Advantages of Borosilicate Glass Microspheres in 0.03mm to 0.2mm sizing

BSGMS 63-75 micron at 40x magnification

High quality glass microspheres for research and development are always in high demand.  In an effort to better serve scientists Cospheric recently added a complete line of high quality borosilicate microspheres, and microbeads.

Borosilicate glass offers  advantages over standard soda lime glass microbeads.

• Roundness is >90%   (Soda lime >85%)
• Density is the lowest of most glasses at 2.2g/cc  (Soda Lime 2.5g/cc)
• Very low thermal expansion coefficient  32×10^-7/°C   (for 30-300°C)   (Soda Lime:  90×10^-7/°C)

The high roundness, and low thermal expansion make borosilicate spheres an excellent candidate for use as spacers in epoxy bond lines, or other applications which require stability over a wide temperature range.

Borosilicate glass spheres are now offered in narrow size ranges from 0.03mm to 0.2mm with greater than 90% of the particles in range.

Continue reading “Advantages of Borosilicate Glass Microspheres in 0.03mm to 0.2mm sizing” »

FDA-Approved Microspheres

What makes a microsphere FDA-approved?

In order to tell whether the microsphere can be used in cosmetics, food, or medical devices it is important to look at the raw materials that are incorporated into the microsphere during manufacturing process.  For example, unpigmented or clear polyethylene microspheres supplied by Cospheric in sizes from 10 micron to 1000 micron meet the quality requirements of the US FDA as specified in 21 CFR 172.888 and 21 CFR 178.3720.  Specific grade of polyethylene used in manufacturing of these microspheres is  FDA-approved for food applications in chewing gum base, on cheese and raw fruits and vegetables, and as a defoamer in food.

Color additives are subject to a strict system of approval under U.S. law (FD&C Act), sec. 721; 21 U.S.C. 379e. Color additive violations are a common reason for detaining imported cosmetic products offered for entry into this country. If a product contains a color additive, by law [FD&C Act, Sec. 721; 21 U.S.C. 379e; 21 CFR Parts 70 and 80] you must adhere to requirements for:

• Approval. All color additives used in cosmetics (or any other FDA-regulated product) must be approved by FDA. There must be a regulation specifically addressing a substance’s use as a color additive, specifications, and restrictions.
• Certification. In addition to approval, a number of color additives must be batch certified by FDA if they are to be used in cosmetics (or any other FDA-regulated product) marketed in the U.S.
• Identity and specifications. All color additives must meet the requirements for identity and specifications stated in the Code of Federal Regulations (CFR).
• Use and restrictions. Color additives may be used only for the intended uses stated in the regulations that pertain to them. The regulations also specify other restrictions for certain colors, such as the maximum permissible concentration in the finished product.

Continue reading “FDA-Approved Microspheres” »

Phosphorescent Microspheres – Long Afterglow Particles

Phosphorecent Beads - Yellow Green Afterglow

Phosphorescent microspheres in particle sizes 10 to 600 microns are now available from Cospheric LLC. These phosphorescent particles are 90% spherical and appear to be off-white under ordinary daylight or regular room illumination.  However, when the lights are turned off these phosphorescent particles exhibit phosphorescent yellow-green after-glow.

The spheres have tight particle size distributions and are > 90% within size range.  Polymer spheres that incorporate proprietary phosphorescent ingredient have a melting point of 115°C , and are mechanically stable past 90°C.  Phosphorescent beads are also inert in most solvents.

Intensity of Phosphorescent Afterglow:

Intensity according to DIN 67510-1

800 mcd/m² at 1 minute
180 mcd/m² at 5 minutes
90 mcd/m² at 10 minutes
12 mcd/m² at 1 hour
5 mcd/m² at 2 hours

Excitation and Phosphorescent Emission Curve:

Microspheres: Technologies and Global Markets

An extensive market research report titled Microspheres: Technologies and Global Markets was recently published by BCC Research marketing firm. The microspheres report examines the spherical microparticles used as components in many advanced materials and composites, in the healthcare and personal care industries, and in many specialty research and development applications. The report estimates the size of the microsphere industry worldwide and makes predictions on a 5-year compound annual growth rate of the microsphere market.

The global market for microspheres in 2010 is estimated to be $2 billion and growing at a 5–year compound annual growth rate (CAGR) of 11.6%, reaching global sales of $3.5 billion by 2015.

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