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Polyethylene Microspheres vs Glass Microspheres - Properties, Advantages and Applications
Microspheres Overview:
Microspheres (also known as spheres, balls, beads or micro-balloons) are spherical microparticles typically ranging from 1 micron to 1000 microns in diameter. Microspheres are manufactured from a variety of raw materials. Most common types of microspheres are:
Each type of microspheres comes in different grades depending on the application and quality requirements. Quality of the microspheres ranges from monodispersed microspheres produced under very tight specifications primarily for laboratory applications to microsphere grades with huge variations in particle size and sphere uniformity for applications as fillers in automotive, transportation and other commodity markets.
Applications of Microspheres:
Traditional applications for microspheres include traffic paint, lightweight fillers for automotive and marine putties, and density modifiers for explosives. Recently microspheres have become popular in specialty applications such as adhesives, automotive and specialty coatings, cosmetics, EMI shielding, offshore products, paper, specialty sealants, plastics and composites.
Microspheres are becoming widely used in specialty applications with high-growth, high-value potential. These include digital displays, medical devices, solar panels, drug delivery, analytical technology and many other unique applications in latest science and technology development.
Polyethylene Microspheres vs Glass Microspheres:
Polyethylene microspheres (also referred to as polyethylene spheres, beads, balls, polymer spheres, polymer microspheres, polymer beads, plastic beads or plastic microspheres) are solid spherical microparticles and are the most common type of solid polymer spheres.
With advances in microsphere manufacturing processes, polymer spheres and glass microspheres are available in comparable grades, particle sizes and prices. Which microsphere material is right for your application?
There are several major differences to keep in mind when selecting microspheres:
1) Melting Point:
Polyethylene microspheres - The melting point of polyethylene microspheres varies somewhat depending on the grade and molecular weight of the polymer, but is usually between 110C for low molecular weight grades and 130C for higher molecular weight material. The melting point is typically low and sharp, since polyethylene goes through a fast phase transition. This is a very important feature for applications where the spheres are used as a temporary filler but would need to be “melted away” at a later point to create holes or cavities for a sponge effect.
Glass microspheres - The melting point of glass microspheres is from 500C - 800C, depending on the product. High melting point makes glass microspheres attractive for high temperature applications, where the product needs to withstand severe environmental or processing conditions.
2) Density:
Polyethylene microspheres - Typical densities of 0.95 g/cc - 1.2 g/cc
Glass microspheres - Solid glass microspheres have typical densities of over 2 g/cc.
Depending on the application requirements, solvents used, desired buoyancy, difference in density between polyethylene and glass microspheres might become a critical factor when selecting the right material.
3) Chemical Stability:
Polyethylene microspheres - Most grades of polyethylene have excellent chemical resistance and do not dissolve at room temperature because of their crystallinity. Polyethylene microcspheres usually can be dissolved at elevated temperatures in aromatic hydrocarbons such as toluene or xylene, or in chlorinated solvents such as trichloroethane or trichlorobenzene. This feature is benefitial if microspheres need to be dissolved at a precise point in the process.
Glass microspheres - Glass has very high chemical resistance and is the right choice for applications where microspheres need to withstand contact with agressive solvents at elevated temperatures.
4) Crush Strength:
Polyethylene Microspheres - Specific crush resistance is strongly dependent on the grade of material and processing techniques. Even though polyethylene microspheres are solid and very robust, they will crush if significant force is applied. They are not suitable for applications were microspheres undergo dramatic mechanical pressing force.
Glass Microspheres - Solid glass microspheres have the highest crush strength. Hollow glass microspheres have the lowest crush strength, which varies widely with the grade of material, density, sphere diameter, shell thickness.
If the microspheres are expected to be exposed to strong mechanical pressures such as plastic compounding or injection molding, crush strength numbers need be carefully evaluated.
5) Color (Pigments and Additives):
Polyethylene Microspheres - Pigments, additives, specialty ingredients can be incorporated into polyethylene prior to microsphere manufacturing process. This allows endless possibilities for customization of polyethylene microspheres for specific applications, smaller R&D projects, and unique customer requirements. Colored, fluorescent, charged, magnetic polyethylene microspheres are available.
Glass Microspheres - In general, it is very difficult to incorporate additives into glass. Formulating with a small percent of additives is sometimes possible, but typically additives interfere with the formation of glass and hinder its inherent properties (such as clarity, sphericity, strength, etc). Customization of microspheres with pigments and additives is limited.
In summary, even though glass and polyethylene micropsheres of comparable diameters and size distributions are available on the market, their inherent material properties make them suitable for different applications.
The defining factors become density, melting point, solvent resistance, crush strength, colors, additives and specific customization requirements. The detailed knowledge of the application, the technical judgement of scientists and engineers on the project, and sometimes simple trial and error approach must be relied on to select the right microsphere for the job.
Contact us to discuss your specific application. We will recommend microspheres that fit your needs (even if we don't manufacture them).
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