Causes Of Plastic Pollution Due To Plastic Bags, Bottles, Containers, Recycled Plastics…

Plastic Pollution, Causes Of Plastic Pollution Due To Plastic Bags, Bottles, Containers, Recycled Plastics

Plastic is one of the few new chemical materials which pose environmental problem. Polyethylene, polyvinyl chloride, polystyrene is largely used in the manufacture of plastics. Synthetic polymers are easily molded into complex shapes, have high chemical resistance, and are more or less elastic. Some can be formed into fibers or thin transparent films. These properties have made them popular in many durable or disposable goods and for packaging materials. These materials have molecular weight ranging from several thousands to 1, 50,000. Excessive molecular size seems to be mainly responsible for the resistance of these chemicals to biodegradation and their persistence in soil environment for a long time.

Plastic in the environment is regarded to be more an aesthetic nuisance than a hazard, since the material is biologically quite inert. The plastic industry in the US alone is $ 50 billion per year and is obviously a tempting market for biotechnological enterprises. Biotechnological processes are being developed as an alternative to existing route or to get new biodegradable biopolymers. 20% of solid municipal wastes in US is plastic. Non-degradable plastics accumulate at the rate of 25 million tones per year. According to an estimate more than 100 million tones of plastic is produced every year all over the world. In India it is only 2 million tones. In India use of plastic is 2 kg per person per year while in European countries it is 60 kg per person per year while that in US it is 80 kg per person per year.

Causes of Plastic Pollution:

Plastics are used because they are easy and cheap to make and they can last a long time. Unfortunately these same useful qualities can make plastic a huge pollution problem. Because the plastic is cheap it gets discarded easily and its persistence in the environment can do great harm. Urbanization has added to the plastic pollution in concentrated form in cities. Plastic thrown on land can enter into drainage lines and chokes them resulting into floods in local areas in cities as experienced in Mumbai, India in 1998. It was claimed in one of the programmes on TV Channel that eating plastic bags results in death of 100 cattle per day in U.P. in India. In stomach of one dead cow, as much as 35 kg of plastic was found. Because plastic does not decompose, and requires high energy ultra-violet light to break down, the amount of plastic waste in our oceans is steadily increasing. More than 90% of the articles found on the sea beaches contained plastic. The plastic rubbish found on beaches near urban areas tends to originate from use on land, such as packaging material used to wrap around other goods.

On remote rural beaches the rubbish tends to have come from ships, such as fishing equipment used in the fishing industry. This plastic can affect marine wildlife in two important ways: by entangling creatures, and by being eaten. Turtles are particularly badly affected by plastic pollution, and all seven of the world’s turtle species are already either endangered or threatened for a number of reasons. Turtles get entangled in fishing nets, and many sea turtles have been found dead with plastic bags in their stomachs. Turtles mistake floating transparent plastic bags for jellyfish and eat them. In one dead turtle found off Hawaii in the Pacific more than 1000 pieces of plastic were found in the stomach. A recent US report concluded that more than 100000 marine mammals die each year in the world’s oceans by eating or becoming entangled in plastic rubbish, and the position is worsening World-wide, 75 marine bird species are known to eat plastic articles. This includes 36 species found off South Africa. A recent study of blue petrel chicks at South Africa‘s remote Marion Island showed that 90% of chicks examined had plastic in their stomachs apparently fed to them accidentally by their parents. South African seabirds are among the worst affected in the world. Plastics may remain in the stomachs, blocking digestion and possibly causing starvation.

Processing of Bioplastics:

Presence of nucleating agents (which facilitate crystallization) or the use of plasticizer shortens the processing cycles during the moulding operations. There are two main points about processing of PHBV bioplastics – (i) The limited thermal stability of the polymer and so it degrades rapidly above 195 degree centi. (ii) The need to optimise conditions to allow a maximum crystallization rate (which reduces cycle times). The maximum rate of crystallization is reported to be at about 55-60 degree centi. which is significantly closer to Tg than the Tm. Processing temperatures should not exceed 180 degree centi. and duration of time when the material is in melt state should be kept minimum.

At the end of a run the processing equipment should be purged with polyethylene. When blow moulding the blow-pin and the mould should be at about 60 degree centi to optimise crystallisation rates. Similarly injection moulds are recommended at 55-65 degree centi. The low-hydroxyvalerate, unplasticised grades are most critical to process, requiring the higher processing temperatures. Conditions are slightly less critical with the higher hydroxyvalerate containing and plasticised grades. In addition to producing PHAs in dry powder form for melt processing, Metabolix is also developing PHA latexes. These materials have unique film forming properties, which are finding application in higher performance applications as well as in more traditional commodity uses. Metabolix Company supplies PHA samples to companies under research and development agreements.

 Source: http://members.rediff.com/jogsn/bp4.htm