PLLA/HIPS bioblends compatibilized by PLA-b-PS block

Journal of Applied Polymer Science, 2013

ABSTRACT Diblock and triblock copolymers of poly-L-lactide (PLLA) and polystyrene (PS) were synthesized and the mechanical properties of these copolymers studied. Free radical polymerization of styrene in the presence of 2-mercaptoethanol as functional chain transfer agent produced mono-functionalized PS-blocks which were used as macroinitiators in the subsequent ring opening polymerization (ROP) of L-lactide to produce the diblock copolymers. Furthermore a α-ω-bishydroxyl functionalized PS-block was synthesized by RAFT, which was then engaged as bifunctional initiator for the ROP of L-lactide to provide the triblock copolymers PLLA-PS-PLLA. Through the copolymerisation and high molar masses, it was possible to achieve an improved mechanical property profile, compared with pure PLLA, or the analogous blends of PLLA and PS. A weight fraction of PS of 10–30% was found to be the optimal range for improving the heat deflection temperature (HDT), as well as mechanical properties such as ultimate tensile strength or elongation at break. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Macromolecules, 2015

Block copolymers consisting of a polyethylene block and a polar polymer block are interesting structures for the compatibilization of polyethylene/polar polymer blends or polyethylene-based composites. Since the synthesis of polyethylenebased block copolymers is an elaborate process, diblock copolymers consisting of "polyethylene-like" poly-(pentadecalactone) (PPDL) and poly(L-lactide) (PLLA) were synthesized using a one-pot, sequential-feed ring-opening polymerization of pentadecalactone (PDL) and L-lactide (LLA). The peculiar activity of the used aluminum salen catalysts yielded a block copolymer consisting of two blocks with both a high dispersity, as a result of intrablock transesterification. Interestingly, interblock transesterification was effectively suppressed. The obtained poly(PDL-block-LLA) of various block lengths showed coincidental crystallization of the two blocks with an associated microphase-separated morphology, in which PLLA spheres with a high dispersity are distributed within the PPDL matrix. The complex morphologies is believed to arise from the presence of a whole range of block sizes as a consequence of the large dispersity of both blocks. The application of these block copolymers as compatibilizers for high density polyethylene (HDPE)/PLLA blends led to a clear change in blend morphology and a steep decrease in particle size of the dispersed phase. Furthermore, addition of the block copolymers to blends of linear low density polyethylene (LLDPE) and PLLA led to a significant increase in adhesion between the two phases. For both HDPE/PLLA and LLDPE/PLLA blends, the compatibilization efficiency of the poly(PDL-block-LLA) increased when the length of the PPDL block was increased. The presented results clearly show that PPDL can function as a substituent for various types of polyethylene, which opens up a new method for compatibilizing polyethylene with polar polymers using easy attainable "PE-like" block copolymers.

Effect of Poly(ε-caprolactone-b-tetrahydrofuran) Triblock Copolymer Concentration on Morphological, Thermal and Mechanical Properties of Immiscible PLA/PCL Blends, 2019

In this study a low molecular weight triblock copolymer derived from ε-caprolactone and tetrahydrofuran was used as a non-reactive compatibilizer of immiscible PLA/PCL blends. Ternary blends with 0, 1.5 wt%, 3 wt% and 5 wt% copolymer and about 75 wt% PLA were prepared by single screw extrusion and characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile and Izod impact testing. SEM micrographs showed that the size of the dispersed PCL domains was practically constant regardless of copolymer concentration. This result can be explained by the low shear rate employed during processing step and a decrease of PCL viscosity by presence of the triblock copolymer. However, when the copolymer concentration increased, strain at break of PLA/PCL blends also increased. PLA/PCL blend with 0 wt% copolymer presented 2% strain at break, whereas PLA/PCL blend with 5 wt% copolymer exhibited 90%.

Macromolecules, 2015

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European Polymer Journal, 2009

Polylactide (PLA) is a potential candidate for the partial replacement of petrochemical polymers because it is biodegradable and produced from annually renewable resources. Characterized by its high tensile strength, unfortunately the brittleness and rigidity limit its applicability. For a great number of applications such as packaging, fibers, films, etc., it is of high interest to formulate new PLA grades with improved flexibility and better impact properties.

