High performance biobased epoxy nanocomposite reinforced with

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High performance biobased epoxy nanocomposite reinforced with bacterial cellulose nanofiber network Liang Yue, Fei Liu, Shekar Mekala, Ammar Abbas Patel, Richard A Gross, and Ica Manas-Zloczower ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06073 • Publication Date (Web): 16 Jan 2019 Downloaded from http://pubs.acs.org on January 17, 2019

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ACS Sustainable Chemistry & Engineering

High performance biobased epoxy nanocomposite reinforced with bacterial cellulose nanofiber network Liang Yue,1 Fei Liu,2 Shekar Mekala, 2 Ammar Patel,1 Richard A. Gross2 and Ica Manas-Zloczower1* 1Department

of Macromolecular Science and Engineering, Case Western Reserve University, 2100 Adelbert

Road, Kent Hale Smith Bldg, Cleveland Ohio, 44106, United States 2Center

for Biotechnology and Interdisciplinary Studies (CBIS), Rensselaer Polytechnic Institute (RPI),

4005B BioTechnology Bldg, 110 Eighth Street, Troy, New York, 12180, United States *E-mail: [email protected]

Key Words: biobased epoxy, epoxy nanocomposites, bacterial cellulose, mechanical reinforcement

Abstract

This work describes the preparation and characterization of biobased fiber reinforced resins using bacterial cellulose (BC) as the matrix reinforcing phase and diglycidyl ether diphenolate ethyl ester (DGEDP-ethyl) as the biobased epoxy resin. BC mats were prepared by static cultivation of strain Gluconacetobacter xylinus ATCC 700178 in Hestrin-Schramm medium augmented with mannitol in sterile containers. After freeze drying, the surface of BC matrix fibers was modified to introduce trimethyl silyl moities (BCTMS). Reinforced by BCTMS nanofiber networks were fabricated by impregnation of BCTMS matrices with the resin mixture followed by hot-pressing and curing. Resulting DGEDP-ethyl/BCTMS composites with 5, 10, 20 and 30 %-by-vol BCTMS network loading were formed. The BC network proved effective in reinforcing the epoxy resin matrix.

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Composite Young`s modulus (ET) increased from 1.22±0.41 GPA for the neat DGEDPethyl thermoset to 8.8±0.98 for the composite with 30%-by-vol BCTMS. Furthermore, the storage modulus (Eʹ) increased for DGEDP-ethyl/30%BCTMS relative to the neat DGEDPethyl resin below Tg (30 oC) by 3 fold (2.27 to 7.7 GPA) and above Tg (180 oC) by 100 fold. This work highlights the potential to use prefabricated BC matrices produced by microbial fermentation along with a biobased epoxy resin to provide high-performance bio-based composites.

Introduction Epoxy resins are the most commonly used family of thermoset polymers. They function in a wide range of applications from coatings, adhesives to composite materials. These resins have high glass transition temperature, good chemical resistance, low density and high strength. Hence, they are the materials of choice for fiber reinforced lightweight structural composites, widely used in wind energy, automobile, and the aviation industry.1 Diglycidyl ether bis-phenol A (DGEBA), the most common constituent of epoxy resins, is synthesized from petroleum-derived building blocks. With the decreasing availability of petroleum resources and increasing environmental concerns related to petroleum use, there is an increasing demand for the development of alternative materials from readily renewable resources. Recently, our team reported a family of biobased epoxy resins, consisting of the diglycidyl ether of n-alkyl diphenolate esters (DGEDP), that have tunable molecular


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structures that give similar mechanical properties as DGEBA when cured with stoichiometric amounts of isophorone diamine.2 Since the chemical route to DGEDPesters simply substitutes acetone, used to produce DGEBA, with bio-levulinic acid, there is excellent potential to reach parity between the costs of DGEDP and DGEBA. This largely depends on success of ongoing efforts to develop a cost-effective route to levulinic acid from lignocellulose.3 In addition, we reported the vacuum infusion of E-glass fiberglass mats (75 wt%) with a mixture of 85 wt% of either ethyl or pentyl DGEDP-ester and 15 wt% of the biobased reactive diluent glycidyl eugenol (GE). The results of this work revealed that the physico-mechanical properties of the DGEDP-ester/GE fiberglass reinforced system are similar and sometimes exceeded that of two DGEBA formulations.4 To further increase the sustainability of DGEBA fiber reinforced composites, we describe herein the use of a biobased reinforcing material. Nanocellulose, in the form of highly crystalized nanoparticles or nanofibers, can be isolated from various renewable sources, including wood, cotton, ramie fibers, and some marine animals or produced through bacterial culture. Since the theoretical Young`s modulus for perfectly crystalized nanocellulose is 167.5 GPa,5 this makes cellulose an attractive biobased candidate for polymer composite reinforcement. A problem in fabricating nanocellulose reinforced polymer composites is dispersion. Nanocellulose tends to aggregate at high volume fractions which makes it difficult to process. An approach of achieving high volume fractions of filler in the composite is by solvent exchange.6 However, at high filler volume fractions, the nanocellulose and resin mixture becomes a paste, which is very difficult to cast.



