@article{dosSantos2024,

title = {Kraft lignin-based polyurethanes: Bulk properties, stability and adhesion to native aluminum surfaces},

author = {Demetrio Jackson dos Santos and Lara B. Tavares and Leonardo D. Antonino and Rogerio R. de Sousa Junior and Paula Homem-de-Mello and Cedric R. Leão},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0032386124007936},

doi = {10.1016/j.polymer.2024.127457},

issn = {0032-3861},

year  = {2024},

date = {2024-09-00},

urldate = {2024-09-00},

journal = {Polymer},

volume = {309},

publisher = {Elsevier BV},

abstract = {Lignin as a byproduct from pulp and paper manufacturing has been extensively investigated as raw material for polymer developments. Although, fundamental topics related to the adhesion mechanisms of lignin-based reactive polyurethanes (LPU) still remain unclear. In this work, LPU thin films on native aluminum surface were prepared and characterized. Diluted in THF, employed as the solvent, reactive mixtures of 4,4′-methylene diphenyl isocyanate (4,4′-MDI) and the soluble fraction of three lignins (liquid hydroxypropylated Kraft lignin and two powder Kraft lignins with different pH) were used for LPU thin film deposition via spin coating on aluminum (PVD layer on silicon wafer). The resulting film thickness ranged from 8 nm to several micrometers. The chemical state of the three LPU compositions was assessed in bulk by infrared attenuated total reflectance (IR-ATR) and in the thin films by infrared external reflection absorption spectroscopy (IR-ERAS). Binding energies of 4,4′-methylene diphenyl diisocyanate with aliphatic and aromatic hydroxyl groups were estimated using Density Functional Theory (DFT) simulations. Thus, besides the elucidation of the bulk chemical state of LPUs, the relation to adhesion and stability of LPUs to a native aluminum surface was evaluated. In addition, film topography and homogeneity were monitored by SFM. All lignin types form uniform and homogeneous films. Results revealed a higher consumption of isocyanate groups (NCO) in the formulation with the alkaline Kraft lignin than with the acid one, despite its lower hydroxyl content. A gradient of unreacted NCO was observed in LPU thin films obtained with the powder Kraft lignin types. Residual NCO is also found in thicker films, while the thinnest films did not contain unreacted NCO anymore, indicating the activating effect of the native aluminum surface on LPU formation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Garcia2024b,

title = {Graphene Oxide-Based Nanocomposites for Stereolithography (SLA) 3D Printing: Comprehensive Mechanical Characterization under Combined Loading Modes},

author = {Guilherme Elias Saltarelli Garcia and Rogerio Ramos de Sousa Junior and Julia Rocha Gouveia and Demetrio Jackson dos Santos},

url = {https://www.mdpi.com/2073-4360/16/9/1261},

doi = {10.3390/polym16091261},

issn = {2073-4360},

year  = {2024},

date = {2024-05-00},

urldate = {2024-05-00},

journal = {Polymers},

volume = {16},

number = {9},

publisher = {MDPI AG},

abstract = {Additive manufacturing, particularly Stereolithography (SLA), has gained widespread attention thanks to its ability to produce intricate parts with high precision and customization capacity. Nevertheless, the inherent low mechanical properties of SLA-printed parts limit their use in high-value applications. One approach to enhance these properties involves the incorporation of nanomaterials, with graphene oxide (GO) being a widely studied option. However, the characterization of SLA-printed GO nanocomposites under various stress loadings remains underexplored in the literature, despite being essential for evaluating their mechanical performance in applications. This study aimed to address this gap by synthesizing GO and incorporating it into a commercial SLA resin at different concentrations (0.2, 0.5, and 1 wt.%). Printed specimens were subjected to pure tension, combined stresses, and pure shear stress modes for comprehensive mechanical characterization. Additionally, failure criteria were provided using the Drucker-–Prager model.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Santos2024b,

title = {Self-healing epoxy coatings via microencapsulation of aromatic diisocyanate in lignin stabilized Pickering emulsions},

author = {Amanda N.B. Santos and Júlia R. Gouveia and Guilherme E.S. Garcia and Renato A. Antunes and Demetrio Jackson dos Santos and Danilo J. Carastan},

