Effects of Natural Fiber Surface Modification on Mechanical Properties of Poly(lactic acid) (PLA)/Sweet Sorghum Fiber Composites
(1583-1589) Polymer - Plastics Technology and Engineering 50 #15 (2011)
Abstract
Zhang et al of the Beijing University of Chemical Technology, China, formed poly(lactic acid)/sweet sorghum fiber composites by melt compounding and compression molding. Four different kinds of surface treating agents (amino silicone oil (ASO), silane coupling agent (SCA), emulsified wax (EW) and titanate coupling agent (TCA)) were used to modify the natural fiber surface to reduce hydrophilicity. PLA/TCA-F composite showed the maximum flexural strength, 60 MPa, which is 63% morethan that of the control. (RDC 11/11/2011)

Preparation, characterization, and biodegradability of renewable resource-based composites from recycled polylactide bioplastic and sisal fibers
(347–355)Journal of Applied Polymer  Science 123 #1 (2012)
Wu of the Kao Yuan University, China, showed that composites containing acrylic acid-grafted PLA (PLA-g-AA/SF) had noticeably superior mechanical properties because of greater compatibility between the two components.  The dispersion of SF in the PLA-g-AA matrix was highly homogeneous as a result of ester formation and the consequent creation of branched and crosslinked macromolecules between the carboxyl groups of PLA-g-AA and hydroxyl groups in SF.  (RDC 10/12/2011)

ENVIRONMENTAL DEGRADATION OF STARCH/POLY(LACTIC ACID) COMPOSITE IN SEAWATER
(559-566) Polymers and Polymer Composites 19 #7 (2011)
Chen et alstudied the degradation property of starch/polylactic acid (PLA) composites in a briny environment by immersion of injection-moulded tensile bars of starch/PLA composites in static seawater controlled at 25 degrees C for 1 year. SEM micrographs showed that starch particles were lost from the bar because of microbial action. GPC results showed the number average molecular weight (Mn) of PLA decreased with degradation time. The glass transition temperature (Tg) and melting temperature (Tm) measured by DSC decreased slightly with degradation time. An increase of crystallinity calculated from the DSC data was attributed to the decrease of molecular weight. Weight losses were mainly due to loss of starch. The impact strength of the composites decreased monotonically with degradation time; tensile strength and elongation at break of the composites first decreased, then increased and at last decreased again with degradation time, and the water was acting as a plasticiser. The starch/PLA composites in seawater had degradability, but the degradation rate of composite bars studied in this paper was very slow. (RDC 9/2/2011)

PLA Based Biopolymer Reinforced with Natural Fibre: A Review
(714-725) Journal of Polymers and the Environment 19 #3 (2011)
Mukherjee and Kao of RMIT University, Australia, reviewed the effects of processing methods, fibre length, fibre orientation, fibre-volume fraction, and fibre-surface treatment on the fibre/matrix adhesion and mechanical properties of natural-fibre-reinforced PLA composites.  Although much work has been performed to engineer the design of such superior biocomposites, the information is scattered in nature. A comprehensive review on the major technical considerations undertaken to prepare such biocomposites over the last decade is investigated to address the feasibility of wide scale industrial acceptance to such biocomposites. A brief review on the available natural fibres and biopolymer is also given for a comparative study.  (RDC 8/23/2011)

Renewable Resource-Based Composites of Acorn Powder and Polylactide Bio-Plastic: Preparation and Properties Evaluation
(301-311) Journal of Polymers and the Environment 19 #1 (2011)
Li et al , China, developeda renewable resource-based composites with acorn powder and thermoplastic resin poly(lactic acid) (PLA) by twin-screw extrusion followed by injection molding processing or hot-compression molding processing.  Silane coupling agent, 4,4′-Methylenebis (phenyl isocyanate) and PLA grafted with maleic anhydride did not show obvious effect on mechanical properties of composites. The impact resistance strength of reinforced composites with steel fiber webs were improved greatly in comparison with those having no steel fiber webs. The study results proved that composites had superior mechanical properties, enough to partially replace the conventional thermoplastic plastics.  (RDC 4/22/2011)

Effects of Alkali Treatment on the Properties of Short Flax Fiber–Poly(Lactic Acid) Eco-Composites
(11-17) Journal of Polymers and the Environment 19 #1 (2011)
Aydin et al of Kocaeti University, Turkey, studied the influence of alkali (NaOH) treatment on the mechanical, thermal and morphological properties of eco-composites of short flax fiber/poly(lactic acid) (PLA).  SEM analysis conducted on alkali treated flax fibers showed that the packed structure of the fibrils was deformed by the removal non-cellulosic materials. The fibrils were separated from each other and the surface roughness of the alkali treated flax fibers was improved.  The mechanical tests indicated that the modulus of the untreated fiber/PLA composites was higher than that of PLA; on the other hand the modulus of alkali treated flax fiber/PLA was lower than PLA. Thermal properties of the PLA in the treated flax fiber composites were also affected. Tg values of treated flax fiber composites were lowered by nearly 10 °C for 10% NaOH treatment and 15 °C for 30% NaOH treatment. A bimodal melting behavior was observed for treated fiber composites different than both of neat PLA and untreated fiber composites. Furthermore, wide angle X-ray diffraction analysis showed that the crystalline structure of cellulose of flax fibers changed from cellulose-I structure to cellulose-II.  (RDC 4/22/2011)