Characteristics of Lightweight Concrete Based on a Synthetic Polymer Foaming Agent

The components of foamed concrete have a significant effect on its properties. Protein-based foamed concrete is used much more often. This study aims to assess the properties of foamed concrete with a density of around 500, 700, 800 and 1000 kg/m3 formed by using a synthetic polymer-based foaming agent. The distribution of pores, wet and dry density and compressive strengths were evaluated. In addition, the creep deformations of foamed concrete with different densities were measured. The difference in density of up to 170 kg/m3 for the highest densities was obtained. Foamed concrete with higher densities (700 and 800 kg/m3) showed similar characteristics of pores, which were different from those of samples with a density of 500 kg/m3. Compressive strength equal to 5.9 ± 0.2, 5.1 ± 0.2, 3.8 ± 0.3 and 1.4 ± 0.2 MPa was obtained for foamed concrete with a density of 500, 700, 800 and 1000 kg/m3, respectively. The obtained compressive strengths were higher than those found in the literature for the foamed concrete with the same densities. With increasing density, smaller creep deformations were obtained. Creep deformations were 509, 495 and 455 με for samples with densities of around 500, 700 and 1000 kg/m3 respectively. Deformation under long-term loading took place up to 90 days, regardless of the density of the foamed concrete.

Current Research and Patents of Polymer Foaming

Background: Since the rapid development of polymers in the 1920’s, polymer products have become a necessary part of people's lives. Supercritical fluid technology was gradually introduced in this field. With the emergence of new technologies, methods, and equipment, the supercritical fluid technology has rapidly developed in the field of polymers and displayed a broad application perspective. Objective: The research progress of supercritical fluid-assisted polymer foaming, including equipment improvement, polymer composition ratio, and foaming process, and the influence of these processes on polymer foaming materials is reviewed here. Methods: Patents and research progress of supercritical fluid assisted polymer foams were reviewed. The advantages and disadvantages of various patents are analyzed in terms of cell structure, mechanical properties, surface quality, processing performance, and cost. Results: The foaming equipment and the manufacturing process of polymer foaming materials were retrospected, in order to improve the quality and application prospect of foaming composites. Conclusion: The preparation technology of supercritical fluid polymer foams has attracted wide attention. In recent years, patented technology has enabled us to use the supercritical fluid polymer foaming materials. There are some problems in the supercritical fluid foaming in terms of mechanical properties, cell structure, cell size, and processing technology, therefore, more equipment and patents are needed to solve these problems in the future.

Fabrication of PCL Scaffolds by Supercritical CO2 Foaming Based on the Combined Effects of Rheological and Crystallization Properties

Polycaprolactone (PCL) scaffolds have recently been developed via efficient and green supercritical carbon dioxide (scCO2) melt-state foaming. However, previously reported gas-foamed scaffolds sometimes showed insufficient interconnectivity or pore size for tissue engineering. In this study, we have correlated the thermal and rheological properties of PCL scaffolds with their porous morphology by studying four foamed samples with varied molecular weight (MW), and particularly aimed to clarify the required properties for the fabrication of scaffolds with favorable interconnected macropores. DSC and rheological tests indicate that samples show a delayed crystallization and enhanced complex viscosity with the increasing of MW. After foaming, scaffolds (27 kDa in weight-average molecular weight) show a favorable morphology (pore size = 70–180 μm, porosity = 90% and interconnectivity = 96%), where the lowest melt strength favors the generation of interconnected macropore, and the most rapid crystallization provides proper foamability. The scaffolds (27 kDa) also possess the highest Young’s modulus. More importantly, owing to the sufficient room and favorable material transportation provided by highly interconnected macropores, cells onto the optimized scaffolds (27 kDa) perform vigorous proliferation and superior adhesion and ingrowth, indicating its potential for regeneration applications. Furthermore, our findings provide new insights into the morphological control of porous scaffolds fabricated by scCO2 foaming, and are highly relevant to a broader community that is focusing on polymer foaming.