url = {https://www.sciencedirect.com/science/article/pii/S294982282400073X},

doi = {10.1016/j.nxmate.2024.100176},

issn = {2949-8228},

year  = {2024},

date = {2024-04-00},

urldate = {2024-04-00},

journal = {Next Materials},

volume = {3},

publisher = {Elsevier BV},

abstract = {Isocyanate-filled microcapsules are gaining increased attention for their role in developing self-healing materials, thereby reducing maintenance costs and increasing polymer durability. Nevertheless, microencapsulating highly reactive -NCO groups remains a challenging task in the literature. Likewise, considerable efforts have been directed towards developing polymers from renewable and biobased sources, which could also be applied to microcapsule synthesis. In this work, lignin, an abundant biopolymer, was used as a solid stabilizer for oil-in-water (O/W) interfaces, enabling the encapsulation of highly reactive isocyanate. Hybrid polyurethane/polyurea microcapsules containing reactive methylenediphenyl diisocyanate (MDI) were obtained via optimized O/W Pickering emulsions using lignin for system stabilization. This optimized process facilitated shell formation via the reaction of diisocyanate with lignin and water, eliminating the need for additional chain extenders. Scanning electron microscopy revealed the formation of spherical and rough microcapsules, while infrared spectroscopy confirmed the presence of residual free -NCO groups, indicating effective encapsulation of MDI. Additionally, a core -NCO concentration of 11 wt% was confirmed by titration. The microcapsules were further assessed as components in self-healing epoxy coatings. Their incorporation resulted in the retardation of corrosion on a low carbon steel panel after 72 h of submersion in a saline solution. Electrochemical impedance spectroscopy (EIS) confirmed a significant increase of approximated 620% in impedance modulus after 83 days of immersion in a 3.5 wt% NaCl solution, compared to the neat epoxy coating. These findings suggest a promising technological application of this material for the advancement of self-healing epoxy-based coatings and composites.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Garcia2024,

title = {Pyrolytic lignin fractionation for rigid polyurethane foams: Relationship between the Pyrolysate's chemical structure and foam properties},

author = {Guilherme E.S. Garcia and Antje Potthast and Ivan Sumerskii and Leonardo D. Antonino and Matheus M. de Oliveira and Rogerio R. de Sousa and Thomas Rosenau and Demetrio Jackson dos Santos},

url = {https://www.sciencedirect.com/science/article/pii/S2949839224000087},

doi = {10.1016/j.scenv.2024.100065},

issn = {2949-8392},

year  = {2024},

date = {2024-03-00},

urldate = {2024-03-00},

journal = {Sustainable Chemistry for the Environment},

volume = {5},

publisher = {Elsevier BV},

abstract = {Pyrolytic lignin (PL) has emerged as a promising renewable material for the production of polyurethanes (PU) due to the high concentration of hydroxyl groups in its structure, being a potential substitute for petroleum-based polyols. On one hand, the high functionality and liquid form of PL favor its application as a polyol in PU formulations. On the other hand, the inherent heterogeneity of PL still imposes a challenge for the development of new materials with reproducible properties. In this work, aiming to overcome these limitations, an acetone-water fractionation process was successfully used to fractionate PL. The resulting fractions were analytically characterized by HSQC NMR, 31P NMR and rheological analysis, revealing significant structural and compositional differences. Afterwards, these fractions partially replaced an industrial polyether polyol in the formulation of rigid PU foams. Finally, microstructure and mechanical properties of these foams were evaluated by SEM and uniaxial compressive tests. The lignin-based foams exhibited reduced cell size and improved mechanical properties compared to the reference foam (based on a polyether polyol). Thus, the mechanical properties of PU foams can be enhanced through the selection of specific PL fractions. These results highlight the potential of PL fractions as a sustainable and viable alternative to industrial polyols for PU foams with improved properties.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Fernando2023,

title = {Effects of the incorporation of modified kraft lignin on the mechanical properties of epoxy adhesive: experimental and theoretical approaches},

author = {Paulo H.L. Fernando and Leonardo D. Antonino and Guilherme E.S. Garcia and Rogerio R. de Sousa Júnior and Antonio V. Neto and Francisco Y. Nakamoto and Demetrio Jackson dos Santos},

