Behavior of biodegradable composites based on starch reinforced with modified cellulosic fibers

The aims of this study were to develop composite films based on potato starch and cellulose modified with toluenediisocyanate, to investigate their morphology and structure, and to evaluate their behavior to enzymatic hydrolysis and their potential use to manufacture of biodegradable seedling pots. The effects of modified cellulosic fibers upon mechanical properties and biodegradability of composite materials based on starch matrix were investigated by tensile strength tests, Fourier infrared spectroscopy, X‐ray diffraction, and dynamic vapor sorption. The behavior of the films to enzymatic hydrolysis with amylase and cellulase was studied; the kinetic of enzymatic hydrolysis and characterization of materials are reported. Chemical modification of cellulose improves tensile strength with about 47%, and decreases the biodegradability of composites making them more resistant to microbial attack, thus prolonging their shelf life. Copyright © 2015 John Wiley & Sons, Ltd.     

Wood plastic composites weathering: Visual appearance and chemical changes

The effects of outside and accelerated (xenon-arc and UVA) weathering on the visual appearance and chemical changes of wood plastic composite (WPC) formulations based on high density polyethylene (HDPE) and polypropylene (PP) were investigated. Colorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were employed in this study. The study showed that for both outside and accelerated weathering, longer exposure time increased the degree of color change (and lightness), carbonyl concentrations, and wood loss on weathered WPC surfaces. HDPE-based WPC exhibited decreased lightening, carbonyl concentrations, and wood content loss when compared to PP-based WPC. From this study, relationships between chemical and color changes that occurred during exterior weathering of HDPE-based WPC were established. Oxidation and degradation of wood lignin influenced WPC color changes (lightening) during weathering.     

Electrospun hyperbranched polylactic acid–modified cellulose nanocrystals/polylactic acid for shape memory membranes with high mechanical properties

The polylactic acid (PLA) nanofiber membranes reinforced with hyperbranched PLA‐modified cellulose nanocrystals (H‐PLA‐CNCs) were prepared by electrospinning. The H‐PLA‐CNCs and the nanofiber membranes were researched by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The outcomes embodied that the cellulose nanocrystals (CNCs) could be successfully improved by the hyperbranched PLA, which would offer powerful CNCs/matrix interfacial adhesion. Thus, the mechanical and shape memory properties of PLA can be improved by adding the H‐PLA‐CNCs. In particular, when the addition of H‐PLA‐CNCs was 7 wt%, the tensile strength and an ultimate strain of PLA composite nanofiber membranes was 15.56 MPa and 25%, which was 228% and 72.4% higher than that of neat PLA, respectively. In addition, the shape recovery rate of the PLA/5 wt% H‐PLA‐CNCs composite nanofiber membrane was 93%, which was 37% higher than that of neat PLA. We expected that this present study would provide unremitting efforts for the development of more effective approaches to prepare biology basic shape memory membranes with high mechanical properties.     

Chemically imaging the interaction of acetylated nanocrystalline cellulose (NCC) with a polylactic acid (PLA) polymer matrix

The non-covalent interaction of acetylated nanocrystalline cellulose (AC-NCC) with polylactic acid (PLA) in a composite blend has been studied at the micron scale by synchrotron Fourier transform infrared (FTIR) microspectroscopy. Microtomed sections of AC-NCC in PLA showed strong, localized carbonyl stretching (νC=O) absorbance characteristic of the cellulose acetylation, and this was observed on the surface of larger aggregated AC-NCC particles. A shift in the νC=O IR absorption peak of AC-NCC in PLA, relative to unblended AC-NCC was observed, which is indicative of an intermolecular interaction between AC-NCC and PLA matrix. Acetylation can therefore potentially improve the performance of the composite by enabling linkages between carbonyl groups, helping to establish a good stress transfer between the fiber and the matrix. This could in turn lead to a material with high yield elastic modulus. This is the first reported chemical imaging of acetylated nanocrystalline cellulose-based composite materials using synchrotron FTIR microspectroscopy.     

