Structure and properties of N-octadecylated poly(p-phenylene terephthalamide)

N-octadecylated PPTA's with various molecular weights were synthesized from PPTA and n-octadecyl bromide via the metalation reaction. The polymer exhibited side-chain crystallization at 314 K due to the long alkyl side chains and both crystallinity and the perfection of the crystal increase with increasing in the molecular weight. The results of IR spectra and the wide angle X-ray indicate that the polymer crystallizes in hexagonal form. The mechanical and the dynamic mechanical properties of N-octadecylated PPTA's were measured. Two tan δ peaks were observed in a temperature range of 310–350 K and at 260 K, respectively, which can be designated α_c and α_a relaxation, respectively. The concentrated solutions of N-octadecylated PPTA's in tetrahydrofuran, dichloroethane, tetrachloroethane, and bromoform showed liquid crystalline behavior of lyotropic type.     

含氯聚对苯二甲酰对苯二胺纤维的结构与性能

以邻氯对苯二胺(Cl-PPD)与对苯二甲酰氯(TPC)为单体,在N-甲基吡咯烷酮(NMP)/氯化钙(Ca Cl2)或氯化锂(Li Cl)体系中进行低温溶液聚合,合成了含氯聚对苯二甲酰对苯二胺(Cl-PPTA)溶液,直接进行湿法纺丝,制备了Cl-PPTA纤维。采用旋转流变仪测试了Cl-PPTA溶液的流变性能,利用傅里叶变换红外光谱、扫描电子显微镜、热失重分析、纤维强伸度仪、声速取向测量仪、氧指数测定仪对Cl-PPTA纤维的结构及性能进行了表征。结果表明:相比于NMP/Ca Cl2体系,NMP/Li Cl体系的Cl-PPTA溶液黏度更低,所制得的纤维其表面更光滑、结构更致密,纤维力学性能也较好;热处理后两种纤维力学性能均得到进一步改善;两种Cl-PPTA纤维具有较好的热稳定性,其阻燃性能均远高于PPTA纤维。     

Preparation of poly(p-phenylene terephthalamide)/poly(vinyl chloride) molecular composite and its thermal and mechanical properties

Poly(p-phenylene terephthalamide) (PPTA) was blended with poly(vinyl chloride) (PVC) by solution-blending method. PPTA was metalated for dissolving in dimethyl sulfoxide. Dimethyl sulfoxide was used as a common solvent. In PPTA/PVC composite, PPTA accelerated the thermal degradation of PVC. PPTA molecules are aggregated as microfibrillar form in PVC matrix. Such microfibrils are dispersed homogeneously in PVC matrix, according to polarizing microscopic observation. The average diameter of the microfibrils becomes smaller in the composite with lower content of PPTA. In the surface region of PPTA microfibrils the intermolecular hydrogen bonds between C? Cl of PVC and N? H of PPTA are formed. Young's modulus and the yield stress at room temperature were higher in the composites than those in PVC. The modulus of the composites was higher, especially at the high temperatures above their glass transition temperatures, than that in PVC. The temperature dependence of modulus can be calculated by using the mechanical model equivalent to the quasi-3-dimensional microfibrillar model which will be approximately applied to the composite structure. It becomes apparent that the modulus of the PPTA microfibrils evaluated by using the mechanical model is higher in the higher molecular weight PPTA.     

正己烷溶剂对聚对苯二甲酰对苯二胺聚合反应的影响

以对苯二胺和对苯二甲酰氯为反应单体,以氯化钙的N-甲基吡咯烷酮(NMP)溶液为溶剂,同时加入不与NMP互溶的正己烷,采用低温溶液缩聚反应制得聚对苯二甲酰对苯二胺(PPTA),研究了正己烷的加入对PPTA的聚合反应及产物结构与性能的影响。结果表明:正己烷的引入可以推迟PPTA聚合反应过程中产生凝胶的时间,有利于聚合反应的进行;当正己烷与NMP的体积比为1∶2时,可以制得较高相对分子质量的PPTA;正己烷的加入可使PPTA树脂颗粒的比表面积更大,但对其结构和性能影响不大。     

Improved properties of molecular composite of nitrile rubber and poly (p-phenylene terephthalamide) by blending with poly (vinyl chloride)

Summary Nitrile rubber (NBR) was reinforced by poly(p-phenylene terephthalamide) (PPTA) with a coprecipitation method from a common solvent of them. PPTA was converted to N-sodium PPTA with sodium hydride in DMSO, forming homogeneous solution. DMF dissolves NBR. Both solutions were blended to form an isotropic solution. The precipitant was NBR reinforced by PPTA which was regenerated from N-sodium PPTA at coagulation as reported previously. The molecular composite thus obtained was mill-blended with poly(vinyl chloride) (PVC) in order to enhance solvent resistant property. The vulcanized composite of NBR/PVC reinforced by PPTA showed higher modulus, higher strength and more improved solvent resistance than the gum stock and the black stock of NBR/PVC. The properties of the molecular composite containing 5phr PPTA found approximately comparable to those of the black stock of NBR/PVC with 30–40phr ISAF carbon black.On Leave from Japan synthetic Rubber Co., Ltd., Higashi-yurigaoka, Assao-ku, Kawasaki 215, Japan     