url = {https://www.tandfonline.com/doi/full/10.1080/00218464.2023.2194535},

doi = {10.1080/00218464.2023.2194535},

issn = {1545-5823},

year  = {2024},

date = {2024-01-25},

urldate = {2024-01-25},

journal = {The Journal of Adhesion},

volume = {100},

number = {2},

pages = {83--95},

publisher = {Informa UK Limited},

abstract = {Several lignin-based adhesives were developed during the last decades. More recently, lignin isolation methods were improved, leading to technical grade lignins with constant properties. This recent scenario created the required conditions for the industrial use of lignin in adhesive applications, at large scale, with reliable properties. In this work, technical grade kraft lignin was epoxidized and incorporated in industrial epoxy resin, resulting into a partly biobased epoxy resin. Notwithstanding, the mechanical properties of cured partly biobased epoxy were investigated using Arcan device, aiming to reproduce realistic load conditions for the adhesively bonded joints. At last, failure envelopes were obtained from Drucker–Prager and von Mises models, revealing the most reliable model to calculate the failure prediction. Results pointed out to the development of a partly biobased epoxy adhesive with slightly superior mechanical properties, in comparison with industrial epoxy adhesive. Indeed, an important contribution was provided for the lignin revalorization and the mechanical characterization and failure prediction of epoxy adhesive based on the modified lignin.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{deSousaJúnior2023c,

title = {Viscoelastic behavior of pressure-sensitive adhesive based on block copolymer and kraft lignin},

author = {Rogerio R. de Sousa Júnior and Guilherme E.S. Garcia and Demetrio Jackson dos Santos and Danilo J. Carastan},

url = {https://www.tandfonline.com/doi/abs/10.1080/00218464.2023.2201443},

doi = {10.1080/00218464.2023.2201443},

issn = {1545-5823},

year  = {2024},

date = {2024-01-25},

urldate = {2024-01-25},

journal = {The Journal of Adhesion},

volume = {100},

number = {2},

pages = {139--155},

publisher = {Informa UK Limited},

abstract = {Practical adhesion of pressure-sensitive adhesives (PSAs) is strongly dependent on their viscoelastic properties. The use of biobased materials emerged as an effective approach to modify the rheological, mechanical, and adhesive properties of PSAs. The biopolymer kraft lignin (KL), a by-product of pulp and paper manufacturing, appeared as a potential candidate for modifying the adhesive behavior of PSAs. In this study, we developed a block copolymer-based PSA by incorporating a hydrocarbon resin (HCR) and kraft lignin into the block copolymer polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS). “Viscoelastic windows”, which describe the potential application of a PSA based on its viscoelastic behavior, were constructed for PSAs with the addition of KL. These results demonstrate the potential for application as a high-shear PSA due to the increased energy dissipation of the samples. Practical adhesion was evaluated using probe tack tests and lap shear strength measurements, which effectively demonstrated an increase in the cohesive strength of the PSA with an optimized concentration of 5 wt% KL.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ito2024,

title = {Synthesis of silver nanoparticles using modified lignin as a reducing agent},

author = {Nathalie Minako Ito and Anibal de Andrade Mendes Filho and Demetrio Jackson dos Santos and Lara Tavares dos Santos},

url = {https://www.sciencedirect.com/science/article/pii/S2949822823001016},

doi = {10.1016/j.nxmate.2023.100101},

issn = {2949-8228},

year  = {2024},

date = {2024-01-00},

urldate = {2024-01-00},

journal = {Next Materials},

volume = {2},

publisher = {Elsevier BV},

abstract = {The emergence and spread of microorganisms, posing a significant threat to public health globally, highlights the urgent need for sustainable solutions to combat pathogens. As a result, green synthesis has garnered increasing attention as an eco-friendly and effective approach to developing antimicrobial materials. This study explores the potential of aminated lignin as an alternative material for synthesizing silver nanoparticles, comparing its performance with commonly used kraft lignin. A one-pot green method was successfully employed to synthesize silver nanoparticles using both lignin types. By incorporating amine groups, lignin demonstrated heightened efficacy as a reducing agent, leading to a nearly fourfold increase in the concentration of silver nanoparticles. The silver nanoparticles obtained using aminated lignin displayed an average crystallite size of 50 nm and demonstrated a more uniform morphology, while those obtained using kraft lignin resulted in a smaller crystallite size of 30 nm but a broader nanoparticle size range. The concentration enhancement and improved morphology control underscore the significant impact of using aminated lignin as a reducing agent, emphasizing its potential in advanced materials synthesis. These results provide valuable insights into the utilization of amine-terminated lignin in nanoparticle synthesis and its potential in diverse applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{deSousaJunior2024,