Furthermore, solvent exchange is a tedious process that uses organic solvents rendering it unattractive for commercial processes. Bacterial cellulose (BC) is an attractive alternative to plant-derived nanocellulose since it is formed by bacteria as a 3D nanostructured pre-percolated network structure .7 Hence, BC can provide high filler volume fractions while avoiding dispersion problems. BC nanofibers, with an experimental Young`s modulus of 78 GPa, are superior to the traditionally used E-glass fibers in accelerate the hydrolysis of matrix ester bonds composites.8 Moreover, the BC density (1.25 g/cm3) is only half of the value for glass fibers (2.5 g/cm3).9 BC has been previously used as nanofiller to reinforce the mechanical properties of epoxy composites. BC nanofiber was mechanically break down into small fibers to disperse in epoxy matrix.10,11,12 Another method was to prepare nanopaper with BC mat first, and then laminate with epoxy resin to fabricate the composites.13,14,15,16,17 Both methods successfully incorporated the BC with epoxy matrix and achieved increased mechanical performance. However, the naturally percolated 3-D network structure of BC mat was not utilized. Here, we report the fabrication and characterization of potentially fully biobased fiber reinforced epoxy resins where the fiber phase consists of an interconnected 3-D matrix of cellulose constructed during the growth of a bacterium. This BC matrix was modified with with trimethylsilyl chloride (TMSCl) to give trimethyl silyl surface modified matrices (BCTMS) that was used to facilitate resin infusion and decrease reactions with the anhydride crosslinking agents. The fabricated composites with up to 30 %-by-wt BCTMS were studied by tensile testing, dynamic mechanical analysis, differential scanning


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calorimetry and thermogravimetric. The results of this work show an excellent potential for use of BC as a matrix material for advanced composite materials.

Materials and Experimental Sections Materials Biobased epoxy resin DGEDP-ethyl (diglycidyl ether of diphenolate ethyl ester) was synthesized as previously reported.2 Hexahydro-4-methylphthalic anhydride (MHHPA), 1methylimidazole (1-MI) and chlorotrimethyl silane (TMSCl) (≥99%) were purchased from Sigma Aldrich, trimethylamine (≥99.5%) was purchased from EMD Millipore Corporation, Koptec Pure Ethanol-200 Proof was purchased from Decon Labs, Inc., and dichloromethane was purchased from Macron Fine Chemicals (dried over 4Å MS for 24 h prior to use). All reagents and solvents were used as received without further purification and deionized water was used in all experiments. Biosynthesis of Bacterial Cellulose mats Bacterial cellulose mat was produced by cultivation of strain G. xylinus ATCC 700178 in Hestrin-Schramm medium (HS medium) (0.5% peptone, 0.5% yeast extract, 0.12% citric acid)18,19 and 4.0% mannitol. Culture pH was adjusted to 5.0 using acetic acid. Medium components and culture containers were autoclaved at 121°C for 15 min. Mannitol was autoclaved separately. G. xylinus stock culture was prepared from 5-day grown culture. In each vial, 1 mL aliquots of culture were mixed with 1mL 40% sterile glycerol, and kept at -80°C. The cell activation culture was prepared using the full content of a glycerol stock tube to incubate 50-mL fresh HS-medium and 2.0% mannitol in a 250-mL Erlenmeyer flask that was incubated statically at 30°C for 5 days. To prepare the seed culture, 10 mL



