Masaya Kawasumi

Mechanical properties of nylon 6-clay hybrid

Various nylon 6-clay hybrids, such as molecular composites of nylon 6 and silicate layers of montmorillonite and saponite, NCHs and NCHPs, respectively, have been synthesized. To estimate the mechanical properties of these hybrids, tensile, flexural, impact, and heat distortion tests were carried out. NCH was found superior in strength and modulus and comparable in impact strength to nylon 6. The heat distortion temperature (HDT) of NCH (montmorillonite: 4.7 wt. %) was 152 °C, which was 87 °C higher than that of nylon 6. In NCHP, saponite had a smaller effect on the increase of these mechanical properties. The modulus and HDT of NCH and NCHP increased with an increase in the amount of clay minerals. It was found that these properties were well described by the contribution of the constrained region calculated from the storage and loss modulus at the glass transition temperature. According to the mixing law on elastic modulus, the following expression was obtained between the modulus E at 120 °C and the fraction of the constrained region C, E n = E c n = C , where the values of n and E c (modulus of the constrained region) were 0.685 and 1.02 GPa, respectively.

Synthesis of nylon 6-clay hybrid

It was found that montmorillonite cation exchanged for 12-aminolauric acid (12-montmorillonite) was swollen by ∊-caprolactam to form a new intercalated compound. Caprolactam was polymerized in the interlayer of montmorillonite, a layer silicate, yielding a nylon 6-clay hybrid (NCH). The silicate layers of montmorillonite were uniformly dispersed in nylon 6. The carboxyl end groups of 12-aminolauric acid in 12-montmorillonite initiated polymerization of ∊-caprolactam, and as 12-montmorillonite content became larger, the molecular weight of nylon was reduced. From the result of end-group analysis, carboxyl end groups were more than amino end groups. The difference between the carboxyl and the amino end groups was attributed to ammonium cations (-NH 3 + ) of nylon molecules, because the difference agreed with the anion site concentration of the montmorillonite in NCH. It is suggested that the ammonium cations in nylon 6 interact with the anions in montmorillonite.

Swelling behavior of montmorillonite cation exchanged for ω-amino acids by -caprolactam

Natural Na-montmorillonite was cation exchanged for the ammonium cations of various ω-amino acids [H 3 N + (CH 2 ) n −1 COOH, n = 2, 3, 4, 5, 6, 8, 11, 12, and 18]. X-ray diffraction (XRD) results suggested that the chain axes of ω-amino acids with a carbon number of eight or less were parallel to the silicate layers, and that the chain axes of those with a carbon number of 11 or more were slanted to the layers. The cation-exchanged montmorillonites form intercalated compounds with ∊-caprolactam at 25 °C. The montmorillonites intercalated with both ω-amino acid and ∊-caprolactam were studied by XRD measurement at room temperature and 100 °C. We propose a model where amino acid molecules were arranged perpendicular to silicate layers and ∊-caprolactam molecules filled the space between them. When the ∊-caprolactam was melted at 100 °C, the basal spacing for the montmorillonite increased, in which the carbon number exceeds 11. This phenomenon will be applicable to obtaining the nylon 6-clay hybrid, a molecular composite of nylon 6 and montmorillonite.

Preparation and mechanical properties of polypropylene‐clay hybrids using a maleic anhydride‐modified polypropylene oligomer

Polypropylene-clay hybrids (PPCH) were prepared using a maleic anhydride-modified PP oligomer (PP-MA) as a compatibilizer. PP was melt-blended with organophilic clay which was intercalated with PP-MA. In these PPCHs, the particles of silicate layers were dispersed at the nanometer level. The particles became smaller and were dispersed more uniformly, as the ratio of PP-MA to the clay was increased. The dynamic storage moduli of the PPCHs were higher than that of PP up to 130°C. For example, the modulus of the PPCH with 5 wt % clay and 22 wt % PP-MA was 1.8 times higher compared to that of PP at 80°C. As the dispersibility of the clays was improved, the reinforcement effect of the clays increased.

Nylon 6–Clay Hybrid

ζ-Caprolactam was polymerized in the interlayer spacing of montmorillonite, a clay mineral, yielding a nylon 6-clay hybrid (NCH) 1) . X-ray and TEM measurements revealed that each template of the silicate, which is 10 A thick, was dispersed in the nylon 6 matrix and that the repeat unit increased from 12 A in unintercalated material to 21 A in the intercalated material. Thus NCH, is a “polymer based molecular composite” or “nanometer composite”. NCH, when injection-molded, shows excellent properties as compared to nylon 6 in terms of tensile strength, tensile modulus and heat resistance. Heat distortion temperature increased from 65 °c for nylon 6 to 152 °c for NCH, containing 4 wt% (1.6 vol%) of clay mineral.

