A comprehensive review on surface modification,structure interface and bonding mechanism of plant cellulose fiber reinforced polymer based composites

Abstract

Plant cellulose fiber polymer composites are readily applied in wide range of applications due to ecological and economical alternative to traditional materials. The considerable amount of residues and organic wastes from agricultural process are still employed as lower energy resource. Organic materials are generally disposed in composting, landfilling or anaerobic digestion. The utilization of these wastes in plant fiber composites shows significant alternative and environmental friendly in nature. The production of plant cellulose fiber composite with higher structural properties is optimized by interfacial bonding between polymer and reinforced fiber. The interface plays a vital role in regulating mechanical properties by distributing bonds and stress transferring, which is one of least understood element of composites. This paper presents the comprehensive review of fiber structures, different modification techniques to reduce the incompatibility between matrix and fiber, assessment of structure interface and bonding, clarifies the interfacial adhesion of cellulose fiber composites.     

Search for a Steric Penultimate Effect: Copolymerization of 2,3,4-Trimethyl-3-pentyl Methacrylate with Styrene

The hindered monomer, 2,3,4-trimethyl-3-pentyl methacrylate (I), was synthesized for penultimate effect studies. Since it readily homopoiymerized (km¹¹¹≠ 0) and readily copolymerized with styrene, copolymerizations of I with styrene were carried out at 60°C in benzene with AIBN as initiator. The conversion to copolymer and the copolymer composition were determined by using GLC techniques. Composition-conversion data was analyzed by performing a computerized nonlinear least-squares fitting to the integrated form of the penultimate model equation. The experimental design included the use of optimized M¹°/M²° ratios. The penultimate reactivity ratios calculated from these data were r¹′ = 0.23, r¹′= 0.59, r² = 0.59, r²′ = 1.34. Thus, when I is the penultimate unit, a terminal styryl radical prefers to add styrene, whereas when styrene is the penultimate unit, terminal styryl radicals prefer to add I. These results constitute the best evidence for a steric penultimate effect yet available in the literature from composition-conversion studies. However, the case is not yet proved. Further studies to strengthen this conclusion are proposed.     

Selection of hydrogel electrolytes for flexible zinc–air batteries

Flexible zinc–air batteries attract more attention due to their high energy density, safety, environmental protection, and low cost. However, the traditional aqueous electrolyte has the disadvantages of leakage and water evaporation, which cannot meet application demand of flexible zinc–air batteries. Hydrogels possessing good conductivity and mechanical properties become a candidate as the electrolytes of flexible zinc–air batteries. In this work, advances in aspects of conductivity, mechanical toughness, environmental adaptability, and interfacial compatibility of hydrogel electrolytes for flexible zinc–air batteries are investigated. First, the additives to improve conductivity of hydrogel electrolytes are summarized. Second, the measures to enhance the mechanical properties of hydrogels are taken by way of structure optimization and composition modification. Third, the environmental adaptability of hydrogel electrolytes is listed in terms of temperature, humidity, and air composition. Fourth, the compatibility of electrolyte–electrode interface is discussed from physical properties of hydrogels. Finally, the prospect for development and application of hydrogels is put forward.     

聚合物锂离子电池界面相容性的研究进展

聚合物锂离子电池作为储能装置在电子产品中具有广泛的应用前景。电极/聚合物电解质(E/P)界面相容性是影响聚合物锂离子电池电导率、安全性、机械性能的重要影响因素之一。研究E/P界面的电化学反应及形成机理,是解决相容性问题的关键。本文综述了近年来有关聚合物锂离子电池E/P界面相容性及相关研究技术的进展,并对聚合物锂离子电池界面相容性的相关研究进行了展望。     

Enhancing toughness of poly (lactic acid)/Thermoplastic polyurethane blends via increasing interface compatibility by polyurethane elastomer prepolymer and its toughening mechanism

Due to the environmental pollution caused by the petroleum-based polymer, poly (lactic acid) (PLA), a biodegradable and biocompatible polymer that obtained from natural and renewable sources, has attracted widespread attention. However, the brittleness of PLA greatly limits its application. In this study, the super toughened PLA-based blends were obtained by compatibilizing the PLA/thermoplastic polyurethane (TPU) blends with the polyurethane elastomer prepolymer (PUEP) as an active compatibilizer. The mechanical properties, thermal properties and corresponding toughening mechanism of PLA/TPU/PUEP system were studied by tensile test, instrumented impact test, dynamic mechanical analysis (DMA), scanning electronic microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All the results demonstrate that the isocyanate (−NCO) group in PUEP is successfully reacted with the –OH groups at both sides of the PLA and the obtained polyurethane (PU)~PLA copolymer (PU ~ cõ PLA) significantly improves the interfacial compatibility of PLA/TPU blends. The gradually refined dispersed phase size and fuzzy phase interface as displayed in SEM images suggest a good interfacial compatibilization in the PLA/TPU/PUEP blends, probably due to the isocyanate reaction between PLA and PUEP. And the interfacial reaction and compatibilization among the components led to the formation of super toughened PLA/TPU/PUEP blends. And the instrumented impact results indicate that most of the impact toughness is provided by the crack propagation rather than the crack initiation during the entire fracture process.     

