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

Solid Red Polyethylene Microspheres Announced

Santa Barbara, CA -  May 28, 2010 - Cospheric LLC is now offering a product line of solid red polyethylene microspheres in particle size ranges from 10um to 1000um (1mm).

Offering a bright red color.  These microspheres can be used as additives in personal care products, or in fluid flow visualization experiments.  Samples are in stock and ready to ship to customers for R&D use of product evaluation.  These high quality microspheres are specified to be greater than 90% spherical, and greater than 90% in the specified size range.

Sample Density is 0.98g/cc (Custom densities are available)

Spherical Particle sizes include:

10-27um, 27-32um (30 micron), 32-38um (35 micron), 38-45um (40 micron), 45-53um (50 micron), 53-63um (60 micron), 63-75um (70 micron), 75-90um (80 micron), 90-106um (0.1mm), 106-125um, 125-150um, 150-180um, 180-212um (0.2mm), 212-250um (0.25mm), 250-300um (0.3mm), 300-355um (0.35mm), 355-400um (0.4mm), 400-500um (0.5mm), 500-600um (0.6mm), 600-710um (0.7mm), 710-850um (0.8mm), 850-1000um (0.9mm).

Solid Polyethylene Microspheres for Effects in Color Cosmetics

A recent article in Cosmetics & Toiletries magazine describes the use Solid Polyethylene Mirospheres for Effects in Color Cosmetics.

Flesh Tone Microspheres - Color Matched to Skin Sample

Micropsheres have been used in cosmetics for some time, primarily as fillers and exfoliators. Most recently scientists started to utilize light reflecting properties of microspheres for creating unique optical effects, such as optical blurring and wrinkle filling.  Due to light scattering effects of the spherical surface, formulating with appropriate microspheres can minimize the appearance of fine lines and uneven skin tone, due to optically reducing contrast on the skin.

The spherical shape and smooth surface of microspheres creates a low friction ball-bearing effect that gives formulations an elegant, silky feel. This ball-bearing effect promotes better blending on the skin and a more natural finish due to the enhanced slip, glide and omnidirectional spreadability, imparting a cream to powder texture. Outstanding roundness also provides lubrication during application, which enhances the tactile experience of a cosmetic product. Continue reading “Solid Polyethylene Microspheres for Effects in Color Cosmetics” »

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” »

Exfoliating Beads: Clinical Study

Mickey McDonnell – Honeywell, United States  conducted a study about exfoliating polyethylene beads ~325um diameter.  His article was published in personal care magazine.

ABSTRACT from article:
Exfoliating beads have a long history in cosmetics, but we are unaware of previous studies on the effect of their regular use. A clinical study with 10 subjects shows that regular exfoliation leads to a reduction in the cell turnover time of the stratum corneum (SC) by about 15% (significant at the 95% level). Standard models of skin function interpret increased cell turnover time as increased desquamation. The regularly exfoliated skin also had a significantly increased uptake of dansyl chloride dye. Higher stain uptake accompanying the increase in desquamation suggests that regular exfoliation promotes addition of new cells to the SC. The study acclimatised the test panel to the exfoliant treatment for two weeks prior to the measurements to minimise the chance that results could be attributed to a shift in treatment procedures.

************ Comments  ************

The author calls the exfoliating material beads (325um).  But they are also commonly called polyethylene microspheres.

This study focuses on abrassive exfoliation with polyethylene microspheres.  Exfoliants can also work through the use of either itty bitty bits of abrasives such as crushed apricot pits, crushed almond shell, pumice, etc., or light acids like salicylic, citric, malic, etc. The means are different but the results are the same. Exfoliants remove the dead skin cells from the face that cause a clogged pore. The removal of these dead skin cells will minimize pores and open pores for cleaning. Microdermabrasion is yet another effective exfoliation method that, while it can be done at home, is generally done at salons.