This work presents one of the fastest composting aliphatic–aromatic
polyesters with a good balance of mechanical and barrier properties,
making it a sustainable alternative for low-density polyethylene in
packaging. The polyesters (PB
x
BDM
y
S) are prepared by melt polycondensation
of 1,4-butanediol (B), 1,4-benzenedimethanol (BDM), and succinic acid
(S). One composition exhibited a tensile strength of 20 ± 2 MPa,
a modulus of 150 ± 8 MPa, and a very high elongation at break
of 581 ± 46%. The low oxygen transmission rate (152 cm3·m–2·day–1·bar–1) measured at 65% relative humidity and 23 °C
confirms excellent barrier performance. A 3 μm water-borne nanocomposite
coating of glycol chitosan and sodium fluorohectorite further reduced
the gas permeability to a value of 0.75 cm3·m–2·day–1·atm–1, which is competitive with materials suitable for demanding packaging
applications such as poly(vinylidene chloride) while maintaining good
mechanical properties and high stretchability. After studying the
enzyme-catalyzed hydrolysis under controlled conditions, the full
fragmentation, assimilation, and mineralization in thermophilic, aerobic
composting could be confirmed in less than 5 weeks using a combination
of different analytical methods. The mechanism of degradation was
proven to be bulk degradation.
Poly(vinyl alcohol) (PVOH) based water‐soluble packaging with intentional disposal into wastewater provides great convenience for both households and industry. In this paper, we demonstrate with CO2 evolution testing that only insignificant fractions (~2%) of PVOH biodegrade in wastewater within 33 days. To avoid unintentional environmental build‐up and the accompanying consequences to marine life, alternative materials with a suitable balance of performance and biodegradability are needed. Until now, the barrier properties of biodegradable biopolymers could not compete with state‐of‐the‐art water‐soluble packaging materials like PVOH films. In this paper, we report on waterborne, sandwich‐structured films using hydroxypropyl methylcellulose or alginate produced with an industrially scalable slot‐die coater system. The inner layer of the film consists of a collapsed nematic suspension of high aspect ratio synthetic clay nanosheets that act as an impermeable wall. Such a film structure not only allows for barrier filler loadings capable of sufficiently reducing oxygen and water vapor permeability of alginate to 0.063 cm3 mm m−2 day−1 bar−1 and 53.8 g mm m−2 day−1 bar−1, respectively, but also provides mechanical reinforcement to the biopolymer films facilitating scalable processing. Moreover, the films disintegrated in water in less than 6 min while rapid biodegradation of the dissolved polymer was observed.
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