Poor Water Resistance of Latex Products

Manufacturer: Some of our customers are complaining that our latex products have poor resistance to water. How could we improve this?

John Woon (Senior Latex Consultant): Rubber products made from natural rubber or synthetic rubbers are generally considered to be water resistant because of their water repelling properties especially when compared to textile materials, paper, wood and leather.

However, you must take note that all rubber products do absorb water to a certain extent. If your customers are comparing your products with your competitors' products which are made from the same rubber, you need to look at your latex formulation and the manufacturing process to minimise the levels of all water soluble hydrophilic materials. Examples are coagulant, wetting agents, fatty acid soaps, KOH and other naturally occurring water soluble non-rubbers.

I suggest you look into improving your leaching process. if you are using potassium soaps as latex stabilisers you might want to change this to ammonium soaps as thses would revert to fatty acids on drying making the rubber less water sensitive.

In order to measure the sensitivity of your product, you could immerse cut pieces of known surface areas in water at both ambient and elevated temperatures and measure the water absorbed in terms of weight per unit surface area after a given period of immersion. You could also measure the physical properties before and after water immersion.

Vietnam's rubber industry to work with regional growers to boost exports

Vietnam -- According to an article in thanhniennews.com, "The Vietnam Rubber Association plans to share information with its counterparts in China’s main rubber suppliers to prevent over-supplies and close price gaps between the exporters.

The agreement with Thailand, Indonesia and Malaysia will facilitate the exchange of information on output, demand and prices, said Tran Thi Thuy Hoa, the association’s general secretary. Vietnam’s rubber exports to China are currently cheaper than those from the three countries. While Vietnam exports rubber latex to 61 countries and territories, including the European Union and Japan, China is the main consumer of Vietnamese rubber, importing nearly 70 percent of the country’s total export volume, according to Hoa.

Of the country’s 208 rubber exporters, 165 companies trade with China, Hoa said, adding that 59 percent of Vietnam’s rubber exports to China are delivered under DAF (Delivered at Frontier) terms. The remaining volume is exported by sea or train. She said the cooperation between Vietnam and the three other rubber suppliers would support Vietnamese rubber exporters, which have been hit hard by Chinese trade barriers since March this year."

Information about Natural Rubber Latex, Glove Processing and Latex Allergens

Students: We are a group of university students and would like to know more about natural rubber latex, glove processing and latex allergens. We would appreciate any information from you.

John Woon (Senior Latex Consultant): This would entails too much of my time. I suggest you check out this website => http://bit.ly/1arR0o

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Lanxess develops new additive for rubber

Specialty chemicals group Lanxess AG has announced the development of a polymer additive for plastics and rubber that is now available for industrial application. These microgels, which consist of nanoscale organic particles, can be used to improve the material properties of elastomer and thermoplastic materials, said Lanxess.

In the course of the product's many years of development, the Lanxess Technical Rubber Products and Rhein Chemie business units have worked together closely and applied for numerous patents. These cover the processing method, the use of nanoparticles in rubber mixtures and the impact on thermoplastic and thermoset polymers.

The Technical Rubber Products business unit markets these nanoscale particles under the registered trademark Nanoprene, while Rhein Chemie Rheinau GmbH sells the additive under the brand name Micromorph. After close co-operation between Rhein Chemie company and the Japanese tire manufacturer Toyo Tire & Rubber Co. Ltd., the first major series application of the rubber additive is in the production of winter tires. These tires boast excellent dry and wet road grip, without the tire rubber hardening on contact with snow or ice.

Discolouration of Latex Dipped Products

Manufacturer: We observed discolouration of our dipped products made from natural rubber latex more than synthetic latex. Also, the colour could vary from batch to batch.

We would appreciate if you could explain why.

John Woon (Senior Latex Consultant): Natural rubber latex indeed is darker than most common synthetic latices. It is well known that natural rubber latex contains many constituents of non-rubbers. One possible cause of darkening of the dried rubber when exposed to air or oxygen is the enzymatic action of the naturally occurring polyphenol oxidase.

Another causative agent is from the Frey Wyssling particles which give the yellow colour due to the presence of carotenoids. Fortunately most of this is removed during the centrifugation process if done properly.

Since natural rubber latex is of botanical origin, the level of non-rubbers and hence its tendency to discolour is expected to vary from clones to clones and from time to time.

Efficient leaching is of utmost importance if you want to minimize the degree of discolouration. One of course must also bear in mind the possible discolouration caused by contamination with heavy metal such as copper and iron in compounded latex in which zinc dialky dithiocarbamates are used. This of course is expected to similarly occur with synthetic latex compounds using dithiocarbamates.