Bio-based Nanocomposites Research Articles

식물성오일 레진을 이용한 고기능성 나노 복합재료의 개발

본 연구에서는 식물성 오일로부터 여러 가지 기능기를 가진 soybean resin(AESO, MAESO)을 제조하였으며, nanoclay를 사용하여 새로운 고기능성 바이오-나노 복합 재료를 개발하였다. 또한 제조된 soybean resin을 바인더로 이용하여 <TEX>$TiO_2$</TEX> 광전극을 제조하고 친환경 염료감응형 태양전지를 개발하다. 제조된 나노복합재료의 형태는 고분자의 삽입에 의해 층간 간격이 증가된 형태와 박리된 형태를 조절하였으며 나노 클레이 함량이 증가됨에 따라 물리적 성질이 증가하였다. 또한 COOH기가 첨가된 MAESO에서 분산도가 향상되었고 초음파 처리에 의해 분산도가 더욱 향상되어 물리적 특성이 현저히 향상되었다. 또한 <TEX>$TiO_2$</TEX>를 질산처리 한 후 soybean resin을 바인더로 이용하여 나노 다공성 <TEX>$TiO_2$</TEX> 광전극을 제조하였으며 염료를 흡착시킨 후 염료감응형 태양전지를 제조하였다. AESO와 MAESO를 바인더로 제조한 <TEX>$TiO_2$</TEX> 광전극에서는 향상된 분산성과 표면적 증가로 인해 염료 흡착량이 증가하였다. 이로 인해 높은 전류밀도를 나타내었으며, 첨가된 기능기의 영향으로 <TEX>$TiO_2$</TEX> 계면의 저항이 낮아져 매우 좋은 광전기화학적 특성과 높은 효율을 나타내었다. In this study, in order to develop renewable bio-based nanocomposites, multi-functional nanocomposites from soybean resins (AESO, MAESO) and nanoclay were prepared. Photoelectrodes for environmental friendly dye-sensitized solar cell using soybean resin were also prepared. Organo-modified nanoclay was directly dispersed in functionalized soybean resins after mixing with styrene as a comonomer and radical initiator was used to copolymerize the nanocomposites. The observed morphology was a mixture of intercalated/exfoliated structure and the physical properties were improved by adding nanoclay. A nanocomposite using MAESO, which added COOH functional group to the soybean resin, showed better dispersibility than AESO composites. Ultrasonic treatment of the nanocomposites also improved the physical properties. Nanoporous <TEX>$TiO_2$</TEX> photoelectrode was also prepared using soybean resins as a binder, after acid-treatment of <TEX>$TiO_2$</TEX> surface using nitric acid. Dye-sensitized solar cells were prepared after adsorbing dye molecules on it. The <TEX>$TiO_2$</TEX> photoelectrode prepared using soybean binder had high current density because of increased surface area by improved dispersibility. The photoelectrochemical properties and conversion efficiency of the solar cell were significantly improved using the soybean binder.

Next-generation biopolymers: Advanced functionality and improved sustainability

Abstract

Bio-based nanocomposites by in situ cure of phenolic prepolymers with cellulose whiskers

A series of resole-type phenolic resin-based nanocomposites, uniformly filled with cellulose nanowhiskers (CNWs), was successfully fabricated via direct solution mixing, then solvent-exchange with DMF and finally stepwise thermal curing. Dynamic mechanical analysis evidenced a moderate reinforcing effect with a minimum CNWs weight content of 5.0 wt% especially above the resin glass transition temperature (T g ). The Halpin–Kardos model provided a good description of the CNWs reinforcing effect, suggesting perhaps the contribution of whiskers/matrix interactions rather than that of whiskers/whiskers interactions. Differential scanning calorimetry (DSC) further indicated that the nanowhiskers enhanced the resin cure, resulting in a more extensive degree of cure. Finally, the CNWs were found to only slightly lower the thermal stability of PF resins. In spite of a modest reinforcing effect, it is proposed that CNWs are also interesting fillers for high modulus and high T g thermosetting resins that require high temperature cure.

