Self-poled piezoelectric polymer composites via melt-state energy implantation.

Lightweight flexible piezoelectric polymers are demanded for various applications. However, the low instinctively piezoelectric coefficient (i.e. d33) and complex poling process greatly resist their applications. Herein, we show that introducing dynamic pressure during fabrication is capable for poling polyvinylidene difluoride/barium titanate (PVDF/BTO) composites with d33 of ~51.20 pC/N at low density of ~0.64 g/cm3. The melt-state dynamic pressure driven energy implantation induces structure evolutions of both PVDF and BTO are demonstrated as reasons for self-poling. Then, the porous material is employed as pressure sensor with a high output of ~20.0 V and sensitivity of ~132.87 mV/kPa. Besides, the energy harvesting experiment suggests power density of ~58.7 mW/m2 can be achieved for 10 N pressure with a long-term durability. In summary, we not only provide a high performance lightweight, flexible piezoelectric polymer composite towards sustainable self-powered sensing and energy harvesting, but also pave an avenue for electrical-free fabrication of piezoelectric polymers.

Fabrication high toughness poly(butylene adipate-co-terephthalate)/thermoplastic starch composites via melt compounding with ethylene-methyl acrylate-glycidyl methacrylate.

The preparation of biodegradable composites with high toughness and low cost is of great significance for their application and promotion in the packaging field. As a renewable and biodegradable material with abundant sources, the inclusion of starch in biodegradable composites can significantly reduce costs. However, the poor compatibility between starch and matrix severely limits its large-scale practical application. In this work, the poly(butylene adipate-co-terephthalate)/thermoplastic starch/ethylene-methyl acrylate-glycidyl methacrylate (PBAT/TPS/EGMA) blends with high toughness were prepared by melt compounding. The elongation at break increased significantly from 533 ± 125 % for the PBAT/TPS(60/40) blend to 1188 ± 28 % for the PBAT/TPS/EGMA(60/40/2) blend. According to the analysis of Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope (SEM), the toughness improvement brought about by the addition of EGMA can be attributed to the enhanced compatibility between PBAT and TPS and the refinement of TPS particle size. The knowledge obtained from this study provides a method to enhance the toughness of biodegradable polymer composites with high TPS loading, which will facilitate the practical application of starch in the packing field.

Dual Reversible Network Nanoarchitectonics for Ultrafast Light-Controlled Healable and Tough Polydimethylsiloxane-Based Composite Elastomers.

It is highly desirable to develop polydimethylsiloxane (PDMS) elastomers with high self-healing efficiency and excellent mechanical properties. However, most self-healable materials reported to date still take several hours to self-heal and improving the self-healing property often comes at the expense of mechanical properties. Herein, a simple design strategy of dual reversible network nanoarchitectonics is reported for constructing ultrafast light-controlled healable (40 s) and tough (≈7.2 MJ m-3) PDMS-based composite elastomers. The rupture reconstruction of dynamic bonds and the reinforcement effect of carbon nanotubes (10 wt %) endowed our composite elastomer with excellent fracture toughness that originated from a good yield strength (≈1.1 MPa) and stretchability (≈882%). Moreover, carbon nanotubes can quickly and directly heat the damaged area of the composite to achieve its ultrafast repair with the assistance of dynamic polymer/filler interfacial interaction, greatly shortening the self-healing time (12 h). The self-healing performance is superior to that of reported self-healable PDMS-based materials. This novel strategy and the as-prepared supramolecular elastomer can inspire further various practical applications, such as remote anti-icing/deicing materials.

Fabrication of triboelectric polymer films via repeated rheological forging for ultrahigh surface charge density.

Triboelectric polymer with high charge density is the foundation to promote the wide range of applications of triboelectric nanogenerators. This work develops a method to produce triboelectric polymer based on repeated rheological forging. The fluorinated ethylene propylene film fabricated by repeated forging method not only has excellent mechanical properties and good transmittance, but also can maintain an ultrahigh tribo-charge density. Based on the film with a thickness of 30 µm, the output charge density from contact-separation nanogenerator reaches 352 µC·m-2. Then, the same film is applied for the nanogenerator with air-breakdown mode and a charge density of 510 µC·m-2 is further achieved. The repeated forging method can effectively regulate the composition of surface functional groups, the crystallinity, and the dielectric constants of the fluorinated ethylene propylene, leading to the superior capability of triboelectrification. Finally, we summarize the key parameters for elevating the electrification performance on the basis of molecular structure and related fabrication crafts, which can guide the further development of triboelectric polymers.

