This study investigates the use of tobacco extract residue (TER), an extraction byproduct, as a filler in poly(butylene adipate-co-terephthalate) (PBAT) composites. Composites containing 10, 20 and 40 wt% TER were prepared and systematically tested and characterized. Experimental results showed that increasing TER levels enhanced stiffness and crystallinity degree of the composites. However, the tensile strength and elongation at break were both decreased. These mechanical reductions were related to an insufficient interfacial adhesion between two components. Additionally, the higher TER contents also enhanced hydrophilicity and diffusion coefficients, leading to the increase of water absorption. To remedy these drawbacks, gallic acid (GA) was introduced as a compatibilizer at content ranging from 1 to 10 wt%. Its hydroxyl and carboxyl groups could create hydrogen bonding and possible covalent interactions with both PBAT and TER, as suggested by FTIR analysis. Microscopic observations revealed improved interfacial adhesion at all GA contents. GA acts as a bio-based interfacial modifier, offering a more sustainable alternative to conventional compatibilizers. Thermogravimetric analysis indicated that all compatibilized compositions enhanced thermal stability compared to the composite without compatibilizer. Based on the experimental results, the composites containing 40 wt% TER and 1 wt% GA exhibited the balanced stiffness, toughness and thermal stability and raw materials cost reduction that potentially approached for applying in biodegradable agricultural applications.

The purpose of this study is to develop green composites prepared from bio-derived polybenzoxazine (PBz) and glass fiber (GF). The effects of GF contents (22.7, 30.6, 39.8, 50.7, and 63.8 vol%) on mechanical, thermal and surface properties, self-healing behavior and UV-protection property were evaluated. Flexural properties, thermal stability and flame resistant of the composite samples was substantially improved by the presence of GFs, while the thermal expansion and water contact angle was progressively reduced with the GF content. The self-healing efficiency assessed through self-healing percentage under flexure content confirm that the composite samples showed good self-healing performance with the self-healing percentage within 59.5-83.8. In addition, reinforcing GF also exhibits an enhanced ultraviolet shielding efficiency of the composite samples closed to 100%. Based on the composite's mechanical and thermal properties, self-healing efficiency, flame resistant and UV-protection property, its potential usage is suggested in advanced application such as structural materials with associated requirements of significant self-healing, self-extinguishing and ultraviolet-shielding property.Highlights Green GF/bio-derived polybenzoxazine composites was successfully developed. The GF/poly(E-fa) composite showed substantial self-healing performance. LOI values of the composite were suitable for self-extinguishing materials. The reinforcement with GF into composites improved comprehensive properties. The composite represents a promising new candidate for structural materials.

A new type of glass fiber (GF)-reinforced bio-derived polybenzoxazine (GF/bio-derived PBz) composites suitable for dental post applications was developed. The study assessed the effects of different quantities of GF on the mechanical and thermal characteristics, thermal stability, and flame resistance of the composite samples. Additionally, the feasibility of using GF/bio-derived PBz composites for dental posts was analyzed through finite element analysis (FEA). The stress distribution in a tooth model repaired with the newly developed GF/bio-derived PBz composite posts under oblique loads was compared to models repaired with conventional glass fiber post and gold alloy post. The incorporation of GFs significantly enhanced the flexural properties, thermal stability, and flame resistance of the composite samples, while also reducing thermal expansion in a manner that closely matched that of dentin. The FEA of a tooth model repaired with a composite post derived from GF/bio-based PBz revealed a stress distribution pattern comparable to that of a tooth model repaired using a conventional glass fiber post. Considering the composite’s mechanical properties, thermal stability, flame resistance, and its suitability for dental fiber posts as demonstrated by the FEA, the GF/bio-derived PBz holds significant promise for use in dental fiber post applications.

Novel sustainable self-healing polymer composites were developed from glass fabric reinforced copolymers of eugenol/furfurylamine-derived benzoxazine resin (E-fa) and epoxidized castor oil (ECO) actuated by nearinfrared (NIR) light. This research demonstrates self-healing processes triggered by NIR affected by glass fabric incorporation as well as investigates essential properties for structural skin applications in sustainable composites. Through the measurement, the reinforced glass fabrics substantially improved flexural properties, enhanced thermal stability and UV light protection of the composites. The healing mechanism and performance of the developed E-fa/ECO composites were also systematically studied. The time for damaged healing of the material triggered by heating from NIR light was found in the range of 80-152 s with the good macroscopic healing performance up to 64-86%. The results suggested that the glass fabric reinforced sustainable benzoxazine/epoxy composites possessing NIR-induced self-healing effect have a potential use in building lath applications.

