尼龙1010结构的研究

本工作通过X-光衍射、红外光谱、示差扫描量热、偏光显微镜、粘弹谱及密度观测,考察了尼龙1010样品,分别从玻璃态结晶与从熔融态结晶后的聚集态结构,发现它的结晶结构与尼龙66相似,但从熔融态结晶的晶格有很大畸变,对所涉及的问题进行了讨论,提出了氢键面畸变的模型。     

尼龙66盐固态缩聚反应的研究

采用测定转化率和特性粘数、红外光谱、偏光显微镜、扫描电镜和DSC等方法,研究了结晶尼龙66盐固态缩聚过程的反应历程、初生态尼龙66的结晶形态及其热行为与热历史的关系。实验结果表明,在缩聚过程中尼龙66盐结晶的缺陷可以诱发大分子相的成核,并出现外延结晶过程。发现,初生态尼龙66呈现出原纤状结构状态,且原纤的取向取决于反应条件;讨论了初生态尼龙66在DSC谱上所出现的熔融双峰现象。     

STUDY ON THE MECHANISM OF NYLON 6, 6 DISSOLVING PROCESS USING CaCl_2/MeOH AS THE SOLVENT

A discussion of the mechanism of nylon 6, 6 dissolving process using CaCl_2/MeOH as the sol-vent is presented. The calcium chloride forms a complex compound with nylon 6, 6 by breakingthe hydrogen bonds. The melting point of the CaCl_2 --nylon 6, 6 complex was found to be reducedby 91K relative to the pure nylon 6, 6 polymer. The role of methanol is somewhat similar to acatalyst. The results demonstrate that the complexation of a Lewis acid (CaCl_2) and a Lewis base(nylon 6, 6) can be used to probe intermolecular interactions such as hydrogen bonding in polymers, to modify the polymer properties and mediate its solubility and processing.     

含喹噁啉环的化合物改性聚己内酰胺

合成了14种由三种含喹(哑心)啉环的芳香化合物改性的聚己内酰胺(MC尼龙),并对其形态、抗冲击强度、吸水性及熔融行为等进行了表征。聚苯基单醚喹(哑心)啉(PPQ)单模型化合物对MC尼龙结晶部分几乎没有影响。少量(0.005—5.0％)吩嗪的引入使MC尼龙的颜色、形态及性能等发生巨大变化,改性体系被认为是氢键相互作用,PPQ双模型化合物的改性作用介于二者之间。     

α–γ transition in nylon 6

The α to γ transition that occurs in nylon 6 upon iodine treatment was investigated by infrared spectroscopy, differential thermal analysis, and x-ray diffraction techniques. Thin films of nylon (0.2 mil) were treated in either iodine–potassium iodide aqueous solution or in iodine vapor. Very short treatment times, in the order of 30 sec, were found to effect the transition when a solution 0.5M with respect to iodine was used. The infrared spectra of the iodine nylon complexes formed from either the α- or γ-nylon 6 treated in vapor or dissolved iodine were all similar. This is an indication that molecular iodine is the active species in forming the complex. The temperature of the washing solution used to remove the iodine from the nylon determines whether an α-nylon 6 or γ-nylon 6 is obtained from the complex after washing. Nylon 6 plaque surfaces and thin films are similar in their behavior towards the iodine treatment. The γ-nylon 6 is a stable modification at all temperatures below its melting point. The conversion of the γ form back to the α modification can occur only if the hydrogen bonding is severely affected, e.g., by phenol treatment, iodine treatment, melting, etc. Infrared spectroscopy provided no evidence for an α–γ transition in nylon 6 on heating the sample continuously through its melting point. The shapes of the melting peaks in the above two modifications of nylon 6 were sufficiently different to provide a means of identifying the two crystalline forms.     

Relations between dynamic mechanical properties and melting behavior of nylon 66 and poly(ethylene terephthalate)

Nylon 66 films exhibiting form I melting behavior show the γ mechanical relaxation at ?140°C. Samples which have form II melting behavior do not show this relaxation. The γ relaxation disappears when material having form I behavior is converted to material having form II behavior by annealing or by cold drawing. The form I and form II types of melting behavior are also found in poly(ethylene terephthalate); the interconversions and thermal behavior of the forms are analogous to the nylon 66 case. In poly(ethylene terephthalate), the β relaxation at ?40 to ?60°C is present only when form I melting behavior is found. Conversion to form II melting behavior by annealing or drawing (80°C) again causes the relaxation to disappear. No β relaxation was found in amorphous polymer. The γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) can therefore be associated with the crystalline structure responsible for form I melting behavior. Form I melting behavior has been associated with foldedchain crystals based on previous work. It is therefore postulated that the γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) are associated with motions in the chain folds. This assignment is not inconsistent with the change in the γ dispersion of nylon 66 with the number of backbone CH₂ units, since these will affect the fold structure.     

