Interest in biodegradable polymers is surging among consumers, businesses, and governments as the accumulation of waste from single-use, petrochemical-based, and non-biodegradable plastics has skyrocketed since the 1960s, with flexible plastics constituting a major part of this surge. However, one major challenge with biodegradable alternatives is their inability to match traditional petrochemical plastics' oxygen and moisture barrier properties, which is critical for maintaining equivalent shelf life. This dissertation addresses several pivotal challenges, presenting innovative solutions within biodegradable polymers. Our research achieved breakthroughs in the extrusion casting of stereocomplex-poly(lactic acid)—SC-PLA films and blends of poly(L-lactic acid)/ poly(D-lactic acid)—PLLA/PDLA in varying ratios, which were not previously documented. We explored the effects of annealing these films from 5 to 30 minutes to enhance crystallization and improve moisture barrier properties. Notably, PDLA served as an effective nucleating agent, significantly accelerating crystallization in blends with as little as 15% PDLA. Further investigations revealed the interplay between density, crystallinity, and barrier properties of PLLA, PDLA, and their blends under varying annealing conditions. Amorphous film samples displayed densities between 1,230 ± 6 and 1,243 ± 2 kg/m3, while semi-crystalline samples showed higher densities of 1,250 ± 8 to 1,257 ± 9 kg/m3. Changes in density and crystallinity were analyzed, with findings indicating that homocomplex crystals formed at shorter annealing times exhibit higher densities than stereocomplex crystals forming at longer durations. An innovative lamination technique involving base layers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or SC-PLA, coated with a biodegradable polyvinyl alcohol and nanoclay mixture, was developed. This structure was tested for its moisture vapor transmission rate (MVTR) and oxygen transmission rate (OTR), demonstrating promising barrier properties suitable for biodegradable packaging solutions. The MVTR ranged from 20 to 30 g/(m2·d), and the OTR ranged from 54 to 69 cc/(m2·d). We showed that optimizing the structure could obtain either a maximized MVTR of 10 g/(m2 · d) at 38 °C/90% RH or a maximized OTR of 14.46 cc/(m2·d) at 23 °C/50% RH, both exceptional for a clear biodegradable structure without PVDC or metallization, showcasing low permeability for several biodegradable products. Finally, we assessed the SC-PLA films and the blends’ biodegradability in simulated composting conditions over 120 days. This test was conducted for 120 days of PLLA, PDLA, PLLA/PDLA 50-50, 30-70, and 70-30 films. This study is the first to report on the biodegradation behavior of these materials, particularly highlighting the rapid biodegradation of annealed PLLA/PDLA 50-50 blends compared to slower rates in higher PDLA content films. This is followed by films with higher PDLA content, such as the 30-70 blend with most PDLA. No data on the biodegradation of SC-PLA or PDLA in compost conditions had previously been reported. This comprehensive test provides reassurance and confidence in the biodegradability of our materials. This dissertation contributes significant insights into developing high-performance, biodegradable film structures that offer viable alternatives to traditional plastics and align with global sustainability goals.
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