Homogeneous alkylation of poly(m-phenylene isophthalamide)

Homogeneous alkylation of poly(m-phenylene isophthalamide) (PMIA) was carried out in N-methyl-2-pyrrolidone. Alkyl halides such as benzyl bromide and allyl bromide were reacted with sodium-metallated PMIA. When the Taft equation was applied to this substitution reaction, the linear relationship was apparently obtained between log k/k₀ and σ^*. The molecular weight of alkylated PMIA decreased by sodium-metallation and alkylation reactions. The weight loss of PMIA derivatives on heating increased with an increasing degree of substitution of the benzyl group, but it was improved by the reaction of the unsaturated alkyl group with 1,2-ethanedithiol.     

Block copolymer of polyurethanes with poly(m-phenylene isophthalamide)

In this study,we modified two kinds of conventional polyurethane (PU) by the low molecular weight diamine-terminated wholly-rigid aromatic polyamide poly(m-phenylene isophthalamide) (PmIA) (Nomex). Two molecular weights (1000 and 2000) of poly(tetramethylene glycol) (PTMG) with 4,4-diphenylene methane diisocyanate (MDI) and with three different ratios of low molecular weight diamine-terminated PmIA prepolymer with different molecular weight of 346, 584, 823 were synthesized to form six PmIA-PU block copolymers. Various block copolymers were also obtained by different ratios of wholly-rigid PmIA prepolymers. Inherent viscosity results indicated that the block copolymers are more viscous than conventional polyurethanes, suggesting that the block copolymers had sufficiently high molecular weights. Moreover, results obtained from differential scanning calorimetry (DSC) and dynamic mechanical properties analysis (DMA) demonstrated that the block copolymers not only exhibited a glass transition temperature (T_g) under 0 °C, but also had a higher storage modulus (E) than those of the conventional PU. Opitical microscopy (OM), phase contrast microscopy (PCM), and transmission electron microscopy (TEM) analyses confirmed that all of the block copolymers had a dispersed phase structure. The mechanical properties, tensile strength and 300% modulus of the block copolymers were found to be better than those of conventional PU.     

Modification of nylon-6 with semirigid poly(p-diphenylmethyl terephthalamide)

In this research, flexible nylon-6 was reinforced by semirigid aromatic polyamide poly(p-diphenylmethyl terephthalamide) (PMA) through physical polyblending and chemical copolymerization using p-aminophenylacetic acid (P-APA) as a coupling agent. From the DSC measurement, it was shown that the T_g of the polyblends was increased with the increase of PMA content. It was discovered that the T_g and T_m of multiblock copolyamides would be higher than those of polyblends and triblock copolyamides. The multiblock copolyamides exhibited a homogeneous texture rather than an aggregated one. Scanning electron microscopy revealed that the polyblends were a dispersed-phase structure. We found that from the wide-angle X-ray diffraction pattern the triblock copolyamides and polyblends had two diffraction peaks, i.e., 2θ = 20° and 24°. However, the multiblock had only one at 2θ = 20°, which evidently indicates that a new crystal structure of multiblock copolyamides was formed. As for the mechanical properties, the multiblock copolyamides were found to have more significant reinforcing effects than those of polyblends and triblock copolyamides. © 1993 John Wiley & Sons, Inc.     

界面缩聚法制备间位芳香族聚酰胺的研究

采用界面缩聚的方法制得了比浓对数粘度较高的聚间苯二甲酰间苯二胺(PMIA)聚合物。对聚合过程中有机溶剂的选择、两种反应单体在各自相中的起始浓度、搅拌速率、缚酸剂的选择等进行了研究。最佳工艺为:以THF为有机溶剂,常温下,CMPD/CIPC比值约为1∶1.1,搅拌速率为750 r/min,以2-甲基吡啶为缚酸剂,制得的聚合物ηinh最大,可达到1.8 dL/g。利用热重法对PMIA的热稳定性进行了分析,结果表明,聚合物具有较好的热稳定性,符合高温使用的要求。     

聚间苯二甲酰间苯二胺平板膜的制备及其性能研究

以聚间苯二甲酰间苯二胺（PMIA）为制膜原料,氯化锂（LiCl）、聚乙二醇（PEG-400）和聚乙烯吡咯烷酮（PVP）为添加剂,通过非溶剂诱导相转化法制备了PMIA平板膜,系统考察了聚合物浓度、添加剂种类和含量对PMIA膜结构和性能的影响。结果表明,聚合物浓度和LiCl含量增加,铸膜液黏度增大,导致膜孔径减小,纯水通量降低。而PEG含量的增加,使得聚合物链呈现舒展状态,膜孔径增大,纯水通量升高,亲水性增强。随着PVP含量的增加,膜的纯水通量先升高后降低,膜的亲水性变差。当PMIA的质量分数为9%,LiCl的质量分数为2.8%,PVP的质量分数为1.2%时,膜的纯水通量高达1421.55 L·m^-2·h^-1·bar^-1,对牛血清蛋白（BSA）的截留率为80%,展现出较高的渗透性,为制备高性能膜材料提供了新的思路。     

