-Heat and drought were extreme in summer 2003 in Europe. Climatic data show that most extreme were maximum air temperatures in June and August; maps of these two months show a striking similarity in geographical range. Over wide regions, monthly mean temperatures were more than

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An excess of anionic surfactant at the surface of waterborne acrylic pressure-sensitive adhesives (PSAs) is identified through the complementary use of atomic force microscopy and elemental depth profiling with Rutherford backscattering spectroscopy. This surfactant is distributed around the particles at the film surface, where it presumably contributes to the stabilization of the particles against coalescence. This result is not consistent with the prediction of a process model of film formation that a coalesced skin layer should form, owing to the polymer's low zero-shear-rate viscosity (5 × 10 4 Pa s). To investigate the reason for the surface excess, the spatial distribution of water during film formation of the latex PSAs has been determined using magnetic resonance profiling. In the later stages of drying, the water concentration is very low near the surface, and it increases linearly with the depth into the film. The water profiles indicate that the deformation of particles is not accompanied by coalescence but that water-filled capillaries exist at particle boundaries. It is suggested that the transport of surfactant (and water-soluble polymer, ions, and other species) to the surface is driven by the capillary pressure.

Abstract. Tackifying resins (TR) are often used to improve the adhesive properties of waterborne pressure-sensitive adhesives (PSAs) derived from latex dispersions.There is a large gap in the understanding of how, and to what extent, the film formation mechanism of PSAs is altered by the addition of TR. Herein, magnetic resonance profiling experiments show that the addition of TR to an acrylic latex creates a coalesced surface layer or "skin" that traps water beneath it. Atomic force microscopy of the PSA surfaces supports this conclusion. In the absence of the TR, particles at the surface do not coalesce but are separated by a second phase composed of surfactant and other species with low molecular weight. The function of the TR is complex.. According to dynamic mechanical analysis, the TR increases the glass transition temperature of the polymer and decreases its molecular mobility at high frequencies. On the other hand, the TR increases the molecular mobility at lower frequencies and thereby promotes the interdiffusion of latex particles to create a skin layer.In turn, the skin layer is a barrier that prevents the exudation of surfactant to the surface. The TR probably enhances the coalescence of the latex particles by

The first atomic force microscopy (AFM) images of waterborne acrylic pressure-sensitive adhesives (PSAs) are presented along with details of their optimum scanning conditions. Driving this work is a huge practical need for information about the surface morphology of waterborne PSAs, which are deposited from colloidal dispersions to yield highly tacky, soft surfaces. These surfaces present contradictory requirements for tapping-mode AFM. Whereas soft surfaces require light tapping to avoid surface damage, tacky surfaces require energetic tapping to enable the tip to lift off of the surface. We have made a systematic study of the effects of several key parameters:  the cantilever spring constant; the free amplitude of oscillation (A o); the setpoint value (d sp); and the setpoint ratio (r sp = d sp/Ao), which we have re-defined for a soft surface to account for the indentation depth. Amplitude−distance curves were obtained from the PSA surfaces to evaluate the tip's indentation depth. Reliable images are obtained when these parameters are known and optimized. While the “true” surface of the film is actually rather smooth, images of the sub-surface particle morphology are best obtained with a stiff cantilever (spring constant of 48 N/m) and a large A o (about 135 nm). Setting r sp close to unity minimizes the indentation of the tip and the resultant surface deformation.

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The length scales of film thickness non-uniformities, commonly observed in polymer colloid (i.e. latex) films, are predicted. This prediction is achieved by investigating the stability behaviour of drying latex films. A linear stability analysis is performed on a base solution representing a uniformly drying latex film containing a surfactant. The analysis identifies film thickness non-uniformities over two length scales: long (millimetre) range (from lubrication theory) and short (micrometer) range (from nonlubrication theory). Evaporation and surfactant desorption into the bulk film are identified as the primary destabilizing mechanisms during drying. Experimental evidence through direct visualization and atomic force microscopy confirm the existence of non-uniformities over both length scales, which are shown to be functions of parameters such as initial particle volume fraction, surfactant amount and desorption strength, whilst being independent of drying rate.Published in JAIChE 54 (2008) 3092-3105

The AROME–NWC nowcasting system has been developed in order to cover the nowcasting 0–6 h range. It is based on the existing AROME mesoscale model, from which the lateral boundary conditions and the first‐guess file are taken. The difference between those two systems is basically the observation window length and a very short cut‐off time. Studies have been carried out to show that in practice it is not necessary to compute a set of background‐error statistics matrices as a function of the forecast lead time of the first‐guess file. The spin‐up of the system has been proven to be small and the 15 min cut‐off to be long enough to keep a good forecast quality. This nowcasting system has been validated against the operational mesoscale model AROME: it has been shown that it performs better for nowcasting ranges as regards temperature, humidity and wind, due to its use of more recent observations. The precipitation forecasts are less satisfactory, with some improvement during the day and some degradation at night.