This work is mainly focused on study of thermal and thermomechanical properties of obtained bio-based polyurethane (coded as bio-PU) composites via using different types of bio-components (bio-glycol, modified soybean oil and sisal fiber) in the procedure. The chemical structure, morphology and mechanical properties were also investigated and described in this manuscript in order to know more perfect characterization of produced composites. The bio-based polyurethane matrix of composites was synthesized via prepolymer method. Bio-PU composites were produced by dispersing 5 and 15 mass% of sisal fibers into the polyurethane matrix during their synthesis. To investigate the thermal stability of sisal fibers and bio-PU composites, the thermogravimetric method (TG) was used. Thermomechanical tests were performed by means of dynamic mechanical analysis (DMA). Based on the results of thermomechanical analysis, it was found that the sisal fibers amount has the impact on storage and loss modulus. Chemical structure was confirmed by FTIR spectra. Mechanical results and scanning microscopy images of the composites showed good interfacial adhesion between sisal fibers and the bio-based PU matrix.

In our study, we focused on obtaining bio-polyurethane composites using bio-components such as bio glycol, modified natural oil-based polyol, and microcrystalline cellulose (MCC). The pre-polymer method was used to prepare the bio polyurethane matrix. Prepolymer was synthesized using 4,4′-diphenylmethane diisocyanate and a polyol mixture containing 50 wt% of commercial polyether and 50 wt% of hydroxylated soybean oil (H3). Bio based 1,3-propanediol (1,3bioPDO) was used as the prepolymer chain extender. The composites were produced by dispersing 5, 10, 15 and 20 wt% of MCC in the bio polyurethane matrix. The polymerization was catalyzed with 1,4-diazabicyclo[2.2.2]octane. The influence of the added MCC powder on the structure and thermal properties of the obtained composites was investigated. The FTIR analysis demonstrated that the MCC admixture affected the absorbance of C–O–C and C=O groups and the phase separation index of the obtained bio-polyurethanes composites. The results of mechanical tests and scanning microscopy images indicated good interfacial adhesion between the partially bio-based matrix of the composite and bio-filler. The results of thermomechanical analysis showed that the application of MCC as a filler has a positive effect on the storage and loss modulus of the composites.

Natural oils have been used in the production of plastics for a long time. However, the number of studies dedicated to polyurethane research has shown an increase only recently. Usually, petrochemical components are used in polyurethane synthesis. Nowadays, there have been attempts made to replace polyols in polyurethanes with the modified oils and other natural raw materials. It is a promising and important scenario because the flexible segment of such polyurethanes can contain even up to 60 wt % of the novel ingredient. In the case of material evaluation for industry, one can additionally count on lowering the product price because natural oil is generally 2 to 3 times cheaper as compared to its synthetic equivalent. Oils most commonly used in industrial applications are soybean oil, palm oil, rapeseed oil, castor oil and tung oil. In this work the study results and the possibilities of applying natural oils in polyurethane synthesis are presented.