Enhancing Electrostrictive Actuation via Strong Electrostatic Repulsion among Field-Induced Nanodomains in a Relaxor Ferroelectric Poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) Random Terpolymer.

Electrostrictive polymers having a large strain are desirable for actuation, sensing, and energy harvesting in wearable electronics and soft robotics. However, a high electric field (>100 MV/m) is usually required for current electrostrictive polymers. To realize large electrostriction at reduced electric fields, the fundamental electrostriction mechanism needs to be better understood. In response to this need, the structure and electrostrictive properties of relaxor ferroelectric (RFE) poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] random terpolymers films with different thermal annealing histories were studied in this work. First, the semicrystalline structure of the P(VDF-TrFE-CTFE) terpolymer films was studied by combined small-angle X-ray scattering and wide-angle X-ray diffraction analyses. A three-phase model was employed, namely, crystals and oriented and isotropic amorphous fractions (OAF and IAF). The bulky CTFE units generated taut-tie molecules (TTM) in the crystalline lamella, dividing it into many nanosized crystals (∼1.3 nm thick). It is this unique crystalline structure with nanocrystals and mobile TTM/OAF that enabled the RFE behavior for the P(VDF-TrFE)-based terpolymers. Through electrostriction measurements and nonlinear dielectric analysis, an inverse correlation was observed between the ferroelectric nonlinearity and the electrostrictive coefficient under a high poling electric field (>100 MV/m). This suggested that higher electrostriction performance could be achieved by decreasing the ferroelectric nonlinearity of the RFE terpolymer. Indeed, above the Curie temperature, the paraelectric terpolymer films achieved a high electrostrictive performance with the transverse strain being ∼5% at 200 MV/m. This was attributed to the strong electrostatic repulsion among electric field-induced ferroelectric nanodomains. The finding from this work provides a viable way to design new electrostrictive polymers with higher performance at low driving fields.

Effect of Different Compatibilizers on the Properties of Poly (Lactic Acid)/Poly (Butylene Adipate-Co-Terephthalate) Blends Prepared under Intense Shear Flow Field.

In this report, poly(lactic acid) (PLA) and Poly(butylene adipate-co-terephthalate) (PBAT) with three kinds of compatibilizers were melt blended under intensive shear flow. A self-made parallel three-screw extruder was developed to generate such flow during the process. Mechanical properties, chemical reactions among PLA, PBAT and compatibilizers, rheological behavior and morphology were investigated. The mechanical tests showed that the notched impact strength of super-tough composite with 10 wt% EGMA is about 20 times than that of pure PLA. The Fourier transform infrared spectroscopy (FT-IR) results showed that the epoxy functional groups or maleic anhydride functional groups of KT-20, KT-915 and EGMA reacted with the hydroxyl groups of PLA or PBAT macromolecules, resulting in a bridge of PLA and PBAT. About rheological properties, the tan δ-angular frequency curves and the η''- η' curves confirmed the chemical reactions mentioned above and indicated better compatibility of η''- η' between PLA and PBAT, respectively. Meanwhile, the loss modulus and storage modulus-angular frequency curves demonstrated the discrepancy of different compatibilizer components. In particular, from scanning electron microscopy (SEM) images, it can be seen that the phase size and dispersion uniformity of PBAT adjusted by compatibilizer, corresponding to better compatibility that is described in the η''- η' curves. The approach for producing super-tough PLA/PBAT/compatibilizer by intensive shear flow provides a viable direction for further improving PLA performance.

Improved Properties of Metallocene Polyethylene/Poly(ethylene terephthalate) Blends Processed by an Innovative Eccentric Rotor Extruder.

* Correspondence: pmhzhe@scut [...].

Blends of rABS and SEBS: Influence of In-Situ Compatibilization on the Mechanical Properties.

