Mechanochemical activation of cellulose and its thermoplastic polyvinyl alcohol ecocomposites with enhanced physicochemical properties

Fabrication and mechanical modelling of dissolvable PVA/PVP composite microneedles with biocompatibility for efficient transdermal delivery of ibuprofen

Microneedles offer minimally invasive, user-friendly, and subcutaneously accessible transdermal drug delivery and have been widely investigated as an effective transdermal delivery system. Ibuprofen is a common anti-inflammatory drug to treat chronic inflammation. It is crucial to develop microneedle patches capable of efficiently delivering ibuprofen through the skin for the effective treatment of arthritis patients requiring repeated medication. In this study, the mechanical properties of a new type of polymer microneedle were studied by finite element analysis, and the experimental results showed that the microneedle could effectively deliver drugs through the skin. In addition, a high ibuprofen-loaded microneedle patch was successfully prepared by micromolding and subjected to evaluation of its infrared spectrum morphology and dissolve degree. The morphology of microneedles was characterized by scanning electron microscopy, and the mechanical properties were assessed using a built linear stretching system. In the in-vitro diffusion cell drug release test, the microneedle released 85.2 ± 1.52% (210 ± 3.7 μg) ibuprofen in the modified Franz diffusion within 4 h, exhibiting a higher drug release compared to other drug delivery methods. This study provides a portable, safe and efficient treatment approach for arthritis patients requiring daily repeated medication.

Melt-processable polyvinyl alcohol/lignin composites with improved strength via synergistic plasticization of lignin

The characteristics of multi-hydroxyl structure and strong hydrogen bonding in polyvinyl alcohol (PVA) make its melting point close to its decomposition temperature, causing melt-processing difficulty. In this work, following the plasticization of small-molecule primary plasticizer acetamide, lignin was demonstrated as a green secondary plasticizer in realizing the melt processing and simultaneous reinforcement of PVA. During the plasticization process, lignin was able to combine with the hydroxyl groups of PVA, so as to destroy the hydrogen bonds and regularity of the PVA chains. The synergistic plasticization effect of lignin dramatically reduced the melting point of PVA from 185 °C to 151 °C. The thermal processing window of PVA composites was expanded from 50 °C to roughly 80 °C after introducing lignin. In contrast to acetamide, the addition of lignin significantly increased the tensile strength and Young's modulus of the composites to 71 MPa and 1.34 GPa, respectively. Meanwhile, lignin helped to hinder the migration of acetamide via hydrogen bonds. With the addition of lignin, the composites also displayed enhanced hydrophobicity and excellent UV shielding performance. The strategy of synergistic plasticization of lignin provides a feasible basis for the practical application of lignin in melt-processable PVA materials with good comprehensive properties.

In situ preparation and properties of polyvinyl alcohol/synthetic ribbon-like nanocellulose composites

This study presents a novel approach in which a dual network (DN) composite, comprising polyvinyl alcohol (PVA) and ribbon-like nanocellulose (RC), was synthesized in one step using the volume exclusion effect involved in enzyme-catalyzed cellulose synthesis. Additionally, the impact of PVA as a crowding reagent during enzymatic catalysis on the in situ formation of nanocellulose and its resulting aspect ratio was explored. In contrast, the other two composites were created by incorporating enzyme-catalyzed synthetic block cellulose (BC) and its acid-hydrolyzed regenerated disc-shaped cellulose (DC) into the PVA. Subsequently, the mechanism by which three distinct types of nanocellulose, varying in morphology and size, was explored to elucidate their contributions to enhancing the properties of PVA. The results demonstrated that PVA/RC outperformed PVA/BC and PVA/DC. The elevated aspect ratio and intricate network structure of RCs not only significantly bolster the mechanical robustness of PVA/RC, leading in an 86.40 % surge in tensile strength and a remarkable 277.03 % rise in tensile modulus in comparison to pure PVA, but also induce a slight enhancement in elongation at break. Moreover, the thermal stability and biodegradability of PVA/RC was enhanced. Collectively, this study introduces an innovative strategy for the efficient fabrication of biodegradable composites with enhanced properties.