title = {Dielectric elastomers based on SEBS gel: The impact of adding kraft lignin on electro-mechanical performance},

author = {Rogerio Ramos de Sousa Junior and Guilherme Elias Saltarelli Garcia and Leonardo Dalseno Antonino and Júlia Rocha Gouveia and Demetrio Jackson dos Santos and Danilo Justino Carastan},

url = {https://openurl.ebsco.com/EPDB%3Agcd%3A16%3A28306480/detailv2?sid=ebsco%3Aplink%3Ascholar&id=ebsco%3Agcd%3A176598638&crl=c},

doi = {10.3144/expresspolymlett.2024.42},

issn = {1788-618X},

year  = {2024},

date = {2024-00-00},

urldate = {2024-00-00},

journal = {Express Polym. Lett.},

volume = {18},

number = {6},

pages = {561--574},

publisher = {Department of Polymer Engineering, Scientific Society of Mechanical Engineering},

abstract = {Thermoplastic elastomer gels based on styrenic triblock copolymers have been increasingly used as dielectric elastomers, particularly due to the possibility of tailoring their properties based on their composition. However, these materials have a low relative permittivity, primarily attributed to their low dipole moment. Consequently, this characteristic poses a challenge for their application as dielectric elastomers. In this work, we aim to assess the impact of adding kraft lignin on the dielectric properties of thermoplastic elastomer gels. Additionally, we investigate the effects of kraft lignin dispersion on their viscoelastic and mechanical properties. For this purpose, we used two types of kraft lignin: acidic and alkaline (ac-KL and alk-KL). The alk-KL demonstrated higher dispersibility in the polymer, mainly attributed to the deprotonation of its structure during its production process. As a result, the dielectric elastomer with alk-KL showed a 50% increase in relative permittivity compared to the pristine polymer without compromising its mechanical and viscoelastic properties. Moreover, these samples demonstrated a greater actuation strain capability in response to an electrical stimulus. Thus, the incorporation of lignin demonstrates promise as a valuable reinforcement in the development of advanced dielectric materials, enhancing their electro-mechanical performance.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{deSousaJunior2023b,

title = {Characterization of Poly(3-hydroxybutyrate) (P3HB) from Alternative, Scalable (Waste) Feedstocks},

author = {Rogerio Ramos de Sousa Junior and Fabiano Eduardo Marques Cezario and Leonardo Dalseno Antonino and Demetrio Jackson dos Santos and Maximilian Lackner},

url = {https://www.mdpi.com/2306-5354/10/12/1382},

doi = {10.3390/bioengineering10121382},

issn = {2306-5354},

year  = {2023},

date = {2023-12-00},

urldate = {2023-12-00},

journal = {Bioengineering},

volume = {10},

number = {12},

publisher = {MDPI AG},

abstract = {Bioplastics hold significant promise in replacing conventional plastic materials, linked to various serious issues such as fossil resource consumption, microplastic formation, non-degradability, and limited end-of-life options. Among bioplastics, polyhydroxyalkanoates (PHA) emerge as an intriguing class, with poly(3-hydroxybutyrate) (P3HB) being the most utilized. The extensive application of P3HB encounters a challenge due to its high production costs, prompting the investigation of sustainable alternatives, including the utilization of waste and new production routes involving CO2 and CH4. This study provides a valuable comparison of two P3HBs synthesized through distinct routes: one via cyanobacteria (Synechocystis sp. PCC 6714) for photoautotrophic production and the other via methanotrophic bacteria (Methylocystis sp. GB 25) for chemoautotrophic growth. This research evaluates the thermal and mechanical properties, including the aging effect over 21 days, demonstrating that both P3HBs are comparable, exhibiting physical properties similar to standard P3HBs. The results highlight the promising potential of P3HBs obtained through alternative routes as biomaterials, thereby contributing to the transition toward more sustainable alternatives to fossil polymers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Antonino2023,

