I'm not sure it's for regulating the the flow. I think it may be there to prevent someone from easily replacing the contents with, say, water.
Plastic bottles are mostly recyclable
Most plastic bottles are a mix of new and recycled plastic.
they are better for enviroment because they last longer than plastic and are not thrown away as aften as plastic bottles
Most recycled plastic bottles are recycled into... plastic bottles, especially PET plastic, the one with the Number 1 in the triangle. Other kinds of plastic bottles can be again made into similar plastic bottles, or they can be "downcycled", that is, combined with other plastics to make things like garbage bins and garden furniture.
Well, plastic is made from used plastic bottles so I guess that they want to recycle.
Milk bottles have clouded plastic because that type of plastic is stronger than others.
Plastic bottles are produced by blow molding.
recycled plastic
how can we regulate the plastics use
Their are hundreds of use for a PLASTIC BOTTLES like Art and making flowers out of cut up PLASTIC BOTTLES. If you want to know how to make flowers out of PLASTIC BOTTLES look on YouTube.com
plastic bottles, plastic is every where!
Certain plastic bottles can be recycled and make other plastic items, so saving them from landfill.