of supernatant from the activation culture was inoculated into 90 mL HS medium with 2% mannitol in 500 mL Erlenmeyer flasks. The flask was incubated statically at 30°C for 5 days. BC-mats were produced in sterile containers (30cm x 15cm) filled with 800 mL HS medium in the presence of 4% mannitol. Each container was inoculated with 10 vol% seedculture broth and then incubated statically at 30°C for 3 weeks. For the removal of microorganism and remaining culture medium, the harvested BC membrane was repeatedly rinsed in 0.5M NaOH for 2 days, washed under distilled water for two days, cut into small pieces （5cm x10cm）and freeze-dried. Synthesis of BC mats modified at fiber surfaces with trimethylsilyl groups (BCTMS) The BC mats were modified with trimethylsilyl chloride (TMSCl) following literature procedures.20,21 To a 500 mL round bottomed flask equipped with a magnetic stirrer, 200 mL dichloromethane and 4.8 mL trimethylamine were added and stirred for 10 min. Subsequently, 6.0 mL TMSCl was added and stirred for another 10 min followed by the addition of bacterial cellulose mats (10cm x 5cm x 0.4cm). Then, the flask was attached to a water condenser, a Ar inlet, and refluxed at 60 oC for about 4 h. Afterward, the reaction flask was cooled to room temperature and the reaction mixture was quenched by addition of small amounts of EtOH. Subsequently the liquids were decanted, the BC mats were transferred into a beaker with EtOH (100 mL) and washed 3 times (3x100 mL ethanol, solvent changed every 30 min). Thereafter, the mats were washed with DI water (3x100 mL) and freeze dried for 48 h. The surface modification of BC mats was determined using energy-dispersive X-ray spectroscopy. Analysis of %-crystallinity of modified BC mats was determined by wide-angle X-ray diffraction (Supporting Information).


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DGEDP-ethyl/BCTMS mat composites preparation Hexahydro-4-methylphthalic anhydride (MHHPA), was used as the curing agent and 1methylimidazole (1-MI) as the curing agent catalyst. First, 1 equivalent of DGEDP-ethyl ester resin was thoroughly mixed with 2 equivalents of MHHPA and 1 phr of the accelerator 1-MI. Pre-weighted BCTMS mats were immersed in the resin mixture. This mixture was placed in a vacuum oven at room temperature for 8h to ensure that resin infusion into porous BCTMS was complete. The DGEDP-ethyl/BCTMS gel was placed between Teflon sheets in a hot press at 80oC. In order to control BC loading in the final composite, very slight pressure (less than 0.1 ton) was applied to squeeze out excess liquid resin mixture from the BCTMS network. Afterwards, composites were cured at 80 oC for 4h followed by a post-cure at 160 oC for another 4h. Composites were prepared with loading of BCTMS fiber matrices of 5, 10, 20, and 30 %-by-vol. Characterizations Dynamic Mechanical Analysis (DMA): TA Instruments Q800, operating in tensile mode with a constant frequency of 1 Hz, strain amplitude of 0.05%, was used to determine the storage modulus (Eʹ) and glass transition temperature (Tg) (determined from the peak of tan ) by scanning at 5 °C/min from 0 °C to 200 °C. Samples were prepared by cutting films strips with a width of 5mm. Differential Scanning Calorimetry (DSC): DSC measurements were performed by using a DSC Q100 differential scanning calorimeter from TA Instruments with Tzero aluminum pans. Each sample was heated from 0 to 200 °C at a heating rate of 5 °C/min under constant nitrogen flow. The glass transition temperature, Tg, was taken as the midpoint of the drop in heat capacity during the heating cycle.



Tensile Test: The test was conducted with a Zwick-Roell tensile Instron 1011 universal tensile machine with a test speed of 50mm/min. Five specimens were tested for each sample. Thermogravimetric Analysis (TGA): The thermal stability of the prepared resins was studied by TGA using a TA Instruments Q500 with an aluminum pan. The samples were about 10 mg each and were exposed from room temperature to 600 °C at a heating rate of 10 °C per minute under constant N2 flow. Scanning Electron Microscopy (SEM). SEM images were obtained using a Carl Zeiss 1540EsB Crossbeam instrument. BCTMS mats were sputtered with platinum prior to imaging. Energy-Dispersive X-ray Spectroscopy (EDS or EDX). The elemental compositions of unmodified and modified BC mats were determined by EDX spectra with the same test conditions as for SEM and the accelerating voltage was at 5 keV. Wide Angle X-ray Scattering (WAXS). Spectra were recorded with a Bruker D8Discover X-ray spectrometer equipped with a NaI dynamic scintillation detector. The samples were scanned from 10 to 40 degrees of 2 (scattering angle), at 40 kV and 40 mA. Results and Discussion The freeze dried BC and BCTMS mat were analyzed by wide-angle X-ray diffraction and the degree of crystallinity, calculated by the Segal equation (Ic= [(I002Iamorphous)/Iamorphous]*100), is 92% (Supporting Information).22 SEM analysis reveals that the BCTMS mat consists of ~70 nm fiber diameter that are entangled forming a 3D-continous nanoporous matrix (Figure 1).