title = {Lignin-Based Polyurethanes from the Blocked Isocyanate Approach: Synthesis and Characterization},

author = {Leonardo D. Antonino and Ivan Sumerskii and Antje Potthast and Thomas Rosenau and Maria Isabel Felisberti and Demetrio Jackson dos Santos},

url = {https://pubs.acs.org/doi/full/10.1021/acsomega.3c03422},

doi = {10.1021/acsomega.3c03422},

issn = {2470-1343},

year  = {2023},

date = {2023-08-01},

urldate = {2023-08-01},

journal = {ACS Omega},

volume = {8},

number = {30},

pages = {27621--27633},

publisher = {American Chemical Society (ACS)},

abstract = {Lignin, the world’s second most abundant biopolymer, has been investigated as a precursor of polyurethanes due to its high availability and large amount of hydroxyls present in its structure. Lignin-based polyurethanes (LPUs) are usually synthesized from the reaction between lignin, previously modified or not, and diisocyanates. In the present work, LPUs were prepared, for the first time, using the blocked isocyanate approach. For that, unmodified and hydroxypropylated Kraft lignins were reacted with 4,4′-methylene diphenyl diisocyanate in the presence of diisopropylamine (blocking agent). Castor oil was employed as a second polyol. The chemical modification was confirmed by 31P nuclear magnetic resonance (31P NMR) analysis, and the structure of both lignins was elucidated by a bidimensional NMR technique. The LPUs’ prepolymerization kinetics was investigated by temperature-modulated optical refractometry and Fourier-transform infrared spectroscopy. The positive effect of hydroxypropylation on the reactivity of the Kraft lignin was verified. The structure of LPU prepolymers was accessed by bidimensional NMR. The formation of hindered urea-terminated LPU prepolymers was confirmed. From the results, the feasibility of the blocked isocyanate approach to obtain LPUs was proven. Lastly, single-lap shear tests were performed and revealed the potential of LPU prepolymers as monocomponent adhesives.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{deSousaJunior2022,

title = {PHB Processability and Property Improvement with Linear-Chain Polyester Oligomers Used as Plasticizers},

author = {Rogerio Ramos de Sousa Junior and Carlos Alberto Soares dos Santos and Nathalie Minako Ito and Airton Nizetti Suqueira and Maximilian Lackner and Demetrio Jackson dos Santos},

url = {https://www.mdpi.com/2073-4360/14/19/4197},

doi = {10.3390/polym14194197},

issn = {2073-4360},

year  = {2022},

date = {2022-10-00},

urldate = {2022-10-00},

journal = {Polymers},

volume = {14},

number = {19},

publisher = {MDPI AG},

abstract = {In 2021, global petroleum-based plastic production reached over 400 million metric tons (Mt), and the accumulation of these non-biodegradable plastics in the environment is a worldwide concern. Polyhydroxybutyrate (PHB) offers many advantages over traditional petroleum-based plastics, being biobased, completely biodegradable, and non-toxic. However, its production and use are still challenging due to its low deformation capacity and narrow processing window. In this work, two linear-chain polyester oligomers were used as plasticizers to improve the processability and properties of PHB. Thermal analyses, XRD, and polarized optical microscopy were performed to evaluate the plasticizing effect on the PHB and the reflection on the mechanical behavior. Both oligomers acted as PHB plasticizers, with a reduction in Tg and Tm as a function of the plasticizer concentration, which can make it easier to handle the material in thermal processing and reduce the probability of thermal degradation. Plasticizer 2 proved to be the most promising between the two with an optimized condition of 20%, in which there was a decrease in elastic modulus of up to 72% and an increase in the maximum elongation of 467%.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Antonino2022,

title = {Polyurethane adhesives from castor oil and modified lignin via reaction with propylene carbonate},

author = {Leonardo Dalseno Antonino and Guilherme Elias Saltarelli Garcia and Julia Rocha Gouveia and Amanda Nascimento Braga Santos and Manuel Patricio da Silva Bisneto and Demetrio Jackson dos Santos},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/app.52477},

