Production Of Polylactide Research Articles

The study of the process of production of polylactide by the interesterification of n-butyl ester of lactic acid

The study of the process of production of polylactide by the interesterification of n-butyl ester of lactic acid

Improvement of mechanical properties of polylactide by equal channel multiple angular extrusion

AbstractThe combination of high strength and toughness is always the goal of high‐performance polymer materials for industrial use. This study addresses the potentialities of a solid state equal‐channel multiple‐angular extrusion (ECMAE) in production of polylactide (PLA) with simultaneous improvement in toughness, strength, and thermal stability. Chain extender Joncryl was used to form PLA with different chain length and morphology (linear or branched PLA). It is demonstrated that simple shear deformation implemented in ECMAE results in formation of an orientation order, an increase in the degree of crystallinity, and the creation of α crystals with an increased degree of perfection. The value of the effects achieved depends on the type of PLA morphology. The best result is observed in the case of linear PLA. ECMAE‐modified linear PLA possess the better combination of strength, modulus, and ductility than the branched one. Compared with neat linear PLA, ECMAE‐modified linear PLA shows 12%, 26%, 217%, and 40% increase in tensile strength, Young's modulus, strain at break and impact strength, respectively. Additionally, the storage modulus shows an improved thermal stability of ECMAE‐modified PLA.

Characterising the sustainability performance of cyclic manufacturing processes: a hybrid manufacturing case

The drive for ever-increasing materials and energy efficiency and associated cost savings has compelled manufacturers to adopt flexible and rapid production systems. The technical limitations and sustainability concerns of conventional unit processes and sequential process flows have led to widespread adoption of advanced manufacturing processes that exhibit cyclic nature, termed cyclic manufacturing processes. While cyclic manufacturing processes enable efficient production through reduced time-to-market, lower production costs, and shorter manufacturing process chains, relatively little attention has been paid toward characterising their associated environmental, economic, and social impacts. A holistic manufacturing process modelling framework is developed to support sustainability performance characterisation of cyclic manufacturing processes. The developed framework enables model reusability, extensibility, and composability to characterise, assess, and extract product and process sustainability information. It is applied to characterise environmental impacts of a low-cost, hybrid (additive-subtractive) process for production of polylactide (PLA) parts, and compared with a conventional subtractive process (milling).

Reactive Extrusion and Magnesium (II) N-Heterocyclic Carbene Catalyst in Continuous PLA Production.

Reactive extrusion and magnesium (II) N-heterocyclic carbene catalyst are successfully employed in continuous polylactide synthesis. The possibility of using six-membered N-heterocyclic carbene adducts to act as efficient catalysts towards the sustainable synthesis of poly(l-lactide) through ring-opening polymerization of l-lactide (LA) is first investigated in bulk batch reactions. Under optimized solvent-free conditions, polylactide (PLA) of moderate to high molecular weights and excellent optical activities are successfully achieved. These promising results are further applied in the continuous production of PLA in an extruder.

Zirconium amine tris(phenolate): A more effective initiator for biomedical lactide

Here a zirconium amine tris(phenolate) is used as the initiator for the production of polylactide for biomedical applications, as a replacement for a tin initiator (usually tin octanoate). The ring opening polymerization (ROP) was carried out in the melt at 130°C. The zirconium-catalyzed PLA (PLA-Zr) required 30min, resulting in a polydispersity index (PDI) of 1.17, compared to 1h and PDI=1.77 for tin-catalyzed PLA (PLA-Sn). PLA-Zr and PLA-Sn supported osteosarcoma cell (MG63) culture to the same extent (cell number, morphology, extracellular matrix production and osteogenic function) until day 14 when the PLA-Zr showed increased cell number, overall extracellular matrix production and osteogenic function. To conclude, the reduction in reaction time, controllable microstructure and biologically benign nature of the zirconium amine tris(phenolate) initiator shows that it is a more effective initiator for ROP of polylactide for biomedical applications.

Recent Progress in Using Stereocomplexation for Enhancement of Thermal and Mechanical Property of Polylactide

Polylactide (PLA) has been receiving significant attention in biopolymer research due to its excellent biodegradability, biocompatibility and sustainability. The mass production of PLA from renewable agricultural resources has delved this green material as a top alternative to replace the petroleum-based conventional polymers. However, the inherent weaknesses of PLA in its raw state such as brittleness, low heat distortion temperature and recrystallization rate, as well as the inadequate crystallization ability and degree after fast processing have limited the competitive edge of PLA over traditional synthetic plastics in industrial use or for biomedical applications. Being different from other types of biodegradable polymers, the diverse isomeric forms of PLA have provided great opportunities for thermal and mechanical enhancement through stereocomplexation formation. In this review, we present the most recent development in thermal and mechanical enhancement of PLA via stereocomplexation of PLA in diffe...

Monomeric and dimeric Al(iii) complexes for the production of polylactide

A series of monometallic and bimetallic Al(iii) complexes with substituted naphthyl based Schiff base ligands have been prepared and characterised. When 1-aminonaphthalene based ligands were reacted with AlMe3 monometallic complexes were isolated, however, with 1,5 and 1,8-diaminonaphthalene based ligands bimetallic complexes were formed. In all cases 4-coordinate tetrahedral Al(iii) centres were observed in the solid state and in solution. There was little difference in rate of polymerisation of rac-lactide between the monometallic and bimetallic complexes based on 1,5-diaminonaphthalene. However, for the 1,8-diaminonaphthalene the complex was an order of magnitude faster than the monometallic and the analogous 1,5-system. Moreover, this complex was active at room temperature, which is rare for aluminium initiators, and PLA with a high degree (Pm = 0.82) of isotacticity was observed.

Microbial production of biopolymers from the renewable resource wheat straw.

