Depolymerization of nylon 6 waste fibers

The depolymerization of nylon 6 was carried out with various solvents, such as formic acid, hydrochloric acid, and sulfuric acid, followed by heating under reflux for different times. From the polymer dissolved and refluxed in formic acid, degradation products with different ranges of molecular weights were collected by fractional precipitation, with small lots of distilled water added as a nonsolvent. The characterization of different fractions was carried out by the measurement of the viscosity‐average molecular weight, the number‐average molecular weight, and the number of amino end groups. The presence of the monomer, aminocaproic acid, was confirmed by thin‐layer chromatography in the case of hydrochloric acid treated nylon 6. With a strongly acidic ion‐exchange resin, the monomer was separated in its purest form, and the melting point was noted. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 186–190, 2006     

Some kinetic aspects of continuous screening

Continuous screening of ferrous sinter mixtures was studied in a laboratory screen (310 × 600) incorporating continuous weighing of the underflow and overlfow streams with the aim of checking the applicability of recent batch sieving results [1] to continuous screening.The results of the study show that the two operations are comparable in all respects if deck length in continuous screening and time in batch sieving are interchanged.The effect of oversize particles is again found to be beneficial in speeding up the screening of near-mesh material.Calculated screening rate constants with and without the presence of oversize, unfortunately, also parallel the results of batch sieving and this problem of theory is, therefore, still unresolved.     

Some kinetic aspects of heterophase saponification of polyacrylonitrile fibres

The kinetics of heterophase saponification of PAN fibre based on poly(AN-co-MA-co-ItA) was investigated at different temperatures and it was shown that the apparent activation energy of this process decreases with an increase in the concentration of caustic soda. The thermal characteristics of chemisorbents based on PAN fibre in the H form, which has a different static exchange capacity, were assessed and it was found that the temperature of the maximum rate of thermal polycyclization and its exothermic effect decrease as the concentration of carboxyl groups in the polymer substrate increases. A variant of the scheme of polymer-analog transformations of poly(AN-co-MA-co-ItA) during heterophase saponification of PAN fibres is proposed. Translated fromKhimicheskie Volokna, No. 3, pp. 61–65, May–June, 2000.     

Some observations on the breakdown of nylon 6. Kurzmitteilung

Different extents of physical and molecular breakdown have been noted, when films of nylon 6 are stirred in warm water after relatively short contact with dilute aqueous cupric chloride. The observations are discussed qualitatively.     

原位复合阻燃尼龙6的非等温动力学研究

采用差示扫描量热法研究了原位聚合反应制备阻燃尼龙6的非等温结晶行为,用Jeziorny法和莫志深法对其动力学过程进行了分析。结果表明:由于阻燃剂起到异相成核作用,使晶核的生长变快,提高了阻燃尼龙6的结晶温度和成核速率。随降温速率的增加,其结晶峰从高温向低温方向移动,峰形变宽,结晶时间缩短。同时阻燃剂在尼龙6分子链中存在相互作用力,阻碍了尼龙6分子链在结晶过程中的运动,导致结晶活化能提高,晶体生长速度下降,结晶度降低。     

Some physical properties of acrylamide and acrylonitrile grafted nylon 6

Graft copolymerization of acrylamide and acrylonitrile on nylon 6 swollen in formic acid (60%) for 30 min was performed using ceric ions as initiator at 60°C. The optimum conditions to get highest percentage of graft-on were utilised to prepare the grafted samples with various amounts of polymer deposited inside the fibres. The mechanical properties, moisture regain, density, infrared studies, birefringence, dye uptake and dynamic mechanical properties were determined for the grafted samples and the results are discussed in relation to possible structural changes due to graft copolymerisation.     

Some physicochemical properties of methyl methacrylate-grafted nylon 6. II.

Graft copolymerization of methyl methacrylate on nylon 6 was investigated using KMnO₄ as initiator at 60°C. The optimum conditions of the grafting process using various amounts of methyl methacrylate have been utilized. Physical and chemical properties of the grafted nylon such as moisture regain, density, and infrared spectra are studied. Furthermore, the dyeing behavior of the grafted nylon toward acid and direct dyes is also investigated. The rate of graft copolymerization (R_p) of methyl methacrylate with this system was evaluated and expressed by the following equation depending upon the potassium permanganate concentration used: The degree of polymerization of isolated poly(methyl methacrylate) from the grafted nylon was found to be a first-order dependence.     