doi = {10.1002/app.52477},

issn = {1097-4628},

year  = {2022},

date = {2022-07-15},

urldate = {2022-07-15},

journal = {J of Applied Polymer Sci},

volume = {139},

number = {27},

publisher = {Wiley},

abstract = {Over the last several years, lignin hydroxypropylation with propylene oxide (PO) has been used as the main strategy to overcome lignin limitations, such as its low reactivity, poor dispersion, and high stiffness, in the context of polyurethane (PU) synthesis. However, PO is a flammable, toxic, and carcinogenic compound. Propylene carbonate (PC), a compound with low toxicity and biodegradability, has emerged as a feasible alternative to PO. Although this compound has potential for use in syntheses, lignin hydroxypropylation with PC has not yet been explored in PU synthesis. In this work, PU adhesives are synthesized using castor oil (CO) and hydroxypropylated lignin via the reaction with PC (HKL_PC) as a polyol. HKL_PC is incorporated in CO at different concentrations (10 wt%, 20 wt%, and 30 wt%). Curing kinetics is investigated with temperature-modulated optical refractometry (TMOR). Dynamic mechanical analysis (DMA) demonstrates an increase in Tg after lignin addition. Furthermore, Young's modulus and practical adhesion are improved with increasing HKL_PC concentration. Results prove that hydroxypropylation with PC is a feasible method for lignin-based PU synthesis and reveals the potential of this approach as an alternative for the PO-based method.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bisneto2022,

title = {Effects of Functionalized Kraft Lignin Incorporation on Polypropylene Surface Energy and Practical Adhesion},

author = {Manuel Patricio da Silva Bisneto and Julia Rocha Gouveia and Leonardo Dalseno Antonino and Lara Basílio Tavares and Nathalie Minako Ito and Demetrio Jackson dos Santos},

url = {https://www.mdpi.com/2073-4360/14/5/999},

doi = {10.3390/polym14050999},

issn = {2073-4360},

year  = {2022},

date = {2022-03-00},

urldate = {2022-03-00},

journal = {Polymers},

volume = {14},

number = {5},

publisher = {MDPI AG},

abstract = {Polypropylene (PP) is a multifunctional and widely applied polymer. Nevertheless, its low energy surface and poor adhesion are well-known and might impair some prospective applications. Aiming to overcome these limitations, PP composites can be applied as a tool to enhance PP surface energy and then increase its practical adhesion. In this work, Kraft lignin (KL) was chemically modified and blended with PP. In short, KL was hydroxypropylated and further reacted with acetic anhydride (A-oxi-KL) or maleic anhydride (M-oxi-KL). Lignin modifications were confirmed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). PP-composites with different lignin contents, as well as pristine PP, were characterized in terms of their thermal behavior, morphology, surface energy, and practical adhesion by DSC, scanning electron microscopy (SEM), contact angle measurement, and peeling tests, respectively. Lignin incorporation did not affect the PP degree of crystallization. The lignin modifications led to a better compatibility with the PP matrix and surface energies up to 86% higher than neat PP. Increases of up to 66% in the peel strength were verified. Composites with M-oxi-KL showed the best adhesion performance, confirming the lignin functionalization is an efficient approach to improve the practical adhesion of PP films.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Antonino2021b,

title = {Effects of core–shell and reactive liquid rubbers incorporation on practical adhesion and fracture energy of epoxy adhesives},

author = {Leonardo Dalseno Antonino and Guilherme Elias Saltarelli Garcia and Camila de Oliveira Viani and Júlia Rocha Gouveia and Suel Eric Vidotti and Demetrio Jackson dos Santos},