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Figure 1 SEM of freeze dried BCTMS mat

The BC mats were modified to introduce trimethylsilyl groups at fiber surfaces. These mats, referred hereafter as BCTMS, were used instead of neat BC in order to increase the affinity of the infused hydrophobic matrix components for the BCTMS fibers (Figure S2). Furthermore, BCTMS, relative to neat BC, should decrease the frequency of reactions between BC hydroxyl groups and methylphthalic anhydride (MHHPA) that would create an imbalance in reactant stoichiometry.

Also, decreasing the composite fiber

hydrophilicity will decrease its tendency to absorb water which could accelerate the hydrolysis of matrix ester bonds.

Structures of native cellulose chains in BC mats and corresponding BCTMS formed by reaction with trimethylsilyl chloride are given in Supporting Information. While modification is shown at primary hydroxyls, the distribution of trimethyl silyl groups is



likely random such that they reside at both primary and secondary hydroxyl groups of glucopyranose rings. To determine the extent of BC trimethylsilylation, EDS spectra were performed. Values of carbon and oxygen for the BC mat prior to and after modification with TMSCl are given in Supporting Information. The calculated average degree of substitution (DSavg i.e. a value of 1 means each glucose unit has on average 1 site of modification), calculated by a literature method,20 is 0.039. Based on theoretical calculations by Fumagalli et al.21 modifications are restricted to the fiber surfaces for DSavg ≤ 0.4. This is consistent with the high degree of BC fiber crystallinity (92%, see Supporting Information) that substantially reduces the rate at which reactants diffuse into fibers. Furthermore, the %-crystallinity values are unchanged after BC trimethylsilyation. This is consistent with surface modification since, modification throughout BC should decrease BC’s crystallinity. Consequently, even though the DSavg is low, functionalization is concentrated at the surface. This can potentially result in the desired decrease in surface hydroxyl group accessibility and, therefore, reduced water affinity and reactivity of matrix fibers with MHHPA. The diglycidyl ether of diphenolate esters (DGEDP) was cured with MHHPA and 1-methylimidazole (1-MI) was the curing agent catalyst. The reaction at room temperature is extremely slow such that the mixture remains as a flowable liquid for more than 48h. This provides ample to complete the infusion of BCTMS mats. Figure 2 describes the twostep processing of the composite preparation. Resin infusion was performed in a vacuum oven at room temperature for 8h. After full infusion, the BCTMS mats become transparent without any trapped air. Composite cure was at 80 oC for 4h followed by a 4h post-cure


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at 160 oC. Composites with 5, 10, 20 and 30 %-by-vol BCTMS network loading were prepared.

Figure 2. Two-step preparation of epoxy/BCTMS composites

Tensile Properties of DGEDP-ethyl/BCTMS mats composites Mechanical properties of neat DGEDP-ethyl, DGEDP-ethyl/ BCTMS and a neat BC room-temperature dried film were evaluated using the uniaxial tensile test. Young's modulus, tensile strength and the elongation at break of DGEDP-ethyl/BCTMS composites and a neat BC film are given in Figure 3. All composites show an increase in Young’s modulus and tensile strength by comparison with the neat resin with dramatically lower elongation at break values. The composites reinforced with 30 vol% BCTMS show more than a 7-fold increase in Young’s modulus (8.8 versus 1.22 GPa) and about a 35% increase in tensile strength (84 versus 60 MPa) relative to neat DGEDP-ethyl ester. BC films used in composites were prepared by freeze drying. This is important since freeze drying



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provides a more open network structure with larger pores whereas BC gels dried under heat and pressure have relatively lower porosity but better mechanical properties.23,24

Figure 3. Tensile properties of neat DGEDP-ethyl, BC film and DGEDP-ethyl/BCTMS composites with different BC volume fractions. Water removal for neat BC films was by room temperature drying.

