The development of crazes in thin films of glassy polymers is a result of a micronecking process. Hence, when sandwiched between ductile poly(phenylene oxide) (PPO) films, a brittle glassy polystyrene (PS) film can be plastically deformed to very large strains without crazing or cracking. However, the stability of this superplastic behavior is strongly dependent upon thickness of the outer ductile films. A sharp ductile−brittle transition in the sandwich thin film structure was observed as the PPO thickness decreased. A simple mechanical model built upon the competition between the necking force, associated with crazing, and the constraining force, due to the ductile films, was utilized to analyze the stability of this superplasticity. The result of the mechanical analysis is in good agreement with the experimental data. The mechanical calculation indicates that the constraining force from the outer layers should be at least 60 MPa greater than the necking force to ensure the superplasticity. The defect size corresponding to this excess constraining stress is around 18 nm, comparable in size of the correlation length of polystyrene chains.

Cure reactions of a bismaleimide (4,4 0-bismaleimidodiphenylmethane, BMI) associated with a liquid aromatic dicyanate ester (1,1 0-bis(4-cyanatophenyl)ethane, BEDCy) and with a powder type aromatic dicyanate ester (bisphenol A dicyanate, BADCy) were investigated by in situ FTIR and DSC dynamic scanning. In non-catalyzed blend systems, co-reactions between dicyanate ester and bismaleimide always occur, and hence the formation of pyrimidine and/or pyridine structures take place. Pyrimidine structures always predominate. Probable reaction paths were also proposed for various formulations of hybrid blends. In addition, N-phenylmaleimide (MI) and p-phenyl-phenylcyanate (S-Cy) were utilized as model compounds and mixed via a melting method and a solution method to explore the corresponding cure reactions by means of FTIR, DSC and NMR. 13 C NMR spectra of the model compounds demonstrated the formation of linkages of sym-triazine rings, pyrimidine structures, pyridine structures and dioxazine structures. The reaction mechanism or linkage structures produced in the model compound system studied may be somewhat different from those of the real system due to a diffusion effect in real systems or to the different activation energy in both systems. q

The nanoscopic interactions between glassy macromolecules and the dispersed single-walled carbon nanotubes (SWCNTs) in a nanocomposite during very large local elongations were revealed. The results also unveiled a unique mode of molecular motions followed by glassy chains during brittle nanoplastic flows. Based on detailed nanomechanical calculations on results from atomic force and electron microscopy, the molecular motions of the “strain-softened” glassy polymer chains were found highly dependent on chain entanglement density (νe), in sharp contrast to the νe-independent elastic reinforcement. Particularly, in the loosely entangled chains the SWCNTs behaved like “phantom tubes”, manifesting no effects on strain hardening of the chain network during plastic flow. This indicates that the “glassy” chains had undergone entanglement clustering, a new and unique mode of nonaffine molecular motions. The results bear important significance in revealing the fundamental behavior of glassy polymer chains and the reinforcement by SWCNTs.

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The T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradation.