How to stop my Lab chewing my kitchen floor?

I have recently started a new job. Before i started work i was at home with my puppy who is now 9 months most of the time. Since starting work she has started to chew my kitchen cushion floor. Everybody says that maybe now i should leave the door of her playpen open, but im afraid if i do it will more than just my kitchen floor she chews. Any suggestions on what i should do. My friend takes her out for 20Min's in the morning and i come home on my dinner and take her out for 20Min's so its not as though she is locked in her pen all day she still gets her exercises. Any suggestions would be fab.