Nylon

The

The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight (UHPPH) and broad molecular weight distribution (MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200℃, whose loss modulus (G") plots at 180 and 200℃ versus the natural logarithm of angular frequency (w) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100rad/s for Ziegler-Natta catalyzing ethylenepropylene random copolymerization (PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G" (w) us. Lnw curves for UHPPH. This makes it possible to determine the plateau modulus (G0N) of UHPPH from a certain experimental temperature G"(w) curve directly. For UHPPH, the G0N determined to be 4.28×105 and 3.62×105 Pa at 180 and 200℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G0N has no relation to the molecular weight.

Two

A novel nanocomposite composed of polybenzoxazine (PBZ) and multiwalled carbon nanotubes (MWNT) was prepared successfully. The surface modification of MWNT, including nitric acid modification followed by toluene-2,4-diisocyanate (TDI) treatment, introduced hydroxyl, carboxyl, and isocyanate groups on the MWNT surface. The surface carboxyl groups catalyzed the ring-opening reaction of benzoxazine and thus decreased the curing temperature of the system. The isocyanate groups reacted with the phenolic hydroxyl groups generated by the ring opening of benzoxazine resulting in the significant improvement of the adhesion between PBZ and MWNT. Dynamic mechanical analyses indicated the increase of storage modulus as well as Tg by the addition of MWNT into PBZ. A well dispersed modified-MWNT on nanoscale level inside PBZ matrix was observed by TEM and SEM.