Saturday, December 12, 2009


Plastics are making inroads into the machinery fabrication industry which normally prefer metals like steel and aluminum because of their strength, amenability to complicated designs and established fabrication technology. When it come to food industry most preferred construction material for processing machinery that comes in contact with the food is stainless steel. Use of plastics was far and few since they do not have many of the properties necessary for the fabrication of process machinery used by the food industry. Food grade plastics find use in limited areas like making containers, hoppers, conveyor belts etc which are not exposed to high wear and tear and temperatures beyond 100C. Of course Teflon is an exception as it has high temperature resistance and is one of the most efficient anti-friction materials available to day. But its fabrication potential is restrained as it cannot be melt processed and it has to be compressed and sintered to form useful shapes.

The advent of Acetal plastics has changed the scenario and this is one of the most sought after plastic fabrication material by the engineering industry. Acetal polymer, the polymerized formaldehyde or better known as Polyoxymethylene (POM) has every thing a fabricator can ask for and many more user friendly features. POM has superb inherent mechanical properties in respect of dimensional stability, strength, stiffness, low wear characteristics, low friction coefficient, , creep resistance, high surface hardness, low moisture absorption, dynamic fatigue resistance, inert towards aliphatic and aromatic hydrocarbons, alcohols, esters, gycerols, ketones, detergents, gasoline etc though it cannot resist strong acids. It can stand up to 93C temperature and can replace metal parts in many machinery through injection molding process. Complex geometric features can be achieved using Acetal plastic resins. Some of the machine parts that can be fabricated include conveyor belt components like links, pins etc, fabricated parts of many processing machinery, scrapers, turned parts, threaded components, moving mechanisms, pulleys, gears, bushings, springs, pumps etc.

POM comes as homoploymer or copolymer with slightly different characteristics and food industry prefers copolymer material because of features like increased thermal stability, better elongation properties and toughness. These properties are achieved by addition of ethylene oxide at random to the homo polymer chain. With a temperature range for operation between -40C and 80C, tensile strength of 8800 psi and a specific gravity of 1.41, Acetal plastics are here to stay as an ideal fabrication material for a wide spectrum of industries in the coming years. Coating with Teflon can further improve the performance in terms of non-stickiness and friction reduction.

Two properties now being incorporated in Acetal plastics are metal detectability with conventional detection equipment and antimicrobial features which make them much superior to other fabrication materials. Foods being processed in machinery with parts made of Acetal plastics can be guaranteed to be free from contamination with particles of POM up to a size of 3 cubic millimeter if metal detection step is part of the manufacturing system. Similarly the antimicrobial properties against bacteria, mold and yeast make Acetal plastics ideal choice for fluid food contact applications. Safety approval by USFDA for its use by food industry probably will see its wide scale use in the coming years by the food machinery industry all over the world.


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