## 4 Conclusions  
Fused-deposition modelling was used to process Ultem 9085, a thermoplastic polymer which has recently attracted the interest of scientific and industrial communities thanks to its good properties such as excellent flame retardancy, low smoke generation, and high mechanical performances. In order to acquire a deeper knowledge of Ultem 9085, which is a promising candidate in many application fields, it was characterized in term of mechanical and thermal properties. Tensile and flexural tests were performed on samples with XY, XZ, and ZX building directions. XZ orientation showed the highest yield and ultimate tensile strengths, elastic modulus, and elongation at break; however, these properties were found not to be significantly different for samples with XY \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mechanical Property** & **Source** & **Sum of Squares** & **F Ratio** & \(p\)**-Value** \\ \hline \multirow{2}{*}{Flexural strength} & BG & 785.737 & \multirow{2}{*}{3.914} & \multirow{2}{*}{0.021} \\  & WG & 803.0275 & & \\ \hline \multirow{2}{*}{Elastic modulus} & BG & 1,346,911 & \multirow{2}{*}{17.018} & \multirow{2}{*}{\textless{}0.001} \\  & WG & 316,574.2 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: ANOVA test for flexural strength and modulus obtained after ageing treatments. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Mechanical Property** & **A** & **B** & **C** & **D** & **As Printed** \\ \hline Flexural strength [MPa] & 118.8 (7.7) a,b,c & 124.7 (5.3) c & 113.4 (1.7) a & 113.7 (13.3) a,b,c & 118.0 (0.3) b \\ Elastic modulus [MPa] & 2201(227) b & 2650 (199) c & 2030 (75) a & 1956(93) a & 2428 (17) b \\ Elongation at break [\%] & 7.5 (0.1) & 7.5 (0.1) & No break & No break & No break \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Mechanical properties of Ultem 9085 after different ageing treatment. Superscript letters indicate statistically homogeneous subsets ([PERSON]’s HSD test, \(\alpha\) = 0.05). orientation (with the exception of elastic modulus which was similar for the two kind of samples). On the contrary, ZX samples reported significantly lower tensile properties; this is due to the fact that the fracture of these samples is caused by debonding among layers, whose adhesion cannot withstand too high tensile loads. A similar trend was observed for flexural properties--XZ samples in fact showed the highest strength and modulus; however, these properties were significantly lower for both XY and ZX samples. These outcomes confirm the excellent mechanical properties of Ultem 9085 built according XZ orientation, and provide evidence that that the building direction has a significant effect on tensile and flexural properties. The effect of ageing treatments performed by varying the environmental conditions in term of maximum reached temperature and relative humidity on the flexural behavior of samples with XZ orientation (the most performance one) was also investigated. Warm storage, which involves the maintenance of samples at 100 \({}^{\circ}\)C and zero relative humidity for a long period, did not show a significant impact on mechanical properties of Ultem 9085. On the contrary, a sudden variation of temperature from 70 \({}^{\circ}\)C to \(-\)20 \({}^{\circ}\)C negatively affected the properties of the material under investigation, which showed a significant decreasing of both flexural strength and elastic modulus with respect to the as-printed samples. When the temperature variation was gradual, as with that experienced by Ultem 9085 during cyclic climate change, a significant improvement of flexural strength and modulus was observed. Ultem 9085 was conclusively found to be sensitive to a sudden variation of the temperature; however, maintenance of high temperature, or a progressive variation of temperature, did not seem to significantly affect the very good mechanical performances of this material.