Expancel microspheres are small spherical particles made of plastic. Microspheres consist of capsules with a gas encapsulated in them. When heated, the gas pressure increases, the thermoplastic capsule softens - resulting in a significant increase in the volume of the microspheres.
Grades of polymer microspheres available DU - Dry unexpanded - used for materials where elevated temperatures (from 90 to 235°C) are used in processing. They are used as a physical foaming agent, mainly in thermoplastics. DET - Dry expanded treated microspheres. Pre-expanded microspheres act as a lightweight filler and are used in processes where no or insufficient heat is generated or, for example, where the matrix is cured at a temperature below the expansion temperature of the microspheres. MB - dry granular non-expanded microspheres containing 65% dry non-expanded microspheres (DU) and 35% EVA. Granular microspheres are dust-free, easy to dispense, especially if the basic composition is also in granules, so MBs are particularly sought after in the production of thermoplastic products as a physical foaming agent, just like DU grades. WU - Wet, unexpanded microspheres. Wet microspheres are used for production processes using water and at production temperatures of 90-235°C. This grade was developed to create 3D printing on fabrics, wallpaper, paper, etc. WET - wet, expanded microspheres. WET microspheres are quite easily incorporated into a water dispersion. This brand is in demand in thermal insulation, water dispersion, water emulsion paints as a lightweight filler when the process does not involve heat generation or heating to temperatures sufficient for microsphere expansion. Elasticity All Expancel grades are highly elastic. Expanded microspheres are easily compressed. When pressure is reduced, the microspheres regain their original volume. Due to their rapid recovery, Expancel microspheres can withstand several thousand compression-expansion cycles without collapsing. This is very important when using the microspheres in impact absorbing materials, as well as when pumping the microspheres, alone or in various mixtures. Thermo - mechanical Characteristics The Expancel product range includes grades with expansion temperatures ranging from 80-190°C. The different thermo - mechanical behaviour of the various Expancel grades allows the selection of the optimum grade for each specific process or application. Expancel microspheres can be stored for long periods of time and retain their properties, but exposure to excessively high temperatures is undesirable.
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TMA curves for some EXPANCEL grades Particle size Expancel microspheres have different particle sizes depending on the intended use. Expanded microspheres range in size from 20 to 150 µm Foaming agent Expancel WU and DU non-expanded microspheres are used as a foaming agent. When heated, the volume of the microspheres increases 30-50 times. In printing inks, this property is used to print stencils and engravings to produce a three-dimensional texture on paper, wallpaper and fabric. In thermoplastics, Expancel microspheres provide a controlled and predictable foaming process during extrusion or injection moulding. The foam structure is 100 per cent closed cell and the cell size is approximately 100 microns. Microspheres are also used in underbody protection materials and sealants for the automotive industry, paper and board manufacturing, coatings, and processing of woven and nonwoven materials. Filler for density reduction Expancel WE and DE expanded microspheres have a density of less than 30kg/m³. This ultra-low density combined with elasticity makes Expancel microspheres an outstanding material compared to other lightweight fillers where not only density reduction but also improved material properties are required. In artificial marble, a small amount of Expancel microspheres (1.5% by weight) reduces product weight while reducing the likelihood of cracking and maintenance costs. Adding 1% wt. of microspheres to polyester putty reduces the density of the putty from 1800 kg/m³ to 1100 kg/ m³. The sandability of the putty is also improved. Other applications where density reduction is achieved by the introduction of Expancel microspheres include injection moulded polyurethanes, paints, acrylic putties and joint fillers.
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Improving Characteristics Expancel microspheres can enhance the properties of both materials and products in a variety of ways, giving them additional benefits. When nonexpanded microspheres are added to thermosetting compounds prior to curing, surface defects, bubbles and other cavities are reduced. Due to the expansion of the microspheres during the curing process, internal pressure is generated and thus the aforementioned surface properties are achieved. In polyester putties, the presence of Expancel pre-expanded microspheres results in a variety of formulations having a consistency ranging from sour cream to butter, facilitating their application. The sandability of polyurethane block modelling materials is improved when the material contains microspheres. Adding small amounts of Expancel microspheres to faux marble makes it a more resilient material, so it can withstand heating and cooling cycles longer.