Han-Seung Yang

Physico-mechanical Properties of Paper Sludge-Thermoplastic Polymer Composites:

This study investigates the effect of paper sludge’s mixing ratio and the types and concentrations of coupling agents on the physical and mechanical properties of paper sludge-thermoplastic polymer composites. In the experiment, four levels of mixing ratios of paper sludge to thermoplastic polymer (10: 90, 20: 80, 30: 70 and 40: 60) and three levels of coupling agent (Epolene G-3003TM) content (1, 3, and 5 wt.%) were designed to discuss the physical and mechanical properties of composite. Composite density, as expected, increased but melt flow index decreased when the paper sludge content increased. Thickness swelling and water absorption of composites was slightly improved by the addition of paper sludge compared with control specimens. Tensile properties of composites significantly increased as the mixing ratio of paper sludge increased. Especially, tensile modulus improved with the increase of paper sludge content. Flexural strength and modulus showed similar trends to that of the tensile properties. Notched and unnotched Izod impact strengths lowered by the addition of paper sludge. With the addition of coupling agent, G-3003TM, tensile and flexural properties improved considerably compared with control specimens (without any coupling agent). Epolene G-3003TM, with high molecular weight, was effective in the improvement of the composites’ tensile and flexural properties.

Thermal analysis study of viscoelastic properties and activation energy of melamine-modified urea-formaldehyde resins

The objective of this research was to investigate the activation energy and viscoelastic properties of urea-formaldehyde (UF) resin, melamine-formaldehyde (MF) resin and UF-MF resin mixtures by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The purpose of adding MF resin to the UF resin was to reduce the formaldehyde emission. As the MF resin content was increased in the UF-MF resin mixture, the formaldehyde emission decreased. The storage modulus (E′), loss modulus (E″) and loss factor (tan δ) of each resin were measured by DMTA. With increasing temperature, as the resin cured, the storage modulus (E′) increased in all resin systems. The storage modulus (E′) increased both as a function of increasing temperature and with increasing MF content. The activation energies (E a) of the curing reactions of the UF and MF resins alone, as well as the mixed resins, on different substrates, were calculated on the basis of the variation of the temperature of the maximum of each DSC scan exotherm using the Kissinger equation. The E a value of the UF resin decreased as the MF resin content ratio increased, and because of this lower activation energy the UF-MF resins cured faster than the UF resin. Formaldehyde is incorporated more easily and completely into melamine than into urea. The results showed that MF resin reacts with formaldehyde faster than UF resin because of its high −NH content.

Flexural Fatigue and Reliability Analysis of Wood Flour/High-Density Polyethylene Composites

In this study, the flexural fatigue behavior of wood flour/high-density polyethylene composites is characterized. A non-dimensional analysis is adopted to establish a prediction equation for the fatigue life of the composites, and S—N curves and survivability diagrams are then constructed to show the fatigue life prediction of the wood/plastic composites (WPCs). Small coupon samples of the composites are tested in flexural fatigue. The predicted results in the non-dimensional (non-linear) fatigue model are better related to the testing data than the classical S—N curve (linear experimental data) fitting, and they could be used as the predicting model for fatigue life analysis of the WPCs. The best-fit S—N curve and its corresponding bounds based on 95% confidence are provided for the composites, and the fatigue data are well distributed within 95% confidence range. Fatigue life distribution diagrams are produced for the WPCs using a two-parameter Weibull cumulative density function based on the probability of survival concept, and this concept is then used to predict the fatigue life of the composites under an applied load. From these diagrams, the fatigue life can be easily determined at any given reliability index. The S—N plots under different reliability index present considerable value to the designer if the structure contains a critical component where any failure is catastrophic. The proposed experimental fatigue study and related analyses verify the applicability of non-dimensional fatigue model and theory of two-parameter Weibull distribution to fatigue life prediction and reliability analysis of WPCs, and they can be used to predict fatigue behavior of similar materials.