Preparation and properties of cellulose/silver nanoparticle composites with in situ-generated silver nanoparticles using Ocimum sanctum leaf extract

In the present work, silver nanoparticles were in situ-generated in cellulose matrix using Ocimum sanctum leaf extract as a reducing agent. Regenerated wet cellulose films were first immersed in O. sanctum leaf extract and then it was allowed to diffuse into the films. The leaf extract–diffused wet films were dipped in different concentrated aq.AgNO₃ solutions. The leaf extract inside the wet films reduced AgNO₃ into nanosilver. The dry composite films were black in color. Some of the nanoparticles were also formed outside the film in the solution. The nanoparticles were viewed by transmission electron microscopy and scanning electronic microscopy techniques. The composite films showed good antibacterial activity. The cellulose, matrix, and the composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis techniques. The tensile properties of the composite films were higher than those of the matrix. These biodegradable films can be used for packaging and medical purposes.     

Study on Refined Triticale Straw Reinforced PP Composites

Triticale straw(TS) and refined triticale straw(RTS) were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR) and thermogravimetric analysis(TGA) in detail, and their application in polypropylene(PP) composite was explored. RTS was obtained by refining TS with environmentally benign processes, by which hemicelluloses and lignin were effectively removed. This was proved by FTIR analysis. The effect of cellulose content on the composite thermal stability and mechanical properties was also examined. RTS has better thermal stability than TS because RTS has lower flammable noncellulose ratio. T_5%(temperature with mass loss of 5%) of RTS could be more than 200℃. It is high enough to meet the requests of processing most polyolefin composites. Both TS and RTS acted as nucleating agents in PP crystallization process. TS was proved to be a filler of the composite, and RTS to be a reinforcing material for the composite. The flexural strength and modulus of RTS/PP increased about by 5% and more than 100%, respectively, compared with those of PP, when the mass fraction of RTS and compatibilizer were 30% and 2%, respectively. The thermal stability of RTS/PP composites was also better than that of TS/PP composites.     

Characterization and properties of carbon/PMR-15 composites

PMR (polymerization of monomer reactants) -15 was formulated to use as a matrix resin for high performance carbon fiber-reinforced composite materials. Monomers for the PMR-15 were characterized using Fourier transform infrared spectroscopy. Molecular weight change during cure was investigated using gel permeation chromatography. Thermal analysis was carried out to investigate glass transition and thermal degradation. Cure behavior of a glass/PMR-15 prepreg was investigated using a dynamic mechanical analyzer. Flexural strength of a cured carbon/PMR-15 composite was affected by cure temperature and pressure. The morphology of the cured carbon/PMR-15 was affected by cure conditions as well as by the surface conditions of the carbon fibers. A scanning electron micrograph of the composite made of untreated carbon fibers showed a void-trapped morphology.     

Intumescent flame retardation and silane crosslinking of PP/EPDM elastomer

This study deals with the silane crosslinking and intumescent flame retardation of polypropylene/ethylene‐propylene‐diene copolymer (PP/EPDM) elastomers. The effect of silane crosslinking on the flame retardancy of the PP/EPDM composites containing melamine phosphate (MP) and dipentaerythritol (DPER) was studied by limiting oxygen index, UL 94 and cone calorimetry tests. The chemical composition of the silane crosslinked and flame retarded PP/EPDM composites treated at different temperatures was studied by X‐ray photoelectron spectroscopy and real time Fourier transform infrared (FTIR) spectrometry. Thermal decomposition and crystallization behavior of the PP/EPDM composites were investigated using thermogravimetric analysis and differential scanning calorimetry, respectively. Moreover, the mechanical properties of the composites were also studied. It is found that the flame retardancy, mechanical properties, and thermal decomposition behavior of the composites are influenced by silane grafting and crosslinking. Copyright © 2008 John Wiley & Sons, Ltd.     

