Effect of heat treatment temperature on properties of electrosprayed paperboard

Abstract

The purpose of this study was to investigate the effect of additional heat treatment on the properties of paperboard electrosprayed with poly(lactic acid) (PLA). For this study, paperboards electrosprayed with PLA at 1%, 2%, and 3% (w/v) were further heat‐treated at 170°C, 180°C, 190°C, and 200°C for 1 minute. Physical properties, such as basis weight, thickness, and colour of electrosprayed paperboards, were investigated. For mechanical properties, folding endurance and bursting strength of treated paperboard was tested. Water resistance property was observed through contact angle, and water absorption was monitored by Cobb test. In addition, water vapour transmission rate tests were also conducted. Surface characteristics were investigated using a scanning electron microscope and roughness tester. After heat treatment, PLA particles on the paperboard surface melted and formed a smoother continuous surface; this contributed to lower water contact angles and significantly lower water absorption. Furthermore, the higher the concentration of PLA, the better the water resistance. Moreover, heat treatment temperature between 180°C and 200°C could significantly improve the water vapour barrier and water resistance properties. Temperature and treatment time could not be further increased, as the electrosprayed paper substrate was damaged and became yellowish. In addition, for the mechanical properties, an increase in the heat treatment temperature improved the bursting strength; however, a reduction in folding endurance was observed, because the melted PLA particles were absorbed deeper into the paper structure and made the whole matrix more brittle.