Biodegradable poly(lactic acid)/chitosan-modified montmorillonite nanocomposites: Preparation and characterization

Effect of Bentonite on the Electrical Properties of a Polylactide-Based Nanocomposite

In this paper, a novel polylactide-based nanocomposite with the addition of bentonite as a filler, Fusabond, and glycerine as a compatibilizer and plasticizer, were prepared and investigated. Four samples with different contents of bentonite (1, 5, 10, and 15 wt.%), as well as three samples without fillers, were prepared with an easily scalable method: melt blending. The electrical properties of all prepared samples were investigated with broadband dielectric spectroscopy in the frequency range between 0.1 Hz and 1 MHz. Measurements were conducted at nine temperatures between 293.15 and 333.15 K (20 to 60 °C) with steps of 5 K. It was found that the increase in the content of bentonite in polylactide has a significant effect on the electrical properties of the prepared nanocomposites.

Fabrication of poly(maleic acid)-grafted cross-linked chitosan/montmorillonite nanospheres for ultra-high adsorption of anionic acid yellow-17 and cationic brilliant green dyes in single and binary systems

In this contribution, poly(maleic acid)-grafted cross-linked chitosan/montmorillonite composite nanospheres (PMAL-CTS/MMT) were synthesized via a facile approach for adsorption of organic dyes. The adsorption capacity of PMAL-CTS/MMT towards anionic acid yellow-17 (AY17) and cationic brilliant green (BG) was compared to PMAL-CTS, CTS/MMT, and MMT to emphasize the role of surface functional groups introduced by poly(maleic acid) and montmorillonite. Interestingly, the adsorption efficiency of PMAL-CTS/MMT nanocomposite towards both dyes in the single and binary systems was extremely high due to plenty of functional groups. The affinity of PMAL-CTS/MMT towards cationic and anionic dyes resulted from the feasible modulation of the surface charges as a function of the solution pH. The PMAL-CTS/MMT nanocomposite exhibited a maximum adsorption capacity of 518 and 1910 mg g^-1 for AY17 and BG, respectively, which is higher than most of the adsorbents reported in recent literature studies. The proposed mechanism based on the characterization of PMAL-CTS/MMT after the adsorption highlighted that the adsorption is mainly controlled by electrostatic interaction, π - π interactions, and hydrogen bonding. More importantly, the PMAL-CTS/MMT nanocomposite was successfully applied to separate the AY17 and BG dyes from real-life aquatic environments. Collectively, the simple fabrication and superior adsorption performance reveal that PMAL-CTS/MMT has the potential to treat concomitant organic dyes effectively.

Improving the Wet-Spinning and Drawing Processes of Poly(lactide)/Poly(ethylene furanoate) and Polylactide/Poly(dodecamethylene furanoate) Fiber Blends

This work aims to produce poly(lactic acid) (PLA)/poly(alkylene furanoate)s (PAF)s fiber blends for textile applications and evaluates their microstructural, chemical, thermal, and mechanical properties. The work focuses on two PAFs with very different alkyl chain lengths, i.e., poly(ethylene 2,5−furandicarboxylate) (PEF) and poly(dodecamethylene 2,5−furandicarboxylate) (PDoF), which were blended in solution at various concentrations (in the range 2.5–10 wt %) with PLA, wet spun, and subsequently drawn. Light optical micrographs highlight that PLA/PEF blends present large and concentrate PEF domains, whereas PLA/PDoF blends show small and homogeneously distributed PDoF domains. The blends appear to be immiscible, which is confirmed also by scanning electron microscopy (SEM), Fourier−Transform Infrared (FT−IR) spectroscopy, and differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) highlights that the addition of the PAFs improves the thermal stability of the fibers. The drawing process, which was carried out at 80 °C with a heat setting step at 95 °C and at three draw ratios, improves the mechanical properties of the fibers upon the addition of the PAFs. The results obtained in this study are promising and may serve as a basis for future investigations on these novel bio−based fiber blends, which can contribute to increase the environmental sustainability of industrial textiles.

