Grantee Research Project Results
2005 Progress Report: Sustainable Biodegradable Green Nanocomposites From Bacterial Bioplastic For Automotive Applications
EPA Grant Number: R830904Title: Sustainable Biodegradable Green Nanocomposites From Bacterial Bioplastic For Automotive Applications
Investigators: Drzal, Lawrence T. , Mohanty, Amar K. , Misra, Manjusri
Institution: Michigan State University
EPA Project Officer: Aja, Hayley
Project Period: January 1, 2004 through December 31, 2006 (Extended to December 31, 2007)
Project Period Covered by this Report: January 1, 2004 through December 31, 2005
Project Amount: $369,613
RFA: Environmental Futures Research in Nanoscale Science Engineering and Technology (2002) RFA Text | Recipients Lists
Research Category: Nanotechnology , Safer Chemicals
Objective:
The objective of this research project is to replace/substitute existing petroleum derived polypropylene/thermoplastic olefin (TPO)-based nanocomposites with ecofriendly, biobased nanocomposites produced from compatibilized clay reinforced bacterial bioplastic (polyhydroxyalkanoate [PHA]) for automotive applications. The green nanocomposites that are the subject of this project are sustainable materials because they are: recyclable, stable in use but can be triggered to biodegrade under composting conditions, environmentally benign, and commercially viable. Compatibilization between the exfoliated clay and the bioplastic is the key to achieving success.
This project has a goal of synergistically combining green materials technology and nanotechnology to produce a new generation of sustainable materials for industrial applications that will have a positive impact on the environment. To achieve sustainability, this project integrates the environmental, economic, life-cycle analysis (LCA), energy, and education components critical to achieving sustainability.
In addition, we are investigating the concept of using ionic liquids as a plasticizer with poly (hydroxybutyrate) (PHB) biopolymer to explore a new route for processing nanocomposite bioplastic matrix materials. Ionic liquids are under intense investigation because of their potential of replacing volatile organic compounds in numerous types of applications; their nonvolatility, high thermal stability, nonflammability; and their potential to be varied structurally according to the task envisaged. The use of these environmentally friendly compounds in the field of green nanocomposites have not been reported yet, and our preliminary results constitute a starting point in the investigation of structure-properties relationship regarding ionic liquids and biopolymers. This portion of the research has the potential of replacing toxic and volatile compounds currently used as plasticizers for bacterial bioplastic polymers. Common plasticizers (e.g., esters of phthalic acid) currently are replaced by environmentally friendly citrates for the plasticization of PHB in our current project. Along with the citrate compounds that are under investigation in this project, we have considered the ionic liquids also as good candidates, especially considering the increased interest in this category of chemicals.
In addition to the study of new potential plasticizers for PHB, we addressed one of the main drawbacks of this polymer, its brittleness, by investigating the use of new expanded graphite nanoplatelets (xGnP) under development at Michigan State University as novel nucleating agents. xGnP-1 were under investigation in the view of producing high-performance electrically conductive bionanocomposites based on PHB. We also are investigating novel ecofriendly techniques for surface modification of the reinforcements. In general practice, these modifications by quaternary complexes are done using aromatic solvents that are toxic and environmentally persistent. We have addressed this problem by two techniques; one is by using an aliphatic solvent having similar characteristics as the aromatic solvent but significantly more environmentally benign and secondly by developing a solvent-less technique using ultrasonic atomization of the modifier directly onto the surface.
Progress Summary:
In Year 2 of the project, novel surface modifications of the clay reinforcement to achieve improved exfoliation/intercalation and matrix-clay compatibility were investigated. The fundamental scientific investigations on structure-property correlation of organoclay are quite valuable in understanding the interface chemistry to design and engineer the most effective polymer-clay nanocomposites systems. Organo alkyl-titanate derivatives were used as reagents for the surface modification of pristine montmorillonite clay platelets. This surface modification was validated through coordinated characterization techniques that include X-ray photoelectron spectroscopy (XPS), contact angle measurements, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). By fine-tuning the surface characteristics (controlling the hydrophilicity), effective nanodispersion in polymers by intercalation or delamination can be accomplished. The titanate-coupling agent increased the water contact angle of the clay from 6° to 44°, denoting significant decrease in hydrophilicity. Similarly, XRD studies revealed the increased intergallery spacing from 9.8 A to 12.7 A. The grafting of titanate modifier on to clay surface is quantified through XPS elemental analysis and co-related with TGA. This new surface-modification method provides an effective technique to convert the hydrophilic surface of the montmorillonite clay into organophillic for polymer-clay nanocomposites.
Optimization of the elastomer-toughened PHB materials included experiments on developing an effective vulcanization system. We investigated different vulcanizing systems (sulfur-based, N,N'-m-phenylene dimaleimide-based) and used dynamic vulcanization to cross-link optimally the elastomeric portion of the blend.
Another part of this project focused on finding a flexible partner for PHB, which will give synergistic properties sufficient for film applications. PHB was blended with a flexible petroleum-based biodegradable polymer (e.g., poly-(butylene adipate-co-terephthalate) [PBAT]) by twin-screw extrusion. PHB-PBAT blends of varying compositions were reinforced with organically modified montmorillonite clay. These blends and their nanocomposites were fabricated into films using a single screw extruder equipped with a blown film line. The blends and nanocomposites were characterized through thermophysical and mechanical analysis. This material combination is ideal for film making (requisite mechanical properties) and shows oxygen barrier between that of polyolefins and Nylon.
