Selective dispersion of carbon nanotubes and nanoclay in biodegradable poly(ε-caprolactone)/poly(lactic acid) blends with improved toughness, strength and thermal stability

Effect of hydrophobic modification of chitin nanocrystals on role as anti-nucleator in the crystallization of poly(ε-caprolactone)/polylactide blend

Biodegradable polymer blends filled with rod-like polysaccharide nanocrystals have attracted much attention because each component in this type of ternary composites is biodegradable, and the final properties are more easily tailored comparing to those of binary composites. In this work, chitin nanocrystals (ChNCs) were used as nanofiller for the biodegradable poly(ε-caprolactone) (PCL)/polylactide (PLA) immiscible blend to prepare ternary composites for a crystallization study. The results revealed that the crystallization behavior of PCL/PLA blend matrices strongly depended on the surface properties of ChNCs. Non-modified ChNCs and modified ChNCs played completely different roles during crystallization of the ternary systems: the former was inert filler, while the latter acted as anti-nucleator to the PCL phase. This alteration was resulted from the improved ChNC-PCL affinity after modification of ChNCs, which was due to the 'interfacial dilution effect' and the preferential dispersion of ChNCs. This work presents a unique perspective on the nucleation role of ChNCs in the crystallization of immiscible PCL/PLA blends, and opens up a new application scenario for ChNCs as anti-nucleator.

Improving flame retardant and electromagnetic interference shielding properties of poly(lactic acid)/poly(ε-caprolactone) composites using catalytic imidazolium modified CNTs and ammonium polyphosphate

The flame retardants and electromagnetic interference (EMI) shielding performance were enhanced by using imidazolium-functionalized polyurethane (IPU) modified multi-walled carbon nanotubes (CNTs) and ammonium polyphosphate (APP) for polylactic acid (PLA)/polycaprolactone (PCL) composites. The PLA/PCL/10APP/8CNT/1.6IPU composite containing 10 wt% APP and 8 wt% imidazolium modified CNTs reached the limiting oxygen index (LOI) value of 30.3 % and passed the V-0 rating in UL-94 tests. Moreover, the peak of the heat release rate (pHRR) and total heat release (THR) for this composite reached around 302 kW/m2 and 64 KJ/m2, which were decreased by 39.1 % and 15.8 % compared with that of PLA/PCL/10APP composite. The improved flame retardancy was attributed to the interplay of catalytic, barrier, and condensed char forming of imidazolium-modified CNTs and APP. IPU catalyzed the charring effect of the polymer matrix during combustion and regulated the migration of more CNTs to disperse at the two-phase interface. The dispersion of imidazolium-modified CNTs and co-continuous phase structure of the composites can establish continuous conductive pathways. The PLA/PCL/APP/CNT/IPU composite obtained a higher conductivity compared to the PLA/PCL/APP/CNT composite and whose EMI SE reached 33.9 dB, which is a promising candidate for next-generation sustainable and protective plastics.

Phase morphology, rheological behavior and mechanical properties of supertough biobased poly(lactic acid) reactive ternary blends

Poly(lactic acid) (PLA) is one of the most promising bio-based polyester with great potential to replace for the petroleum-based polymers, which can significantly reduce greenhouse gas emissions. However, the inherent brittleness of PLA seriously restricts its broad applications. Herein, PLA/poly(ε-caprolactone) (PCL)/ethylene methyl acrylate-glycidyl methacrylate (EMA-GMA) ternary blends with different phase structures were prepared through reactive blending. The reactions between the epoxy groups of EMA-GMA and the carboxyl and hydroxyl end groups of PLA and PCL and were evidenced from the Fourier transform infrared spectroscopy, dynamic mechanical analysis and rheological results. The atomic force microscopy (AFM) images clearly revealed the formation of stack structure of the PCL and EMA-GMA minor phases in PLA/PCL/EMA-GMA (80/15/5) blend, and core-shell particle structures in PLA/PCL/EMA-GMA (80/10/10) and (80/5/15) blends. In terms of elongation at break and impact toughness, PLA/PCL/EMA-GMA (80/5/15) blend presents the best properties among all the compositions. Moreover, it also behaved excellent stiffness-toughness balance. The toughening mechanism can be ascribed to the formation of core-shell structure and the existence of interfacial adhesion in the ternary blends. This work can provide guide for the preparation and design of PLA-based partially renewable supertough materials that can compete with conventional petro-derived plastics.

Super-Tough and Biodegradable Poly(lactide-co-glycolide) (PLGA) Transparent Thin Films Toughened by Star-Shaped PCL-b-PDLA Plasticizers

To obtain fully degradable and super-tough poly(lactide-co-glycolide) (PLGA) blends, biodegradable star-shaped PCL-b-PDLA plasticizers were synthesized using natural originated xylitol as initiator. These plasticizers were blended with PLGA to prepare transparent thin films. Effects of added star-shaped PCL-b-PDLA plasticizers on mechanical, morphological, and thermodynamic properties of PLGA/star-shaped PCL-b-PDLA blends were investigated. The stereocomplexation strong cross-linked network between PLLA segment and PDLA segment effectively enhanced interfacial adhesion between star-shaped PCL-b-PDLA plasticizers and PLGA matrix. With only 0.5 wt% addition of star-shaped PCL-b-PDLA (Mn = 5000 g/mol), elongation at break of the PLGA blend reached approximately 248%, without any considerable sacrifice over excellent mechanical strength and modulus of PLGA.