Roles of Chitosan as Bio-Fillers in Radiation-Vulcanized Natural Rubber Latex and Hybrid Radiation and Peroxide-Vulcanized Natural Rubber Latex: Physical/Mechanical Properties under Thermal Aging and Biodegradability

Although natural rubber was regarded as biodegradable, the degradation is a time-consuming process that could take weeks or months for any degradation or substantial weight loss to be observable, resulting in the need for novel processes/methods to accelerate the rubber degradation. As a result, this work investigated the potential utilization of chitosan (CS) as a biodegradation enhancer for radiation-vulcanized natural rubber latex (R-VNRL) and hybrid radiation and peroxide-vulcanized natural rubber latex (RP-VNRL) composites, with varying CS contents (0, 2, 4, or 6 phr). The R-VNRL samples were prepared using 15 kGy gamma irradiation, while the RP-VNRL samples were prepared using a combination of 0.1 phr tert-butyl hydroperoxide (t-BHPO) and 10 kGy gamma irradiation. The properties investigated were biodegradability in the soil and the morphological, chemical, mechanical, and physical properties, both before and after undergoing thermal aging. The results indicated that the biodegradability of both the R-VNRL and RP-VNRL composites was enhanced with the addition of CS, as evidenced by increases in the percentage weight loss (% weight loss) after being buried in soil for 8 weeks from 6.5 ± 0.1% and 6.4 ± 0.1% in a pristine R-VNRL and RP-VNRL samples, respectively, to 10.5 ± 0.1% and 10.2 ± 0.1% in 6-pph CS/R-VNRL and 6-pph CS/RP-VNRL composites, respectively, indicating the biodegradation enhancement of approximately 60%. In addition, the results revealed that the addition of CS could increase the value of tensile modulus by 119%, while decrease the values of tensile strength and elongation at break by 50% and 43%, respectively, in the specimens containing 6-phr CS. In terms of the color appearances, the samples were lighter and yellower after the addition of CS, as evidenced by the noticeably increased L* and b* values, based on the CIE L*a*b* color space system. Furthermore, the investigation into the effects of thermal aging showed that the overall tensile properties for both curing systems were reduced, while varying degrees of color change were observed, with the pristine R-VNRL and RP-VNRL samples having more pronounced degradation/changes for both properties. In conclusion, the overall results suggested that CS had great potential to be applied as a bio-filler in R-VNRL and RP-VNRL composites to effectively promote the biodegradability, environmental friendliness, and resistance to thermal degradation of the composites.

Poly(lactic acid)-based composite film reinforced with acetylated cellulose nanocrystals and ZnO nanoparticles for active food packaging

Poly(lactic acid) (PLA)-based composite films reinforced with acetylated cellulose nanocrystals (ACNC) (1 wt%) and ZnO nanoparticles at different content (1, 3, 5 and 7 wt%) were prepared by solution-casting method. The surface acetylation of cellulose nanocrystals improved its dispersion in the PLA matrix. The morphologies, optical, mechanical, barrier, thermal and antibacterial properties of PLA/ACNC/ZnO ternary composite films were investigated. SEM images showed that ACNC and ZnO were evenly distributed in the PLA matrix to form homogenous film when the content of ZnO was ≤5 wt%. The PLA/ACNC/ZnO composite films showed improved UV blocking, mechanical strength, oxygen and water vapor barrier. This ternary composite also exhibited excellent antibacterial activity against E. coli and S. aureus. The migration amounts of Zn²⁺ from PLA/ACNC/ZnO composite film to food simulants were below the specific migration limit (5 mg/kg). Overall, the desirable properties of the resulting PLA/ACNC/ZnO ternary composite film highlighted the potential application as a promising option for active food packaging materials.

