dr dre beats radical polymerization

ddkity82 · Wysłany: 31 Mar 2011, 05:0 Temat postu: dr dre beats radical polymerization

Polythene bag manufacturers make polythene products for use in many different industries. Some of these industries will include:
Construction Retail supply chain Environmental Manufacturing Agriculture & Horticulture
Polythene contains the chemical elements hydrogen and carbon, and is created by the polmerization of ethene. It may also be produced by anionic addition polymerization, radical polymerization, cationic addition polymerization or ion coordination polymerization, and each of these various methods will produce a different type of polyethylene.

All these different types of polythene are classified into several different categories ranging from very low density polythene ( VLDPE ) to ultra high molecular weight polythene ( UHMWPE ).

Very low density polythene (VLDPE) is used for food packaging, stretch wrap,[link widoczny dla zalogowanych], frozen food bags,[link widoczny dla zalogowanych], hoses and tubing.

There are many different applications and uses for polythene and probably the one most commonly seen is the everyday plastic bag. Millions of tons of plastic bags are manufactured and used every year, and some companies now produce a biodegradeable plastic bag which is made using sugar cane.

Polythene is used all over the world and this makes it an important environmental issue. Polythene can be recycled but most of it ends up in landfills. It is generally considered non- biodegradeable as it may take hundreds of years for it to efficiently degrade. However, it was discovered in 2008 that a type of bacteria can degrade over forty percent of the weight of the plastic bags in less than three months. This discovery was made by Daniel Burd a sixteen year old Canadian.

There are four main stages in the production of polythene bags, and these are:
Raw Material : Film : Printing : Final Product
The main ingredient in most plastics is polyolefins hydrocarbons, mainly natural gas or crude oil. The original polyethene was produced by a high pressure process, but newer types of polythene are produced with lower pressures. These processes produce granules which are sent to processing factories in sacks or bulk containers.

The next stage is to make polythene film. The granules are mixed with colouring agents and other additives if required,[link widoczny dla zalogowanych], and then conveyed to a film extruding machine. The finished rolls of film typically 100kg each and up to 10,000 meteres in length, are removed for the next stage. All standard bags and carriers have one side open and three sides closed, and there are two methods of making bags; sideways or lengthways.

The sideways method, the bags are produced sideways on by a machine using a hot knife to cut and seal the tubular film to form the sides of the bag, the bottom being the fold in the tubular film. These are called side-weld bags.

Lengthways - using this method, the layflat tube is pulled through the machine and a hot wire makes a seal across the tube while a flying knife cuts the film below the seal whilst the film is motionless for the sealing process. Thus the seal forms the bottom of the bag and the folds of the layflat tubing, the sides. These are called bottom-weld bags.