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In a further printing study carried out at atmospheric pressure in a nitrogen atmosphere , it was also demonstrated that any oxidation of the polymer layers during printing , did not significantly influence the mechanical properties of the resultant printed parts .
 pressure, nitrogen, oxidation, polymer, mechanical properties
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:
 pressure, nitrogen, oxidation, polymer, mechanical properties