Koku mizas ūdens ekstrakcijas produktu komplekss pielietojums trīsdimensiju poliuretāna matricas veidošanai ar paaugstinātu termo-oksidācijas stabilitāti un pieejamību mikrobiālai noārdīšanai
Projekta apraksts
Projekta kopsavilkums: Poliuretāni (PU) ir visuniversālākie polimēri ar nepārtraukti augošu tirgu. Atjaunojamās sastāvdaļas īpatsvara palielināšana, PU materiālu ekspluatācijas īpašību un bioloģiskās noārdīšanās uzlabošana ir PU ķīmijas mūsdienu attīstības noteicošais virziens. Projekta mērķis ir iegūt zināšanas par koku mizas sastāvdaļu komplekso izmantošanu PU materiālos. Sastāvdaļas, kas spēj izšķīst un reaģēt PU matricas veidošanās apstākļos, tiks izolētas no mizas, izmantojot ūdens ekstrakciju ar mikroviļņu (MW) palīdzību. MW apstrāde ar kontrolējamu šūnu sienu noārdīšanās veicināšanu un hemicelulozes atvasinājumu pāreju šķīdinātājā, regulēs ekstraktu sastāvu un funkcionalitāti. Ekstraktvielas tiks ievadītas PU matricā, OH grupu, galvenokārt ogļhidrātu izcelsmes, un izocianāta reakcijas rezultātā. Glikozīdu tipa fenolisko mizas antioksidantu iekļaušana PU matricā, kavēs to iztvaikošanu augstās temperatūrās. Mizas atlikumi pēc ekstrakcijas, kas tiks ievadītas PU putu sastāvā kā pildviela, darbosies kā antipirēni. Tiks novērtēta mizas ekstrakcijas produktu ietekme uz PU plēvju un cieto putu mehāniskajām īpašībām, termo-oksidācijas stabilitāti un bioloģisko noārdīšanos. Projekta galvenie rezultāti būs mizas ekstrakcijas režīmi un metodes tās frakciju ievadīšanai biobāzētu PU materiālu, ar uzlabotām īpašībām, receptēs. Tas veicinās tirgus produktu attīstību uz mežsaimniecības atkritumu bāzes.
Projekta galvenie rezultāti: Izveidota teorētiskā bāze un tehnoloģiska pieeja mizas komponentu kompleksai izmantošanai biobāzētu poliuretānu, ar uzlabotām īpašībām, iegūšanai. Ir nopublicēti 5 zinātniskie raksti, ir reģistrēts patents.
Projekta īstenošanas termiņš: 36 mēneši.
Projekta kopējais finansējums: 299999.70 EUR apmērā.
Projekta īstenošanas vieta: Latvijas Valsts koksnes ķīmijas institūts (LVKĶI), Rīga, Latvija
Uzsaukums, aktivitāte: Latvijas Zinātnes Padomes Fundamentālo un lietišķo pētījumu projektu 2021. gada konkurss (LZP FLPP 2021/1)
Projekta īstenošana (informācija sagatavota angliski)
Sixth 6-month activity (01.07.2024 - 31.12. 2024).
During this period, the compression properties and thermal stability of bio-polyol-based rigid PUR foams were evaluated in comparison to PUR foams produced using commercial polyol-polyethers, specifically Lupranol 3300 and Lupranol 3422. PUR foams derived from oxypropylated extractives exhibited superior compression characteristics, achieving a strength of 0.31 MPa and a Young’s modulus of 8.6 MPa at an apparent density of 40 kg/m³. Although the composition based on liquefied extractives showed lower performance, it still demonstrated improved properties relative to the reference foams.
Bio-polyol-based PUR foams also exhibited enhanced thermal characteristics, as determined through non-isothermal thermogravimetric analysis. The incorporation of polyols derived from BA bark extractives into the PUR foam composition reduced material weight loss during the volatile formation stage (200–350 °C) and increased weight retention at higher temperatures (450–600 °C), predominantly associated with char combustion. It is well-established that the flammability of PUR materials is linked to the release of flammable gaseous decomposition products during the initial degradation stage. Consequently, the bio-polyol-based PUR foams are expected to exhibit lower flammability compared to the reference materials.
Combustion tests performed using the cone calorimeter method (ISO 5660-1:2015) supported these findings. The results aligned with the thermogravimetric analysis data, showing a lower total heat release during the initial stages of combustion and a reduced tendency for fire development compared to the reference materials.
