Lignin and Xylan as interface engineering additives for improved environmental durability of sustainable cellulose nanopapers

Cellulose materials and products are frequently affected by environmental factors such as light, temperature, and humidity. Simulated UV irradiation, heat, and moisture exposure were comprehensively used to characterize changes in cellulose nanopaper (NP) tensile properties. For the preparation of NP, high-purity cellulose from old, unused filter paper waste was used. Lignin and xylan were used as sustainable green interface engineering modifiers for NP due to their structural compatibility, low price, nontoxic nature, and abundance as a by-product of biomass processing, as well as their ability to protect cellulose fibers from UV irradiation. Nanofibrillated cellulose (NFC) suspension was obtained by microfluidizing cellulose suspension, and NP was produced by casting films from water suspensions. The use of filler from 1 to 30 wt% significantly altered NP properties. All nanopapers were tested for their sensitivity to water humidity, which reduced mechanical properties from 10 to 40% depending on the saturation level. Xylan addition showed a significant increase in the specific elastic modulus and specific strength by 1.4- and 2.8-fold, respectively. Xylan-containing NPs had remarkable resistance to UV irradiation, retaining 50 to 90% of their initial properties. Lignin-modified NPs resulted in a decreased mechanical performance due to the particle structure of the filler and the agglomeration process, but it was compensated by good property retention and enhanced elongation. The UV oxidation process of the NP interface was studied with UV-Vis and FTIR spectroscopy, which showed that the degradation of lignin and xylan preserves a cellulose fiber structure. Scanning electron microscopy images revealed the structural formation of the interface and supplemented understanding of UV aging impact on the surface and penetration depth in the cross-section. The ability to overcome premature aging in environmental factors can significantly benefit the wide adaption of NP in food packaging and functional applications

Highly loaded cellulose/poly (butylene succinate) sustainable composites for woody-like advanced materials application

We report the manufacturing and characterization of poly (butylene succinate) (PBS) and micro cellulose (MCC) woody-like composites. These composites can be applied as a sustainable woody-like composite alternative to conventional fossil polymer-based wood-plastic composites (WPC). The PBS/MCC composites were prepared by using a melt blending of 70 wt% of MCC processed from bleached softwood. MCC was modified to enhance dispersion and compatibility by way of carbodiimide (CDI), polyhydroxy amides (PHA), alkyl ester (EST), (3-Aminopropyl) trimethoxysilane (APTMS), maleic acid anhydride (MAH), and polymeric diphenylmethane diisocyanate (PMDI). The addition of filler into PBS led to a 4.5-fold improvement of Young’s modulus E for the MCC composite, in comparison to neat PBS. The 1.6-fold increase of E was obtained for CDI modified composition in comparison to the unmodified MCC composite. At room temperature, the storage modulus E′ was found to improve by almost 4-fold for the APTMS composite. The EST composite showed a pronounced enhancement in viscoelasticity properties due to the introduction of flexible long alkyl chains in comparison to other compositions. The glass transition temperature was directly affected by the composition and its value was −15 °C for PBS, −30 °C for EST, and −10 °C for MAH composites. FTIR indicated the generation of strong bonding between the polymer and cellulose components in the composite. Scanning electron microscopy analysis evidenced the agglomeration of the MCC in the PBS/MCC composites. PMDI, APTMS, and CDI composites were characterized by the uniform dispersion of MCC particles and a decrease of polymer crystallinity. MCC chemical modification induced the enhancement of the thermal stability of MCC composites

Polipropilēna – titāna dioksīda daļiņu nanokompozītu izpēte

Darbā apskatīti polipropilēns, titāna dioksīds, to īpašības un struktūra, kā arī polipropilēna nanokompozītu iegūšana. Pētījumā ir iegūti un izpētīti PP/TiO2 nanokompozīti, noteikta izturība pret UV starojumu

Preparation and Characterization of Hot-Pressed Li + Ion Conducting PEO Composite Electrolytes

Preparation and characterization of hot-pressed Li+ ion conducting Polyethylene oxide (PEO) composite electrolytes are discussed in this paper. Lithium trifluoromethanesulfonate with linear formula CF3SO3Li is selected as Li+ ion source for polymer composite electrolyte processing. Polyethylene oxide as matrix for polymer electrolyte is selected, because of its cation solvatation and salt complexes formation partibility. Nano-sized fillers such as carbon nanotube (CNT) and graphene (GR) are introduced to polymeric composite to improve PEO electrolyte mechanical properties. The composites were prepared from PEO, CF3SO3LP CNT and GR by solution casting and by hot-pressing method. Influence of CF3SO3LP CNT and GR concentrations on the electrical, thermal and mechanical properties of PEO composite is investigated and discussed. The additives addition to the PEO matrix improves the electrical, thermal and mechanical properties of the composite. The crystallinity of the PEO decreases

Polietilēna oksīda gēlu pagatavošana un izpēte

Darbā iegūti polietilēna oksīda (PEO) gēli, izmantojot ķīmiskās šķērssaistīšanas metodi. Pētīta šķērssaistīšanas aģenta koncentrācijas un nanodaļiņu pievienošanas ietekme uz gēlu uzbriešanas pakāpi, difūzijas koeficientu, gēla frakciju un gēla režģu struktūru, kā arī dielektriskajām īpašībām. Literatūras apskatā apkopota informācija par PEO, gēlu iegūšanas metodēm, superabsorbentiem un nanokompozītu gēliem. Literatūra apkopota par laika periodu no 1990. līdz 2013. gadam

Polietilēna oksīda kristalizācijas pētījumi

Darba literatūras apskatā tika apskatīta polimēru kristalizācija plānās kārtiņās veidojošās struktūras un kristalizācijas kinētika. Apskatīti faktori, kas ietekmēja polimēru kristalizāciju plānās kārtiņās. Eksperimentālajā daļā tika iegūtas dažādas koncentrācijas polietilēna oksīda plānās kārtiņas. Iegūšanas procesā dažām no plānajām kārtiņām tika pievienotas nanodaļiņas.Iegūtās plānās kārtiņas tika pētītas ar optisko mikroskopiju, atomspēku mikroskopiju un rentgendifrakcijas iekārtu