A nanohybrid formulation of silvertitanium dioxide nanoparticles/poly(lactic acid) (Ag-TiO2/PLA) was designed for Norfloxacin/Tenoxicam (NOR/TENO) targeted delivery to maximize the bioavailability and minimize the side effects of the drugs. Ag-TiO2 nanoparticles were prepared via Stober method. NOR, TENO and a mixture of NOR/TENO (NT) were loaded onto Ag-TiO2 nanoparticles and coated by PLA via solution casting. The physical interaction between the drugs and carrier was confirmed by Fourier-transform infrared (FTIR) analysis. X-ray diffraction (XRD) demonstrated that Ag-TiO2 consists of a cubic phase of Ag with two phases of TiO2 (anatase and brookite). Ag nanoparticle fine spots coated with TiO2 were collected to form spheres averaging at 100 nm in size. In-vitro release behavior of drugs was studied at different pH (5.4, 7.4) and the release of drug from NT/Ag-TiO2/PLA was faster at pH 7.4. Gram-positive and Gram-negative bacteria were used to investigate antibacterial properties of the nanohybrid. Cytotoxicity of the nanohybrid using an MTT assay was studied against different tumor and normal cell lines. It was found that NT/Ag-TiO2/PLA has an excellent cytotoxic effect against various bacterial cells and tumor cell lines. In addition, antioxidant properties of the nanohybrids were tested using ABTS method and the nanohybrid showed moderate antioxidant activity.
Drug Delivery Systems/methods , Metal Nanoparticles/chemistry , Norfloxacin/administration & dosage , Piroxicam/analogs & derivatives , Polyesters/chemistry , Silver/chemistry , Titanium/chemistry , Anti-Bacterial Agents/administration & dosage , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacokinetics , Anti-Inflammatory Agents, Non-Steroidal/administration & dosage , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Anti-Inflammatory Agents, Non-Steroidal/pharmacokinetics , Cell Line , Cell Survival/drug effects , Drug Liberation , Hep G2 Cells , Humans , Metal Nanoparticles/ultrastructure , Microbial Sensitivity Tests/methods , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Norfloxacin/chemistry , Norfloxacin/pharmacokinetics , Piroxicam/administration & dosage , Piroxicam/chemistry , Piroxicam/pharmacokinetics , Spectrophotometry
[This corrects the article DOI: 10.1039/C9RA00034H.].
Polypropylene (PP) is an attractive polymer for use in automotive parts due to its ease of processing, hydrophobic nature, chemical resistance and low density. The global shift towards eliminating non-renewable resource consumption has promoted research of sustainable biocarbon (BioC) filler in a PP matrix, but this material often leads to reduction in composite strength and requires additional fillers. Graphene nano-platelets (GnPs) have been the subject of considerable research as a nanofiller due to their strength, while maleic anhydride grafted polypropylene (MA-g-PP) is a commonly used compatibilizer for improvement of interfacial adhesion in composites. This study compared the thermo-mechanical properties of PP/BioC/MA-g-PP/GnP composites with varying wt.% of GnP. Morphological analysis revealed uniform dispersion of BioC, while significant agglomeration of GnPs limited their even dispersion throughout the PP matrix. In the optimal blend of 3 wt.% GnP and 17 wt.% BioC biocontent, tensile strength and modulus increased by ~19% and ~22% respectively, as compared to 20 wt.% BioC biocomposites. Thermal stability and performance enhancement occurred through incorporation of the fillers. Thus, hybridization of fillers in the compatibilized matrix presents a promising route to the enhancement of material properties, while reducing petroleum-based products through use of sustainable BioC filler in composite structures.
This study investigates the effects talc and two sizes of biocarbon have as fillers in a PLA bioplastic, when considering them for durable composite applications. Analysis of the PLA-based biocomposites' resistance to wear and flammability accompanied by the vapor barrier characteristics were conducted, with subsequent rheological and thermal properties to further explain the observed results. The compression molded sheets showed a reduction in abrasion by greater than 69% for either filler type compared to the neat PLA due to their high stiffness. In contrast, only the talc provided barrier properties that hindered both water and oxygen permeability, while biocarbon did not possess a high aspect ratio to form a tortuous path necessary for barrier improvement. Yet, the biocarbon-filled PLA biocomposites provided superior flammability resistance due to its char-like caricature that superseded the neat PLA and talc variant which both failed the horizontal burning test. The rheology of the composites provided evidence in the degradation of the PLA chains from the presence of the biocarbon that did not occur with the talc, which may have also contributed to the lower barrier and higher burn resistance from increased dripping. Thus, both talc and biocarbon have their own potential applicability when it comes to acting as a barrier enhancer or flammability retardant due to their intrinsic nature, but both possess wear reinforcement for focus in the tribological area.
