Practical and theoretical molecular weights in polyaddition reactions of ethylene and propylene oxide

The addition reactions of ethylene oxide and/or propylene oxide catalyzed by KOH and initiated with compounds containing free hydroxyls are followed by secondary reactions which vary the expected molecular weight. By using ethylene oxide, diols are formed and by using propylene oxide, both diols and unsaturated monofunctional compounds are formed. These products are usually characterized by their hydroxyl number. The average molecular weight is found by taking into consideration the starter functionality only. There are often some behavioral differences among similar products owing to the different quantity and chain length of the secondary products contained therein. The secondary products are analyzed and the quantity of the secondary products were determined from the hydroxyl number values and from the unsaturation of reagents and products. In the case of monofunctional adducts using the calculation method, the results have been experimentally confirmed.     

Recycled poly(ethylene terephthalate) and its short glass fibres composites: effects of hygrothermal aging on the thermo-mechanical behaviour

This paper reports on the effects of hygrothermal aging at 70 °C in water and at 80% relative humidity, on the thermo-mechanical properties, molar mass and microstructure of recycled poly(ethylene terephthalate) (rPET) and its short glass fibres composites.For all the investigated materials, the elastic mechanical properties (tensile and storage moduli) determined at low strain levels resulted practically unaffected by hygrothermal aging under the selected conditions. On the other hand, a marked reduction of the tensile strength and apparent fracture toughness has been observed for rPET matrix and its composites during hygrothermal aging, more markedly for materials immersed in water than for those aged at 80% RH. Both properties resulted to be related on the molar mass of the rPET matrix, that decreased during hygrothermal aging as a consequence of the hydrolysis process.The materials glass transition, evaluated as the temperature of the loss factor peak, increased during hygrothermal aging due to the progressively restricted mobility of the amorphous phase caused by a concurrent crystallinity increase. This crystallization process (chemicrystallization) is favoured by temperature, by the plasticizing effect of water and by the reduction of molar mass.Consistently with the mechanical measurements, the morphology of fracture surfaces exposed to hygrothermal aging in water revealed a reduction of plastic deformation of the rPET matrix and a weakening of the fibre-matrix interface for rPET composites.     

Grafted polypropylene membranes for purification of water containing sodium alkylbenzenesulfonate

The possibility of eliminating sodium alkylbenzenesulfonate (ABS) from water by reverse osmosis was examined by operating with polypropylene membranes grafted with poly(acrylic acid). Flux through the membranes decreases with increasing thickness. For 23μ thickness and 0.5 1./hr-m² flux, the rejection is 100% (operating pressure, 50 atm: concentration, 1 g ABS/l.). For 5μ thickness the rejection is lower and is related to ABS concentration: rejection increases with increasing concentration and reaches 60% for concentrations higher than 5 g ABS/l. (flux, 51./hr-m²; operating pressure, 50 atm). This is ascribed to the prevailing ultrafiltration as regards the reverse osmosis. ABS, at higher concentrations than the critical value, gives micelles whose dimensions might be compared to pores. The membrane behavior is influenced by previous treatments; when the membrane has been conditioned in NaCl solution, it is more selective and more permeable; the rejection reaches 90% with fluxes of 6.8 l./hr-m² for concentrations of 5 g ABS/1. (operating pressure, 50 atm). In order to relate the properties to the structure of membranes, we have examined them by electron microscope. The ion exchange which takes place between membrane and NaCl and between membrane and ABS has also been studied.     

Social influences on creativity: The effects of contracted-for reward.

Three studies, with 195 5–11 yr olds and 60 female undergraduates, tested the hypothesis that explicitly contracting to do an activity in order to receive a reward would have negative effects on creativity, but receiving no reward or only a noncontracted-for reward would have no such negative effects. Children performed story-telling and collage-making tasks and were rewarded with an activity, while undergraduates performed the collage-making task and were paid or not paid for their participation. All 3 studies supported the hypothesis. This support appeared to be strong and generalizable across different S populations, reward types, reward presentations, and creativity tasks. Possible mechanisms for the phenomenon are discussed in terms of choice, intrinsic motivation, and the labeling of the task. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of external evaluation on artistic creativity.

