Accepted: generally approved; generally agreed upon; not subject to dispute. Acceptable: worthy of acceptance; satisfactory; adequate for the purpose.

accepted is the past tense... acceptable is whether somthing is appropriate or not.

It is the same word but different form .Accept is to acknowledge , approve of ,find valid , accepted is the passiv form of the verb accept . The request is accepted .. ( means approved by another part and in this form it is already approved .) acceptable is the adjective of the verb to accept . The request is acceptable . ( means can be accepted ,not necessarily accepted yet , but has the potential to be accepted .