Degradable Plastic   

Retailers supplying degradable plastic bags are seen to be proactive about reducing pollution in the environment and environmentally friendly. In those instances where retailers have instituted these bags there has been very positive feedback from customers.

OMNIpac PTY LTD believes by establishing effective recycling programmes and the use of photodegradable polymers can eliminate many of the environmental problems associated with shopping bags. The following report, discusses why plastic shopping bags should remain in use and how photodegradable additives can assist in reducing the impact these bags have on the environment.

High-density polyethylene is the material used to manufacture plastic check out bags and is derived from ethylene gas, which is a byproduct of the manufacture of petroleum. The ethylene molecules are linked together to make long chains comprised of carbon molecules linked together with hydrogen molecules attached along the sides. These long chain molecules have a very high tensile strength.

A recent study in the U.S.A. found that the manufacturing of plastic products is not only more cost effective than substitute products but is also less damaging on the environment and in particular:

• Plastic shopping bags are more energy efficient - 30 percent less energy used compared to the paper alternative
• Plastic shopping bags are less polluting, with 77 percent less solid waste during manufacturing and distribution
• 68 percent less atmospheric emissions
• 93 percent fewer waterborne wastes

In addition, at the time of disposal, plastic bags:

• can be easily recycled requiring far less energy to do so than alternative products
• if disposed of, require less space in landfills
• are chemically inert therefore resist decomposition into gasses which can increase the greenhouse effect
• maintain the integrity of garbage in landfill sites preventing subsidence and allowing completed sites to be used for other purposes such as parks
• Modern day landfills are designed to contain their contents in a dry anaerobic atmosphere which is not conducive to degradation, to the extent that vegetable items do not quickly break up in these sites.

The major benefits to consumers of plastic shopping bags are:

• Their low cost
• Their carrying capacity
• Their ease of distribution
• Their waterproof ability
• The cost savings they provide to retail stores
• Bag design allows for large amounts of goods to be carried at once
• Bags may be re-used as dustbin liners and household containers
• Security in terms of not displaying the contents
can be easily recycled requiring far less energy to do so than alternative products

• Security in terms of printed store bags identifying the shop from which items were bought
• Ease of packing at grocery check out stations enables fast customer processing
• Advertising and brand awareness

This creates problems in terms of visual pollution on land and a danger to animals that may eat the bag. This last point is especially pertinent to sea creatures, which can mistake the bags for jellyfish.

Unfortunately these programs have only been marginally successful due to consumer apathy, lack of motivation or re-use of bags for other purposes.

In order to recycle plastic shopping bags into similar products the bags need to be kept relatively clean and separated from other types of plastic which can contaminate the end product. Providing facilities to ensure this happens is extremely difficult and costly.

There are some products, which can utilize assorted plastic waste, but the volumes required by these industries is a fraction of the amount generated initially.

Unfortunately the above solution although very desirable does not address the main pollutant factor of plastic bags i.e. litter.

These biodegradable products do not have the tensile strengths of 100% polyethylene and therefore significantly more material has to be used to achieve the same end use. These raw materials are also more expensive and consequently less cost effective to use.

The control of the degradation process is not exact and depends on the environment in which the bag is disposed of. In a modern day landfill these biodegradable bags will decompose very slowly and if they are in an environment containing few microbes such as, if the biodegradable bag were blown onto a fence it does not degrade.

Moisture levels in the air can affect these biodegradable bags lifespan.

Photodegradable Additives
Photodegradable plastics unlike biodegradable plastics use additives that are included in small proportions into the polymer when making the plastic bag.

The photodegradable additive once exposed to ultra violet light releases free radicals, which migrate throughout the material of the bag. These cause localized oxidization of the long chain molecule causing the chains to break into ever decreasing lengths thereby reducing their tensile strength and making the material of the bag extremely brittle.

Once this degradation process has commenced it does not stop. Even under the influence of outside mechanical action such as wind or waves, the photodegradable bag breaks up into ever-smaller pieces until it forms inert dust size particles.

The greater the exposure to ultra violet light the faster the destruction of the plastic, exposure to 7 days sunshine is adequate to commence the degradation process.

After considering all the advantages and disadvantages of the two types of degradable polymers OMNIPAC has elected to manufacture photodegradable plastic bags and has been doing so for some 12 months.

All research and practical studies performed by the staff of OMNIpac indicates that photodegradable polymers provide a direct solution to the major environmental polluting effects of plastic bags while maintaining all the consumer and retailer benefits of the bags.
For more information please do not hesitate to contact OMNIpac.

Retailers supplying degradable plastic bags are seen to be proactive about reducing pollution in the environment and environmentally friendly. In those instances where retailers have instituted these bags there has been very positive feedback from customers.