In a textbook I'm using, there's a brief explanation regarding phrasal verbs.
It states that one type of phrasal verb can be without an object in the sentence, and provides the example: "I'm going to be tied up in meetings all day".
Wouldn't "meetings" qualify as an object in this sentence?
If you wanted to give it an object, you could say 'He tied up a pig'; but 'tied up' has a different meaning there - different, but not unrelated. The speaker is - metaphorically - being tied up by the meetings.