Tao Zhang

Bio: Tao Zhang is an academic researcher from Zhejiang University. The author has contributed to research in topics: Materials science & Medicine. The author has an hindex of 17, co-authored 40 publications receiving 818 citations. Previous affiliations of Tao Zhang include Zhejiang Sci-Tech University & Ningbo Institute of Technology, Zhejiang University.

Core–Shell Bioderived Flame Retardants Based on Chitosan/Alginate Coated Ammonia Polyphosphate for Enhancing Flame Retardancy of Polylactic Acid

Abstract: Bioderived flame retardants represent one class of the most promising sustainable additives for creating flame retardant polylactic acid (PLA) because of their marginal impact on the biodegradability of PLA. Ammonium polyphosphate (APP) has demonstrated high flame-retardant effectiveness in PLA but its flame-retardant efficiency remains unsatisfactory even if after modifications. Herein, we report the facile fabrication of core–shell bioderived flame retardants by using APP as the core, and the chitosan (CS)/alginate (AA) bilayer as the shell through self-assembly in aqueous solution. The resultant core–shell flame retardant, APP@CS@AA-nBL (where “BL” is a CS&AA bilayer and “n” denotes 1–3 BL), can endow PLA with improved flame retardancy without negatively affecting the thermal properties. The PLA containing 10 wt % APP@CS@AA-3BL shows the highest LOI value (30.6%) and achieves a UL94 V-0 rating in the vertical burning test. Meanwhile, the cone calorimetry results demonstrate that the peak of the heat release rate and total heat release are respectively decreased by 23% and 11% relative to the PLA bulk. Such enhanced flame retardancy is mainly due to the excellent char-forming capability of APP@CS@AA. Moreover, the inclusion of 10 wt % APP@CS@AA-3BL gives rise to ∼23% increase in the impact strength of PLA possibly because of their interfacial hydrogen-bonding interactions. This work provides a facile and green strategy for preparing highly effective bioderived flame retardants for PLA and thus is expected to expand the practical applications in industry.

Chitosan/Phytic Acid Polyelectrolyte Complex: A Green and Renewable Intumescent Flame Retardant System for Ethylene–Vinyl Acetate Copolymer

Abstract: We describe the preparation and characterization of a green and renewable polyelectrolyte complex (PEC) containing phosphorus, nitrogen and carbon elements, based on the ionic complexation between chitosan and phytic acid. Introduction of this PEC to ethylene–vinyl acetate copolymer (EVA) leads to an improvement of the flame retardancy. As for the EVA/PEC composites with 20.0 wt % of PEC (EVA/20PEC), the char residue at 600 °C is 12 wt % higher than that of the pristine EVA under nitrogen atmosphere. Compared to the pristine EVA, the peak heat release rate and total heat release of EVA/20PEC show 249 W g–1 and 5.6 kJ g–1 decreases, respectively. The char residue of EVA/20PEC is full and compact, demonstrating excellent intumescent effect. Introduction of this PEC also contributes to a slight increase of the Young’s modulus while maintains the excellent ductility. This work provides a new approach for the development of environmentally friendly intumescent flame retardant system.

Construction of flame retardant nanocoating on ramie fabric via layer-by-layer assembly of carbon nanotube and ammonium polyphosphate

Abstract: A new flame retardant nanocoating has been constructed by the alternate adsorption of polyelectrolyte amino-functionalized multiwall carbon nanotube (MWNT-NH2) and ammonium polyphosphate (APP) onto flexible and porous ramie fabric. Scanning electron microscopy indicates that the adsorbed carbon nanotube coating is a randomly oriented and overlapped network structure, which is a promising candidate for flame retardancy applications. Attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis confirm that the APP is successfully incorporated into the multilayers sequentially. Assessment of the thermal and flammability properties for the pristine and nanocoated ramie fabrics shows that the thermal stability, flame retardancy and residual char are enhanced as the concentration of MWNT-NH2 suspension and number of deposition cycles increases. The enhancements are mostly attributed to the barrier effect of intumescent network structure, which is composed of MWNT-NH2 and the absorbed APP.

