(07-10-2018, 12:01 PM)Highpower Wrote: So why is it that they say plastic straws can't be recycled?
They have been talking about doing away with plastic straws all together on the news for days now, in favor of paper straws or better yet, preferring that you don't use straws at all!
It's all in the shape. Because they are long and thin, they can pass through a typical plastic shredder nearly intact. Instead of having a bin full of nicely chopped plastic chips, you now have a mix of chips and straws. This means it won't melt evenly, and the non melted parts can clog the extruder. So, they screen out the bigger chunks, and even that doesn't catch all the straws. The tiny coffee stirrers are even worse.
Because of the shape, they are also harder to wash before shredding, meaning debris/waste can get mixed in with the plastic. It doesn't take much foreign material to ruin an entire batch of plastic, especially if it gets mixed in and put into the extruders. Lots of work to take them apart and clean the clogs.
I worked at a place that molded plastic parts for cars. They try to shred and reuse all the small trimmings, but there are some pieces that are a real pain to reuse.
Edit: most straws (as far as I know, anyway) are polypropylene. Same stuff as gallon milk jugs here in the US.
Full of ideas, but slow to produce parts