what is the thermoplastic used to make drink bottles
and what is the name of the industrial process of making plastic bottles.
could be anything - look for little signs like PET or PE or PU
I think Ive seen all three on plastic bottles.
Did you know you can make polymers out of plant material as well! did ya?
did ya?
There is no one thing that is plastic, it can be made out of
any number of materials, the first plastic was make out of a petroleum
base, but plastic bottles are made out of polymerized cellulose. Which
means the cellulose molecules are rearranged by a chemical proces so the
molecules will stretch & leave places where other substance can be added
to make the molecule longer still. A very very long molecule can usually
be reshaped & then hold that shape. It is shipped to the factory that is going to use it in small flat disks so they can be reheated & all the plastic used will be the same temperature. A big chunk of plastic will be different temperatures when heated, plastic has a small resistence to heat or else it wouldn't melt at the factory, but if shipped in large blocke the outside would be cooler than the inside unless it was pelletized & only used on site where the bottling process takes place. The plastized cellulose melts at a much lower temperature than other materials are melted at the plant & then an amount is placed in the neck of a mold & compressed air to make the bottle & the excess is cut off. The bottles are then sent to an oven so they cool slowly, when cooled they are filled with whatever liquid.
normally bottles are blow molded.
Nice link here, tells everything.
http://madehow.com/Volume-1/Soda-Bottle.html
This link gives the codes referring to what resin is used it the bottles
http://plastics.ca/news/default.php?id=200
One of the polymers used for drinking bottles is polyethylene
terephthalate (PET). the process of manufacturing is blow molding
Polyethylene terephthalate (aka PET, PETE or the obsolete PETP
or PET-P) is a thermoplastic polymer resin of the polyester family that is
produced by the chemical industry & is used in synthetic fibers; beverage,
food & other liquid containers; thermoforming applications; & engineering
resins often in combination with glass fiber. It is one of the most
important raw materials used in man-made fibers.
Depending on its processing & thermal history, it may exist both as an amorphous (transparent) & as a semi-crystalline (opaque & white) material. Its monomer can be synthesized by the esterification reaction between terephthalic acid & ethylene glycol with water as a byproduct, or the transesterification reaction between ethylene glycol & dimethyl terephthalate with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with ethylene glycol as the byproduct (the ethylene glycol is recycled in production). The majority of the world is PET production is for synthetic fibers (in excess of 60%) with bottle production accounting for around 30% of global demand. In discussing textile applications, PET is generally referred to as simply ''polyester'' while ''PET'' is used most often to refer to packaging applications. PET is hygroscopic, meaning that it naturally absorbs water from its surroundings. However, when this 'damp' PET is then heated a chemical reaction known as hydrolysis takes place between the water & the PET which reduces its molecular weight (IV) & its physical properties. This means that before the resin can be processed in a molding machine, as much moisture as possible must be removed from the resin. This is achieved through the use of a desiccant or dryers before the PET is fed in the processing equipment. Inside the dryer, hot dry air is pumped into the bottom of the hopper containing the resin so that it flows up through the pellets removing moisture on its way. The hot wet air leaves the top of the hopper & is first run through an after-cooler, because it is easier to remove moisture from cold air than hot air. The resulting cool wet air is then passed through a desiccant bed. Finally the cool dry air leaving the desiccant bed is re-heated in a process heater & sent back through the same processes in a closed loop. Typically residual moisture levels in the resin must be less than 40 ppm before processing. Dryer residence time should not be shorter than about four hours. This is because drying the material in less than 4 hours would require a temperature above 160 °C, at which level hydrolysis would begin inside the pellets before they could be dried out.
I beleive its polyprophelyne. (sp?)
polyeurethane made by blow moulding
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