LISTS OF ACCEPTABLE POLYMERS FOR USE IN FOOD PACKAGING APPLICATIONS

Tables 1 to 12 list polymers that have been granted no objection statusby the Food Packaging Materials & Incidental Additives Section of theChemical Health Hazard Assessment Division (Food Directorate) foruse in food packaging applications. The polymers are coded andcategorized as shown in the following table.
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LISTS OF ACCEPTABLE POLYMERS FOR USE IN FOOD PACKAGING APPLICATIONS 1 Food Packaging Materials Food Packaging Materials LISTS OF ACCEPTABLE POLYMERS FOR USE IN FOOD PACKAGING APPLICATIONSTables 1 to 12 list polymers that have been granted no objection statusby the Food Packaging Materials & Incidental Additives Section of theChemical Health Hazard Assessment Division (Food Directorate) foruse in food packaging applications. The polymers are coded andcategorized as shown in the following table. POLYMER CATEGORIES Table No. Polymer Type Code 1 polyethylenes PE 2 polypropylenes PP 3 polystyrenes PS 4 polyvinyl chlorides PVC 5 ionomers I 6 polyethylene terephthalates PET 7 polyvinyl acetates PVAc 8 polycarbonates PC 9 polyamides PA 10 polyvinyl alcohols PVOH 11 polyvinylidene chlorides PVDC 12 Others O For polycarbonate at a glance, click here. 2 Food Packaging MaterialsPolycarbonate, or specifically polycarbonate of bisphenol A, is a clear plastic used to makeshatterproof windows, lightweight eyeglass lenses, and such. General Electric makes this stuffand sells it as Lexan.Polycarbonate gets its name from the carbonate groups in its backbone chain. We call itpolycarbonate of bisphenol A because it is made from bisphenol A and phosgene. Thisstarts out with the reaction of bisphenol A with sodium hydroxide to get the sodium saltof bisphenol A.The sodium salt of bisphenol A is then reacted with phosgene, a right nasty compoundwhich was a favorite chemical weapon in World War I, to produce the polycarbonate.What? You want the gritty details of the reaction? Then click here and you will not bedisappointed.Another polymer used for unbreakable windows is poly(methyl methacrylate).Seeing Another Polycarbonate More Clearly 3 Food Packaging MaterialsUp until now, weve been talking about only one polycarbonate, polycarbonate of bisphenol A.But theres another polycarbonate out there, that some of us look at all the time. In fact, someof us, like me, never look at anything without the help of this polycarbonate. This is thepolycarbonate that is used to make ultra-light eyeglass lenses. For people with really badeyesight, like me, if the lenses were made out of glass, they would be so thick that theyd betoo heavy to wear. I know. I used to have glass lenses. My glasses were so heavy that wearingthem gave me a headache. But this new polycarbonate changed all that. Not only is it a lotlighter than glass, but it has a much higher refractive index. That means it bends light morethan glass, so my glasses dont need to be nearly so thick.So what is this wonderful new polycarbonate? Its very different from polycarbonate ofbisphenol A. We make it by starting with this monomer:You can see that it has two allyl groups on the ends. These allyl groups have carbon-carbon double bonds in them. This means they can polymerize by free radical vinylpolymerization. Of course, there are two allyl groups on each monomer. The two allylgroups will become parts of different polymer chains. In this way, all the chains willbecome tied together to form a crosslinked material that looks like this:As you can see, the carbonate-containing groups (shown in blue) for the crosslinksbetween the polymer chains (shown in red). This crosslinking is makes the material very 4 Food Packaging Materialsstrong, so it wont break nearly as easily as glass will. This is really important for kidsglasses! If only this stuff had been invented when I was a kid!There is a fundamental difference in the two types of polycarbonate described here that Ishould point out. Polycarbonate of bisphenol A is a thermoplastic. This means it can bemolded when it is hot. But the polycarbonate used in eyeglasses is a thermoset.Thermosets do not melt, and they cant be remolded. They are used to make things thatneed to be really strong and heat resistant. For polyethylene at a glance, click here!Polyethylene is probably the polymer you see most in daily life. Polyethylene is the mostpopular plastic in the world. This is the polymer that makes grocery bags, shampoo bottles,childrens toys, and even bullet proof vests . For such a versatile material, it has a very simplestructure, the simplest of all commercial polymers. A molecule of polyethylene is nothingmore than a long chain of carbon atoms, with two hydrogen atoms attached to each carbonatom. Thats what the picture at the top of the page shows, but it might be easier to draw it likethe picture below, only with the chain of carbon atoms being many thousands of atoms long:Sometimes its a little more complicated. Sometimes some of the carbons, instead ofhaving hydrogens attached to them, will have long chains of polyethylene attached tothem. This is called branched, or low-density polyethylene, or LDPE. When there is nobranching, it is called linear polyethylene, or HDPE . Linear polyethylene is much stronger ...