This study investigated the discoloration of polyamide-12, its elasticity and surface roughness in dependence of different storage media and artificial aging. Discoloration and surface roughness were also examined for PMMA specimens serving as a control.
Method:
A polyamide-12 (Valplast) was tested and compared with a self-cured acrylic resin (Palapress). 50 Polyamide-12 and 40 PMMA specimens were fabricated each measuring 40 x 10 x 2 mm. Discoloration in different storage media was measured using the CIE L*a*b* classification system. Changes in elasticity of artificial aging were measured with the three-point bending test, calculating the modulus of elasticity. In order to assess the roughness of the samples in various storage media a surface roughness test (Ra) was used. The results have been statistically analyzed (p=0.05).
Result:
The polyamide-12 showed statistically significant discoloration in red wine and coffee (p<0.05). The results for the PMMA specimens were not statistically different regardless of the storage media or the submersion period (p>0.05). Elastic modulus of polyamide-12 was not affected by thermocycling. The comparison of averages after thermocycling did not lead to any statistically significant differences (p>0.81). However dry specimens showed significantly decreased elasticity. The Ra values for polyamide-12 and PMMA showed no statistically significant differences between the two materials.
Conclusion:
Polyamide-12 is less resistant to staining than PMMA. Elasticity of polyamide-12 has increased after thermocycling. Surface and structure of polyamide-12 is more susceptible to storage conditions than PMMA.