8051
Hydrophobic asymmetric ultrafiltration PVDF membranes : an alternative separator for VFB with excellent stability .
 Chemical: PVDF
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: PVDF 
Answer:
 Chemical: PVDF