Vitreousness is an important quality characteristic that affects the yield of semolina during milling of durum wheat. It has been observed that kernel vitreousness seems to be lower when durum is exposed to damp conditions just before harvest. The main objective of this research was to determine the effect of high relative humidity (RH) on kernel vitreousness of ten durum wheat cultivars. Spikes were exposed to 88% RH at room temperature for 1 and 3 days. This resulted in increased spike moisture, kernel moisture and kernel size. Vitreous kernel content (vitreousness) decreased 23.6% after spikes were exposed to high relative humidity for 3 days. Exposure to 88% RH caused the greatest decline in vitreousness with the cultivar ‘Ben’.
A description is given of modifications to a dynamic mechanical analyser (DMA) to allow controlled relative humidity (RH) experiments to be performed under isothermal or thermal scanning conditions. Free film samples of polyester melamine paints
(under-cured, normal-cured and over-cured) were supplied and the viscoelastic properties measured in the tensile mode of the
DMA. A reduction in the glass transition temperature (Tg) of up to 10C was found as the controlled RH was increased.
Authors:B. Ormsby, G. Foster, T. Learner, S. Ritchie, and M. Schilling
Issues encountered with dynamic mechanical analysis of artists’ acrylic emulsion paint films are presented alongside modifications
to improve controlled relative humidity (RH) experiments using isothermal and thermal scanning conditions. Free films of titanium
white (PW6) artists’ acrylic emulsion paints were cast as free films and their viscoelastic properties measured using the
tensile mode of the dynamic mechanical analyser (DMA). Artists’ acrylic emulsion paints are within their glass transition
temperature region at room temperature and are highly responsive to changes in ambient temperature and relative humidity,
hence controlling relative humidity during analysis is vital to the successful analysis of these paints.
Authors:B. Ormsby, G. Foster, T. Learner, S. Ritchie, and M. Schilling
After improvements were made to a modified Polymer Labs MkIII DMTA instrument to facilitate repeatable controlled humidity
(RH) experiments using isothermal and thermal scanning conditions, the viscoelastic properties of titanium white pigmented
artists’ acrylic emulsion films were measured in tensile mode. The effects of temperature, relative humidity and accelerated
ageing regimes on two brands of titanium white paints were explored. These paints are highly responsive to changes in temperature
and relative humidity, formulation differences affect properties slightly, and while light ageing had a negligible effect,
thermal ageing resulted in decreased storage modulus and increased film density.
All building materials can be affected by microbiological agents during their lifecycle. The presence of microorganisms changes the appearance of the surface, degrading it, and they can even cause health problems to the residents. The biological susceptibility is dependent on the content of nutrient based on organic compounds. Thus one of the most susceptible of those materials are earthen construction materials. The degree of fungal growth is influenced by the chemical composition and plant fibres additives as well as the external conditions such as temperature and relative humidity.
The earth plastering mortar has started to gain more attention recently as it is considered to have a low environmental impact and to increase the indoor air quality. Mechanical and physical characteristics of earth materials were studied by a number of authors but the knowledge about the biological resistance of the material is scarce.
This study intends to look into the issue of the biological colonisation of earth plasters depending on the relative humidity. The samples, made of four types of earth plasters with different plant fibres, were placed to an environment of the relative humidity ranging from 33% to 100%. During a period of 4 weeks the extent of fungal growth was observed.
Growth of mould fungi is one of the main causes of deterioration of foodstuffs, building materials and textiles. A new microcalorimetric
technique has been developed for the study of mould activity as a function of water activity, temperature and atmospheric
composition. This paper describes the method, in particular how to measure mould activity as a function of relative humidity.
An understanding of the mechanisms by which water molecules are held within a substance or at its surface, either by physical
or chemical processes, is of importance in the formulation, preparation and storage of a wide variety of substances. The traditional
experimental techniques which have been used to make measurements on samples exposed to specific levels of relative humidity,
(e.g. using desiccators containing saturated salt solutions), are slow, laborious, inaccurate, and provide a limited amount
of data. This paper describes the conception, operation, and facilities of a new system which by employing recently developed
electronic components and transducers, significantly advances the performance capability for moisture sorption analysis.
Authors:Z. Ali, D. James, W. O'Hare, F. Rowell, and S. Scott
The effect of different relative humidity (RH) on the response of a six-polymer coated Quartz Crystal Microbalance (QCM) sensor based electronic nose (EN) was investigated, RH 30 and 50% respectively. Increases in the sensor responses were observed for an increase in RH. A stainless steel pre-concentration tube (PCT) containing Porapak-S and a nichrome heating element was developed to minimise the effect and allow for chromatographic pre-separation. Breakthrough times of chemical compounds through the PCT were experimentally determined and used to select a mixture of water and toluene as a suitable sample for pre-separation. The PCT was capable of separating the water from the toluene and the EN was competent at evaluating the concentration of toluene in the solution.
Seed moisture content is a well-recognised index of safe storage. However, when in equilibrium with the storage environment it is merely an indicator of the relative humidity of the air, which is the primary regulator of the growth of moulds and insects. The relationship is influenced by the profile of the seed components. During the 1990s, significant increases in the seed oil content of evening primrose were achieved through plant breeding. This paper shows that the equilibrium moisture content of evening primrose seeds declines significantly with increasing oil content. Hence, the moisture isotherm is altered and newer cultivars must be stored at slightly lower seed moisture contents to ensure that seed and oil quality are maintained.
Authors:A. Foppoli, L. Zema, A. Maroni, M. Sangalli, M. Caira, and A. Gazzaniga
saturated aqueous solutions of CH 3 COOK, NaI (samples of TAA·H 2 O), NaBr, KBr, KNO 3 and K 2 SO 4 (samples of TAA) in order to produce relativehumidity values of 0, 22, 38, 58, 81, 94 and 97, respectively [ 5 ]. The control of relativehumidity was