Rheological behavior of cellulose/silk fibroin blend solutions with ionic liquid as solvent

The rheological behavior of cellulose and silk fibroin blend in 1-butyl-3-methylimidazolium chloride was studied. The data from the rheological results was analyzed to understand the microstructure of the blend solutions. The viscosity and dynamic modulus of the blend solution decreased with increasing ratio of silk fibroin. While comparing the experimental results with the calculated data from the log-additivity rule, it is revealed that zero-shear viscosity, dynamic modulus show positive–negative deviations and a typical continuous–discrete type of morphology could be imaged. At lower shear rate, the change of phase morphology took place at the ratio of about 0.5 volume fraction of cellulose. However, the blend solution showed positive deviations for all cellulose/silk fibroin blend ratios at high shear rate, which indicates that the dispersion of cellulose and silk fibroin was improved under shear stress. The properties of cellulose/silk fibroin blends observed by Fourier transform infrared spectroscopy and scanning electron microcopy agreed with the result from rheology.     

Hydrophobization and characterization of internally crosslink-reinforced cellulose fibers

Transforming hydrophilic cellulose fibers into hydrophobic, non-hygroscopic fibers could potentially lead to a variety of new products, such as flexible packaging, self-cleaning films and strength-enhancing agents in polymer composites. To achieve this, softwood cellulose pulp was chemically modified with successive chemical treatments. First the C2 and C3 hydroxyl groups of the glucose units were selectively oxidized by periodate oxidation to reactive dialdehyde units on the cellulose chain, followed by a Schiff base reaction with 1,12-diaminododecane to crosslink the microfibrils within the fiber wall. This was done, because introducing high levels of alkylation resulted in fiber disintegration, which could be prevented by crosslinking. After internal crosslinking a second Schiff base reaction was performed with butylamine. This procedure yielded highly hydrophobic and low-hygroscopic cellulosic materials. The modified cellulose fibers were investigated by a variety of techniques, including Fourier transform infrared spectroscopy, nuclear magnetic resonance, field-emission scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, moisture sorption and water contact angle measurements. The water uptake of the fibers after being modified reduced from 4 to around 1 %. Various reaction conditions were studied for optimum performance.     

Surface esterification of cellulose fibers: characterization by DRIFT and contact angle measurements

The surface chemical modification of microcrystalline cellulose and cellulose fibers obtained from different sugar cane bagasse pulping processes, viz. Kraft, organosolv ethanol/water and organosolv/supercritical carbon dioxide, were studied in heterogeneous conditions using modest amounts of octadecanoyl and dodecanoyl chloride. The ensuing surfaces acquired a non-polar character, suitable for incorporating these fibers as reinforcing agents in composite materials based on polymeric matrices. The success of these chemical modifications was assessed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, elemental analysis, scanning electron microscopy (SEM) and contact angle measurements. In particular, the dynamic and equilibrium contact angle measurements, before and after the treatments, revealed that the value of the polar component (gamma(s)p) of the surface energy had decreased very considerably following the modification.     

Nanocomposite films based on cellulose reinforced with nano-SiO2: microstructure, hydrophilicity, thermal stability, and mechanical properties

Microcrystalline cellulose/nano-SiO₂ composite films have been successfully prepared from solutions in ionic liquid 1-allyl-3-methylimidazolium chloride by a facile and economic method. The microstructure and properties were investigated by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, water contact angle, thermal gravimetric analyses, and tensile testing. The results revealed that the well-dispersed nanoparticles exhibit strong interfacial interactions with cellulose matrix. The thermal stability and tensile strength of the cellulose nanocomposite films were significantly improved over those of pure regenerated cellulose film. Furthermore, the cellulose nanocomposite films exhibited better hydrophobicity and a lower degree of swelling than pure cellulose. This method is believed to have potential application in the field of fabricating cellulose-based nanocomposite film with high performance, thus enlarging the scope of commercial application of cellulose-based materials.     