Fabrication of partially biobased poly(trimethylene terephthalate) (PTT) elastomeric blends was done via melt processing. Both natural rubber (NR) and epoxidized NR (ENR) were investigated as impact modifiers at 40 wt % loading to avoid lowering the overall biobased content of the blend system below that of the PTT alone (35% renewable content), along with maleated polybutadiene rubber (MR) and dicumyl peroxide (DCP) as reactive compatibilizers. The compatibility of the blend components was investigated using contact angle, rheometry, and scanning electron microscopy (SEM). The interfacial tensions and work of adhesions indicated that ENR was more miscible than NR in the PTT blend system, which was corroborated by the higher shear viscosity of the ENR blends and strong shear thinning behavior. Additionally, the predictive modeling of viscosity ratios on the elastomer-thermoplastic morphology was found to match the SEM micrographs with the dispersed elastomeric phase within the PTT matrix. The SEM images of the blends also establish that both the compatibilizers reduced the rubber inclusions size, though DCP hampered the impact performance as compared to the MR. In the presence of the MR, there was an increased cross-linking and observed variation in the Fourier transform infrared peaks demonstrating chemical interactions between the maleic anhydride groups with the PTT that allowed for the impact strength to reach 137 J·m-1 or 4.5 times that of the neat PTT, with the modulus of toughness increased by 82% and an elongation at yield of 50% because of the flexibility and amorphous nature of the rubber constituent.
To increase the biobased content of poly(ethylene terephthalate) (PET), up to 30 wt % poly(lactic acid) (PLA) was blended with PET using twin-screw compounding and injection molding processes. Multifunctional epoxide compatibilizers including a chain extender and an impact toughening agent were used as blend modifiers to improve the poor mechanical properties of PET/PLA blends. The mechanical and thermodynamic performances were investigated along with the morphological features through scanning electron microscopy, atomic force microscopy, and interfacial tension determination. From rheological and differential scanning calorimetry results, it was observed that the molecular weight of both PET and PLA increased with compatibilizers because of epoxide reactions. The toughening agent, poly(ethylene-n-butylene-acrylate-co-glycidyl methacrylate) (EBA-GMA), provided a 292% increase in impact strength over the blend but reduced modulus by 25%. In contrast, 0.7 phr addition of the chain extender, poly(styrene-acrylic-co-glycidyl methacrylate) (SA-GMA), yielded comparable performance to that of neat PET without sacrificing the tensile and flexural properties. When both compatibilizers were present in the blend, the mechanical properties remained relatively unaltered or decreased with increasing EBA-GMA content. The differences in mechanical performance observed were considered in relation to the strengthening mechanism of the two differing compatibilizers and their effects on the miscibility of the blend.
The incorporation of poly(lactic acid) (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) as a partial biobased polymer substitute for polypropylene (PP) was investigated. The ternary blends were prepared through melt compounding extrusion followed by injection molding techniques with a constant biopolymer ratio of 30 wt %. Further addition of pyrolyzed miscanthus-based carbon was carried out to establish a contrast between talc-filled PP. When the morphology of the biopolymer minor phase was analyzed theoretically using contact angle for interfacial tension and spreading coefficient values along with solubility parameter calculations and via scanning electron microscopy imaging, the core-shell architecture was found with the PHBV encasing the PLA phase. Mechanical testing of the materials showed that only the tensile properties were reduced for all samples, whereas the impact strength was increased above the neat PP. With inclusion of the biobased carbon filler into the blend system, the thermomechanical properties were elevated above that of the PP matrix. The final properties of the multiphase polymeric composites are found to be related to the morphology obtained and inherent properties of the individual constituents.
