Mixtures Of Nylon Research Articles

Mechanical properties and crystallization behavior of three kinds of straws/nylon 6 composites

After alkali treatment, wheat straw, maize straw and rice straw were mixed with a mixture of nylon 6 (PA6) and prepared into composites using the melt blending method. The mechanical properties and crystallization behavior of three kinds of straw fiber/PA6 composites were studied using tensile and impact tests, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results showed that increasing of the three kinds of straw fibers initially increased the tensile strength of the composites and then decreased, and that the tensile strength reached a maximum value when the wheat straw fiber content was 10%, which was 56.9% higher than that of the pure PA6. The impact strength of the composites initially decreased and then increased, with the maximum impact obtained for the composites with the wheat straw fiber content of 10%, which was 39.2% higher than that of the pure PA6. The introduction of the three kinds of straw fiber also induced the formation of α crystal formed in the PA6. With the increase of the straw fiber content, the grain size of the composite increased continuously, the crystallization temperature (Tc) decreased, the melting temperature (Tm) and crystalline changed slightly, and the maximum degree of crystallinity was obtained when the wheat straw fiber content was 10%.

An Experimental Study on Fluidization of Binary Mixture in Particulate Flows

In this article, we studied experimentally the fluidization of binary mixture in particulate flows. A laboratory fluidized bed is built with water being used as carrying fluid. Three types of solid particles, nylon, glass, and aluminum of the same size and different densities, were used in the experiments. We investigated the wall effect to the fluidization of a single particle, the fluidization of binary mixture of nylon and aluminum with a density ratio of 0.42, and the fluidization of binary mixture of glass and aluminum with a density ratio of 0.91. Our results show that the presence of narrow walls reduces the minimum fluidization velocity for a single particle up to 40%. We also found that in the case of binary mixture of glass and aluminum particles, uniform mixing can be easily achieved with no segregation observed; on the other hand, in the case of binary mixture of nylon and aluminum particles, significant segregation and separation are observed. Based on experimental results, correlation relationships between fluidization velocity and bed height are also reported.

A constitutive model in linear thermoviscoelasticity of polymers based on the concept of cooperative relaxation

New constitutive relations are derived for amorphous glassy polymers based on the concept of cooperative relaxation. A polymer is treated as a system of rearranging regions (flow units) embedded into a homogeneous elastic matrix. The viscoelastic (time-dependent) response of a medium is explained by rearrangements of segments of long chains in relaxing regions which occur at random instants. The kinetics of rearrangement is described in the framework of the Eyring concept of thermally activated processes, whereas the energy of any flow unit is assumed to randomly change at the instant of its reformation. Based on experimental data, phenomenological formulas are proposed for material functions. Adjustable parameters are found by fitting observations for mixtures of nylon with lithium halides in isothermal tensile relaxation tests. The thermoviscoelastic response in other tests is studied numerically. It is demonstrated that the material behavior predicted by the constitutive model in non-isothermal tests substantially differs from that predicted by conventional models whose adjustable parameters are determined by using the same experimental data.

CASE FURNISHING MATERIALS CAUSE SULPHIDE CORROSION

In 1965, the Field Museum in Chicago opened an exhibit of its unique collections of Tibetan artifacts. All aspects of everyday and religious life were represented by objects made from a wide variety of materials. Of particular interest are the objects made of metal, especially silver. The exhibit involved three walk-in cases which were unusually tightly sealed. Great pride was taken in the modern appearance of the exhibit: innovative materials had been used to furnish the cases. The floor of the cases was covered with carpeting and there was vinyl wallpaper on all interior walls as well as on top of all horizontal surfaces of the tables inside the cases. Shortly after installation, a black bushy crystal growth appeared on some of the copper and silver objects. These crystals were brushed off, but reappeared within months. For the next 26 years, crystals continued to grow on the pieces and were periodically brushed off. In 1991, the affected objects were removed for conservation treatment and the source of the problem was sought. The carpet was immediately suspect, and a sample was taken for testing. The pile consisted of a mixture of nylon and wool fibers, backed with a coarse, loosely woven burlap adhered with a thick layer of a black, rubbery substance. Analysis showed this substance to be the synthetic rubber, poly-I-butene. Samples of the carpet were subjected to 'Oddy tests' [I] using silver blanks. The carpet was divided into its constituent parts and each was tested separately. Within 24 hours, all blanks were covered with a dense black layer of corrosion. While the pile fibers did produce sulphide corrosion on the blanks, the rubber backing produced the most corrosion and appeared to be the primary source of sulphur inside the cases. During 26 years of exposure to an extremely aggressive sulphurous atmosphere, the silver objects sustained severe damage. The corrosion took two forms: bushes made up of dense clusters of crystals, or a fine web of black lines. Underneath the bushy corrosion, the silver surfaces were severely pitted. On several objects, this pitting was so severe that the silver had lost its characteristic white lustre and appeared dull and gray. Underneath the web-like, or filiform, corrosion, deep channels had been eaten into the surface, badly disfiguring the appearance of the objects. On some objects, both forms of corrosion resulted in what appeared to be dc-alloying of the surface. When the corrosion was removed, the surfaces were reddish-brown in color, suggesting the preferential removal of silver. When polished, these surfaces regained the characteristic white lustre of silver. Corrosion also removed the very thin silver washes applied to the surface of many of the objects made of a copper alloy. This sulphide corrosion problem provides an extremely graphic example of the damage caused by the use of inappropriate case construction materials and furnishings. In this exhibit, seemingly innocent materials caused irreparable damage to this once splendid collection of silver objects. It is hoped that this example will convince museum personnel of the importance of testing and choosing all exhibit materials carefully and wisely. Author's address: Division of Conservation, Field Museum, Roosevelt Road at Lake Shore Drive, Chicago, IL 60605, USA.

Phase behaviour of blends of nylon 6 and lightly sulfonated polystyrene ionomers

Mixtures of nylon 6 and lightly sulfonated polystyrene ionomers (M-SPS, where MLi, Mg, Zn or Mn) exhibit lower critical solution temperature ( LCST) phase behaviour. Miscibility was a consequence of specific complex formation between the metal sulfonate and amide groups. The interactions were strongest when the cation was Zn 2+ or a transition metal such as Mn 2+. The LCST increased as the sulfonation level increased and as the cation was changed in the order of Mg 2+ + < Li + < Zn 2+ < Mn 2+. Despite large differences in the molecular weights of the two polymers, the liquid-liquid phase diagrams were symmetric about the 50/50 composition. The glass transition temperature of miscible blends showed a positive synergism due to the physical network resulting from intermolecular complex formation. Although both polymers were hygroscopic, the blends exhibited less water absorption than either of the two components alone, which was a consequence of the complex removing sites for hydrogen bonding of water. The amount of water absorption decreased when the cation was varied in the order of Mgt + > Li + > Zn2+.

X‐ray scattering from mixtures of nylon 6 and m‐cresol

X‐ray scattering from mixtures of nylon 6 and <i>m</i>‐cresol