The Young`s modulus of randomly oriented fiber composites can be modeled using the Cox-Krenchel model, developed based on the classical shear-lag theory.25,26 Based on this model, the Young’s modulus of the composite, Ecomposite, can be calculated as: Ecomposite= η0ηLvfEf + (1-vf)Em

Eq.1

where Ef is the fiber modulus, Em is the matrix modulus, η0 and ηL are efficiency factors corresponding to fiber orientation and length, respectively, and vf is the fiber volume fraction. Here, Em=1.22 GPa as measured in the tensile test, and Ef =78±17 GPa as measured by Guhados et al. by atomic force microscopy.8 The orientation factor of BC fibers (η0) can be considered as the value of in-plane isotropic orientation (0.375). Considering BC to be a percolated network formed by continuous fibers, the length efficiency of the BC fibers is assumed to be unity. The Cox-Krenchel model is plotted as


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the black line in Figure 4. The results suggest Cox-Krenchel model could provide accurate predictions within the test BCTMS loading range.

Figure 4 Young`s modulus of the composites as a function of BCTMS volume fraction.

Thermo- Mechanical Properties of DGEDP-ethyl/ BCTMS mats composites The thermo-mechanical properties of DGEDP-ethyl/BCTMS biobased composites were investigated by dynamic mechanical analysis (DMA). Figure 5 shows the storage modulus, Eʹ, of composites with different BCTMS loadings as a function of temperature while Table 1 lists corresponding Eʹ values at 30 and 180oC. The biobased matrix DGEDPethyl displays typical behavior for an amorphous thermoset polymer. At temperatures below Tg, Eʹ decreases slightly with increasing temperature. However, above Tg, a large decrease in Eʹ occurs. A clear trend of increasing Eʹ with increasing BCTMS loading was observed (Table 1). At 30 oC, Eʹ increased more than 3 times, from 2.27 GPa for neat DGEDP-ethyl to 7.7 GPa for the 30 vol% BCTMS composite. Above Tg, the reinforcement



is more pronounced. For example, at 180 oC, the storage modulus of the 30 vol% BCTMS composite is 100 fold higher than neat DGEBA (0.024 and 2.47 GPa, respectively). Improvements in Eʹ as well as in tensile properties is attributed to formation of a percolated network of high crystallinity rigid BC fibers as well as favorable interfacial interactions between BCTMS and DGEDP-ethyl. Especially at high temperatures, when the polymer matrix loses most of its mechanical properties, the percolated BC network dominates the mechanical performance of the composites. For comparison, the properties of plant-derived nanocellulose reinforced/epoxy composites is discussed below. A general feature of these studies is that, similar to this work, the modulus increases with higher nanocellulose loadings.26 A key challenge faced in these studies is that, with increasing nanocellulose loadings, processing difficulties were encountered due to high viscosities.27 Also, at higher nanocellulose loadings nanocellulose agglomeration is observed.27 Most often, nanocellulose/epoxy nanocomposites were fabricated by mechanically dispersing the nanocellulose within the resin. The loadings were usually low (less than 20wt%), due to the high viscosities encountered. These nanocellulose/epoxy composites typically have modulus values below 5GPa (See Table S1, Supporting Information). Tang et al. fabricated a cellulose nanowhisker/epoxy composites with a maximum loading of 24vol% using a solvent exchange method, which avoided the viscosity problem and reached a storage modulus of 4.7 GPa.28 Another method to fabricate nanocellulose/epoxy composites with high cellulose loadings is to first prepare nanocellulose paper and then impregnate the paper with epoxy resin. Shimazaki et al. prepared epoxy composites with up to 58wt% of nanocellulose sheets from vacuum filtration of a nanocellulose aqueous suspension. The resulting nanocomposites have


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storage modulus values up to 5.0 GPa relative to 3.7 GPa for the non-reinforced matrix.29 Using the same method, Lee et al. reported BC/epoxy composites with loadings up to 49 vol% and tensile modulus and strength 7.1GPa and 102 MPa, respectively.17 Review of a broad range of nanocellulose/polymer composites with up to 30 vol% nanocellulose finds that the tensile modulus and strength rarely exceeded 5 GPa and 100MPa, respectively.26

Figure 5. Storage modulus as function of temperature for neat DGEDP-ethyl, BC film and corresponding BCTMS composites (left). Tan() as a function of temperature for neat DGEDP-ethyl and corresponding BCTMS composites (right).

