| 摘要 |
Unique transparent plastic (preferably though not necessarily polypropylene) articles that can be tailored to become opaque when exposed to a sufficiently high temperature and which returns to substantially the same transparency level upon cooling are provided. Such formulations include polymeric constituents that exhibit melting temperatures well below that for the majority clarified polypropylene, and thus which appear to become amorphous upon exposure to temperatures above such a lower melting temperature, thereby affecting the crystalline formation of the clarified polypropylene to the extent that opacity dominates the appearance thereof. Such lower melting temperature polymeric constituents include species such as low melt flow (up to 10) metallocene polyethylene and/or low density polyethylene, both of which exhibit melting temperatures of from about 60 to about 100° C., well below the typical polypropylene melting temperatures of roughly about 150° C. for homopolymer and about 165° for typical random copolymer. Preferably, as well, the melt flow for the polypropylene may be anywhere from about 1 to about 20, with the most preferable formulation comprising polyethylene and polypropylene components exhibiting similar melt flow properties (e.g., with a difference of at most 5 units) for better mixing results. Methods of producing such temperature sensitive transparent polypropylene formulations and articles are also encompassed within this invention.
|
