Open‐Pore Biodegradable Foams Prepared via Gas Foaming and Microparticulate Templating

Abstract

Open-pore biodegradable foams with controlled porous architectures were prepared by combining gas foaming and microparticulate templating. Microparticulate composites of poly(epsilon-caprolactone) (PCL) and micrometric sodium chloride particles (NaCl), in concentrations ranging from 70/30 to 20/80 wt.-% of PCL/NaCl were melt-mixed and gas-foamed using carbon dioxide as physical blowing agent. The effects of microparticle concentration, foaming temperature, and pressure drop rate on foam microstructure were surveyed and related to the viscoelastic properties of the polymer/microparticle composite melt. Results showed that foams with open-pore networks can be obtained and that porosity, pore size, and interconnectivity may be finely modulated by optimizing the processing parameters. Furthermore, the ability to obtain a spatial gradient of porosity embossed within the three-dimensional polymer structure was exploited by using a heterogeneous microparticle filling. Results indicated that by foaming composites with microparticle concentration gradients, it was also possible to control the porosity and pore-size spatial distribution of the open-pore PCL foams.

Novel 3D porous multi-phase composite scaffolds based on PCL, thermoplastic zein and ha prepared via supercritical CO2 foaming for bone regeneration

“…Furthermore, we observed the increase of the pore size when T F increased from 80°C (Figures 3c and d) to 100°C (Figures 3e and f), as a consequence of the further decrease of the stiffness of the two polymers [27,28]. The higher magnifications of the PCL-TZ and PCL-TZ-HA 20 composite scaffolds prepared at T F = 100°C, reported in the insets of Figures 3e and f, respectively, also showed the presence of pore interconnectivity (black arrows).…”

“…(Figures 3a and b). The PCL-TZ-HA 20 composite was characterized, hence, by smaller pores (compare the high magnification insets reported in Figures 3a and b), mainly because of the enhanced stiffness of the polymeric matrix [27,28]. Conversely, by performing foaming at T F > T m , the pores…”

“…Looking at the TZ phase, a smaller porosity was observed (not shown), due to the higher stiffness of this polymer, with respect to the PCL [21]. It is also important to point out that all of the T F selected for the design of the scaffolds were significantly lower than the degradation temperature of TZ (323.9°C, Figure 2 and Table 2) and, therefore, the foaming experiments should allow for the and pore size distribution of porous materials prepared by CO 2 foaming [27,28]. In our previously reported work, we showed that, by increasing the amount of NaCl particles (5 µm in size) within PCL, it was possible to obtain PCL foams characterized by a lower mean pores size and a narrower pore size distribution [27].…”

“…By considering the main importance of T F on the final properties of porous material prepared via the gas foaming process [21,[25][26][27], we limited our investigation on the effect of different T F on the final morphology, porosity and pore size distribution of the scaffolds. Other processing parameters have been fixed as: saturation pressure equal to 150 MPa and pressure drop rate equal to 700 bar/s.…”

Carbon dioxide‐induced crystallization in poly(L‐lactic acid) and its effect on foam morphologies

“…Using CO 2 to prepare biodegradable polymer foams has been done for poly(lactic-co-glycolic acid), 24 -26 poly(ε-caprolactone), 27,28 poly(L-lactic acid) (PLLA), 11,26,27 poly(glycolic acid), 26,27 PLA, 29 PLA/silk composites 30 and PLA/layered silicate nanocomposites. 31,32 Studies have also demonstrated that CO 2 is able to depress T g and T m , 33,34 and induce crystallization 11 in PLLA.…”