Hybrid layer-by-layer assembly based on animal and vegetable structural materials: multilayered films of collagen and cellulose nanowhiskers

Layer-by-layer (LBL) assembly was used to combine crystalline rod-like nanoparticles obtained from a vegetable source, cellulose nanowhiskers (CNWs), with collagen, the main component of skin and connective tissue found exclusively in animals. The film growth of the multilayered collagen/CNW was monitored by UV-Vis spectroscopy and ellipsometry measurements, whereas the film morphology and surface roughness were characterized by SEM and AFM. UV-Vis spectra showed the deposition of the same amount of collagen, 5 mg m−2, in each dipping cycle. Ellipsometry data showed an increment in thickness with the number of layers, and the average thickness of each bilayer was found to be 8.6 nm. The multilayered bio-based nanocomposites were formed by single layers of densely packed CNWs adsorbed on top of each thin collagen layer where the hydrogen bonding between collagen amide groups and OH groups of the CNWs plays a mandatory role in the build-up of the thin films. The approach used in this work represents a potential strategy to mimic the characteristics of natural extracellular matrix (ECM) which can be used for applications in the biomedical field.

Crosslinking as an Efficient Tool for Decreasing Moisture Sensitivity of Biobased Nanocomposite Films

Chitosan-nanoclay bio-hybrid films were successfully crosslinked with glutaraldehyde, genipin and glyoxal. Moisture sensitivity of films decreased as a result of crosslinking which led to improved barrier properties against water vapor and oxygen. Films containing chitosan (6.6 g/m2) with genipin (3.3 g/m2) and nanoclay (6.6 g/m2) had water vapor transmission rate of 72 g × 100 µm/(m2 × 24 h) which was 34% lower as compared to pure chitosan and 30% lower as compared to chitosan/nanoclay without crosslinkers. Glyoxal induced crosslinking resulted in 92% reduction in oxygen transmission rate at 80% relative humidity as compared to pure chitosan films. Oxygen transmission through glyoxal (3.3 g/m2) treated chitosan/nanoclay film was 2.8 cm3 × 100 µm/(m2 × 24 h) which was 53% lower as compared to chitosan/nanoclay without crosslinkers. In addition, nanoclay and especially glyoxal crosslinking prevented the water vapor sorption of chitosan considerably. Crosslinking may be used as an efficient tool for enhancing the exploitability of naturally hydrophilic biopolymers towards new high-value applications, such as food packaging.

Effect of glycerol on the morphology of nanocomposites made from thermoplastic starch and starch nanocrystals

Fully bio-based nanocomposites were prepared using starch nanoparticles obtained by acidic hydrolysis of waxy maize starch granules as reinforcement. The same type of starch, which contains 99wt.% amylopectin, was used to prepare glycerol plasticized and unplasticized matrices. The X-ray diffraction pattern of the plasticized reinforced materials displays both A and B-type peaks, showing that the crystalline structure of the nanocrystals was not affected by processing. The storage modulus of the composite material increases, with respect to the unfilled film, by 470% at 50°C, while the permeability increases by 70%. This is probably due to a good association of glycerol with the nanoparticles leading to a fibrillar structure, studied by scanning electron microscopy of plasticized and unplasticized composites.

Bio-based polymer nanocomposites from UPE/EML blends and nanoclay: Development, experimental characterization and limits to synergistic performance

Bio-based nanocomposites, defined as blends of petroleum and vegetable oil resins reinforced with nanoparticles, can lead to synergistic material property enhancement; and evaluation of their performance and limits can allow for their optimal design. An array of 12 nanocomposite designs with up to 30% epoxidized methyl linseedate (EML) and up to 5.0 wt.% nanoclay in unsaturated polyester were manufactured using a solvent-based technique. Mechanical, thermal and diffusion properties of resulting composites were experimentally characterized. Reduction of mechanical and transient properties due to bio-resin blending were recovered by the addition of nanoclay for EML contents of up to 20%, while 30% EML composites showed little improvement. Systems with 2.5 wt.% nanoclay and up to 20% EML showed optimal performance with balanced properties and processing ease. The developed eco-friendly bio-based nanocomposites exhibit good stiffness–toughness balance along with improvements in other mechanical and transient properties, thereby showing potential for use in structural applications.