In this study, the in-situ compatibilization reaction between recycled acrylonitrile-butadiene-styrene copolymer (rABS) and functional styrene-ethylene-butylene-styrene block maleic anhydride (SEBS-g-MAH) was confirmed, which contributed to the toughening phenomenon of rABS, especially the notched impact strength. As mechanical test that manifested, the rABS/SEBS-g-MAH blends are stronger and more ductile than the rABS/SEBS blends. Prominently, the former has great advantage over the latter in terms of improving the impact performance. Scanning electron microscope (SEM) images showed that the compatible segments that were generated by reaction not only improve the interface adhesion of rABS/SEBS-g-MAH blends but also promote the evolution of co-continuous structures, which can be evidently observed after etching. Furthermore, the SEM micrographs of tensile fracture surfaces indicated that the formation of the co-continuous phase and the improvement of interface adhesion are the most profound reasons for the excellent tensile properties of the rABS/SEBS-g-MAH blends. The impact fracture surface revealed that two-phase interface affects crack propagation and shear yielding absorbs more impact energy than simple interface debonding does at higher deformation rates. Meanwhile, rheological analysis demonstrated that the complex viscosity of the rABS/SEBS-g-MAH (80/20 wt%) blend with a co-continuous structure exhibits a maximum positive deviation at low frequencies from the theoretical value calculated using the rule of logarithmic sum, which indicated a connection between co-continuous structure and complex viscosity. In addition, the storage modulus vs. loss modulus curves of the blends revealed that the viscoelastic behavior of rABS/SEBS-g-MAH blends is very similar to that of rABS.

Morphology, Thermal, Mechanical Properties and Rheological Behavior of Biodegradable Poly(butylene succinate)/poly(lactic acid) In-Situ Submicrofibrillar Composites.

In this study, biodegradable poly(butylene succinate)/poly(lactic acid) (PBS/PLA) in-situ submicrofibrillar composites with various PLA content were successfully produced by a triple-screw extruder followed by a hot stretching-cold drawing-compression molding process. This study aimed to investigate the effects of dispersed PLA submicro-fibrils on the thermal, mechanical and rheological properties of PBS/PLA composites. Morphological observations demonstrated that the PLA phases are fibrillated to submicro-fibrils in the PBS/PLA composites, and all the PLA submicro-fibrils produced seem to have a uniform diameter of about 200nm. As rheological measurements revealed, at low frequencies, the storage modulus (G') of PBS/PLA composites has been increased by more than four orders of magnitude with the inclusion of high concentrations (15 wt % and 20 wt %) of PLA submicro-fibrils, which indicates a significant improvement in the elastic responses of PBS melt. Dynamic Mechanical Analysis (DMA) results showed that the glass transition temperature (Tg) of PBS phase slightly shifted to the higher temperature after the inclusion of PLA. DSC experiments proved that fiber morphology of PLA has obvious heterogeneous nucleation effect on the crystallization of PBS. The tensile properties of the PBS/PLA in-situ submicrofibrillar composites are also improved compared to neat PBS.

Preparation and Characteristics of Biocomposites Based on Steam Exploded Sisal Fiber Modified with Amphipathic Epoxidized Soybean Oil Resin.

Sisal fiber was pretreated by continuous screw extrusion steam explosion to prepare steam exploded sisal fiber (SESF) preforms. An amphipathic bio-based thermosetting resin with poor mechanical properties was cured by epoxidized soybean oil (ESO) and citric acid (CA). The obtained resin was used to modify SESF preforms and prepare eco-friendly biocomposites. The molar ratios (R) of carboxylic groups to epoxy groups and resin contents in biocomposites were adjusted. The biocomposites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transfer infrared spectroscopy (FT-IR), tensile testing, scanning electron microscopy (SEM), water absorption and water contact angle measurements. The maximum thermal decomposition temperature of the biocomposites was 373.1 °C. The curing efficiency of the resin in the biocomposites improved with the increase of resin content, and reached a maximum at R = 1.2. The tensile strength of the biocomposites reached a maximum of 30.4 MPa at R = 1.2 and 40% resin content. SEM images showed excellent interfacial bonding and fracture mechanisms within the biocomposites. The biocomposites exhibited satisfactory water resistance. ESO resin cured with polybasic carboxylic acid is therefore a good bio-based modifier for lignocellulose, that prepare biocomposites with good mechanical properties, hydrophobicity, and thermostability, and which has a potential application in packaging.