url = {https://link.springer.com/article/10.1007/s13726-021-00976-z},

doi = {10.1007/s13726-021-00976-z},

issn = {1735-5265},

year  = {2021},

date = {2021-12-00},

urldate = {2021-12-00},

journal = {Iran Polym J},

volume = {30},

number = {12},

pages = {1329--1338},

publisher = {Springer Science and Business Media LLC},

abstract = {Epoxies offer many advantages in structural applications compared with other adhesives. However, their highly cross-linked structure leads to brittle materials, with low toughness and poor impact resistance. Usually, core–shell and reactive liquid rubbers are incorporated into industrial epoxy adhesives to overcome these limitations. Although important studies have been published in this field, it still lacks in the literature a comprehensive comparison between the effects of incorporating each type of rubber into the same epoxy matrix. Additionally, these reports usually focus on the behavior of the adhesive bulk, neglecting the effect of tougheners inclusion on the adhesively bonded joints fracture energy. Aiming to fill this gap, in this work, we prepared epoxy adhesives reinforced with core–shell rubber particles (CSR) or with a reactive liquid rubber (carboxyl-terminated polybutadiene-co-acrylonitrile—CTBN), at constant rubber contents in both formulations. Then, the toughened adhesives were investigated with respect to their thermomechanical behavior, as well as their adhesion performance. Bulk properties were characterized by uniaxial tensile tests and dynamic mechanical analysis, while the practical adhesion was investigated with single-lap shear and peeling tests. Finally, we assessed the adhesively bonded joints fracture energy in a customized experiment. The results showed that CTBN incorporation improved the adhesively bonded joints fracture energy by almost 816%, while CSR increased it by 550%. However, CTBN decreased the Tg of epoxy adhesives from 160 up to 130 °C, while CSR incorporation revealed no significant influence on Tg. Practical adhesion was increased by incorporation of both tougheners. In short, CTBN-containing samples revealed to be more efficient, even in smaller concentrations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gouveia2020,

title = {Kraft lignin-containing polyurethane adhesives: the role of hydroxypropylation on thermomechanical properties},

author = {Júlia R. Gouveia and Leonardo D. Antonino and Guilherme E. S. Garcia and Lara Basílio Tavares and Amanda N. B. Santos and Demetrio Jackson dos Santos},

url = {https://www.tandfonline.com/doi/abs/10.1080/00218464.2020.1784148},

doi = {10.1080/00218464.2020.1784148},

issn = {1545-5823},

year  = {2021},

date = {2021-11-18},

urldate = {2021-11-18},

journal = {The Journal of Adhesion},

volume = {97},

number = {15},

pages = {1423--1439},

publisher = {Informa UK Limited},

abstract = {During the last years, several efforts were dedicated to the development of lignin-based polyurethane adhesives, in which phase separation and brittleness were the most significant reported limitations. Hydroxypropylation emerged as a feasible method to overcome their restricted performance, since this method generates lignin with higher reactivity and branched molecular structure, at different extends. However, the effect of lignin hydroxypropylation on properties of lignin-based PU adhesives remains unclear. In this work, mixtures of lignins and castor oil were used as renewable raw material polyol in the PU synthesis. First, a pristine kraft lignin (KL) was used as reference, followed by incorporation of two hydroxypropylated lignins: highT_HPL – obtained under high temperature and pressure (150°C, 18 bar) and lowT_HPL – synthesized under milder conditions (40°C, atm). Temperature modulated optical refractometry (TMOR) revealed a slower curing process for than highT_HPL-containing PU. LowT_HPL lignin improved the PU modulus of elasticity and ultimate tensile stress. KL and lowT_HPL incorporation resulted in higher strength of wooden adhesively bonded joints (single lap shear tests – 4.5 MPa). The results elucidated the main effects of hydropropylation on PU and its application on adhesively bonded joints, supporting the development of further lignin-based adhesives.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Santos2021b,

title = {Microencapsulation of reactive isocyanates for application in self-healing materials: a review},

author = {Amanda N. B. Santos and Demetrio Jackson dos Santos and Danilo J. Carastan},

url = {https://www.tandfonline.com/doi/abs/10.1080/02652048.2021.1921068},

doi = {10.1080/02652048.2021.1921068},

issn = {1464-5246},

year  = {2021},

date = {2021-07-04},

urldate = {2021-07-04},

journal = {Journal of Microencapsulation},

volume = {38},

number = {5},

pages = {338--356},

publisher = {Informa UK Limited},

abstract = {Microencapsulation of curing agents is a major strategy for the development of self-healing polymers. Isocyanates are among the most promising compounds for the development of one-part, catalyst free, self-healing materials, but their microencapsulation is challenging due to their high reactivity. To keep the healing agent intact in the liquid state and containing free-NCO groups, the monitoring of several synthesis parameters is essential. This review aims to summarise the outcomes in the microencapsulation of isocyanates, emphasising the efforts reported in the literature to modulate the microcapsule properties. In this regard, the main synthesis procedures are presented, followed by the most relevant characterisation methods used to assess microcapsule properties. The correlation between these properties and synthesis parameters is also discussed, and finally the main potential and challenges for industrial applications are highlighted.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Antonino2021,

