Clay-based heat insulator composites: Thermal and water retention properties

Applied Clay Science (Impact Factor: 2.7). 06/2007; 37:90-96. DOI: 10.1016/j.clay.2007.01.001

ABSTRACT The formulation of unsaturated polyester composite as an insulating material that gives the best in terms of thermal and water retention properties was investigated as a function of filler type and content. Different types of local fillers were used in the formulations. Bentonite-based unsaturated polyester composite which is denoted as BBUPEC was found to have stable and compatible thermal, physical, and chemical properties. BBUPEC thermal conductivity, k, values lie between 0.1 and 0.2 W/(m K). It was found that at 50 wt.% filler content and 40 wt.% polyester content, k of BBUPEC is minimum. Calcium carbonate-based composite also gave a similar value. However, in terms of citric acid impregnation, calcium carbonate-based composite was not stable and dissolution took place. In terms of water retention value, citric acid and NaOH impregnation values, one could say that bentonite-3-based composite was the best among BBUPEC. Consequently, one would say that BBUPEC shows good characteristics in terms of thermal conductivity and physical and chemical stability and with such inexpensive and abundant fillers from natural resources, they pose a potential thermal insulating material. Sandwiching of BBUPEC in wall structures by one-third of the total thickness will significantly reduce the overall heat transfer coefficient in home and industrial applications by at least 50%.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: Laboratory and field experiments were carried out, to assess the efficiency of palm-based insulators for storage water tanks under variable ambient temperatures. Palm fronds, palm leaves and their composite were used to wrap pilot water tanks and examine their thermal insulation efficiency. Four arrangements were tested including: double layer of fronds and an inner air gap, double layer of fronds separated by an intermediate air gap, palm leaves and composite of palm leaves sandwiched between two layers of fronds. The insulation efficiency was assessed in laboratory setting under heating-up and cooling-down conditions using the time constant, ${\tau}$ , and compared to a reference unwrapped tank. The insulators were also tested in the field under variable ambient air temperatures. In this case, their efficiencies were assessed considering the relative amplitude ratio of the stored water and ambient air temperatures, in addition to the phase shift between the times of temperature extremes of air and water in the different tanks. The results indicate that the fronds–leaves composite provides better insulation efficiency under heating-up, cooling-down and variable ambient air temperatures.
    ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 06/2013; 38(6). · 0.37 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, the performance of polyester (P)/glass fiber mats (G) and P/G/calcium carbonate (CaCO3) composites was compared with that of P/G/fiberglass waste composites. The residues used were conventional P/G postconsumer light resin-transfer-molding parts, obtained via knife or ball milling. Composites with up to 50 wt % reinforcement were prepared by hot compression molding and characterized via physical (density and water sorption), thermal (thermogravimetry and burnout), and mechanical (impact, Barcol hardness, and tensile) testing. The results show that the simple grinding and reincorporation of the composite residues yielded new composites with generally worse characteristics than the ones with calcium carbonate. Then, the waste was sorted by removing most of the pure resin particles from it. This yielded a resin-rich fraction, which could be better used for energy recovery and resin-covered fibers. The use of the latter as a filler yielded composites with better overall properties than those with calcium carbonate for a controlled amount of W; thus showing potential use as a replacement for the commonly used inorganic filler, maintaining the mechanical properties, decreasing the raw material cost, and reducing the amount of composite waste discarded in the environment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
    Journal of Applied Polymer Science 04/2012; 124(1). · 1.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel–Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.
    Mechanics of Composite Materials 07/2013; 49(3). · 0.45 Impact Factor

Full-text (2 Sources)

Available from
May 19, 2014

View other sources