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In this paper, the amount of polyethylene (PE) contained in complex biodegradable polymer blends and in carrier bags claimed to be compostable was determined by thermogravimetry analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). To validate the method, polymer blends based on polylactide (PLA), poly(butylene adipate-co-butylene terephthalate) 53/47 (PBAT), native starch (NS), and calcium carbonate, with known amount of PE ranging from 0 to 10%, were prepared by melt mixing. Py-GC/MS parameters were optimized. In the first step at 400 °C, pyrolysis products originated from thermal cracking of PLA, NS and PBAT were detected. In the second step carried out at 500 °C, triplet peaks characteristic for PE, consisting of α,ω-dienes, α-alkenes and n-alkanes, were revealed together with some signals related to PBAT. TGA under nitrogen atmosphere was used to determine the amount of PE in the blends. An overestimation of about 1.2%, constant for all the blends, was revealed. The overestimation was attributed to the partial overlapping of one of the steps of degradation of the commercial PBAT and that of PE. Additionally, the analytical approach was applied in the characterization of carrier bags claimed to be compostable, recovered directly from the market. The correct determination of the composition of these biodegradable blends is important and crucial to comply with the compostability standard EN 13432-2000. According to this standard, each significant organic constituent of the packaging material must be biodegradable. “Significant” means any constituent present in more than 1% of dry weight of that material. This implies that maximum allowed PE concentration that can be detected in a compostable blend is 1%. In two commercial carrier bags, TGA revealed a component with a degradation temperature of about 455 °C corresponding to that of PE. The relative weight loss percentages of these two carrier bags have been estimated 7.6 and 14%. Optimization of the Py-GC/MS conditions allowed identifying its chemical structure. In fact, the Py-GC/MS at 500 °C provided a pyrogram that was a fingerprint for PE with triplets corresponding to linear chains of α,ω-dienes, α-alkenes and n-alkanes with chain lengths in the range of 9–36 C atoms. Overall, the results show that the combination of TGA and Py-GC/MS can be applied with practical implications.

In this study, we carried out the structural and thermal characterization of a medical-grade poly (lactide) (PLA) by SEC, TGA, DSC, NMR, ICP-MS and Py-GC/MS. Moreover, we investigated the laser-induced degradation occurring when ultrashort laser pulses (ULP) were employed to cut extremely thin polymer films prepared by solvent-casting. ULP polymer cutting technology is an interesting manufacturing process for its advantages in potential medical applications. In fact, heat transmission to the region surrounding the cuts is limited, so that the incisions are precise and the effects on the regions around them are small. In this way, the need for post-processing is reduced and ULP cutting becomes interesting for industrial applications. However, degradation induced by ULP may occur and compromise the properties of the polymer samples. To investigate this possibility, portions of PLA films, ultrashort laser cut (ULC) and uncut, were analysed by SEC, DSC, NMR and FTIR. Furthermore, PLA oligomers were studied by ESI-MS. Both SEC and NMR showed a decrease in the molecular weight. FTIR, ESI-MS and NMR spectra revealed the presence of olefin end groups originated from a β-H transfer mechanism, induced by heat and/or light (Norrish II mechanism). Additionally, the inspection of the ESI mass spectra highlighted the cleavage of ester bonds related to the Norrish I type mechanism, undetected by the other techniques.

During last decades, implantable drug delivery systems (DDS) have been developed to optimize therapeutic properties of drugs and ensure their release in a specific site. Acrylic polymers have obtained growing interest in biomedical applications for their biocompatibility and chemical properties that make them extremely versatile. In this work, we focused on the realization of polymeric systems for controlled and sustained release of betamethasone 17,21-dipropionate (BDP), a corticosteroid drug, in the treatment of the posterior eye diseases (PED). The investigated DDS were made of opportunely designed methacrylic block copolymers. Different series of methylmethacrylate/2-hydroxyethylmethacrylate (MMA/HEMA) block copolymers, with various monomeric compositions (20-60 mol% HEMA), were synthetized by Atom Transfer Radical Polymerization to find the best hydrophilic/hydrophobic ratio, able to ensure optimal kinetic release. Copolymers were characterized by nuclear magnectic resonance, size exclusion chromatography, and differential scanning calorimetry. Monitoring of drug release from films loaded with BDP was carried out by HPLC analysis. In particular, PMMA-b-PHEMA with 47 mol% of HEMA showed the best release profile to achieve the therapeutic reference dose, used in the treatment of PED (1-3 mu g/day), up to four months. Additionally, intraocular inserts with different shapes were prepared using silicon molds made by means of a 3D printer. POLYM. ENG. SCI., 57:570-578, 2017. (c) 2017 Society of Plastics Engineers