Bioplastificantes

1 J. Applied Polymer Science, Vol. 102, 1366-1373, 2006

Evaluation of the effects of bio-based plasticizers on thermal and mechanical properties of poly (vinylchloride)
N. Gil1, I. Negulescu2 and M. Saska1 Audubon Sugar Institute, Louisiana State University Agricultural Center, St. Gabriel, LA 70776 2 Department of Human Ecology, Louisiana State University Agricultural Center, Baton Rouge, LA70803 ABSTRACT Blends were prepared of PVC with four different plasticizers, esters of aconitic, citric and phthalic acids, and other ingredients used in commercial flexible PVC products. Thermal and mechanical properties were measured of the fresh products and after six months of aging. The Young modulus of the PVC blends was reduced about ten-fold by raising the plasticizer level from 15 to 30phr, from the semi-rigid to flexible range according to the ASTM classification, but a 40 phr level was required for PVC to retain its flexibility beyond six months. At the 40 phr level, tri-butyl aconitate performed better than di-isononyl phthalate or tri-butyl citrate, in terms of lowering Young modulus, both in fresh materials and after six months of aging. Effects of the four plasticizers onthe glass transition temperature were similar, with Tg close to ambient temperature at the 30 and 40 phr levels in freshly prepared samples and 40 to 60˚C after a period of six months. The thermal stability of the PVC plasticized with di-isononyl phthalate was superior among the group. Overall, tri-butyl aconitate appears to be a good candidate for use in consumer products where the allegedtoxicity of DINP may be an issue. Key words: poly (vinyl chloride) PVC; plasticizer; plastics; tri-butyl aconitate; aconitic acid; sugar cane; tri-butyl citrate; citric acid; di-isononyl phthalate INTRODUCTION After polyethylene, poly (vinyl chloride) is the most widely used plastic. Some 25 to 35 % of the total PVC production goes into flexible consumer products such as wire and cable insulation,flooring, wall covering and packaging materials. For those applications, before molding or extrusion, PVC must be blended with a suitable plasticizer, a compound designed to weaken intermolecular bonds in the polymer in order to increase its workability, toughness and flexibility1,2. In addition to its good miscibility with the polymer, other attributes of a good plasticizer are a high boiling point toprevent or reduce its loss during processing and a low rate of migration out of the polymer to avoid loss of its properties3 and contamination of the materials or consumers in contact with it if it is a part of food grade or personal use products.
1

1

2
H2C-COO-(n-Bu) CH3-COO-C-COO-(n-Bu) H2C-COO-(n-Bu) ATBC HC-COO-(n-Bu) C-COO-(n-Bu) H2C-COO-(n-Bu) TBA O H2C-COO-(n-Bu) HO-C-COO-(n-Bu)H2C-COO-(n-Bu) TBC O O O DINP

Figure 1. Chemical structure of the four plasticizers tested in this work, esters of citric, aconitic and phthalic acids. Until now, plasticizers produced from phthalic anhydride, such as DINP, diisononylphthalate (Figure 1), DEHP, di-2 ethylhexylphthalate and DIDP, di-isodecylphthalate have been the most widely used. In a recent work1 the effects were evaluated ofseveral phthalate plasticizers and their blends on mechanical, thermal and electrical properties of PVC. However, growing concerns about their toxicity4-6 in consumer products made of PVC have led to a search for alternatives that would not elicit the same public health concerns. An alternative to phthalates have been esters of bio-derived citric acid, such as tri-butyl citrate (TBC), acetyltributyl citrate (ATBC) (Figure 1), tri-ethyl citrate, acetyl tri-ethyl citrate and tri-(2-ethylhexyl)citrate. The U.S. Federal Drug Administration (FDA) approved both the acid and its esters as additives in food 7. Nevertheless, the price of these esters is about three times higher than that of phthalates and their application is limited to small niche markets. Another alternative that was proposed...