SYNOPSISNylon 6-clay hybrid ( N C H ) is a molecular composite of nylon 6 and uniformly dispersed silicate layers of montmorillonite. We found that the phase with the high melting temperature (HMT phase) in the NCH annealed under elevated pressure. The melting temperature of the H M T phase was 240°C. Nylon 6 annealed under elevated pressure did not have the H M T phase. Thus, the presence of the H M T phase was characteristic of the NCH. The relative heat of fusion of the H M T phase (heat of fusion of H M T phase/heat of fusion in the pressure annealed NCH ) increased with increase in pressure. High-pressure differential thermal analysis (DTA) measurement revealed that the temperature, a t which the relative heat of fusion showed a maximum value, was below about 20°C of the melting temperature of the original NCH under elevated pressure. It was considered that the nylon 6 crystallite near the melting temperature and the molecular mobility under elevated pressure were necessary to the appearance to the H M T phase. 0 1994 John Wiley & Sons, Inc. I NTRO D UCTlO NNylon 6-clay hybrid ( N C H ) is a molecular composite of nylon 6 in which silicate monolayers of montmorillonite, 1 nm in thickness and 100 nm in width, are uniformly dispersed.'-4 NCH is readily processed in the molten state by injection molding or extrusion molding. It is well known that high pressure above 0.3 GPa strongly enhances the rate at which polyethylene crystallizes in extended forms. Extended-chain crystal (ECC) of polyethylene is grown either by pressure-induced crystallization or by annealing of folded chain crystal near the melting temperature, as was reported by Rees and Bassett.' The melting temperature and the crystallinity of the polyethylene with ECC are higher than those of folded-chain crystals of p~lyethylene.~ In the NCH annealed under elevated pressure, it is expected that the melting temperature and the crystallinity are increased due to the growing of the ECC.In this study, the NCH was crystallized by annealing under elevated pressure above 0.15 GPa. The
Optical limiters exhibit a fixed intensity of transmitted light at high incident light levels. The limiter can serve as protecting sensor and eye. The Ceo solution shows the excellent optical-limiting property compared with many other optical-limiting materials.1 For optical-limiting application, a solid-state optical limiter is desirable, but the performance of Ceo in poly(methyl methacrylate) as a solid polymer was low compared with that of the Ceo solution.2 Here we described the opticallimiting study of a solid-state polystyrene-bound Ceo and demonstrated that this polymer improved the opticallimiting performance of the Ceo solution. The polymer was created by a high-pressure polymerization of styrene in the presence of Ceo-The optical-limiting tests were performed with a pulse laser beam at 532 nm, and the limiting was about 5 times greater than that of a Ceo solution.Buckminsterfullerene (Ceo) is a soluble new form of carbon3 and can be obtained by evaporating graphite electrodes in an atmosphere of ~100 Torr of helium.4 The combination of this molecule with polymer is challenging. The polymeric fullerene derivatives were prepared in the previous papers.5-7 We expected that the optical clear polymer-bound Ceo would be a very
Nylon 66/mesoporous molecular sieve (pore diameter: 2.7 nm) composites were prepared by annealing mixtures of nylon 66 and mesoporous molecular sieve (FSM) powders under high pressures and high temperature (FSM content: 0 -60 wt %; pressure: 0.5-30 MPa; temperature: 300°C; time: 1 h). X-ray diffraction and TEM measurements indicated the presence of the pores of FSM in the composite. Above 2 MPa, nylon 66 was charged in the pores of FSM. The fraction of the charged nylon 66 increased with pressure and was independent of the FSM content (pressure: 2-30 MPa; fraction of charged nylon 66: 54 -66%). The infrared spectrum of the composite showed the bands based on SiOO, COH, NOH, CAO. DSC measurement indicated that the heat of fusion of nylon 66 crystallite in the FSM pores was low compared with that of nylon 66. The composites prepared above 2 MPa were found to be superior in storage modulus to nylon 66. The modulus increased with an increase in the fraction of charged nylon 66 and the amount of FSM.
SynopsisLittle is known of the rheology of polymer melts in the high shear rate up to 106 s-1 or more. A specially designed high-shear-rate rheometer was developed, by which the rheology of polymer melts for shear rates up to 108 s-l can be investigated. Two non-Newtonian regions and a transition or the second Newtonian region were observed in the wide range of shear rates up to lo7 s-l . The observed flow curves for various polymer melts are classified into three typical patterns. One is the flow curve typically shown of highdensity polyethylene in which a clear second Newtonian region appears after the first non-Newtonian region. The second is the typical flow curve of polystyrene in which a "transition region" appears instead of the second non-Newtonian region. The third is the flow curve shown of acrylonitrile-styrene copolymer, which exhibits behavior between the two types. A generalized flow curve is proposed to explain the observed flow behaviors of various polymers over a wide range of shear rates. The flow behavior in high shear rate results from high orientation and scission of polymer molecules.
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