Synergistic effects of β-cyclodextrin containing silicone oligomer on intumescent flame retardant polypropylene system

All-in-one bio-derived poly(L-lactic acid)-based composite with fire-resistance and smoke-suppression performance

The flammability of bio-derived poly(L-lactic acid) (PLA) greatly limits its application and eco-friendly multifunctional fire-fighting PLA-based composites are highly desired. In this work, a fully bio-based modified CS (C-CS) and commercially available eco-friendly ammonium polyphosphate (APP) were used as a synergistic flame retardant agent (C-CS/APP) to investigate its effects on fire-proofing performance and diverse properties of the PLA. The PLA/5%C-CS/5%APP composite exhibited excellent fire-resistant performance with anti-droplet, smoke-suppression and self-extinguishing property, and its limited oxygen index enhanced by 37 % (compared with neat PLA). This composite reached the highest V-0 fire safety rating, and its peak of heat release rate and total smoke production reduced by 26.5 % and 68.3 %, respectively. In addition, the char residue yield after the cone calorimeter test increased by 46 times in the composite, indicating an outstanding char-forming capacity. The condensed phase flame retardancy played a crucial role on the fire-fighting of this composite, that is, significantly enhanced char residue (as a physical barrier) blocked the heat exchange and O2 entry, and further suppressed the combustion reaction. Additionally, the PLA-based composite showed outstanding UV-absorption property, good anti-bacterial effect, and increased hydrophilicity and crystallizability.

Modified β-cyclodextrin microspheres towards the application in intumescent fire resistance and smoke-suppressing of bio-based poly(L-lactic acid)

In this work, the β-cyclodextrin (β-CD) was modified by a phosphazene compound to prepare a novel amorphous derivate (β-CDCP), which was combined with the ammonium polyphosphate (APP) as a synergistic flame retardant (FR) of the bio-based poly(L-lactic acid) (PLA). The effects of the APP/β-CDCP on the thermal stability, combustion behavior, pyrolysis process, fire resistance performance and crystallizability of the PLA were investigated comprehensively and in depth by thermogravimetric (TG) analysis, limited oxygen index (LOI) analysis, UL-94 test, cone calorimetry measurement, TG-infrared (TG-IR), scanning electron microscopy-energy dispersive spectrometer, Raman spectroscopy, pyrolysis-gas chromatography/mass spectrometry and differential scanning calorimetry. The PLA/5%APP/10%β-CDCP showed a highest LOI of 33.2 %, passed V-0 rating and exhibited self-extinguish phenomenon in the UL-94 test. Also, it presented a lowest peak of heat release rate, total heat release, peak of smoke production rate and total smoke release, and a highest char yield treated by cone calorimetry analysis. In addition, the 5%APP/10%β-CDCP shortened significantly crystallization time and enhanced crystallization rate of the PLA. Gas phase and intumescent condensed phase fire proofing mechanisms are proposed to elucidate enhanced fire resistance in this system in detail.

Cyclodextrins and Cyclodextrin Derivatives as Green Char Promoters in Flame Retardants Formulations for Polymeric Materials. A Review

Polymers are intrinsically flammable materials; hence, fire retardance (FR) is required in their most common applications (i.e., electronic and construction, to mention some). Recently, it has been reported that cyclodextrin (CD) and cyclodextrin derivatives are beginning to be introduced into Intumescent Fire Retardant (IFR) formulations in place of pentaerythritol, which is used in IFRs that are currently on the market. Since IFRs are of less environmental concern than their hazardous halogen containing counterparts, the use of natural origin compounds in IFRs provides a way to comply with green chemistry issues. BCD and BCD derivatives presence in IFR mixtures promotes a higher yield of blowing gases and char when polymeric materials undergo combustion. Both processes play important roles in intumescence. The key rule to obtain in insulating compact char is the good dispersion of the nanoparticles in the matrix, which can be achieved by functionalizing nanoparticles with BCD derivatives. Moreover, CD derivatives are attractive because of their nanosized structure and their ability to form inclusion complexes with many compounds used as FR components, reducing their release to the environment during their shelf life of FR items. Often, fire retardance performed by BCD and BCD derivatives accompanies other relevant properties, such as improved mechanical resistance, washability resistance, self healing ability, thermal conductivity, etc. The application of CD fire retardant additives in many polymers, such as poly(lactic acid), poly(propylene), poly(vinyl acetate), poly(methyl methacrylate), linear low density poly(ethylene), polyamides, and polyesters are comprehensively reviewed here.

