No abstract

Carbon-based nanomaterials, such as carbon nanotubes, are well-known for their unique physical properties. They have attracted interest as reinforcing fillers because of their superb mechanical properties (Young’s modulus ≥1 TPa and tensile strength = 100–150 GPa). However, the success of the reinforcement has been limited because of their tendency to form agglomerates in polymer matrices. We report the excellent reinforcement properties of polymer nanocomposites by the incorporation of nanodiamond (ND). ND has been expected to offer polymer nanocomposites optimal properties because of its smooth surface and excellent optical, mechanical, and thermal properties, which can approach the values of single diamond crystal. We prepared poly(vinyl alcohol) (PVA)/ND nanocomposites by a simple casting method from aqueous medium and achieved the high dispersibility of ND in the PVA matrices. The resulting nanocomposites had excellent properties derived both from ND and PVA. The Young’s modulus of the nanocomposites in particular increased 2.5 times compared with that of PVA film with only 1 wt % ND loading. For the thermal properties, the thermal conductivity of the nanocomposites increased dramatically, much above the calculated values, especially at a low content of ND. Furthermore, it was revealed that PVA/ND nanocomposites remained high transparency of PVA even if ND particles were imparted. We anticipate that ND will be able to compete as a nanofiller against conventional carbon-based nanofillers for polymer composites, and it is possible their reinforcement properties will be extended in the future.

The initial stage of fiber structure development in the continuous neck-drawing of amorphous poly(ethylene terephthalate) fibers was analyzed by in-situ wide-angle x-ray diffraction, small-angle x-ray scattering, and temperature measurements. The time error of the measurements (< 600 μs) was obtained by synchrotron x-ray source and laser irradiation heating. A highly ordered fibrillar-shaped two-dimensional (smectic-like) structure was found to be formed less than 1 ms after necking. By analyzing its (001') and (002') diffractions, the length of the structure 60-70 nm were obtained. A three-dimensionally ordered triclinic crystal began to form with the vanishing of the structure around 1 ms after necking. The amount and size of the crystal were almost saturated within several milliseconds of necking, during which time a mainly exothermic heat of crystallization was also observed.

No abstract

A successful scaffold for use in tendon tissue engineering requires a high affinity for living organisms and the ability to maintain its mechanical strength until maturation of the regenerated tissue. We compared two types of poly(L-lactic acid) (PLLA) scaffolds for use in tendon regeneration, a plain-woven PLLA fabric (fabric P) with a smooth surface only and a double layered PLLA fabric (fabric D) with a smooth surface on one side and a rough (pile-finished) surface on the other side. These two types of fabric were implanted into the back muscles of rabbits and evaluated at three and six weeks after implantation. Histological examination showed collagen tissues were highly regenerated on the rough surface of fabric D. On the other hand, liner cell attachment was seen in the smooth surface of fabric P and fabric D. The total DNA amount was significantly higher in fabric D. Additionally, mechanical examination showed fabric P had lost its mechanical strength by six weeks after implantation, while the strength of fabric D was maintained. Fabric D had more cell migration on one side and less cell adhesion on the other side and maintained its initial strength. Thus, a novel form of double-layered PLLA fabric has the potential to be used as a scaffold in tendon regeneration.