Environmentally-Friendly Extraction of Cellulose Nanofibers from Steam-Explosion Pretreated Sugar Beet Pulp.

Cellulose nanofibers (CNFs) with an average diameter of 22 nm were prepared from sugar beet pulp (SBP) via an environmentally-friendly method. Steam-explosion pretreated SBP was treated with hydrogen peroxide (H2O2) bleaching, high-speed blending, and ultrasonic treatment. Thermogravimetric analysis showed that hemicellulose was partially hydrolyzed in the steam-cooking stage, pectin was removed in the explosion stage, and lignin was removed by H2O2 bleaching. The removal of non-cellulosic components was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. Morphological analysis showed that steam-explosion pretreatment largely extracted the binder materials of hemicellulose and pectin. This exposed the microfibrillated cellulosic fibers, which promoted subsequent nanofibrillation. X-ray diffraction showed that the CNFs had a crystallinity index of 62.3%. The CNFs had good thermal stability, and thus have potential for use as fillers in polymer matrices. The only chemical reagent used in this green method was H2O2. Combining H2O2 bleaching with steam explosion, high-speed blending, and ultrasonic treatment reduced the overall energy consumption and increased the efficiency of the CNFs extraction. The method, therefore, has potential application in industrial processes.

Synthesis of a bioadsorbent from jute cellulose, and application for aqueous Cd (II) removal.

A low-cost, high-adsorption-capacity, eco-friendly bioadsorbent for removing Cd2+ from aqueous solution is reported. J-g-P(AM-co-AANa) was prepared by hydrolysis of the grafted copolymer, which was synthesized by free radical polymerization of acrylamide (AM) with jute fibers (JSE) pretreated by continuous screw-extrusion steam explosion. Fourier transform infrared and solid-state 13C nuclear magnetic resonance spectroscopies, confirmed that amino and carboxylate groups were introduced into J-g-P(AM-co-AANa). X-ray diffraction showed that the crystallinity of J-g-P(AM-co-AANa) was significantly lower than that of JSE. The surface morphology of bioadsorbent was investigated by scanning electron microscopy (SEM). The adsorption capacity of Cd2+ on J-g-P(AM-co-AANa) was evaluated for different solution pH values, contact times, and initial Cd2+ concentrations. The adsorption kinetics followed the pseudo-second-order kinetic model, and the rate controlling step was chemisorption. The adsorption isotherm was well fitted by the Freundlich model, and the adsorption process was multilayer adsorption. The maximum adsorption capacity was 344.8 mg/g, which indicated that the bioadsorbent was effective for removing Cd2+ from aqueous solution.

A Facile Fabrication of High Toughness Poly(lactic Acid) via Reactive Extrusion with Poly(butylene Succinate) and Ethylene-Methyl Acrylate-Glycidyl Methacrylate.

As is an excellent bio-based polymer material, poly(lactic acid) (PLA)'s brittle nature greatly restricts its extensive applications. Herein, poly(butylene succinate) (PBS) was introduced to toughening PLA by melt blending using a self-made triple screw extruder through in situ reactive with ethylene-methyl acrylate-glycidyl methacrylate (EGMA). The effect of EGMA concentrations on the mechanical properties, morphology, interfacial compatibility of PLA/PBS blends were studied. Fourier transform infrared (FT-IR) results demonstrated that the epoxy group of EGMA reacts with the hydroxyl groups of PLA and PBS, which proved the occurrence of interfacial reactions among the tri-component. The significantly improved compatibility between PLA and PBS after EGMA incorporation was made evident by scanning electron microscope (SEM) characterization results. Meanwhile, the contact angle test predicted that the EGMA was selectively localized at the interface between PLA and PBS, and the result was verified by morphological analysis of cryofracture and etched samples. The EGMA improves the compatibility of PLA/PBS blends, and consequently leads to a significantly increased toughness with the elongation at break occurring 83 times more when 10 wt % EGMA was introduced than neat PLA, while impact strength also enhanced by twentyfold. Ultimately, the toughening mechanism of PLA based polymers was established based on the above analysis, exploring a new way for the extensive application for degradable material.