Tailoring the biodegradability of polylactic acid (PLA) based films and ramie- PLA green composites by using selective additives

This study explores the effect of plasticisers (lotader AX8900, polyethylene glycol and triethyl citrate) on biodegradability of polylactic acid (PLA) and its composites with halloysite nanotubes and ramie fabric by soil burial method. Changes in surface morphology and mechanical properties were evaluated to quantify the degradation behaviour of all samples. The results showed that the relative loss in tensile strength of ramie-PLA composites was more than that of neat PLA or plasticised PLA films. Also, ramie-PLA composite, where ramie fabric was treated with diammonium orthophosphate, had degraded entirely after 60 days of soil burial. It was also confirmed by Fourier transform infrared spectroscopy that the chemical structures of neat PLA and plasticised PLA films changed after the soil burial test. The use of these additives not only reduces the brittleness of PLA but also accelerates the biodegradation rate of PLA. Thus, PLA, along with additives, can help in reduction of carbon footprint and other environmental issues customarily associated with petro based polymers. Therefore, the finding supports the notion of PLA usage as a viable alternative to fossil fuel-based materials.

Dual-Crystallizable Silk Fibroin/Poly(L-lactic Acid) Biocomposite Films: Effect of Polymer Phases on Protein Structures in Protein-Polymer Blends

Biopolymer composites based on silk fibroin have shown widespread potential due to their brilliant applications in tissue engineering, medicine and bioelectronics. In our present work, biocomposite nanofilms with different special topologies were obtained through blending silk fibroin with crystallizable poly(L-lactic acid) (PLLA) at various mixture rates using a stirring-reflux condensation blending method. The microstructure, phase components, and miscibility of the blended films were studied through thermal analysis in combination with Fourier-transform infrared spectroscopy and Raman analysis. X-ray diffraction and scanning electron microscope were also used for advanced structural analysis. Furthermore, their conformation transition, interaction mechanism, and thermal stability were also discussed. The results showed that the hydrogen bonds and hydrophobic interactions existed between silk fibroin (SF) and PLLA polymer chains in the blended films. The secondary structures of silk fibroin and phase components of PLLA in composites vary at different ratios of silk to PLLA. The β-sheet content increased with the increase of the silk fibroin content, while the glass transition temperature was raised mainly due to the rigid amorphous phase presence in the blended system. This results in an increase in thermal stability in blended films compared to the pure silk fibroin films. This study provided detailed insights into the influence of synthetic polymer phases (crystalline, rigid amorphous, and mobile amorphous) on protein secondary structures through blending, which has direct applications on the design and fabrication of novel protein–synthetic polymer composites for the biomedical and green chemistry fields.

How Surface Properties of Silica Nanoparticles Influence Structural, Microstructural and Biological Properties of Polymer Nanocomposites

The aim of this work was to study effect of the type of silica nanoparticles on the properties of nanocomposites for application in the guided bone regeneration (GBR). Two types of nanometric silica particles with different size, morphology and specific surface area (SSA) i.e., high specific surface silica (hss-SiO₂) and low specific surface silica (lss-SiO₂), were used as nano-fillers for a resorbable polymer matrix: poly(L-lactide-co-D,L-lactide), called PLDLA. It was shown that higher surface specific area and morphology (including pore size distribution) recorded for hss-SiO₂ influences chemical activity of the nanoparticle; in addition, hydroxyl groups appeared on the surface. The nanoparticle with 10 times lower specific surface area (lss-SiO₂) characterized lower chemical action. In addition, a lack of hydroxyl groups on the surface obstructed apatite nucleation (reduced zeta potential in comparison to hss-SiO₂), where an apatite layer appeared already after 48 h of incubation in the simulated body fluid (SBF), and no significant changes in crystallinity of PLDLA/lss-SiO₂ nanocomposite material in comparison to neat PLDLA foil were observed. The presence and type of inorganic particles in the PLDLA matrix influenced various physicochemical properties such as the wettability, and the roughness parameter note for PLDLA/lss-SiO₂ increased. The results of biological investigation show that the bioactive nanocomposites with hss-SiO₂ may stimulate osteoblast and fibroblast cells’proliferation and secretion of collagen type I. Additionally, both nanocomposites with the nanometric silica inducted differentiation of mesenchymal cells into osteoblasts at a proliferation stage in in vitro conditions. A higher concentration of alkaline phosphatase (ALP) was observed on the material modified with hss-SiO₂ silica.

