I am an art student at a college in NY, and am doing research for an
industrial design problem.

I intend to make a new spray bottle entirely out of one type of
plastic. My questions has a few different parts.

Currently, the body of spray bottles (or atomizers) is made out of
HDPE (High Density Polyethylene) which is the recyclable category (2).
The head of the spray bottles appears to be made out of a different
type of plastic which is unrecyclable.

QUESTION 1::: Is it possible to create the head of the spray bottle out of HDPE,
or conversely, the body out of the same material as the head is
currently made out of?

Secondly, all spray bottle have one metal spring in them to control
the trigger mechanism.

Through brief research there are die springs made from polyurethene
plastics (a foam plastic), but it would be better if there was not
this second type of plastic, since it would defeat the purpose.

QUESTION 2::: Is there a way to design a plastic spring that will not wear down
or break? Or is there currently a type of coil spring on the market
made from harder plastic?

> Or is there currently a type of coil spring 
> on the market made from harder plastic?

Slinky
http://www.poof-slinky.com/catalog/slinkytoys/catalog.asp?action=catv&catid=33

Best regards,

Omnivorous-GA

Yes, but a slinky has no compresion strength. It want to be
compressed, therefore providing no pressure for a trigger type device.
Thanks, though.

Jerskinen --

I suggested the Slinky because whatever plastic they are using for
that product obviously can be molded to a specific form -- and clearly
doesn't fatigue easily.

Best regards,

Omnivorous-GA

The spring should not be a problem.
 
Critical issue may be cost of material which can be used to make a nozzle 
vs cheaper materials, perhaps with fillers, normally used for the body.

 Try this
SEARCH TERMS: precision molding, injection molding

and then call some manufacturers. This is specialised engineering knowhow
which is not (probably) obtainable via $12 search on the internet.

Hedgie