Development of nanocellulose fiber reinforced starch biopolymer composites: a review

In the last few years, there are rising numbers for environmental waste due to factors such as plastic based food packaging that really need to get enough attention in order to prevent the issue from becoming worse and bringing disaster to society. Thus, the uses of plastic composite materials need to be reduced and need to be replaced with materials that are natural and have low degradation to preserve nature. Based on the statistics for the global, the production of plastic has been roughly calculated for passing 400 million metric tons every year and has a high probability of approaching the value of 500 million metric tons at the year of 2025 and this issue needs to be counteracted as soon as possible. Due to that, the increasing number for recent development of natural biopolymer, as an example starch, has been investigated as the substitution for the non-biodegradable biopolymer. Besides, among all biodegradable polymers, starch has been considered as promising substitution polymer due to its renewability, easy availability, and biodegradability. Apart from that, by the reinforcement from the nanocellulose, starch fiber has an increasing in terms of mechanical, barrier and thermal properties. In this review paper, we will be discussing the up-to-date development of nanocellulose fiber reinforced starch biopolymer composites throughout this century.

Biodegradable Nonwovens with Poultry Feather Addition as a Method for Recycling and Waste Management

Geotextiles are used for separation, drainage, filtration and anti-erosion protection sealing, as well as to improve plant vegetation conditions. The research objective of this study was to verify the influence of the addition of poultry feathers on accelerating the biodegradation of nonwovens in cultivated soil. The tests were carried out in laboratory conditions and were based on the assessment of weight loss. The experiments confirmed the positive effects of the presence of waste that was rich in keratin on the time required for the biodegradation of the tested materials (the period of biodegradation was 8-24 weeks). Additionally, the influence of the biodegradation of the tested materials on the ecotoxicity was investigated and showed no negative effects on the microbiological activity (106 cfu). The research also included the determination of the carbon to nitrogen ratio of the test medium (blank, 12-14:1; with feather addition, 19-20:1). A statistical analysis revealed a correlation between the mechanical properties and the period of biological decomposition. This research was an important step for the management of poultry feather waste in agricultural applications. The tested materials could be seen an alternative that meets all ecological criteria, which seems to be a golden solution that not only allows the delivery of important nutrients to the soil, but also manages waste in an environmentally safe manner.

Development of Quebracho (Schinopsis balansae) Tannin-Based Thermoset Resins

One of the major challenges currently in the field of material science is finding natural alternatives to the high-performing plastics developed in the last century. Consumers trust synthetic products for their excellent properties, but they are becoming aware of their impact on the planet. One of the most attractive precursors for natural polymers is tannin extracts and in particular condensed tannins. Quebracho (Schinopsis balansae) extract is one of the few industrially available flavonoids and can be exploited as a building block for thermoset resins due to its phenol-like reactivity. The aim of this study was to systematically investigate different hardeners and evaluate the water resistance, thermal behavior, and chemical structure of the quebracho tannin-based polymers in order to understand their suitability as adhesives. It was observed that around 80% of the extract is resistant to leaching when 5% of formaldehyde or hexamine or 10% of glyoxal or furfural are added. Additionally, furfuryl alcohol guarantees high leaching resistance, but only at higher proportions (20%). The quebracho-based formulations showed specific thermal behavior during hardening and higher degradation resistance than the extract. Finally, these polymers undergo similar chemistry to those of mimosa, with exclusive reactivity of the A-ring of the flavonoid.

Green composites based on Atriplex halimus fibers and PLA matrix

This work focuses on the potential use of cellulose fibers extracted from Mediterranean saltbush (Atriplex halimus) as a filler in the polymeric matrix. The fully biodegradable composites were prepared from polylactic acid (PLA) as matrix and microcellulose fibers ranging from 0 to 15 wt.%. The influence of the fiber content on the structure, mechanical, thermal, and water absorption properties was evaluated. Mechanical results indicated that fibers acted effectively as reinforcement, increasing the tensile strength and the Young’s modulus of PLA by 25 and 45%, respectively. This is due to the good stress transfer between fibers and matrix through the strong interactions that have been evidenced by Fourier Transform Infrared (FTIR) spectroscopy. The thermogravimetric analysis showed that PLA composites have a slightly lower degradation temperature than the pure PLA, but they still have favorable thermal stability. Water absorption measurements and biodegradability tests showed that the addition of fibers accelerates degradation kinetics and confirm that the prepared composites are an environmentally safe material suited for different applications.

