1640
However , the high viscosity of high-performance polymers causes complications during the FFF process and reduces the final print quality .
 viscosity, polymers, FFF, print quality
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 viscosity, polymers, FFF, print quality