User:Jvquadr/Vegetable plasticizers
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Vegetable Plasticizers
[edit]Plastic is a common designation for many thermoplastic polymers. The properties of these polymers are commonly enhanced or modified through the use of additives. Plasticizers are the most widely used additives, with greater importance for the polyvinyl chloride polymer (PVC). The main function of these plasticizers is to confer flexibility to PVC, which is otherwise a rigid polymer.
Plasticizers represent a large market worldwide. In 2006 plasticizers production reached 6 million tons, with 80% to 90% used for flexible PVC applications.[1]. Phthalates are the most common plasticizers, but as toxicity concerns increase and petroleum prices rise, alternative materials are gaining importance. Among these, vegetable plasticizers are finding increasing interest and penetration.
There are many types of vegetable plasticizers. Current commercially successful products can be classified in 3 main groups: epoxidized esters, acetylated esters, and natural acid esters.
EPOXIDIZED ESTERS OF VEGETABLE OILS
[edit]Vegetable oils compatibility with PVC is weak, making them unsuitable for use as plasticizers. The chemical epoxidation of the naturally occurring double bonds alters the solubility parameters of many vegetable oils to make them compatible with PVC. Further chemical modifications, such as transesterification with various mono alcohols, esterification of hydrolyzed acids with mono, di, tetra and penta alcohols, also produce compatible materials. Many technical evaluations of epoxidized materials show comparisons with traditional plasticizers such as DOP (or DEHP), demonstrating the viability of these products in various applications such as toys, wires and cables, coated fabrics, films, laminates, shoes, and others.
ESBO (epoxidized soybean oil) is the most commonly used epoxidized ester. It is a triglyceride ester, with high molecular weight - approximately 1000. Due to concerns regarding exudation[2], ESBO has a limitation of use[3] at higher concentrations. It has been widely used for decades as a minor additive, to improve thermal stability, but many formulators are stretching the use of this material to reduce cost of final compounds. The use of ESBO in flexible PVC formulations has been normally limited no more than 15% on a weight basis.
EFAME (epoxidized fatty acid methyl ester of soybean oil) is a patented primary plasticizer[4]. It consists of a mixture of components with molecular weight of approximately 350, produced from the methanol alcoholysis and epoxidation of refined soybean oil. Unlike ESBO, EFAME is considered a primary plasticizer for PVC and it can be used as the only plasticizer in a composition, at any concentration. Studies done by Braskem with Brazilian Federal Universities UFABC and UFPR[5] and Solvay with Nexoleum[6] demonstrate the performance of this material, indicating the key differences in comparison to traditional plasticizers. A few key advantages have been noted: higher efficiency (solvation), improved thermal stability, improved UV resistance, improved resistance to heptane extraction. In the process of replacing traditional plasticizers, an expert formulator is required to make proper adjustments to obtain a final PVC compound with the adequate properties.
Epoxidized linseed oil and its derived smaller molecule size esters are well known for its high compatibility and quality, but the higher cost of linseed oil is a limiting factor to consider this product for general use.
Other esters, such as epoxidized higher alcohols monoesters of soybean oil are also gaining importance in the flexible PVC market.
ACETYLATED ESTERS OF VEGETABLE OILS
[edit]Acetylated esters of castor oil have been also successfully introduced in the market, replacing phthalates in many applications. [7]. These materials have also been proven to offer comparable to improved performance over traditional plasticizers, but at a higher cost.
NATURAL ACID ESTERS
[edit]Although not entirely derived from vegetables, Esters of Citric Acid are also commonly used as plasticizers for PVC. Citric acid is esterified with various alcohols to generate triesters of higher alcohols, together with the esterification of the hydroxyl group (of the original citric acid) that are compatible with PVC. These products have a more limited usage due to a higher cost when compared to traditional plasticizers.
References
[edit]- ^ Plasticizers Market Data, Arbeitsgemeinschaft PVC und Umwelt e.V. http://www.agpu.de/fileadmin/user_upload/information_herunterlade/Marktdaten%20Weichmacher_230106.lin_en.pdf
- ^ Edward J. Wickson, "Handbook of PVC Formulating" - pp 253 to 264, 1993
- ^ Exudation of Epoxidized Soybean Oil in PVC, http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?action=rtdoc&an=5756934
- ^ Vegetable Plasticizers, Battelle Memorial Institute http://www.battelle.org/productscontracts/techtrans/summary/vegetable.aspx
- ^ Study of the use of plasticizer from renewable sources in PVC compositions, http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-14282009000400004&lang=pt
- ^ Compounding PVC with Renewable Materials, http://www.solvayplastics.com/sites/solvayplastics/EN/Solvay%20Plastics%20Literature/BR_Compounding_PVC_with_Renewable_Materials_EN.pdf
- ^ Danisco Soft'n Safe Plasticizers, http://www.danisco-softnsafe.com/
External links
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