Preparation and mechanical properties of polystyrene–clay hybrids

Polystyrene–clay hybrids (PSCHs) were prepared by melt blending a styrene vinyloxazoline copolymer with organophilic clay. In the PSCHs, the silicate layers of the clay were delaminated and dispersed homogeneously to the nanometer level. The moduli of the PSCHs were higher than that of the PS copolymer. For example, the tensile modulus of the PSCH with 5 wt % clay was 1.4 times higher compared to that of the PS copolymer.

Cell performances of direct methanol fuel cells with grafted membranes

Cell performances were evaluated with grafted polymer membranes as an electrolyte for a direct methanol fuel cell (DMFC). The membranes were prepared using a poly(ethylene-tetrafluoroethylene), or ETFE, film. The base polymer film was added to sulfonic groups using γ-radiation activated grafting technique as ion-exchange groups. These membranes had more suitable properties for DMFCs, i.e. higher electric conductivity and lower methanol permeability than perfluorinated ionomer membrane (Nafion). Nevertheless, the cell performance with the grafted membrane was inferior to that with Nafion. The analysis of electrode potentials vs. reversible hydrogen electrode showed larger activation overpotential for both the electrodes on the grafted membranes. We concluded that this is due to poor bonding of the catalyst layers to the grafted membranes.

Nematic liquid crystal/clay mineral composites

Abstract Novel liquid crystalline composites composed of a nematic low molar mass liquid crystal and a few percents of organized clay minerals have been prepared. The affinity of the organized clay minerals for the liquid crystal, which was evaluated by measuring their contact angles, was highly dependent on the kind of organic ammonium cations used for the organization of the clay. In the case of an organized clay having good affinity for the liquid crystal, the organized clay was dispersed homogeneously in the liquid crystal in the size of several micron meters. The composites exhibited so-called multidomain textures composed of a few micron meters domains of the liquid crystal. The composites were sandwiched between transparent conductive ITO coated glasses with 12 μm polymer beads as a spacer and their electro-optical properties were measured. The composite cells exhibited a bistable and reversible electro-optical effect between a light scattering state and transparent state. Both the states including intermediate states between them could be selected by changing the frequency and voltage of applied electric fields. The memory effect exhibited by the composites based on the nematic liquid crystal is rather unusual since most of conventional nematic liquid crystals do not exhibit such a memory effect due to their low viscosity. The memory mechanism exhibited by the composites was proposed.

Liquid crystal/clay mineral composites

Abstract Novel liquid crystalline composites composed of a nematic two-frequency addressing liquid crystal (TFALC) and a few percents of various types of organized clay minerals (LCC) have been prepared. The affinity of the organized clay minerals for the liquid crystal, which was evaluated by measuring their contact angles, was highly dependent on the kind of organic ammonium cations used for the organization of the clay. In the case of an organized clay having good affinity for the liquid crystal, the organized clay was dispersed homogeneously in the liquid crystal in the size of several micron meters. Also, the LCCs were stable enough against sedimentation or aggregation under an electric field. The LCCs were sandwiched between transparent conductive In/SnO2 (ITO)-coated glasses with 12 μm polymer beads as a spacer and their electro-optical properties were measured. The LCC cells exhibited a bistable and reversible electro-optical effect between a light scattering state and transparent state. The contrast between the light scattering and transparent memory states is highly dependent on the kind of the organized clays. The LCCs based on the organized clays with better affinity for the liquid crystal exhibited relatively higher contrast. The memory effect exhibited by the LCCs is rather unusual since most of conventional nematic liquid crystals do not exhibit such a memory effect due to their low viscosity. Their memory mechanism was proposed.

Novel memory effect found in nematic liquid crystal/fine particle system

Abstract Novel liquid crystalline composites composed of a nematic two-frequency-addressing liquid crystal and organized clay mineral (about 1 wt %) have been prepared. The particles of clay mineral were dispersed homogeneously in the liquid crystal. The composite cells became transparent within 50ms when a 60 Hz electric field was applied. The transparent state was maintained after the field was switched off. It transformed into a turbid light scattering state by applying 1.5 kHz electric field which caused dynamic scattering in the cell. The light transmittance of both memory states did not change after 20 h without the electric field.