This paper describes the production of “green” microfibrillated cellulose-reinforced polylactide cellular biocomposites using a wet mixing technique combined with supercritical carbon dioxide foaming. The effect of composition on the morphology, density and compression modulus of foams was investigated for different processing parameters, along with the use of a chain extender to modify the melt elasticity. Foams with mean densities ranging from 0.18 to 0.32 g/cm3 were obtained for the neat polylactide and polylactide/5 wt% microfibrillated cellulose, respectively, and there was a corresponding increase in compressive modulus from 25 to 47 MPa. The addition of the chain extender is argued to compensate the molar mass loss induced by the different processing steps, promoting more uniform foam structures and allowing a density reduction of up to 75%.
CarothersWDoroughGVan NattaF. Studies of polymerization and ring formation. X. The reversible polymerization of six-membered cyclic esters. J Am Chem Soc1932; 54: 761–772.
2.
BledzkiAJaszkiewiczASherzerD. Mechanical properties of PLA composites with man-made cellulose and abaca fibres. Compos Part A-Appl S2009; 40: 404–412.
3.
BogrenKMGamstedtEKNeaguRC. Dynamic-mechanical properties of wood-fiber reinforced polylactide: Experimental characterization and micromechanical modeling. J Thermoplast Compos Mater2006; 19: 613–637.
4.
HudaMSDrzalLTMisraM. Wood-fiber-reinforced poly(lactic acid) composites: Evaluation of the physicomechanical and morphological properties. J Appl Polym Sci2006; 102: 4856–4869.
5.
MathewAPOksmanKSainM. The effect of morphology and chemical characteristics of cellulose reinforcements on the crystallinity of polylactic acid. J Appl Polym Sci2006; 101: 300–310.
NakagaitoAFujimuraASakaiT. Production of microfibrillated cellulose (MFC)-reinforced polylactic acid (PLA) nanocomposites from sheets obtained by a papermaking-like process. Compos Sci Technol2009; 69: 1293–1293.
8.
TingautPZimmermannTLopez-SuevosF. Synthesis and characterization of bionanocomposites with tunable properties from poly(lactic acid) and acetylated microfibrillated cellulose. Biomacromolecules2010; 11: 454–464.
9.
ZimmermannTPohlerESchwallerP. Mechanical and morphological properties of cellulose fibril reinforced nanocomposites. Adv Eng Mater2005; 7: 1156–1161.
10.
Azizi SamirMASAlloinFDufresneA. Review of recent research into cellulosic whiskers, their properties and their application in nanocomposite field. Biomacromolecules2005; 6: 612–626.
11.
ZimmermannTPohlerEGeigerT. Cellulose fibrils for polymer reinforcement. Adv Eng Mater2004; 6: 754–761.
12.
MatuanaLMParkCBBalatineczJJ. Cell morphology and property relationships of microcellular foamed PVC/wood-fiber composites. Polym Eng Sci1998; 38: 1862–1872.
13.
NalawadeSPPicchioniFJanssenL. Supercritical carbon dioxide as a green solvent for processing polymer melts: Processing aspects and applications. Prog Polym Sci2006; 31: 19–43.
14.
CarrascoFPagesPGamez-PerezJ. Processing of poly(lactic acid): Characterization of chemical structure, thermal stability and mechanical properties. Polym Degrad Stabil2010; 95: 116–125.
15.
PeregoGCellaGBastioliC. Effect of molecular weight and crystallinity on poly(lactid acid) mechanical properties. J Appl Polym Sci1996; 59: 37–43.
16.
JamshidiKHyonSHIkadaY. Thermal characterization of polylactides. Polymer1988; 29: 2229–2234.
17.
FrenzVScherzerDVillalobosM. Multifunctional polymers as chain extenders and compatibilizers for polycondensates and biopolymers in SPE's ANTEC2008. , Milwaukee.
18.
PillaSKimSGAuerGK. Microcellular extrusion-foaming of polylactide with chain-extender. Polym Eng Sci2009; 49: 1653–1660.
19.
DorganJRLehermeierHMangM. Thermal and rheological properties of commercial-grade poly(lactic acid)s. J Polym Environ2000; 8: 1–9.
20.
MihaiMHuneaultMAFavisBD. Rheology and extrusion foaming of chain-branched poly(lactic acid). Polym Eng Sci2009; 50: 629–642.
21.
LehermeierHJDorganJR. Melt rheology of poly(lactic acid): Consequences of blending chain architectures. Polym Eng Sci2001; 41: 2172–2184.
22.
PaakkoMAnkerforsMKosonenH. Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels. Biomacromolecules2007; 8: 1934–1941.
23.
AntalMVarhegyiG. Cellulose pyrolysis kinetics: the current state of knowledge. Ind Eng Chem Res1995; 34: 703–717.
24.
Di BlasiCBrancaCSantoroA. Pyrolity behavior and products of some wood varieties. Combust Flame2001; 124: 165–177.
25.
BuhlerMBourbanPEMånsonJ-AE. Cellular thermoplastic composites with microstructural gradients of fibres and porosity. Compos Sci Technol2008; 68: 820–828.
26.
MathieuLMMontjoventMOBourbanPE. Bioresorbable composites prepared by supercritical fluid foaming. J Biomed Mater Res Part A2005; 75A: 89–97.
27.
GarlottaD. A literature review of poly(lactic acid). J Polym Environ2001; 9: 63–84.
SiqueiraGBrasJDufresneA. Cellulose whiskers versus microfibrils: influence of the nature of the nanoparticle and its surface functionalization on the thermal and mechanical properties of nanocomposites. Biomacromolecules2009; 10: 425–432.
30.
DoroudianiSChaffeyCEKortschotMT. Sorption and diffusion of carbon dioxide in wood-fiber/polystyrene composites. J Polym Sci Part B-Polym Phys2002; 40: 723–735.
MengelogluFMatuanaLM. Foaming of rigid PVC/wood-flour composites through a continuous extrusion process. J Vinyl Addit Technol2001; 7: 142–148.
33.
RachtanapunPSelkeSEMMatuanaLM. Microcellular foam of polymer blends of HDPE/PP and their composites with wood fiber. J Appl Polym Sci2003; 88: 2842–2850.
34.
MatuanaLMParkCBBalatineczJJ. Structures and mechanical properties of microcellular foamed polyvinyl chloride. Cell Polym1998; 17: 1–16.
35.
MatuanaLMParkCBBalatineczJJ. Processing and cell morphology relationships for microcellular foamed PVC/wood-fiber composites. Polym Eng Sci1997; 37: 1137–1147.
36.
ZhangHRizviGMParkCB. Development of an extrusion system for producing fine-celled HDPE/wood-fiber composite foams using CO2 as a blowing agent. Adv Polym Technol2004; 23: 263–276.
37.
MatuanaLM. Solid state microcellular foamed poly(lactic acid): Morphology and property characterization. Biores Technol2008; 99: 3643–3650.
38.
HentonDGruberPLuntJPolylactic acid technology. In: MohantyA (eds). Natural fibers, biopolymers, and biocomposites: an introduction, Boca Raton, FL: CRC Press, 2005; 527–577.
GuoGWangKHParkCB. Effects of nanoparticles on density reductin and cell morphology of extruded metallocene polyethylene/wood fiber nanocomposites. J Appl Polym Sci2007; 104: 1058–1063.
41.
NeaguRCGamstedtEKBertholdF. Stiffness contribution of various wood fibers to composite materials. J Compos Mater2006; 40: 663–699.
42.
GibsonLAshbyM. Cellular solids-structure and properties, Oxford: Pergamon Press, 1988.