Accelerated Weathering Effects on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV/TiO2 Nanocomposites

The effect of accelerated weathering on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV-based nanocomposites with rutile titanium (IV) dioxide (PHBV/TiO₂) was investigated. The accelerated weathering test applied consecutive steps of UV irradiation (at 340 nm and 0.76 W m⁻² irradiance) and moisture at 50 °C following the ASTM D4329 standard for up to 2000 h of exposure time. The morphology, chemical structure, crystallization, as well as the mechanical and thermal properties were studied. Samples were characterized after 500, 1000, and 2000 h of exposure time. Different degradation mechanisms were proposed to occur during the weathering exposure and were confirmed based on the experimental data. The PHBV surface revealed cracks and increasing roughness with the increasing exposure time, whereas the PHBV/TiO₂ nanocomposites showed surface changes only after 2000 h of accelerated weathering. The degradation of neat PHBV under moisture and UV exposure occurred preferentially in the amorphous phase. In contrast, the presence of TiO₂ in the nanocomposites retarded this process, but the degradation would occur simultaneously in both the amorphous and crystalline segments of the polymer after long exposure times. The thermal stability, as well as the temperature and rate of crystallization, decreased in the absence of TiO₂. TiO₂ not only provided UV protection, but also restricted the physical mobility of the polymer chains, acting as a nucleating agent during the crystallization process. It also slowed down the decrease in mechanical properties. The mechanical properties were shown to gradually decrease for the PHBV/TiO₂ nanocomposites, whereas a sharp drop was observed for the neat PHBV after an accelerated weathering exposure. Atomic force microscopy (AFM), using the amplitude modulation–frequency modulation (AM–FM) tool, also confirmed the mechanical changes in the surface area of the PHBV and PHBV/TiO₂ samples after accelerated weathering exposure. The changes in the physical and chemical properties of PHBV/TiO₂ confirm the barrier activity of TiO₂ for weathering attack and its retardation of the degradation process.

Polylactic Acid/Polycaprolactone Blends: On the Path to Circular Economy, Substituting Single-Use Commodity Plastic Products

Circular economy comes to break the linear resource to waste economy, by introducing different strategies, two of them being: using material from renewable sources and producing biodegradable products. The present work aims at developing polylactic acid (PLA), typically made from fermented plant starch, and polycaprolactone (PCL) blends, a biodegradable polyester, to study their potential to be used as substitutes of oil-based commodity plastics. For this, PLA/PCL blends were compounded in a batch and lab scale internal mixer and processed by means of injection molding. Tensile and impact characteristics were determined and compared to different thermoplastic materials, such as polypropylene, high density polyethylene, polystyrene, and others. It has been found that the incorporation of PCL into a PLA matrix can lead to materials in the range of 18.25 to 63.13 megapascals of tensile strength, 0.56 to 3.82 gigapascals of Young’s modulus, 12.65 to 3.27 percent of strain at maximum strength, and 35 to 2 kJ/m² of notched impact strength. The evolution of the tensile strength fitted the Voigt and Reuss model, while Young’s modulus was successfully described by the rule of mixtures. Toughness of PLA was significantly improved with the incorporation of PCL, significantly increasing the energy required to fracture the specimens. Blends containing more than 20 wt% of PCL did not break when unnotched specimens were tested. Overall, it was found that the obtained PLA/PCL blends can constitute a strong and environmentally friendly alternative to oil-based commodity materials.

Studies on durability of sustainable biobased composites: a review

This review provides a comprehensive discussion on the long-term durability performance and degradation behaviour of the increasingly popular sustainable biobased composites under various aging environments.

Hyaluronic acid and chitosan-based nanosystems: a new dressing generation for wound care

INTRODUCTION

The main goal in the management of chronic wounds is the development of multifunctional dressings able to promote a rapid recovery of skin structure and function, improving patient compliance.

