In this study, the effects of nanoclay on the mechanical properties of poly(methylmethacrylate) (PMMA)/clay nanocomposite foams are investigated. Intercalated PMMA/clay nanocomposites have been prepared through a solvent co-precipitation method. PMMA/clay nanocomposites with only 0.5 wt% of well-dispersed montmorillonite nanoclay showed considerable improvement of mechanical properties; specifically in elastic modulus, tensile strength, and elongation at break. However, with an increased load of clay in the nanocomposite, the mechanical properties decreased due to the agglomeration of excessive nanoclay. Microcellular foams have been processed with PMMA/clay nanocomposite material using a subcritical gas foaming method. When a short foaming time is used, the increased amount of nanoclay induced a greater amount of heterogeneous nucleation during the foaming process and therefore decreased the density of the foam. In contrast, when a longer foaming time is used, foam density increased with a larger nanoclay load due to the higher diffusivity coefficient of CO2 blowing agent. Nanoclay, as a nucleation agent and reinforcement filler, changed the foaming behavior and mechanical properties of the PMMA microcellular foams. The microcellular foams made of PMMA/clay nanocomposite with 0.5 wt% exhibited an optimized mechanical response under tensile experiments. It is observed that the mechanical properties of nanocomposite foams are greatly related to the mechanical properties of unfoamed material and foam density. The nanoclay dispersion quality is a very important factor for the mechanical properties of both foamed and unfoamed polymer/clay nanocomposites.

Geniposide (GE) is the extraction and purification of iridoid glycosides from the Gardenia jasminoides Ellis, which is a promising anti-inflammatory drug, but its mechanism of actions on rheumatoid arthritis (RA) has not been clarified. This study investigated the molecular mechanism behind GE reduced the high permeability of fibroblast-like synoviocytes (FLSs) derived from SD rats with adjuvant arthritis (AA), with the aims of observing the action of GE in AA rats and exploring new therapeutic strategies for RA treatment. The CCK-8 method was used to detect FLSs proliferation. The pro-inflammatory cytokines levels and anti-inflammatory cytokines levels in FLSs were determined by ELISA kits. FLSs permeability assay was performed on Transwell. Immunofluorescence was used to assay the arrangement and morphology of F-actin. The expression of the key molecules related to FLSs permeability (RhoA, p-p38MAPK, NF-κB p-p65 and F-actin) was detected by western blotting. After treatment with lipopolysaccharide (LPS), the proliferation and the permeability of the cells increased significantly (all P < 0.05). The expression of RhoA, p-p38MAPK, NF-κB p-p65 and F-actin in FLSs was higher compared with the control group, and F-actin was redistributed, with the formation of additional stress fibers. But, these conditions were moderated after treatment with GE. We demonstrated that the treatment of different concentrations of GE (25, 50, and 100 μg/mL) had a significant inhibitory effect on the proliferation and permeability of FLSs in vitro. Furthermore, the levels of interleukin (IL)-1β and IL-17 secreted by FLSs were decreased in different doses of GE groups, and the levels of anti-inflammatory cytokines (IL-4, TGF-β1) were increased. Under treatment with GE, low expression of RhoA downregulated expression of p-p38MAPK, NF-κB p-p65, and F-actin while compared with control group, and restored the hyperpermeability of FLSs due to LPS treatment. Taken together, GE might play its anti-inflammatory and immunoregulatory effects via regulating the relative equilibrium of pro-inflammatory cytokines and anti-inflammatory cytokines. GE attenuated the hyperpermeability of FLSs. The down-regulation of the conduction of RhoA/p38MAPK/NF-κB/F-actin signal may play a critical role in the mechanisms of GE on RA. GE could be an effective therapeutic agent for the treatment of RA.

In this study, the effect of processing parameters on the cellular morphologies and mechanical properties of PMMA microcellular foams is investigated. Microcellular closed cell Poly(methyl-methacrylate) (PMMA) foams were prepared using a two stage batch process method. The foam structure was controlled by altering the processing parameters such as foaming temperature, foaming time and saturation pressure. The foam morphologies were characterized in terms of the average cell size, cell density and foam density. Elastic modulus, tensile strength and elongation at break were studied as functions of the different foaming parameters. The mechanical properties were found to be greatly affected by the foaming parameters and vary with changing the cell morphologies. The experimental results were compared with existing analytical models to validate them and to predict the mechanical properties of microcellular polymeric PMMA foams prepared with different processing parameters. A constitutive equation for the nonlinear elastic behavior of polymeric microcellular foams was developed based on the Maxwell viscoelastic model. The results of this work can help designers optimize the foam processing parameters and achieve desired foam morphology and mechanical properties.

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