The role of solvent type,size and chemical composition of bioactive glass particles in modulating material properties of poly(ε-caprolactone) based composites

The role of solvent type (dichloromethane, 1,4-dioxane, tetrahydrofuran), size (<45, <3 μm) and chemical composition (silica-rich, calcium-rich) of bioactive glass (BG) particles in modulating surface properties, crystallinity, mechanical properties and in vitro bioactivity of poly(ε-caprolactone) based composite films was investigated. Films were prepared by solvent casting method. Bioactive glasses from the SiO₂–CaO–P₂O₅ system were obtained by sol-gel method. The particle size and solvent type played an important role in nucleation and crystallisation kinetics of PCL, affecting morphology, topography and wettability of films. In contrast to BG particles of <45 μm size, the smaller ones (<3 μm) were exposed on the surfaces of films and consequently have improved hydrophilicity and have provided crystallisation of carbonated hydroxyapatite after incubation in SBF. Type of the solvent, by affecting surface properties, influenced hydroxyapatite crystallisation process. The addition of BG particles of both sizes resulted in enhanced modulus and drastic decrease in elongation at break.     

Innovative flax tapes reinforced Acrodur biocomposites: A new alternative for automotive applications

Flax Acrodur biocomposites are elaborated with an innovative flax reinforcement consisting of long technical fibers unidirectionally arranged without any weft and twist. The fibers cohesion is performed by using a new process consisting by reactivating the pectin cement. A polyester thermoset matrix (Acrodur) is used to impregnate the flax reinforcement and to produce unidirectional (UD) laminates. The relationship between the main process variables (drying, fibers content, densification and curing parameters) and the properties of the biocomposites is investigated. The optimized biocomposites have an elastic modulus of 18 ± 1 GPa with 55% wt.% flax fiber content and a low density of 0.93 g/cm³. The thermal stability of the developed biocomposites is also investigated by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA). DMA results show a slight change of the storage modulus in a range of temperature from 23 °C to 160 °C. The appropriate processing parameters for the biocomposites are established. The developed flax tapes reinforced Acrodur biocomposites have a potential to be integrated for automotive applications thanks to their high stiffness/weight ratio and environmental advantages.     

Glycidyl methacrylate-compatibilized poly(lactic acid)/hemp hurd biocomposites: Processing,crystallization, and thermo-mechanical response

Poly(lactic acid)-based biocomposites were developed with hemp hurd (Cannabis sativa L.) with grafting-based interfacial compatibilization. Poly(lactic acid) was extruded with hemp hurd and glycidyl methacrylate as the polymer/hurd interfacial compatibilizer, and injection molded. Interfacial compatibility between poly(lactic acid) and hemp hurd increased with grafted glycidyl methacrylate in comparison to the non-compatibilized control, as corroborated by scanning electron microscopy fractography and mechanical analysis, which showed increases in the glycidyl methacrylate-grafted 20% (w/w) hemp hurd/poly(lactic acid) biocomposite, retaining 94% of the neat polymer strength, with increases in crystallinity, and showing a range of thermo-mechanical properties desirable for rigid biocomposite applications.     

电化学方法制备HAp/金属生物复合材料研究进展

着重介绍了4种制备HAp(羟基磷灰石)／金属生物复合材料的电化学方法，即电结晶、电泳沉积、电镀共沉积和阳极氧化；详细叙述了4种方法相关的研究进展，并对利用电化学方法在金属或合金上制备HAp生物涂层的发展趋势作了概述。     

In situ Biomimetic Synthesis to Produce Hydroxyapatite–Polyvinyl Alcohol Biocomposites: Precipitation and Spray Drying Methods

In this study, the hydroxyapatite–polyvinyl alcohol biocomposites were prepared using in situ biomimetic synthesis with two different drying routes: drying in oven and spray drying. Besides, the effect of the molecular weight of polyvinyl alcohol on structure of the biocomposites was investigated. Fourier transform infrared analysis indicated the presence of the polyvinyl alcohol in the composite structure. X-ray diffraction patterns showed that the change of the molecular weight of polymers or using different methods did not have a noticeable effect on the peak positions. Scanning electron microscope and particle size analyses showed that increasing in the polymer molecular weight decreased the particle size.     