AREAS COVERED

This review discusses the use of nanosystems, based on hyaluronic acid and chitosan or their derivatives for the local treatment of chronic wounds. The bioactive properties of both polysaccharides will be described, as well as the results obtained in the last decade by the in vitro and in vivo evaluation of the wound healing properties of nanosystems based on such polymers.

EXPERT OPINION

In the last decades, there has been a progressive change in the local treatments of chronic wounds: traditional inert dressings have been replaced by more effective bioactive ones, based on biopolymers taking part in wound healing and able to release the loaded active agents in a controlled way. With the advance of nanotechnologies, the scenario has further changed: nanosystems, characterized by a large area-to-volume ratio, show an improved interaction with the biological substrates, amplifying the activity of the constituent biopolymers. In the coming years, a deeper insight into wound healing mechanisms and the development of new techniques for nanosystem manufacturing will results in the design of new scaffolds with improved performance.

Biodegradation Assessment of Poly (Lactic Acid) Filled with Functionalized Titania Nanoparticles (PLA/TiO2) under Compost Conditions

This paper presents a biodegradation study conducted for 90 days under standardized controlled composting conditions of poly (lactic acid) (PLA) filled with functionalized anatase-titania nanofiller (PLA/TiO₂ nanocomposites). The surface morphology, thermal properties, percentage of biodegradation, and molecular weight changes at different incubation times were evaluated via visual inspection, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) by taking degraded samples from compost at the end of target biodegradation time interval. The rapid increase of crystallinity indicated that the PLA and PLA/TiO₂ nanocomposites had heterogeneous degradation mechanisms under controlled composting conditions. The biodegradation rate of PLA/TiO₂ nanocomposites was higher than that of pure PLA because water molecules easily penetrated the nanocomposites. The dispersion of the nanoparticles in the PLA/TiO₂ nanocomposites affected the biodegradation rate of PLA. Moreover, the biodegradation of PLA could be controlled by adding an amount of dispersed TiO₂ nanofillers under controlled composting conditions.

Poly(Lactic Acid)-Based Nanobiocomposites with Modulated Degradation Rates

In the field of biodegradable polymers such as poly(Lactic Acid) (PLA), it is quite well known that their kinetics of hydrolysis strongly depend on the pH of the hydrolyzing medium. The idea explored during this study focused on PLA, is the addition of additives that are able to control the pH of water when it diffuses inside the polymer. For instance, acids (i.e. succinic acid, also used as food additive) are bio- and eco- friendly additives that are able to play this role. In order to control the release of these molecules and their dispersion inside the polymer, their intercalation in biocompatible nanofillers like layered double hydroxides (LDH) is here considered. The additives have been dispersed in the polymer by melt compounding, commonly used in the plastic industry. Several composites of PLA (4032D) and LDH intercalated with organic acids (succinic, fumaric, and ascorbic acid) have been obtained by an extrusion process. From all extruded materials, PLA films obtained by compression molding were then subjected to hydrolysis tests. The results showed that the mentioned molecules, dispersed in the polymer, are able to control the rate of hydrolysis, and experimental results show an increase of degradation time for samples containing LDH-organic acid (in particular with LDH-succinic acid), making such hybrid additives an appropriate and efficient solution for PLA.

PLA Melt Stabilization by High-Surface-Area Graphite and Carbon Black

Small amounts of carbon nanofillers, specifically high-surface-area graphite (HSAG) and more effectively carbon black (CB), are able to solve the well-known problem of degradation (molecular weight reduction) during melt processing, for the most relevant biodegradable polymer, namely poly(lactic acid), PLA. This behavior is shown by rheological measurements (melt viscosity during extrusion experiments and time sweep-complex viscosity) combined with gel permeation chromatography (GPC) experiments. PLA's molecular weight, which is heavily reduced during melt extrusion of the neat polymer, can remain essentially unaltered by simple compounding with only 0.1 wt % of CB. At temperatures close to polymer melting by compounding with graphitic fillers, the observed stabilization of PLA melt could be rationalized by scavenging traces of water, which reduces hydrolysis of polyester bonds. Thermogravimetric analyses (TGA) indicate that the same carbon fillers, on the contrary, slightly destabilize PLA toward decomposition reactions, leading to the loss of volatile byproducts, which occur at temperatures higher than 300 °C, i.e., far from melt processing conditions.

