Mechanical and physical properties of thermally modified wood flour reinforced polypropylene composites

H. Kallakas¹*, M. Martin¹, D. Goljandin², T. Poltimäe¹, A. Krumme³ and J. Kers¹

¹Tallinn University of Technology, Faculty of Chemical and Materials Technology, Department of Polymer Materials, Chair of Woodworking, Teaduspargi 5, EE 12618 Tallinn, Estonia
²Tallinn University of Technology, Faculty of Mechanical Engineering, Department of Materials Engineering, Chair of Materials Science, Ehitajate tee 5, EE19086 Tallinn, Estonia
³Tallinn University of Technology, Faculty of Chemical and Materials Technology, Department of Polymer Materials, Ehitajate tee 5, EE 19086 Tallinn, Estonia
*Correspondence: heikko.kallakas@ttu.ee

Abstract:

Heat treatment of wood helps to lower the hydrophilicity and polarity of wood fibres used in wood-plastic composites. By means of heat treatment it is possible to reduce the access to wood hydroxyl (OH) group, which causes hydrophilic and polarity of wood fibres. Therefore improving compatibility between the wood and polymer matrix. In this research, the effect of wood flour (WF) heat treatment and chemical modification with 3-aminopropyltriethoxysilane (APTES) were investigated. WPC test samples were prepared using alder (Alnus incana) WF with mesh size of 0.05 mm as a filler material and polypropylene (PP) as the matrix material. WF was chemically modified with NaOH and APTES to increase the adhesion and compatibility of WF to polymer matrix. The composites were manufactured using a twin-screw extruder and the test samples were made by injection molding. The composites mechanical properties were tested using three-point flexural test and Charpy impact test. The composite physical properties were investigated with Fourier transform infrared spectroscopy (FTIR). The effect of silane (APTES) and NaOH modification on thermally treated and untreated WF was examined with contact angle measurement. Comparisons were made between the untreated WF and thermally treated WF. Also the effect of NaOH and silane (APTES) modification on the properties of thermally modified and unmodified WF composite were investigated. Using WF as a filler material increased flexural strength, while impact strength decreased thus making the material more rigid and brittle. The test results revealed that there was no significant difference in the mechanical properties between thermally treated and untreated composites. However, chemical modification improved the mechanical properties of the composites.

Key words:

chemical modification, thermal treatment, wood flour, wood-plastic composite

The effect of pre-planting treatment of seed tubers on potato yield formation

V. Eremeev, J. Jõudu, A. Lõhmus, P. Lääniste and A. Makke

Department of Field Crop Husbandry, Estonian Agricultural University, Kreutzwaldi 64, 51014 Tartu, Estonia; e-mail: slava@eau.ee

Abstract:

In the trials conducted in 2000–2002, we examined possibilities for growing potato using different methods of pre-planting treatment of seed tubers.
The varieties exploited were ‘Varajane kollane’ (early), ‘Piret’ (medium early) and ‘Ants’ (medium late). There were used the following ways of treatment for all varieties: PS – pre-sprouting, TT – thermal treatment and 0 – tubers not treated.
The dynamics of tuber yield formation during the vegetation period was significantly influenced by the weather. In terms of potato growth, weather conditions were the most favourable in 2001. The weather in 2000 and 2002 was not the most suitable for potato growth and development, and the yield in these years proved lower than the three-year average.
The average results from the three years show that potatoes could not realise their full potential to reach maximum yield. Pre-planting germination and thermal treatment had positive effects during the entire vegetation period, the effect being stronger at the beginning and then gradually decreasing.
Pre-planting treatment of seed tubers had a different effect on varieties with different growing times.
A comparison between the varieties showed that ‘Piret’ and ‘Varajane kollane’ started to form tubers early and thus exceeded the development of the variety ‘Ants’ until the 60^th day of growth. ‘Ants’ reached its maximum yield, 47.0 t ha^-1, already by the 114^th day, followed by the fast-ripening ‘Varajane kollane’ and the medium-ripening ‘Piret’. Thermal treatment did not give any advantage in terms of total yield formation compared to untreated seeds, except for the pre-planting germination variant of the variety ‘Varajane kollane’, the total yield of which exceeded that of its untreated variant by 7.08 t ha^-1.

Key words: