No abstract

Thermal and thermo-oxidative decomposition and decomposition kinetics of flame retardant high impact polystyrene (HIPS) with triphenyl phosphate (TPP) and novolac type epoxy resin (NE) were characterized using thermo-gravimetric experiment. And the flammability was determined by limited oxygen indices (LOI). The LOI results show that TPP and NE had a good synthetic effect on the flame retardancy of HIPS. Compared with pure HIPS, the LOI values of HIPS/NE and HIPS/TPP only increased by about 5%, and the LOI value of HIPS/TPP/NE reached 42.3%, nearly 23% above that of HIPS. All materials showed one main decomposition step, as radical HIPS scission predominated during anaerobic decomposition. TPP increased the activity energy effectively while NE affected the thermal-oxidative degradation more with the help of the char formation. With both TPP and NE, the materials could have a comparable good result of both thermal and thermal-oxidative degradation, which could contribute to their effect on the flame retardancy.

Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (Tg's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher Tg's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004

In order to reduce the damage of blasting to rock mass and improve the half-hole rate of presplitting blasting, the dynamic finite element analysis software ANSYS/LS-DYNA is used to simulate and analyze the action process of sequential controlled blasting. The effects of the detonation delay time of the postblasting hole and the hole spacing of the postblasting hole on the crack formation of the sequential controlled presplitting blasting are studied. The results show that when the blast hole with a diameter of 42 mm is used for sequential controlled presplitting blasting and the first blast hole pitch is 60 cm, the reasonable detonation delay time is 80∼120 μs. When the detonation delay time is 80 μs, the reasonable postblast hole spacing is 60 cm. Field tests show that when reasonable optimized blasting parameters are used, presplit blasting with sequential control can reduce drilling workload and explosive consumption. The sequential controlled presplitting blasting not only increases the hole spacing but also plays a better role in protecting the surrounding rock.