Continual reduction of landfill space along with rising CO 2 levels and environmental pollution, are global issues that will only grow with time if not correctly addressed. The lack of proper waste management infrastructure means gloablly commodity plastics are disposed of incorrectly, leading to both an economical loss and environmental destruction. The bioaccumulation of plastics and microplastics can already be seen in marine ecosystems causing a negative impact on all organisms that live there, ultimately microplastics will bioaccumulate in humans. The opportunity exists to replace the majority of petroleum derived plastics with bioplastics (bio-based, biodegradable or both). This, in conjunction with mechanical and chemical recycling is a renewable and sustainable solution that would help mitigate climate change. This review covers the most promising biopolymers PLA, PGA, PHA and bio-versions of conventional petro-plastics bio-PET, bio-PE. The most optimal recycling routes after reuse and mechanical recycling are: alcoholysis, biodegradation, biological recycling, glycolysis and pyrolysis respectively.

Poly(lactic acid) (PLA) was degraded to methyl lactate (Me-La) by an imino monophenolate Zn(1) 2 catalyst in the presence of tetrahydrofuran, as the solvent, and methanol, as the protic source. As well as solution-based polymerization and degradation, catalyst stability was assessed and discussed. The chemical degradation of four different commercial samples of PLA, varying in molecular weight, was studied. The effect of PLA concentration (0.05−0.2 g mL −1 ), reaction temperature (40−130 °C), and catalyst concentration (4−16 wt %) on conversion, yield, and selectivity were studied and results statistically analyzed. Mass-transfer limitations were assessed by utilizing two different PLA particle sizes and altering the stirring speed. Results revealed that the main variables affecting PLA degradation are temperature and catalyst concentration. It was possible to observe Me-La formation even at 40 °C, although the reaction times were significantly longer when compared to the highest temperatures. Conversions of 100%, as determined by 1H NMR spectroscopy and gel permeation chromatography, were possible in short times (<15 min) depending on temperature and catalyst concentration. A reaction mechanism for the production of Me-La from PLA, which considers the formation of chain-end groups as intermediates is presented and values for the kinetic constants are determined from the model. The activation energy for the initial degradation step was in the range 39−65 kJ mol −1 , decreasing with increasing catalyst loading.

As eries of Zn II complexes, based on propylenediamineS chiff bases, have been prepared and fully characterized. X-ray crystallography and NMR spectroscopy identified significant differences in the solid and solution state for the Zn II species. All complexes have been applied to the ring-opening polymerization of l-lactidew ith emphasis on industrial conditions. High conversion and good molecularw eight control were generally achievablef or Zn(A-D) 2 ,a nd high-molecular-weight poly(lactic acid) (PLA) was prepared in 1min at a1 0000:1:33 [lactide]/ [Zn]/[BnOH] loading. The more active Zn II catalysts were also appliedt oP LA degradation to alkyl lactateu nder mild conditions. Zn(A-B) 2 demonstrated high activity and selectivity in this process with PLA being consumed within 1h at 50 8C. Zn(C-D) 2 were shown to be less active, and these observations can be relatedt ot he catalysts' structure and the degradation mechanism. Initialr esultsf or the degradation of poly(ethylene terephthalate) and mixed feeds are also presented, highlighting the broader applicability of the systems presented.Owing to the inevitable depletion of fossil fuel resources, and inherentc arbon emissions, alternatives to petrochemical plastics are desperately needed. [1] Poly(lactic acid) (PLA) is apotential replacement for fossil-fuel-derived plastics used for packaging applications. [2,3] PLA has the added advantageo f being biocompatible and therefore suitable for biomedical applications. [4,5] Because it is derived from annually harvested crops, PLA is biorenewable and has promising green credentials in terms of CO 2 emissions and life-cycle assessment. [6,7] High-molecular-weight PLA is preferentially prepared from the cyclic dimer of lactic acid, lactide (LA), through ring-opening polymerization (ROP). [8] CurrentP LA research seeks to reduce energy/material input of LA monomer synthesis, [9][10][11][12] demonstrate ande lucidate stereoselective initiation [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] and prepare robust initiators to compete with Sn(Oct) 2 under industrial conditions. [30][31][32][33][34] Plastic waste andp ollution are af urther 21 st century challenge forboth academia and industry.Although PLA is biodegradable under high-temperature industrial conditions, it will not readily degrade in the natural environmenta nd therefore will contribute to the millions of tonnes of waste in landfill and in oceans. [35][36][37] End-of-life plastic waste managementi s key to tackling this issue, andi ti si mperative this is addressed for all aspiring materials such as PLA. For PLA, chemical recycling is ap articularly attractive route because it can produce value-added products such as alkyl lactates, lactic acid and acrylic acid. [38,39] These can be usefuli nt heir own right or used to reform LA, and therefore PLA, to facilitate ac ircular-economy approach. Lactic acid, for example, is regarded as ap latform chemical, and alkyl lactates are considered green solvents. [40][41][42][43][44] The conversion of PLA ...

The use of a simple, cheap and effective organocatalyst, has been exploited for the transesterification/degradation of commercial polymers.

The catalyzed methanolysis of end-of-life poly(lactic acid) (PLA) products by an ethylenediamine Zn(II) complex to form biodegradable methyl lactate was studied experimentally at 70, 90, and 110 °C. The PLA samples consisted of typical consumer waste materials, including a cup, a toy, and a threedimensional (3D) printing material. High selectivities and yields (>94%) were possible depending on temperature and reaction time. Additionally, and to develop a predictive kinetic model, kinetic parameters (pre-exponential factor and activation energies) of the PLA transesterification reaction were first obtained from virgin PLA. These parameters were subsequently used to estimate the conversion of PLA, selectivity, and yield of methyl lactate after 1 and 4 h of the reaction, and the results were compared with the experimental values of the end-of-life PLA. Despite the presence of unknown additives in the PLA waste material and uncontrolled particle size, the model was able to predict the overall conversion, selectivity, and yield to an average deviation of 5, 7, and 12%, respectively. A greater agreement between the model and experimental values is observed for the higher temperatures and the longer reaction time. Larger deviations were observed for the PLA toy, which we attribute to the presence of additives, since despite its lower molecular weight, it possessed a higher structural strength.