MTA-BME Research Group

Novel thermoplastic dynamic vulcanizates (TDV) with enhanced wear resistance based on in situ produced polyurethane matrix

Project ID:
Supported by:
Nemzeti Kutatási, Fejlesztési és Innovációs Hivatal (NKFIH)
1 December 2018 - 30 November 2022
Supervisor (BME):
Dr. Tamás Bárány
Participant researchers (BME):
Dr. Halász István Zoltán
Kohári Andrea

Project summary

To find a potential solution for the recycling of used rubber products is a key issue of environmental protection. One of the viable opportunities is the replacement of several traditional crosslinked rubbers with alternative materials that have matching overall performance and properties, but can be recycled more simply and economically. One of the emerging family of materials showing rubber-like behavior is the group of so-called thermoplastic dynamic vulcanizates (TDVs). These TDVs, composed of a continuous thermoplastic phase in which rubber is finely dispersed, combine the beneficial properties of its components, namely the elastic behavior of rubbers and the simple, processing (and also possible reprocessing) of plastics. Accordingly, manufacturing TDVs with properties similar to those of traditional rubbers could be a straightforward solution to the above-mentioned problem. However, the overall performance of TDVs can be limited by the inadequate adhesion between the rubber and the thermoplastic phase. Our intention is to enhance this bonding with a new reactive production technique, involving the in situ synthesis of the thermoplastic phase (PU), which should improve interfacial adhesion, partly due to the mutual entanglement of the molecules of each phase. This should yield a strong interphase between the rubber and the thermoplastic phase and thus lead to an improvement in the overall performance of the in situ produced blend. A further aim of this project is to investigate the effects of recycling this novel TDV and determine the effects of repeated processing on its properties.

Project results

Section 1
1 December 2018 - 30 November 2019
We reviewed the literature in the field and collected the relevant initial knowledge for the research. Based on the literature, the raw materials for the synthesis of thermoplastic polyurethane (TPU) were selected and obtained. Within the project a Bruker Tensor II type FTIR spectrometer was purchased, so that the investigation of the material structure properties relevant for the research could be carried out in-house. The synthesis was carried out in an internal mixer, using production parameters and formulations based on literature data, and the effect on the properties of the TPUs was investigated. In our work, we investigated the applicability of two polyols, polytetrahydrofuran and hydroxyl-terminated polybutadiene, and in the case of polytetrahydrofuran, the effect of the ratio of polyol to chain extender on the properties of the final polyurethane. By increasing the ratio of polyol, the prepared thermoplastic polyurethane can be softened and its hardness can be reduced. The investigation of the applicability of hydroxyl-terminated polybutadiene was important because the TPUs so produced may be able to form better bonds with polybutadiene or polybutadiene copolymer-based rubbers in the manufacture of thermoplastic dynamic vulcanizates (TDVs). Among manufacturing parameters, the effects of mixing time and different rotor speeds were also explored. The development of the other component of TDVs, the rubber phase, was initiated in the pursuit of formulation simplicity, with only vulcanizing agents being added to the NBR, XNBR and ENR rubbers chosen as models. The starting rubbers are polar in nature, similar to the thermoplastic polyurethane phase, which is the basis for the cooperation of the two phases. These rubber compounds were also qualified and used to produce TDVs using the experience gained from polyurethane synthesis.
Bruker Tensor II type Fourier transform infrared spectrometer and spectras of the samples

Section 2
1 December 2019 - 30 November 2020
The work started by investigating the reproducibility of thermoplastic polyurethane synthesis. By comparing the torque and temperature curves recorded by the internal mixer of TPUs prepared at different times under the same conditions and formulation, we found that they are different. This is important because the change in torque is a good indicator of the change in molecular weight if all other parameters are unchanged. When examining the mechanical properties of the samples, we also found significant differences. Due to their hydrophilic nature, the materials used for synthesis are susceptible to water absorption, and the water they contain can react with the diisocyanate, leading to adverse side reactions. The chain extender used is able to bind the moisture content of the air entering the glass, which cannot be completely expelled by vacuum drying or other simpler drying methods. To overcome this problem, 1,4-butanediol was poured into smaller glass bottles under inert atmosphere and zeolite was added to it to absorb possible tiny amounts of water. These glass bottles are stored in a desiccator containing phosphorus pentoxide. To produce thermoplastic polyurethanes, we have also experimented with the two-step or also known as prepolymer method in addition to the one-step method used previously. One of the advantages of this process is that it is less harmful to health and is therefore becoming more widespread in industry. Another is that it allows polyurethane with a much more regular structure to be produced. We used four prepolymers with different isocyanate contents. %). In addition to the 1,4-butanediol chain extender, we tried 1,6-hexanediol as well. We performed different tests on the TPU samples produced. As the isocyanate content of the prepolymer increased, the samples became stiffer and their tensile strength increased, while their elongation at break decreased. Furthermore, by using 1,6-hexanediol, we obtained better results for the same prepolymer.
Preparation of thermoplastic polyurethane-based thermoplastic elastomers by the prepolymer method

Section 3
1 December 2020 - 30 November 2021

Section 4
1 December 2021 - 30 November 2022

Project-related publications

  1. Kohári A., Halász I. Z., Bárány T.: In situ előállított, poliuretán alapú termoplasztikus elasztomerek fejlesztése. Polimerek, 5, 622-625 (2019)
  2. Kohári A., Halász I. Z., Bárány T.: Thermoplastic dynamic vulcanizates with in situ synthesized segmented polyurethane matrix. Polymers, 11, 1663/1-1663/1-15 (2019) 10.3390/polym11101663 IF=3.426 Q1

© 2014 BME Department of Polymer Engineering - Created by: Dr. Romhány Gábor