Peculiar micro and nano cell morphology of PBT/PTFE nanofibrillated composite foams of supercritical CO2 foaming induced by in-situ formed 3D PTFE nanofiber networks

Stable nanoscale sea-island structure of biobased polyamide 56/poly (butylene adipate-co-terephthalate) blends compatibilized by interfacial hyperbranched structure: Toward biobased polymer blends with ultrahigh toughness

Developing biobased materials is a considerably effective approach to save fossil resources and reduce emissions. Biobased polyamide 56 (PA56) is an excellent engineering material, but it has low toughness. Herein, to enhance the toughness of PA56, an ultra-tough biodegradable material, i.e., poly (butylene adipate-co-terephthalate) (PBAT) was introduced into PA56. Moreover, a self-synthesized epoxy-terminated hyperbranched polyester (EHBP) was used to improve the compatibility of the blended materials. The results of differential scanning calorimetry and Fourier-transform infrared spectroscopy indicated that the epoxide group of EHBP could react with PA56 and PBAT to form a block-like polymer structure and limit the crystallization behavior of the blends. The scanning electron microscopy results show that the addition of EHBP considerably reduced the dispersed-phase size in the blends, forming a nanoscale island structure. Moreover, the hydrogen bonds formed between EHBP and PA56/PBAT enhanced the intermolecular interaction between the two materials. Thus, PA56 blends with ultrahigh toughness were successfully prepared. The prepared PA56/PBAT/EHBP blend exhibited a notch impact strength of 20.71 kJ/m2 and a breaking elongation of 38.3 %, which represent increases of 427.3 % and 252.8 %, respectively, compared with those of pure PA56. Thus, the proposed method is suitable for toughening PA56 and broadening its applications.

Preparing low-Density microcellular polystyrene foam by in-Situ fibrillated PTFE and supramolecular nucleator TMC-300 in the presence of sc-CO2

A method using in-situ fibrillated polytetrafluoroethylene (PTFE) and octamethylenedicarboxylicdibenzoylhydrazide (TMC-300) supramolecular nucleator was presented to prepare low density polystyrene foams. This study used a torque rheometer in the molten compound preparation of PS/fibrillated-PTFE/TMC-300 composites. Scanning electron microscopy showed in-situ fibrillated polytetrafluoroethylene in Polystyrene melt and a nanofiber network with high aspect ratio. The formation of nanometer-sized fiber networks improved the melt viscoelasticity of matrices which promoted cell nucleation. As the results demonstrated, low-density foams with 11 μm average cell size were obtained using Polystyrene. The self-assembly nucleating agent TMC-300 was then introduced to the composite materials. TMC-300 and polytetrafluoroethylene as a composite cell nucleating agent were used in Polystyrene foams. Meanwhile, their nucleating efficiency was investigated. TMC-300 completed self-assembly in Polystyrene and served as composite nucleating agent in combination with polytetrafluoroethylene. Compared with the sample PS/PTFE-0.5, the average cell size of the sample PS/PTFE-0.5/TMC-2 had a reduction rate of 28.16% from 12.18 μm to 8.75 μm. The cell density increased by an order of magnitude. The composite nucleating agent was successful in controlling Polystyrene foam cell morphology, thus leading to the preparation of low-density Polystyrene microporous foams.

ScCO2-assisted fabrication and compressive property of poly (lactic acid) foam reinforced by in-situ polytetrafluoroethylene fibrils

As an effective alternative for petrochemical-based polymers, bio-based poly (lactic acid) (PLA) foam has been anticipated to alleviate enormous environmental pollution caused by microplastics. However, some difficulties involved in PLA foaming process due to the inherently poor melt strength and crystallization properties. In this context, a small amount of polytetrafluoroethylene (PTFE) was incorporated into PLA matrix to solve the aforementioned issues. Scanning electron microscopy measurement exhibited that PTFE fibrils and their physical networks were formed in molten PLA after blending. Due to these PTFE networks, approximately 2 orders of magnitudes increment in the storage modulus and more than 20% improvement in crystallinity of PLA were obtained. Diverse PLA samples were successfully foamed by a cost-effective, green and supercritical CO₂-assisted foaming method. The PLA/PTFE foam with the PTFE content of 5 wt% (PLA/PTFE5) possessed the smallest pore size (9.51 μm) and the highest pore density (2.60 × 10⁸ pores/cm³). In addition, the average specific compressive strength of PLA/PTFE5 foam was enhanced 30% in comparison with that of pure PLA foam. Overall, this study could provide a prospective strategy for developing bioderived and biodegradable polymer foams with controllable pore structures and high compression property.