Sunday, October 5, 2008

More on Plastic

Adapted from "The Green Guide" #77, The Green Guide Institute.

With all the recent press about plastics leaching harmful chemicals into food, we want to be sure we’re using the safest materials in our children’s lunchboxes.

Get the scoop on which plastics are safe to use right here:

Chemicals that leach from plastic containers into food include suspected carcinogens or endocrine disrupters, which have been linked to reproductive system harm. Plastic used for containers can be identified by their recycling codes, as listed in this article.

Most wraps on pre-packaged foods lack identifying symbols. Here is a great list from The Green Guide Institute from which you can tell at a glance the plastics that are safe for food storage and those that aren’t:

As a precaution, you can unwrap these foods and store them in nontoxic glass, ceramic or steel bowls, or Ziploc bags (made of LDPE). Heat promotes leaching:

To be safest, never microwave or heat foods in plastics.

1. Polyethylene Terephthalate (PETE or PET): No known hazards.

2. High Density Polyethylene (HDPE): No known hazards.

3. Polyvinyl Chloride (PVC or vinyl): Plasticizers are added to many PVC products to make them flexible. These include phthalates — suspected endocrine-disrupting chemicals (EDCs), DEHA, another possible EDC, was found to leach from PVC cling wraps into cheese. Grocery stores commonly use PVC to wrap deli meats and cheeses. Reyonds cling wrap is PVC. Some waters and vegetable oils are bottled in PVC. Ad PVC’s manufacture and incineration produces highly toxic dioxins, as does the PVDC used in Saran Wrap, according to Consumers Union.

4. Low Density Polyethylene (LDPE): No known hazards.

5. Polypropylene (PP): No known hazards.

6. Polystyrene (PS or Styrofoam): Made from styrene, a suspected carcinogen, PS also contains p-nonylphenol; both chemicals are suspected EDCs. Do not consumer fatty foods or alcoholic beverages from Styrofoam containers; styrene can leach into these substances. Some opaque plastic cutlery is PS, as well.

7. Other Resins, including Polycarbonate (PC): Most clear plastic baby bottles and 5-gallon water bottles are made of PC. Bisphenol-A EDC in PC, has been found in water and heated infant formulas bottles in PC, as well as food cans lined with a plastic film.

For some more great tips on how and why to reduce your use of plastics –and for which ones are the biggest concern for your health and the environment — read these new guidelines from The Green Guide Institute .

This article was reprinted from “The Green Guide” newsletter, a publication of The Green Guide Institute. Since 1994, “The Green Guide” has been a premier consumer source for practical everyday actions benefiting environmental and personal health. Want more practical solutions that benefit the environment and personal health? Subscribe online to The Green Guide.

Saturday, October 4, 2008

Least Evil Among Plastics

Choose your water bottles very carefully in order to prevent chemicals in the plastic from leaching into your water.

Plastic water bottles are very convenient for carting water around when we are on the go, as they don't break if we drop them. However, it is worth paying attention to the type of plastic your water bottle is made of, to ensure that the chemicals in the plastic do not leach into the water. If you taste plastic, you are drinking it, so get yourself another bottle.

To be certain that you are choosing a bottle that does not leach, check the recycling symbol on your bottle. If it is a #2 HDPE (high density polyethylene), or a #4 LDPE (low density polyethylene), or a #5 PP (polypropylene), your bottle is fine. The type of plastic bottle in which water is usually sold is usually a #1, and is only recommended for one time use. Do not refill it. Better to use a reusable water bottle, and fill it with your own filtered water from home and keep these single-use bottles out of the landfill.

Unfortunately, those fabulous colourful hard plastic lexan bottles made with polycarbonate plastics and identified by the #7 recycling symbol, may leach BPA. Bisphenol A is a xenoestrogen, a known endocrine disruptor, meaning it disturbs the hormonal messaging in our bodies. Synthetic xenoestrogens are linked to breast cancer and uterine cancer in women, decreased testosterone levels in men, and are particularly devastating to babies and young children. BPA has even been linked to insulin resistance and Type 2 Diabetes. For more of the science on the effects of BPA on our endocrine system etc. see these studies: Environmental Health Perspectives Journal. Nalgene, the company that manufactures the lexan water bottles also makes #2 HDPE bottles in the same sizes and shapes, so we have a viable alternative.

Unfortunately, most plastic baby bottles and drinking cups are made with plastics containing Bisphenol A. In 2006 Europe banned all products made for children under age 3 containing BPA, and as of Dec. 2006 the city of San Franscisco followed suit. In March 2007 a billion-dollar class action suit was commenced against Gerber, Playtex, Evenflo, Avent, and Dr. Brown's in Los Angeles superior court for harm done to babies caused by drinking out of baby bottles and sippy cups containing BPA. So, to be certain that your baby is not exposed, use glass bottles.
Check the recycling numbers on all your plastic food containers as well, and gradually move to storing all food in glass or ceramic.

Store water in glass or brass if possible, and out of direct sunlight.


Friday, October 3, 2008

The Seven Types of Plastic

Why are most plastics marked with a number inside a recycling symbol? The simple answer is that each number represents the type of resin made to produce the plastic.

Because each resin is different, these numbers affect how and where you can recycle plastics. You don’t have to remember the name. Plastics are identified by numbers 1-7.

