Modified and unmodified technical lignins as flame retardants for polypropylene

Petri Widsten (Corresponding Author), Tarja Tamminen, Antti Paajanen, Tuula Hakkarainen, Tiina Liitiä

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)


Polyolefins used in building materials and furniture require the use of flame-retardant (FR) additives to improve their fire safety. Such additives should be safe to humans and the environment, and preferably bio-based. In the present work, the FR performance of unmodified and chemically modified technical lignins was compared to that of the ammonium polyphosphate/pentaerythritol (APP/PER) intumescent system in a polypropylene (PP) matrix. Micro-scale combustion calorimetry (MCC) was used to study the peak heat release rate (PHR), temperature at PHR (TPHR), total heat release (THR) and char yield upon thermal decomposition of milligram-scale specimens. The PP/lignin composites showed up to 41% lower PHR and up to 36% lower THR compared to pure PP as well as large char residues. Based on the same parameters, especially the PP/lignin composites made with modified lignins outperformed the reference PP/APP/PER system and the PP/APP/lignin composites where unmodified lignin was used with APP. The most promising PP/lignin composites were prepared with partially demethylated/demethoxylated and depolymerised kraft lignin (‘CatLignin’), modified by the Mannich reaction to a nitrogen content of 13.5%.
Original languageEnglish
Pages (from-to)584-590
Number of pages7
Issue number6
Publication statusPublished - 1 Jun 2021
MoE publication typeA1 Journal article-refereed


  • chemical modification
  • flame retardant
  • lignin
  • micro-scale combustion calorimetry
  • polypropylene
  • thermal properties


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