Deformation band studies of axially compressed poly(p-phenylene terephthalamide) fiber

Deformation mechanism of poly(p-phenylene terephthalamide) (PPTA) fiber during axial compression was studied. PPTA fibers were embedded in resin and axialy compressed in a tensile machine. PPTA fibers were then taken out from resin at various stages of compression. Kink band formation was examined by means of polarizing microscopy, X-ray diffraction (WAXD), electron diffraction (ED), and electron microscopy. WAXD pattern of seriously compressed PPTA fiber shows that (200) reflection spots and arcs appear on the equator and meridian respectively. On the other hand, (110) reflection spots are confined to the equator. PPTA fiber could be splitted tangentially and radially into two kinds of thin fibrillar fragments (I and II) which reveal two distinct types of kink band and ED pattern. In fragment I obtained by tangential splitting, kink bands are formed at about 55° with respect to fibril axis, whereas in fragment II obtained by radial splitting kink bands are formed perpendicular to the fibril axis. These results were confirmed by ED studies. It was assumed that slip of (200) planes containing hydrogen bonded sheets as well as intermicrofibril slip plays an important role in the deformation of PPTA fiber during axial compression.     

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.     

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.     

Synthesis and properties of poly(imide siloxane) block copolymers with different block lengths

Several poly(imide siloxane) block copolymers with the same bis(γ‐aminopropyl)polydimethylsiloxane (APPS) content were prepared. The polyimide hard block was composed of 4,4′‐oxydianiline and 3,3′,4,4′‐diphenylthioether dianhydride (TDPA), and the polysiloxane soft block was composed of APPS and TDPA. The length of polysiloxane soft block increased simultaneously with increasing the length of polyimide hard block. For better understanding the structure–property relations, the corresponding randomly segmented poly(imide siloxane) copolymer was also prepared. These copolymers were characterized by FT‐IR, ¹H‐NMR, dynamic mechanical thermal analysis, thermogravimetric analysis, polarized optical microscope, rheology and tensile test. Two glass transition temperatures (T_g) were found in the randomly segmented copolymer, while three T_gs were found in the block copolymers. In addition, the T_gs, storage modulus, tensile modulus, solubility, elastic recovery, surface morphology and complex viscosity of the copolymers varied regularly with increasing the lengths of both blocks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Uniplanar orientation of poly(p-phenylene terephthalamide) crystal in thin film and its effect on mechanical properties

The uniplanar orientation of poly(p-phenylene terephthalamide) (PPTA) crystal was investigated by x-ray and infrared measurements. Thin PPTA films 3–15 μm thick were prepared by coagulating a sulfuric acid solution of PPTA with various coagulants. Two types of uniplanar orientation were observed, depending on the coagulant used. Thin film coagulated with water exhibits (0k0) uniplanar orientation and film coagulated with other coagulants such as methanol, ethanol, and acetone exhibits (h00) uniplanar orientation. These (h00) and (0k0) uniplanar orientations are formed with crystal modifications I and II, respectively. The (0k0) uniplanar orientation transforms to (h00) upon annealing, accompanying crystal transformation from modification II to modifications I. These uniplanar orientations may result from anisotropic crystal growth due to polymer–coagulant interaction along the hydrogen bond direction. The effect of these uniplanar orientations on the mechanical properties was also examined. The thin film having the (0k0) uniplanar orientation shows ductile fracture, whereas the one having the (h00) uniplanar orientation shows brittle fracture upon tensile deformation. These results are explained on the basis of the direction of the uniplanar orientation of the hydrogen-bonded sheet.     

聚对苯二甲酰对苯二胺的合成方法

分别介绍了聚对苯二甲酰对苯二胺的应用及界面缩聚法、酯交换法、气相聚合法、低温溶液缩聚法、直接缩聚法等几种合成方法的优缺点,分析了国内外聚对苯二甲酰对苯二胺的发展趋势。     

Tensile deformation of poly(p-phenylene terephthalamide) fibres,an experimental and theoretical analysis

The tensile deformation of poly(p-phenylene terephthalamide) fibres has been investigated. Functional relationships observed between stress, crystallite orientation distribution, dynamic modulus and strain are derived from an analysis of the deformational behaviour of a series model consisting of a linear arrangement of crystallites. It is shown that the deformation of these fibres is largely brought about by the elastic strain and irreversible rotation of the crystallites. A formula is derived for the stress—strain relationship of a crystalline polymeric fibre with a narrow crystallite orientation distribution.     

