Sea-island Microstructure and Spontaneous Confinement Layer Formation in Polyamide 6/Polybutylene Terephthalate Films for Improved Laser Propulsion Efficiency

Laser ablation propulsion (LAP) represents a promising approach for nano-satellite propulsion, owing to its high exhaust velocity and the possibility of remote thrust generation. Polymeric materials are particularly attractive as LAP targets due to their low ablation thresholds and possible high laser impulse coupling coefficients. In this study, polymeric films based on immiscible blends of polyamide 6 (PA6) and polybutylene terephthalate (PBT) are investigated with the aim of enhancing impulse generation through confined laser ablation. The intrinsic immiscibility of PA6 and PBT gives rise to a sea-island microstructure which is exploited to promote the spontaneous formation of a confinement layer during laser irradiation. The blend morphology and optical absorption properties were characterized by scanning electron microscopy and UV-Vis spectroscopy, respectively, while impulse generation under vacuum conditions was quantified using a custom ballistic pendulum. By tuning the PBT concentration, an optimal composition was identified at which the onset of confined ablation coincides with surface layer detachment and a maximum in the generated impulse. These results demonstrate that the sea-island microstructure plays a critical role in enabling spontaneous confinement effects, offering a viable strategy for the design of advanced polymeric targets for laser ablation propulsion.