Biobased Nanocomposites from Layer-by-Layer Assembly of Cellulose Nanowhiskers with Chitosan

A new biodegradable nanocomposite was obtained from layer-by-layer (LBL) technique using highly deacetylated chitosan and eucalyptus wood cellulose nanowhiskers (CNWs). Hydrogen bonds and electrostatic interactions between the negatively charged sulfate groups on the whisker surface and the ammonium groups of chitosan were the driving forces for the growth of the multilayered films. The film growth was followed by UV-vis spectroscopy through the maximum value of the absorption band at 194 nm and showed the deposition of 14.7 mg.m(-2) of chitosan polymer in each cycle. Scanning electron microscopy showed high density and homogeneous distribution of CNWs adsorbed on each chitosan layer. Cross-section characterization of the assembled films indicates an average of approximately 7 nm of thickness per bilayer. The results presented in this work indicate that the methodology used can be extended to different biopolymers for the design of new biobased nanocomposites in a wide range of applications such as biomedical and food packaging.

A study of the physical and tribological properties of biobased polymer–clay nanocomposites at different clay concentrations

Novel biobased nanocomposites have been prepared by the cationic copolymerization of conjugated low saturated soybean oil with styrene and divinylbenzene, and a reactive organomodified montmorillonite (VMMT) clay as reinforcing phase. Microscale tribological measurements were performed on samples with different concentration of VMMT (0%, 1% and 5%, w/w) using a ball-on-flat reciprocating microtribometer. Friction and wear behavior during dry sliding were evaluated using spherical (1.2 mm radius) steel probe as well as a conical (100 μm radius, 90° cone angle) diamond probe. Friction behavior was evaluated from single strokes at ramped normal loads, whereas wear experiments were evaluated from 10 to 1000 reciprocating cycles at fixed normal loads. Contact profilometry and scanning electron microscopy of wear tracks were used to elucidate deformation mechanisms in the various samples.

All-cellulose nanocomposites by surface selective dissolution of bacterial cellulose

All-cellulose nanocomposites using bacterial cellulose (BC) as a single raw material were prepared by a surface selective dissolution method. The effect of the immersion time of BC in the solvent (lithium chloride/N,N-dimethylacetamide) during preparation on the nanocomposite properties was investigated. The structure, morphology and mechanical properties of the nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and tensile testing. The optimum immersion time of 10 min allowed the preparation of nanocomposites with an average tensile strength of 411 MPa and Young’s modulus of 18 GPa. With the longest immersion time of 60 min, the prepared composite sheet turns to express a very high toughness characteristic possessing a work-to-fracture as high as 16 MJ/m3. These biobased nanocomposites show high performances thanks to their unique structure and properties.

&lt;p&gt;Bio-based Nanocomposites: An Alternative to Traditional Composites&lt;/p&gt;