Some kinetic aspects of the oxidation of graphite and platinum graphimet

The catalytic effect of platinum on the oxidation of graphite has been examined for 1 wt% Pt-graphimet with the use of temperature programmed desorption technique. Analyses of results show that the addition of platinum particles enhances the overall rate of carbon oxides evolution by increasing the active surface area, with little or no change in the apparent activation energy of desorption. This is attributed to the scission of carbon-carbon bonds by platinum. Results of the mathematical modelling based on controlled atmosphere electron microscopy studies by Baker and his co-workers seem to suggest the existence of a viscous oxide layer and surface diffusion on the metal surface and a possibility that both electron and oxygen transfer mechanisms are operating in the carbon-oxygen reactions catalysed by platinum group metals.     

Vibration welding of nylon 6 to nylon 66

Vibration welding of dissimilar nylons is a promising technique for assembling complex components made of different polymers. The effects of pressure and meltdown on the tensile strength of nylon 6 (PA 6) to nylon 66 (PA 66) vibration welds were determined in this study using an experimental design and three weld geometries. Weld strengths were generally improved by increasing meltdown and decreasing weld pressure. The weld strength was also shown to vary with the position of the lower melting material for T‐welds. Using differential scanning calorimentry and fracture surface analyses, it is concluded that for all geometries, higher weld strengths can be achieved when both materials are melted. Polym. Eng. Sci. 44:760–771, 2004. © 2004 Society of Plastics Engineers.     

Interpretive nonlinear viscoelasticity: Dynamic properties of nylon 6, nylon 66, and nylon 12 fibers

Nonlinear response of nylon 6, nylon 66, and nylon 12 fibers to sinusoidal straining under relatively large strain amplitude is analyzed in terms of the changes in properties during the straining, i.e., the change in modulus, change in internal friction and change in structure which involves energy release or absorption in straining. Modulus generally increases with strain but it decreases with increase of strain amplitude, the effect of strain amplitude being largest with nylon 6 and smallest with nylon 66. Mechanical loss increase with the increase of strain amplitudes in nonlinear manner, and the magnitude of change is largest with nylon 66 and smallest with nylon 6. During the extension phase, structural change occurring in nylon 6 is predominantly an increase in order or orientation while that with nylon 66 is crack opening or cavitation. Various aspects of the experiments and analysis of the data are described in detail.     

Polymorphic behavior of nylon 6/saponite and nylon 6/montmorillonite nanocomposites

X‐ray diffraction methods and DSC thermal analysis have been used to investigate the structural change of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of ε‐caprolactam and then exfoliaton of the layered saponite or montmorillonite by subsequent polymerization. Both X‐ray diffraction data and DSC results indicate the presence of polymorphism in nylon 6 and in nylon 6/clay nanocomposites. This polymorphic behavior is dependent on the cooling rate of nylon 6/clay nanocomposites from melt and the content of saponite or montmorillonite in nylon 6/clay nanocomposites. The quenching from the melt induces the crystallization into the γ crystalline form. The addition of clay increases the crystallization rate of the α crystalline form at lower saponite content and promotes the heterophase nucleation of γ crystalline form at higher saponite or montmorillonite content. The effect of thermal treatment on the crystalline structure of nylon 6/clay nanocomposites in the range between Tg and Tm is also discussed.     

Some kinetic aspects of radical copolymerization: influence of the reaction medium on the reactivity ratios

The reactivity ratios for the free radical copolymerization of styrene and methyl methacrylate at 50°C have been evaluated in dioxane, acetone and dimethylformamide solutions. In all these systems there is a marked solvent effect on both r₁ and r₂, which can be correlated to the variation in the dielectric constant of the solvent. The role of solvents in enhancing the polarization of growing chains and the alternation tendency is discussed.     

锦纶66与锦纶6帘线的性能对比

对锦纶66与锦纶6帘线的性能进行对比。与锦纶6帘线相比，锦纶66帘线具有良好的基本耐热性能、尺寸稳定性及耐高温性能，在受热状态下的断裂强力保持率较高；用其生产轮胎时可提高硫化温度，缩短硫化时间，提高生产效率，而轮胎使用寿命长，安全性和耐久性较优。     

Intrinsic birefringence of nylon 6

Different values are reported in the literature for the intrinsic birefringence of the crystalline (Δn) and the amorphous (Δn) phases in nylon 6. Mostly, these values have either been determined by extrapolation (and then it is assumed that Δn = Δn) or calculated theoretically. In this study, intrinsic birefringence values Δn and Δn for nylon 6 were determined using the Samuels two-phase model which correlates sonic modulus with structural parameters. Three series of fiber samples were used: (1) isotropic samples of different degrees of crystallinity for estimation of E and E moduli at two temperatures. The following modulus values were obtained: 1.62 × 10⁹ and 6.66 × 10⁹ N/m² for 28.5°C, and 1.81 × 10⁹ and 6.71 × 10⁹ N/m² for ?20°C; (2) anisotropic, amorphous fiber samples for estimation of Δn = 0.076 and E = 1.63 × 10⁹ N/m² at 28.5°C; (3) semicrystalline samples of various draw ratios for estimations of Δn = 0.089 and Δn = 0.078. All measurements were carried out with carefully dried samples to avoid erroneous results caused by moisture.     

