Fused filament fabrication of biodegradable polylactic acid reinforced by nanoclay as a potential biomedical material

Fused filament fabrication (FFF) is one of the most common 3D printing techniques having considerable potential in various fields such as pharmaceutical, medical, aerospace, and automotive. One of the impediments of FFF components is their lower mechanical performance compared with those from conventional fabrication methods. This work aims to investigate the effect of adding nanoclay due to being nontoxic to the biodegradable polylactic acid (PLA) polymer matrix for medical applications. PLA granules were melt-compounded by a twin-screw extruder with nanoclay at 2 and 4 wt.%, and then, PLA and PLA/nanoclay filaments were produced using a single-screw extruder. An L9 orthogonal array of the Taguchi approach was utilized as the design of the experiment tool to study the process in detail considering nanoclay content, nozzle temperature and raster angle as material and processing parameters. The dispersion of nanoclay in the PLA matrix was assessed by X-ray diffraction test. The results indicated that the tensile strength was enhanced by 4.6% and 15.3% using the addition of 2 and 4 wt.% of nanoclay, respectively. The microscopic observations showed that the bonding between the rasters and between the contours and rasters was improved by increasing the temperature, and consequently, led to higher tensile strength values. The results revealed that the tensile strength of 38.9 MPa was obtained at the optimum condition.

Effect of Nanoclay Addition on the Morphology, Fiber Size Distribution and Pore Size of Electrospun Polyvinylpyrrolidone (PVP) Composite Fibers for Air Filter Applications

The fabrication of Polyvinylpyrrolidone (PVP) electrospun layers for air filter applications is the target of this study. Solutions of 10% PVP containing 0, 3, 10 and 25 wt% nanoclay were used to fabricate electrospun fibers. Scanning electron microscopy showed that the fibers’ roughness increased by increasing the nanoclay content, and it was maximum at the nanoclay concentration of 25 wt%. Concurrently, nanoclay decreased the pore size considerably and increased the range of the fibers’ size distribution up to 100%. In addition, as the nanoclay concentration increased, the frequency distribution decreased abruptly for the larger fiber sizes and increased dramatically for the small fiber sizes. This phenomenon was correlated to the effect of nanoclay concentration on the conductivity of the solution. The solution’s conductivity increased from 1.7 ± 0.05 µS/cm for the PVP solution without nanoclay to 62.7 ± 0.19 µS/cm for the solution containing 25 wt% nanoclay and destabilized the electrospun jet, increasing the range of fiber size distribution. Therefore, the PVP solution containing 25 wt% nanoclay has potential characteristics suitable for air-filter applications, owing to its rougher fibers and combination of fine and thicker fibers.

Consolidation Behavior and Compression Prediction Model of Coastal Cement Soil Modified by Nanoclay

Coastal cement soil modified by nanoclay (NCS) has particular research significance as a modification approach to improve the high compressibility of coastal cement soil (CCS). At curing ages of 7 days and 28 days, consolidation and SEM tests were performed on 6 groups of NCS samples with a nanoclay content between 0% and 10% and 6 groups of CCS samples with a cement content between 10 and 20%, and a compression prediction model was established based on the test results. Test results show that (1) there is a linear interval for the improvement effect of the increment of cement content on the compression of CCS samples. In this test, the cement content in this interval is between 12% and 18%. CCS with a cement content of 18% is preferred. (2) The improvement effect on the compression of the sample is better with a nanoclay content of 4% and 8%, but poor with a content of 2%. At a consolidation pressure between 100 kPa and 800 kPa, NCS with a nanoclay content of 4% is preferred. (3) Adhesion is better with a nanoclay content of 4%, and the filling effect is better with a content of 8%. (4) The cosine-power function-exponential model is established, and the measured data are fitted, and a prediction model for the compression amount of CCS and NCS is established.

Rheological and tribological approaches as a tool for the development of sustainable lubricating greases based on nano-montmorillonite and castor oil

This study investigates the development of novel montmorillonite/castor oil blends to formulate sustainable lubricating greases to promote the replacement of petrochemicals industry-derived materials by substances obtained from renewable sources. Specifically, the effect of the thickener concentration on the rheological, chemical, thermal, tribological properties, and atomic force microscopy (AFM) microstructure of these systems were studied. The results showed that the C20A nanoclay content could be used to modulate the viscosity values, the linear viscoelastic functions, and tribological properties of these montmorillonite dispersions. In general, these gel-like dispersions exhibited remarkable lubricant properties; the samples showed values of the friction coefficient and wear scars similar or lower than those obtained with model bentonite grease.