Despite previous findings suggesting that incorporating bark-based polyols into the composition of polyurethane (PU) films enhances their biodegradability, the results of biodegradation tests on the synthesized PUR foams indicate a different behavior. The PUR foams, containing black alder bark extractives-based polyols and extracted bark residues as fillers, exhibited resistance to biodegradation even with a substantial renewable content of up to 24%. This was demonstrated by a maximum mass loss of only about 7% for the bark-based PUR foams after a 2-month biodegradation test in composting conditions, compared to about 4% mass loss for a reference PUR composition based on the commercial polyether polyols. These findings suggest that bark-based PUR foams are well-suited for applications such as insulation in environmentally exposed settings. By incorporating black alder bark extractives-based polyols and extracted bark residues, the renewable content of the materials increased significantly to 22–24%, aligning with sustainability goals without compromising the durability and performance of these materials in long-lasting applications.
In this period the following publications were published or submitted:
- Arshanitsa, A., M.Pals., Godina, D., Bikovens, O. The oxyalkylation of hydrophilic black alder bark extractives with propylene carbonate with a focus of green polyols synthesis. JRM, 2024, vol.12, no.11., 1927-1948, DOI: 10.32604/jrm.2024.05646 (Published).
- Arshanitsa, A., Pals, M., Vevere, L., Jashina, L., Bikovens, O. The complex valorization of black alder bark biomass in compositions of rigid polyurethane foams. Materials (submitted 26.11.2024)
- Aršaņica, A., Pals, M., Vēvere, L. Augu izejvielu apstrādes metode poliuretānu ražošanai. (Method of processing plant raw materials for the production of polyurethanes). Iesniegums Patenta Piešķiršanai. (Patent Application) EPLV202100000062683; (submitted 02.12.2024.
Fifth 6-month activity (01.01.2024 - 30.06.2024).
In this period, two approaches for introducing black alder bark extracts into polyols suitable for PUR foam synthesis were developed. Approximately 300 g of extractives (on a dry matter basis) containing about 32% oregonin with a total OH content of 14.9 mmol·g⁻¹ were obtained using optimal conditions of microwave extractions with water performed at 90 °C.
In the first approach, the obtained extractives were liquefied using the glycerol-based commercial polyol polyethers Lupranol 3300. Biomass content in the Lupranol 3300-extractives suspension was 10%, 20%, 30%, and 40%, respectively. Liquefaction was performed at temperatures of 125, 150, and 170 °C, respectively. The duration varied in the range of 1-24 hours. The insoluble fraction of the extractives was removed from the polyols obtained by hot filtration. It was shown that a temperature of 150 °C and a duration of about 6 hours are the optimal conditions for extractives liquefaction. Liquid polyols containing the soluble portion of biomass in the range of 8 to 34%, with a viscosity of 900-27000 mPa·s⁻¹ and an OHV of 400-650 mgKOH·g⁻¹, were obtained.
The second approach was based on an innovative “green” modification of extractives with propylene carbonate (PC) in the presence of 1,8-Diazabicyclo [5.4.0] undec-7-ene as a catalyst. The reactivity of phenolic and aliphatic OH groups with PC was studied separately using catechol, xylose, and PEG 400 as model compounds. FTIR spectroscopy and GPC were used to monitor PC conversion and to characterize the structure of the obtained polyol. Under optimal conditions, including a temperature of 150 °C, a PC/OH ratio of 3, and a duration of 24 hours, uniform liquid polyols with a biomass content of ~27%, low viscosity of 900 mPa·s⁻¹, and an OHV of 500 mgKOH·g⁻¹ were synthesized.
During this period, the methodology for obtaining PUR foam with extracts as a polyol component was developed. A commercial product-based PUR foam recipe containing 70 pbw of Lupranol 3300, 30 pbw of Lupranol 3422, 20 pbw of blowing agent “Option”, 0.5 pbw of catalyst Polycat 5, and PMDI (NCO/OH=1.15) was used as a reference composition. The biomass-containing polyols obtained by different pathways substituted the commercial polyol Lupranol 3300 in the recipe. The PUR foams were obtained by the free-rising method using a mold of 1500 cm³. PUR foams with a density in the range of 40-50 kg·m⁻³ were obtained. Currently, properties such as compression strength and modulus, closed-cell content, and thermal stability of reference and bio-polyols containing PUR foams are under testing and will be compared.
