The Effect of Annealing Treatments on Spherulitic Morphology and Physical Ageing on Glass Transition of Poly Lactic Acid (PLLA)

El-Hadi Ahmed Mohamed
DOI: 10.4236/msa.2011.25058                

Abstract

Spherulitic morphology of pure poly lactic acid (PLLA) PLLA have investigated after thermal annealing. The morphology of spherulite of pure poly lactic acid (PLLA) PLLA have investigated after thermal annealing. The effect of both annealing temperature and crystallization temperature on the formation of cracks was described by polarized optical microscope (POM). Non banded spherulite (fibrils) with cracks was detected in PLLA film after annealing at 160°C (180 min.) and isothermal crystallization temperatures at 140°C and 150°C. With increasing temperature after annealing treatment the size of spherulite is increased and more cracks are formed. The maximum growth rate of spherulites was found at 130°C. The physical ageing was carried out by annealing the PLLA sample at room temperature for several annealing time (ta) from 0 h to 720 h. The enthalpy relaxation has been studied by differential scanning calorimetry (DSC) through analysis of the endothermic peak of glass transition temperature, which increased and shifted towards higher temperature as the annealing time increased.

Keywords

Poly Lactic Acid (PLLA), Morphology, Non-Banded Spherulites, Annealing, Polarized Optical Microscopy, Physical Ageing

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	A. El-Hadi and R. Schnabel, “Effect of Melt Processing on Crystallization Behavior and Rheology of Poly(3-hydro-xybutyrate) (PHB) and Its Blends,” Macromolecular Materials and Engineering, Vol. 287, No. 5, 2002, pp. 363-372. doi:10.1002/1439-2054(20020501)287:5<363::AID-MAME363>3.0.CO;2-D
[2]	A. El-Hadi and R. Schnabel, “Correlation between Degree of Crystallinity, Morphology, Glass Temperature, Mechanical Properties and Biodegradation of Poly (3-hydroxyal-kanoate) PHAs and Their Blends,” Polymer Test, Vol. 21, No. 6, 2002, pp. 665-674. doi:10.1016/S0142-9418(01)00142-8
[3]	A. El-Hadi, “Development of a Biodegradable Material Based on Poly(3-hydroxybutyrate) PHB,” Ph.D. Dissertation, Physics Department, University of Halle-Witten- berg, Halle and Wittenberg, 2002.
[4]	Y. Ikada and H. Tsuji, “Biodegradable Polyesters for Medical and Ecological Applications,” Macromolecules Rapid Communication, Vol. 21, No. 3, 2000, pp. 117-132.
[5]	S. Petrulyte, “Advanced Textile Materials and Biopolymers in Wound Management,” Danish Medical Bulletin, Vol. 55, No. 1, 2008, pp. 72-77.
[6]	W. H. Hoidy, M. B. Ahmad, E. A. J. Al-Mulla and N. A. B. Ibrahim, “Preparation and Characterization of Polylactic Acid and Polycaprolactone Clay Nanocomposites,” Journal of Applied Sciences, Vol. 10, No. 2, 2010, pp. 97-106. doi:10.3923/jas.2010.97.106
[7]	Z. Kulinski and E. Piorkowska, “Plasticization of Poly(L-lactide) with Poly(propylene glycol),” Biomacromolecules, Vol. 7, No. 20, September 2006, pp. 2128-2135. doi:10.1021/bm060089m
[8]	R. Masirek, E. Piórkowska, A. Ga??ski and M. Mucha, “Influence of Thermal history on the Nonisothermal Crystallization of Poly(L-lactide),” Journal Applied Polymer Science, Vol. 105, No. 1, 2007, pp. 282-290. doi:10.1002/app.26047
[9]	M. Koz?owski, R. Masirek, E. Piórkowska and M. Gazicki-Lipman, “Biodegradable Blends of Poly(L-lactide) and Starch,” Journal Applied Polymer Science, Vol. 105, No. 1, 2007, pp. 269-277. doi:10.1002/app.26088
[10]	M. Pluta and A. Ga??ski, “Plastic Deformation of Amorphous Poly(L/DL-lactide), Structure Evolution and Physical Prorties,” Biomacromolecules, Vol. 8, No. 6 2007, pp. 1836-1843. doi:10.1021/bm061229v
[11]	M. Pluta, “Melt Compounding of Polylactide/Organoclay: Structure and Properties of Nanocomposites,” Journal Polymer Science B: Polymer Physics, Vol. 44, No. 23, 2006, 3392-3405. doi:10.1002/polb.20957
[12]	H. D. Keith and F. J. Padden, “The Optical Behavior of Spherulites in Crystalline Polymers, Part I, “Calculation of Theoretical Extinction Patterns in Spherulites with Twisting Crystalline Orientation,” Journal Polymer Science, Vol. 39, No. 135, 1959, pp. 101-122.
[13]	A. J. Lovinger and D. C. Bassett, “Development in Crystalline Polymers-1, Chapter 5,” Applied Science Publishers, 1982, pp. 195-273.
[14]	M. L. Di Lorenzo, “Crystallization Behavior of Poly(L-lactic acid),” European Polymer Journal, Vol. 41, No. 3, 2005, pp. 569-575. doi:10.1016/j.eurpolymj.2004.10.020
[15]	R. Vasanthakumari and A. J. Pennings, “Crystallisation Kinetics of Poly(L-Lactic acid),” Polymer, Vol. 24, No. 2, 1983, pp. 175-178. doi:10.1016/0032-3861(83)90129-5
[16]	Y. Yuryev, P. Wood-Adams and M. C. Heuzey, “Crystallization of polylactide films: An Atomic Force Microscopy Study of the Effects of Temperature and Blending,” Polymer, Vol. 49, No. 9, 2008, pp. 2306-2320. doi:10.1016/j.polymer.2008.02.023
[17]	L. C. E. Struik, “Mechanical Behavior and Physical Ageing of Semi-Crystalline Polymers,” Polymer, Vol. 30, No. 5, 1989, pp. 815-830. doi:10.1016/0032-3861(89)90177-8
[18]	J. K. Hobbs, T. J. McMaster, M. J. Miles and P. J. Barham, “Cracking in Spherulites of Poly(hydroxybutyrate),” Journal Polymer Science Part B: Polymer Physics, Vol. 37, No. 15, 1996, pp. 3241-3246.