Monitoring the polymerization process of polypyrrole films by thermogravimetric and X-ray analysis

Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.     

Thermomechanical behaviors and dielectric properties of polyaniline‐doped para‐toluene sulfonic acid/epoxy resin composites

Composites based on conductive organic/inorganic fillers dispersed in insulating matrix have been widely investigated because of their widespread applications such as electromagnetic shielding, electrostatic discharge, and sensors. In this context, novel composite materials based on epoxy resin matrix charged with polyaniline (PANI)‐doped para‐toluene sulfonic acid were elaborated. Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy were used to check the structure and the morphology of the samples. Viscoelastic behavior and thermal stability of the composites were explored by dynamic mechanical thermal analysis and thermogravimetric analysis. It was shown that the PANI particles exhibited a partial crystalline structure and were homogeneously dispersed in epoxy matrix. Consequently, this structure affected the thermal stability and viscoelastic properties of the composites. Furthermore, the dielectric and electrical properties were investigated up to 1 MHz. Measurements of dielectric properties revealed that with loading fillers in matrix, the dielectric parameters increased to high values at low frequency then decreased at values around 40 and 32 of real and imaginary parts, respectively, at 1 MHz with 15% of PANI content. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal analysis and crystallinity study of cellulose nanofibril-filled polypropylene composites

The isothermal and non-isothermal decompositions of cellulose nanofiber (CNF) and microfibrillated cellulose (MFC)-filled polypropylene (PP) composites were evaluated and compared with microcrystalline cellulose (MCC)-filled composites by means of thermogravimetric analysis (TG). X-ray diffraction was employed to evaluate crystallinity of the composites. The degree of maximum thermal degradation (ultimate DTG peak value) increased and thermal degradation onset temperature decreased as the cellulose content increased because the thermal stability of cellulose fillers is lower than that of neat PP, but the thermal degradation of the composite was hindered at higher temperature conditions because of the increased residual mass content of the cellulose nanofibril fillers compared to the matrix polymer. The isothermal residual mass of the cellulose nanofibril-filled PP composites under melt blending and injection molding temperatures was decreased marginally by incorporation of the cellulose reinforcement but still exhibited considerable isothermal stability. The raw materials and composites examined in this study were not affected by the manufacturing process temperatures utilized to produce the composites. The MCC decreased the composite crystallinity while the nano-sized cellulose (CNF and MFC) did not appear to have an effect on crystallinity.     

Structure‐property relationship,rheological behavior,and thermal degradability of poly(lactic acid)/fulvic acid amide composites

Fulvic acid amide (FAA) was synthesized with fulvic acid (FA) and urea. The structure of FAA was characterized by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Poly(lactic acid)/fulvic acid amide (PLA/FAA) composites were prepared by melt blending and compression molding. The nucleation effect of FAA on PLA was investigated by differential scanning calorimetry and polarized optical microscopy. Structure‐property relationship of PLA/FAA composites showed that FAA accelerated crystallization rate of PLA and improved toughness of PLA. Rotational rheological behavior of PLA/FAA composites showed that FAA increased the storage modulus of PLA. Capillary rheological analysis showed that the apparent viscosities of PLA composites were highly increased after the introduction of the FAA nucleating agent. Moreover, thermogravimetric analysis demonstrated that thermal degradability of PLA/FAA composites has been increased significantly compared with the neat PLA.     

