Considerations on the Micro-Indentation and Differential Scanning Calorimetry of Arboform Reinforced with Aramid Fibres

Abstract

The researches made in the last years have shown that lignin is a substance that gives wood strength. It can be found in the granular form that can be melted and injected. Lignin is used to obtain material with multiple uses such as electronics, food containers etc. This material is known as "liquid wood". Fibers with high specific resistance and high elasticity modules, such as aramid fibers, are used to create high performance composites. Here are the main physical-mechanical properties of aramid fibers: high tensile strength, high shock resistance, high stresses and fatigue, excellent characteristics of damping vibrations, exposure characteristics preservation at temperatures ranging from-700C to + 1800C, flame resistance (self-extinguishing, not melting), low smoke emission, corrosion stability, good electrical characteristics, low conductivity and low dielectric constant. The main areas of use of aramid wires are: special clothes resistance to cutting and high temperature components for materials composite, ropes, cables, lashing straps, safety equipment for the armed forces, police, aircraft, etc. This research used Arboform L, V3 Nature reinforced with aramid fiber. The experimental research plan observes the Taguchi methodology with 6 input factors, each with two levels of variation. The input parameters effects are analyzed on the mechanical properties of the specimens obtained. Micro-indentation tests and differential scanning calorimetry were conducted. The studied test samples showed the following mean recovery values: 31.219μm for the first sample, 31.059μm for the second sample and 25.996μm for the third sample. Three extreme points were detected on the DSC thermogram: an endothermic peak occurs up to 380 K (I) and an exothermic one of higher intensity (II); above 430 K the DSC thermogram shows a deviation from linearity of the flow heat, which suggests a melting phenomenon. The first variation of the heat flow can be attributed to the transformations that occur in solid form in the sample subjected to heating, the first adsorption heat exchanger (peak I) and the second heat releasing (peak II). Comparing the amount of heat absorbed by heat dissipation, one may notice that the exothermic conversion is increased. The initial transformation temperature (Ts 10) corresponds to 10% of the total peak area while the final transformation temperature (Tf 90) corresponds to 90% of the total surface area.

Dynamic Mechanical Analysis and Thermal Expansion of Lignin-Based Biopolymers

“…A second, much lower peak can be observed with a centered tanδ at 0.18 and a temperature of 86.52 °C, which can be associated with a transformation that occurs in the material structure during its progressive heating, most likely to be water evaporation and/or the decomposition of natural additives or dyes [ 15 ]. On the damping curve, no transition that could be associated with the reinforcement—aramid fibers—is noticed, as it is thermally stable up to 450 °C [ 16 ], well above the range set for this analysis, and the glass transition of the aramid fibers appears in the (345–360) °C temperature range, [ 17 ]; otherwise, there are only losses of hydrogen bonds; On the damping curve, around the 145 °C temperature mark, an ascending slope appears, which indicates the beginning of the material softening—the flowing zone— which according to reference [ 18 ], has a melting point at 171 °C; The damping peak is narrow and sharp and the descending E′ slope is steep, which indicates that the chemical structure of the material is homogeneous, and the transition takes place in a short time and temperature range; The rubbery plateau region is in the 96–148 °C temperature range. …”

“…On the damping curve, around the 145 °C temperature mark, an ascending slope appears, which indicates the beginning of the material softening—the flowing zone— which according to reference [ 18 ], has a melting point at 171 °C;…”