A novel dental fiber post from glass fiber-reinforced polybenzoxazine (PBZ) composites was developed in this work. The essential properties, that is, chemical characteristics, thermal and biological properties of the PBZ composites were investigated for various glass fiber loadings (10.5, 23.7, 41.2 and 65.1 vol%). Finite element analysis (FEA) was also utilized to observe mechanical behaviors of the tooth model repaired with PBZ composite posts compared to a natural tooth model. The findings reveal that for the fiber-reinforced PBZ composites not only their thermal properties were significantly improved, but they also showed enhanced cytocompatibility; we found a coefficient of thermal expansion of 12.8 ppm/degrees C and cell viability of 91.55 for the 65.1 vol% glass fiber-reinforced PBZ composite. Moreover, samples reinforced with higher glass fiber loadings effectively resulted in the reduction of stress distribution in dentin observed from FEA suggesting protection againt root fractures. Restoration using the PBZ composite post showed the same stress patterns in the dentin-composite resin-post interface of the repaired tooth as in the natural tooth model. The results revealed that the glass fiber-reinforced PBZ composites possess good thermal properties and mechanical behaviors which renders them suitable candidates for biocompatible dental materials.Highlights The glass fiber/polybenzoxazine (GF/PBZ) composites had nontoxic properties as evidenced through cell viability, growth and morphology studies. The thermal expansion of the GF/PBZ composite was similar to that of dentin, promoting adaptation at the dentin-post interface. Mechanical behaviors evaluated by FEA of tooth model restored with GF/PBZ composite post were similar to those restored with commercial glass fiber post. The biocompatible GF/PBZ composite with good thermal and mechanical properties is a promising new candidate material as dental fiber post. Effect of glass fiber reinforcement on biological and thermal properties, mechanical behaviors and chemical characteristics of the PBZ composites for use as a dental fiber post. image

Shape memory polymers are advanced materials that find diverse applications in soft robotic grippers, aerospace structures, and medical devices. This study focuses on developing fast magnetic-responsive shape memory composites using bio-based benzoxazine /polyglycerol polyglycidyl ether copolymers filled with high-content iron oxide nanoparticles (Fe3O4 NPs). We investigated how varying Fe3O4 NP content influenced composite properties. Results indicated improved saturation magnetization, mechanical strength, and thermal stability with increasing Fe3O4 NP content (5-45 wt%). Activation of the composites' recovery process via an alternating magnetic field consistently achieved high shape recovery ratios (96-99 %). As Fe3O4 NP content increased, recovery time decreased from 14 to 3 s due to enhanced heat generation, accelerating shape restoration by reaching the glass transition temperature faster. Furthermore, we demonstrated their utility in a four-arm gripper, highlighting their potential in soft robotics. In conclusion, these shape memory composites exhibit rapid magnetic-responsive properties, promising significant applications in soft robotics.

This work emphasized on development of a novel bio-derived self-healing copolymer fabricated from benzoxazine and epoxy resins by varying weight ratios. The bio-derived benzoxazine (E-fa) acted as a healing agent was copolymerized with bio-derived epoxy resin namely epoxidized castor oil (ECO). Three main essential properties of the developed copolymer were systematically investigated: thermal property, mechanical property, and self-healing capacity. The numerical simulation was also used to study and predict the ability of roof coatings based on the developed copolymers. The results showed that the reversible crosslinking reaction occurred and resulted in state transition of the copolymers. The mechanical property i.e., tensile strength and peel strength to stainless steel substrate, were substantially improved with the incorporation of ECO. The increase in E-fa contents can enhance the thermos-responsive healing performance of the copolymers up to 93% via reversible reactions with rapid surface damage healed within 2 min. Furthermore, the experimental and numerical results revealed that the thermo-responsive thermoset self-healing bio-derived benzoxazine/epoxy copolymers have a potential use in coating applications required fast self-healing performance and good mechanical properties.

Non-asbestos and non-copper polybenzoxazine friction composites were developed with varying mass ratios of synthetic graphite (SG)/carbonized hemp hurd (CHH). Mechanical, thermal, and tribological properties of the polybenzoxazine friction composites were studied. The wear simulation of the polybenzoxazine friction composites has been performed with commercial ANSYS finite element analysis software. The strength and modulus under flexure mode, glass transition temperature of the polybenzoxazine friction composite samples were observed to be improved with increasing CHH content. It appears that the incorporation of the CHH into the polybenzoxazine friction composites not only enhanced the coefficient of friction (COF) but also improved the overall wear resistance of the units. The wear resistance and wear pattern obtained by the wear simulation also showed a good correlation with the experimental results. Based on the findings in this study, it is evident that the carbonized hemp hurd possesses a great potential to be used in green brake pad application.