Permeability, viscoelasticity, and flammability performances and their relationship to polymer nanocomposites

Abstract: Despite abundant studies on gas barrier, viscoelastic, and flammability properties of polymer nanocomposites, comprehensive understandings of these performances and their relationships are still lacking. We herein attempt to gain deep insights into the performances by creating several polymer nanocomposites by incorporating three types of nanoparticles, nanoclay (Clay), carbon nanotubes (CNTs), and reduced graphene nanoplates (RGO), into polypropylene (PP). The oxygen permeability, viscoelasticity, and flammability measurements demonstrate that RGO can lead to much more reduction in the gas permeability (by ∼73%) and flammability (peak heat release rate (PHRR) reduction by ∼78%), as well as a higher storage modulus and melt viscosity of polymer matrix relative to clay and CNTs at the same loading (1.0 wt %) due to its higher aspect ratio. Clay performs better than CNTs in terms of gas barrier property due to its lamellar structure while behaves worse than CNTs in terms of increasing the melt viscosity and reducing flammability of polymers. Most important, there is a nearly line correlation among these properties for all polymer nanocomposites despite some deviations.

Controlled Formation of Self-Extinguishing Intumescent Coating on Ramie Fabric via Layer-by-Layer Assembly

Abstract: Self-extinguishing multilayer coatings consisting of polyelectrolyte polyethylenimine (PEI) and ammonium polyphosphate (APP) have been constructed by the layer-by-layer assembly technique onto flexible and porous ramie fabric. Attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis directly confirmed that PEI and APP were successfully incorporated onto the surface of ramie fabric sequentially. Assessment of the thermal and flammability properties for the coated ramie fabrics showed that the char residue at temperatures ranging from 400 to 600 °C during thermogravimetric analysis (TGA) and the self-extinguishing ability during vertical flame test were significantly enhanced as compared with the pristine sample, which showed strong dependency on the number of deposited layers, especially on the concentration collocation of both polyelectrolytes. This work provided a simple but effective method for the controlled formation of self-extinguishing intumescent coa...

Layer-by-layer Nanoarchitectonics: Invention, Innovation, and Evolution

Abstract: Materials fabrication with nanoscale structural precision based on bottom-up-type self-assembly has become more important in various current disciplines in chemistry including materials chemistry, ...

Review on the Processing and Properties of Polymer Nanocomposites and Nanocoatings and Their Applications in the Packaging, Automotive and Solar Energy Fields.

Abstract: For the last decades, nanocomposites materials have been widely studied in the scientific literature as they provide substantial properties enhancements, even at low nanoparticles content. Their performance depends on a number of parameters but the nanoparticles dispersion and distribution state remains the key challenge in order to obtain the full nanocomposites’ potential in terms of, e.g., flame retardance, mechanical, barrier and thermal properties, etc., that would allow extending their use in the industry. While the amount of existing research and indeed review papers regarding the formulation of nanocomposites is already significant, after listing the most common applications, this review focuses more in-depth on the properties and materials of relevance in three target sectors: packaging, solar energy and automotive. In terms of advances in the processing of nanocomposites, this review discusses various enhancement technologies such as the use of ultrasounds for in-process nanoparticles dispersion. In the case of nanocoatings, it describes the different conventionally used processes as well as nanoparticles deposition by electro-hydrodynamic processing. All in all, this review gives the basics both in terms of composition and of processing aspects to reach optimal properties for using nanocomposites in the selected applications. As an outlook, up-to-date nanosafety issues are discussed.

Environmental performance of bio-based and biodegradable plastics: the road ahead

Abstract: Future plastic materials will be very different from those that are used today The increasing importance of sustainability promotes the development of bio-based and biodegradable polymers, sometimes misleadingly referred to as ‘bioplastics’ Because both terms imply “green” sources and “clean” removal, this paper aims at critically discussing the sometimes-conflicting terminology as well as renewable sources with a special focus on the degradation of these polymers in natural environments With regard to the former we review innovations in feedstock development (eg microalgae and food wastes) In terms of the latter, we highlight the effects that polymer structure, additives, and environmental variables have on plastic biodegradability We argue that the ‘biodegradable’ end-product does not necessarily degrade once emitted to the environment because chemical additives used to make them fit for purpose will increase the longevity In the future, this trend may continue as the plastics industry also is expected to be a major user of nanocomposites Overall, there is a need to assess the performance of polymer innovations in terms of their biodegradability especially under realistic waste management and environmental conditions, to avoid the unwanted release of plastic degradation products in receiving environments