聚间苯二甲酰间苯二胺平板膜的制备及其性能研究

以聚间苯二甲酰间苯二胺（PMIA）为制膜原料,氯化锂（LiCl）、聚乙二醇（PEG-400）和聚乙烯吡咯烷酮（PVP）为添加剂,通过非溶剂诱导相转化法制备了PMIA平板膜,系统考察了聚合物浓度、添加剂种类和含量对PMIA膜结构和性能的影响。结果表明,聚合物浓度和LiCl含量增加,铸膜液黏度增大,导致膜孔径减小,纯水通量降低。而PEG含量的增加,使得聚合物链呈现舒展状态,膜孔径增大,纯水通量升高,亲水性增强。随着PVP含量的增加,膜的纯水通量先升高后降低,膜的亲水性变差。当PMIA的质量分数为9%,LiCl的质量分数为2.8%,PVP的质量分数为1.2%时,膜的纯水通量高达1421.55 L·m^-2·h^-1·bar^-1,对牛血清蛋白（BSA）的截留率为80%,展现出较高的渗透性,为制备高性能膜材料提供了新的思路。     

聚间苯二甲酰间苯二胺树脂的合成研究

以间苯二胺为原料,在溶剂N,N-二甲基乙酰胺中与间苯二甲酰氯反应,聚合成间苯二甲酰间苯二胺树脂。通过在微通道反应器中进行聚合反应时,反应物配比有效控制在1.005~1.000,反应温度0~10℃,溶剂水份300×10~(-6)g/g以下,两种单体进料速率5∶4~5∶3,此条件下,聚合物粘度1.9~2.1,分子量分布稳定。     

Preparation and application of zinc oxide/poly(m-phenylene isophthalamide) hybrid ultrafiltration membranes

A small molecular-weight cut-off (MWCO) of 6000 Da poly(m-phenylene isophthalamide) (PMIA) embedded zinc oxide (ZnO) hybrid ultrafiltration (UF) membrane was synthesized via nonsolvent-induced phase separation (NIPS). Tests of field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), thermal gravimetric analyzer (TGA), Fourier transform infrared (FTIR), capillary flow porometer (CPF), mechanical test, and pure water flux (PWF) for characterization of membranes were carried out. The EDX, FTIR, and TGA indicated the presence of ZnO in the polymer matrix. The hybrid membranes showed enhanced pore density, PWF by the presence of the particles. The contact angle and water flux of modified membrane with 0.03 wt % of nano-ZnO were 47.7° and 52.58 L·m⁻²·h⁻¹ compared to 71.6° and 36.27 L·m⁻²·h⁻¹ respectively; Compared with the hydrophobic membrane, the PMIA membrane, with hydrophilicity, is supposed to exhibit good antifouling properties. Furthermore, the thermal stability and mechanical properties of the modified membranes were increased. Finally, the hybrid membrane was used in treating papermaking white wastewater and exhibited good separation and high water flux. The great properties of the ultrafiltration PMIA membranes indicate their potential for excellent performance in industrial applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47583.     

干法纺丝用聚间苯二甲酰间苯二胺溶液的流变性能

研究了聚间苯二甲酰间苯二胺溶液的固体质量分数、相对分子质量、温度对溶液流变性能的影响。结果表明:聚间苯二甲酰间苯二胺溶液的流变性能受溶液固体质量分数、相对分子质量、温度的影响明显,聚合物相对分子质量增大、溶液固体质量分数增加均使溶液表观黏度增大,温度升高使溶液表观黏度减小,溶液表观黏度随剪切速率的变化幅度较小。试验结果表明:适合干法纺丝的聚间苯二甲酰间苯二胺溶液的固体质量分数为31%³5%,特性黏度为1.6 dL/g左右,纺丝时原液温度范围为5035%,特性黏度为1.6 dL/g左右,纺丝时原液温度范围为50¹20℃。     

着色PMIA纤维结构与性能的研究

采用原液着色的方法,通过湿法纺丝制备了聚间苯二甲酰间苯二胺(PMIA)着色纤维,并对其进行了机械性能、染色深度、热失重、红外光谱分析测试。结果表明:原液着色PMIA纤维的机械性能受颜料加入量的影响很小;颜料含量为3%时就能赋予PMIA原液着色纤维较好的染色深度;原液着色PMIA纤维的起始分解温度较未着色PMIA纤维有所降低,但二者在失重率15%的温度及550℃的重量保持率相似,都具有较好的热稳定性。     