During the reporting period, the bark residue, which will be introduced into PUR foam as a filler, was characterized by thermogravimetric analysis. The yield of char residue in Ar media was ~32%. The mechanical activation of the bark residue was performed using a planetary mill. A powder with 68.8% of particles with a size of 50 µm or less was obtained.
In this period the results were presented in two conferences:
- International Conference for Young Scientists on Biorefinery Technologies and Products 2024 (BTechPro 2024!) April 24-26, 2024, Riga, Latvia
The oxyalkylation of hydrophilic tree bark extractives with propylene carbonate with a focus on green polyols obtaining.
M. Pals, J. Ponomarenko, M. Lauberts, A. Arshanitsa - 30TH ANNUAL INTERNATIONAL SCIENTIFIC CONFERENCE "RESEARCH FOR RURAL DEVELOPMENT 2024" (RRD2024) May 15-16, 2024, Jelgava, Latvia
DISSOLUTION BEHAVIOUR OF BLACK ALDER BARK EXTRCTIVES IN POLYURETHANE SYNTHESIS MEDIA: A COMPREHENSIVE STUDY
M. Lauberts, M. Pals, J. Ponomarenko, A. Arshanitsa.
Fourth 6-month activity (01.07.2023 - 31.12.2023)
According to the working plan, the mid-term report was prepared. The report received a high rating from the reviewer.
During this period, the effects of the sugar moiety and the diarylheptanoid moiety, characterized by a linear flexible C7 aliphatic chain, on the physical-mechanical properties and biodegradation behavior of PU materials were evaluated. For this, the carbohydrates were removed from extracts by hydrolysis with sulfuric acid. As a result, the parent extract contained 71.4% oregonin, which, during hydrolysis, is converted into an oregonin sugar-moiety-free hydrolysis product and hirsutenone. The sugar-free fraction was introduced into the PU films up to 30% content as a renewable polyol, using the methodology previously developed for non-hydrolyzed extractives.
The obtained TG curves clearly demonstrate the positive effect of the concentration of diarylheptanoid moieties in biopolyols, obtained after the hydrolysis of the parent black alder bark extract, on the thermo-oxidative stability of the synthesized PU materials at 5% of bio-polyol. The introduction of hydrolyzed diarylheptanoid-based extracts as polyols in the matrix of PU films increases their mechanical strength and modulus compared to reference biomass-free PU films. However, this effect was less pronounced compared to non-hydrolyzed extractives. The synthesized PU films containing 30% of various diarylheptanoid-based biopolyols, replacing PEG 400, were subjected to a degradation period of 2 months in compost-enriched soil, serving as both the medium and the source of biodegrading microorganisms.
The susceptibility to biodegradation of the PUs under study was evaluated by their weight loss, as well as using FTIR and Py-GC/MS/FID techniques. After the 2-month biodegradation period in soil, the PU synthesized using conventional fossil-based building blocks experienced a weight loss of 5.8%, compared to 11.8% and 11.2% for non-hydrolyzed and hydrolyzed extractives containing PU, respectively. It was established that the sugar present in extractives does not influence the susceptibility of the PUs to biodegradation. The presence of the catechol moiety in the structure of diarylheptanoids is the dominant factor for the biodegradation of PU materials based on these polyols. It was concluded that complete removal of sugar from the BA bark extractives is not advisable for their usage as bio-polyol in the composition of PU elastomers.
Third 6-month activity (01.01.2023 - 30.06.2023)
After characterization of the bark extracts and their fractions composition, functionality, reactivity in the urethane-formation reactions and development of the methodology for their introduction in PU materials, their influence on the structural, mechanical and thermal properties of the model PU films was thoroughly studied. PU elastomers containing up to 50% of bark extractives were obtained.
Experimental data confirmed the crosslinking activity of the bark-sourced biopolyol in PU, leading to an increase in glass transition temperature (Tg), a decrease in sol fraction yield upon leaching of cured PU networks in THF, a significant increase in Young's modulus and tensile strength of material. The bark-sourced building blocks promoted char formation under high temperature and oxidative stress, reducing combustible volatiles and limiting heat release during macromolecular network degradation compared to biopolyol free PU. This shift towards char oxidation at higher temperatures suggests a potential decrease in flammability during actual combustion tests of bio-polyol-based PUs.
