Thermal stabilization of polyamide 11 by phenolic antioxidants

Effect of Antioxidants on Thermo-Oxidative Stability and Aging of Bio-Based PA56T and Fast Characterization of Anti-Oxidation Performance

Bio-based polyamide 56T (PA56T) is a new type of bio-based polyamide regarded as a promising material for sustainable solutions. The stabilization of PA56T compounded with Irganox 1098, Doverphos S9228, or SH3368 was studied by using a rotational rheometer and a circulating air oven at 150 °C. The thermal-oxidative aging resulted in an increase of the yellow color index of the PA56T/GF composites, which due to the carbonyl group as a chromophore group, continuously formatted during the aging process. After 10 days of aging, the mechanical properties and dynamic mechanical properties increase due to the molecular cross-linking and annealing effects. When the aging time is beyond 20 days, the degradation of molecular chain segments dominates, and the mechanical properties of PA56T/GF deteriorate continuously. The addition of antioxidants only slowed this effect and did not change the process of thermal-oxidative aging, which destroys the molecular chain. The results from both methods are consistent after a series of characterizations by FTIR, XRD, and so on. In the case of samples without lubricant, the rotational rheometer has the benefit of being less time-consuming than the accelerated aging experiment.

Hindered phenolic antioxidant passivation of black phosphorus affords air stability and free radical quenching

As an antioxidant, hindered phenol scavenges free radicals. Due to the oxidative degradation of black phosphorus (BP) in the presence of water and oxygen, free radical quenching of hindered phenol antioxidants can solve this issue and improve the environmental stability and flame retardant efficiency of BP. Herein, hydroxyl-modified BP (BP-OH) with active groups on the surface was obtained by hydroxylation, and then the hindered phenol antioxidant was grafted onto the surface of BP-OH through an isophorone diisocyanate bridging covalent reaction to obtain hindered phenol-modified BP (BP-HPL). The fire hazard of thermoplastic polyurethane (TPU) can be significantly reduced by introducing BP-HPL into TPU. Adding 2 wt% BP-HPL can reduce the heat release rate and total heat release values of TPU by 49.9% and 49.0%, respectively. In addition, the reductions in smoke volume and carbon monoxide production were also significant. Compared with BP-OH, the environmental stability of BP-HPL is significantly improved. This work provides a reference for the application of BP in the field of fire safety and simultaneously achieves the improvement of the environmental stability and flame retardant performance of BP.

Effect of neutralizers and silicone softeners on phenolic yellowing phenomenon of OBA treated cotton knitted fabric

Phenolic yellowing is a complex physicochemical phenomenon of cotton, especially for white and pastel-colored fabrics. This study tried to analyze the effect of neutralizers and silicone softeners on this. Three types of neutralizers of different chemical characteristics (acetic acid, citric acid, and commercial complex acid) were used to achieve core neutralization whereas two unlike ionic nature of silicone softeners (cationic & non-ionic) for the finishing process used. The acetic acid and nonionic softener treated fabric gives the maximum CIE (International Commission on Illumination) whiteness index value of 151 while citric acid and cationic softener have the least rating of 140.93 with a similar chemical dosage of 1.5 g/l by immediate testing. However, after repeated testing for one-month conditioning in atmospheric conditions, complex acid, and nonionic softener treated samples exhibited the maximum whiteness index of 145.86; on the other hand, citric acid and cationic softener treated one had the least rating of 125.85. Moreover, fabric core p^H, reading was found to be 6.68, 6.15 & 5.13 for acetic acid, citric acid, and complex acid through immediate testing. After one month of conditioning, the values were 7.2, 6.61, and 5.25, respectively. Finally, a maximum phenolic yellowing rating of 4–5 was found with complex acid & nonionic softener in contrast poor rating of 2 with acetic acid & cationic softener for immediate testing. Storage of the samples has a significant impact on phenolic yellowing for all types of chemical concentrations. Lightfastness rating was found identical for all samples while bursting strength had a very negligible impact, Fourier transform infrared (FT-IR) spectroscopy also revealed the presence of noticeable chemical functional groups.