STRUCTURAL PHASE TRANSITION OF ALIPHATIC NYLONS VIEWED FROM THE WAXD/SAXS AND VIBRATIONAL SPECTRAL MEASUREMENTS AND MOLECULAR DYNAMICS CALCULATION

The crystalline phase transition of aliphatic nylon 10/10 has been investigated on the basis of the simultaneous measurement of wide-angle and small-angle X-ray scatterings, the infrared spectral measurement and the molecular dynamics calculation. An interpretation of infrared spectra taken for a series of nylon samples and the corresponding model compounds was successfully made, allowing us to assign the infrared bands of the planar-zigzag methylene segments reasonably. As a result the methylene segmental parts of molecular chains were found to experience an order-to-disorder transition in the Brill transition region, where the intermolecular hydrogen bonds are kept alive although the bond strength becomes weaker at higher temperature. The small-angle X-ray scattering data revealed a slight change in lamellar stacking mode in the transition region. The crystal structure has been found to change more remarkably in the temperature region immediately below the melting point, where the conformationally disordered chains experienced drastic rotational and translational motions without any constraints by hydrogen bonds, and the lamellar thickness increased largely along the chain axis. These experimental results were reasonably reproduced by the molecular dynamics calculation performed at the various temperatures.     

聚甲醛与热塑性酚醛树脂相容性研究

考察了聚甲醛(POM)与热塑性酚醛树脂(Novolak)的相容性;浊点法研究结果表明,POM/Novolak共混物存在一个低位临界相转变温度.DSC测试表明,POM与Novolak共混后,共混物的熔点下降;通过DSC测试得到数据,采用Hoffman-Weeks平衡熔点外推法和Flory熔点下降方程推算出POM与Novolak的相互作用参数(χ)约为-0.032.FTIR研究表明,Novolak的羟基能够与POM的醚氧基形成氢键,导致共混物中Novolak的羟基峰向高频偏移.研究结果表明,POM与Novolak能够达到热力学相容.     

Partial miscibility in a nylon‐6/nylon‐66 blend coalesced from their common α‐cyclodextrin inclusion complex

We successfully formed a series of inclusion complexes (ICs) between an α‐cyclodextrin (α‐CD) host and two kinds of guest polymers, nylon‐6 and nylon‐66. An attempt to achieve an intimate blend between nylon‐6 and nylon‐66 through the formation and dissociation of their common α‐CD IC was made. The formation of all nylon ICs was verified with wide‐angle X‐ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) and cross‐polarized/magic‐angle‐spinning ¹³C NMR spectroscopy. The experimental results demonstrated that α‐CD could only host single nylon polymer chains in the IC channels, either nylon‐6 or nylon‐66 in their own complexes, and presumably either nylon in neighboring channels of their common IC. The IC‐coalesced blend of nylon‐6 and nylon‐66 was obtained after the removal of the host cyclodextrin from their common IC with dimethyl sulfoxide. The spectroscopic results (FTIR and ¹³C NMR) illustrated that there was a degree of intimate miscibility existing in the IC‐coalesced blend, but not in the solution‐cast physical blend, although X‐ray diffraction patterns showed that the crystal structure of the IC‐coalesced blend was similar to that of the physical blend. DSC thermal profiles suggested that nylon‐66 first formed crystals during coalescence and that the subsequent crystallization of nylon‐6 was greatly affected by the nylon‐66 crystallites because of the close proximity of the two components in portions of the coalesced blend. DSC observations also demonstrated that the melting of the coalesced blend did not lead to complete phase separation of the nylon‐6 and nylon‐66 components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1369–1378, 2004     

Synthesis and properties of some semi-fluoroalkoxy chain liquid crystals

Six compounds with semi-fluorinated chains have been synthesized. When the terminal hydrogen atom in the semi-fluoroalkoxy chain was changed to chlorine, both the clearing point and the melting point were enhanced. It was also found that the clearing points were decreased and melting points increased with the introduction of a triple bond into the cores.     

