The flame retarding mechanism of the novolac as char agent with the fire retardant containing phosphorous–nitrogen in thermoplastic poly(ether ester) elastomer system

Flame-Retardant Thermoplastic Polyether Ester/Aluminum Butylmethylphosphinate/Phenolphthalein Composites with Enhanced Mechanical Properties and Antidripping

Aluminum butylmethylphosphinate AiBMP as a flame retardant and phenolphthalein as a synergistic agent were applied in a thermoplastic polyester elastomer (TPEE)) in the current study. The thermal properties, flame retardancy, crystallization and mechanical properties of TPEE/AiMBP with or without phenolphthalein were investigated using various characterizations, including the limiting oxygen index (LOI), vertical burning test (UL 94), thermogravimetric analysis TG, differential scanning calorimetry, microcombustion calorimeter (MCC), scanning electron microscopy (SEM), and mechanical tests. The results revealed that AiBMP alone is an efficient flame retardant of TPEE. Adding 15 wt.% AiBMP increases the LOI value of TPEE from 20% to 36%. The formula TPEE-15 AiBMP passed the UL 94 V-0 rating with no dripping occurring. The MCC test shows that AiBMP depresses the heat release of TPEE. In comparison with pure TPEE, the heat release rate at peak temperature and the heat release capacity of TPEE-15AiBMP are reduced by 46.1% and 55.5%, respectively. With the phenolphthalein added, the formula TPEE/13AiBMP/2Ph shows a higher char yield at high temperatures (>600 °C), and the char layer is stronger and more condensed than TPEE-15AiBMP.The tensile strength and elongation at break values of TPEE-13AiBMP-2Ph are increased by 29.63% and 4.8% in comparison with TPEE-15AiBMP. The SEM morphology of the fracture surface of the sample shows that phenolphthalein acts as a plasticizer to improve the dispersion of AiBMP within the matrix. The good char charming ability of phenolphthalein itself and improved dispersion of AiBMP make the TPEE composites achieve both satisfying flame retardancy and high mechanical properties.

Preparation and thermal cross-linking mechanism of co-polyester fiber with flame retardancy and anti-dripping by in situ polymerization

Extensive research has been conducted on polyester flame retardants and anti-droplet modifications in recent years. The conventional methods used to improve the effectiveness of the anti-droplet modifications usually involve improving the melt fluidity and the combustion char formation through reactive cross-linking. However, these methods, while reducing the droplets, may produce more smoke. This study proposes a combustion cross-linking method which avoids the droplet and flame retardancy synergistic modification problem. Based on the flame retardancy of polyester, anti-droplet properties were realized using a collaborative cross – linking structure formed by a phosphorus – containing flame – retardant group and acid silicon solvent to achieve a flame retardant and anti-droplets result. The results show that the phosphorus–silicon copolyester presents an enhancement effect for flame retardancy, confirmed by obvious reductions in the peak value of heat release rate (78.4%) and total heat release (44.2%). Meanwhile, the total smoke release and smoke product rate of phosphorus–silicon copolyester are decreased by 45.1% and 41.5%, respectively. And the phosphorus–silicon copolyester has a high LOI value of 34.8 ± 0.1% and UL-94 is V-0 rating with superior anti-dripping performance. Flame retardancy index (FRI) of the copolyesters containing phosphorus–silica are up to 4.3093 (good flame retardancy). Nonisothermal differential scanning calorimetry (DSC) was performed for qualitative analysis of network formation by the aid of Cure Index (CI) dimensionless criterion. It was observed that the acidic silica led to Excellent cure situation. The TG-DSC, XPS, and FTIR results validate the thermal cross-linking ability of the copolymer due to the synergistic cross-linking effect between the self-cross-linking characteristic of the catalysed acidic silica sol containing the phosphorus flame retardant. The SEM-EDX and Raman results further verify the effectiveness of the condensed-phase flame-retardant mechanism. Phosphorus–silicon copolyester has good spinnability, flame retardancy and anti-droplets properties. Which provides a simple method for preparing polyester by using this combustion synergistic crosslinking effect to achieve flame retardant and anti-dripping modification of copolymers.

Scheme of proposed thermal cross-linking mechanism.

Intumescent Flame Retardant Mechanism of Lignosulfonate as a Char Forming Agent in Rigid Polyurethane Foam

Intumescent flame retardants (IFR) have been widely used to improve flame retardancy of rigid polyurethane (RPU) foams and the most commonly used char forming agent is pentaerythritol (PER). Lignosulfonate (LS) is a natural macromolecule with substantial aromatic structures and abundant hydroxyl groups, and carbon content higher than PER. The flame retardancy and its mechanism of LS as char forming agent instead of PER in IFR formulation were investigated by scanning electron microscopy, thermogravimetric analysis, limiting oxygen index testing and cone calorimeter test. The results showed LS as a char forming agent did not increase the density of RPU/LS foams. LOI value and char residue of RPU/LS foam were higher than RPU/PER and the mass loss of RPU/LS foam decreased 18%, suggesting enhanced thermal stability. CCT results showed LS as a char forming agent in IFR formulation effectively enhanced the flame retardancy of RPU foams with respect to PER. The flame retardancy mechanism showed RPU/LS foam presented a continuous and relatively compact char layer, acting as the effect of the flame retardant and heat insulation between gaseous and condensed phases. The efficiency of different LS ratio in IFR formulation as char forming agent was different, and the best flame retardancy and thermal stability was obtained at RPU/LS1.

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.

Themoxidative stability and char formation mechanism for the introduction of CNTs and MoS2 into halogen-free flame retarding TPEE

In this study, we give an insight into the char formation mechanism for the addition of CNTs and MoS₂ into halogen-free flame retarding thermoplastic poly(ether ester) elastomers (TPEE).

Surface modification of titanium substrate with a novel covalently-bound copolymer thin film for improving its platelet compatibility

Despite of its widely uses in various clinical applications, the titanium-based material still faces different challenges, such as hemocompatibility and anti-biofouling characteristics required in various situations. The objective of this investigation was to develop a novel surface modification strategy for titanium-based material to improve the platelet compatibility that is important in rigorous blood-contacting cardiovascular applications. In this work, a series of copolymers, which composed of novel 6-acryloyloxy hexyl phosphonic acid (AcrHPA) and sulfobetaine methacrylate (SBMA) was synthesized. The phosphonic acid group in these copolymers can impart covalent binding to the titanium substrate while the zwitterionic sulfobetaine functionality is considered being able to reduce the platelet adhesion and activation on the modified titanium substrate. NMR analyses suggested that copolymerization reaction is likely not an ideal statistical reaction but to add the monomers in a random order. Studies have shown that the composition of the monomers affected the surface characteristics and platelet compatibility of these covalent-bound AcrHPA-SBMA copolymers on titanium substrate. Contact angle analysis has shown the addition of SBMA can increase surface hydrophilicity of the spun-coated copolymers. In addition, AFM analyses have revealed that the surface roughness of the spun-coated copolymer layer were varied with the ratio of AcrHPA and SBMA. The most platelet compatible surface was noted on the one modified by the highest amount of SBMA added (i.e. 70 mol%) in copolymerization. In summary, the surface modification scheme presented here would be of potential as well as manufacturing process applicable for future development in blood-contacting titanium-based biomedical devices.

Synergistic effects of BHDB-IPC with AlPi/MCA on flame retarding TPEE

The deoxybenzoin-based copolyarylate BHDB-IPC with perfect charring ability was synthesized.