Preparation of Cast Metallic Foams with Irregular and Regular Inner Structure

The aim of this paper is to summarize the possibilities of foundry methods for the production of metallic foams. At present, there are a number of production technologies for this interesting material, to which increasing attention has been paid in recent years. What is unique about metallic foams is the combination of their physical and mechanical properties. As part of our research, we designed and verified four main methods of metallic foam production by the foundry technology, whose products are metallic foam castings with regular and irregular arrangements of internal cavities. All these methods use materials and processes commonly used in conventional foundry technologies. The main idea of the research is to highlight such technologies for the production of metallic foams that could be provided by manufacturing companies without the need to introduce changes in production. Moreover, foundry methods for the production of metallic foams have the unique advantage of being able to produce even complex shaped parts and can thus be competitive compared to today's established technologies, the output of which is usually only a semi-finished product for further processing. This fact was the main motivation for the research.

Study of Cellulose and Starch-Based Biodegradable Foam Production Technology as Enviromentally Packaging Materials

Biodegradable foam is an alternative to styrofoam packaging which is not environmental friendly and harmful to health. Various sources of starch are widely available in nature which can be used as raw material for making biodegradable foam. Several researchers found that many types of starch can be used as the main material for making biodegradable foam, including cassava starch, corn starch, sago starch, durian seed starch, jackfruit seed starch, avocado seed starch, and banana weevil starch. The production methods used from several studies that have been carried out are thermopressing, baking process, microwave assisted molding, and extrusion. Biodegradable foam based on starch is brittle, sensitive to water and requires additional treatment to increase strength, flexibility and resistance to water so that it can be used commercially. The purpose of this article is to provide information on the production of biodegradable foam from various types of starch and cellulose. Based on the results of the analysis, the characteristics of biodegradable foam using the baking process method and modified sago starch resulted in better water absorption values compared to other types of starch and production methods.

Hardly Flammable Polyurethane Foams with 1,3-Pyrimidine Ring and Boron Atoms

This work presents the results of research related to the determination of application possibilities of new oligoetherols with 1,3-pyrimidine rings and boron atoms in rigid polyurethane foam production. Oligoetherols were obtained from 1,3-bis(2-hydroxyethyl)uracil, boric acid, and ethylene carbonate. Their structure was determined by instrumental methods (IR, 1H-NMR and MALDI-ToF spectra) and the physicochemical and thermal properties were examined. Obtained oligoetherols were used for synthesis of polyurethane foams. Some properties of the foams, such as apparent density, water uptake, dimensions stability, thermal stability, compression strength, thermal conductivity, oxygen index, and horizontal burning were investigated. The introduction of boron atoms into the foam structure reduced their flammability, but unfortunately it had a negative effect on the water absorption of the obtained materials—the water absorption was higher compared to the boron-free foams. The obtained foams showed good thermal stability compared to classic, rigid polyurethane foams.

Properties of polyurethane foam with fourth-generation blowing agent

Climate change makes it imperative to use materials with minimum global warming potential. The fourth-generation blowing agent HCFO-1233zd-E is one of them. The use of HCFO allows the production of polyurethane foam with low thermal conductivity. Thermal conductivity, like other foam properties, depends not only on the density but also on the cellular structure of the foam. The cellular structure, in turn, depends on the technological parameters of foam production. A comparison of pouring and spray foams of the same low density has shown that the cellular structure of spray foam consists of cells with much less sizes than pouring foam. Due to the small size of cells, spray foam has a lower radiative constituent in the foam conductivity and, as a result, a lower overall thermal conductivity than pouring foam. The water absorption of spray foam, due to the fine cellular structure, also is lower than that of pouring foam. Pouring foam with bigger cells has higher compressive strength and modulus of elasticity in the foam rise direction. On the contrary, spray foam with a fine cellular structure has higher strength and modulus in the perpendicular direction. The effect of foam aging on thermal conductivity was also studied.

Experimental and computation assessment of thermomechanical effects during auxetic foam fabrication

Auxetic foams continue to interest researchers owing to their unique and enhanced properties. Existing studies attest to the importance of fabrication mechanisms and parameters. However, disparity in thermo-mechanical parameters has left much debate as to which factors dominate fabrication output quality. This paper provides experimental, computational, and statistical insights into the mechanisms that enable auxetic foams to be produced, using key parameters reported within the literature: porosity; heating time; and volumetric compression ratio. To advance the considerations on manufacturing parameter dominance, both study design and scale have been optimised to enable statistical inferences to be drawn. Whilst being unusual for a manufacturing domain, such additional analysis provides more conclusive evidence of auxetic properties and highlights the supremacy of volumetric compression ratio in predicting Poisson’s ratio outcomes in the manufacture process. Furthermore statistical results are exploited to formulate key recommendations for those wishing to maximise/optimise auxetic foam production.