Everything about Microspheres
RSS feed
  • Technical Characteristics of PMMA Microspheres

    Posted on June 15th, 2010 Microsphere Expert

    PMMA microspheres

    PMMA microspheres - Cospheric LLC

    PMMA micropsheres or polymethylmethacrylate microspheres are often referred as acrylic microspheres.  PMMA polymer is an amorphous, transparent and colorless thermoplastic that is hard and stiff. It has good abrasion and UV resistance and excellent optical clarity. It has somewhat poor solvent resistance. PMMA spheres are soluble in organic solvents such as acetone, benzene, or halogenated hydrocarbons. Though flammable, PMMA material has low smoke emission.

    Poly(methyl methacrylate) or PMMA is less hydrophobic than polystyrene and reported to show reduced nonspecific protein and peptide binding. The density of these beads, 1.19 g/cc, is considerably heavier than polystyrene particles, allowing more rapid separation and making them easier to concentrate by centrifugation. The particles typically have a hydrophilic anionic surface with refractive index of 1.48.

    PMMA micropsheres have good biocompatibility which allows the particles to be used in many medical and biochemical applications. Diameter and monodispersity specifications for the micropsheres are dictated by the requirements of each application.

    PMMA micropsheres are used in such a wide variety of industries as investigations in the colloidal crystal field, toners for copying machines, biomedical devices and injectable dermal fillers.

    Research quantities of PMMA microspheres can be obtained from several suppliers depending on the desired particle size.

    Bangs Labs offers PMMA microspheres 0.5 micron – 5 micron in diameter. Cospheric LLC sells research samples of PMMA spheres in several tight size ranges from 5 micron to 150 micron. Goodfellow offers polymethylmethacrylate spheres in two diameters of 1.5mm and 3.18mm.

    Below is some detailed technical information on material properties of PMMA:
    (source: Goodfellow)

    Electrical Properties

    Dielectric constant @1MHz     2.6
    Dielectric strength ( kV mm-1 )      15
    Dissipation factor @ 1MHz      0.014
    Surface resistivity ( Ohm/sq )      1014
    Volume resistivity ( Ohmcm )      2-14 x 1015

    Mechanical Properties

    Elongation at break ( % )      2.5-4
    Hardness – Rockwell M     92-100
    Izod impact strength ( J m-1 )      16-32
    Poisson’s ratio      0.35 – 0.4
    Tensile modulus ( GPa )      2.4-3.3
    Tensile strength ( MPa )      80

    Physical Properties

    Abbe number      57.2
    Density ( g cm-3 )      1.19
    Flammability      HB
    Limiting oxygen index ( % )      17-20
    Radiation resistance      Fair
    Refractive index      1.49
    Resistance to Ultra-violet      Good
    Water absorption – over 24 hours ( % )      0.2

    Thermal Properties

    Coefficient of thermal expansion ( x10-6 K-1 )       70-77
    Heat-deflection temperature – 0.45MPa ( C )      105
    Heat-deflection temperature – 1.8MPa ( C )     95
    Lower working temperature ( C )      -40
    Specific heat ( J K-1 kg-1 )        1400 – 1500
    Thermal conductivity @23C ( W m-1 K-1 )      0.17-0.19
    Upper working temperature ( C )      50 to 90

Comments are closed.