Poly( l-lactide)/nano-structured carbon composites: Conductivity, thermal properties, crystallization, and biodegradation

• Published in: Polymer (Guilford) Vol. 48; no. 14; pp. 4213 - 4225
• Main Authors: Tsuji, Hideto, Kawashima, Yoshio, Takikawa, Hirofumi, Tanaka, Saburo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 29.06.2007; Elsevier
• Subjects: Applied sciences; Composites; Exact sciences and technology; Forms of application and semi-finished materials; Nano-structured carbons; Poly(lactic acid); Polylactide; Polymer industry, paints, wood; Technology of polymers; Nano-structured carbons; Polylactide; Poly(lactic acid); Biological properties; Optically active polymer; Biodegradability; Softening point; Carbon nanotubes; Thermal stability; Transformation temperature; Nanocomposite; Carbon black; Electrical properties; Filled polymers; Crystallization; Experimental study; Glass transition temperature; Heat of transformation; Lactic acid polymer; Singlewalled nanotube; Concentration effect; Enzymatic digestion; Fullerenes; Electric resistivity; Filler; Comparative study
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2007.05.040

The effects of nano-structured carbon fillers [fullerene C 60, single wall carbon nanotube (SWCNT), carbon nanohorn (CNH), carbon nanoballoon (CNB), and ketjenblack (KB)] and conventional carbon fillers [conductive grade and graphitized carbon black (CB)] on conductivity (resistance), thermal properties, crystallization, and proteinase K-catalyzed enzymatic degradation of poly( l-lactide) [i.e., poly( l-lactic acid) (PLLA)] films were investigated. Even at low filler concentrations such as 1 wt%, the addition of SWCNT effectively decreased the resistivity of PLLA film compared with that of conventional CB, and PLLA–SWCNT film with filler concentration of 10 wt% attained the resistivity lower than 100 Ω cm. The crystallization of PLLA further decreased the resistivity of films. The addition of carbon fillers, except for C 60 and CNB at 5 wt%, lowered the glass transition temperature, whereas the addition of carbon fillers, excluding C 60, elevated softening temperatures, if an appropriate filler concentration was selected. On heating from room temperature, cold crystallization temperature was determined mainly by the molecular weight of PLLA, whereas on cooling from the melt, the carbon fillers, excluding KB, elevated the cold crystallization temperature, reflecting the effectiveness of most of the carbon fillers as nucleating agents. Despite the nucleating effects, the addition of carbon fillers decreased the enthalpy of cold crystallization of PLLA on both heating and cooling. The addition of CNH, CNB, and CB elevated the starting temperature of thermal degradation of PLLA, whereas the addition of SWCNT reduced the thermal stability. Furthermore, the addition of C 60 and SWCNT enhanced the enzymatic degradation of PLLA, whereas the addition of KB and CNB disturbed the enzymatic degradation of PLLA. The reasons for the effects of carbon fillers on the physical properties, crystallization, and enzymatic degradation of PLLA films are discussed.