According to the project plan, substantial experimental work has been started to study the availability of synthesized materials to microbial-mediated degradation. The susceptibility to biodegradation of bio-based PU elastomers containing 40% and 50% of black alder bark extractives as biopolyol, replacing fossil-based PEG 400, was compared to that of 100% fossil-based PU. The synthesized PUs films were subjected to a degradation period of 2 months in sewage water and compost-enriched soil, serving as media and sources of biodegrading microorganisms. The weight loss data, as well as the Py-GC/MS, FTIR and TG confirmed the increased susceptibility to biodegradation of PU containing bark-sourced building blocks in comparison with fossil based PU. The abstract titled "Influence of Black Alder Bark Extractives as Integral Building Blocks on the Susceptibility to Biodegradation of Resilient Polyether Polyurethanes" was submitted for presenting the results at the International Conference EcoBalt 2023 "Chemicals & Environment" in Tallinn, Estonia, from 09 to 11 October 2023.
The project's findings have been submitted for publication in two high-impact scientific journals with a citation index of at least 75% of the average in the field:
"Controlling the Reactivity of Hydrophilic Bark Extractives as Biopolyol in Urethane-Formation Reactions Using Various Catalysts" by Alexandr Arshanitsa, Jevgenija Ponomarenko, Matiss Pals, and Lilija Jashina, submitted to the journal "Industrial Crops and Products."
"Impact of Bark-Sourced Building Blocks as Substitutes for Fossil-Derived Polyols on the Structural, Thermal, and Mechanical Properties of Polyurethane Networks" by Alexandr Arshanitsa, Jevgenija Ponomarenko, Matiss Pals, Lilija Jashina, and Maris Lauberts, submitted for publication in the journal "Polymers."
Second 6-month activity (01.07.2022 - 31.12.2022)
Unlike fossil-derived polyol-polyether, which are enriched with aliphatic OH, bark-derived polyols contain both aliphatic OH and phenolic groups. As reactivity of various phenolic groups, including phenolic groups of catechol, pyrogallol and resorcinol moieties in urethane-formation reaction is not characterized so far, it was studied during this project using both obtained bark extracts and several modelling compounds chosen based on the extract’s composition. Kinetic reactions between the polyols under study, including model compounds, and diphenyl methane diisocyanate in a DMSO solution were monitored using FTIR by measuring the absorption intensity at 2273 cm-1, corresponding to the free -NCO groups of the isocyanate. Additionally, isothermal DSC was employed to determine the second-order rate constants and molar enthalpy of the reactions. According to the obtained results, the involvement of aliphatic OH and phenolic groups of the bark extractives in the reaction with isocyanate can be modified by using different catalysts. The high catalytic activity and selectivity of the tertiary amine - 1,4-diazabicyclo [2.2.2] octane (DABCO) catalyst towards reactions of extractives phenolic groups with PMDI was established. But tin organic - dibutyl tin dilaurate (DBTDL) catalyst exhibit higher activity in the reaction of aliphatic OH groups of carbohydrates with isocyanate compared to compared to amine catalyst.
First 6-month activity (01.01.2022 - 30.06.2022)
The microwave assisted water extraction of coniferous and deciduous tree barks was performed at different regimes. The composition and functionality of coniferous and deciduous tree bark extractives were studied, depending on microwave-assisted water extraction conditions. Was shown that black alder bark extractives (Alnus glutinosa) obtained at low (70-90°C) temperature consists mainly on non-lignin polyphenolic diarylheptanoids from which oregonin is enriched with aliphatic and phenolic OH groups. Water extracts of Baltic pine (Pinus sylvestris) bark obtained at the same temperature mainly consist of condensed tannins or proanthocyanidins. Extracts from both black alder and pine barks obtained at different times of isothermal heating between 130-150°C have decreased content of phenolic secondary metabolites and are rich in carbohydrates, including those derived from cell wall components, such as hemicelluloses. Depending on the extraction conditions, the total content of hydroxyl groups varies in the range of 24-30% for black alder bark extracts and in the range of 21-26% for pine bark extracts.
In order to evaluate the potential application of extracted bark residues as fillers for PU foams, with the ability to enhance the properties of polymer composites while reducing the environmental impact associated with their disposal, their composition was analysed using analytical pyrolysis (Py-GC-MS/FID), FTIR and wet chemistry methods. The solid residues obtained after bark extraction exhibit an enrichment of lignin compared to the initial bark. Consequently, we propose that incorporating bark extraction residues as fillers in polyurethane foam formulations will offer natural fire retardancy by forming a protective charcoal layer on the material surface during high-temperature oxidation.