Biocopolymers based on vanillin/fufurylamine–biobenzoxazine (V-fa) and epoxide castor oil (ECO), a bioepoxy, were prepared for application as dental fiber-reinforced composite post. The mechanical and thermal properties of the V-fa/ECO biocopolymers were assessed with regard to the influence of ECO content. The addition of the ECO at an amount of 20% by weight into the poly(V-fa) preserved the stiffness, glass transition temperature and thermal stability nearly to the poly(V-fa). Differential scanning calorimetry (DSC) was used to examine the curing kinetics of the V-fa/ECO monomer system with different heating rates. To determine the activation energy ( E a ), the experimental data were subjected to the isoconversional methods, namely Flynn–Wall–Ozawa (FWO) and Friedman (FR). The V-fa/ECO monomer mixture showed average E a values of 105 kJ/mol and 94 kJ/mol. The results derived using the curing reaction model and the experimental data were in good agreement, demonstrating the efficacy of the FWO method for determining the curing kinetics parameters. The simulated mechanical response to external applied loads by finite-element analysis of the tooth model restored with glass fiber-reinforced V-fa/ECO biocopolymer post showed a similar stress field to the tooth model restored with a commercial glass fiber post. Therefore, based on the findings in this work, it is evident that the bio-based benzoxazine/epoxy copolymer possesses a great potential to be used for dental fiber post. Graphical Abstract

The objective of this research is to study mechanical and thermal properties of polybenzoxazine-based friction materials (PFMs) filled with 10 wt% bamboo charcoal particles (BC) containing residual lignocellulose content of 0-10wt% (BC0-10%), 10-20wt% (BC10-20%) and 20-30wt% (BC20-30%). The PFMs filled with synthetic graphite particles was also prepared to compare the properties. The obtained results showed that the mechanical properties, i.e., flexural strength and flexural modulus of the PFMs were improved with an increase of the residual lignocellulose content, and tended to be higher than that of the PFMs filled with synthetic graphite particles. Thermal stability monitored by the degradation temperature at 5% weight loss (T d5 ) of the PFMs revealed a decrease with an increasing residual lignocellulose content in BC. However, the T d5 of the PFMs filled with BC is still higher than the generated heat during the braking, which has temperatures around 350 °C. The results suggested that the obtained composite material is a promising candidate for car brake pads.

Shape-memory carbon fiber (CF) polymer composites reinforced with graphene nanoplatelets (GnPs) as a filler based on a bio-based V-fa/ECO copolymer were prepared at different graphene GnPs and CF mass fractions using the hand lay-up and hot-pressing methods. The obtained composite specimens were subjected to flexural, dynamic mechanical, and shape-memory analyses. The obtained results revealed that the flexural strength and modulus were improved by the addition of the GnPs and CF due to the improvement in the interfacial adhesion and fiber reinforcement with up to 3 wt.% GnPs and 60 wt.% CF. Additionally, appreciable improvements in the shape-memory performance were achieved with the addition of the GnPs, where values of up to 93% and 96% were recorded for the shape fixity and recovery, respectively. The shape-memory performance was affected by the fiber mass fraction, with the composites retaining the shape-memory effect albeit with a significant drop in performance at higher fiber mass fractions. Lastly, the specimens at 40 wt.% CF and 3 wt.% GnPs were determined to be the optimum compositions for the best performance of the bio-based SMP composite.

A novel two-way shape memory polymers derived from benzoxazine/urethane alloys (poly(BA-a/PU)) are developed in this research. The effect of urethane contents acted as spring elastomer on dynamic mechanical properties and two-way shape memory performance of the alloys was investigated. The experimental test and numerical simulation were also used to study and predict the ability of the developed 2WSMPs. The results showed that shape fixity at room temperature (RT) of poly(BA-a/PU) was enhanced in the range of 80–97% with the addition of PU contents. Shape recovery values to first temporary shape at Tg+20 °C of the specimen were 79–93%, whereas, those to second temporary shape at RT were 82–95%. Furthermore, 2WSMP based on poly(BA-a/PU) was reversely recovered between both temporary shapes more than 7 cycles. The experimental and numerical results revealed that poly(BA-a/PU) exhibited high 2WSMP performance for using as smart materials in self-folding structures application.