Self-Healable Conductive Nanocellulose Nanocomposites for Biocompatible Electronic Skin Sensor Systems

Electronic skins are developed for applications such as biomedical sensors, robotic prosthetics, and human-machine interactions, which raise the interest in composite materials that possess both flexibility and sensing properties. Polypyrrole-coated cellulose nanocrystals and cellulose nanofibers were prepared using iron(III) chloride (FeCl₃) oxidant, which were used to reinforce polyvinyl alcohol (PVA). The combination of weak H-bonds and iron coordination bonds and the synergistic effect of these components yielded self-healing nanocomposite films with robust mechanical strength (409% increase compared to pure PVA and high toughness up to 407.1%) and excellent adhesion (9670 times greater than its own weight) to various substrates in air and water. When damaged, the nanocomposite films displayed good mechanical (72.0-76.3%) and conductive (54.9-91.2%) recovery after a healing time of 30 min. More importantly, the flexible nanocomposites possessed high strain sensitivity under subtle strains (<48.5%) with a gauge factor (GF) of 2.52, which was relatively larger than the GF of ionic hydrogel-based skin sensors. These nanocomposite films possessed superior sensing performance for real-time monitoring of large and subtle human motions (finger bending motions, swallowing, and wrist pulse); thus, they have great potentials in health monitoring, smart flexible skin sensors. and wearable electronic devices.

Mechanically Strong, Heat-Resistant, Water-Induced Shape Memory Poly(vinyl alcohol)/Regenerated Cellulose Biocomposites via a Facile Co-precipitation Method

In this work, poly(vinyl alcohol) (PVA) biocomposites with regenerated cellulose-softwood pulp (RC-SP) as a green reinforcement were prepared via co-precipitation method. Simultaneous precipitation of the two components promotes uniform dispersion of the RC-SP and constructs strong molecular chain entanglements and hydrogen bonding network inside the composites. This physical cross-linking network reduces the water absorption and improves the water resistance of the composites. The incorporation of RC-SP not only improves the thermal decomposition properties of the composites, but also enhances the mechanical properties and dynamic mechanical properties, attributed to the strong interaction between the filler and the matrix. Moreover, the fabricated PVA/RC-SP composites exhibit good water-induced shape memory effect, and shape recovery rate of 10% RC-SP reinforced composite reaches 95.3% after immersing for 35 min. This work provides useful information for the implementation of co-precipitation method and the application of renewable cellulose resources.

Modulable properties of PVA/cellulose fiber composites

PURPOSE:

Development of PVA/cellulose fiber composite material with modulable properties, obtained through the increase of reinforcement and heat treatments in order to optimize the composite in terms of mechanical, thermal, and degradation properties.

METHODS:

The composite was designed selecting as matrix an experimental formulation based on water-soluble, biodegradable, polyvinyl alcohol (PVA) and microcrystalline cellulose (MCC), as reinforcement. Six different formulations, with increasing ratio of MCC content (from 0% to 55% w/w) in PVA, were developed and extruded by a co-rotating twin-screw extruder (TSA FSCM 21/40). Then, samples have been treated through two different thermal conditions (T1, T2) and characterized by scanning electron microscopy, tensile mechanical tests, thermogravimetric analysis, and water degradation tests to investigate, respectively, the influence of MCC ratios and heat treatment on morphological, mechanical, degradation, and thermal properties.

RESULTS:

The PVA/MCC composite exhibited a good stress-strain behavior as well as a close correlation between MCC content on tensile, thermal, and degradation properties. The second part of the results includes the analysis of the effects that the thermal treatments (T1, T2) had on the composite. In fact, thermal treatments have allowed improving the thermal and water stability as well as a significant improvement in the considered mechanical parameters due to a possible crosslinking of the PVA matrix.

CONCLUSION:

The present work shows how the properties of the PVA/MCC composite can become modular with the aim of extending its range of application as a new sustainable solution in the field of consumer products.