The investigation of ionic liquids as potential plasticizers for PHB continued, and, based on Hoffman-Weeks analysis, two imidazolium phosphates were found to be immiscible with PHB, thus inadequate as plasticizers. An environmentally friendly ionic liquid (1-Buthyl-4-methylimidazolium acetate) was further analyzed and proved to degrade PHB. Another important drawback of this polymer was addressed by searching for new nucleating/reinforcing agents. Saccharin was confirmed to act as nucleating agent for PHB, in the view of using it in PHB systems containing saccharinate-based ionic liquids. Expanded graphite nanoplatelets with average size of 1 μm (xGnP-1) were proved to act as efficient nucleating agents, as well as reinforcements. A detailed kinetic study of the nonisothermal crystallization, important in the view of optimizing processing conditions, was performed. The morphology of the resulted nanocomposites was studied by optical microscopy and atomic force microscopy. We concluded that PHB/xGnP-1 systems have the potential for developing new novel bionanocomposites with enhanced mechanical, thermal, and barrier properties, longer shelf life. This study continues and the goal is to obtain electrically conductive bionanocomposites based on xGnP-1 and PHA.
Future Activities:
Part I
Toughening of PHB with incorporation of elastomer and compatibilizer will continue in Year 3 to achieve still improved properties. We are planning on experiments on large-scale equipment to study the feasibility of commercial production. Based on the results obtained from the deep soil mixing (DSM) equipment, pilot scale compounding of PHB with clay nanoparticles and the compatibilizers will take place in a standard Werner & Pfleiderer ZSK 30 twin-screw extruder as well as a standard Brabender kinetic mixer. Also the pilot scale molding of the plastics and nanocomposites will take place in a Cincinnati Milacron Sentry 85 injection molder.
PHB-PBAT blending gave promising results and further studies targeting incompatibility issues are planned. PHB is incapable of forming commercial films because of its low percent elongation and poor melt strength. We hence intend to investigate different techniques for increasing elongation of unplasticized PHB like chain extension and reactive plasticization so as to fabricate films. These high elongation materials will be reinforced with organically modified nanoclays and fabricated into films by blown film or cast film extrusion. We intend to investigate the thermophysical, mechanical, and barrier properties of such films for commercial packaging applications.
Part II
We will continue to explore xGnP-1/PHB systems to determine the percolation threshold for electrical conductivity. A detailed study will be performed using atomic force microscopy and XRD to elucidate the nucleation mechanism of xGnP‑1 on PHB, as well as the changes in crystallinity and morphology of the resulted nanocomposites. The plasticization of PHB will be addressed further based on previous results obtained with ionic liquids, through the design of efficient surface treatment methods for the xGnP-1 using ILs. The resulted bionanocomposites also will be examined in terms of mechanical, thermal, and barrier properties.
We will continue to do research on the study of structure-properties relationship of ionic liquids with regard to nanocomposites. The plasticizing effects of several ionic liquids will be investigated and compared with the effects of commonly used plasticizers. This will be done by optimizing the processing of plasticized polymer samples, testing the thermal and mechanical properties of the obtained specimens, and characterizing the polymer-plasticizer interaction, as well as by studying the crystallinity and the morphology of the materials.
All the above blends and nanocomposites will be processed mainly using a DSM microextruder and injection molder (15 cm3 capacity); Werner-Pfleidderer ZSK 30 mm Twin Screw Extruder L/D 26:1; Killion blown film line (Killion, NJ) single screw extruder attached with a blown film die, 1’ screw diameter, 25:1 L/D (multiplayer and single layer); and Killion cast film line single screw extruder (Killion, NJ), 1’ screw diameter, 25:1 L/D attached with a cast blown film die with chill roll. Mechanical properties will be measured using United Test System and Testing Machines Inc., equipment, according to specified American Society for Testing and Materials (ASTM) standards. Thermal properties (differential scanning calorimetry, TGA, dynamic mechanical analysis, and thermomechanical analyzers) will be observed using TA Thermal Analysis equipment as per the ASTM standards. Polymer morphology and crystallization behavior will be observed using Olympus optical microscopes equipped with a hot stage (from Mettler Toledo). Fracture surfaces will be analyzed by environmental scanning electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Perkin-Elmer Spectrum 2000 Fourier transform infrared will be used for infrared characterizations of blends and nanocomposites. XRD by RIGAKU 200B (rotating anode) and Nanoscope I
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 30 publications | 3 publications in selected types | All 3 journal articles |
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Parulekar Y, Mohanty AK. Effect of titanate-based surface on hydrophilicity and interlayer spacing of montmorillonite clay for polymer nanocomposites. Journal of Nanoscience and Nanotechnology 2005;5(12):2138-2143. |
R830904 (2005) R830904 (2006) |
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Parulekar Y, Mohanty AK. Biodegradable toughened polymers from renewable resources:blends of polyhydroxybutyrate with epoxidized natural rubber and maleated polybutadiene. Green Chemistry 2006;8(2):206-213. |
R830904 (2005) R830904 (2006) |
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Supplemental Keywords:
green chemistry, material science, innovative technology, waste reduction, socio-economic transportation, eco-friendly materials, environmentally conscious manufacturing, life-cycle analysis, sustainable development, renewable,, RFA, Scientific Discipline, INTERNATIONAL COOPERATION, TREATMENT/CONTROL, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, Environmental Chemistry, Technology, Technology for Sustainable Environment, Chemistry and Materials Science, Chemicals Management, Environmental Engineering, biopolymers, energy conservation, biodegradable plastics, clean technologies, cleaner production, environmentally conscious manufacturing, green design, nanocomposite, air pollution control, automotive industry, environmental conscious construction, environmental sustainability, nanotechnology, biodegradeable nanocomposites, alternative materials, clean manufacturing, environmentally applicable nanoparticles, environmentally friendly green products, nanomaterials, environmentally benign alternative, nanoparticles, Design for Environment, polypropylene substitute, automotive interior parts, environmentally conscious designProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.