Preparation and Properties of Thermoplastic Polyurethane Composites Filled with Powdered Buckwheat Husks

Modified Buckwheat Husk as a Filler for Urea-Formaldehyde Resin in Plywood Production

The aim of the presented research was to determine the suitability of both non-modified and modified buckwheat husk (BH) as a filler for urea-formaldehyde adhesive in plywood production. The effect of two modification methods, acetylation and silanization, was investigated. Infrared spectroscopy outcomes confirmed that both acetylation and silanization of the filler had occurred. Based on the results, it was found that the introduction of BH had a significant effect on both the adhesive properties and the characteristics of the manufactured plywood. The application of non-modified husks led to a reduction in viscosity and an extension of the gelation time, and the produced plywood boards were characterized by reduced bonding quality and increased delamination. Modification of the husk surface by acetylation and silanization with 3-aminopropyltriethoxysilane contributed to the noticeable improvement in the resin properties. On the other hand, the improvement in plywood properties, consisting of the increase in bonding quality and reduced delamination, was observed only in the case of the silanized husk. Furthermore, the use of non-modified and acetylated husk did not significantly influence the formaldehyde emission. The reduction in the investigated emission of formaldehyde was observed only in the case of variants containing 15 and 20% of silanized buckwheat husk.

Functional Management of Waste Wood Flour as an Example of a 'Greener' Approach towards the Synthesis of Bio-Based Epoxy Resins

Nowadays, in the era of growing ecological awareness, composites based on synthetic or bio-based polymers and fillers of natural origin find various potential applications. Plant-based materials are obtained using plant-derived materials, such as e.g., vegetable oil or wood fillers. Such synthesis of polymer composites allows for the selection of the reactants in terms of the potential requirements of the application. In the presented research polymer composites were obtained using bio-based high molecular-weight epoxy resins of hydroxylated soybean oil (SMEG) and a low-molecular-weight epoxy resin (EPR 0162) filled with the oak wood flour waste from the production of parquet flooring. To increase the poor compatibility between the highly hydrophilic wood fibers and the hydrophobic polymer matrix, waste wood flour (WF) was subjected to chemical modifications (mercerization, acetylation, and diisocyanate modification). Based on performed FT-IR and SEM analysis of wood flour, it was found that, among all performed modifications, the acetylation allows for the hydroxyl groups removal to the greatest extent. As a result of sequence synthesis including (1) the synthesis of SMEG_EPR polyaddition product, (2) the introduction of WF followed by its (3) curing with diisocyanate, obtained wood/polymer composites contain about 40% of raw materials of natural origin. As a consequence of the carried out modification of the wood waste flour, the compatibility of the filler and the bio-based polymer matrix was improved, resulting in an improvement in compressive strength by 3.51 MPa (SMEG_EPR_2% WF-10% NaOH) and 2.19 MPa (SMEG_EPR_2% A-WF) compared to samples containing unmodified wood flour. Additionally, concerning the results registered for pure SMEG_EPR composition, the introduction of 2 wt.% of wood filler resulted in a three/fourfold increase in the elongation at the break of the composition containing unmodified and chemically modified wood flour (10.99%-SMEG_EPR_2%WF; SMEG_EPR_2%WF-5%NaOH-10.36%; SMEG_EPR_2%WF-10%NaOH-9.54%, and 12.15%-SMEG_EPR_2%A-WF). Moreover, the incorporation of wood filler increased the value of the compression set of samples (2.40%-SMEG_EPR_2%WF, 2.39%-SMEG_EPR_2%WF-5%NaOH, and 2.34% for SMEG_EPR_2%WF-10%NaOH compared with 2.32%-SMEG_EPR).

Buckwheat Hulls/Perlite as an Environmentally Friendly Flame-Retardant System for Rigid Polyurethane Foams

This article presents an innovative approach to the flame retardancy of rigid polyurethane foams using natural waste in the form of buckwheat hulls in combination with an inorganic additive-perlite. A series of tests were presented in which various contents of flame-retardant additives were used. Based on the test results, it was found that the addition of the buckwheat hull/perlite system affected the physical and mechanical properties of the obtained foams, i.e., apparent density, impact strength, and compressive and flexural strength. The structure of the system had also changed, directly affecting the hydrophobic properties of the foams. In addition, it was observed that the addition of buckwheat hull/perlite modifiers improved the burning behavior of composite foams.

Failure Analysis of Abnormal Cracking of the Track Circuit Reader Antenna Baffle for High-Speed Trains

The track circuit reader (TCR) is an important part of train control systems. This paper reports a failure of the TCR antenna baffle, which is used to prevent the TCR antenna from being struck by foreign objects. The designed service life of the baffle is 4.8 million kilometers, but serious cracking was found during routine maintenance after only 0.67 million kilometers of operation. In order to avoid the hidden danger brought by the incident to the safe operation of the train, it is necessary to conduct a complete failure analysis of the failed TCR antenna baffle. Therefore, a comprehensive investigation of the base material, cleaning agents, crack morphologies, etc., was carried out, and the failure environment of the antenna baffle was verified by experiment. The final results show that the environmental stress cracking is the root cause of the failed antenna baffle, and the multiple bubbles produced by the formed process of the antenna baffle are another important cause. According to the conclusions, the solutions to prevent the reoccurrence of such failures are proposed. After these solutions are adopted, the number of failed antenna baffles is greatly reduced, which fully proves the correctness of this analysis.

Properties of Rigid Polyurethane Foam Filled with Sawdust from Primary Wood Processing

In this study, the possibility of using sawdust, a by-product of primary wood processing, as a filler (WF) for rigid polyurethane (PUR) foams was investigated. The effects of the addition of 5, 10, 15 and 20% of WF particles to the polyurethane matrix on the foaming process, cell structure and selected physical-mechanical properties such as density, thermal conductivity, dimensional stability, water absorption, brittleness, compressive and bending strengths were evaluated. Based on the results, it was found that the addition of WF in the amount of up to 10% does not significantly affect the kinetics of the foam foaming process, allowing the reduction of their thermal conductivity, significantly reducing brittleness and maintaining high dimensional stability. On the other hand, such an amount of WF causes a slight decrease in the compressive strength of the foam, a decrease in its bending strength and an increase in water absorption. However, it is important that in spite of the observed decrease in the values of these parameters, the obtained results are satisfactory and consistent with the parameters of insulation materials based on rigid PUR foam, currently available on the market.