EFFECT OF POLYMERIZATION CONDITIONS ON THE MOLECULAR WEIGHT OF POLYPHENYLSILSISQUIOXANE

Samples of polyphenylsilsisquioxane (PPSQ)using CaF_2 or MgF_2 as the main catalysts hadbeen prepared under different polymerization conditions. The results were treated on anorthogonal design L_9 (3~4). All weight-average molecular weights (M_W ) of PPSQ had beenmeasured by gel permeation chromatography (GPC). Effects of polymerization conditionsincluding reaction temperature, composition of the dual catalysts (CaF_2 or MgF_2 and DCC),mixture of solvents and reaction time on M_W of PPSQ have been discussed. The quantity of thecatalysts is the most important factor that affects M_W of PPSQ. Reaction temperature is thesecond important factor. Appropriate polymerization condition has been established to get PPSQwith high M_W.

EFFECT OF POLYMERIZATION CONDITIONS ON THE LADDERLIKE STRUCTURE OF POLYPHENYLSILSESQUIOXANE

The ladderlike structure of PPSQ synthesized by-using four kinds of catalysts (MgF2, LiF, KOH and DCC) at different polymerization conditions has been investigated by IR and NMR. In the system using MgF2 as the main catalyst, the most important factor which affects the ladderlike structure of PPSQ is the composition of the dual catalysts, MgF2 and DCC. PPSQ prepared by using KOH as the catalyst has the highest regularity of ladderlike structure among all samples. PPSQ with different degree of ladder regularity can be obtained by choice of polymerization conditions.

Experimental Measurements of the Sensitivity of Fiber-optic Bragg Grating Sensors with a Soft Polymeric Coating under Mechanical Loading,Thermal and Magnetic under Cryogenic Conditions

The strain and temperature sensing performance of fiber-optic Bragg gratings （FBGs） with soft polymeric coating, which can be used to sense internal strain in superconducting coils, are evaluated under variable cryogenic field and magnetic field. The response to a temperature and strain change of coated-soft polymeric FBGs is tested by comparing with those of coated-metal FBGs. The results indicate that the coated-soft polymeric FBGs can freely detect temperature and thermal strain, their At variable magnetic field, the tested results indicate accuracy and repeatability are also discussed in detail. that the cross-coupling effects of FBGs with different matrixes are not negligible to measure electromagnetic strain during fast excitation. The present results are expected to be able to provide basis measurements on the strain of pulsed superconducting magnet/cable （cable- around-conduit conductors, cable-in-conduit conductors）, independently or utilized together with other strain measurement methods.

Bearing capacity of concrete filled bidirectional FRP tube subjected to axial compression

External confinement by fiber reinforced polymer (FRP) is an efficient technique to increase the bearing capacity and ductility of concrete. To better study the mechanical behavior of bidirectional FRP confined concrete, the yield criterion of bidirectional FRP is presented based on the static equilibrium condition in this paper, and a model for calculating the bearing capacity of bidirectional FRP confined concrete is established. The model can capture the character of bidirectional FRP confined concrete. Effects of the confinement effect coefficient, the unconfined concrete strength and the material properties of FRP on bearing capacity are analyzed. Results show that each parameter has different effects on the bearing capacity of bidirectional FRP confined concrete.