A novel material based on silicone rubber (SR) modified with natural rubber (NR) was developed. Combinations of sulfur/peroxide curing systems were used as crosslinking agents. The results showed that the incorporation of NR improved the tensile strength, tear strength and elongation at break of the SR/NR blend. It was also found that the blending of SR/NR at 90/10 provided the greatest tensile strength and elongation at break of 1.9 MPa and 1381%, respectively as well as good tear strength. The properties of this SR/NR blend and the corresponding interpenetrating polymer network (IPN) were compared and showed that the IPN provided higher tensile strength. However, the blend exhibited greater elongation at break and hardness, relatively close to human skin which are more important for a birthing model material. It can be concluded that the blending of SR/NR at 90/10 is the most promising material to substitute expensive currently used birthing model.

Shape memory polymers (SMPs) are a class of smart materials that can be programmed to recover from temporary shape to permanent shape by applying external stimuli (temperature, magnetic field, light, electric field, and moisture, etc.). This unique property of SMPs makes them an appealing candidate in application for soft robotics, such as smart actuators, artificial muscles, and biomedical devices. In this contribution, we have developed multi-stimuli-responsive SMPs from bio-based benzoxazine resin and iron oxide nanoparticles (Fe3O4 NPs) that could be actuated by magnetic field and light. The nanocomposites were characterized by infrared spectroscopy, in which molecular interaction between benzoxazine/epoxy copolymers and Fe3O4 NPs was observed. Effects of nanoparticle content (0-5 wt%) on magnetic, mechanical, thermal, and thermo-mechanical properties of nanocomposites were investigated. Shape memory performance of nanocomposites was significantly improved with incorporation of Fe3O4 NPs. Shape fixity increased from 85% of neat copolymers to 93% of copolymers filled with 3 wt% Fe3O4 NPs, while shape recovery increased from 94% to 98%. Moreover, shape fixity could be done without external force contact by 808 nm-light actuation and magnetic attraction, due to photothermal and magnetic properties of nanocomposites. Shape recovery was tested under actuation by magnetic field. The highest shape recovery ratio was 99% within 26 s for copolymers filled with 5 wt% Fe3O4 NPs. Lastly, preliminary application of nanocomposites was demonstrated as they could push a 1 g-object within 10 s of actuation by magnetic field. In overall, these nanocomposites with multi-stimuli-responsive shape memory property had a good potential to be applied for soft robotics. (c) 2023 Kingfa Scientific and Technological Co. Ltd. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

This work aims to develop a novel composite post based on bio-based polybenzoxazine reinforced with glass fiber. The bio-based polybenzoxazine (poly(V-fa)) derived from vanillin, furfurylamine and paraformaldehyde, was prepared as polymer matrix in this study. Mechanical property and thermal property influenced by glass fiber contents were evaluated. The numerical simulation was also used to study the response to external applied load of tooth restored with glass fiber-reinforced poly(V-fa) composite posts by finite element analysis. From the results, not only the flexural properties, i.e. flexural strength and flexural modulus, were substantially improved up to 460 MPa and 25.6 GPa, respectively, but thermal properties, i.e. glass transition temperature (T g ) and degradation temperature at 5wt% loss (T d5 ), of the composites were also enhanced with the reinforcement of glass fiber contents. Furthermore, the restoration of the developed glass fiber-reinforced poly(V-fa) composite post in term of the maximum von Mises stress and deformation areas was predicted via ANSYS program. The experimental and numerical results revealed that the bio-based polybenzoxazine composite reinforced with glass fiber have highly potential to be used as composite posts.

Graft copolymers, deproteinized natural rubber-graft-polystyrene (DPNR-g-PS) and deproteinized natural rubber-graft-polyacrylonitrile (DPNR-g-PAN), were prepared by the grafting of styrene (St) or acrylonitrile (AN) monomers onto DPNR latex via emulsion copolymerization. Then, ultrafine fully vulcanized powdered natural rubbers (UFPNRs) were produced by electron beam irradiation of the graft copolymers in the presence of di-trimethylolpropane tetra-acrylate (DTMPTA) as a crosslinking agent and, subsequently, a fast spray drying process. The effects of St or AN monomer contents and the radiation doses on the chemical structure, thermal stability, and physical properties of the graft copolymers and UFPNRs were investigated. The results showed that solvent resistance and grafting efficiency of DPNR-g-PS and DPNR-g-PAN were enhanced with increasing monomer content. SEM morphology of the UFPNRs showed separated and much less agglomerated particles with an average size about 6 μm. Therefore, it is possible that the developed UFPNRs grafted copolymers with good solvent resistance and rather high thermal stability can be used easily as toughening modifiers for polymers and their composites.

