It seems that you know little about modern China. Only trusting Western media wont give you a true and fair view.
I dont know if you did any research on PET`s Chinese directors, these guys are leading hands in Chinese environmental science industry. Their professional opinions are highly appreciated by the government.
Hotcopper is an investment forum so I dont want to get too deep with politics, just a hint: their government is very firm and steady on environmental protection and this wont change unless there is a full war between China and US. PET have many years of opportunity ahead for its development in China.
Just like Political Correctness (Race / Feminist etc.) in the West,there are certain topics which are sensitive in China (sovereignty and integrity), I dont think PET directors are dumb enough to get themselves plunged into that kind of trouble. So rest assured.
In all, please focus on the company`s performance, not "political risk".