Vinodrai Newsletter August 2009 Vol 1

August 2009,

Vinodrai Engineers Monthly Newsletter.

Vol.: 1

Vinodrai Engineers, a name to reckon with in Rotational Moulding Technology, has been active in the field of rotational moulding for the last 16 years. The objective to make the “Rotomoulding” process easier by each passing day helped us reach at a position, where we have many delighted customers all across the globe. To keep up with the tradition of sharing knowledge, we at Vinodrai will publish a monthly newsletter. We hope rotational moulders will benefit by technical articles by prominent rotomoulders.

Why Carbon Black ? Sintex introduced water tank in India with single layer black tanks. Over a period, as per the demand and preference of customers, tank makers started offering two layer tanks with white “clean look” layer from inside. As competition started hoting up manufacturer started offering triple layered colored tanks mainly to satisfy cosmetic desire of customer. Today triple layer and double layer tanks are market standards. There is hardly any sale of single layer tank in smaller size. As tank manufacturer needs to give guarantee for tanks, it is very important for rotomoulders to know role of Carbon Black. Every material when exposed to sunlight, will partially absorb the sunlight and partially reflect the same. Absorbed portion of energy from sunlight will heat up the material. For most of the material effect of absorbing sunlight has no effect other than heating, but there are many materials which degrades and loose properties when exposed to sunlight. Most plastics will degrade when exposed to sunlight. Studies of the degradation of plastics by sunlight have shown that Ultra Violet ( UV ) content of high energy portion of sunlight is responsible for this degradation.

The absorbed UV light breaks the molecular chains of the polymer material. This leads to shorter chains, which in turn causes the plastic material to become more brittle. It leads to loss of mechanical properties and/or discoloration, cracking, fading, and chalking. UV Stabilizers : In order to protect outdoor plastic products from the UV light, the plastic needs to be shielded from these harmful rays. Stabilizers are additives, which are compounded with plastics to provide the shield and improve its resistance to UV rays. These stabilizers are added to the plastic before moulding. The stabilizers absorb or screen out the damaging UV light and transform the energy of the rays, the UV light, into heat, which is dissipated harmlessly throughout the product. Carbon Black is most popular and cost effective UV stabilizer for plastic and rubber. Research and experimental data has shown that the tensile strength of natural material (no color added) falls below 50% in less than 6 months of exposure. With addition of carbon black, even after 30 months exposure, the product still retains more than 90 % of its strength. This clearly illustrates the effectiveness of carbon black as an excellent UV stabilizer. It is experimentally proven that 2.5% addition of carbon black gives best result. So you need to add carbon black master batch in quantity so as to get 2.5% carbon black in final product.

Pursuing excellence in Rotational Moulding Technology.

How to achieve 2.5%Carbon Black: It is very important for rotational moulder to achieving 2.5% carbon black in tank material so as to offer maximum guarantee to customer. All black master batches looks alike but carbon black loading may not be the same. Normally carbon black loading varies from Few New Products : 30% to 60 %. Find out from your master batch supplier how much is loading. If carbon loading in master batch is X%=50%. For every 100 Kg of LLDPE you need to add 2.5 kg of raw carbon. So you will need to add ( 2.5 x 100/X ) Kg i.e. 5 kg of master batch of 50 % to be added to 100 kg of LLDPE to get 2.5% loading. If the carbon black is poorly dispersed or diluted, its full benefit will not be realized. Rotational moulding process does not contribute much to dispersion of carbon black as rotational moulding is very low shear process. It is highly advisable to achieve proper dispersion during compounding. Dry blending of carbon black with LLDPE powder in high Children Desk speed mixture is not right way of dispersion and should be avoided. Expected life of Single Layer all black tank with 2.5% carbon content is highest i.e. more than 15 years. Double Layer Tank with outer black layer will last more than 10 years only if carbon content is 2.5% and black layer thickness in tank is more than 2.5 mm. Triple Layer Tank with middle black layer will last more than 10 years only if carbon content is 2.5% and black layer thickness is more than 2.0 mm. Most of the triple layer tank available in School Furniture market does not have sufficient thickness of black layer & are expected to fail before 10 years. In nutshell it is very important to understand the importance of Carbon Black content in tank material and maintain 2.5% carbon black loading and minimum of 2.5 mm thickness of black layer in multilayer tank.

This news letter is for internal circulation only. For subscription e mail: [email protected] Pursuing excellence in Rotational Moulding Technology.