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Montmorillonite is a promising substitute for aluminum trihydroxide in flame-retardant polypropylene/aluminum trihydroxide (PP/ATH) composites. Study was made of the partial substitution of organoclay for ATH in PP/ATH composites. The total concentration of filler was kept at 30 wt%. The composites were compatibilized with two types of compatibilizer: commercial maleic anhydride functionalized polypropylene (PP-g-MA) and hydroxyl-functionalized polypropylene (PP-co-OH) prepared with metallocene catalyst. The effect of compatibilization on the morphology was studied by the transmission electron microscopy and the scanning electron microscopy. Mechanical properties were characterized by tensile and impact measurements, and flammability properties with a cone calorimeter. Addition of compatibilizer and stearic acid (SA) treatment of the ATH particles contributed to the dispersion of the fillers. Both compatibilizers produced organoclay with exfoliated structure and improved adhesion between the fillers and the matrix. Toughness improved and decomposition and flammability were reduced. POLYM. ENG. SCI., 45:1568-1575, 2005. [c] 2005 Society of Plastics Engineers, INTRODUCTION Flame retardancy is commonly introduced to polymers by adding metal hydroxide filler, such as aluminum trihydroxide (ATH). Typically about 60 wt% of filler is required, however, and this creates [...]

Fast repetition rate (FRR) fluorometry has been used successfully to investigate the variable fluorescence characteristics of cyanobacteria in oceanic Case 1 waters. In these waters, the effective absorption bands of the light harvesting pigments for photosystem II (PSII) of the dominant cyanobacterial taxa overlap with the peak of the FRR excitation at 470 nm. The effective PSII absorption of the ecologically-significant filamentous cyanophytes in the Baltic Sea--Nodularia spumigena (Mertens ex Bornet and Flahault 1886) and Aphanizomenon sp. ((L.) Ralfs ex Bornet and Flahault 1886)--is, however, restricted to beyond 550 nm. We tested the applicability of a currently commercially available FRR fluorometer to studies of these two cyanobacterial taxa. We propose that the FRR technique should not be used in studies on these taxa, or on any cyanophyte containing phycoerythrocyanin instead of phycoerythrin, the former having inefficient PSII light harvesting in the wave band of the FRR excitation. This issue should be taken into account whenever field studies utilizing the FRR system are planned in those Case 2 water bodies, in which cyanobacteria lacking phycoerythin are among the dominant phytoplankton groups.

Enclosure experiments with all combinations of N[H.sub.4] and P[O.sub.4] treatments were carried out in the northern Baltic coastal zone during the post--spring bloom growth season. Empirical models were used to identify the important 3-d treatment effects on the state and process variables governing the main plankton compartments. Moreover, dilution experiments revealed the main nutrient sources for algal growth (external pools, intracellular stores, remineralization) and estimated phytoplankton growth and feeding loss rates. Maximal (nutrient-replete) algal community growth rates were 0.1-0.7 [d.sup.-1]. Small (2-10 [micro]m) algae grew fast (0.5-1.5 [d.sup.-1]), whereas the abundant trichal blue-green algae grew very slowly. Ciliates showed a clear increase in units with positive algal response at minimum grazing estimates of 0.05-0.3 [d.sup.-1]. Initial inorganic N:P ratios were consistently low (10 [micro]m) size fractions. During the mineral N- and P-deplete late summer bloom of trichal blue-green algae, the positive P responses of chlorophyll a--normalized [sup.14]C[O.sub.2] fixation and growth rates indicated physiological P deficiency of the whole algal assemblage, but only a combined N and P addition evoked an increase in algal biomass. In early summer, low inorganic N:P ratios reflected N limitation, as commonly found in estuaries, but later, the indicative value of this ratio evaporated, evidently because of gaseous [N.sub.2] fixation by blue-green algae.

The effect of the screw configuration of a closely intermeshing co-rotating twin-screw extruder on residence time and mixing efficiency was studied for an uncompatibilized immiscible PA6/PP (80:20) bend. Alternative screw configurations were investigated systematically. The residence time distribution (RTD) was found to be a poor indicator of the total mixing efficiency, whereas the mixing intensity function yielded considerably better information. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good dispersion of the minor phase. The evolution of morphology along the screw axis depended strongly on the screw configuration. The downstream flow characteristics after the screw end determined the final morphology of the blend., INTRODUCTION The predominant commercial method of blend preparation is melt blending in an extruder. The co-rotating twin-screw extruder (co-TSE) has outstanding distributive mixing efficiency and self-wiping characteristics (1). In general, [...]

Byline: Markku T. Heino, Jukka V. Seppala A totally aromatic thermotropic liquid crystalline polymer was melt blended in a twin-screw-extruder mainly with polyethylene terephtalate and polypropylene, and the blends were injection moulded into the form of standard test specimens. Mechanical properties of the blends were studied by tensile and impact tests and the blend morphology by scanning electron microscopy. Thermal expansion coefficients and heat deflection temperatures were also determined. The blends were two-phase systems, where LCP was as small spheres or fibres in the matrix. Skin-core morphology was found. LCP improved the mechanical properties as well as thermal and dimensional stability of the thermoplastics studied. Generally, the tensile strength, elastic modulus and HDT of the matrices increased with increasing LCP content, while elongation at break and Charpy impact strength decreased. This means that the blends were stiffer but also more brittle than the matrix polymers.

A 30-year chlorophyll alpha data set from the western Gulf of Finland is presented. The trophic state of this area showed an increasing trend from the 1970s to the 1980s but then remained unchanged in the 1990s.

JUKKA V. SEPPALA [*] Biodegradable lactic acid based poly(ester-urethanes) (PEU) were polymerized and their structure and rheological properties were characterized. The polymerization process comprised two steps: lactic acid monomer was [...]