Mechanical, thermal and physical properties of chitosan and chitin filled compatibilized polyamide-6/polypropylene composites

Abstract

Chitosan (CSN) is one of the natural fillers that offer various advantages due to its biodegradability, non-toxic and absorption properties. The presence of hydroxyl and amino group in chitosan molecules, which is a derivative obtained through alkaline deacetylation of chitin (CN), offers wide possibilities to be blended with other polymers to form new material with better properties. Polymer blending of polyamide-6 (PA6)/polypropylene (PP) incorporated with maleated polypropylene (MA-g-PP) as compatibilizer has been studied by many researchers. The present study investigates the performance of chitosan as filler incorporated into compatibilized PA6/PP blends. Throughout the study, the weight ratio of PA6/PP and compatibilizer was fixed at 70:30 weight percent of PA6/PP and 5 phr of MA-g-PP. All blends with different contents (0, 10, 20, 30 phr) of chitosan were compounded using co-rotating twin-screw extruder followed by injection moulding into test samples. Mechanical properties of the blends were studied through tensile, flexural and impact tests. It was found that the flexural strength and modulus were highest at 30 phr of chitosan. Since chitin is cheaper than chitosan and is also a biodegradable and non-toxic polymer, chitin was chosen to partially replace chitosan in the PA6/PP blends. Moreover, chitin contains amide group which is similar to PA6, and is expected to improve the composites properties. Results showed that tensile strength of PA6/PP/CSN/CN composites did not have significant difference with PA6/PP/CSN at 30 phr. However, the impact strength increased with increasing chitin content until it reached 20 phr. Furthermore, impact strength of mixed chitosan/chitin content is higher as compared to single fillers in the composites. The comparison between composites containing virgin chitosan and virgin chitin at 30 phr were made and results showed that the tensile strength, flexural strength and modulus, and impact strength of chitin composites were higher. Thermal analysis using thermogravimetry and differential scanning calorimetry showed that thermal stability of PA6/PP blends were not much affected with incorporation of chitosan or chitin. However, the incorporation of chitosan at 30 phr has increased the percentage of water absorption of blends to 66% with incorporation of chitosan at 30 phr which is in contrast with the addition of chitin. In conclusion there is no clear advantage of using chitosan over chitin or a mixture of both.