Synthesis and properties of some polyesters with mesogenic groups and flexible spacers in the main chain

Polymers containing, in the main chain, various mesogenic moieties separated by flexible spacers have been prepared by condensation of the corresponding diphenol or diol with an aliphatic diacid chloride. The polymers have been characterized by X-ray, d.s.c. and polarizing microscopy. The diacids used were sebacic (SEB), succinic (SUC) and 3-methyladipic (MAA). The biphenols were 4-hydroxyl-N-benzylidene-4′-hydroxyaniline(1), 4.4′-biphenol(2), 4,4′-bis (2-hydroxyethoxy)-biphenyl(5) and 3,3′-dimethyl-4,4′-di(2-hydroxyethoxy)-stilbene(7). The polymers SEB-1 and SEB-2 were classified as giving thermotropic lamellar mesophases; SEB-5, SEB-7 and SUC-5 as potentially nematic; MAA-2 and SUC-2 gave crystalline polymers.     

Multiple melting endotherms of poly(ethylene terephthalate)

Poly(elhylene terephthalate) samples were isothermally crystallized from the melt on a differential scanning calorimeter. Subsequent fusion showed three endotherms under many crystallization conditions. These three peaks are attributed to melting of crystallites formed daring primary and secondary crystallization processes and to fusion of crystals formed during recrystallizatlon during the melting scan.     

STATE ESTIMATION OF BUBBLE FREQUENCY AND VELOCITY IN A BUBBLING FLUIDIZED BED

Bubble frequency and velocity in a bubbling fluidized bed are estimated by combining advanced estimation theory and the cross correlation function of pressure measurements. The cross correlation function is shown to be a mathematical function of bubble frequency and velocity. Sequential weighted least squares and a version of Kalman filtering are used to compute optimal estimates of these bubble parameters for fluidization in the bubbling/near slugging regime. The dynamics of both algorithms are studied in response to simulated step changes in fluidizing air flow.