Tuning the compatibility to achieve toughened biobased poly(lactic acid)/poly(butylene terephthalate) blends

Morphologies, Compatibilization and Properties of Immiscible PLA-Based Blends with Engineering Polymers: An Overview of Recent Works

Poly(L-Lactide) (PLA), a fully biobased aliphatic polyester, has attracted significant attention in the last decade due to its exceptional set of properties, such as high tensile modulus/strength, biocompatibility, (bio)degradability in various media, easy recyclability and good melt-state processability by the conventional processes of the plastic/textile industry. Blending PLA with other polymers represents one of the most cost-effective and efficient approaches to develop a next-generation of PLA-based materials with superior properties. In particular, intensive research has been carried out on PLA-based blends with engineering polymers such as polycarbonate (PC), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT) and various polyamides (PA). This overview, consequently, aims to gather recent works over the last 10 years on these immiscible PLA-based blends processed by melt extrusion, such as twin screw compounding. Furthermore, for a better scientific understanding of various ultimate properties, processing by internal mixers has also been ventured. A specific emphasis on blend morphologies, compatibilization strategies and final (thermo)mechanical properties (tensile/impact strength, ductility and heat deflection temperature) for potential durable and high-performance applications, such as electronic parts (3C parts, electronic cases) to replace PC/ABS blends, has been made.

The Development of Sustainable Polyethylene Terephthalate Glycol-Based (PETG) Blends for Additive Manufacturing Processing-The Use of Multilayered Foil Waste as the Blend Component

The polymer foil industry is one of the leading producers of plastic waste. The development of new recycling methods for packaging products is one of the biggest demands in today's engineering. The subject of this research was the melt processing of multilayered PET-based foil waste with PETG copolymer. The resulting blends were intended for additive manufacturing processing using the fused deposition modeling (FDM) method. In order to improve the properties of the developed materials, the blends compounding procedure was conducted with the addition of a reactive chain extender (CE) and elastomeric copolymer used as an impact modifier (IM). The samples were manufactured using the 3D printing technique and, for comparison, using the traditional injection molding method. The obtained samples were subjected to a detailed characterization procedure, including mechanical performance evaluation, thermal analysis, and rheological measurements. This research confirms that PET-based film waste can be successfully used for the production of filament, and for most samples, the FDM printing process can be conducted without any difficulties. Unfortunately, the unmodified blends are characterized by brittleness, which makes it necessary to use an elastomer additive (IM). The presence of a semicrystalline PET phase improves the thermal resistance of the prepared blends; however, an annealing procedure is required for this purpose.

Conductive Plastics from Al Platelets in a PBT-PET Polyester Blend Having Co-Continuous Morphology

Conductive plastics are made by placing conductive fillers in polymer matrices. It is known that a conductive filler in a binary polymer blend with a co-continuous morphology is more effective than in a single polymer, because it aids the formation of a 'segregated conductive network'. We embedded a relatively low-cost conductive filler, aluminium nano platelets, in a 60/40 PBT/PET polymer blend. While 25 vol.% of the Al nanoplatelets when placed in a single polymer (PET) gave a material with the resistivity of an insulator (1014 Ωcm), the same Al nano platelets in the 60/40 PBT/PET blend reduced the resistivity to 7.2 × 107 Ωcm, which is in the category of an electrostatic charge dissipation material. While PET tends to give amorphous articles, the 60/40 PBT/PET blends crystallised in the time scale of the injection moulding and hence the conductive articles had dimensional stability above the Tg of PET.

Recent advances in additive manufacturing of engineering thermoplastics: challenges and opportunities

There are many limitations within three-dimensional (3D) printing that hinder its adaptation into industries such as biomedical, cosmetic, processing, automotive, aerospace, and electronics. The disadvantages of 3D printing include the inability of parts to function in weight-bearing applications, reduced mechanical performance from anisotropic properties of printed products, and limited intrinsic material performances such as flame retardancy, thermal stability, and/or electrical conductivity. Many of these shortcomings have prevented the adaptation of 3D printing into product development, especially with few novel researched materials being sold commercially. In many cases, high-performance engineering thermoplastics (ET) provide a basis for increased thermal and mechanical performances to address the shortcomings or limitations of both selective laser sintering and extrusion 3D printing. The first strategy to combat these limitations is to fabricate blends or composites. Novel printing materials have been implemented to reduce anisotropic properties and losses in strength. Additives such as flame retardants generate robust materials with V0 flame retardancy ratings, and compatibilizers can improve thermal or dimensional stability. To serve the electronic industry better, the addition of carbon black at only 4 wt%, to an ET matrix has been found to improve the electrical conductivity by five times the magnitude. Surface modifications such as photopolymerization have improved the usability of ET in automotive applications, whereas the dynamic chemical processes increased the biocompatibility of ET for medical device materials. Thermal resistant foam from polyamide 12 and fly ash spheres were researched and fabricated as possible insulation materials for automotive industries. These works and others have not only generated great potential for additive manufacturing technologies, but also provided solutions to critical challenges of 3D printing.