Production of poly-ß-hydroxybutyrate (PHB) and the chemical basic compound lactate from the agricultural crop 'wheat straw' as a renewable carbon resource. A thermal pressure hydrolysis procedure for the breakdown of wheat straw was applied. By this means, the wheat straw was converted into a partially solubilized hemicellulosic fraction, consisting of sugar monomers, and an insoluble cellulosic fraction, containing cellulose, lignin and a small portion of hemicellulose. The insoluble cellulosic fraction was further hydrolysed by commercial enzymes in monomers. The production of PHB from the sugar monomers originating from hemicellulose or cellulose was achieved by the isolates Bacillus licheniformis IMW KHC 3 and Bacillus megaterium IMW KNaC 2. The basic chemical compound, lactate, a starting compound for the production of polylactide (PLA), was formed by some heterofermentative lactic acid bacteria (LAB) able to grow with xylose from the hemicellulosic wheat straw hydrolysate. Two strains were selected which were able to produce PHB from the sugars both from the hemicellulosic and the cellulosic fraction of the wheat straw. In addition, some of the LAB tested were capable of producing lactate from the hemicellulosic hydrolysate. The renewable resource wheat straw could serve as a substrate for microbiologically produced basic chemicals and biodegradable plastics.

Group 4 salalen complexes for the production and degradation of polylactide

In this communication we report the preparation of highly active catalysts for the production of polylactide and the subsequent conversion of polylactide to methyl lactate. The use of these catalysts for potential recycling applications is discussed.

Crystallographic characterisation of Ti(iv) piperazine complexes and their exploitation for the ring opening polymerisation of rac-lactide

In this paper a series of eight Ti(IV) piperazine based complexes have been prepared and fully characterised in the solid-state by X-ray crystallography and in solution via NMR spectroscopy. In the solid-state either Ti(2)(L)(O(i)Pr)(6) or Ti(2)(L)(2)(O(i)Pr)(4) were observed depending upon the nature of the starting ligand. For complexes with less sterically demanding ligands (1H(2) and 2H(2)) an equilibrium was observed: 2 Ti(2)(L)(O(i)Pr)(6) ⇔ Ti(2)(L)(2)(O(i)Pr)(4) + 2 Ti(O(i)Pr)(4). The thermodynamic properties (ΔG, ΔH and ΔS) have been investigated via variable temperature NMR spectroscopy. With more sterically demanding ligands (3-8H(2)) the Ti(2)(L)(O(i)Pr)(6) form was the most prevalent in the solid-state and in solution. These complexes have been tested for the production of polylactide under melt and solution conditions with high conversions being obtained.

New titanium and zirconium initiators for the production of polylactide

Abstract Two new group 4 initiators based on N,N′-Bis(2-hydroxybenzyl)ethylenediamine have been prepared and fully characterised via multi-nuclear NMR spectroscopy and single crystal X-ray diffraction studies. The complexes have been tested for the production of polylactide. The phenolate ligand complexes to Ti(IV) to generate the β-cis isomer in the solid-state. Whereas for Zr(IV) the isolated species (regardless of stoichiometery) is a diligated complex.

Crystallographic characterisation of novel Zn(II) silsesquioxane complexes and their application as initiators for the production of polylactide

Herein, the solid state structures of the products from the reaction of the silsesquioxane triol ( iso-C 4H 9) 7Si 7O 12(OH) 3 ( 1) with two equivalents of ZnMe 2 in both THF and toluene are reported. In both cases tetrametallic Zn(II) complexes were isolated, with toluene [( iso-C 4H 9) 7Si 7O 12] 2Zn 4Me 2 ( 2) was prepared while performing the reaction in THF the analogous complex [( iso-C 4H 9) 7Si 7O 12] 2Zn 4Me 2(THF) 2 ( 3) was formed. Both species have also been characterised via 1H, 13C{ 1H} and 29Si{ 1H} NMR spectroscopy, which confirm the solid state structures are maintained in solution. Both 2 and 3 show modest activities for the polymerisation of rac-lactide and a heterogeneous catalyst has also been prepared.

Tert-butylamidinate tin(ii) complexes: high activity, single-site initiators for the controlled production of polylactide

The tin(ii) coordination chemistry of two monoanionic N,N'-bis(2,6-diisopropylphenyl)alkylamidinate ligands is described. Complexation studies with the acetamidinate, [MeC(NAr)(2)](-), (Ar = 2,6-(i)Pr(2)C(6)H(3)) are complicated by the side formation of the bis(amidinate) tin(ii) compound, [MeC(NAr)(2)](2)Sn. By contrast, the bulkier tert-butylamidinate, [(t)BuC(NAr)(2)](-), allows tin(ii) mono-halide, -alkoxide and -amide complexes to be isolated cleanly in high yields. Thus, the reaction of [(t)BuC(NAr)(2)]H with (n)BuLi and subsequent treatment with SnCl(2) generates [(t)BuC(NAr)(2)]SnCl, in ca. 70% yield. Reactions of with LiO(i)Pr, LiNMe(2) and LiNTMS(2) afford [(t)BuC(NAr)(2)]Sn(O(i)Pr), [(t)BuC(NAr)(2)]Sn(NMe(2)), and [(t)BuC(NAr)(2)]Sn(NTMS(2)), respectively. The molecular structures of complexes are reported. Complexes, and have been investigated as initiators for the ring-opening polymerisation of rac-lactide: and display characteristics of well-controlled polymerisation initiators, but high molecular weight polymer is observed with due to inefficient initiation, a consequence of the steric bulk of the NTMS(2) unit. Polymerisations with and are faster than for the corresponding beta-diketiminate tin(ii) complexes, consistent with the more open nature of the tin(ii) coordination sphere.