Biocides, Fungicides and Algaecides Update

Kerry Pianoforte of Coating Worlds wrote:

Biocides are a critical component in paint formulations. Although biocides represent a relatively small percentage of the overall formulation, without the right biocide mix, microbes can compromise product performance, functionality and general aesthetics of the coating.

"Biocides can help alleviate the threat of microbes by protecting products throughout the life cycle, from manufacturing and storage to the actual application of the product," said Ken Littel, Dow Biocides global marketing manager for materials protection.

One of the main drivers for biocides, fungicides and algaecides continues to be the ever increasing demand for waterborne coatings....CLICK HERE TO READ to read the whole article in JW Latex Consultancy Book 2.

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Pigments Suppliers Directory - JW Latex Consultancy Book 2

Please Click Here For The "PIGMENTS SUPPLIERS DIRECTORY"

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Dunlop and Talalay Latex Foam

Student: In the manufacturing of latex foam products such as the mattresses, what are the main differences between the so called Dunlop process and the Talalay process? What gelling mechanism is involved in each case?

JohnWoon: Very briefly, in the Dunlop process, the gelling system is done in a one-stage operation. For gelling, zinc oxide and sodium silicofluoride (SSF) are used. The compounded latex (with curatives, soap etc) is first frothed mechanically before the addition of the gelling agents (i.e zinc oxide and SSF) followed by moulding.

SSF would undergo hydrolysis resulting in a drop in the latex pH due to the formation of hydrofluoric acid. This, coupled with the formation of zinc ammines, would lead to the gelling of the latex in the foam.

In the case of the Talalay process, a measured quantity of slightly foamed latex is poured into the mould to only partially fill it. After the mould has been closed, the latex is expanded by vacuum to completely fill the mould. The foamed latex is prevented from collapsing by rapidly dropping the temperature to -30°C and freezing it solid.

At this point, carbon dioxide gas is passed through the latex leading to a drop in pH and hence gelling. The temperature is then increased to 115°C to set and vulcanise the latex.

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Permeation and degradation of gloves by chemicals

Consumer: Can you explain briefly the meaning of "permeation" and "degradation" when one talks about chemical resistance of gloves.

JohnWoon: Permeation is the penetration of a substance or chemical (i.e. the permeate) through a solid (e.g. film or sheet) through the following processes:

1) Sorption (at the interface): meaning chemicals are adsorbed at the surface of the film.

2) Diffusion (through the solid): meaning the "permeate" (i.e. the chemical) penetrates the film through molecular gaps and pores.

3) Desorption: The chemical leaves the solid at the other side of the film (as a gas if it is volatile). For glove testing, this is known as "breakthrough" and the time taken for this to take place is termed "breakthrough time".

The "degradation" of gloves after exposure to the chemicals refers to the loss of physical properties such as modulus and tensile strength.

For more in depth description of such test, please CLICK HERE.

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K 2007 FAIR

The K 2007 fair to be held on 24-31 October in Düsseldorf, Germany has a huge variety of exhibitors that supply technology, materials and services for the many different polymer processes. To Get Details Please Click here

Not really sure about the difference between "thermoplastics" and "thermosets"?

The prestigious Nobel Prize organisation has launched an online game in their website in its educational section. The objective is to inform school students about plastics.
The game is called "Heating Plastics" and is designed to educate children aged 14 years and older about plastics, including how they are made and what happens when they are heated. If you don't already know the difference between thermoplastics and thermosets, please click HERE to join your children and play this game.

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Unjustifiable banning of latex gloves in restaurants?

Consumer: I've been diagnosed to be suffering from latex allergic problems through years' of using latex gloves and have had quite a bad experience in some restaurants where latex gloves were used in handling food. I was therefore very pleased that a few states in the USA have banned the use of latex gloves in restaurants. What is your comment?

JohnWoon: First of all, my sympathy is with you for having unfortunately developed the latex allergy problem. We should however understand the reasons why the use of gloves in the food industry was first initiated in the first place.

I understand that thousands of deaths have been repeatedly reported in the United States every year due to food-borne infections. To control this problem, The FDA had introduced the Food Code that provided guidelines to retail outlets such as restaurants and grocery stores on how to prevent food borne illness and the use of gloves is one of them. For barrier property, one generally has the choice of either gloves made from the superior natural rubber latex or the inferior PVC or polyethylene.

Yes, we know that a few states in the USA have banned the use of latex gloves in restaurants but to the best of my knowledge, this decision was made despite the FDA’s advice that there was no scientific and medical verification that the reported cases of allergy episodes in restaurants were directly linked to the natural rubber latex gloves used. FDA also cited the possibility of the sensitized persons having consumed foods in the restaurants that cross reacted to latex protein. Such foods include kiwi, bananas, potatoes, tomatoes, sweet pepper, chestnuts, spinach, buckwheat, stone fruits, etc.

My advice to you is that you should now be aware of the danger of the restaurants’ switching to the use of PVC and Polythene gloves which have been proven to have a very much inferior barrier property compared to latex gloves. Further more, the plasticizers used in PVC gloves which could leach out easily from gloves have been reported to be toxic to the liver, kidney, heart, and reproductive system.

I would like to stress that latex gloves made today especially those with the SMG (Standard Malaysian Gloves) certification have a protein and powder content at levels so low that the gloves would no longer induce easily further sensitization to those donning latex gloves.

If you were to go back to and use the same restaurants (who are now no longer using latex gloves) where you've experienced the allergy reaction earlier, chances are that you might still have the same allergy reaction!

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