Water-soluble polymeric xenobiotics - Polyvinyl alcohol and polyvinylpyrrolidon - And potential solutions to environmental issues: A brief review

This paper describes a potential environmental problem closely linked with the global production of water-soluble polymers such as polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP). Both polymers make up the components of a multitude of products commonly utilized by industries and households. Hence, such a widespread use of PVA and PVP in the industrial sector and among consumers (the concentration of PVP in urban wastewater is approximately 7 mg/L) could pose a considerable problem, particularly to the environment. To this end, many publications have recently highlighted the poor biodegradability of PVA, in principle influenced by numerous biotic and abiotic factors. Facts published on the environmental fate of PVP have been scant, basically reporting that it is a biologically resistant polymer. As a result, the commercially produced water-soluble polymers of PVA and PVP are essentially non-biodegradable and possess the capacity to accumulate in virtually all environmental media. Consequently, there is a chance of heightened risk to the very environmental constituents in which PVA and PVP accumulate, depending on the routes of entry and transformation processes underway in such constituents of the ecosystem. This assumption is confirmed by the findings of initial research, which is worrying. Herein, PVA was detected in a soil environment, while a relatively high concentration of PVP was found in river water. A review of the literature was conducted to summarize the current state of knowledge concerning the fate of PVA and PVP in various environments, thereby also discerning potential solutions to tackle such dangers. This paper proposes methods to enhance the biodegradability of materials containing such materials; for PVA this means utilizing a suitable polysaccharide, whereas for PVP this pertains to actuating applications that induce substances to degrade. Accordingly, while it is understandable that this work cannot fully address all the issues associated with polymeric xenobiotics, it can still serve as a guide to discerning an economically viable solution, and provide a foundation for further research.

Dynamic and creep analysis of polyvinyl alcohol based films blended with starch and protein

The present study focuses on the fabrication and analyses of polyvinyl alcohol (PVA) based films blended with polymers, such as starch and protein. The aim is to improve the moisture absorption, solubility, mechanical and thermal properties of PVA by blending it with various polymers. The thermal cross-linking of the films has been studied by heating the films at 120°C for 4 h. The result shows that PVA was completely soluble in water, while post-blending solubility and moisture absorption of blended films decreased. The tensile strength of blended films was significantly higher (4%–29%) as compared to neat PVA, while thermally cross-linked films showed much higher strength (8%–174%). Blended films were characterized using Fourier transform infrared spectroscopy (FTIR) to confirm the formation of hydrogen bonds. Thermogravimetric analysis showed the increase in degradation temperature post-blending as compared to neat PVA. The viscoelastic behavior of the material as well as glass transition temperature was studied using dynamic mechanical analysis. Creep and recovery behavior were examined to study the effect of stress and temperature on creep strain. The biodegradability of the blended films was increased post-blending. This study showed that PVA based blend films can replace non-biodegradable plastics and hence are necessary for the development of environmentally friendly materials.

Facile Fabrication of 100% Bio-based and Degradable Ternary Cellulose/PHBV/PLA Composites

Modifying bio-based degradable polymers such as polylactide (PLA) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) with non-degradable agents will compromise the 100% degradability of their resultant composites. This work developed a facile and solvent-free route in order to fabricate 100% bio-based and degradable ternary cellulose/PHBV/PLA composite materials. The effects of ball milling on the physicochemical properties of pulp cellulose fibers, and the ball-milled cellulose particles on the morphology and mechanical properties of PHBV/PLA blends, were investigated experimentally and statistically. The results showed that more ball-milling time resulted in a smaller particle size and lower crystallinity by way of mechanical disintegration. Filling PHBV/PLA blends with the ball-milled celluloses dramatically increased the stiffness at all of the levels of particle size and filling content, and improved their elongation at the break and fracture work at certain levels of particle size and filling content. It was also found that the high filling content of the ball-milled cellulose particles was detrimental to the mechanical properties for the resultant composite materials. The ternary cellulose/PHBV/PLA composite materials have some potential applications, such as in packaging materials and automobile inner decoration parts. Furthermore, filling content contributes more to the variations of their mechanical properties than particle size does. Statistical analysis combined with experimental tests provide a new pathway to quantitatively evaluate the effects of multiple variables on a specific property, and figure out the dominant one for the resultant composite materials.

