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About Biopol®

BIOPOL® Polymers are water soluble crosslinked Polyacrylic Acid. It is offered as fluffy dry white powder.

BIOPOL® polymers have been used for over 50 years for various applications with the highest quality carbomers on the market. Their application in products as rheology modifiers, tablet binders, suspension stabilizers, thickeners, extended release polymers, mucoadhesive aids, bioavailability enhancers have increased their demand as they are versatile and their ease of use has created its demand in Pharmaceutical, Nutraceutical, Personal Care & Allied Industrial applications. Grades within the BIOPOL® family are chemically similar in terms of the fact that they are all high molecular weight, crosslinked polyacrylic acid polymers. However, these gel forming polymers differ by their chemical crosslinking and can be grouped
into 3 categories.

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3 Categories of Polymers

Carbomer Homopolymers

Acrylic acid crosslinked with allyl sucrose or allyl pentaerythritol.

Carbomer Copolymers

Acrylic acid and C10-C30 alkyl acrylate crosslinked with allyl pentaerythritol.

Carbomer Interpolymers

Carbomer homopolymer or copolymer that contains a block copolymer of polyethylene glycol and a long chain alkyl acid ester.

Our passion & mission to enhance our product performance & quality over time has helped us address the regulatory demands, increase product robustness & flexibility and improve product handling, especially during mixing/processing and increase the ease of polymer dispersion to cut down on processing time. Our entire range of BIOPOL® carbomer family are synthesized without Benzene - a substance that is increasingly restricted for use in pharmaceutical excipient applications as well as is harmful for topical applications on repeated use. Our entire range of carbomers are synthesized in Methylene Chloride only within the range of Pharmacopoeia & maintaining it much below the maximum allowed limit for higher safety levels.

Structure of BIOPOL®

BIOPOL® is manufactured via suspension polymerization. The polymeric powder is separated from the polymerization medium, purified and dried to the required specifications.

Each particle (about 0.2 micron in diameter with an average agglomerate size of 2-7 microns) is a network structure of polymer chains chemically connected by crosslinks (shown in figure 1).

When in contact with water, hydration starts to uncoil the polymer network of BIOPOL®. This results in an increase in viscosity of the aqueous dispersion (BIOPOL® polymer is not soluble in water but becomes swollen in water). To achieve full viscosity, it is necessary to complete the uncoiling of the polymer chain network. Complete uncoiling is achieved by neutralizing the carboxylic acid groups with a base (an alkali or amine); the resulting anionic charge on the polymer chain creates repulsive forces that rapidly uncoil the network to an extended structure, therefore attaining maximum thickening efficiency (Figure 2).

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As described above, the viscosity of BIOPOL® in water (for example) will increase upon neutralization with a base (such as sodium hydroxide/Tri-ethanolamine). With variation in pH, the viscosity of the aqueous dispersion decreases drastically. This effect is due to the presence of excessive ions. Therefore, care must be taken to avoid overshooting the pH in order to maintain the maximum thickening efficiency.

The neutralized version of BIOPOL® (in form of a salt) is in fact a polyelectrolyte. Therefore, the viscosity of its aqueous dispersion will be susceptible to the presence of electrolytes (e.g. an inorganic salt). The viscosity drops more dramatically for di-valent ions. (e.g. calcium chloride) than mono- valent ions (e.g. sodium chloride). Solid precipitation can also occur with of di-valent ions. In Industrial practice, the use of a slight excess of BIOPOL® or a chelating agent such as EDTA, or both can overcome the presence of inorganic salts to maintain the rheology & thickening efficiency.
Thickening efficiency increases with increasing concentrations of BIOPOL® at specific pH7 . Generally, the viscosity of aqueous dispersions will experience a slight reduction at high temperatures (e.g. 60-70°C).
Aqueous dispersion of BIOPOL® exhibits pseudo plastic behaviour (i.e. the dispersion has a high apparent viscosity at rest but low viscosity under shear stress). Under normal conditions, the dispersion reverts back to its apparent high viscosity when the shear force is removed. This unique rheological property of BIOPOL® provides many benefits for various applications such as cling when applied to a vertical surface and non-splashing when poured out from a container. The yield value and the viscosity of aqueous dispersions are the two important factors for providing stability for an emulsion and stability of suspending solid insoluble particles in a medium.

SELECTION OF A NEUTRALIZING AGENT

There are many types of bases (i.e. neutralizing agents) available commercially. Hydroxides of sodium, potassium and ammonium are the most common inorganic bases for use in an aqueous system. For hydroalcoholic systems, the choice of a neutralizing agent depends on the hydrophilicity of the medium to be thickened (i.e. hydrophilicity decreases with increasing the amount of alcohol in the medium). The hydrophilicity of the neutralizing agent chosen will decrease with increasing amount of alcohol in the medium.

The same principle holds for thickening organic solvents; an organic amine is recommended. BIOPOL® can be used to thicken a variety of polyhydroxy solvents (such as diols, triols and polyols) without a neutralizing agent since the thickening mechanism is hydrogen bonding. In many cases, the use of dual neutralizing agents (inorganic and organic) can be useful for an emulsion system.

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