Foaming window for preparation of microcellular rigid polyurethanes using supercritical carbon dioxide as blowing agent

A novel and green method for recycling of waste feather for down via flash explosion with supercritical carbon dioxide

Millions of tons of feather are produced worldwide each year and considered as a solid waste owing to technical or cost constraints to provide valuable functional characteristics. In this study, a novel and ecofriendly method to recycle waste feather and obtain a type of explosion down via flash explosion with a supercritical fluid of carbon dioxide (SCF-CO₂) was developed for the first time. The effects of flash explosion parameters on the structures and properties of feather were explored by orthogonal experiments. A mechanism involving two-step procedures for the developed SCF-CO₂ flash explosion is proposed. The obtained results indicate that reinforcements of flash explosion conditions, particularly the system pressure, were readily conducive to transfer the original feather to a soft down with an improved separation ratio, as well as easily weaken or break hydrogen and disulfide bonds associated in feather macromolecules. Moreover, efficient modifications of the physical characteristics, structures and surface morphologies of the waste feather were obtained by the SCF flash explosion to produce a uniform, slender and fibrous explosion down, as demonstrated by scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis. Further tests on the SCF explosion down treated at 70.0 °C at 15.0 MPa for 30.0 min and at 90.0 °C at 20.0 MPa for 20.0 min showed remarkable enhancements in warmth retention along with comparable thermal degradation nature, as well as enhanced softness, down-proof, and other service properties in comparison to the original feather. The SCF-CO₂ flash explosion is a promising approach with environment-friendly characteristics to obtain high efficiency and quality of the explosion down by recycling of waste feather.

A Brief Introduction to the Polyurethanes According to the Principles of Green Chemistry

Polyurethanes are most often called “green” when they contain natural, renewable additives in their network or chemical structure, such as mono- and polysaccharides, oils (mainly vegetable oils), polyphenols (e.g., lignins, tannins), or various compounds derived from agro-waste white biotechnology (Principle 7). This usually results in these polyurethanes obtained from less hazardous substrates (Principle 4). Appropriate modification of polyurethanes makes them susceptible to degradation, and the use of appropriate processes allows for their recycling (Principle 10). However, this fulfilment of other principles also predisposes them to be green. As in the production of other polymer materials, the synthesis of polyurethanes is carried out with the use of catalysts (such as biocatalysts) (Principle 9) with full control of the course of the reaction (Principle 11), which allows maximization of the atomic economy (Principle 2) and an increase in energy efficiency (Principle 6) while minimizing the risk of production waste (Principle 1). Moreover, traditional substrates in the synthesis of polyurethanes can be replaced with less toxic ones (e.g., in non-isocyanate polyurethanes), which, at the same time, leads to a non-toxic product (Principle 3, Principle 5). In general, there is no need for blocking compounds to provide intermediates in the synthesis of polyurethanes (Principle 8). Reasonable storage of substrates, their transport, and the synthesis of polyurethanes guarantee the safety and the prevention of uncontrolled reactions (Principle 12). This publication is a summary of the achievements of scientists and technologists who are constantly working to create ideal polyurethanes that do not pollute the environment, and their synthesis and use are consistent with the principles of sustainable economy.

Experimental and numerical study of the polyurethane foaming process using high-pressure CO2

A simulation of simultaneous bubble nucleation and growth was performed for polyurethane/CO2 physical foaming process. The single-factor and comprehensive effects of viscoelastic properties, Henry’s constant, CO2 diffusion coefficient and surface tension on the cell morphology were numerically analyzed. The results show that the cell density of PU foam ( N0) increases and its average cell diameter ( Dv) reduces with increased Henry’s constant and slower gas diffusion. Both N0 and Dv reduces with the curing degree ( α). In addition, the effects of α and foaming conditions on the cell structure were experimentally investigated. With an increase of α at foamable range, Dv decreases continuously and N0 increases first and then declines. With increasing saturation pressure and depressurization rate or decreasing temperature, N0 increases and Dv reduces. There is an intrinsic correlation between the simulated and experimental variables, and the results of the simulation and experiment are generally consistent.

Foaming of PLA Composites by Supercritical Fluid-Assisted Processes: A Review

Polylactic acid (PLA) is a well-known and commercially available biopolymer that can be produced from different sources. Its different characteristics generated a great deal of interest in various industrial fields. Besides, its use as a polymer matrix for foam production has increased in recent years. With the rise of technologies that seek to reduce the negative environmental impact of processes, chemical foaming agents are being substituted by physical agents, primarily supercritical fluids (SCFs). Currently, the mass production of low-density PLA foams with a uniform cell morphology using SCFs as blowing agents is a challenge. This is mainly due to the low melt strength of PLA and its slow crystallization kinetics. Among the different options to improve the PLA characteristics, compounding it with different types of fillers has great potential. This strategy does not only have foaming advantages, but can also improve the performances of the final composites, regardless of the implemented foaming process, i.e., batch, injection molding, and extrusion. In addition, the operating conditions and the characteristics of the fillers, such as their size, shape factor, and surface chemistry, play an important role in the final foam morphology. This article proposes a critical review on the different SCF-assisted processes and effects of operating conditions and fillers on foaming of PLA composites.

Practical Modification of Tannic Acid Polyether Demulsifier and Its Highly Efficient Demulsification for Water-in-Aging Crude Oil Emulsions

In order to break the aging crude oil (WACO) emulsion of the offshore platform more effectively, a highly active isocyanate, polyaryl polymethylene isocyanate (PAPI), was selected to modify the pilot-scale tannic acid demulsifier. In the addition of PAPI, its molecular weight and viscosity dramatically increased, while its relative solubility, hydroxyl number, and cloud point exhibited an opposite direction, showing an increase in hydrophobicity. After adding the above modified demulsifier, a remarkably improved water removal of WACO emulsion accompanied by a notable reduction of the water content in the oil phase monitored by the Karl Fischer method was observed. Demulsification on the offshore platform demonstrated that the best water removal was achieved when the proportion of PAPI is 1.5 wt %. Its demulsification efficiency reached 95.7%, which was 25.6% higher than the 76.2% of unmodified demulsifier. In addition, a positive correlation between viscoelasticity of emulsion and demulsification performance was found by only adjusting the parameters of the rheometer. This method may be utilized to characterize the demulsification performance by any rotary rheometer. The pilot-scale demulsification experiment demonstrated that the water removal can reach 98.14 vol % and residual water content was only 0.55 vol %. These results further confirmed the excellent demulsification performance of the modified demulsifier toward the WACO emulsion in production.