Examined the conditions under which the imposition of an extrinsic constraint upon performance of an activity can lead to decrements in creativity. 95 female undergraduates worked on an art activity either with or without the expectation of external evaluation. In addition, Ss were asked to focus on either the creative or the technical aspects of the activity or they were given no specific focus. Finally, some Ss expecting evaluation were given explicit instructions on how to make their artworks. As predicted, Ss in the evaluation groups produced artworks significantly lower on judged creativity than did Ss in the nonevaluation control groups. The only evaluation group for which this pattern was reversed had received explicit instructions on how to make artworks that would be judged creative. A possible reconciliation of these 2 disparate results is proposed, and practical implications are discussed. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivation and creativity: Effects of motivational orientation on creative writers.

72 members of the college community who identified themselves as actively involved in creative writing participated in individual laboratory sessions, in which they were asked to write 2 brief poems, to investigate the hypothesis that intrinsic motivation is conducive to creativity and extrinsic motivation is detrimental. In the present study, intrinsic motivation was defined as resulting from an S's interest in and enjoyment of writing for its own sake, while extrinsic motivation was defined as resulting from the external things obtained by writing (e.g., rewards, approval). Ss were divided into approximately equal groups that were designated as intrinsic-orientation, extrinsic-orientation, and control conditions. Before writing the 2nd poem, Ss in the intrinsic-orientation condition completed a questionnaire on intrinsic reasons for being involved in writing, and Ss in the extrinsic-orientation condition completed a questionnaire on extrinsic reasons. Ss in the control condition were not given a questionnaire on reasons for writing. Results indicate that, although there were no initial differences between conditions on prior involvement in writing or on creativity of the 1st poems written, there were significant differences in the creativity of the poems written after the experimental manipulations. Poems written under an extrinsic orientation were significantly less creative than those written in the other 2 conditions. Implications for social-psychological and individual-difference conceptions of creativity are discussed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermal,thermo‐mechanical,and dynamic mechanical properties of polypropylene/cycloolefin copolymer blends

Interaction of the components and physical properties of the polypropylene (PP)/cycloolefin copolymer (COC) blends were studied by means of differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), Vicat softening temperature (VST), and measurements of the coefficient of linear thermal expansion (CLTE) and of the density. The attention was focused on the blends with 90–60% of PP by wt, where the COC minority component was present in the form of short fibers. DSC, DMTA, and density measurements concurrently prove the immiscibility of PP and COC. DSC measurements reveal that crystallinity and melting temperature of the PP component slightly decrease with the fraction of COC in blends, in the range of 56–47% and 164–161°C, respectively. Storage modulus and loss modulus of the blends are in a good accord with the model predictions based on (i) the equivalent box model (EBM) and on (ii) modified equations of the percolation theory. The dependence of the VST on the blend composition is in a good correlation with the previous morphological analysis. Measurements of the coefficient of thermal expansion provide useful data as the functions of temperature and blend composition. Density of the blends was found to obey the volume additivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Interaction between water and polytrans-2,5-dimethylpiperazin thiofurazanamide films

Dense films of polytrans-2,5-dimethylpiperazin thiofurazanamide (DMP-TFZ) were characterized as to their physical properties and sorption isotherms. They appeared to be amorphous, endowed with high Tg (247°C), and high mechanical stiffness.Sorption and desorption equilibrium curves were obtained at 23°C for samples 26 and 36 μm thick; hysteresis phenomena were observed only in the desorption steps. BET and Burhoff-Pusch theories and best fit calculations allowed to find that the water layers on the active sorption centers are n = 5 and 1.6 respectively.The Zimm water cluster integral G₁₁/v₁ shows that water tends to be split in single adsorbed molecules in a large field of activities, but that cluster formation is unavoidable in the presence of liquid water. Infrared analysis of the OH stretching region of films conditioned at different relative humidity (RH), demonstrates that water hydrogen bonds in the sorbed state are weaker than in the liquid state and that the presence of big water clusters able to dissolve salts must be excluded. The close packing and high rigidity of the chains should be responsible for the free volume small size holes and uniform distribution, which does not allow big water clusters.