; but for the elongation, the order is PSA > POA > PMA > PmIA. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1031–1043, 1998     

Carbon dioxide/ethane mixed-gas sorption and dilation in a cross-linked poly(ethylene oxide) copolymer

Mixed-gas CO₂/C₂H₆ sorption and dilation in a cross-linked poly(ethylene oxide) copolymer were studied at temperatures ranging from −20 to 35 °C. The polymer was prepared by photopolymerization of a solution containing 70 wt.% poly(ethylene glycol) methyl ether acrylate (PEGMEA) and 30 wt.% poly(ethylene glycol) diacrylate (PEGDA). Four different gas mixtures (10, 25, 50 and 70 mol% CO₂) were considered at operating pressures up to 21 atm. At a given temperature, polymer dilation increased with pressure and CO₂ content. Compared to pure-gas values, CO₂ solubility was higher in the presence of ethane, an effect whose extent increased with decreasing temperature. Ethane solubility in the polymer also increased in the presence of CO₂ compared to the pure-gas value at T ≥ 25 °C. However, at T ≤ 0 °C, the presence of carbon dioxide initially reduced ethane solubility. As the fugacity of CO₂ in the mixture increased and the polymer dilated, ethane solubility progressively increased, eventually surpassing the pure-gas value. The multicomponent Flory-Huggins model could describe the pure- and mixed-gas data simultaneously, provided that an empirical composition dependence was included in the interaction parameters for T < 25 °C.     

Comparison of the toughening effects of different elastomers on nylon 1010

The toughness of three different elastomer‐toughened nylon 1010 blends was investigated via standard notched Izod impact test and single edge notched three‐point bending test. The toughness of nylon 1010 blends varies much with different elastomer types and components. All three kinds of nylon/elastomer/maleated‐elastomer blends showed high impact strength (over 50 kJ m^?2) as long as at appropriate blending ratios. With increasing maleated elastomer content, brittle‐ductile transition was observed for all three kinds of elastomer‐toughened nylon 1010 blends. The number average dispersed particle size (d_n) of ethylene‐1‐octene copolymers or ethylene‐vinyl acetate copolymers toughened nylon 1010 blends significantly decreased from over 1 to 0.1 μm with increasing corresponding maleated elastomer content. Investigation on the fracture toughness showed the dissipative energy density gradually increased with decreasing d_n, while the limited specific fracture energy increased with increasing d_n when d_n was below 1 μm and then sharply decreased with further increasing d_n. The energy consumed in the outer plastic zone was the main part of the whole energy dissipated during the fracture process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Water effect on the morphology of EVOH copolymers

The effect of water on the morphology of four ethylene vinyl alcohol copolymers (EVOH) with different ethylene contents was studied by differential scanning calorimetry (DSC). EVOH film samples equilibrated in controlled atmospheres at different relative humidities (RH) and 23°C were analyzed. Under dry conditions, the glass transition temperature (T_g) was unaffected by copolymer ethylene content. As RH increases, T_g decreases. It seems that the presence of water within the polymer matrix results in plasticization of the polymer. T_g varies from around 50°C (dry) to below room temperature. EVOH copolymers are glassy polymers when dry and rubbery polymers at high RHs. Fox and Gordon–Taylor's equations well describe T_g depletion at low water uptake, although severe water gain results in a considerable T_g decrease, which is not predicted by these theories. Melting temperature, T_m, and enthalpy, ΔH_m, were also analyzed. When dry, T_m decreases as ethylene content increases. No significant water effect was found on either T_m or ΔH_m. Hence, crystallinity seems to be unaffected by water presence. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1201–1206, 1999     

Synthesis and properties of an electroactive alternating multi‐block copolymer of poly(ethylene oxide) and oligo‐aniline with high dielectric constant

A novel electroactive polymer that has alternating oligo‐aniline and flexible poly(ethylene oxide) segments in the main chain has been synthesized through oxidative coupling polymerization. The chemical structure of the electroactive copolymer was confirmed using Fourier transform infrared and NMR spectroscopy measurements. The electrochemical activity of the copolymer was tested in 1.0 mol L^?1 H₂SO₄ aqueous solution and it shows two redox peaks. Moreover, the thermal properties of the copolymer were investigated using thermogravimetric analysis. The copolymer obtained has good solubility in some common organic solvents. The most important properties of the copolymer are its dielectric ones, which were also investigated. It has a very high dielectric constant at room temperature. Copyright © 2010 Society of Chemical Industry     

