Lips, P.A.M. Erratum - Gas foaming of segmented poly(ester amide) films
Lips, P.A.M., Velthoen, I.W., Dijkstra, P.J., Wessling, M. and Feijen, J
Polymer, 46, 12737-12737
Biodegradable segmented poly(ester amide)s, based on dimethyl adipate, 1,4-butanediol and N,N0-1,2-ethanediyl-bis[6-hydroxyhexanamide], with two distinct melting transitions were gas foamed using carbon dioxide (CO2). Polymer ﬁlms were saturated with CO2 at 50 bar for 6 h after which the pressure was released. The samples were immersed in octane at the desired temperature after which foaming started immediately. Just above the lower melt transition the polymers retain adequate mechanical properties and dimensional stability, while the chain mobility increased sufﬁciently to nucleate and expand gas cells during the foaming process. In this way semi-crystalline poly(esteramide)s can be gas foamed below the ﬂow temperature. Two poly(ester amide)s with 25 mol% (PEA2,5-25) and 50 mol% (PEA2,5-50) of bisamide segment content were foamed at 70 and 105 8C, respectively. The storage modulus (G 0) of both pure polymers at the onset foaming temperature is 50–60 MPa. Closed-cell foams were obtained with a maximum porosity of w90%. The average pore size of PEA2,5-25 ranges from 77 to 99 mm. In contrast, the average pore size of PEA2,5-50 is in between 2 and 4 mm and can be increased to 100 mm by lowering the CO2 saturation pressure to 20 bar. The porosity of PEA2,5-50 foams using this saturation pressure decreased to 70%.