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There currently exists the requirement to improve reproducibility and mechanical properties of SLS Nylon parts for RRapid MManufacturing (RM). In order to achieve this, further fundamental research is needed and this paper addresses this need by investigating effects of potential sources of the lack of reproducibility (i.e. build procedure/parameters and powder blend) and reports effects in relation to crystal structure, microstructure, chemical structure (molecular weight) and mechanical properties.Different and γ p crystal forms were identified and related to the un-molten particle cores and the molten/crystallised regions of the microstructure. The melt point of the γ p form varied depending on processing conditions but the γ v remained principally constant. Observable differences were also present when comparing the microstructure of the parts. Molecular weight of parts was significantly higher than virgin powder but used powder (powder already held at elevated temperature) also showed an increase in molecular weight. This was related to improved elongation at break of parts built from the used powder, consistent with previous studies. Tensile strength showed some increase with parameters selected for improved strength but Young's modulus values were broadly similar.

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A cross-linked nonlinear optical urethane polymer is prepared from 4-[ (2-hydroxyethyl)sulfonyl] -4'-[N,N-bis(2-hydroxyethyl)amino] azobenzene (1) and toluene diisocyanate by simultaneously corona poling and cross-linking at 145 °C for only 30 min. This material shows very promising results as NLO material: SHG measurements show a resonantly enhanced <¿33 value of 60 pm/V at 1064 nm 1 day after poling and a 34% decrease after 800 h at 70 °C. Moreover, electrooptic measurements on contact poled samples at 175 °C result in a value of the pockels constant r33 of 12.3 pm/V. Poling at 190 °C results in a decrease of less than 40 % after 100 h at 1506 C. Additional measurements show a linear interrelation between the electrooptic and the pyroelectric constant, as well as between the electrooptic constant and the dielectric polarization.

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