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Monday, 16 September 2019
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Raw materials & technologies, Raw materials, Coatings binders

Tear-resistant soybean oil

Thursday, 21 February 2013

Biobased investigations highly increase. This time the big issue of a low tensile strength with carbonated soybean oil for polyurethanes is solved.

Polyurethanes based on soybean oil show now a high tensile strength

Source: Fotolia/light-image

Polyurethanes based on soybean oil show now a high tensile strength

Source: Fotolia/light-image

Ivan Javni  and his colleagues from Pittsburg State University prepared polyurethanes  via a nonisocyanate route, by reacting carbonated soybean oil (CSBO) with aromatic and cycloaliphatic diamines.

Amine to carbonate ratio investigated

Nonisocyanate polyurethanes prepared form CSBO and aliphatic diamines have relatively low tensile strength and one of the possible ways to increase strength and rigidity is to use diamines with rigid aromatic or cyclic structure. The researchers studied the effect of amine structure and amine to carbonate ratio on polyurethane structure and mechanical, physical, and swelling properties.
They used m-xylylene diamine (m-XDA), p-xylylene diamine (p-XDA), and isophorone diamine as the reactants, with amine to carbonate ratios of 0.5 : 1, 1 : 1, and 1 : 2.

Gaining tensile strength

All amines produced elastomeric polyurethanes with glass transitions between −6 °C and 26 °C, as measured by differential scanning calorimeter (DSC). Tg was primarily controlled by the amine-to-cyclic carbonate ratio, and to a lesser extent by the amine structure. Javni obtained the highest tensile strength for p-XDA and the lowest for m-XDA as a result of differences in hydrogen bonding. Tensile strength and hardness were higher than in aliphatic diamine-based polyurethanes.

Swelling behaviour studied

Swelling in toluene and water depended on the polarity of polyurethane networks that was dominantly controlled by the amine-to-cyclic carbonate ratio. Swelling in toluene was higher at the lower amine to carbonate ratio due to lower polarity of the polyurethane matrix. Swelling in water behaved quite the opposite, the degree of swelling for the more polar polyurethane matrix was higher. Reaction temperatures of 70–100 °C were high enough to promote ester group cleavage and along with urethanes, amide formation was always present.

The research was published in the Journal for Applied Polymer Science 2013, Volume 128, Issue 1, pages 566–571, 5 April 2013

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