Figure 5 displays plots of tan  versus temperature for neat DGEDP-ethyl and the BCTMS reinforced composites from which Tg values were obtained (Table 1). A small increase in Tg relative to the neat DGEDP-ethyl resin (152.2 to 157.7 oC) results by incorporating 5 vol% BCTMS in the composite. However, further increases in the BCTMS volume fraction results in decreased composite Tg values. The Tg data obtained from DSC (Figure 6 and Table 1) exhibit a similar trend. Analogous phenomena of changes in Tg for epoxy/cellulose nanocrystal composites were reported previously. Tang8, Omrani23 and Saba24 reported that, in epoxy/cellulose nanocrystal systems, Tg increases slightly at low filler concentration and



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decreases at higher filler concentration. Mathew25 reported that, in tunicate cellulose nanowhisker reinforced sorbitol plasticized starch nanocomposites, the Tg slightly increases at low filler concentration but decreases at higher loadings.5 Most literature reports

do

not

describe

improvements

in

Tg

for

nanocellulose

polymer

composites.31,32,33,34,35,36,37,38,39,40 Hence, the results obtained herein agree with these literature reports.

Figure 6. DSC thermograms as a function of temperature for neat DGEDP-ethyl and corresponding BCTMS composites.

Thermal stability of DGEDP-ethyl, BC and their composites was studied by thermal gravimetric analysis (TGA). Decomposition of DGEDP-ethyl occurs between 350


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and 500 oC, whereas the degradation of BC is in a lower temperature range between 300 to 400 oC. From these results it would be expected that decomposition temperatures of DGEDP-ethyl/BCTMS composites will lie between neat DGEDP-ethyl and BC. The results shown in Figure 7 confirm this hypothesis. The temperature at the maximum weight loss rate (Tdmax), which is determined from the 1st derivative peak temperature (Tp), slightly decrease as BCTMS loading increases from 5 to 30 vol%, however, differences in values between these composites are small. For example, Tdmax values for 5 vol% and 30 vol% composites are 427.9 and 420.2 oC, respectively (Table 1).

Figure 7. TGA curves of DGEDP-ethyl, BCTMS and the composites

Table 1. Mechanical and thermal properties of neat DGEDP-ethyl, neat BC and the corresponding composites with different BC loadings.

DGEDPethyl

ET a GPa

E30 b GPa

E180 b GPa

Tg DMA oC

Tg DSC oC

Tdmax oC

1.22±0.41

2.27

0.024

152.2

136.5

425.1


c


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BC film

16.4±0.84

15.80

15.6

\

\

378.4

5 vol%

2.5±0.42

2.96

0.21

157.7

138.6

427.9

10 vol%

3.9±0.53

3.94

0.45

144.9

128.9

425.2

20 vol%

7.2±0.71

6.33

1.72

143.8

127.2

424.4

30 vol%

8.8±0.98

7.70

2.47

141.9

123.3

420.2

a) ET is the modulus obtained from tensile test b) E30 and E180 are the storage moduli obtained from DMA at 30 oC and 180 oC, respectively. c) Tdmax is determined from TGA

Conclusions This work demonstrated that impregnation of a pre-percolated BCTMS network with the biobased epoxy resin (DGEDP-ethyl ester) followed by hot-pressing and curing provides a viable manufacturing route that avoids problems encountered when using plant-derived nanocellulose fiber reinforcement such as fiber agglomeration and high viscosities of epoxy resin/nanocellulose suspensions. Loading of 30 vol% pre-percolated BCTMS were easily attained. Analysis of the physical-mechanical properties of pre-percolated BCTMS/ DGEDP-ethyl ester cured epoxy composites revealed that high modulus/low density composites were prepared that are suitable for applications in the automotive and transportation industry or as construction materials. In addition, biobased BCTMS/DGEDP-


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ethyl ester cured epoxy composites have good transparency and thermal stability, features that are important to their potential use in the optoelectronics industry. Supporting Information Picture of BC mat and bio-based epoxy/BCTMS composite, scheme of BC surface modification, EDS and XRD of BC and BCTMS, summary of mechanical properties of nanocellulose/epoxy composites Author Information Corresponding Author E-mail: [email protected] (Ica Manas-Zloczower) The authors declare no competing financial interest. Acknowledgements The authors are grateful for funding received from the National Science Foundation Partnerships for International Research and Education (PIRE) Program (Award #1243313).

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Fully renewable high performance composite materials fabricated with bio-based epoxy resin and pre-percolated bacterial cellulose network


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High performance biobased epoxy nanocomposite reinforced with

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