The influence of pre-treatment of Spartium junceum L. fibres on the structure and mechanical properties of PLA biocomposites

Different chemical pre-treatments of Spartium junceum L. fibres using alkali (NaOH), nanoclay (MMT) and Citric acid (CA) with the aim of producing biodegradable composite material are discussed. As environmental requirements in processing technologies have been higher in recent years, the Polylactic acid (PLA) is used in this research as a matrix, due to its renewability, biodegradability and biocompatibility. Biocomposites are prepared by reinforcing PLA with randomly oriented, short Spartium junceum L. fibres in order to increase material strength. The effects of different pre-treatments of Spartium junceum L. fibres on the mechanical properties of final biocomposite material are examined. Fibre tenacity is studied using Vibroscop and Vibrodyn devices. Tensile strength of biocomposite material was measured on the universal electromechanical testing machine Instron 5584. The results indicate that biocomposites reinforced with fibres modified with MMT and CA show upgraded mechanical properties of the final composite material in comparison with the composite materials reinforced with referenced (nontreated) fibres. Infrared spectra of tested fibres and biocomposites were determined with Fourier transform infrared spectroscopy using Attenuated total reflection (FT-IR ATR) sampling technique and the influence of fibre modifications on the fibre/polymer interfacial bonding was investigated. The interface of Spartium/PLA composites was observed with scanning electron microscope (SEM) and it was clearly visible that biocomposites reinforced with fibres modified by MMT and CA showed better interaction of fibres and matrix.     

Outdoor and accelerated weathering tests for polypropylene and polypropylene/talc composites: A comparative study of their weathering behavior

In this study, the comparisons of degradation behavior of polypropylene(PP) and PP/talc composites were carried out with one outdoor weathering test and three accelerated weathering (xenon, metal halide and carbon arc lamps) tests, respectively. The outdoor exposure vigorously advanced these degradations with the lowest amount of UV exposure energy. It was found that the degradation rates were affected by the visible light intensity in the light sources. In the case of the existence of talc compound, the degradation was synergistically accelerated by the exposures of the sunshine, the xenon and the metal halide lamps having higher visible light intensities. In addition, the degradations of the PP and the PP/talc composites were found to be synergistically accelerated by sunlight exposure and the acid rain, too.     

Application of dynamic 2D FTIR to cellulose

Cellulose, the dominant polymer in the biosphere, is a homopolysaccharide composed of (1,4)-β-d-glucopyranose. Interactions between and within the cellulose polymer chains are mainly determined by inter- and intramolecular hydrogen bonds, which are therefore mainly responsible for mechanical properties of cellulosic materials. The coupling of dynamic mechanical analysis (DMA) and 2D step-scan Fourier transform infrared (FTIR) spectroscopy, is shown to be a very promising way of investigating these submolecular interactions in cellulosic materials. The broad and unstructured band in the OH-stretching vibration region (3100 and 3700 cm⁻¹) of the cellulose vibrational spectra, which contains information about the intra- and intermolecular hydrogen bonds, can be unraveled by this new technique. In the experiments reported here, cellulose sheets have been stretched sinusoidally at low strains while being irradiated with polarized infrared light. For the obtained dynamic IR signals (the in-phase and the out-of-phase responses of the sample), the dynamic IR cross-correlation was defined. It consists of two terms which are referred to as the synchronous and the asynchronous 2D infrared correlation intensities. In the 2D spectra, obtained by DMA–FTIR, several distinct peaks are observed in the OH-range between 3700 and 3100 cm⁻¹ which may be related to specific interactions.     

Microfibrillated cellulose/cellulose acetate composites: Effect of surface treatment

Microfibrillated cellulose (MFC), which consists of a web‐like array of cellulose fibrils having a diameter in the range of 10–100 nm, was incorporated into a cellulose acetate (CA) matrix to form a totally biobased structural composite. Untreated and a 3‐aminopropyltriethoxysilane (APS) surface treated MFC was combined with a CA matrix by film casting from an acetone suspension. The effectiveness of the surface treatment was determined by infrared spectroscopy and X‐ray photoelectron spectroscopy. The Young's moduli of APS treated MFC composite films increase with increasing MFC content from 1.9 GPa for the CA to 4.1 GPa at 7.5 wt % of MFC, which is more than doubled. The tensile strength of the composite film increases to a maximum of 63.5 MPa at 2.5 wt % compared to the CA which has a value of 38 MPa. The thermal stability of composites with treated MFC is also better than the untreated MFC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 153–161, 2010