Influence of structure of 1,1,3-trimethyl-5-carboxy-3-(p-carboxyphenyl)indan upon polyamide properties

Copolyamides of nylon 66 and 1,1,3-trimethyl-5-carboxy-3-(p-carboxyphenyl)indan (PIDA) were prepared by melt polycondensation of nylon 66 salt with PIDA in combination with hexamethylenediamine, trans-1,4-cyclohexanebis(methylamine), and m-xylylenediamine. In addition, hexamethylenediamine-PIDA was incorporated into the copolymer system of nylon 66–poly(hexamethylene terephthalamide). The effect of PIDA upon the intrinsic viscosity, crystallinity, density, melting point, moisture regain, tenacity, initial modulus, and the boiling-water shrinkage of such polyamides was determined. Particular emphasis was placed upon the influence of PIDA on the glass transition temperature of the polyamides. The effect of moisture on the glass transition temperature was also discussed. The physical properties of PIDA copolymers indicate that crystallinity virtually disappears above 20 mole-% PIDA concentration; however, the glass transition temperature measured at 0 and 30% RH increases sharply with increased PIDA concentration.     

Multiple melting and crystallization of nylon‐66/montmorillonite nanocomposites

Nylon‐66 nanocomposites were prepared by melt‐compounding nylon‐66 with organically modified montmorillonite (MMT). The organic MMT layers were exfoliated in a nylon‐66 matrix as confirmed by wide‐angle X‐ray diffraction (WAXD) and transmission electron microscopy. The presence of MMT layers increased the crystallization temperature of nylon‐66 because of the heterogeneous nucleation of MMT. Multiple melting behavior was observed in the nylon‐66/MMT nanocomposites, and the MMT layers induced the formation of form II spherulites of nylon‐66. The crystallite sizes L₁₀₀ and L₀₁₀ of nylon‐66, determined by WAXD, decreased with an increasing MMT content. High‐temperature WAXD was performed to determine the Brill transition in the nylon‐66/MMT nanocomposites. Polarized optical microscopy demonstrated that the dimension of nylon‐66 spherulites decreased because of the effect of the MMT layers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2861–2869, 2003     

Crystalline stoichiometric adducts of polyamides with phosphoric acid

It is shown the crystalline stoichiometric adducts of phosphoric acid with polyamides such as nylon 6 and poly-p-benzamide, and probably nylon 66, nylon 69, nylon 11, and nylon 12, can be prepared. These adducts are characterized by their unique wide-angle x-ray diffraction patterns and by rather low melting or decomposition temperatures. The thermal behavior and infrared data, indicate that interactions between the acid and the polymeric amide residues are weak.     

Structure–property relationships of ring-containing nylon 66 copolyamides

Several series of nylon 66 copolyamides were prepared with up to 30 mole-% substitution of ringed comonomers of the type X-(CH₂)_n-R-(CH₂)_n-X, where n = 0, 1, or 2; X = ?NH₂ or ? CO₂H; and R = phenylene, cyclohexylene, or naphthyle. The ring structure was correlated with glass transition temperature and melting point. The important features of ring structure fall into the following categories: ring isomerism, aromaticity, diamine vs. diacid substitution, chain length, and ring substitution. Proper “fit” (isomorphism) of the comonomer into the nylon 66 chain appears to be the main criterion for ringed copolymers of high T_g and high melting point.     

Melting behavior and morphology of drawn nylon 6

Thermal analysis has been carried out on drawn nylon 6 filaments annealed at various temperatures between 150 and 210°C and then methoxymethylated to various degrees. It is shown that the melting point inherent to the morphology of drawn nylon 6 can be obtained from samples in which the reorganization of defect crystallites in the course of thermal analysis is prevented by a proper degree of methoxymethylation of amorphous regions. The melting point thus obtained is in linear relation with the reciprocal crystallite size in the direction of fiber axis which has been obtained from small-angle x-ray data and crystallinity. The extrapolation and the slope of this linear relation give the equilibrium melting point of nylon 6 as 245°C and an end-surface free energy of 42 erg/cm². The results seem to provide strong support for the presence of chain-fold surfaces in the drawn and annealed polymers.     

