In this investigation, the effect of different surface treatments on morphology, water absorption and biodegradable properties of sisal fiber reinforced PLA (SF/PLA) composites were studied. ...Field-emission scanning electron microscopy (FE-SEM) analysis confirmed the good dispersion of different surface treated sisal fibers in the PLA composites which improved the interfacial adhesion between sisal fibers and PLA matrix. Water absorption is reduced significantly for combined treated SF/PLA composites by 136% as compare to untreated composites. Environmental degradation was studied for SF/PLA composites by composting the samples into the soil. FE-SEM analysis shows the fiber reinforced composites were degraded faster than the pure PLA. It is also worth noted that the combination of alkali and HIU treated fiber composites show slower degradation as compare to untreated one. A significant weight loss could be seen (17.87% weight loss for untreated SF/PLA composites) after soil composting for 120 days. This investigation clearly confirms that the surface treatments of sisal fibers with the combination of alkali and high intensity ultrasound (HIU) are effective to improve filler dispersion, water resistance and biodegradability of SF/PLA composites
In this study, we present the manufacturing process of two new composites materials in the form of long fibers of polylactic-acid (PLA) or polypropylene (PP), reinforced by cellulose whiskers ...micro-fibers loads. In order to evaluate the mechanical properties of these advanced materials, a several uniaxial tensile tests were carried out. The PP and the PLA have initially been spinning without the addition of cellulose whiskers micro-fibers. In order to study the effects of cellulose whiskers micro-fibers reinforcements in the Mechanical behavior of the PLA and PP filaments, we determinate the proprieties of these advanced material from the tensile results. For the PP composite filaments material case, the whiskers reinforcement increases Young's modulus and failure resistance, but it reduces the limit strength failure. For the PLA composites the addition of 1% wt of cellulose whiskers from the total volume fraction of the material, increase the Young’s modulus more than 50% and a decrease of the failure resistance and the limit strength of composite. The obtained composites fibers are very rigid and brittle. What follows, that the addition of cellulose whiskers micro fibers in PP matrix, provides mechanical properties more convenient compared to the PLA matrix.
The aim of this paper is to investigate the influence of the surface modification ratio on the tensile strength of the hybrid-interface-controlled HAp/PLA composite materials. Here, pectin and ...chitosan were selected as the surface modification polymers for the HAp particles. In addition, o-nitrobenzyl alcohol was selected as the photodissociable protecting groups to avoid the chemical reaction between the surface modification polymers. First, the critical amount of the surface modification polymers for the whole surface modification of the HAp particles was evaluated. Then, the tensile tests were carried out for the hybrid-interface-controlled HAp/PLA composites with the various surface modification ratio. As a result, the FT-IR measurement revealed that the positively and negatively charged region of the HAp surface can be fully modified by pectin of 11 wt% and chitosan of 0.6 wt%, respectively. Based on this result, the surface modification ratio of the hybrid-interface-controlled HAp particles could be evaluated under the assumption that the 50 % of the HAp surface is positively charged whereas the another 50 % is negatively charged. As a result of the tensile tests of the HAp/PLA composites, the tensile strength drastically decreased by the hydrolysis in the case that the surface modification ratio was 0 %. On the other hand, the decrease in the tensile strength was quite small in the case that the surface modification ratio was 75 %. It is notable that the hydrolytic degradation in the tensile strength was suppressed in the early stage and then accelerated after the 2-week hydrolysis, in the case that the surface modification ratio was 50 %. This result suggests that the simultaneous optimization of the hydrolytic and fracture properties of the hybrid-interface-controlled HAp/PLA composites would be enabled by the control of the surface modification ratio.
We studied the antibacterial effect and mechanical properties of PLA composites with in organic porous zeolite-type bacteriocides. The specimens were prepared by an intermeshing co-rotating twin ...screw extruder using different contents of inorganic bacteriocide. The degree of dispersion of the in organic bacteriocide in the PLA composite was confirmed by FE-SEM. The contents of Ag and Zn in the composite were also investigated by energy dispersive spectroscopy at different concentrations of the inorganic bacteriocide. The antibacterial effects were analyzed by turbidity analysis, shaking culture, and drop-test. The mechanical properties, such as the tensile and flexural properties, impact strength, and physical properties, were also investigated. As the content of inorganic bacteriocide increased, the antibacterial activity was increased, especially against Staphylococcus aureus. Mechanical properties, namely, tensile strength, elongation, flexural strength, and impact strength, tended to decrease with an increase in inorganic bacteriocide content, but the tensile and flexural modulus increased.
In this study, amorphous nickel phosphate (NiPO) was prepared through urea-assisted hydrothermal process. The composition of NiPO was investigated via X-ray photoelectron spectrum (XPS). And the ...structure of NiPO was characterized by Fourier transform infrared spectrometer (FTIR) and X-ray diffraction measurement (XRD).Then poly(lactide) (PLA) was melt blended with the resulting NiPO to prepare flame retardant PLA composites. The flame retardant property of PLA composites was probed using limiting oxygen index test (LOI), UL-94 vertical burning test (UL-94), cone calorimeter test (CCT). And the thermal combustion property was analyzed through pyrolysis combustion flow calorimeter test (PCFC). In the meantime, the thermal stability of NiPO microparticles and PLA composites was analyzed through thermogravimetric analyzer (TGA) and integrated procedural degradation temperature (IPDT). In the meantime, the melting and crystallization property of PLA composites was investigated through DSC analysis. Results showed that NiHPO
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was the main component of NiPO. PLA composite with only 2 wt.% NiPO powder exhibited excellent flame retardancy (LOI = 27.5% and UL-94 V-0 rating). In the CCT and PCFC test, it showed that HRR of PLA composites was higher in the early stage of combustion and lower in the late stage of combustion than that of pure PLA. Moreover, a slightly increased CO production rate (COP) and obviously decreased total smoke production (TSP) were found in PLA composites containing 2 wt.% NiPO in CCT. In the DTG curve, the similar weight derivation trend to HRR in CCT and PCFC test was also observed. Additionally, the intrinsic thermal stability was enhanced significantly by 19°C with 2 wt.% NiPO into PLA composites. DSC results showed that NiPO could also improve the crystallization property of PLA composites.
