Composition and Types of Plastic
A plastic is made up principally of a binder together with plasticizers, fillers, pigments, and other additives. The binder gives a plastic its main characteristics and usually its name. Thus, polyvinyl chloride is both the name of a binder and the name of a plastic into which it is made. Binders may be natural materials, e.g., cellulose derivatives, casein, or milk protein, but are more commonly synthetic resins. In either case, the binder materials consist of very long chainlike molecules called polymers. Cellulose derivatives are made from cellulose, a naturally occurring polymer; casein is also a naturally occurring polymer. Synthetic resins are polymerized, or built up, from small simple molecules called monomers. Plasticizers are added to a binder to increase flexibility and toughness.
Fillers are added to improve particular properties, e.g., hardness or resistance to shock. Pigments are used to impart various colors. Virtually any desired color or shape and many combinations of the properties of hardness, durability, elasticity, and resistance to heat, cold, and acid can be obtained in a plastic. There are two basic types of plastic: thermosetting, which cannot be resoftened after being subjected to heat and pressure; and thermoplastic, which can be repeatedly softened and remolded by heat and pressure. When heat and pressure are applied to a thermoplastic binder, the chainlike polymers slide past each other, giving the material “plasticity.” However, when heat and pressure are initially applied to a thermosetting binder, the molecular chains become cross-linked, thus preventing any slippage if heat and pressure are reapplied.
The Essay on Biodegradable Plastics from Cassava Starch
Workshop Guide Make your own Bio-Plastic Description A workshop focusing on the problems of plastics made by fossil fuels and a look into making your own bio-plastic. At a glance Total time: 1 hour Learning Styles: Visual, auditory, practical, participatory, teamwork Objectives: To learn about the challenges facing fossil fuel plastics and how to make your own bio-plastic Audience: Anyone Max/Min ...
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Be Wise With Plastics
Plastics are everywhere and in most cases are very affordable and convenient. But, increasingly scientists are finding that a hidden cost may be our health. Some common plastics release harmful chemicals into our air, foods, and drinks. Maybe you can’t see or taste it, but if you’re serving your dinner on plastic, you’re likely eating a little plastic for dinner.
Beyond the immediate health risks, our increasing use of plastics is causing an enormous amount of enduring pollution. Every bit of plastic that has ever been created still exists (except for the little bit that has been incinerated, which releases toxic chemicals).
In the ocean, plastic waste is accumulating in giant gyres of debris where, among other thing, fish are ingesting toxic plastic bits at a rate which will soon make them unsafe to eat.
Plastic is generally toxic to produce, toxic to use, and toxic to dispose of. Luckily, we can all make safer choices.
What to Do
The best thing to do is to reduce your use of plastic. Look for natural alternatives like textiles, solid wood, bamboo, glass, stainless steel, etc. Also, look for items with less (or no) plastic packaging. If you do buy plastic, opt for products you can recycle or re-purpose (e.g. a yogurt tub can be re-used to store crayons).
And, get to know your plastics – starting with this guide: The most common plastics have a resin code in a chasing arrow symbol (often found on the bottom of the product).
PET (Polyethylene Terephthalate):
AVOID
Common Uses: Soda Bottles, Water Bottles, Cooking Oil Bottles Concerns:
Can leach antimony and phthalates.
HDPE (High Density Polyethylene): SAFER
Common Uses: Milk Jugs, Plastic Bags, Yogurt Cups
PVC (Polyvinyl Chloride, aka Vinyl): AVOID
Common Uses: Condiment Bottles, Cling Wrap, Teething Rings, Toys, Shower Curtains Concerns: Can leach lead and phthalates among other things. Can also off-gas toxic chemicals. LDPE (Low Density Polyethylene):
The Essay on Dangers of Plastic Bottles
Plastic bottles are hugely popular these days for their convenience and perceived purity, as portrayed by effective marketing strategies. But according to the Natural Resources Defense Council, consumers should not assume that bottled water is safe. Reusing plastic drink bottles is not recommended, as it increases the likelihood of impurities due to the introduction of bacteria and the potential ...
SAFER
Common Uses: Produce Bags, Food Storage Containers
PP (Polypropylene): SAFER
Common Uses: Bottle Caps, Storage Containers, Dishware
PS (Polystyrene, aka Styrofoam): AVOID
Common Uses: Meat Trays, Foam Food Containers & Cups
Concerns: Can leach carcinogenic styrene and estrogenic alkylphenols Other this is a catch-all category which includes:
PC (Polycarbonate): AVOID – can leach Bisphenol-A (BPA).
It also includes ABS (Acrylonitrile Butadiene Styrene), SAN (Styrene Acrylonitrile), Acrylic, and Polyamide. These plastics can be a safer option because they are typically very durable and resistant to high heat resulting in less leaching. Their drawbacks are that they are not typically recyclable and some need additional safety research. New plant-based, biodegradable plastics like PLA (Polylactic Acid) also fall into the #7 category.