High-performance biodegradable polylactide composites fabricated using a novel plasticizer and functionalized eggshell powder

A novel polyester poly(diethylene glycol succinate) (PDEGS) was synthesized and evaluated as a plasticizer for polylactide (PLA) in this study. Meanwhile, an effective sustainable filler, functionalized eggshell powder (FES) with a surface layer of calcium phenyphosphonate was also prepared. Then, PLA biocomposites were prepared from FES and PDEGS using a facile melt blending process. The addition of 15 wt% PDEGS as plasticizer showed good miscibility with PLA macromolecules and increased the chain mobility of PLA. The crystallization kinetics of PLA composites revealed that the highly effective nucleating FES significantly improved the crystallization ability of PLA at both of non-isothermal and isothermal conditions. In addition, the effective plasticizer and well-dispersed FES increased the elongation at break from 6% of pure PLA to over 200% for all of the plasticized PLA composites. These biodegradable PLA biocomposites, coupled with excellent crystallization ability and tunable mechanical properties, demonstrate their potential as alternatives to traditional commodity plastics.

Rheological, Morphological and Mechanical Studies of Sustainably Sourced Polymer Blends Based on Poly(Lactic Acid) and Polyamide 11

The objective of this study was to gain a deep understanding of composition and compatibilization effects on the properties of entirely sustainably sourced polymer blends based on polylactide (PLA) and polyamide 11 (PA11). Generally, PLA cannot challenge regular commodity polymers due to its weak thermo-mechanical properties and its poor elongation properties. With this work, however, we present a promising route to overcome these drawbacks in order to enhance the processability of PLA: blending the polymer with various compositions of other ductile biopolymers such as PA11, as well as mixing PLA/PA11 blends with various amounts of a chain extender, Joncryl ADR^®-4368, containing reactive epoxy functions, in a laboratory-scale twin-screw extruder. The effects on the rheological, morphological and mechanical properties were investigated. Results showed that a "self compatibilization" between PLA and PA11 chains can occur but it was found to be insufficient, contrary to recent work reported in the literature. The role of Joncryl as a compatibilizer for the PLA/PA11 system has been demonstrated by the significant decrease of particle size and interfacial tension as well as the improvement of ductile properties. Moreover, a new relaxation peak appeared in the relaxation spectrum, indicating the generation of a copolymer at the polymer-polymer interface.

Chitosan-Montmorillonite Polymer Composites: Formulation and Evaluation of Sustained Release Tablets of Aceclofenac

The present study reports the preparation and evaluation of polymer composites of chitosan and montmorillonite. The prepared polymer composites were evaluated for various powder properties and characterized by FTIR-ATR (Fourier Transform Infrared Spectroscopy- Attenuated Total Reflectance), XRD (X Ray Diffraction), and SEM (Scaning Electron Microscopy) techniques. Heckel and Kawakita equations indicated good compression characteristics of the composites. The polymer composites were employed in formulating sustained release tablets of aceclofenac. The formation of intercalated lamellar structures due to the entrapment of clay particles in the polymeric matrix network was found to be responsible for the drug release retardant behavior of the composites. The in vitro drug release data were fitted to various models like zero-order, first-order, Higuchi, Korsmeyer-Peppas, and Hixon and Crowell for studying the mechanism of drug release from the formulation. The value of release exponent (n) was found to range between 0.59 and 0.82, indicating non-Fickian (anomalous) drug release behavior. Swelling-induced diffusion of the drug through the polymer matrix and polymer matrix chain relaxation appeared to play a role in the release of the drug from the polymer composites.