Determination of plasticizers efficiency for nylon by molecular modeling

Polyamides are semicrystalline polymers useful in a wide range of applications in the plastics industry. Some applications require higher flexibility and workability of the polyamides, therefore, plasticizers are added to ease compounding and processing procedures and produce the desired product properties. The goal of this study was to estimate plasticizers efficiency in plasticizing Nylon 66/6 copolymer (molar ratio 80/20, respectively) using computational tools and to compare the calculated estimations to experimental results. Four plasticizers were studied: glycerin mono stearate, benzene sulfonamide, methyl 4-hydroxybenzoate (M4HB), and diethylhexyl phthalate. Plasticizers efficiency was determined by calculating cohesive energy density, solubility parameters, free volume and interaction intensities of pristine nylon, and the nylon–plasticizer blends. It was found that the efficiency of the plasticizers increases with the degree of interaction intensity between the plasticizer and polymer chains and that M4HB molecules cause the largest changes in free volume. This finding correlates with the experimental results, based on reduction of polymer glass transition temperature (T _g). The highest calculated plasticization efficiency was obtained for M4HB, for which the decrease in T _g was the most significant.     

Studies on crystallization kinetics of nylon 6-polyoxypropylene-nylon 6 copolymers

The crystllization kinetics of anionic-prepared nylon6-poly(oxypropylene) 1000-nylon 6 (NPN) block copolymers containing 1.20 to 8.76 wt% poly(oxypropylene)(POP) were studied. The thermograms of isothermal and nonisothermal differential scanning calorimetry of NPN block copolymers obtained were used for the study. The Avrami equation was used to analyze the isothermal crystallization of NPN nylon block copolymers. The Avrami exponent n obtained in the temperature range of 180 to 200 °C was 2.0 to 2.5. It was not similar to that for nylon 6 reported in literature. The activation energies of crystallization for the nylon block copolymers were smaller than that of nylon 6, and showed a minimum with POP content. The equilibrium melting point increased as the POP content decreased. For the nylon block copolymers with lower POP content, the slopes of T_c vs. T_m plots were higher than the values reported elsewhere. The Ozawa plot was used to analyze the data of nonisothermal crystallization. The obvious curvature in the plot indicated that the Ozawa model could not fit our system well, and there was an abrupt change of the slope in the Ozawa plot at a critical cooling rate.     

Engineering plastics from lignin II. Characterization of hydroxyalkyl lignin derivatives

Several types of hydroxyalkyl lignin derivatives were synthesized from milled wood, organosolv, steam explosion, acid (H₂SO₄) hydrolysis, and kraft lignin with ethylene oxide, propylene oxide, and butylene oxide by either batch reaction in toluene at 180°C using KOH as catalyst, or in aqueous alkali at room temperature. The isolated derivatives were characterized in terms of their chemical structures by H-NMR and FT-IR spectroscopy. Thermal properties were determined by differential scanning calorimetry. Molecular weights were measured by gel permeation chromatography on polystyrene/lignin model compound calibrated high pressure μ-spherogel columns. Solubilities in various organic solvents spanning a solubility parameter (δ) range from 9.3 to 14.5 and a hydrogen bonding index (γ) range from 1.5 to 18.7 were tested using UV₂₈₀ absorption of solutions of up to with degrees of substitution of between 1 and 2.6 (except for ethylene oxide derivatives which were higher) and with lignin contents of around 60%. The drastic reduction of glass transition temperature of between 50° and 100° is explained with increased free volume of the copolymer and with disruption of hydrogen bonds involving especially phenolic hydroxy groups. The greatly enhanced solubility in organic solvents indicates absence of the gel structure typical of network polymers. No molecular breakdown was observed as a consequence of oxyalkylation. The derivatives had molecular weights (M_w) of between 2000 and 50,000 at dispersity factors of between 2.5 and 25. The derivatives seem to constitute useful prepolymers for thermosetting engineering plastics.     

