Not processed sufficiently to satisfy specifications for a given grade. Scrap can be prepared to satisfy one grade but not another; but the general term "unprepared" refers to scrap not prepared at all, most of the time.

without preparation; not prepared for; "unprepared remarks"; "the shock was unprepared"; "our treaty makers approached their immensely difficult problems unprepared"- R.E.Danielson

To present participles which come from intransitive verbs, or are themselves employed as adjectives, to mark the absence of the activity, disposition, or condition implied by the participle;

not put in a state of preparedness; "the machinery was unprepared for the extra load"

lacking with intellectual equipment; "unprepared to stand on his own feet"