Biomass Thermoplastic (Co)polyamide Elastomers Synthesized from a Fatty Dimer Acid: a Sustainable Route toward a New Era of Uniform and Bimodal Foams

Abstract

Renewable polyamides (PAs) with excellent flexibility and low-temperature foaming capability are of current interest for a wide range of industrial applications. Presently, most commercially available foams are made from fossil-based plastics, and several engineering polymers are not deployed for this, specifically bio-based ones. In this work, a new library of fully bio-based, thermoplastic PAs (denoted as DFA-BDA x HMDA y and DFA-EDA x HMDA y ) with low-temperature foaming attributes is synthesized through catalyst-free polycondensation using a renewable fatty dimer acid and different chain length diamines. The resulting PAs showed M w up to 44,191 g/mol, T d5% over 415 °C, T m from 63.1 to 103.9 °C, T g from 14.6 to 23.6 °C, strain from 386.65 ± 0.08 to 832.46 ± 0.03%, and tensile strength up to 18.57 ± 0.02 MPa. The bio-based PA samples were foamed using the scCO2 batch foaming process, and the foam cell structure was investigated with scanning electron microscopy. The results showed that the foaming morphologies could be easily tuned by changing the diamine compositions, indicating the great simplicity and tunability of this method. Consequently, we achieved foams with uniform and bimodal textures with an average diameter range of 18–198 μm for small and large cells, respectively, and the foams with various densities (0.214–0.351 g/cm3) were gained. The creation mechanism of uniform to bimodal foams was proposed and explained by a schematic illustration. All the bio-based PA foams exhibit creep recovery values above 85%. This is the first report on the manufacturing of bio-based PA foams at low foaming temperatures without toxic solvents. These outcomes provide insights into bio-based PA foam research.

Synthesis of High-Value Bio-Based Polyamide 12,36 Microcellular Foams with Excellent Dimensional Stability and Shape Recovery Properties

“…Primarily, PA12,36 comprised entangled methyl long chains in its repeating unit, which escalated chain disorder and prevented the formation of an ordered crystalline segment. Secondly, amid the ordered and disordered phases, the lengthy repeating network of PA12,36 structured kinetic obstacles of conformational entropy, which were hard to surpass [ 27 ]. As shown in the DSC cooling trace in Figure 3 a, PA12,36 had an exothermic peak at 52.3 °C, labeled as T c .…”

“…In addition, large footwear manufacturers using PA foams increase PA waste [ 27 ]. The shoe industry is a huge and rapidly developing industry [ 28 ].…”

Toward a greener future: Exploring sustainable thermoplastic elastomers

“…Other uses of fatty acids as a renewable source were independently reported in notable studies conducted by Shin and coworkers, Karak and coworker, and Ranganathan and coworkers 45,69,70 . Conjugated (or dimerized) fatty acids derived from soybean oil were shown to serve as a soft segment of TPEs, designated as DAME‐ alt ‐PPG (Figure 6).…”

“…Other uses of fatty acids as a renewable source were independently reported in notable studies conducted by Shin and coworkers, Karak and coworker, and Ranganathan and coworkers. 45,69,70 Conjugated (or dimerized) fatty acids derived from soybean oil were shown to serve as a soft segment of TPEs, designated as DAME-alt-PPG (Figure 6). 45 This multi-block type of TPE was successfully synthesized as a PLA-b-Poly(DAME-alt-PPG)-b-PLA copolymer and demonstrated to exhibit potential as a pressure-sensitive adhesive.…”

Highly Stretchable Fully Biomass Autonomic Self-Healing Polyamide Elastomers and Their Foam for Selective Oil Absorption

“…However, the integration of most autonomous self-healing elastomeric materials includes multiple steps using noxious compounds, which are undesirable for green polymer production, create challenges for scaling up production, and are not cost effective [28]. Furthermore, few fully bio-based autonomous self-healing elastomeric materials have been reported to date; published studies involve bio-based instances that are not 100% bio-based or are partially bio-based [29][30][31].…”