Heat capacity of liquids : critical review and recommended values

Dispersions of nanofillers into aqueous and solid biopolymeric matrices were studied from the physicochemical viewpoint. This work was carried out based on the idea that the combination of biopolymers, derived from renewable resources, and nanofiller, environmentally friendly, may form a new generation of nanomaterials with excellent and unique properties at low cost. To this purpose, two pectins with different degrees of methyl esterification and nanoclays like halloysite and laponite RD were selected. The thermodynamic and structural studies on the aqueous mixtures of pectin and nanoclay were able to discriminate the interactions, which control the adsorption of pectin onto the filler and the aggregation of both pectin and clay particles. The gained insights were useful to interpret the mesoscopic structure of the nanocomposites (prepared from the aqueous mixtures by means of the casting method) evidenced by SEM, thermal stability, tensile properties, and transparency investigations. The attained knowledge represents a basic point for designing new hybrid nanostructures in both the aqueous and the solid phase for specific purposes.

Dispersions of Nanoclays of Different Shapes into Aqueous and Solid Biopolymeric Matrices. Extended Physicochemical Study

This study focused on the preparation and characterization of films based on biopolymers (hydroxypropylcellulose and low methoxyl pectin) and halloysite nanotubes (HNTs). The morphology is strongly dependent on the polymer nature. In particular, we observed a sandwich-like structure composed of two hydroxypropylcellulose layers incorporating the HNTs and a homogeneous distribution of the nanotubes into the low methoxyl pectin matrix. The different mesoscopic properties were invoked to explain the dielectric, thermal, and wettability properties of the corresponding films. Nanocomposites obtained by combining materials from renewable resources and HNTs is a challenging task in view of designing green materials with tunable barrier and delivery properties for specific purposes.

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Films of Halloysite Nanotubes Sandwiched between Two Layers of Biopolymer: From the Morphology to the Dielectric, Thermal, Transparency, and Wettability Properties

A study was carried out in which new experimental data on heat capacities of pure liquid organic and some inorganic compounds were compiled, critically evaluated, and recommended values provided. Compounds included in the compilation have a melting point below 573 K. The bulk of the compiled data covers data published in the primary literature between 1993 and 1999 and some data of 2000. However, some data from older sources were also included. The data were taken from almost 1030 literature references. Parameters of correlating equations for temperature dependence of heat capacities of liquids were developed. This paper is an update of a two volume monograph entitled Heat Capacity of Liquids: Critical Review and Recommended Values (96ZAB/RUZ) that was published in 1996 in the Journal of Physical and Chemical Reference Data as Monograph No. 6 and was the product of the IUPAC Project No. 121/11/87.

Heat Capacity of Liquids: Critical Review and Recommended Values. Supplement II

We present here the first results of a systematic study of the dielectric properties of alcohols–water solutions. The complex dielectric constant e=e′−ie′′ and the dielectric relaxation time τ of MeOH, EtOH, 2‐PrOH alcohols, and their aqueous solutions are reported for some values of the water mole fraction xw in the range 0≤xw≤0.5, at various temperatures (from 30 °C down to −43 °C for MeOH and its solutions). τ has been measured by a two coaxial resonators spectrometer in a significant frequency range for the principal relaxation region of these liquids (0.47–4 GHz). Measurements of e′ at 13 MHz with a different experimental apparatus have also been made. Our data do not confirm previous determinations of τ vs xw at 30 °C. In all the investigated temperature range, τ is a decreasing monotone function of xw for the aqueous solutions of EtOH and 2‐PrOH. On the contrary, the dielectric relaxation time of MeOH aqueous solution is practically constant up to xw=0.1 at 30 °C; at 0° and −25 °C, τ increases at ...

The dielectric properties of alcohols–water solutions. I. The alcohol rich region

Dielectric constants (measured at 1 MHz) are reported for solutions of water (concentration range 0 to 0.2 mole fraction) in 1-propanol at 25°C, and in 1-butanol, 1-pentanol, and 1-hexanol at 15, 25, 35, and 45°C. These results, together with literature values for solutions of water in methanol, ethanol, 1-heptanol, and 1-octanol, show that water interacts with alcohols in at least two ways: (1) it can participate in the formation of dynamic hydrogen-bonded chains, thereby raising the polarizability; (2) it can form relatively stable structures such as H2O(ROH)4 which have zero net dipole moment and consequently diminish volume polarizability. For C
 n
 H
 2n+1
 OH alcohols,n≥4, most of the initially added water forms complexes: consequently, addition of water to these alcohols lowers the dielectric constant.

The static dielectric constant of solutions of water inn-alcohols at 15, 25, 35, and 45°C

Static dielectric constants, viscosities, densitites and refractive indices of 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-methyl-2-butanol were measured at 15, 25, 35 and 45°C. These results together with the previous data on n-pentanol have been analyzed in terms of the Kirkwood correlation factor g
 k
 and of the energy of activiation for viscous flow. With the exception of 2-methyl-2-butanol, g
 k
 was found to be greater than unity. These results show that the monomeric units of isomeric pentanols interact by means of hydrogen bonding to form dynamic structures essentially of two types: linear chains where co-association raises the total polarizability and cyclic dimers with nearly zero net dipole moment. Energies of activation for viscous flow as well as Kirkwood correlation factors correlate with the molecular parameters (i.e. position of OH group in the molecules, steric hindrance of alkyl chain etc.) of the alcohols. The implication of these parameters on the molecular association of the isomeric pentanols are discussed.

Static dielectric constant, viscosity, and structure of pure isomeric pentanols

The effects of cold HMDSO and HMDSO + SF6 plasma treatments on spruce, chestnut and poplar wood were investigated in order to obtain a hydrophobic surface evaluated by microscopic, spectroscopic (FT-IR and LIBS) and contact angle analyses. Cold plasma treatments can increase the surface hydro-repellence without modifying the external aspect and bulk properties of different woods.

Wood coated with plasma-polymer for water repellence

Moisture absorption, thermal conductivity and noise mitigation of clay based plasters: The influence of mineralogical and textural characteristics

Waterlogged archaeological woods (Pinus pinaster, Ulmus cf. minor and Fagus sylvatica L.) were consolidated by using Colophony, Rosin 100, and a mixture of Poly(ethylene) glycol (PEG) 3000 and Poly(propylene) glycol (PPG) 425. The efficiency of the consolidants was estimated by determining the content entrapped into the cavity of degraded wood. For this purpose, thermogravimetry was demonstrated to be a reliable tool. In the case that the polymeric mixture was used for impregnation, it was also possible to discriminate the amount of PEG 3000 from that of PPG 425 captured by the wood capillaries. Regardless of the wood nature, all the consolidants were present in treated samples in large amount (at least 70% w/w). Thermogravimetric results were in agreement with those calculated by using the wood degradation degree and composition of the consolidant mixture. One of the advantages of using this technique consists into requiring very small amounts (a few mg) of sample against the grams necessary for the conventional experiments.

Dorina Ines Donato

Papers

The static dielectric constant of solutions of water inn-alcohols at 15, 25, 35, and 45°C

Static dielectric constant, viscosity, and structure of pure isomeric pentanols

Wood coated with plasma-polymer for water repellence

Moisture absorption, thermal conductivity and noise mitigation of clay based plasters: The influence of mineralogical and textural characteristics

Thermogravimetric analysis: A tool to evaluate the ability of mixtures in consolidating waterlogged archaeological woods