Reaction Mechanism and Mechanical Property Improvement of Poly(Lactic Acid) Reactive Blending with Epoxy Resin.

Polylactic acid (PLA) was melt-blended with epoxy resin to study the effects of the reaction on the mechanical and thermal properties of the PLA. The addition of 0.5% (wt/wt) epoxy to PLA increased the maximum tensile strength of PLA (57.5 MPa) to 67 MPa, whereas the 20% epoxy improved the elongation at break to 12%, due to crosslinking caused by the epoxy reaction. The morphology of the PLA/epoxy blends showed epoxy nanoparticle dispersion in the PLA matrix that presented a smooth fracture surface with a high epoxy content. The glass transition temperature of PLA decreased with an increasing epoxy content owing to the partial miscibility between PLA and the epoxy resin. The Vicat softening temperature of the PLA was 59 °C and increased to 64.6 °C for 0.5% epoxy. NMR confirmed the reaction between the -COOH groups of PLA and the epoxy groups of the epoxy resin. This reaction, and partial miscibility of the PLA/epoxy blend, improved the interfacial crosslinking, morphology, thermal properties, and mechanical properties of the blends.

Presence of microplastics in water, sediments and fish species in an urban coastal environment of Fiji, a Pacific small island developing state.

Microplastics (MP) in the marine environment are widely reported. However, MP occurrence in some geographical areas such as from Small Island Developing States (SIDS) is missing. The main aim of this study was to assess MP levels in the urban coastal environment of Suva, the capital of the Republic of Fiji. Microplastics were measured from surface water, sediments and fish gastrointestinal tracts (GI) from three sites adjacent to Suva. In addition, an evaluation on the contribution from the local sewage treatment plant to MP levels was undertaken. In general, low levels of MP in water and sediments were detected, but significant differences were observed among sites. The sewage treatment plant was shown to contribute to MP levels in sediment but not in water. Species ingestion of MP was high and associated with MP in sediments. Fibres and fragments were the predominant type of MP, and fifteen different polymers were detected, with higher percentages of polyethylene, latex and polypropylene. In conclusion, MP were found in Suva coastal environment and these MP were associated to land based human activities.

Structural Changes in Poly(trimethylene adipate) and Poly(trimethylene succinate) During Melt Crystallization Studied Using In Situ Infrared Spectroscopy.

This paper investigates the structural changes occurring in poly(trimethylene adipate) (PTAd) and poly(trimethylene succinate) (PTSu) during melt crystallization using differential scanning calorimetry (DSC) and in situ Fourier transform infrared (FT-IR) spectroscopy. Cooling thermograms revealed that PTAd had a faster crystallization rate than PTSu. Infrared (IR) bands of the two polyesters were assigned by correlating with the IR bands of polymers containing the trimethylene and the diacid segments. The bands at 1478, 1459, 1393, and 1364 cm-1 in PTAd and 1475, 1459, 1393, and 1361 cm-1 in PTSu were designated to the CH2 of the trimethylene segment. Changes in the IR band absorbance intensities of the CH2 and the C-O-C groups were monitored with time during melt crystallization. Structural changes of the trimethylene and diacid segments of PTAd occurred synchronously, while in PTSu the two segments changed sequentially. Normalized band intensities showed a time lag between the trimethylene and succinic acid segments. The acid segment showed a faster change compared to the trimethylene segment. Fourier transform infrared spectroscopy is shown to be a useful technique to study conformational changes during crystallization in polymers.