Determination of mass attenuation coefficient of polylactic acid using gamma densitometry in 50-1000 keV energy range

Abstract Polylactic acid (PLA) is a biodegradable organic acid of polymeric chain that has as chemical structure the monomer C3H4O2 and it is one of the most used materials in rapid prototyping among 3D printers. Due to the ease of manufacturing PLA parts and because of its low atomic number, PLA can be used as holder to radiation source and detectors to establish fixed geometries in experiments using gamma radiation, hence the importance in knowing more about PLA characteristics. In this way, the novelty of this paper is to determine the mass attenuation coefficient of 3D printed PLA samples using gamma densitometry. A mathematical model was developed using MCNPX code and consisted of a PLA sample, a NaI(Tl) detector and gamma rays of 661.6 keV as radiation source (narrow beam). The mathematical model was experimentally validated using the same geometry and a lead collimator. Besides that, PLA weight fractions and density were also determined in order to use this information as input data in the MCNPX code. The obtained mass attenuation coefficients were in good agreement with the NIST theoretical reference value, presenting relative errors of 0.99% (MCNPX) and 1.66% (experimental). The proposed methodology was repeated replacing PLA for aluminum samples and comparing its results with NIST. In addition, the mass attenuation coefficient for some polymers was calculated using this model aiming to validate the geometry developed with MCNPX code.