Modification of nylon-6 with semi-or wholly-aromatic polyamides

In this study, flexible Nylon-6 was reinforced by semi-or wholly-aromatic polyamides; poly(m-phenylene isophthalamide) (PmIA), poly(4,4′-diphenylmethane terephthalamide) (PMA), and poly(4,4′-diphenylsulfone terephthalamide) (PSA). 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 > PSA. Moreover, 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 peak at 2θ = 20°, indicating a different crystal structure for multiblock copolyamides. 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 the physical properties of aromatic modified Nylon-6 copolyamides, such as tensile strength, is PmIA > PMA > PSA, but for the elongation PSA > PMA > PmIA.     

对苯二胺改性间位芳香族聚酰胺的合成及热性能研究

采用低温溶液法共缩聚反应合成了5%￣15%的对苯二胺(PPDA)改性间位芳香族聚酰胺(PMIA)共聚物。用1HNMR对改性共聚物进行了分析,讨论了PPDA的含量对共聚物比浓对数黏度的影响;对改性聚合物和PMIA纤维进行了热失重分析,并用红外光谱跟踪法探讨了PMIA和共聚物的热降解过程。实验结果表明,用PPDA改性后的共聚物具有更优异的热性能。     

Some studies on polyblends of poly(p-phenyleneterephthalamide) and nylon-6

Polyblends of poly(p-phenyleneterephthalamide) (PPTA) and nylon-6 have been prepared by coprecipitation from solutions of the polymers in concentrated sulphuric acid. The behaviour of solutions of the polyblends in concentrated sulphuric acid was investigated. The polyblends were characterized by differential scanning calorimetry, X-ray diffraction and density measurements. The polymers were found to form a miscible blend with the composition 62.7 wt% nylon-6 and 37.3 wt% PPTA. The blends could be compacted to hard dense solids by high pressure compaction.     

Synthesis and structural study of poly(isophthalamide)s

The synthesis of a series of soluble 5-alkoxy substituted isophthalamides is described. Condensation of 1,3-diaminobenzene or 2,6-diaminopyridine with alkoxy substituted isophthaloylchlorides yields the title polyaramides. The influence of the alkyl chain length on the supramolecular structure of the polymer is investigated by X-ray diffraction experiments. Initial results indicate a lamellar type solid lattice for the polymers studied here.     

Detection of glass transition in poly(ethylene terephthalate) and nylon-6 by positron annihilation

Positron annihilation lifetime spectroscopy (PALS) was used to investigate the phase transitions, mainly the glass transition, of poly(ethylene terephthalate) (PET) and nylon-6 during the thermal treatment of these polymers. The longest-lived component lifetime and intensity, indicative of ortho-positronium pick-off, exhibit thermal dependencies that can be attributed to the free-volume changes associated with structural transitions. Glass transition temperatures and the volume of intermolecular-space holes among polymer chains were obtained from the lifetime, τ₃ and intensity of formation, I₃, of the long-lived component of ortho-positronium. For PET, the free-volume fraction and thermal expansion coefficients related to the free-volume fraction were also obtained. Double glass transition behavior was noted in the analyzed polymers, which was consistent with their semicrystalline nature as revealed by differential scanning calorimetry. Increases in the slope of the lifetime-temperature plots for nylon-6 and PET were interpreted to suggest that glass transitions are followed by an increased free-volume cavity expansion as temperature is increased. The intensity response for PET was consistent with the association of glass transition with the reduction of crystalline consraint on segmental mobility in the amorphous phase. In contrast, the intensity behavior during the thermal treatment of nylon-6 seems to be governed more by the electronic effects occurring when the polymer chains acquire mobility than by free-volume changes. Since the sensitivity of PALS is in the order of nanometers, it is expected to give an alternative novel technique to estimate phase transitions and relaxations in polymers from the point of view of the free volume. © 1996 John Wiley & Sons, Inc.     

