Technical Characteristics of 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 10 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

Cosmetic Applications of Injectable Polymer Microspheres

Polymer microspheres, in particular injectable polymer particles with a diameter in the range of 30−300 μm, are becoming widely used as a biomaterial in different clinical fields, such as cosmetic surgery, reconstructive surgery, and urology.  Injectable skin fillers offer many benefits in cosmetic dermatology, allowing new forms of facial rejuvenation and wrinkle treatment without surgery. Injectable skin and wrinkle fillers are used to increase tissue volume, reduce wrinkles, and improve skin’s overall contour.

According to The American Society for Aesthetic Plastic Surgery,  two formulations of fillers that are based on microsphere technology are FDA approved for use, differing in design and expected longevity of results.  These injectable microspheres products are used for volume replacement and for deep facial wrinkles (such as the nasolabial folds.) They are not approved for use in the lips.

One of cosmetic dermatology products using injectable microspheres is ArteFill® – a new breed of dermal filler that offers longer lasting results than other cosmetic filler injections. ArteFill® (known as Artecoll® outside of the United States) is made of polymethylmethacrylate (PMMA) microspheres (miniature beads) that are suspended in bovine collagen. Tiny microspheres are made of non-resorbable polymethylmethacrylate – a biocompatable compound that has been used for years.  PMMA has been used since the early 1930s in such common procedures as dental prostheses, eye lenses, bone repair, orthopedics and in pacemakers.  PMMA microspheres are well tolerated by human tissue (no rejection). Continue reading “Cosmetic Applications of Injectable Polymer Microspheres” »