Polymer matrix composites (PMC), often referred to as fiber reinforced plastics (FRP), consist of fiber reinforcement (E-glass, S2-glass, aramid, carbon, or natural fibers) and polymer matrix/resin (polyester, vinyl ester, polyurethane, phenolic, and epoxies). Eglass/polyester and E-glass/vinyl ester composites are extensively used in the marine, sports, transportation, military, and construction industries. These industries primarily use low-cost open molding processes, such as manual/spray lay-up. Polyester and vinyl ester resin systems produce styrene emissions. Because of the stringent EPA regulations on styrene emissions, composite manufacturers are interested in using low-cost closed molding processes, such as vacuum-assisted resin transfer molding (VARTM) and styrene-free resin systems such as non-foam and full-density polyurethanes (PUR). Polyurethanes are polymers created by addition of polyisocyanates and polyols. The polyol component in polyurerhane can be produced from soybean oil. This study demonstrates that with the proper addition of nanoparticles, mechanical properties of soy-based polyurethane can be enhanced. These nanomodified soy-based polyurethane/glass composites manufactured by using the low-cost VARTM process provide alternatives to traditional glass/polyester and glass/vinyl ester composites. These composites will be more environmental friendly for two reasons: (a) Polyurethane does not produce styrene emission, thereby, resulting in a safer work place and (b) Polyol is made from a renewable resource (soybean oil).

A new bio-based nanocomposite: fibrillated TEMPO-oxidized celluloses in hydroxypropylcellulose matrix

Utilization of TEMPO-oxidized celluloses in bio-based nanocomposites is reported for the first time. TEMPO-oxidized wood pulps (net carboxylate content 1.1 mmol/g cellulose) were fibrillated to varying degrees using a high intensity ultrasonic processor. The degree of fibrillation was controlled by varying sonication time from 1 to 20 min. The sonication products were then characterized independently and as fillers (5 wt% loading) in hydroxypropyl cellulose nanocomposite films. Nanofibril yields ranging from 11 to 98 wt% (on fiber weight basis) were obtained over the range of sonication times used. Suspension viscosities increased initially with sonication time, peaked with gel-like behavior at 10 min of sonication and then decreased with further sonication. The thermal degradation temperature of unfibrillated oxidized pulps was only minimally affected (6 °C decrease) by the fibrillation process. Dynamic mechanical analysis of the nanocomposites revealed strong fibril-matrix interactions as evidenced by remarkable storage modulus retention at high temperatures and a suppression of matrix glass transition at “high” (~5 wt%) nanofibril loadings. Creep properties likewise exhibited significant (order of magnitude) suppression of matrix flow at high temperatures. It was also believed, based on morphologies of freeze-fracture surfaces that the nanocomposites may be characterized by high fracture toughness. Direct fracture testing will however be necessary to verify this suspicion.

Renewable Polymeric Nanocomposite Synthesis Using Renewable Functionalized Soybean-Oil-Based Intercalant and Matrix

Completely bio-based and renewable polymeric nanocomposites have been prepared using an in situ polymerization technique in the presence of organically-modified montmorillonite (MMT) clays in different loading degrees. Acrylated epoxidized soybean oil (AESO) and styrene have been used as matrices, whereas modification of MMT has been done by using a new renewable soybean-oil-based intercalant, quarternized functionalized acrylated epoxidized soybean oil, which is the first renewable intercalant described in the literature. It was found that the above-mentioned intercalant could be successfully intercalated between the interlayer galleries of montmorillonite which is confirmed by X-ray diffraction (XRD) data and atomic force microscopy (AFM). The nanocomposite formation studies examined by both XRD and AFM showed that the desired exfoliated nanocomposite structures can be achieved with all nanofiller loadings. The resultant exfoliated nanocomposites were found to have significantly improved thermal stability and dynamic mechanical performance at very low loadings. The nanocomposites from both renewable intercalant and matrix offer a significant potential for new high-volume, low-cost applications.

Improvement in Food Packaging Industry with Biobased Nanocomposites

Nanotechnology will become one of the most powerful forces for innovation in the food packaging industry. One such innovation is biobased nanocomposite technology, which holds the key to future advances in flexible packaging. Biobased nanocomposites are produced from incorporation of nanoclay into biopolymers (or Edible films). Advantages of biobased nanocomposites are numerous and possibilities for application in the packaging industry are endless. A comprehensive review of biobased nanocomposite applications in food packaging industry should be necessary because nanotechnology is changing rapidly and the food packaging industry is facing new challenges. This provides a general review of previous works. Many of the works reported in the literature are focused on the production and the mechanical properties of the biobased nanocomposites. Little attention has been paid to gas permeability of biobased nanocomposites. In regard to extensive research on Edible film, this article suggests investigating the replacement of biobased nanocomposites instead of Edible films in different areas of food packaging.

