Characterization of polypropylene composites using sludge waste from the natural rubber latex industry as reinforcing filler

In the natural rubber latex industries, a huge amount of sludge waste is produced in different processes, which creates potential for use as reinforcing filler in plastic composites. The present work aimed to investigate the effects of sludge waste generated from the manufacturing process of fresh latex pond (FLSF) and concentrated latex processing (CLSF) on the thermal, mechanical, and physical properties of polypropylene (PP) composites. Composite samples were produced using a twin-screw extruder and a compression molding machine. From experiments, particle size analysis showed that FLSF had a smaller particle size than CLSF. For both the reinforcing fillers with increasing addition from 30 to 50 wt%, crystallinity degrees increased by about 3.30% and 7.80% for the composites with FLSF and CLSF, respectively. The strength of tension and flexure in the PP composites reduced continuously with an increase of the sludge waste contents in a range of 30-70 wt%, but the modulus from tension and flexure, hardness, and water absorption (WA) increased. The PP composites produced from FLSF displayed superior strength, modulus, hardness, and WA than those produced from CLSF. Further, the morphological, mechanical, and physical properties of the PP-sludge composites were improved with addition of maleic anhydride-grafted polypropylene. The aforementioned results showed that latex sludge waste could be used as an effective filler in plastic composites.

Automated summary

This study aimed to investigate the effects of sludge waste from the natural rubber latex industries on the properties of polypropylene composites. The results showed that the addition of sludge waste decreased the strength but increased the modulus, hardness, and water absorption of the composites. Composite samples made from fresh latex sludge displayed superior performance due to their smaller particle size.