Mika Härkönen, Kari Hiltunen, Minna Malin, Jukka V. Seppälä

    Research output: Contribution to journalArticleScientificpeer-review


    Aliphatic polyesters, such as poly(lactic acids), need high molecular weight for acceptable mechanical properties. This can be achieved through ring-opening polymerization of lactides. The lactide route is, however, relatively complicated, and alternative polymerization routes are of interest. In this paper we report the properties of a polymer made by a two-step process: first a condensation polymerization of lactic acid and then an increase of the molecular weight with diisocyanate. The end product is then a thermoplastic poly(ester-urethane). The hydroxyl-terminated prepolymer was made with condensation polymerization of L-lactic acid and a small amount of 1,4-butanediol. The polymerization was performed in the melt under nitrogen and reduced pressure. The preparation of poly(ester-urethane) was done in the melt using aliphatic diisocyanates as the chain extenders reacting with the end groups of the prepolymer. The polymer samples were carefully characterized, including preliminary degradation studies. The results indicate that this route to convert lactic acid into thermoplastic biodegradable polymer has high potential. Lactic acid is converted into a mechanically attractive polymer with high yield, which could make the polymer suitable for high volume applications. The mechanical properties of the poly(ester-urethane) are comparable with those of poly(lactides). Capillary rheometer measurements indicate that the polymer is processible both by injection molding and extrusion.

    Original languageEnglish
    Pages (from-to)857-862
    Number of pages6
    JournalJournal of Macromolecular Science Part A: Pure and Applied Chemistry
    Issue number4
    Publication statusPublished - 1995
    MoE publication typeA1 Journal article-refereed


    • biodegradable thermoplastic


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