Melt Rheological Behavior and Morphology of Poly(ethylene oxide)/Natural Rubber-graft-Poly(methyl methacrylate) Blends

The influence of morphology on the rheological properties of poly(ethylene oxide) (PEO) and natural rubber-graft-poly(methyl methacrylate) (NR-g-PMMA) blends in the melt was investigated. The blends were prepared at different blend compositions by a solution-casting method. Linear viscoelastic shear oscillations measurements were performed in order to determine the elastic and viscous properties of the blends in the melt. The rheological results suggested that the blending of the two constituents reduced the elasticity and viscosity of the blends. The addition of an even small amount of NR-g-PMMA to PEO changed the liquid-like behavior of PEO to more solid-like behavior. Morphological investigations were carried out by optical microscopy to establish the relationship between morphology and melt viscosity. Depending on the blend compositions and viscosities, either droplet-matrix or co-continuous morphologies was observed. PEO/NR-g-PMMA blends exhibited a broad co-continuity range, and phase inversion was suggested to occur at the PEO/NR-g-PMMA blend with a mass ratio of 60/40 (m/m), when NR-g-PMMA was added to PEO as a matrix.

Improving the Toughness and Thermal Resistance of Polyoxymethylene/Poly(lactic acid) Blends: Evaluation of Structure-Properties Correlation for Reactive Processing

The study focuses on the development of polyoxymethylene (POM)/poly(lactic acid) (PLA) blends with increased impact and thermal resistance. The study was conducted in two phases; in the first part, a series of unmodified blends with PLA content of 25, 50, and 75 wt.% was prepared, while the second part focused on the modification of the PLA/POM (50/50) blends. An ethylene/butyl acrylate/glycidyl methacrylate terpolymer (E/BA/GMA) elastomer (EBA) was used to improve the impact strength of the prepared blends, while reactive blending was used to improve interfacial interactions. We used a multifunctional epoxy chain extender (CE) as the compatibilizer. Static tensile tests and notched Izod measurement were used to evaluate the mechanical performance of the prepared samples. The thermomechanical properties were investigated using dynamic mechanical thermal analysis (DMTA) analysis and heat deflection temperature (HDT)/Vicat softening temperature (VST) methods. The crystallinity was measured using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXS) measurements, while the rheology was evaluated using a rotational rheometer. The paper also includes a structure analysis performed using the SEM method. The structural tests show partial miscibility of the POM/PLA systems, resulting in the perfect compatibility of both phases. The impact properties of the final blends modified by the EBA/CE system were found to be similar to pure POM resin, while the E modulus was visibly improved. Favorable changes were also noticeable in the case of the thermomechanical properties. The results of most of the conducted measurements and microscopic observations confirm the high efficiency of the reaction for PLA as well as for the modified POM/PLA mixtures.

Strategy To Improve Printability of Renewable Resource-Based Engineering Plastic Tailored for FDM Applications

This work features the first-time use of poly(trimethylene terephthalate) (PTT), a biobased engineering thermoplastic, for fused deposition modeling (FDM) applications. Additives such as chain extenders (CEs) and impact modifiers are traditionally used to improve the processability of polymers for injection molding; as a proof of concept for their use in FDM, the same strategies were applied to PTT to improve its printability. The filament processing conditions and printing parameters were optimized to generate complete, warpage-free samples. The blends were characterized through physical, thermal, viscoelastic, and morphological analyses. In the optimal blend (90 wt % PTT, 10 wt % impact modifier, and 0.5 phr CE), the filament diameter was improved by ∼150%, the size of the spherulites significantly decreased to 5% of the ∼26 μm spherulite size found in neat PTT, and the melt flow index decreased to ∼4.7 g/10 min. From this blend, FDM samples with a high impact performance of ∼61 J/m were obtained, which are comparable to other conventional FDM thermoplastics. The ability to print complete and warpage-free samples from this blend suggests a new filament feedstock material for industrial and home-use FDM applications. This paper discusses methods to improve hard-to-print polymers and presents the improved printability of PTT as proof of these methods' effectiveness.

One-pot route to graft long-chain polymer onto silica nanoparticles and its application for high-performance poly(l-lactide) nanocomposites

A facile “one-pot” synthetic route to modify SiO₂ nanoparticles with long-chain polymer was developed. The structure and morphology of SiO₂ grafted with poly(l-lactide) (SiO₂-g-PLA) were characterized by FTIR, TGA, GPC, and TEM. Furthermore, a series of PLA/SiO₂-g-PLA nanocomposites were prepared with different nanofiller loadings, and their related performances were investigated. As an effective nucleating agent, the SiO₂-g-PLA had a positive effect to improve the crystallization rate and increase the crystallinity. Meanwhile, the PLA nanocomposites presented outstanding mechanical properties including excellent toughness and high stiffness. In addition, the PLA materials kept good transparency with less than 3 wt% nanofillers. Overall, this work provides a useful method for preparing high-performance polymer nanocomposites.

A facile “one-pot” synthetic route is used to modify SiO₂ nanoparticles with a long-chain polymer, and to prepare high-performance poly(l-lactide) nanocomposites.