A New Promising Nucleating Agent for Polymer Foaming: Applications of Ordered Mesoporous Silica Particles in Polymethyl Methacrylate Supercritical Carbon Dioxide Microcellular Foaming

Effect of Organic Cage Nucleating Agent Structure on Nucleating Efficiency and the Structure-Property Relationship

Three types of organic cage compounds, namely, cucurbit[6]uril (Q[6]), hemicucurbit[6]uril (HQ[6]), and β-cyclodextrin (BC), with different cavity structures as heterogeneous nucleation agents were selected for a polypropylene (PP) foaming injection molding process. The experimental results showed that Q[6] with a "natural" cavity structure possessed the best nucleation efficiency of these three cage compounds. The nucleation mechanism of organic cage compounds was explored through classical nucleation theory, molecular structure, and in situ visual injection molding analysis.

Cellulose Nanostructure-Based Biodegradable Nanocomposite Foams: A Brief Overview on the Recent Advancements and Perspectives

The interest in designing new environmentally friendly materials has led to the development of biodegradable foams as a potential substitute to most currently used fossil fuel-derived polymer foams. Despite the possibility of developing biodegradable and environmentally friendly polymer foams, the challenge of foaming biopolymers still persists as they have very low melt strength and viscosity as well as low crystallisation kinetics. Studies have shown that the incorporation of cellulose nanostructure (CN) particles into biopolymers can enhance the foamability of these materials. In addition, the final properties and performance of the foamed products can be improved with the addition of these nanoparticles. They not only aid in foamability but also act as nucleating agents by controlling the morphological properties of the foamed material. Here, we provide a critical and accessible overview of the influence of CN particles on the properties of biodegradable foams; in particular, their rheological, thermal, mechanical, and flammability and thermal insulating properties and biodegradability.

Nanocellular Polymers: The Challenge of Creating Cells in the Nanoscale

The evolution of technology means that increasingly better materials are needed. It is well known that as a result of their interesting properties, nanocellular polymers perform better than microcellular ones. For this reason, the investigation on nanocellular materials is nowadays a very topical issue. In this paper, the different approaches for the production of these materials in our laboratory are explained, and results obtained by using polymethylmethacrylate (PMMA) are shown. Homogeneous nucleation has been studied by using raw PMMA, while two different systems were used for heterogeneous nucleation; adding nanoparticles to the system and using nanostructured polymers as solid precursors for foaming. The effects of the different parameters of the production process (gas dissolution foaming process) have been evaluated for all systems being possible to establish a comparison between the materials produced by different approaches. Moreover, the limitations and future work to optimise the materials produced are also discussed.

A new promising nucleating agent for polymer foaming: effects of hollow molecular-sieve particles on polypropylene supercritical CO2 microcellular foaming

Because polypropylene (PP) foam normally exhibits nonuniform cell size and cracked cellular structure, a narrow cell-size distribution and a well-defined morphology are always the focus of PP foaming technology. In this work, hollow molecular-sieve (MS) particles were applied as a potential nucleating agent in supercritical carbon dioxide (scCO2) foaming of PP. It was observed that the addition of MS particles largely narrowed the cell-size distribution. The resultant PP/MS foams exhibited significant concurrent enhancement in their cell density and mechanical properties: the cell density increased remarkably, by approximately 10 times, and the tensile strength increased from 6.1 MPa to 12.6 MPa. The hollow-structure MS particles resulted in a higher heterogeneous nucleation efficiency in the PP foaming process. We believe that the trapping of CO2 in the hollow holes of MS particles largely increased the solubility CO2 in PP and a number of gas cavities were formed. The existence of gas cavities reduced the energy barrier of heterogeneous nucleation, favoring the formation of a well-defined cellular structure. Additionally, the regular-hexagon shape of the cells might endow the PP foam with better mechanical properties compared with a circular cell shape.