Renewable lignin-based surfactant modified layered double hydroxide and its application in polypropylene as flame retardant and smoke suppression.

A novel and environmentally friendly lignin-based surfactant sodium lignosulfonate (SLS) modified layered double hydroxide (LDH) flame retardant (LDH-LS) was fabricated via co-precipitation method, and subsequently incorporated into polypropylene (PP) matrix to obtain the PP and LDH-LS composites (PP/LDH-LS) by melt blending method. The XRD, FT-IR and XPS results indicated that SLS had successfully modified LDH by adsorbing on the surface of the LDH nanosheet. The WCA and SEM results revealed that the hydrophobic property of LDH-LS had been evidently improved, and it displayed a more homogeneous dispersion than virgin LDH in the PP matrix. Furthermore, cone calorimetry tests (CCT) illustrated that the peak heat release rate (PHRR), total heat release (THR), and total smoke release (TSR) of PP/LDH-LS composites exhibited declines of 62.9%, 25.1%, and 43.3% compared with those of Neat PP, respectively. Besides, the PP/LDH-LS achieved a LOI value of 29.4% and a UL-94 V-0 rating, whereas the PP/LDH showed only a LOI value of 25.2% and a UL-94 V-2 rating at 20 wt% loading. These improvements of flame retardant properties can be attributed to that the well-dispersed LDH-LS and synergistic flame retardancy between LDH and SLS.

Fabrication of green alginate-based and layered double hydroxides flame retardant for enhancing the fire retardancy properties of polypropylene.

An efficient and bio-based alginate pillared hydrotalcite (SA@LDHs) was fabricated via calcination-reconstruction manner with sodium alginate (SA) and hydrotalcite (LDHs-C), and used as novel flame retardant for polypropylene (PP). The morphologies and combustion properties of SA@LDHs and its hybrid with PP composites (PP/SA@LDHs) had been characterized by SEM, TGA, cone calorimetry, LOI and UL-94 measurements. With 30 wt% loading, the SA@LDHs achieved a LOI value of 30.9 % and a UL-94 V-0 rating, whereas the LDHs-C exhibited only LOI value of 27.6 % and a UL-94 V-1 rating. The peak heat release rate, total heat release and total smoke production of PP/SA@LDHs were 260.8 kW m-2, 61.3 MJ m-2 and 8.2 m2, respectively, which presented declines of 69.2 %, 42.8 % and 32.2 % compared with those of Neat PP. These improvements could be attributed to the presence of the radical-trapping effect of SA, which leading to promote PP chains to participate in the carbonization process.