Degradation of respirable fibrils of poly(p-phenylene terephthalamide) by solar ultraviolet radiation

After ～ 160 days in the environment, the polymer in a respirable-size poly(p-phenylene terephthalamide) fibril (diameter = 0.3 μm) is expected to degrade, due to solar ultraviolet radiation, from an initial molecular weight of ～ 20,000 to less than 400. This estimate is based on ultraviolet absorption characteristics, photolytic degradation kinetics, and judgments regarding how these translate into actual time in the environment. Degradation to this molecular weight level will cause the fibril tensile strength and modulus to decrease to ～ 1% of their initial values. Mechanically, such a degraded fibril will be weak and brittle with properties similar to those of uncooked spaghetti. © 1994 John Wiley & Sons, Inc.     

Synthesis of block copolymers of poly(p-dioxanone) block poly(tetrahydrofuran)

Summary The triblock copolymers of poly(p-dioxanone)-b-poly(tetrahydrofuran)-b-poly(p-dioxanone) were synthesized by ring-opening polymerization of p-dioxanone in the presence of dihydroxyl poly(tetrahydrofuran)(PTHF) using stannous octoate (SnOct₂) as a catalyst. The effects of feed ratio, reaction time and reaction temperature on the copolymerization were investigated. It was found that the optimal reaction temperature and time were 80 °C and 42 hours, respectively, and the molar ratio of p-dioxanone/SnOct₂ (PDO/cat.) had little influence on the inherent viscosity of the copolymers. The triblock copolymers were characterized by various analytical techniques such as ¹H-NMR and DSC.     

Preparation of poly(dimethylsiloxane)–polypeptide block copolymers

Block copolymers composed of poly(dimethylsiloxane) segments linked to polypeptide have been synthesized by reacting primary amine-terminated silicone with N-carboxy anhydrides of amino acids. The amine-terminated silicone was prepared by reacting “living” polysilanolate with γ-aminopropyltriethoxysilane. The block copolymers prepared consisted of segments of poly(DL-phenylalanine) or poly(γ-benzyl-L -glutamate). The block copolymers were purified by extraction with solvents which are selective for the homopolymers. Analysis of the products was accomplished by hydrolysis of the polypeptide segments, infrared spectra, gel permeation chromatography, and elemental analysis. The content of the copolymers ranged from 50 to 87% polypeptide.     

Preparation and properties of some graft copolymers of the poly(2-chlorocyanurate) ester of bisphenol A

Graft copolymers of poly(2-chlorocyanurate)ester of bisphenol A have been prepared by coupling with polymers containing nucleophilic terminal groups. Polystyrene, poly(ethyl acrylate) and poly(methyl methacrylate) have been prepared. Physical properties of the grafts are characterized by two separate glass transition temperatures characteristic of the two homopolymers involved. The thermostability of the grafts increased with increase in weight fraction of polycyanurate in the copolymers.     

Preparation and physical properties of polyurethane modified with poly(4,4′-diphenylsulfone terephthalamide)

Three conventional polyurethane (PU) elastomers were blended physically with various ratios of high molecular weight of poly(4,4′-diphenylsulfone terephthalamide) (PSA) to form 12 PU/PSA polyblends in order to modify their physical properties. Also three new polyurethanes were synthesized with a low-molecular-weight PSA prepolymer as a hydrogen donor for chain extending. From dynamic properties, it showed that both the blends and the new polyurethanes (or polyurethane-ureas) exhibited a glass transition temperature (T_g) below 0°C and had a higher modulus E′ than those of the conventional PU. Based on the analysis of X-ray diffraction of the conventional and the new PU, it was shown that the degree of stress-induced crystallization was dependent on the segmental composition of the soft and hard segments and also the degree of its stretching. On the morphological observation, it was revealed that both the blends and the new polyurethanes were in a dispersed phase structure, although new PU exhibited a better compatible state. For tensile properties, it was found that both tensile strength and elongation of the new polyurethanes were better than those of the blends and conventional PU. © 1994 John Wiley & Sons, Inc.     

Mechanical properties of poly(vinyl chloride) blends and corresponding graft copolymers

The mechanical properties of the poly (vinyl chloride) (PVC) and poly (glycidyl methacrylate) [poly (GMA)] blend system and the PVC and poly (hydroxyethyl methacrylate) [poly (HEMA)] blend system and their crosslinked films were investigated. At the same time, the mechanical properties for the corresponding graft copolymers such as PVC-g-GMA, PVC-g-HEMA, and their crosslinked films were also investigated in this study. The results showed that the tensile strengths for PVC–poly (GMA) blend systems were higher than those for PVC-g-GMA graft copolymer, and the tensile strengths for PVC-g-HEMA were higher than those for PVC-poly (HEMA) blend systems. However, the mechanical properties for the PVC–poly (GMA) blend system were not affected by the crosslinking of the blend system, but those for PVC-poly (HEMA) and their graft copolymers decreased with an increase of the equivalent ratio ([NCO]/[OH]) of the crosslinker. Finally, the surface hydrophilicity of the PVC-g-HEMA graft copolymer and PVC-poly (HEMA) blends were also assessed through measuring the contact angle. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 307–319, 1998