The ornamental design for plastic thermal barrier for use in constructing thermally insulated windows, doors and/or frames and the like, substantially as shown and described.
FIG. 1 is a perspective view of a plastic thermal barrier for use in
constructing thermally insulated windows, doors, frames and the like shown
fragmentarily to indicate indeterminate length;
FIG. 2 is a side view thereof;
FIG. 3 is a sectional view taken along line 3--3 of FIG. 2.