Plastics Engineering Interview Questions and Answers
Question - 31 : - Do Plastic Grocery Bags Block Drains During The Rains?
Answer - 31 : -
Unlikely.Plastic grocery bags are lighter (less dense) than water; hence, they float. This is why they accumulate on the beaches when disposed indiscriminately. In the case of a vertical grill in the drainage system, the water will flowthrough the grill with the plastic bags floating on the surface. In the case of a horizontal grill such as the one found on the roadside, the bags will be displaced by flowing water. By applying this logic, it is difficult to understand how plastic grocery bags are responsible for blocking drains. Perhaps, someone should carefullyobserve and determine what is the real porblem.
Question - 32 : - Are Plastics Toxic When Used In Contact With Foods And Medicines?
Answer - 32 : -
NO. Plastics are used world-over because they are safe for packaging of foods, medicines and child care products. A few examples are - milk pouches, edible oil container, ice-cream packs, blister packs for tablets and capsules.I.V.fluids and blood is collected and stored in plastic bags.
While plastics are safe for packaging of food and medicinal products, there are standards in each country,which specify the type of Additives and Pigments, which can be used safely for contact with foods.
Question - 33 : - Are Plastics Hazardous When Buried In Land-fills?
Answer - 33 : -
NO. Plastic waste is pre-dominantly eco-neutral or inert. It does not generate toxic leachates which contaminate the soil or ground water resources. On the contrary, those products which do biodegrade with by-products,may result in contaminating ground water resources.
Plastic consumer waste is easily compactible, and occupies less space inland-fills.
The fact that plastic waste is inert and does not biodegrade, makes segregation and recycling a more logical approach to waste managment, for urban areas.
The famous study on excavation of New York's land-fills by the University of Arizona, U.S.A., reveals that fooditems, such as beef-stakes, corn-on-cob, news papers - things which you might expect to biodegrade in a fewyears, are in recognisable form after 30 years. This is because, anaerobic biodegradation (in the absence of airand sun-light) is an extremely slow process. This process also generates methane gas from land-fills - which for its "green-house" effect is worse than carbon dioxide.
Question - 34 : - Does The Burning Of Plastic Generate Toxic Fumes?
Answer - 34 : -
NO. To a large extent, post-consumer waste is made up of grocery or polyethylene bags. The chemical structure of polyethylene is made up only by carbon & hydrogen atoms. Anyone, who has done elementary chemistry will know that burning a carbon hydrogen molecular chain will generate carbon-dioxide and water vapour.
A product made from PVC, when burnt in an open fire will emit hydrogen chloride fumes which are pungent. In fact this property has a singnificant advantage in retarding propagation of a flame when used as a sheath in a
power cables. Normally a PVC product or a post consumer pack is extremely rare, in Municipal solid waste.
The toxic fumes which the public wrongly believe are generated from plastics, are the result of burning materials contained in the bag, to get ride of industrial wastes.
Question - 35 : - Should We Change Over From Plastic To Paper Bags?
Answer - 35 : -
A decision should be made after considering these facts.
The wide spread belief that substitution of plastics with paper is more favourable to the environment, is not supported by facts and a L.C.A.
The manufacture of paper bags requires two-and-half times the energy as compared to plastic bags of the same size and for comparable performance.
The manufacture of paper produces singnificantly higher air pollutants. There is a huge disparity in waste water discharge in manufacture or recycling of paper.
As far as biodegradability is concerned, the University of Arizona study shows that newspapers burried in 1952 in land-fills and excavated in 1989, were legible. The same observation was made with telephone directories.
Some will argue that paper comes from trees which is a renewable resource; while plastic is manufactured from oil, which cannot be replaced. The argument against this is, that forests play an important role in protecting our soil bank and maintaining the gaseous balance in our atmosphere, by absorbing carbon dioxide and in turn releasing oxygen. In our hunger for wood, 44 million hectares of forests have been felled since Independence, making this country a land with one of the lowest areas under forest cover (area under forest to total land area). Therefore, as far as India is concerned land is not a renewable resource.
Question - 36 : - Do Plastics Meet The Criteria Of Resource Conservation; - Do We Get "more For Less" While Using Plastics Packaging?
Answer - 36 : -
YES, Let us take the example of the humble plastic grocery bag whcih has been denigrated so extensively in the media. A stack of 2000 plastic grocery bags will be seven-and-half INCHES high; a stack of 2000 paper grocery bags will have a height of seven-and-half feet. Imagine what this means in terms of transportation, and the increase in exhaust emissions.
A study conducted by the "German Society for Reasearch in the Packaging Market", shows that if plastics packaging were replaced with other materials, the weight and volume of disposables would increase by a factor of 4 and 2.5 respectively, along with twice the level of energy consumption and double the cost of packaging.
Another good example is the transport of mineral water in light weight PET bottles. A truck can carry 60% more water with 80% less packaging, as compared to glass bottles; this results in fuel savings of almost 40%.
The ratio of product weight packed to the weight of package is the highest for plastics packaging; for example 500 gms of coffee can be packed in a glass jar weighing 500 gms, or a tin plate container weighing 130 gms, or a plastic laminated pouch weighing only 12 gms. Still better, one kg of salt is packed in a pouch weighing 5 gms where the ratio of product weight to package weight is 200:1. These are some examples of getting "more from less" through plastics packaging.