Phosphorylated poly(vinyl alcohol) surface coatings as intumescent flame inhibitor for polymer matrix composites

Applications of poly(vinyl alcohol) (PVOH) are largely limited due to its poor flame resistance. In this work, organosolubility, and flame resistance are imparted to PVOH through green chemical transformation using dichloroacetic acid (DCAA). Unlike the conventional solvent-based strategies, PVOH was modified by simply mixing it with DCAA and heating the mixture without employing any additional reagents/catalysts/solvents. This resulted in the formation of a random copolymer, poly(vinyl alcohol-co-vinyl dichloroacetate), which was not soluble in water but was soluble in organic solvents such as acetone, methanol, and dimethylsulfoxide. Furthermore, the copolymer was inherently self-extinguishing, and did not melt drip or show glowing combustion. Additionally, dummy currency notes coated with this copolymer displayed exceptional self-extinguishing and non-glowing properties when removed from the flame, proving the copolymer's suitability for flame-retardant sizing/coating applications. 

Facile chemical modification of poly(vinyl alcohol) to an organosoluble, flame‐retardant copolymer using dichloroacetic acid

Resveratrol/tannic acid-poly(vinyl alcohol) (RETA-PVA) blends have been prepared by compression molding using poly(vinyl alcohol), tannic acid and resveratrol as raw materials. The effects of different resveratrol/tannic acid ratios on the flammability of RETA-PVA blends have been studied. The flammability of the RETA-PVA blends was assessed using cone calorimetry, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results indicate that RETA-PVA molecules occur through hydrogen bonding and RETA-PVA blends are amorphous. The glass transition temperature for RETA-PVA-2 is the highest among all blends and the peak of heat release rate and smoke production rate for RETA-PVA is 38.4% and 43.9% lower than that for PVA, respectively. With the addition of resveratrol, the residual amount of RETA-PVA after complete combustion is greatly increased, to 30 times that for PVA, indicating that RETA-PVA blends display excellent flame retardant properties. 

/pdf/outstanding-flame-retardancy-for-poly-vinyl-alcohol-achieved-1fgrla2k.pdf

Outstanding flame retardancy for poly(vinyl alcohol) achieved using a resveratrol/tannic acid complex


 The understanding of the mechanical indentation on a curved specimen (e.g., microspheres and microfibers) is of paramount importance in the characterization of curved micro-structured materials, but there has been no reliable theoretical method to evaluate the mechanical behavior of nanoindentation on a microsphere. This article reports a computational study on the instrumented nanoindentation of elastic-plastic microsphere materials via finite element simulation. The finite element analyses indicate that all loading curves are parabolic curves and the loading curve for different materials can be calculated from one single indentation. The results demonstrate that the Oliver-Pharr formula is unsuitable for calculating the elastic modulus of nanoindentation involving cured surfaces. The surface of the test specimen of a microsphere requires prepolishing to achieve accurate results of indentation on a micro-spherical material. This study provides new insight into the establishment of nanoindentation models that can effectively be used to simulate the mechanical behavior of a microsphere.

/pdf/finite-element-modeling-of-nanoindentation-on-an-elastic-cbqbzmyxae.pdf

Hongzhou Li

Papers

Outstanding flame retardancy for poly(vinyl alcohol) achieved using a resveratrol/tannic acid complex

Finite element modeling of nanoindentation on an elastic-plastic microsphere