title = {Reactivity of Aliphatic and Phenolic Hydroxyl Groups in Kraft Lignin towards 4,4′ MDI},

author = {Leonardo Dalseno Antonino and Júlia Rocha Gouveia and Rogério Ramos de Sousa Júnior and Guilherme Elias Saltarelli Garcia and Luara Carneiro Gobbo and Lara Basílio Tavares and Demetrio Jackson dos Santos},

url = {https://www.mdpi.com/1420-3049/26/8/2131},

doi = {10.3390/molecules26082131},

issn = {1420-3049},

year  = {2021},

date = {2021-04-00},

urldate = {2021-04-00},

journal = {Molecules},

volume = {26},

number = {8},

publisher = {MDPI AG},

abstract = {Several efforts have been dedicated to the development of lignin-based polyurethanes (PU) in recent years. The low and heterogeneous reactivity of lignin hydroxyl groups towards diisocyanates, arising from their highly complex chemical structure, limits the application of this biopolymer in PU synthesis. Besides the well-known differences in the reactivity of aliphatic and aromatic hydroxyl groups, experimental work in which the reactivity of both types of hydroxyl, especially the aromatic ones present in syringyl (S-unit), guaiacyl (G-unit), and p-hydroxyphenyl (H-unit) building units are considered and compared, is still lacking in the literature. In this work, the hydroxyl reactivity of two kraft lignin grades towards 4,4′-diphenylmethane diisocyanate (MDI) was investigated. 31P NMR allowed the monitoring of the reactivity of each hydroxyl group in the lignin structure. FTIR spectra revealed the evolution of peaks related to hydroxyl consumption and urethane formation. These results might support new PU developments, including the use of unmodified lignin and the synthesis of MDI-functionalized biopolymers or prepolymers.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{dosSantos2021,

title = {Lignin-based polyurethane and epoxyadhesives: a short review},

author = {Demetrio Jackson dos Santos and L.B. Tavares and J.R. Gouveia and G.F. Batalha},

url = {https://archivesmse.org/resources/html/article/details?id=217749&language=en},

doi = {10.5604/01.3001.0015.0242},

issn = {1897-2764},

year  = {2021},

date = {2021-02-01},

urldate = {2021-02-01},

volume = {2},

number = {107},

pages = {56--63},

publisher = {Index Copernicus},

abstract = {Purpose: of this paper was to review and summarize significant papers related to the development and characterization of lignin-containing adhesives: polyurethane and epoxy types. In the last decades, several efforts have been dedicated on the development of renewable raw materials for polymer synthesis, mainly due to petroleum depletion and sustainability. In this context, lignin emerged as a potential candidate to substitute fossilbased raw materials in adhesive synthesis and formulations. Design/methodology/approach: Recent and other relevant papers were reviewed, aiming to identify the main advantages and limitations involved in lignin incorporation into epoxy and polyurethane adhesives formulations. First, effects of unmodified lignin addition were presented. Afterwards, the main lignin chemical modification methods were presented and discussed, based on thermomechanical results. Findings: Incorporation of unmodified lignin usually is limited to 30 %wt., otherwise mechanical properties are drastically affected as consequence of poor lignin solubility and excessive brittleness. Lignin chemical modification can be used to increase the reactivity of hydroxyl groups and/or add new moieties in its molecular structure, improving solubility and thermomechanical properties of cured adhesives. Practical implications: In the last years, some industrial plants started to operate and produce technical grade lignin at industrial scale, with reproducible properties and controlled molecular structure. Therefore, increasing efforts have been dedicated from researchers and chemists to develop lignin-based technologies, in which this work can directly contribute with. Originality/value: As consequence of the high content of phenol groups in its molecular structure, lignin was mostly applied on the development of phenolic resins applied as wood adhesives. For the first time in the literature, this work summarizes the advances related to synthesis and characterization of polyurethane and epoxy, applied as adhesives. Results can support the development and application of biobased, as well as contribute to the revalorization of this valuable and readily available biomass.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}