Novel Biobased Nanocomposites from Soybean Oil and Functionalized Organoclay

Novel biobased nanocomposites have been prepared by the cationic polymerization of conjugated soybean oil (CSOY) or conjugated LoSatSoy oil (CLS) with styrene (ST) and divinylbenzene (DVB), and a reactive organomodified montmorillonite (VMMT) clay as a reinforcing phase. This filler has been prepared by the cationic exchange of sodium montmorillonite with (4-vinylbenzyl)triethylammonium chloride in aqueous solution. The nanostructures of the nanocomposites have been determined by using wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM), respectively. The results from WAXD and TEM indicate that a heterogeneous structure consisting of intercalation and partial exfoliation or an intercalation structure exists in the nanocomposites, depending on the amount of VMMT in the polymer matrix. The thermal, mechanical, and organic vapor barrier properties of the nanocomposites have been evaluated by dynamic thermal analysis, thermogravimetric analysis, mechanical testing, and toluene absorption. A significant improvement is observed in the thermal stability, the dynamic bending storage modulus, the compressive modulus, the compressive strength, the compressive strain at failure, and the vapor barrier performance for the CSOY-- and CLS-based nanocomposites with 1-2 wt % VMMT loading, where some individual exfoliated silicate platelets occur. For example, the CLS-based nanocomposite with 1-2 wt % VMMT exhibits increases of 100-128%, 86-92%, and 5-7% in compressive modulus, compressive strength, and compressive strain at failure, respectively. CLS with higher unsaturation and reactivity affords nanocomposites with higher thermal stability and higher mechanical properties than CSOY.

Recent Advances in Biodegradable Nanocomposites

There is growing interest in developing bio-based products and innovative process technologies that can reduce the dependence on fossil fuel and move to a sustainable materials basis. Biodegradable bio-based nanocomposites are the next generation of materials for the future. Renewable resource-based biodegradable polymers including cellulosic plastic (plastic made from wood), corn-derived plastics, and polyhydroxyalkanoates (plastics made from bacterial sources) are some of the potential biopolymers which, in combination with nanoclay reinforcement, can produce nanocomposites for a variety of applications. Nanocomposites of this category are expected to possess improved strength and stiffness with little sacrifice of toughness, reduced gas/water vapor permeability, a lower coefficient of thermal expansion, and an increased heat deflection temperature, opening an opportunity for the use of new, high performance, lightweight green nanocomposite materials to replace conventional petroleum-based composites. The present review addresses this green material, including its technical difficulties and their solutions.

Novel biobased nanocomposites from functionalized vegetable oil and organically-modified layered silicate clay

The new biobased nanocomposites are processed from anhydride-cured epoxidized linseed oil (ELO)/ or octyl epoxide linseedate (OEL)/diglycidyl ether of bisphenol F (DGEBF) epoxy matrix and organomontmorillonite clay. The selection of anhydride curing agent and biobased epoxy resulted in an excellent combination to provide an epoxy matrix having high elastic modulus, high glass transition temperature, and high heat distortion temperature (HDT), with higher amounts of functionalized vegetable oil (FVO), compared with amine-cured biobased epoxy. The sonication technique was utilized to process the organically-modified clay nanoplatelets in the glassy biobased epoxy network resulting in nanocomposites where the clay nanoplatelets are almost completely exfoliated and homogeneously dispersed in the epoxy network. The processed exfoliated clay nanocomposites showed higher storage modulus compared with the neat epoxy containing the same amount of FVO. Therefore, the lost storage modulus with larger amount of FVO can be regained with exfoliated clay nanoreinforcement.