2011

Pengoptimunan gaulan poli(L-laktik asid) (PLLA) telah dihasilkan melalui pengaulan polimer bio liat seperti poli(kaprolakton) (PCL), poli(butil suksinat-ko-L-laktad) (PBSL) dan poli(butilena suksinat-ko-e-kaprolakton) (PBSC) dan penambahan agen perserasian seperti lysine triisosianat (LTI) dan tiga blok kopolimer polietilena oksida - polipropilena oksida - polietilena oksida (PEO-PPO-PEO). Optimization of poly(L-lactic acid) (PLLA) blends was carried out by blending with ductile biopolymers such as poly(ε-caprolactone) (PCL), poly(butylene succinate-co-L-lactate) (PBSL) and poly(butylene succinate-co-e-caprolactone) (PBSC) and addition of compatibilizer such as lysine triisocyanate (LTI) and polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) triblock copolymer

ACS Omega

Well-defined six-arm star-branched biodegradable block copolymers of L-lactide and ε-caprolactone were prepared using controlled ring-opening polymerization and a sequential monomer addition method using dipentaerythritol as the initiator core and organocatalysts at low temperatures in solution. Sequence of enchainment was changed by reversing the order of monomer addition giving, either, a crystalline PLA block or an amorphous PCL block as the outer segment. Well-defined six-arm poly(ε-caprolactone-b-L-lactide, 6s-PCL-b-PLA) block copolymers were obtained with a range of segment molecular weights. However, in the case of six-arm poly(L-lactide-b-ε-caprolactone, 6s-PLA-b-PCL), disruption of the block structure was observed on account of competing transesterification reactions accompanying a chaingrowth reaction. Such sequence-controlled block copolymers showed interesting phase morphologies, as evidenced by differential scanning calorimetry (DSC) studies. 6s-PCL-b-PLA showed two glass-transition temperatures and two melting temperatures characteristic of the amorphous and crystalline blocks. 6s-PCL-b-PLA and 6s-PLA-b-PCL with different segment chain lengths were solution blended (10 wt %) with a commercially sourced PLA. All the blends were highly transparent. The structure and properties of the blend were examined by DSC, measurement of mechanical properties, and scanning electron microscopy. The results show that a phaseseparated 6s-PCL-b-PLA copolymer results in two-to threefold improvement in tensile toughness without the loss of modulus. A possible hypothesis for the mechanism of tensile toughness in the blend has been proposed.

Polymer, 2011

A wood hydrolysate derived hemicellulose-rich fraction was functionalized with L-lactide oligomers through a ring opening polymerization mediated grafting-from reaction. The graft copolymer was designed to act as a compatibilizer in hydrolysate/poly(L-lactide) (PLLA) blend films. The PLLA addition improved the tensile behavior of the hydrolysate matrix and this effect was enhanced further by the addition of minor amounts of the synthesized compatibilizer. With only 1% (w/w) of compatibilitzer the compatibility between the components and the homogeneity of the resulting films were greatly improved with an increase of strain-at-break with up to 400%. The oxygen permeability of the blend films was markedly reduced with the addition of wood hydrolysate, compared to the barrier properties of pure PLLA, an effect that is not significantly compromised when compatibilizer amounts are kept small.

Zenodo (CERN European Organization for Nuclear Research), 2023

The mole (Talpa europea) has a long history of use as medicament beginning with rather sparse records in classical and medieval writings. The number and diversity of mole therapies expanded during early modern times. This, the first survey of mole-containing medicines in scientific medical literature, reveals that they were used to treat, amongst other ailments, rheumatism, arthritis, hernias, prolapse, leprosy, epilepsy, wounds, and a wide range of dermal, dental, ocular and aural conditions. Preparations were generally quite simple, comprising either isolated organs from the animal (liver, blood, teeth, skin) or the whole carcass, usually in the form of a pulverised ash.