A model for the molecular motion of a polymer melt under the impact of a vibration force field was developed. From complicated theory deduction, an expression of the relaxation time and dynamic apparent viscosity were obtained. The effect of a vibration frequency and amplitude on the melt's dynamic apparent viscosity is explained in terms of shear-thinning and untie-tangle criteria. The model is supplemented by a calculation sample and experiment, which show that dynamic apparent viscosity of a melt will tend to decrease as the vibration frequency or amplitude increases.
Research on the preparation of starch‐based degradable foams by adding simple raw materials and using simple processes meets the requirements of modern society and market demand. Water is the most common raw material in daily life, its triple transformation is easy to achieve, and it has an important effect on many aspects of the starch foaming process. This paper presents the research results on the preparation of starch‐based foaming materials using water as an important raw material, summarizing the mechanism of the action of solid–liquid gaseous water in the plasticization, foaming, hydrophobic, and swelling processes. Water vapor fumigation of starch materials uses high temperatures to induce the inversion (or dehydration) of the hydroxyl groups distributed on the surface, reducing the water sensitivity of the starch foam surface. Finally, the development trend is analyzed and foreseen, in order to provide new ideas for the development of low‐cost methods to prepare degradable and environmentally friendly packaging materials.
Novel graphitic carbon nitride quantum dots (g-C3N5-dots) were synthesized by an alkali-assisted hydrothermal method, having great potential applications in bioimaging and biological sensing.
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