Mechanical properties polylactic acid

Polymer blends have been categorized as (1) compatible, exhibiting only a single Tg, (2) mechanically compatible, exhibiting the Tg values of each component but with superior mechanical properties, and (3) incompatible, exhibiting the unenhanced properties of phase-separated materials (8). Based on the mechanical properties, it has been suggested that PCL-cellulose acetate butyrate blends are compatible (8). Dynamic mechanical measurements of the Tg of PCL-polylactic acid blends indicate that the compatability may depend on the ratios employed (65). Both of these blends have been used to control the permeability of delivery systems (vide infra). 

Tawakkal, 1. S. M. A., Talib, R. A., Abdan, K., and Ling, C. N. (2012). Mechanical and physical properties of kenaf-derived cellulose (KDC)-filled polylactic acid (PLA) composites. Bioresmirces. 1,1643-1655. 

Semba, T., Kitagawa, K., Ishiaku, U.S., Hamada, H. The Effect of crosslinking on the mechanical properties of polylactic acid/polycaprolactone blends. J. Appl. Polym. Sci. 101(3), 1816-1825 (2006)... 

Balakrishnan, H., Hassan, A., Wahit, M.U. Mechanical, thermal and morphological properties of polylactic acid/linear low density polyethylene blends. J. Elastomers Plast 42(3), 223-229 (2010)... 

Yussuf, A.A., Massoumi, I., Hassan, A. Comparison of polylactic acid/kenaf and polylactic acid/rise husk composites The influence of the natural fibers on the mechanical, thermal and biodegradability properties. J. Polym. Environ. 18(3), 422-429 (2010)... 

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

K. Hamad, Y. Gun, Ko, M. Kaseem, F. Deri. Effect of acrylonitrile-butadiene-styrene on flow behaviour and mechanical properties of polylactic acid/low density polyethylene blend. 

The bio-related resin polylactic acid is well known as a renewable material. However, renewable materials such as this lack the mechanical and thermal properties to be of any practical use. hi order to overcome these drawbacks, the synthesis of clay nanocomposites based on renewable materials has been discussed. These materials are known as Green Nanocomposites [44] and are now forming a new sector in materials studies. 

The poly-L-lactic acid shows high melting points and good mechanical properties. Polylactic acid degrades by hydrolysis, which has been shown to be accelerated by many enzymes. Recently, it has been found to be biodegradable in a compost environment [43, 45]. The thermoplastic material can be made stereo specific or racemic to yield different properties. 

Noishiki Y, Nishiyama Y, Wada M et al (2002) Mechanical properties of silk fibroin-microcrys-talline cellulose composite films. J Appl Polym Sci 86 3425-3429 O Sullivan AC (1997) Cellulose the structure slowly unravels. Cellulose 4 173-207 Oksman K, Mathew AP, Bondeson D et al (2006) Manufacturing process of cellulose whiskers/ polylactic acid nanocomposites. Compos Sci Technol 66 2776-2784 Orts WJ, Godbout L, Marchessault RH et al (1998) Enhanced ordering of liquid crystalline suspensions of cellulose microfibrils a small-angle neutron scattering study. Macromolecules 31 5717-5725... 

M. Ragoubi, B. George, S. Molina, D. Bienaime, A. Merlin, J.-M. Hiver, and A. Dahoun, Effect of corona discharge treatment on mechanical and thermal properties of composites based on miscanthus fibres and polylactic acid or polypropylene matrix. Compos. A 43, 675-685 (2012). 

P.K. Bajpai, I. Singh, and J. Madaan, Joining of natural fiber reinforced composites using microwave energy Experimental and finite element study. Mater. Des. 35, 596-602 (2012). P. K. Bajpai, I. Singh, and J. Madaan, Comparative studies of mechanical and morphological properties of polylactic acid and polypropylene based natural fiber composites. Reinf. Plast. Compos. 31, 1712-1724 (2012). 

G.H. Yew, A.M.M. Yusof, Z.A.M. Ishak and US. Ishiaku, Natural Weathering Effects on the Mechanical Properties of Polylactic Acid/Rice Starch Composites, in Proceedings of the 8th Polymers for Advanced Technologies International Symposium, Budapest, Hungary, Volume 1 (2005). 

To improve processability, mechanical properties and moisture resistance while maintaining biodegradability, starch may be mixed with aliphatic or aliphatic-aromatic polyesters, such as polycaprolactone (PCL), polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT), suffering complexing with these pol)miers [33,35]. 

Recent publications describe the effects of silica on the conductivity and mechanical properties of a polyethylene oxide/ammonium bifluoride complex containing propylene carbonate [36], as a foam stabilizer in polyester polyurethane foams, and on the properties of polylactic acid nanocomposites prepared by the sol-gel technique [37] (see also Chapter 24), on the mechanical properties and permeability of i-PP composites [38], on the surface hardness of polymers for biomedical devices [39], on enhanced properties of polymer interlayers that are used in multiple layer glazing panels [40]. 

Unitika Ltd. of Osaka, Japan has developed a hydrolysis-resistant polylactic acid which, when combined with a nanoclay filler, is said to have sufficiently good mechanical and thermal properties to be targeted at computer, electronic and automotive parts. 

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