Effects of Citric Acid on Structures and Properties of Thermoplastic Hydroxypropyl Amylomaize Starch Films

• Published in: Materials Vol. 12; no. 9; p. 1565
• Main Authors: Qin, Yang, Wang, Wentao, Zhang, Hui, Dai, Yangyong, Hou, Hanxue, Dong, Haizhou
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 13.05.2019; MDPI
• Subjects: Acids; biodegradable plastic film; Caustic soda; Citric acid; Copper; cross-linking; Crosslinking; Elongation; Extrusion; Glycerol; Humidity; hydroxypropyl amylomaize starch; Mechanical properties; Molecular interactions; Molecular structure; NMR; Nuclear magnetic resonance; Polyethylene; reactive extrusion; Software; Tensile strength; Viscosity; United States > US; China; citric acid; hydroxypropyl amylomaize starch; reactive extrusion; cross-linking; biodegradable plastic film
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma12091565

Hydroxypropyl amylomaize starch (HPAS) films were prepared by hot press. The effects of initial pH of HPAS on the mechanical properties, molecular interaction, structure, and cross-linking degree of the resultant films were investigated. A weak acidic condition was suitable for cross-linking of citric acid and HPAS by reactive extrusion. The film of HPAS with an initial pH of 5.66 had the maximum tensile strength of 7.20 MPa and elongation-at-break of 94.53%, and the weight average molecular weight of HPAS increased to 4.17 × 10 g/mol. An appropriate initial pH facilitated the formation of diester bonds between HPAS and citric acid during extrusion, but too low initial pH levels resulted in hydrolysis of starch molecules and reduced the mechanical properties.