Joong Yeon Lim

Effects of repetitive processing, wood content, and coupling agent on the mechanical, thermal, and water absorption properties of wood/polypropylene green composites

In an effort to determine to what extent natural fiber/plastic composites were recyclable, this study conducted repetitive processing cycles on wood flour/polypropylene composites through extrusion up to three times followed by injection molding. Mechanical properties of the composites, containing 10–50 wt% wood flour and with/without addition of 3 wt% maleic anhydride polypropylene (MAPP) as coupling agent, were evaluated by conducting tensile test, thermal analysis, and water absorption test. Repetitive processing as well as wood content and coupling agent addition influenced physical properties of the composites. MAPP functioned well in improving fiber-matrix adhesion in terms of mechanical properties. Repetitive processing did not deteriorate the composite’s properties; rather opposite effect was shown. Thermal analysis indicated that the alteration in properties was contributed by the molecular condition of the polypropylene matrix. Water absorption increased with the wood flour content but reduced when MAPP was added and with more processing cycles.

Finite element analysis of bone–implant biomechanics: refinement through featuring various osseointegration conditions

A refinement technique is proposed for developing finite element models capable of simulating peri-implant bone conditions for bone types II, III, and IV at various degrees of osseointegration. The refined models feature a transition region between bone (cortical and cancellous) and implant and designate it partially to fully osseointegrated by assigning corresponding fractions of the bulk bones elastic properties to this region. Bone is assumed to be transversely isotropic. The refined technique is implemented in a case study, in which osseointegrated (25-100%) peri-implant bone, type II, III, or IV with an implant attached, is loaded with a 100 MPa occlusal load. The biomechanics of this peri-implant bone was simulated and analysed. Results showed that the less dense bone must support higher stress and strain, especially at the cortical region. Higher degree of osseointegration induced higher stress but lower strain. Both the bone type and the osseointegration condition significantly affected the stress-strain relation. For minimum stress and strain, denser and more osseointegrated peri-implant bone is desirable. When bone failure criteria were set, based on the yield strength and strain of the bone, a higher degree of osseointegration was needed for the less dense peri-implant bone to be considered safe.

Effect of Silane Treatment on Mechanical Properties of Basalt Fiber/Polylactic Acid Ecofriendly Composites

Ecofriendly thermoplastic composites combining basalt fiber and polylactic acid were prepared and analyzed, considering effects when the fiber is silane treated. Intended to improve mechanical properties of the composites, the silane treatment varied the types of silane solution (water- and methanol-based solvents) and immersion time (15 and 60 min). Optimum mechanical properties were exhibited by composite whose basalt fiber constituent was treated by silane dissolved in water-based solvent, for a short period of time.

Elastic properties of polycaprolactone at small strains are significantly affected by strain rate and temperature

Tensile tests were conducted on polycaprolactone at various strain rates and temperatures. Focusing on the mechanical properties within only the small-strain elastic region, i.e. up to the inflection point in the stress–strain diagram, it was found that strain rate and temperature had significant effects on the polymer. This finding implies that the effects of strain rate and temperature on the elastic properties of polycaprolactone should be considered in the design and manufacture of rigidity-sensitive, load-bearing applications, including use as biomaterial for scaffolds in tissue engineering applications.

Polycaprolactone–starch blends with corn-based coupling agent: physical properties and in vitro analysis

In an attempt to improve properties of polycaprolcatone–starch blend, this study uses zein as coupling agent in preparing the blend through a single-step process. Zein, which has affinity to both polar and non-polar groups, is expected to improve miscibility between the blends’ constituents and its overall biocompatibility. Mechanical properties of the blend were tested and further characterizations (Fourier transform infrared spectroscopy, thermal properties) were performed to analyze the effect of zein as an addition to the blend’s physical properties. The blend’s biocompatibility was examined by indirect methods (contact angle and weight gain after immersion in simulated body fluid) and in vitro analysis. No significant effect on the blend’s strength and stiffness was caused by adding zein. Hydrophilicity and cell affinity were improved when zein was added. Zein did not perform as a coupling agent that improved miscibility between polycaprolactone and starch, but its addition improved the blend’s biocompatibility.

Towards improving mechanical properties of basalt fiber/polylactic acid composites by fiber surface treatments

Attempting to improve reinforcement effect on basalt fiber/polylactic acid composites, this study evaluates the effects of silane treatment, atmospheric glow discharge plasma polymerization, desizing, and addition of maleic anhydride coupling agent. The treated fibers were characterized, in terms of surface morphology and existing molecular bonds, and the mechanical properties of the composites were tested (i.e. strength, stiffness, and elongation at yield). Among the fiber surface treatments and the addition of coupling agent, improved mechanical properties were only shown by the silane treated and the atmospheric plasma polymerized composites by having 26 and 22% higher strength, respectively, as compared with the untreated one.

Interfacial Optimization of Lyocell Fabric/PLA with Silane Treatments

In order to improve the interfacial bonding with polylactic acid, Lyocell fabric’s surfaces were treated with various silanes. The silanes applied were aminoethylaminopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane, respectively. Silane was chosen since hydroxyl group (-OH) in silane always reacts with -OH in Lyocell fabric. As received fabric’s sizing was with a solution containing polyvinyl alcohol (PVA), poly acrylic acid (PAA) and water at the ratio of 3 : 1 : 96. Highest peel test results was obtained with 3wt% silane concentration (3-methacryloxypropyltrimethoxysilane). Highest tensile strength was obtained with 2wt% silane concentration (3-methacryloxypropyltrimethoxysilane). Tensile tests were carried out before analyzing the fracture surface of the composites by scanning electron microscope. FT-IR run confirmed the silane on the surface of fabric.

Strain rate and temperature effects on elastic properties of polycaprolactone/starch composite

Abstract Composite of polycaprolactone (PCL) and starch is a potential biomaterial for tissue engineering scaffolds. During implantation, its mechanical properties might be compromised considering the various strain rates it is subjected to and that human body temperature is close to polycaprolactone’s melting temperature. This study aims at revealing the effect of strain rate and temperature to the elastic properties of polycaprolactone-starch composite. Tensile test at strain rates of 5, 0.1, and 0.01 mm/min at ambient and body temperatures were performed. It was revealed that strain rate as well as temperature readily have significant effects on the composite’s elastic properties. Such effects have similar trends with that of PCL homopolymer which is used as the composite’s matrix. Further analysis on the consequence of the finding was performed by applying the behavior to a finite element model of a porous scaffold and it was found that the discrepancy in elastic properties throughout the construct is even greater.

Effect of starter defect to GIIC of unidirectional CFRP composite

Critical strain energy release rate in CFRP composites characterizes the delamination resistance. More study is still needed to measure the critical strain energy release rate in sliding shear mode (GIIC) considering various factors that influence its measurement. This study evaluates one of the influencing factors, the starter defect. Two types of on thin, unidirectional CFRP composites with one having thin film insert as starter defect and another one with pre-crack under Mode II loading were prepared and tested in three point bending end notch flexure (3ENF) test. It was found that the (GIIC) of the former was more than twice higher than that of the latter, supposedly due to the presence of resin rich region in the former.