Morphology and organizational characteristics of poly(m-phenylene isophthalamide-b-ethylene oxide) systems

A series of essentially triblock poly(m-phenylene isophthalamide-b-ethylene oxide) with sequence PEO-(MPD-I)-PEO or (MPD-I)-PEO-(MPD-I) and their admixtures with (PEO)_n were studied as solution cast films. Experimental techniques included transmission optical microscopy, transmission electron microscopy, electron diffraction, and X-ray diffraction. Characterization of these systems showed that structure could develop in two ways. The first way was the development of a typical polycrystalline structure of the (MPD-I) segment by the action of such agents as formic acid. In a second manner, however, a non-typical development was manifested by the appearance of crosses In the polarized opticial microscope. These samples showed only an amorphous halo when subjected to wide angle X-ray diffraction measuremfents. Their small angle pattern suggested scattering by dispersed particles. Other experiments indicated the crosses would form only under an unusually restrictive set of conditions, principally that the PEO present must be above a certain molecular weight and concentration and, furthermore, that the solvent must contain a salt such as LiCl. These observations led us to speculate that optical activity of the films showing crosses could occur either by chain orientation near the interface of a spherical particulate second phase or from stress induced bond polarization resulting from the film formation process.     

Hierarchical Cellular Poly(m-phenylene isophthalamide) with High Flame Retardancy,Mechanical Robustness,and Heat Resistance at Extreme Situation

High-performance cellular foams with superior mechanical properties and heat resistance are urgently needed to fulfill the applications in extreme environments. However, they are difficult to be prepared because of low gas diffusion rate in high-performance polymers. In this work, a facile solution-foaming strategy to prepare multifunctional foams based on poly(m-phenylene isophthalamide) (PMIA) is reported. The achieved PMIA foams show a hierarchically cellular structure containing macropores and mesopores. Due to their high porosity, the PMIA foams exhibit low thermal conductivity (0.0447–0.0498 W m⁻¹ K⁻¹) and high sound absorption coefficient at different frequency. A bimodal distribution on acoustic absorption is observed. With a bulk density range of 0.089–0.122 g cm⁻³, PMIA foams possess compressive moduli of 3.2–14.2 MPa and bending strength of 1.1–2.1 MPa, respectively. Moreover, they exhibit a recoverable deformation of 55.4% after 10 cycling 10% strain compressions and maintain a dimensional stability under harsh environment (–196 to 250 °C). Despite generated byproducts like polyurea, they still show a limiting oxygen index (25.2–26.3%) and relatively low heat release rate (178.3 kW m⁻²). This work provides a facile strategy to efficiently prepare high-performance PMIA foams for broad application prospects.     

Crosslinking of rigid poly(vinyl chloride) with epoxysilane

Crosslinking is an effective way to improve the properties of poly(vinyl chloride). A crosslinking agent consisting of R‐glycidoxypropyltrimethoxysilane (KH560) has been used for the first time in order to introduce crosslinking into rigid poly(vinyl chloride). Different thermal stabilizers (organotin, Ca/Zn stearate, and Ba/Zn stearate) as well as sodium bisulfite were tried in order to promote grafting of the epoxy group and enhance the degree of crosslinking. Fourier transform infrared (FTIR) spectra showed that grafting and crosslinking of KH560 with poly(vinyl chloride) could take place, and that a gel content of 40% could be obtained when more than 10 phr of epoxysilane was used with a 2:1 (weight) ratio of BaSt₂/ZnSt₂ and a 1:1 molar ratio of NaHSO₃/KH560, while premature crosslinking was avoided. The Vicat softening temperature of crosslinked PVC could be increased by about 10°C when 5 phr of epoxysilane was added, and thermal degradation could be delayed with increasing gel content. Therefore, epoxysilane‐crosslinked PVC has the potential for extensive applications. J. VINYL ADDIT. TECHNOL., 13:103–109, 2007. © 2007 Society of Plastics Engineers.     

Differential refractometry and light scattering on nylon-6 and poly(methyl acrylate) in mixed solvents

Investigations have been made of solvent systems for potential use in characterizing nylon-6/poly (methyl acrylate) copolymers. To this end, measurements involving differential refractometry (at constant composition and also constant chemical potential of solvents) and light scattering have been conducted on solutions of nylon-6, poly(methyl acrylate) and a mixture of these two polymers. From refractometric and solubility considerations the most suitable solvents are binary mixtures of o-chlorophenol (o-CP) and 2, 2′, 3, 3′-tetrafluoropropanol. In particular, the binary solvent containing 73% (by volume) of o-CP yields the molecular weight of the nylon-6 constituent of the polymer mixture directly, since the light scattering from the other polymer constituent is thereby eliminated. Preferential adsorption of o-CP occurs to both polymers, the maximum extents corresponding to 1 mol $\text{o-}\text{CP}\text{1.4}$ segments nylon and 1 mol $\text{o-}\text{CP}\text{5.7}$ segments poly(methyl acrylate). This is attributed to a breakdown of intramolecular hydrogen-bonding in o-CP and subsequent formation of hydrogen bonds with the carbonyl groups in the polymers.