Recent Advances in Bio-Based Flame Retardant Additives for Synthetic Polymeric Materials

It would be difficult to imagine how modern life across the globe would operate in the absence of synthetic polymers. Although these materials (mostly in the form of plastics) have revolutionized our daily lives, there are consequences to their use, one of these being their high levels of flammability. For this reason, research into the development of flame retardant (FR) additives for these materials is of tremendous importance. However, many of the FRs prepared are problematic due to their negative impacts on human health and the environment. Furthermore, their preparations are neither green nor sustainable since they require typical organic synthetic processes that rely on fossil fuels. Because of this, the need to develop more sustainable and non-toxic options is vital. Many research groups have turned their attention to preparing new bio-based FR additives for synthetic polymers. This review explores some of the recent examples made in this field.

New insight into the preparation of flame-retardant thermoplastic polyether ester utilizing β-cyclodextrin as a charring agent

The past decade has witnessed remarkable progress of the development and amelioration of thermoplastic polyether ester elastomer (TPEE), showing its promising wide-range utility. Herein we unraveled an unprecedented research to utilize β-cyclodextrin (β-CD) with perfect charring ability in TPEE in substitution of toxic halogen flame retardants. The TPEE/phosphorous–nitrogen flame retardants (P-N FR) (aluminum diethylphosphinate and melamine polyphosphate)/β-CD system was created and the flame retardance effects were determined using the limiting oxygen index (LOI) and the vertical burning test (UL94), while the charring effects of β-CD were measured by thermogravimetric analysis (TGA), laser Raman spectroscopy (LRS), and scanning electron microscopy (SEM). Besides, the mechanical properties and the morphology were tested by the universal testing machine and SEM. Results indicate that with 10 wt% of β-CD added to the TPEE/25 wt% P-N FR systems, the UL94 can reach to V-0 grade and the tensile strength of this blend was kept above 10 MPa, which can be applied in practice. To our delight, β-CD promoted the formation of stable and compact carbonaceous char, preventing the melt dripping and enhancing the properties and the charring mechanism was better studied by real-time Fourier transform infrared spectra. Being easy to construct, sustainable, and economic, the TPEE composite modified by β-CD and P-N FR is a reliable and widely applicable novel fire retardation material.

Influence of Aluminum Hydroxide and Expandable Graphite on the Flammability of Polyisocyanurate-Polyurethane Foams

The aim of this work was to verify the influence of expandable graphite (EG) and aluminum hydroxide (ATH) fillers on the flammability of polyisocyanurate-polyurethane (PIR). Limited oxygen index increased to 72.5 with an incorporation of 16 phr (parts per hundred of matrix) EG and 50 phr ATH into the matrix (total weight percent was 39.76%). Cone calorimetry was employed to study the flammability properties of these PIR/ATH/EG composites. Scanning electron microscopy analysis was conducted to study the char characteristics of the composites after the cone calorimetry tests. It was found ATH could effectively induce villi like particles, which made the intumescent char denser, on the surface of EG. The compact char layer could effectively impede the transport of bubbles and heat. ATH and EG accelerated the initial degradation and fluffy char was quickly generated on the surface. Thus, degradation products of the composite were slowed down and the diffusion of volatile combustible fragments to flame zone was delayed.