Dielectric relaxation of poly(chlorostyrenes) and their copolymers in the primary transition region

Dielectric relaxation measurements were carried out on a series of bulk poly(chlorostyrene) homopolymers and random copolymers over the frequency range from 50 to 100 kHz and at temperatures in the neighbourhood of the glass transitions of the polymers thus encompassing the α relaxation. Homopolymers examined were polystyrene (PS), poly(2-chlorostyrene) (P2CS), poly(3-chlorostyrene) (P3CS), and poly(4-chlorostyrene) (P4CS). Copolymers were poly(styrene-co-2-chlorostyrene) (PS2CS), poly(styrene-co-4-chlorostyrene) (PS4CS), and poly(2-chlorostyrene-co-4-chlorostyrene) (P2CS4CS). The dielectric data were analysed to yield dipole moments and Kirkwood—Fröhlich correlation parameters. The shapes of the dielectric loss curves were also taken into account. Glass transition temperatures were determined by differential scanning calorimetry (d.s.c.). It was concluded that the phenyl ring rotates freely in the α relaxation regions of PS, P4CS, and P3CS, but not in P2CS. The dipole moments of the copolymers are correlated with dyad distributions calculated from reactivity ratios.     

A Comparative Study of the Potent Odorants of Different Virgin Olive Oils

The flavour of virgin olive oil was investigated by means of an aroma extract dilution analysis. A comparative study of four oil samples differing in the flavour, indicated that the following odorants were mainly responsible for the odour notes given in brackets: (Z)-3-hexenol, hexanal, (E)-2-hexenal and (Z)-3-hexenal (green), ethyl 2-methylbutyrate, (Z)-3-hexenyl acetate and ethyl cyclohexanoate (fruity), (E,E)-2,4-decadienal, (E)- and (Z)-2-nonenal (fatty) and 4-methoxy-2-methyl-2-butanethiol (black currant-like).     

Analysis of deformation processes in glassy polycarbonate using internal friction measurements during a tensile test

Internal friction has been measured by torsion at 1 Hz during tensile tests performed on glassy polycarbonate at room-temperature. Steady-state flow and transient effects have been studied during continuous tensile tests and strain-rate changes. During steady-state, internal friction and flow-stress vary in a similar way with strain-rate. But during transients, internal friction varies continuously while flow-stress passes through a maximum (or a minimum). These results are interpreted assuming that non-elastic deformation of glassy polymers requires some microscopic discontinuous processes such as motion of defects. Two parameters are considered: the velocity v and the density ρ of mobile defects. Assuming that the former is directly related to the flow stress, it has been shown that internal friction is related to the density of mobile defects ρ. This feature is used to interpret the different stages of a tensile test curve. Activation volumes for both velocity and density of mobile defects are calculated from experimental data.     

Effect of crystallization and interface formation mechanism on mechanical properties of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate

A previous study has shown that the adhesion between the film and substrate of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate was evident with the increases in barrel temperature and injection holding pressure. In this second part of the research work, the crystallinity at the interfacial region (i.e., region between the film and the injected substrate) was extensively studied using FTIR imaging, polarized light microscopy, and DSC in an attempt to determine the level of influence that crystallinity has on the interface and bulk mechanical properties. Consequently, a more thorough and clearer picture of the influence of the inserted film on the interfacial crystallinity and subsequently the substrate mechanical properties, such as peel strength and impact strength, has been revealed. The initial proposition that crystallinity could enhance film–substrate interfacial bonding has been confirmed, judging from the higher peel strength with increasing crystallinity at the interfacial region. Nevertheless, the change in crystallinity was not only confined to the interfacial region. With the film acting as heat‐transfer inhibitor between the injected resin and the mold wall, the total crystal structure of the substrate was substantially altered, which subsequently affected the bulk mechanical properties. The lower impact strength of film‐insert injection‐molded samples compared to that of samples without film inserts provided evidence of how the film could impart inferior properties to the substrate. The difference in cooling rate between the substrate and film might also cause other defects such as warpage and/or residual stress build‐up within the product. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 294–301, 2005     

Development of a eutectic freezing process for brine disposal

At the eutectic point, both ice and salt crystallize out of salt water and brine volume is minimized. Thus, continuous eutectic freezing has major potentials for brine disposal and concentration of industrial wastes. This paper presents a laboratory study of the principal unit operations: crystallization, separation, and washing. The results prove technical feasibility and underlie a conceptual design of a two-stage eutectic freezing process. Process economics are also discussed.     

Mobil Zeolite Catalysts for Monomers

It has been about 20 years since Plank, Rosinski, and Hawthorne reported their spectacular results with metal-modified zeolite cracking catalysts for more efficient production of gasoline [1]. This discovery has saved an estimated 200 million barrels of crude oil each year in the United States alone [2]. In 1972, a patent by Argauer and Landolt described the preparation of a member of a generation of new synthetic zeolites, called ZSM- 5. It was unique because of its high silica/alumina ratio and greatly reduced coking rates for reactions with hydrocarbons by comparison with known low silica zeolites [3]. This material was an early member of a series of over 50 synthetic zeolitic substances prepared in Mobil laboratories.     

Fundamental Study of Clay: XIII, Drying Behavior and Plastic Properties

The effects of nonionic, anionic, and cationic surface-active agents on yield point, plasticity, drying and firing shrinkage, dry and fired density, and rate of drying have been experimentally determined. These and other factors have been correlated on the basis of a comprehensive theory of the plastic properties and drying behavior of clay-water masses.     

Copolyester studies. I. Preparation and characterization of tetramethylene terephthalate–tetramethylene sebacate copolymers

Tetramethylene terephthalate–tetramethylene sebacate copolymers containing up to 20 mol % sebacate have been prepared and characterized. Molecular weights and distributions have been evaluated using viscometry and gel-permeation chromatography. Compositions have been established by NMR spectroscopy. Thermal properties have been studied by differential scanning calorimetry and dynamic mechanical methods. Melting and glass-transition temperatures and moduli are discussed in terms of the structural differences, particularly the effect of composition on chain flexibility. Density and thermal methods of crystallinity determination are critically discussed for these systems.