Novel superabsorbent membranes made of PVA and Ziziphus spina-christi cellulose for agricultural and horticultural applications

Novel superabsorbent membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) from Ziziphus spina-christi fibers (ZSP-fibers), glutaraldehyde (GLA) and glycerin (G) were prepared using a Hydraulic Lamination Hot Press machine.

Poly-Paper: A Sustainable Material for Packaging, Based on Recycled Paper and Recyclable with Paper

Background

Until now, environmental sustainability issues are almost entirely unsolved for packaging materials. With the final aim of finding materials with a single recycling channel, cellulose fiber/poly(vinyl)alcohol composites were investigated.

Methods

After extrusion and injection molding, samples of composite with different cellulose fiber content (30%, 50% and 70% w/w) were tested.

Results

Tensile mechanical tests exhibited an improvement in composite stiffness when the reinforcement content was increased together with a decrease in composite elongation. Solubility tests performed at room temperature and 45°C showed different behavior depending on the water-resistant film applied on the composite (50% cellulose fiber content). In particular, the uncoated composite showed complete solubility after 2 hours, whereas at the same time point, no solubility occurred when a non-water-soluble varnish was used.

Conclusions

The proposed composites, named Poly-paper, appear to warrant further investigation as highly sustainable packaging.

Highly percolated poly(vinyl alcohol) and bacterial nanocellulose synthesized in situ by physical-crosslinking: exploiting polymer synergies for biomedical nanocomposites

Bacterial cellulose (BC) grown from a culture medium in the presence of water-soluble poly(vinyl alcohol) (PVA) produced an assemblage that was used as precursor for the synthesis of biocompatible nanocomposites.

Effective dispersion and crosslinking in PVA/cellulose fiber biocomposites via solid-state mechanochemistry

A mechanochemical approach to improve the dispersion and the degree of crosslinking between cellulose fiber and polymer matrix is presented herein to create high performance poly(vinyl alcohol) (PVA)/cellulose biocomposites in a solvent-free and catalyst-free system. During a pan-milling process, the hydrogen bonds in both cellulose and PVA were effectively broken up, and the released hydroxyl groups could react with succinic anhydride (SA) to form covalent bonds between the two components. This stress-induced chemical reaction was verified by fourier transform infrared spectroscopy. The reaction kinetics was discussed according to the conversion rate of SA during the pan-milling process. Soxhlet extraction with hot water showed that the crosslinked PVA/cellulose retained more PVA in the composites due to the homogeneous and heterogeneous crosslinking. Scanning electron microscope images indicated the dispersion and interfacial interactions between PVA and cellulose were largely improved. The resulting composites exhibited remarkably enhanced mechanical properties. The tensile strength increased from 8.8 MPa (without mechanochemical treatment) to 18.2 MPa, and elongation at break increased from 76.8 to 361.7% after the treatment. Their thermal stability was also significantly improved.

High-water-content mouldable polyvinyl alcohol-borax hydrogels reinforced by well-dispersed cellulose nanoparticles: dynamic rheological properties and hydrogel formation mechanism

Cellulose nanoparticle (CNP) reinforced polyvinyl alcohol-borax (PB) hydrogels were produced via a facile approach in an aqueous system. The effects of particle size, aspect ratio, crystal structure, and surface charge of CNPs on the rheological properties of the composite hydrogels were investigated. The rheological measurements confirmed the incorporation of well-dispersed CNPs to PB system significantly enhanced the viscoelasticity and stiffness of hydrogels. The obtained free-standing, high elasticity and mouldable hydrogels exhibited self-recovery under continuous step strain and thermo-reversibility under temperature sweep. With the addition of cellulose I nanofibers, a 19-fold increase in the high-frequency plateau of storage modulus was obtained compared with that of the pure PB. CNPs acted as multifunctional crosslinking agents and nanofillers to physically and chemically bridge the 3D network hydrogel. The plausible mechanism for the multi-complexation between CNPs, polyvinyl alcohol and borax was proposed to understand the relationship between the 3D network and hydrogel properties.