lijit search

Sunday, March 28, 2010

Plastic recycling

In November 2007, a small group of six US citizens-two screenwriters, a physicist, a marine biologist, a philosopher and a science journalist-began working  to restore science and innovation to America’s political diologue.Here are Barack Obama’s answers to some of their questions with global reference-: The US must get off the sidelines and take long overdue action to reduce it’s own greenhouse gas emissions.This is a global problem.US leadership is essential but solution requires contribution from all parts of the world particularly China,Europe and India. President Obama-:”I will restore U.S. leadership in strategies for combating climate change and work closely with international community.I will create a global energy forum-based on the G8+5,which includes all G-8 members plus Brazil, China, India , Mexico and south Africa,comprising the largest energy consuming nations from both the developing and developed world.This forum would focus exclusively on global energy and environmental issues and  will also create a technology transfer Program dedicated  to exporting climate-friendly technologies, including green buildings, clean coal and advanced automobiles, to developing countries to help them combat climate change.” He said further-:”America’s challenges in providing  secure,affordable energy while addressing climate change mean that we must make much more efficient use of energy and begin to rely on new energy sources that eliminate or greatly reduce greenhouse gas emissions.” The President proposed programs that , taken together , would increase the federal investment in the energy research , development,deployment by $150 billion over ten year. He also encouraged communities around the nation to design and build sustainable communities the that cut energy use with walkable  community design .

There is a growing problem regarding recycling of plastic. Discarded plastic products and packaging contribute to a growing portion of Municipal Solid Waste. In recent times the amount of plastic thrown has increased by more than 50 percent than at the beginning 0f 1990s. Plastic waste accounts for one-fifth of all waste in waste stream.Plastic recycling ws never expected to be widespread because the process is too expensive, unpractical and inefficient.This though is slowly being turned.

The difference between a polymer and a plastic
The term “plastics” is used to describe a wide variety of resins or polymers with different characteristics and uses. While all plastics are polymers, not all polymers are plastic. Polymers are rarely useful in themselves and are most often modified or compounded with additives (including colours) to form useful materials. The compounded product is generally termed a plastic.

For this discussion of recycling, an understanding of two basic types of polymers is helpful:
Thermoplastic polymers can be heated and formed, then heated and formed again and again. The shape of the polymer molecules are generally linear or slightly branched. This means that the molecules can flow under pressure when heated above their melting point.
Thermoset polymers undergo a chemical change when they are heated, creating a three-dimensional network. After they are heated and formed, these molecules cannot be re-heated and re-formed. Comparing these types, thermoplastics are much easier to adapt to recycling.

Plastic consumer goods not identified by code numbers are not usually collected. Plastic tarps, pipes, toys, computer keyboards, and a multitude of other products simply do not fit into the numbering system that identifies plastics used in consumer containers. There are actually thousands of different varieties of plastic resins or mixtures of resins. These are developed to suit the needs of particular products. There is limited recycling of some of these specific plastic products in truckload quantities from industrial sources. No one has entered the business of collecting a variety of these plastics in small quantities.

The Problem with Plastics Recycling
When glass, paper and cans are recycled, they become similar products which can be used and recycled over and over again. With plastics recycling, however, there is usually only a single re-use. Most bottles and jugs don't become food and beverage containers again. For example, pop bottles might become carpet or stuffing for sleeping bags. Milk jugs are often made into plastic lumber, recycling bins, and toys.

Currently only about 3.5% of all plastics generated is recycled compared to 34% of paper, 22% of glass and 30% of metals. At this time, plastics recycling only minimally reduces the amount of virgin resources used to make plastics. Recycling papers, glass and metal, materials that are easily recycled more than once, saves far more energy and resources than are saved with plastics recycling.

There are five factors that are necessary in order for the recycling of plastic to be a successful process. First, the supply of used plastic has to be of a large quantity. This large quantity of plastic is collected at certain areas, which is the second step. Once the plastic is collected, the sorting and separating process begins; this is the third step in the process. The sorting and separating process depends upon the type of polymers that make up the plastic. Plastic products are given codes to help the sorting and separating process. The fourth step in plastic recycling is reprocessing. The reprocessing of polymers includes the melting process, the melting process can be accomplished if the polymers have not been widely cross-linked with any synthetics. If the cross-linking of polymers contain too many synthetics, the polymers will be difficult to stretch and less pliable. The final step is the manufacturing of the melted plastic into new products.


Post a Comment