Synthesis of nonionic flocculants by gamma irradiation of mixtures of polyacrylamide and poly(ethylene oxide)

The synthesis of polyacrylamide (PAM) graft poly(ethylene oxide) (PEO) has been investigated and the reaction conditions were varied by gamma irradiation to optimize polystyrene latex flocculation by the copolymers. The effects of the gamma ray dosage, the PEO chain length, the ratio of PEO to PAM, and the crosslinking degree of copolymer were studied. The most effective flocculant was obtained by exposing a mixture of 1.2 wt % PAM (M_w = 5 × 10⁶) and 0.94 wt % PEO (M_w = 5000) to 816 krad of gamma radiation. The resulting copolymer contained 24 wt % PEO. Crosslinking to give insoluble gels was an undesirable side reaction increased with γ-ray dose and decreased with PEO addition. The most effective flocculants contained more than 15 wt % PEO with little crosslinking. The grafting behavior of triblock copolymer, poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (E_mP_nE_m, where m and n are oxyethylene and oxypropylene unit, respectively), onto PAM by gamma radiation was also studied; grafting occurred but effective flocculants were not obtained. © 1994 John Wiley & Sons, Inc.     

Self‐nucleation–induced nonisothermal crystallization of nylon 6 from the melt

The effect of thermal treatment over a wide range of temperature (130–280°C) on the crystallization behavior of nylon 6 was studied by using DSC, FTIR, and polarized light microscope equipped with a hot stage. The crystallization and the subsequent melting behavior of the nylon 6 samples treated at different temperatures (T_s) were classified into four types. When T_s was higher than 236°C or lower than 213°C, the crystallization behavior of nylon 6 was insensitive to the variation of T_s. When T_s was in the range of 213–235°C, the crystallization behavior was sensitive to the change of T_s. The polarized light microscopic experiments have demonstrated that a large amount of tiny ordered nylon 6 segments/cluster persisted when nylon 6 film are heated to 231°C. Consequently, the fastest crystallization speed was observed. As T_s was between 214 and 223°C, both the T_m and the ΔH_m were higher than those of the nylon 6 samples treated at other temperature. The polarized light microscopic investigations have also demonstrated that molten nylon 6 crystallizes by using the un‐molten nylon 6 crystals as nucleation center at 220°C. Crystallization at higher temperature produces nylon 6 with thicker crystalline lamella. The above results are helpful for rational design of thermal treatment procedure to obtain nylon 6 with different crystalline features. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42413.     

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.     

Structure–microhardness correlation in blends of nylon 6/nylon 66 monofilaments

The microstructure (crystallinity, long spacing) and the micromechanical properties (microhardness H) of two series of nylon 6 and nylon 66 monofilaments and their blends were investigated as a function of annealing temperature T_A and uniaxial deformation in a wide composition range. In case of the homopolymers, the gradual rise of microhardness with T_A is interpreted in the light of the increasing values of the crystallinity α and the hardness of the crystals H_c. The depression of the hardness values of the blends from the additive behavior of the hardness of individual components is discussed in the basis of the crystallinity depression of one component by the second one and viceversa. Finally, the influence of drawing and pressing the blends at 130°C which leads to a hardness increase is also explained in the light of an increase in the H_c value of nylon 66 due to orientation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 636–643, 2000     

Butyllithium-initiated anionic synthesis of well-defined poly(styrene-block-ethylene oxide) block copolymers with potassium salt additives

Poly(styrene-block-ethylene oxide) (PS–PEO) diblock copolymers have been synthesized with predictable block molecular weights and narrow molecular weight distributions. sec-Butyllithium-initiated polymerization of styrene was effected in benzene solution followed by ω-end-group functionalization with ethylene oxide to form the corresponding polymeric lithium alkoxide (PSOLi). Block copolymerization of ethylene oxide initiated by the unreactive PSOLi was promoted by addition of dimethylsulfoxide and either potassium t-butoxide, potassium t-amyloxide or potassium 2,6-di-t-butylphenoxide. Although the PS–PEO block copolymer product contained some poly(ethylene oxide) homopolymer, the poly(ethylene oxide) block M̄_n was in good agreement with the calculated value and the molecular weight distribution of the final block was generally narrow (M̄_w/M̄_n ≤ 1.1). The amount of PEO homopolymer was minimized using potassium 2,6-di-t-butylphenoxide rather than potassium t-alkoxides.