Laurent M. Matuana

Cell morphology of extrusion foamed poly(lactic acid) using endothermic chemical foaming agent

Poly(lactic acid) (PLA) was foamed with an endothermic chemical foaming agent (CFA) through an extrusion process. The effects of polymer melt flow index, CFA content, and processing speed on the cellular structures, void fraction, and cell-population density of foamed PLA were investigated. The apparent melt viscosity of PLA was measured to understand the effect of melt index on the cell morphology of foamed PLA samples. The void fraction was strongly dependent on the PLA melt index. It increased with increasing melt index, reaching a maximum value, after which it decreased. Melt index showed no significant effect on the cell-population density of foamed samples within the narrow range studied. A gas containment limit was observed in PLA foamed with CFA. Both the void fraction and cell-population density increased with an initial increase in CFA content, reached a maximum value, and then decreased as CFA content continued to increase. The processing speed also affected the morphology of PLA foams. The void fraction reached a maximum value as the extruders screw speed increased to 40 rpm and a further increase in the processing speed tended to reduce the void fraction of foamed samples. By contrast, cell-population density increased one order of magnitude by increasing the screw speed from 20 to 120 rpm. The experimental results indicate that a homogeneous and finer cellular morphology could be successfully achieved in PLA foamed in an extrusion process with a proper combination of polymer melt flow index, CFA content, and processing speed.

Chemical modification of nanocellulose with canola oil fatty acid methyl ester

Cellulose nanocrystals (CNCs), produced from dissolving wood pulp, were chemically functionalized by transesterification with canola oil fatty acid methyl ester (CME). CME performs as both the reaction reagent and solvent. Transesterified CNC (CNCFE) was characterized for their chemical structure, morphology, crystalline structure, thermal stability, and hydrophobicity. Analysis by Fourier transform infrared (FTIR) and FT-Raman spectroscopies showed that the long chain hydrocarbon structure was successfully grafted onto CNC surfaces. After transesterification the crystal size and crystallinity of nanocrystals were not changed as determined by Raman spectroscopy and wide angle X-ray diffraction (XRD). CNCFE showed higher thermal stability and smaller particle size than unmodified CNCs. Water contact angle measurement indicated the CNCFE surface has significantly higher hydrophobicity than unmodified CNCs. The transesterified CNCs could be potentially used as hydrophobic coatings and reinforcing agents to hydrophobic polymer for nanocomposites.

The use of wood fibers as reinforcements in composites

Abstract: The chapter begins by discussing the major characteristics of wood in terms of structure, major chemical constituents and wood fiber production methods, which is followed by the description of major manufacturing processes for wood plastic composites (WPCs). It then reviews the effects of different variables such as the nature of wood flour (particle size, wood species, and wood flour content), filler–matrix adhesion, characteristics of polymer matrix, processing conditions, performance-enhancing additives, and foaming agents on the physical, mechanical, thermal, and durability properties of WPCs. Finally, the chapter discusses future trends in WPCs including new materials, novel manufacturing techniques, and emerging applications.

Preparation and characterization of the nanocomposites from chemically modified nanocellulose and poly(lactic acid)

Cellulose nanocrystals (CNCs) are renewable and sustainable filler for polymeric nanocomposites. However, their high hydrophilicity limits their use with hydrophobic polymer for composite materials. In this study, freeze-dried CNCs were modified by transesterification with canola oil fatty acid methyl ester to reduce the hydrophilicity. The transesterified CNCs (CNCFE) were compounded with PLA into nanocomposites. CNCFE with long-chain hydrocarbons plays a role as plasticizer. Increasing CNCFE loadings resulted in clear plasticizing effects. Lower Tg and Tm were achieved for CNCFE-based nanocomposites. Plasticizing nanocomposite melt with CNCFE can mitigate the degradation of CNCs during thermal processing. The elongation at break of nanocomposites containing 5% CNCFE was increased. Dynamic rheological study showed the highest elastic and viscous moduli (G′ and G′′) and complex viscosity (G*) of nanocomposites with addition of 2% CNCFE. By tailoring the loadings of the transesterified CNCs, tunable structure and properties of nanocomposites can be obtained.

Effect of processing parameters on the quality of red oak flakes

ABSTRACT A lot of volume of red oak (Quercus rubra) is available for use in the manufacture of oriented strand board (OSB) in the Appalachian and Northeast regions of the U.S.A. However, the large amount of fines and low quality of red oak ring-cut flakes produced in industry have restricted their use in commercial OSB products. This study evaluated the effects of log pre-treatment temperature and disc flaker’s knife clearance on the quality of red oak flakes. Experimental results showed that heat treatment was the dominant factor than the flaker’s knife clearance during oak disc-cut flaking. A large amount of high quality oak flakes with acceptable geometry and minimal fines suitable for usage as face furnish on the OSB panel can be produced with a proper log heating treatment before flaking.