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Towards the end of 2001, Bio-Lab received reports of discoloured Polysheen Plus from several dealers and consumers. Product ranged in colour from almost clear to a bluish-grey and sediment was observed at the bottom of all of the bottles concerned. An investigation showed that the blue dyestuff used to colour the product was settling out of solution and no amount of agitation would get the dye to redissolve. In a somewhat perverse way, this "self-clarification" bore testament to the clarifying ability of Polysheen Plus. The solution to the problem was straightforward. Bio-Lab assessed a number of blue dyes and selected one that showed excellent long-term stability in high concentrations of clarifier. To further ensure quality, a series of filtration steps were introduced for both the raw materials and the final product. Since replacement of the dye, there have been no further reports of discolouration, even on batches of product over 18 months old.

A second, more complex issue arose during 2002. Several reports were received detailing the appearance of a white contaminant in bottles of Polysheen Plus. Descriptions ranged from fibrous material all the way through to discrete lumps. The conclusion reached by most respondents was that the contaminant was a mould or fungal growth. However, investigations carried out at Bio-Lab revealed that this was not the case. The solid material was actually a plastic - to be specific, a cross-linked polymer. For readers seeking further technical information on this term, please see the section headed Introduction to Polymerisation, below.

The cross-linking reaction that occurred in Polysheen Plus was initiated by traces of acrylamide monomer present in one of the principal polymeric ingredients. According to the raw material's manufacturer, this unreacted monomer is encapsulated in the polymer at the time of production - such regions are often referred to as "hot spots". The monomer remains in the granulated raw material until released when the material is dissolved - an essential step in the production of Polysheen Plus. Unfortunately, cross-linking does not necessarily take place immediately. Indeed, some batches of Polysheen Plus sat three months before any sign of the white contaminant was evident. Filtration pre- and immediately post-production did not prevent the material forming, although filtering after the cross-linked polymer came out of solution did not result in further contamination.

A similar reaction has been observed in clarifiers used in the paper manufacturing industry.

In order to prevent the formation of this cross-linked polymer, new sources of raw material were tested and appropriate changes made in February 2003. As a precaution, all batches manufactured from that month onwards have been, and will continue to be, stored in intermediate bulk containers (IBCs) for 3 months prior to bottling to ensure any traces of contaminant, if present, are removed by filtration. It must be stressed that the two quality issues described herein have no effect whatsoever upon the performance of Polysheen Plus. Field tests revealed that the white cross-linked contaminant dispersed in pool water, leaving no residue on surfaces or in filters.

Introduction to Polymerisation

Polysheen Plus is composed of a proprietary blend of water-soluble polymers. Polymers are long chains of atoms held together by covalent bonds. All plastics and rubbers are classed as polymers. They are produced in a process termed polymerisation, in which the "building blocks" - molecules referred to as monomers - are reacted to form linear chains or, in some cases, three-dimensional networks. Using poly(ethylene) as an example, an appropriate acid (A) reacts with an ethylene monomer to form a reactive intermediate:

 

Basically, then, polymers are chains of repeating monomer units. A few examples of monomers and the resultant polymers are given in the table below. The list includes the first man-made polymer, polystyrene, which was synthesized in 1839.(1)


With many polymers, it is possible to react certain atoms in the linear chains with specific compounds (sometimes the monomer itself) to form "bridges" between successive chains. This process, known as cross-linking, gives rise to a three-dimensional network often exhibiting great strength and rigidity. Examples of useful cross-linked polymers include the hard-wearing alkyd resins used extensively in automotive paint finishes.

Reference
1. B. Selinger, "Chemistry in the Marketplace", 4th edition, Harcourt Brace Jovanovich Publishers, Sydney 1989, p. 193.

The above information is supplied by Bio-Lab and represents its best interpretation of available technical information at the time of preparation. The sole purpose is to supply factual information to Bio-Lab customers. It is not to be taken out of context nor used as support for any other claim not made herein.