Synergistic Effect of Cellulose Nanofiber and Nanoclay as Distributed Phase in a Polypropylene Based Nanocomposite System

Since the plastic-based multilayer films applied to food packaging are not recyclable, it is necessary to develop easily recyclable single materials. Herein, polypropylene (PP)-based cellulose nanofiber (CNF)/nanoclay nanocomposites were prepared by melt-mixing using a fixed CNF content of 1 wt %, while the nanoclay content varied from 1 to 5 wt %. The optimum nanoclay content in the PP matrix was found to be 3 wt % (PCN3), while they exhibited synergistic effects as a nucleating agent. PCN3 exhibited the best mechanical properties, and the tensile and flexural moduli were improved by 51% and 26%, respectively, compared to PP. In addition, the oxygen permeability was reduced by 28%, while maintaining the excellent water vapor permeability of PP. The improvement in the mechanical and barrier properties of PP through the production of PP/CNF/nanoclay hybrid nanocomposites suggested their possible application in the field of food packaging.

Nanocomposite hydrogel of chitosan-g-poly acrylamide/ nanoclay: effect of degree of cross-linking on their swelling

In this study a chitosan-g-Polyacrylamide hydrogel was prepared through graft copolymerization in the presence of an appropriate amount of potassium persulfate as the initiator and different ratio of methylene bis acrylamide as the crosslinker agent. After dewatering the gels in acetone and being dried in oven, the swelling behaviors of hydrogels in different media such as distilled water, NaCl 0.15M, basic buffer with pH=10 and acidic buffer with pH=3 were evaluated. The gel with the highest swelling degree (i.e. 1/60 crosslinker) was selected to be used in the synthesis of nanocomposite hydrogel. Nanocomposite hydrogels with 1, 3, 5 percent of nanoclay were synthesized respectively. Swelling behaviors of nanocomposite hydrogels were examined. The results of swelling test showed a decrease in the swelling extent as the crosslinker ratio is increased. The result showed that different swelling behaviors as the media of experiment is changed. They showed a lower swelling extent in saline media than in distilled water. The results of swelling test in buffer media show lower swelling extent than in distilled water and swelling extent in acidic buffer with pH=3 is greater than swelling extent in basic buffer with pH=10. The swelling extent of nanocomposite increases slightly with the increase of nanoclay content up to 1%. More increase in the nanoclay content caused a drastic decrease in the swelling extent as well.

Influence of nanoclays on water uptake and flexural strength of glass–polyester composites

Fiber-reinforced polyester composites have received significant attention in a variety of applications due to their considerable potential due to such characteristics as high strength, stiffness, and modulus. However, one of the most important concerns about polymeric composites is their sensitivity to moisture attack. This work has been conducted to investigate the effects of nanoclay addition on reinforcing glass/polyester composites against water absorption and the resultant deterioration of flexural strength. Therefore, chopped strand mat and woven fiberglass polyester specimens were fabricated by using the hand lay-up technique with varying weight percentages of Cloisite 20A nanoclays (0, 1.5, and 3 wt%) and immersion in water for a time duration of 21 days. The specimens were weighed for the water absorption test. The results showed a remarkable drop in water absorption of the composite samples with the increase of nanoclay content. Moreover, although all the pure and nanocomposite specimens underwent degradation in flexural strength due to the water absorption, the strength was found to significantly increase with increasing the percentage of nanoclay at all immersion periods. The experimental results were confirmed by scanning electron microscopy (SEM). SEM images indicated that the presence of nanoclay protected the fiber/matrix interfaces.

Preparation of cross-linked PVC-g-(St-MA) copolymer/organoclay nanocomposites and investigation of chemical characteristics, morphology, thermal, and mechanical properties

The goal of this work is to investigate the effect of incorporating organoclays on the cross-link structure, morphology, and thermomechanical properties of cross-linked organoclay/polyvinyl chloride grafted with styrene and maleic anhydride (PVC- g-(St-MA)) copolymer nanocomposites (CPN). Cloisite30B (C30B) and Cloisite15A (C15A) organoclays were used for the preparation of cross-linked PVC- g-(St-MA) nanocomposites by the solution mixing route. The nanoclay content in nanocomposites varied from 0.2 wt% to 1 wt%. The chemical structure and interaction between PVC- g-(St-MA) cross-linked segments and nanoclays were studied by Fourier transform infrared (FTIR) peaks deconvolution method. FTIR spectroscopy suggested the lowest extent of hydrogen bonding interaction for C30B containing sample, which decreased with clay content increment. The morphology of nanocomposites was studied by X-ray diffraction and transmission electron microscopy methods. Morphological observation revealed a near to the exfoliation state for organoclays in PVC- g-(St-MA) nanocomposite containing 1 wt% C30B. However, C15A/PVC- g-(St-MA) nanocomposite (C15A-CPN) exhibited partially intercalated and agglomerated morphology. Differential scanning calorimetry examination was conducted to measure the glass transition temperature ( T g) of the segments. At the same clay content, the T g of the C30B containing nanocomposites were higher than that of C15A samples. The mechanical properties of these nanocomposites were also investigated. As a consequence, C30B-CPN showed improved mechanical properties compared to C15A-CPN and cross-linked PVC- g-(St-MA) samples.