Partial replacement effect of montmorillonite with cellulose nanowhiskers on polylactic acid nanocomposites

In this study, hybrid montmorillonite/cellulose nanowhiskers (MMT/CNW) reinforced polylactic acid (PLA) nanocomposites were produced through solution casting. The CNW filler was first isolated from microcrystalline cellulose by chemical swelling technique. The partial replacement of MMT with CNW in order to produce PLA/MMT/CNW hybrid nanocomposites was performed at 5 parts per hundred parts of polymer (phr) fillers content, based on highest tensile strength values as reported in our previous study. MMT were partially replaced with various amounts of CNW (1, 2, 3, 4 and 5phr). The tensile, thermal, morphological and biodegradability properties of PLA hybrid nanocomposites were investigated. The highest tensile strength of hybrid nanocomposites was obtained with the combination of 4phr MMT and 1phr CNW. Interestingly, the ductility of hybrid nanocomposites increased significantly by 79% at this formulation. The Young's modulus increased linearly with increasing CNW content. Thermogravimetric analysis illustrated that the partial replacement of MMT with CNW filler enhanced the thermal stability of the PLA. This is due to the relatively good dispersion of fillers in the hybrid nanocomposites samples as revealed by transmission electron microscopy. Interestingly, partial replacements of MMT with CNW improved the biodegradability of hybrid nanocomposites compared to PLA/MMT and neat PLA.

Thermal and Flexural Properties and Water Absorption of Caulis Spatholobi Residue Fiber Reinforced Biodegradable Poly(propylene carbonate) Composites

This paper investigated and compared the thermal and flexural properties and water absorption of natural caulis spatholobi residue fibers reinforced PPC/CSRF composites. Polypropylene carbonate (PPC) was reinforced by caulis spatholobi residue fibers (CSRF) which had been pretreated by continuous steam explosion. The effect of fiber content (10 to 60 wt%) on the properties and water absorption of PPC/CSRF biodegradable composites was investigated. The thermal properties of PPC/CSRF composites indicated that the addition of CSRF could improve the thermal stability of the composites. The flexural strength and modulus of the composites were found to be improved as the content of fiber increased. From the SEM micrographs, it was found that a small amount of fibers were pulled out on fractured surfaces of the composites, showing good network structure between the fiber and PPC matrix. The water absorption amount of the composites increased with increasing the fiber content. This paper demonstrates that the incorporation of low-cost and biodegradable caulis spatholobi residue fiber into PPC provides a practical way to produce completely biodegradable and cost-competitive composites with good mechanical properties.

Mechanical and thermal property characterization of poly-l-lactide (PLLA) scaffold developed using pressure-controllable green foaming technology

Poly-l-lactide (PLLA) is one of the most promising biological materials used for tissue engineering scaffolds (TES) because of their excellent biodegradability and tenability. Here, microcellular PLLA foams were fabricated by pressure-controllable green foaming technology. Scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), wide angle X-ray diffraction measurement (WAXRD), thermogravimetric (TG) analysis, reflection-Fourier transform infrared (FTIR) analysis, enzymatic degradation study and MTT assay were used to analyze the scaffolds' morphologies, structures and crystallinities, mechanical and biodegradation properties, as well as their cytotoxicity. The results showed that PLLA foams with pore sizes from 8 to 103μm diameters were produced when the saturation pressure decreased from 7.0 to 4.0MPa. Through a combination of StepScan DSC (SSDSC) and WAXRD approaches, it was observed in PLLA foams that the crystallinity, highly-oriented metastable state and rigid amorphous phase increased with the increasing foaming pressure. It was also found that both the glass transition temperature and apparent enthalpy of PLLA significantly increased after the foaming process, which suggested that the changes of microcellular structure could provide PLLA scaffolds better thermal stability and elasticity. Moreover, MTT assessments suggested that the smaller pore size should benefit cell attachment and growth in the scaffold. The results of current work will give us better understanding of the mechanisms involved in structure and property changes of PLLA at the molecular level, which enables more possibilities for the design of PLLA scaffold to satisfy various requirements in biomedical and green chemical applications.