Enhancement of mechanical properties of waste-sourced biocomposites through peroxide induced crosslinking

The enhancement of mechanical performance of waste-sourced biocomposites through peroxide induced crosslinking was investigated in order to expand their range of applications. Biocomposites containing 25 to 35 wt% of residual Kraft-pulp cellulose fibers, 1.5 wt% of a selected maleic-anhydride-modified polyethylene coupling agent and a 60/40 (w/w) of recycled agricultural plastic/post-consumer plastic blend were compounded in an extrusion-compounding pilot-plant. Changes in the blend structure due to the presence of the organic peroxide used were studied by spectroscopy and thermal analysis. It was found that the addition of extremely low amounts of peroxide (0.025–0.050 wt%) results in remarkable improvements in stiffness, strength and toughness of biocomposites, without compromising processability. Thus, their tensile strength and energy at break increased up to 89.4% and 138%, respectively, with regard to uncrosslinked biocomposites. Scanning electron microscopy revealed an improvement of the fiber–matrix adhesion due to the treatment with the peroxide.     

Improved fatigue performance for wood-based structural panels using slot and tab construction

This paper presents static and fatigue bending behavior for a wood-based structural panel having a slot and tab (S/T) construction technique. Comparisons were made with similarly fabricated panels without the S/T construction technique. Experimental results showed that both types of panels had similar bending properties in the static tests. However, the panels with S/T construction had better fatigue results. The failure modes were different for the two fabrication techniques. The panels without S/T debonded at the core:face interface. Whereas, the panels with S/T had cracks that propagated within the rib of the core after debonding damage at the core:face interface. The fatigue deflection-life relationship indicated that the S/T construction improved the connection between the faces and core. The S/T construction decreased the deflection growth rate that delayed panel failure. The fatigue stress-life relationship or degradation was better for the panels with S/T construction than the panels without the S/T construction.     

Development of PLA/cellulosic fiber composite foams using injection molding: Crystallization and foaming behaviors

Poly(lactic acid) (PLA) and northern bleached softwood kraft (NBSK) or black spruce medium density fiberboard (MDF) fibers were melt compounded using a co-rotating twin screw extruder and subsequently microcellular injection molded. Poly(ethlylene glycol) (PEG) was used as a lubricant. The microcellular structure, thermal properties, and crystallization behaviors were characterized using scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and wide angle X-ray diffraction. Results show that cellulosic fibers, acting as crystal nucleating agents, increased the crystallization temperature and the crystallinity and decreased the crystallization half time. The dissolved N₂, the shear stress, and biaxial stretching during foaming also enhanced the crystallinity of PLA. Compared to PLA/PEG, a finer and more uniform cell structure was achieved in the cellulosic fiber composite foams. The improved foam morphology was attributed to the cell nucleating effects of the fibers and the increased melt strength by the addition of cellulosic fibers and by the gas- and fiber- induced crystallization.     

Thermo-mechanical characterization of Manicaria Saccifera natural fabric reinforced poly-lactic acid composite lamina

The development and thermo-mechanical characterization of a novel green composite lamina, made of PolyLactic Acid (PLA) reinforced with a natural fabric extracted from Manicaria Saccifera palm, are presented. The composite was characterized by thermal-analysis (TGA), tensile, flexural, and izod impact tests, and scanning electronic microscopy (SEM). TGA analysis showed that the degradation process of the composite started earlier than that of neat PLA due to the lower thermal stability of the fabric. The mechanical tests showed that PLA properties were improved. The tensile strength, elastic modulus and impact resistance were improved by 26%, 51% and 56% respectively. Good dispersion and mechanical interlocking of PLA into the fabric were seen by SEM explaining the improvements of the mechanical properties of the composite. In summary, the good tensile properties and the excellent energy absorption capabilities of the MF/PLA composite lamina show great potential of Manicaria fabric as reinforcement in green composites.