Abstract
A bio-derived monomer called 2,3:4,5-di-O-isopropylidene-galactarate acid/ester (GalXMe) has great potential in polymer production. The unique properties of this molecule, such as its rigidity and bulkiness, contribute to the good thermal properties and appealing transparency of the material. The main problem, however, is that like other biobased materials, the polymers derived thereof are very brittle. In this study, we report on the melt blending of GalXMe polyamides (PAs) with different commercial PA grades using extrusion as well as blend characterization. Biobased PA blends showed limited to no miscibility with other polyamides. However, their incorporation resulted in strong materials with high Young moduli. The increase in modulus of the prepared GalXMe blends with commercial PAs ranged from up to 75% for blends with aliphatic polyamide composed of 1,6-diaminohexane and 1,12-dodecanedioic acid PA(6,12) to up to 82% for blends with cycloaliphatic polyamide composed of 4,4′-methylenebis(cyclohexylamine) and 1,12-dodecanedioic acid PA(PACM,12). Investigation into the mechanism of blending revealed that for some polyamides a transamidation reaction improved the blend compatibility. The thermal stability of the biobased PAs depended on which diamine was used. Polymers with aliphatic/aromatic or alicyclic diamines showed no degradation, whereas with fully aromatic diamines such as p-phenylenediamine, some degradation processes were observed under extrusion conditions (260/270 °C).
Highlights
Carbohydrate-based monomers constitute a very promising replacement for fossil-based building blocks by providing a biobased alternative to some commonly used monomers [1,2,3,4], and by offering new functionalities [5,6]
GalXMe blends with commercial PAs ranged from up to 75% for blends with aliphatic polyamide composed of 1,6-diaminohexane and 1,12-dodecanedioic acid PA(6,12) to up to 82% for blends with cycloaliphatic polyamide composed of 4,40 -methylenebis(cyclohexylamine) and 1,12-dodecanedioic acid PA(PACM,12)
Like other carbohydrate-based polymers, these polyamides have the tendency to be brittle at room temperature (Figure 1) [1,10]
Summary
Carbohydrate-based monomers constitute a very promising replacement for fossil-based building blocks by providing a biobased alternative to some commonly used monomers [1,2,3,4], and by offering new functionalities [5,6]. The acetal of galactaric acid (GalX) is used for polyamide synthesis and is obtained from sugar beet pulp, a second-generation feedstock which does not compete with the food industry [7,8]. Like other carbohydrate-based polymers, these polyamides have the tendency to be brittle at room temperature (Figure 1) [1,10]. As for biobased poly(lactic acid) (PLA), the mechanical performance of these polymers needs to be further improved. PLA is an extensively researched biobased polyester with high potential for wide-spread applications. It possesses poor ductility, with an elongation at break of only around 3% [11,12,13]
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