Cenospheres

Hollow Ceramic Microspheres

Also known as Hollow Ceramic Microspheres and trade names like Cenolite, Spherelite and Litefill etc. Standard Grades

Introduction:-

Cenospheres is a glass hard, inert, hollow silicate sphere. Cenospheres is primarily used to reduce the weight of plastics, rubbers, resins, cement, etc., but also imparts further benefits in many situations. Many of the advantages from the use of Cenospheres, including increased filler loading and improved rheology, are directly attributed to the spherical nature of the material. Characteristics · Lightweight · Free-flowing · Off-White in Colour · Spherical · Inert Typical Applications Refractories, PVC flooring, Oilwell cements, brake linings, Phenolics, Epoxies, Cast Polyesters, synthetic marbles, syntactic foams, BMC, SMC and FRP. Low-density cements, shotcrete and gypsum board joint compounds. Automotive sound-dampening sheets. Advantages Reduced weight, increased filler loadings, better flow characteristics, less shrinkage and warping. Improved physical properties in moldings, castings and laminates, reduced water absorption, improved flame retardance, improved chemical resistance.

Advantages of Cenospheres

Spherical Shape:-

The sphere is natures most efficient shape with the lowest surface area compared to volume. It is this shape which gives cenospheres such a wide variety of uses other than simply being used as a lightweight filler. The spherical shape means that it takes less resin, binder, water etc to wet out the surface of cenosphere than any other shaped filler. This results in low resin or binder demand which in turn allows high solids formulations, lower shrinkage and often lower cost. Spherical fillers exhibit excellent flow and are easy to spray, pump, trowel etc. Cenospheres are therefore used to considerably improve workability and ease of use in a wide variety of applications. Spherical fillers also reduce shrinkage not only because they allow lower binder contents but directly as a result of their shape. At high concentrations, the spheres are packed together but find it difficult to get closer together in the way that irregular shaped fillers can during shrinkage of the binder, evaporation of solvent or water. Spheres therefore help maintain the volume of the original product and as such are excellent fillers for crack and joint compounds, sealants etc.

Lightweight:-

The advantages of low density are in many cases quite obvious and clear. The automotive, marine and aerospace industries all demand the lowest possible weight for plastic parts, sealants, putties, sound dampening etc and the addition of hollow spheres are an ideal solution. At 0.7 g/cc cenospheres are approximately 25 % of the density of other mineral fillers but are also strong enough to withstand most mixing, compounding and processing activities. The building industry is moving more and more to lightweight products. Low density results in ease of application and use, easier mixing, lower transport costs, low slump and sag, reduced worker fatigue, easier sanding, easier cutting, easier drilling and a considerably happier work force.

High Melting Point :-

Cenospheres have a high melting point of 1200 – 1600 °C, which is considerably higher than synthetic glass microspheres. They are therefore excellent for use in high temperature insulating refractories and fire resistant coatings and panels. All other possible HIGH Heat application.

Inert :-

Cenospheres are inherently alumino silicate spheres of very low reactivity. Their chemical composition makes them very resistant to acids and alkalis. They are neutral in pH and do not interfere in the chemistry or reaction of the products they are used in. The silica content is amorphous which does however make the cenospheres slightly pozzolanic and so they will over a period of months react with the free lime liberated as cement hydrates. This minor reaction is highly desirable in cement, as the presence of un reacted free lime deteriorates cementitious products.

Free Flowing :-

The free flowing nature of cenospheres means that they are easy to handle in a factory environment. They can be easily gravity fed without blockage and can be pumped in a dry form.

Insulating :-

Cenospheres have a low thermal conductivity of 0.11 Wm-1K-1. As a result they have found applications in insulating refractories, oil pipe-line insulation, geothermal cements, external wall insulation stuccos and many other applications where good thermal insulation is required.

Hard:-

With a Mohs hardness of 5 – 6, cenospheres have a hard surface that provides excellent erosion and weather resistance. The glassy shell of the cenospheres is totally impermeable to liquids and gases.

Electrical Properties:-

In lightweight insulation products, cenospheres have excellent electrical properties and are used in potting compounds, electrical encapsulation, solenoids, buss bars etc. Properties are virtually unaffected at high frequencies and while there is some loss at power frequencies, these are considerable lower that for dense silica fillers.

Low Oil Absorption:-

Cenospheres have an oil absorption of approximately 16 g oil/100 g. When it is considered that cenospheres are only 25 % of the density of most other commonly used fillers, this figure is equivalent to a level of 4 g oil/100 g. This means cenospheres have one of the lowest oil absorption levels of any available filler. This low figure is due to the spherical, low surface area shape and the glassy, smooth, totally non-porous shell of the cenospheres. Cenospheres are an ideal choice therefore when formulating to low binder level without high viscosity increase.

Good Packing Factor:-

The ratio between bulk and true density for cenospheres is small resulting in a very high packing factor of 60 – 65 %. This means that although the true density of cenospheres is only 25 % of say calcium carbonate, a 20 kg bag of cenospheres is only twice the size as a 20 kg bag of carbonate. This property is a major cost saving in terms of transport since four 20 tonne trucks of other minerals can be replaced by only one 20 tonne truck of cenospheres. Warehouse storage area and cost is also considerably reduced.