Glass fiber post based on the new polymeric material, polybenzoxazine, is prepared and the effects of glass fiber contents on mechanical and thermal properties are evaluated. The mechanical response to externally applied loads of tooth restored with glass fiber-reinforced polybenzoxazine composite posts is also simulated by finite element analysis of a tridimensional model and compared with the response to that of a natural tooth. The reinforcing of glass fiber can help improve the mechanical and thermal properties of the polybenzoxazine influenced by the interfacial adhesion between the glass fiber and polybenzoxazine matrix, except for the relatively high mechanical property of the glass fiber. The mechanical data, i.e., elastic modulus under flexure load or flexural modulus by three-point bending test of the glass fiber-reinforced polybenzoxazine composites are agreed with the elastic modulus of dentin and then used in the finite element model. The restoration using the glass fiber-reinforced polybenzoxazine composite post provided the maximum von Mises equivalent stress at the cervical third area of the endodontically treated tooth model as similarly observed in the natural tooth. In addition, the maximum von Mises equivalent stress of the tooth restored with the glass fiber-reinforced polybenzoxazine composite post is also quietly like that of the natural tooth. The finding of this work provided the essential properties of the glass fiber-reinforced polybenzoxazine composite for dental restorations and appliances.

In this paper, the effects of organic based stabilizers (OBS) are investigated and compared with traditional lead (Pb) and calcium zinc (CaZn) heat stabilizers regarding their processability, mechanical property, and thermal degradation behaviors in rigid PVC pipe applications. In addition, the effects of repeated processing cycles on the degree of gelation and the impact strength of the PVC/OBS, PVC/CaZn, and PVC/Pb are also examined. A repeated processing cycle of those three types of the heat stabilizers up to four cycles was found to increase the degree of gelation and proved no significant effect on the impact strength and heat resistance of the resulting PVC samples. The OBS showed a positive effect on preventing the autocatalytic-typed thermal degradation of the PVC samples. This leads to a longer retention time for the initial color change of the PVC/OBS compared to PVC/Pb or PVC/CaZn systems. This characteristic was related to a more uniform fusion behavior of the PVC/OBS, i.e., the lowest gelation speed and the longest fusion time. The non-isothermal kinetic parameter determined by the Kissinger and Flynn–Wall–Ozawa methods of the dehydrochlorination stage of the PVC/OBS was in satisfactory agreement and continued to compare with the PVC/Pb and PVC/CaZn systems. The results indicated that the OBS might decrease the dehydrochlorination rate of PVC, implying that PVC/OBS was more stable than PVC/Pb and PVC/CaZn systems.

Abstract This study explored the development of a robust asbestos-free brake pad composite material from benzoxazine resin, eucalyptus fibers and other constituents. Two different samples involving bleached and unbleached eucalyptus fibers reinforced polybenzoxazine composites were produced, denoted by BEFPC and UEFPC respectively. The effects of bleached and unbleached eucalyptus fibers reinforcement on the mechanical, thermal and tribological properties of the composite were investigated for the first time. The results obtained suggested that both the two composites possesses good flexural properties, great thermal stability, and high coefficient of friction (COF) at 5 wt% fiber reinforcement. The degradation temperature at 5% weight loss (Td5) for PBEC and PUBEC stood at 368 and 342 ℃ respectively, with both having residual weight of more than 68%. Storage modulus of 5.25 and 5.10 GPa, and glass transition temperature (Tg) of 219 and 237°C were recorded for the BEFPC and UEFPC respectively. Findings from the study of flexural strength of the BEFPC and UEFPC conducted reveals that the flexural strengths were as high as 54.5 and 51.3 MPa respectively. Furthermore, interesting results from the study on the tribology of the composites shows that the coefficient of friction (COF) is in the range of 0.2–0.7, and wear rates were lower than 3.5×10− 7 cm3/Nm as required by Thailand Industrial Standard (TIS: 97-2014). Therefore, this study presents eucalyptus fiber-reinforced polybenzoxazine brake pad composites (EFPBC) as a potential friction materials for the automobile industry.