title: Interfacial Stabilization of Fiber-Laden Foams with Carboxymethylated Lignin toward Strong Nonwoven Networks.
abstract: Wet foams were produced via agitation and compressed air bubbling of aqueous solutions of carboxymethylated lignin (CML). Bubble size and distribution were assessed in situ via optical microscopy. Foamability, bubble collapse rate, and foam stability (half-life time) were analyzed as a function of CML concentration, temperature, pH, and air content. Dynamic changes of the CML liquid foam were monitored by light transmission and backscattering. Cellulosic fibers of different aspect ratios (long pine fibers and short birch fibers) were suspended under agitation by the liquid foams (0.6% CML in the aqueous phase) with an air (bubble) content as high as 75% in volume. Remarkably, the half-life time of fiber-laden CML foams was 10-fold higher than that of the corresponding fiber-free liquid foam. Such lignin-based foams were demonstrated, after dewatering, as a precursor for the synthesis of nonwoven, layered structures. The resulting fiber networks (paper), obtained here for the first time with lignin-based foams, were characterized for pore size distribution, lignin retention, morphology, and physical-mechanical properties (network formation quality, density, air permeability, surface roughness, and tensile and internal bond strengths). The results were compared against structures obtained from foams stabilized with an anionic surfactant (SDS) as well as those from foam-free, water-based web-laying. Remarkably, compared to SDS, the foam-formed materials produced with CML displayed better bonding and tensile strengths. Overall, CML-based foams were found to be suitable carriers of cellulosic fibers and have opened the possibility for integrating fully biobased systems in foam-forming. This is an emerging option to increase the effective solids content in the system without compromising the quality of formed nonwoven materials while achieving reductions in water and energy consumption.
authors.affiliation: Bio-based Colloids and Materials (BiCMat), Departments of Forest Products Technology, Aalto University , P. O. Box 16300, 00076 Espoo, Finland.|Departments of Forest Biomaterials and Chemical & Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Shuai
authors.initials: S
authors.lastname: Li
authors.affiliation: Bio-based Colloids and Materials (BiCMat), Departments of Forest Products Technology, Aalto University , P. O. Box 16300, 00076 Espoo, Finland.
authors.forename: Wenchao
authors.initials: W
authors.lastname: Xiang
authors.affiliation: VTT Technical Research Centre of Finland , FI-40101 Jyväskylä, Finland.
authors.forename: Marjo
authors.initials: M
authors.lastname: Järvinen
authors.affiliation: VTT Technical Research Centre of Finland , FI-40101 Jyväskylä, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Lappalainen
authors.affiliation: VTT Technical Research Centre of Finland , FI-40101 Jyväskylä, Finland.
authors.forename: Kristian
authors.initials: K
authors.lastname: Salminen
authors.affiliation: Bio-based Colloids and Materials (BiCMat), Departments of Forest Products Technology, Aalto University , P. O. Box 16300, 00076 Espoo, Finland.|Departments of Forest Biomaterials and Chemical & Bimolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Orlando J
authors.initials: OJ
authors.lastname: Rojas
keywords: air/liquid interfaces; carboxymethylated lignin; foam-forming; foamability; lignin adsorption