title: Synthesis of waterborne polyurethane-urea dispersions with chain extension step in homogeneous and heterogeneous media.
abstract: OBJECTIVE
  The possibility of tailoring the final properties of environmentally friendly waterborne polyurethane and polyurethane-urea dispersions and the films they produce makes them attractive for a wide range of applications. Both the reagents content and the synthesis route contribute to the observed final properties.
  
  
  METHODS
  A series of polyurethane-urea and polyurethane aqueous dispersions were synthesized using 1,2-ethanediamine and/or 1,4-butanediol as chain extenders. The diamine content was varied from 0 to 4.5wt%. Its addition was carried out either by the classical heterogeneous reaction medium (after phase inversion step), or else by the alternative homogeneous medium (prior to dispersion formation). Dispersions as well as films prepared from dispersions have been later extensively characterized.
  
  
  RESULTS
  1,2-Ethanediamine addition in heterogeneous medium leads to dispersions with high particle sizes and broad distributions whereas in homogeneous medium, lower particle sizes and narrow distributions were observed, thus leading to higher uniformity and cohesiveness among particles during film formation. Thereby, stress transfer is favored adding the diamine in a homogeneous medium; and thus the obtained films presented quite higher stress and modulus values. Furthermore, the higher uniformity of films tends to hinder water molecules transport through the film, resulting, in general, in a lower water absorption capacity.
authors.affiliation: Group 'Materials + Technologies', Department of Chemical and Environmental Engineering, Polytechnic School, University of the Basque Country, Pza Europa 1, 20018 Donostia-San Sebastián, Spain. Electronic address: arantzazu.santamaria@ehu.eus.
authors.forename: Arantzazu
authors.initials: A
authors.lastname: Santamaria-Echart
authors.affiliation: Laboratory of Separation and Reaction Engineering (LSRE), Associate Laboratory LSRE/LCM, Polytechnic Institute of Bragança, Campus of Santa Apolonia, 5300-253 Bragança, Portugal. Electronic address: ipmf@ipb.pt.
authors.forename: Isabel
authors.initials: I
authors.lastname: Fernandes
authors.affiliation: Group 'Materials + Technologies', Department of Chemical and Environmental Engineering, Polytechnic School, University of the Basque Country, Pza Europa 1, 20018 Donostia-San Sebastián, Spain. Electronic address: ainara.saralegi@ehu.eus.
authors.forename: Ainara
authors.initials: A
authors.lastname: Saralegi
authors.affiliation: Laboratory of Separation and Reaction Engineering (LSRE), Associate Laboratory LSRE/LCM, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal. Electronic address: mrcosta@fe.up.pt.
authors.forename: Mário Rui P F N
authors.initials: MRPFN
authors.lastname: Costa
authors.affiliation: Laboratory of Separation and Reaction Engineering (LSRE), Associate Laboratory LSRE/LCM, Polytechnic Institute of Bragança, Campus of Santa Apolonia, 5300-253 Bragança, Portugal. Electronic address: barreiro@ipb.pt.
authors.forename: Filomena
authors.initials: F
authors.lastname: Barreiro
authors.affiliation: Group 'Materials + Technologies', Department of Chemical and Environmental Engineering, Polytechnic School, University of the Basque Country, Pza Europa 1, 20018 Donostia-San Sebastián, Spain. Electronic address: marian.corcuera@ehu.eus.
authors.forename: Maria Angeles
authors.initials: MA
authors.lastname: Corcuera
authors.affiliation: Group 'Materials + Technologies', Department of Chemical and Environmental Engineering, Polytechnic School, University of the Basque Country, Pza Europa 1, 20018 Donostia-San Sebastián, Spain. Electronic address: arantxa.eceiza@ehu.eus.
authors.forename: Arantxa
authors.initials: A
authors.lastname: Eceiza
keywords: 1,2-Ethanediamine; Heterogeneous medium reaction; Homogeneous medium reaction; Mechanical behavior; Particle size distribution; Waterborne polyurethane-ureas