Effect of processing variables on the thermal and physical properties of poly(L-lactide) spun bond fabrics

In this paper, the influence of the take-up velocity (Vt–u) of fibers on the molecular ordering and ά – α form transition of polylactide (PLA) non-woven fabrics during their manufacturing by spun-bonding is described. Non-woven samples were studied by wide-angle X-ray diffraction, differential scanning calorimetry and Fourier transform infrared spectroscopy. In addition, the physical and mechanical properties of the non-woven fabrics were determined. The results are discussed in terms of the structural changes of the PLA and the meso-phase content during the spun-bonded non-woven fabric forming process. This technological process includes preliminary molecular ordering of the PLA fibers in a downstream spinning block and crystallization on a calender system at a temperature higher than the glass transition. The molecular ordering of the investigated PLA fabric samples under different technological conditions was observed as follows: creation of the meso-phase and a disorder-to-order phase transition (ά to α form) during heating to approximately 110℃ and an increase in the degree of crystallinity for take-up velocities higher than 1400 m/min. The structural changes of the PLA explain the observed changes in the physical and mechanical properties of the non-woven fabrics obtained under different technological conditions.