Interaction of nylon 6-clay surface and mechanical properties of nylon 6-clay hybrid

We synthesized nylon 6-clay hybrid materials using four types of clay minerals, montmorillonite, saponite, hectrite, and synthetic mica. The mechanical properties of their injection molded specimens were measured according to ASTM. Nylon 6-clay hybrid using montmorillonite was superior to the other hybrids in mechanical properties. This might result from the difference in the interaction between nylon molecules and silicates in the hybrids. To clarify this hypothesis, we synthesized intercalated compounds of the clay minerals with glycine as the model of the hybrids, and analyzed the interaction using ¹⁵N cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. The ¹⁵N-NMR result reveals that the positive charge density on the nitrogen of the intercalated compound based on montmorillonite was largest in all the intercalated compounds. It was suggested that montmorillonite interacted strongly with nylon 6 by ionic interaction. This ionic interaction was one of the reasons why these hybrid materials had superior mechanical properties. © 1995 John Wiley & Sons, Inc.     

橡胶改性尼龙6动力学

采用酰基己内酰胺封端的丁腈橡胶(CHTBN)或丁苯橡胶(CHTBS)与NaOH作为引发催化体系,反应温度在145～160℃之间,通过绝热法测定反应过程的温升曲线,计算得到了动力学参数。采用CHTBN/NaOH时反应级数为一级,活化能在72.91～73.16 kJ·mol-1之间,指前因子在3.22×10¹¹～3.38×10¹¹mol ^1-n·s^-1范围内;采用CHTBS/NaOH时反应级数在1.23～1.34之间,偏离了1级反应,活化能在85.55～86.88 kJ·mol-1之间,指前因子在4.52×10¹¹～5.09×10¹¹mol ^1-n·s^-1范围内。在前人工作的基础上建立了阴离子聚合绝热反应动力学模型并对反应过程进行了模拟,结果与实验温升曲线具有很好相关性,从而证明了模型的合理。     

Comparison of nanocomposites based on nylon 6 and nylon 66

Nylon 6 and nylon 6,6 organoclay nanocomposites were prepared by melt processing using a twin screw extruder. The effects of polyamide type and processing temperature on the mechanical properties and the morphology of the nanocomposites were examined. Mechanical properties, transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), percentage crystallinity and isothermal thermo-gravimetric analysis (TGA) data are reported. A particle analysis was performed to quantitatively characterize the morphology; these results are later employed in modeling the modulus of these materials using composite theory. No significant difference was observed in the mechanical properties and morphology of PA-6 nanocomposites processed at two different temperatures. PA-6 nanocomposites had superior mechanical properties than those made from PA-66. The tensile strength of PA-66 nanocomposites deviated from linearity at high levels of MMT. WAXD and TEM results show that the PA-6 nanocomposites are better exfoliated than the PA-66 nanocomposites, which exhibit a mixture of intercalated and exfoliated structures. Mechanical properties were consistent with the morphology. DSC reveals a higher percentage of crystallinity in the PA-66 samples. Isothermal TGA shows only a 5% difference in the degradation of the organic modifier on the organoclay processed at 240 °C versus 270 °C. Particle analysis shows a higher average particle length and thickness, and a lower average particle density and aspect ratio in nanocomposites based on PA-66 versus PA-6. The Halpin-Tsai and Mori-Tanaka composite theories predict satisfactorily the behavior of the PA-6 nanocomposites, while the PA-66 nanocomposites were predicted acceptably up to a certain volume fraction where the non-linear behavior takes effect. All the results indicate that there is a lower degree of exfoliation in the nanocomposites produced with a PA-66 matrix apparently stemming from the chemical differences between PA-6 and PA-66.     

Biodegradation of nylon4 and its blend with nylon6

The nylon4 portion in the blend films composed of nylon4 and nylon6 was degraded and completely disappeared within 4 months in two kinds of composted soils gathered from different university farms as well as pure nylon4 film reported previously, while the nylon6 portion remained even after the burial test for 15 months. Nylon4 powder was also degraded to carbon dioxide in the degradation test in an activated sludge obtained from a sewage disposal institution in Kogakuin University. Three species of microoganisms (i.e., ascomytous fungi) were isolated through the inoculation from the nylon4 film partially degraded in the soil on a medium containing nylon4 powder as a carbon source. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2307–2311, 2002