Here’s some common products you’ll find of each type:

#1 PET (Polyethylene terephthalate)*: soda bottles, oven-ready meal trays and water bottles

#2 HDPE (High-density polyethylene)*: milk bottles, detergent bottles and grocery/trash/retail bags

#3 PVC (Polyvinyl chloride): plastic food wrap, loose-leaf binders and plastic pipes

#4 LDPE (Low-density polyethylene): dry cleaning bags, produce bags and squeezable bottles

#5 PP (Polypropylene): medicine bottles, aerosol caps and drinking straws

#6 PS (Polystyrene): compact disc jackets, packaging Styrofoam peanuts and plastic tableware

#7 Other: reusable water bottles, certain kinds of food containers and Tupperware

*PET and HDPE are the most common forms of plastic, so they are the easiest to find recycling locations for


Thursday, October 2, 2008

The Plastic Age

We currently live in the 'Plastics Age' with a total consumption of about 182 million tonnes of polymers per year. Of this, polypropylene is 24 t
o 25 per cent and all polyethylenes, about 40 per cent. This industry has grown phenomenally in the last century. Its growth within this period will be of interest to many.

Human race has always progressed by using raw materials around. Growth from 'Stone Age' to 'Plastics Age' has been very rapid. Use of plastics within the last century and in particular, after World War II has increased exponentially.

Plastic is not a uniformly defined term. Its origin is from the Greek word 'Plasticos', which means 'to form or mould'.
Plastics can broadly be defined or described as materials composed essentially of very large molecules (called macromolecules or polymers) which may be natural, semi natural (modified natural) or synthesised from small molecules, termed as monomers.

At times, plastics and polymers are used as synonyms in the colloquial world. Some prefer to differentiate the two by defining plastics as made by compounding polymer and additives. Polyvinyl chloride is a polymer, but when compounded with a plasticiser and the thermal stabiliser, it may be termed as a plastic.

Some polymers may not need any additives and these can be used as such in their virgin form. It is preferable to use the word polymer instead of plastic, as the word polymer denotes big or giant molecules. 'Poly' means many and 'mer' indicates substance.

Classification of Polymers

Polymers can be classified based on their end uses or origin of raw materials.

Classification based on End-uses

This type of classification also highlights different market and key properties depending upon specific use. Thus, adhesives need totally different properties from materials used as consumer goods like packaging films, ice cream cups, paints or moulded furniture.

Thermoset Polymers: Thermosets were the early polymers made synthetically. The first totally synthetic polymer, Phenol, Formaldehyde was, in fact, thermoset in nature, its moulding powder, polyurethane foams used in sofa seats, automobile seats or the 'setting adhesives' are examples of thermoset resins. Thermoset materials 'set' when heated (thermal effect). One can imagine boiling of an egg. The yolk becomes hard or it is 'set'. Once it is set, it cannot be reprocessed again. It does not become liquid again.

Thermoplastic Polymers: Thermoplastic materials melt when heated and can be shaped as desired. They can be reheated and melted several times. Polyethylene, polypropylene, polystyrene, nylon, polyester and PVC are examples of thermoplastic polymers. Today, production of thermoplastic polymer is several times that of thermoset polymers.

Rubber: Rubber can be natural or synthetic, such as styrene-butadiene-styrene block copolymer, nitrile rubber, silicone rubber or isoprene. The high impact is the key property for rubber.

Fibers: Polymers for fibers need different properties as compared to rubber or thermoplastics used in furniture or in milk packaging. Fibers have textile and non-textile applications. For textile applications, dyeability, washability, lightness and comfort on feel are major properties; while that for non-textile use, solvent resistance or tenacity may be of importance. Polyester and nylon are commonly used in textile applications, whereas polypropylene has properties suitable for non textile use.

Adhesives: These polymers must have a good adhesion between different substrates and good bonding strength. It should be easy to apply on the surface. Poly vinyl alcohol, epoxy polymers or cyno acrylic polymers are examples of adhesives.

Paints and Inks: These polymers should have a film forming ability, good flow properties and sufficient tack to the surface on which they are applied. They should be able to incorporate large quantities of pigments. Inks on paper or plastics have different properties. Alkyd polymers, polyesters, epoxy polymers or amino polymers are common examples.

Classification of Polymers based on Origin of Raw Materials

Polymers can be classified based upon their origin, as:

Natural Polymers: These occur as macromolecules or polymers in their natural form. Cellulose, starch, sugar, lignin etc. have plant origin. Other materials such as shellac, wool etc. have animal origin. All these materials are natural polymers. They exist in nature. It is interesting to know that different starches behave differently due to difference in their spatial structure although their chemical formulae are the same.

Semi-Natural or Modified Natural Polymers: Most natural polymers cannot be used in their virgin or native form, but can be chemically modified. Thus, cellulose when treated chemically (acetylated) yields cellulose acetate, which can be spun into fibre, extruded or injection moulded. Carboxy methyl cellulose, CMC, dissolves in water but cellulose itself does not. Thus, cellulose acetate or CMC can be classified as semi-natural polymers.

Synthetic Polymers: These are made from monomers through a chemical reaction, called polymerisation. Polyethylene, polypropylene, nylon, polyvinyl chloride, polyester etc. are examples of synthetic polymers. Although synthetic polymers outnumber natural polymers, the total quantum of natural polymers is far greater than synthetic polymers.

(Source: Prof. D.D. Kale, Ex-HOD, Polymer Department, UICT, Mumbai)
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