Solution crystallization of nylon 12

Electron microscopy and x-ray diffraction data have been obtained on nylon 12 crystallized from 1-hexanol, 1,6-hexanediol, and hexylene glycol. Ribbonlike lamellar crystals of the γ form are obtained by crystallization from all the solutions and elongated flat crystals of the α form by crystallization from the 1-hexanol and hexylene glycol solutions. The direction of the hydrogen bond in these crystals is almost parallel to that of maximum crystal elongation. α- and γ-form crystals both grow from 1-hexanol and hexylene glycol at appropriate crystallization temperatures. γ-form crystals alone are obtained from 1,6-hexanediol solution at every crystallization temperature. The long periods measured by small-angle x-ray diffraction for the solution-grown crystals are in the range 7.6–10.6 nm. The melting behavior of the solution-grown crystals is examined and discussed. The melting temperatures of the γ form may be lower than that of the α form. An equilibrium melting temperature of 208.4°C for γ-form crystals is obtained by using a relation between thickness of lamellar crystals and their melting temperatures observed by differential scanning calorimeter measurements. Solvents affect the growth of the two crystalline forms in solution crystallization.     

Microstructural rearrangement during heat treatment of drawn nylon 66 fiber

Melt-spun nylon 66 fibers were drawn and subsequently heat treated isothermally and quenched. The heat-treated fibers were then examined by wide-and small-angle x-ray scattering (WAXS and SAXS), by differential scanning calorimetry (DSC), and by static mechanical testing. These measurements allow one to follow microstructural changes taking place during the course of the heat treatment. WAXS results show that as the treatment progresses, the crystallites become both more perfect and more disoriented with respect to the fiber axis. SAXS results show crystallite thickening. DSC results show that the melting point increases, goes through a maximum, and then decreases as the heat treatment progresses. The tensile modulus decreases with time to an asymptotic level. The changes in crystallite perfection and thickness occur more rapidly than do the changes in crystallite orientation, modulus, and melting point. A model is proposed whereby the two time frames are related to intracrystalline and intercrystalline processes, respectively.     

Multiple melting in nylon 66

Either of the two endothermic melting peaks found by differential thermal analysis of nylon 66 may be converted to the other by appropriate choice of annealing conditions. The two peaks are considered due to the melting of two morphological species, forms I and II. Form I is relatively fixed in melting temperature, while the form II melting temperature varies with annealing conditions and can be either above or below form I. The two forms can be distinguished by whether or not the conversion I → II takes place; if the sample is in form II no change in the thermogram is observed under suitable conversion conditions. The conversion of form I to form II also takes place during cold drawing. It has been previously shown that form I results from rapid cooling from the melt, and form II results from slow cooling. Form I appears to be kinetically favored, while form II is thermodynamically preferred. The variability in the form II melting point is attributed to variable crystal size and/or perfection.     

Hydrogen bonding in polyamide 66/clay nanocomposite

Hydrogen bonding in polyamide 66/clay nanocomposite (PA66CN) was first investigated with temperature Fourier transform infrared (FTIR), the results of which were compared with that of pristine polyamide 66 (PA66) with the same thermal history. FTIR spectra at room temperature revealed that there is essentially 100% hydrogen bonding in both PA66CN and PA66, and the difference in hydrogen‐bonding status between them is tiny. Additionally, DSC showed that the crystalline degrees and melting temperatures of PA66CN and PA66 prepared by melt quenching are similar. However, the changes of hydrogen bonding with temperature in PA66CN and PA66 are different. As the temperature rose, the hydrogen bonding in PA66CN attenuated and dissociated considerably at a smaller rate than PA66. According to transmission electron microscopic morphology of PA66CN, we analyzed the effect of nanodispersion clay layers on the motion of a polymer chain and the thermal expansion of crystalline lamella for interpreting the observed phenomenon. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2313–2321, 2003     

Effect of fluorine substituents on the properties of nylon copolymers

Nylon 610/65F and nylon 610/65 copolymers were prepared by melt polycondensation from the diethylester of sebacic acid (10) and hexafluoroglutaric acid (5F) or glutaric acid (5) with hexamethylene diamine (6). Reduced specific viscosities of nylon 610/65F were lower than those of nylon 610/65. The crystallinity measured by WAXS and the melting point measured by DTA were depressed by the copolymerization. The melting point depression of nylon 610/65F was much larger than that of nylon 610/65. The thermal decomposition temperature measured by TG was also depressed significantly for nylon 610/65F. The residue at 600°C was increased by the fluorine substitution. The copolymers with higher fluorine content became flame retardant. The solubility was appreciably affected by the fluorine substitution. The contact angle for nylon 610/65F varied in a complicated manner with increasing 65F content and tended to be higher than the corresponding nylon 610/65.