Microindentation and differential scanning calorimetry of “liquid wood”

Abstract

Lignin was used only as a fuel until not so long ago, but the research done in the last few years has shown that it is a substance that confers wood its strength and takes the form of granules that may be melted. Thus, lignin was used to produce a material out of which almost anything can be manufactured, from furniture, accessories, toys, plastic cases for electronic devices, and food containers of any shape, to car bodies, and which is known as “liquid wood”. Its properties recommend “liquid wood” as an alternative to all plastic products in the near future, as it is biodegradable and reusable several times, and its properties remain intact. Three types of “liquid wood” are known: Arbofill, Arboblend and Arboform. Whereas Arboform is 100% biodegradable, the other two materials are only partially biodegradable. The following types of “liquid wood” were used: Arbofill Fitchie, Arboblend V2 Nature and Arboform L, V3 Nature. The research described in this paper focuses on the study of microindentation and differential calorimetry. Also, the software package we used enabled us to read both the microhardness values, and the reduced indentation modulus and Young’s modulus.The studied test samples showed the following mean recovery values: 45.9170μm for Arbofill Fitchie, 22.2783μm for Arboblend V2 Nature and 17.7430μm for Arboform L, V3 Nature. These values are in agreement with the microhardness and modulus of elasticity values. Differential calorimetry research has shown that Arboblend V2 Nature and Arboform L, V3 Nature suffered two transformations each, one endothermal and the other exothermal, during which we measured the transformation onset and completion temperatures, as well as the temperature in the middle of the transformation process. We also measured the amount of absorbed and dissipated heat, respectively. As far as Arbofill Fitchie is concerned, the DSC diagram showed no temperature-dependent heat flow variation that could suggest a solid state transformation. We could safely state that the Arbofill Fitchie sample is thermally stable up to a temperature of 423K.