Effect of Polydopamine Coating of Cellulose Nanocrystals on Performance of PCL/PLA Bio-Nanocomposites

In bio-nanocomposites with a poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) matrix with neat and polydopamine (PDA)-coated cellulose nanocrystals (CNCd), the use of different mixing protocols with masterbatches prepared by solution casting led to marked variation of localization, as well as reinforcing and structure-directing effects, of cellulose nanocrystals (CNC). The most balanced mechanical properties were found with an 80/20 PLA/PCL ratio, and complex PCL/CNC structures were formed. In the nanocomposites with a bicontinuous structure (60/40 and 40/60 PLA/PCL ratios), pre-blending the CNC and CNCd/PLA caused a marked increase in the continuity of mechanically stronger PLA and an improvement in related parameters of the system. On the other hand, improved continuity of the PCL phase when using a PCL masterbatch may lead to the reduction in or elimination of reinforcing effects. The PDA coating of CNC significantly changed its behavior. In particular, a higher affinity to PCL and ordering of PLA led to dissimilar structures and interface transformations, while also having antagonistic effects on mechanical properties. The negligible differences in bulk crystallinity indicate that alteration of mechanical properties may have originated from differences in crystallinity at the interface, also influenced by presence of CNC in this area. The complex effect of CNC on bio-nanocomposites, including the potential of PDA coating to increase thermal stability, is worthy of further study.

Preparation and mechanism of lightweight wood fiber/poly(lactic acid) composites

The high density and poor thermal insulation of traditional wood-plastic composites limited the application in the field of building materials. In this paper, wood fiber (WF) and PLA were used as raw materials and azodicarbonamide was used as the foaming agent. Lightweight WF/PLA composites were prepared by the hot-pressing foaming method, aiming to obtain renewable, low-density material with high strength-to-weight ratio and thermal insulation performance. The results showed that after adding 20 % WF into PLA, the cell morphology was excellent and the cell size was uniform. The magnification reached the minimum value of 0.36 g/cm³ and the foaming magnification was 3.42 times. The impact strength and compressive strength were 3.16 kJ/m³ and 4.12 MPa, its comprehensive mechanical properties were outstanding. The thermal conductivity of foamed materials was 0.110-0.148 (W/m·K), which was significantly lower than that of unfoamed materials and common wood. Its excellent mechanical properties and thermal insulation can be suitable for application in the construction field to replace traditional wood.

A review of trends in the development of bionanocomposites from lignocellulosic and polyacids biomolecules as packing material making alternative: A bibliometric analysis

Contamination caused by the accumulation of petrochemical-based plastics has reached worrying magnitudes and led to the development of biopolymers as an option to mitigate the problem. This work thus presents a bibliometric analysis of all that concerns the development of such bionanocomposite materials, using ScientoPy and SciMAT software to establish associations between the number of published documents, countries, institutions and most relevant topics. The bionanocomposites topic was found to throw up the biggest number of documents associated (2008) with the different types of raw materials and methods used to obtain nanoparticles and their combination with biopolymeric materials, the result known as a "bionancomposite*". Analysis of the documents related to the application for development of packaging materials from biological molecules, carbohydrate polymers, compounds, conjugates, gels, glucans, hydrogels, membranes, mucilage (source unspecified), mucoadhesives, paper, polymers, polysaccharide, saccharides etc, is also presented, emphasizing mechanical, thermal and barrier properties, which, due to the inclusion of nanoparticles mainly from natural sources of cellulose, show increases of up to 30%. The inclusion of nanoparticles, especially those derived from cellulose sources, generally seeks to increase the properties of bionanocomposite materials. Regarding an increase in mechanical properties, specifically tensile strength, inclusions at percentages not exceeding 10 wt% can register increases that exceed 30% were reported.

Biodegradable polycaprolactone (PCL) based polymer and composites

Polycaprolactone (PCL) is a biodegradable polyester that has advantages over other biopolymers, making it an extensively researched polymer. PCL is a hydrophobic, slow-degrading, synthetic polymer making it particularly interesting for the preparation of long-term implantable devices and a variety of drug delivery systems. Recently, PCL has been used for additional applications including food packaging and tissue engineering. In this chapter, the processing methods and characterization of PCL will be discussed. The chapter will summarize the synthesis of poly(α-hydroxy acid) and the ring-opening polymerization of PCL. Discussion on the biodegradability of PCL will be reviewed. The biomedical applications of PCL, such as, drug-delivery systems, medical devices, and tissue engineering will be also summarized. Finally, the chapter will conclude with a characterization section outlining recent studies focusing on PCL based composites and films.