Polymer Biocompositions and Nanobiocomposites Based on P3HB with Polyurethane and Montmorillonite.

Due to the growing interest in biopolymers, biosynthesizable and biodegradable polymers currently occupy a special place. Unfortunately, the properties of native biopolymers make them not good enough for use as substitutes for conventional polymers. Therefore, attempts are being made to modify their properties. In this work, in order to improve the properties of the poly(3-hydroxybutyrate) (P3HB) biopolymer, linear aliphatic polyurethane (PU) based on 1,4-butanediol (BD) and hexamethylene 1,6-diisocyanate (HDI) was used. The conducted studies on the effect of the amount of PU used (5, 10, 15 and 20 m/m%) showed an improvement in the thermal properties of the prepared polymer blends. As part of the tested mechanical properties of the new polymer blends, we noted the desired increase in the tensile strength, and the impact strength showed a decrease in hardness, in particular at the presence of 5 m/m% PU. Therefore, for further improvement, hybrid nanobiocomposites with 5 m/m% PU and organically modified montmorillonite (MMT) (Cloisite 30®B) were produced. The nanoadditive was used in a typical amount of 1-3 m/m%. It was found that the obtained nanobiocomposites containing the smallest amount of nanofillers, i.e., 1 m/m% Cloisite®30B, exhibited the best mechanical and thermal properties.

Biobased poly(3-hydroxybutyrate acid) composites with addition of aliphatic polyurethane based on polypropylene glycols.

Poly(3-hydroxybutyrate) (P3HB) is the most important of the polyhydroxyalkanoates. It is biosynthesized, biodegradable, biocompatible, and shows no cytotoxicity and mutagenicity. P3HB is a natural metabolite in the human body and, therefore, it could replace the synthetic, hard-to-degrade polymers used in the production of implants. However, P3HB is a brittle material with limited thermal stability. Therefore, in order to improve its mechanical properties and processing parameters by separating its melting point and degradation temperature, P3HB-based composites can be produced using, for example, linear aliphatic polyurethanes as modifiers. The aim of the study is a modification of P3HB properties with the use of linear aliphatic polyurethanes synthesized in reaction of hexamethylene diisocyanate (HDI) and polypropylene glycols (PPG) by producing their composites. Prepared biocomposites were tested by the scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TGA). Furthermore, selected mechanical properties were evaluated. It has been confirmed that new biocomposites showed an increase in impact strength, relative strain at break, decrease of hardness and higher degradation temperature compared to the unfilled P3HB. The biocomposites also showed a decrease in the glass transition temperature and the degree of crystallinity. Biocomposites obtained with 10 wt. % polyurethane synthesized with polypropylene glycol having 1000 g ⋅ mole-1 and HDI have the best thermal and mechanical properties.

Thermally stable biopolymer composites based on poly(3-hydroxybutyrate) modified with linear aliphatic polyurethanes - preparation and properties.

PURPOSE: Poly(3-hydroxybutyrate) (P3HB) is a biopolymer, but storing products from P3HB causes the deterioration of their properties leading to their brittleness. P3HB has also low thermal stability. Its melting point almost equals its degradation temperature. To obtain biodegradable and biocompatible materials characterized by higher thermal stability and better strength parameters than the unfilled P3HB, composites with the addition of polyurethanes were produced. METHODS: The morphology, thermal, and mechanical property parameters of the biocomposites were examined using scanning electron microscopy, thermogravimetric analysis, standard differential scanning calorimetry, and typical strength machines. RESULTS: Aliphatic polyurethanes, obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycols, were used as modifiers. To check the influence of the glycol molar mass on the properties of the biocomposites, glycols with a molecular weight of 400 and 1000 g/mol were used. New biocomposites based on P3HB were produced with 5, 10, 15, and 20 wt. % content of polyurethane by direct mixing using a twin-screw extruder. The following property parameters of the prepared biocomposites were tested: degradation temperature, glass transition temperature, tensile strength, impact strength, and Brinell hardness. CONCLUSIONS: Improvement of the processing property parameters of P3HB-biocomposites with the addition of aliphatic polyurethanes was achieved by increasing the degradation temperature in relation to the degradation temperature of the unfilled P3HB by over 30 °C. The performance property parameters have also been improved by reducing the brittleness compared to the P3HB, as evidenced by the increase in impact strength and the decrease in hardness with an increase in the amount of polyurethane obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycol with a molecular weight of 400 g/mol (PU400) as modifier.

New Mono- and Diesters with Imidazoquinolinone Ring- Synthesis, Structure Characterization, and Molecular Modeling.

The objective of the studies was to synthesize and characterize new mono- and diesters with an imidazoquinolin-2-one ring with the use of 2,3-dihydro-2-thioxo-1H-imidazo[4 ,5-c]-quinolin-4(5H)-ones and ethyl bromoacetate. The products were isolated at high yield and characterized by instrumental methods (IR, 1H-, 13C-, and 15N- NMR, MS-ESI, HR-MS, EA). In order to clarify the places of substitution and the structure of the derivatives obtained, molecular modeling of substrates and products was performed. Consideration of the possible tautomeric structures of the substrates confirmed the existence only the most stable keto form. Based on the free energy of monosubstituted ester derivatives, the most stable form were derivatives substituted at sulfur atom of enolic form the used imidazoquinolones. Enolic form referred only to nitrogen atom no 1. The modeling results were consistent with the experimental data. The HOMO electron densities at selected atoms of each substrate has shown that the most reactive atom is sulfur atom. It explained the formation of monoderivatives substituted at sulfur atom. The diester derivatives of the used imidazoquinolones had second substituent at nitrogen atom no. 3. The new diesters can be used as raw material for synthesis of thermally stable polymers, and they can also have biological activity.

Analysis of the Possibility and Conditions of Application of Methylene Blue to Determine the Activity of Radicals in Model System with Preaccelerated Cross-Linking of Polyester Resins.

Unsaturated polyester resins are usually processed using a curing system consisting of initiator and accelerator introduced into the resin. Actually, the producers apply built-in amine accelerators which can be named as preaccelerators. Commonly used preaccelerators for unsaturated resins are tertiary aromatic amines of which incorporation into resin structure may bring better stability. It also causes shorter gelation time of resins because of formation of active RO• radicals that initiate polymerization. Investigated radical reactions are too fast and there is no possibility of freezing it (in unsaturated polyester) to measure with Electron Paramagnetic Resonance (EPR). The analytical methodology on radicals activity measurement in model of preaccelerated unsaturated polyester resin reaction with methylene blue as indicator was presented. Using methylene blue as indicator allows us to determine the activity of forming radicals in three-component system (cobalt salt, amine preaccelerator, peroxide, or hydroperoxide) during the reaction of radicals generating. Changes in radicals activity using methylene blue as interceptor can be observed by changes of transmittance in the UV-Vis spectrum in the range 400-950 nm.