Abstract
The flammability of the biodegradable plastic PLA limits its application in industrial fields with high flame-retardant requirements. This paper provides a novel strategy for constructing refractory and thermostable PLA composites using layered double hydroxides (LDHs) chemically modified with ammonium polyphosphate (APP). XRD, FT-IR, SEM-EDS, and TEM confirm that the goal of LDHs has been successfully prepared. The thermal stability and combustion behavior of PLA composites were evaluated by the thermogravimetric analysis (TGA) and cone calorimetry tests (CCT). The crystallization behavior and tensile performances were also examined. The results showed that the incorporation of 15 wt% MgAlY-APP-LDHs practically makes the PLA composites reach the UL-94 V-0 grade. There were 43% and 20% reduction in the PHRR and THR of PLA/15APP-LDHs respectively due to the catalytic effect of Y elements and barrier effects of LDHs, which was a major performance against fire hazards. Furthermore, the increase in crystallinity and the decrease in mechanical strength of PLA composites are attributed to the nucleation of LDHs. In short, this research introduces the production of multifunctional PLA composites through APP intercalation of LDHs, which are deemed as prospective candidates for the next generation of sustainable plastics products.
Highlights
The global plastics market is expected to grow at a rate of 5% per year
The results showed that the PHRR of the PP containing 20 wt% ammonium polyphosphate (APP)-layered double hydroxides (LDHs) and 2 wt% zinc borate (ZB) was significantly reduced by 58%
By comparing the X-Ray Diffraction (XRD) patterns of APP and LDHs, it can be found that no characteristic peaks of APP were observed in LDHs, which confirms that APP molecules were successfully inserted into the interlayer of LDHs
Summary
The global plastics market is expected to grow at a rate of 5% per year. The excessive use of petroleum-based plastics has caused the problem of “white pollution” and has seriously threatened the Earth’s ecological environment. [4–6], while the poor flame retardancy of PLA seriously restrains its applications in emerging fields such as electronic devices, automobiles, and building materials [7, 8]. To circumvent this problem, adding flame retardants to PLA is an effective strategy to combat fire risk [9–11]. The endothermic decomposition of metal-hydroxides can decrease the combustion performance of flammable materials and release water into the vapor phase to dilute the blaze [14] Their main disadvantages are low flameretardant efficiency and poor compatibility with common polymers. The thick layer of APP formed during combustion is separated from the polymer matrix, so we need to find new ways to balance the flame retardancy and other properties. LDHs were introduced into the PLA to improve its fire retardancy
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