Open to two or more interpretations; or of uncertain nature or significance; or (often) intended to mislead. Synonyms: ambiguous; equivocal. Context examples:
Many of the polypropylene sleeves are less than 2 mil. Many of the sleeves being sold on the internet and by hobby and comic shops are very flimsy and range from .5 mil to 2 mil. The majority of commercially-available polypropylene sleeves are 1 to 1.5 mil. Our polyethylene sleeves are 2 mil and 3 mil, respectively. In more chemistry-speak, propylene (CH3CH:CH2) is is a sub-stratum of ethylene. Ethylene is the purest form of the base chemical and thus the purer better of the two.
The major difference between these pipes is basically the difference in material and there properties. PVC, CPVC, UPVC and HDPE are non metalic pipes. They are made from thermoplastic materials. These fall under the category of Plastic pipework. Both pipes and fittings are available in these materials.