Synthesis of two A-B-C type conjugated amphiphilic triblock fullerene derivatives and their application in organic solar cells

Two A-B-C type conjugated amphiphilic triblock fullerene derivatives C60-2 HMTPB and C60-2 EHTPB were obtained in multi steps synthesis with three different blocks,and the amphiphilic diblock molecular C60-4 TPB was also preferred as a reference.When as modifying layer on zinc oxide(ZnO),the three fullerene derivatives can all reduce the work function of ZnO via modulation of the interfacial dipoles and lead a better electrical coupling.As introducing treatment of toluene,the obvious self-assembly of fullerene derivatives were observed,which were supported by X-ray diffraction and contact angle of water measurement.Base on PTB7-Th:PC71 BM system,the inverted organic solar cells devices with structure of ITO/ZnO/fullerene derivatives/PTB7-Th:PC71BM/Mo03/Al got power conversion efficiencies of 8.62%,8.83%and 9.00%for C60-4 TPB,C60-2 HMTPB and C60-2 EHTPB,respectively,compared 8.13%of devices with bare ZnO.The result of conjugated amphiphilic triblock fullerene derivatives provides a straightforward approaching by simultaneously modulating the morphology and interfacial work function of ZnO,which can also lead high performance in optoelectronic devices.     

Direct diazotization of graphite nanoplatelets with melamine and their favorable application in epoxy resins

The ease of undesirable agglomeration and a low efficiency are two problems that restrict the application of graphite nanoplatelets (GNPs) in epoxy resins (EP). Herein, a new strategy with melamine (MEL) as the precursor to functionalize GNPs chemically, which form a bonding layer that is compatible with epoxy matrix, is reported. The MEL fragments with secondary amine groups were grafted uniformly on the GNPs surface by covalent junctions to exploit the diazonium chemistry. This behavior led to a better dispersion and a stronger interaction with the epoxy matrix and resulted in an enhanced glass transition temperature and bending strength, compared with the pure EP. When only 1 wt% functionalized GNPs (f‐GNPs) was used, the Tg of the modified EP raised of about 15°C compared with pure EP, and the bending strength increased by approximately 39%. The dielectric constant of the EP with f‐GNPs was impacted slightly, and the dielectric loss decreased. At 10⁵ Hz, the dielectric loss of the EP with 1 wt% f‐GNPs decreased by approximately 11% compared with pure EP. Therefore, diazotization modification of the GNPs is a useful approach to improve the compatibility in nanoparticle networks.     

Design of aluminum trihydroxide and P‐N core‐shell structures and their synergistic effects on halogen‐free flame‐retardant polyethylene composites

In order to improve the performance of inorganic/organic composites, aluminum trihydroxide (ATH) core composites with a styrene‐ethylene‐butadiene‐styrene block copolymer grafted with maleic anhydride (MAH‐g‐SEBS) shell phase, and P‐N flame retardant as a synergistic agent, were prepared through an interface design. The effects of polyethylene glycol (PEG) content on the interfacial interaction, flame retardancy, thermal properties, and mechanical properties of high‐density polyethylene (HDPE)/ATH composites were investigated by small angle X‐ray diffraction, rotational rheometer, limiting oxygen index, thermogravimetric analysis (TGA), and tensile testing. The ATH synergistic effects of P‐N flame‐retardant improved the combustion performance of HDPE/ATH/PEG(3%)/MAH‐g‐SEBS/P‐N (abbreviated as HDPE/MH3/M‐g‐S/P‐N) composite by forming more carbon layer, increased the elongation at break from 21% to 558% compared to HDPE/ATH, and increased the interface thickness from 0.447 to 0.891 nm. SEM results support the compatibility of ATH with HDPE increased and the interfacial effect was enhanced. TGA showed the maximum decomposition temperature of the two stages and the yield of the residue at high temperature increased first and then decreased with the increase of PEG content. Rheological behavior showed the storage modulus, complex viscosity, and the relaxation time initially increased and then decreased with the increase of PEG content indicating PEG, M‐g‐S, and ATH powder gradually formed a partial coating, then a full coating, and finally an over‐coated core‐shell structured model.     

Compatibility and fungal degradation of poly[(R)-3-hydroxybutyrate]/aliphatic copolyester blend

Poly[(R)-3-hydroxybutyrate] (PHB) was blended with an aliphatic copolyester, which was synthesized by the esterification of adipic acid, ethylene glycol, and lactic acid. The blend showed a single T_g, which varied systematically but convexly upwards with the composition. The growth rate of PHB spherulites, the crystallization temperature, and the equilibrium melting temperature of the blend were decreased as the amount of the copolyester was increased. Therefore, the blend system was determined to be compatible. However, the degree of crystallinity, and the enthalpies of crystallization and fusion of PHB in the blend remained almost constant, regardless of the compositional change, although the crystallization rate was decreased upon blending. No chemical change such as transesterification was observed as a result of the blending, yet there was a slight change in the crystalline morphology of PHB. The rate of fungal degradation was lowered with an increase in the copolyester content of the blend. © 1996 John Wiley & Sons, Inc.     

Synthesis of polymers having a phospholipid polar group connected to a poly(oxyethylene) chain and their protein adsorption-resistance properties

New methacrylates having a phospholipid polar group which was connected to various lengths of poly(oxyethylene) chains to form a polymerizable group (MEOnPC) were synthesized. The MEOnPC could polymerize with n-butyl methacrylate (BMA) in ethanol using a conventional radical polymerization technique. The unit mole fraction of MEOnPC in the polymer corresponded to that in the feed monomer solution. The MEOnPC polymers were soluble in ethanol, insoluble in water, but swelled in water and became hydrated. On the surface of a poly(BMA) membrane coated with MEOnPC, the phosphorylcholine groups of the MEOnPC unit present were determined by x-ray photoelectron spectroscopy. As a fundamental evaluation for biomedical materials, adsorption of one of the plasma proteins, fibrinogen, on acrylic beads coated with the MEOnPC polymers was evaluated. The amount of fibrinogen adsorbed on the MEOnPC polymer was smaller than that on the original acrylic beads, poly(BMA) and poly(2-hydroxyethyl methacrylate). The increase in the MEOnPC unit mole fraction in the polymer showed more effective protein adsorption-resistant properties. © 1996 John Wiley & Sons, Inc.