Size Effect of Layered Double Hydroxide Platelets on the Crystallization Behavior of Isotactic Polypropylene

[Image: see text] Layered double hydroxide (LDH) platelets with nanosized and microsized level were synthesized and used as fillers in an isotactic polypropylene (PP) matrix. The nucleation and crystallization behavior of PP/LDH composites (denoted as 1-PPLx and 2-PPLx for composites containing nanosized and microsized LDH, respectively; x represents the mass percentage of LDH) was investigated by differential scanning calorimetry and polarized optical microscopy techniques. It is found that the crystallization temperature of PP/LDH composites is largely enhanced and the half crystallization time is reduced remarkably relative to pure PP, especially for 2-PPLx composite. The 2-PPLx composite exhibits stronger heterogeneous nucleating ability and faster crystallization rate than 1-PPLx samples with the same LDH loading. In addition, the crystallized PP/LDH composites possess significantly enhanced thermal stability, gas barrier, and flame-retardant properties relative to neat PP, which would show a broad application prospect in engineering plastics and packing industry.