9010
We printed and tested 84 parts , in three polymer materials having relative density ranging from 0.06 to 0.23 .
 polymer materials, relative density
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:
 polymer materials, relative density