Performing Department
(N/A)
Non Technical Summary
Plastic manufacture and incineration are a significant contributor to global greenhouse gas emissions (up to 13%). Further, the accumulation of non-biodegradable plastics in waterways and oceans is a growing problem. This project aims to replace large-volume petrochemical plastics, such as polyethylene and polypropylene, with a family of renewable and biodegradable bioplastics with equal or better performance at an equal or lesser cost than existing petrochemical alternatives. These bioplastics will have an estimated 75% lower carbon footprint and a benign end of life, whether they are collected and up-cycled to new products or accidentally dispersed into the environment and degrade to natural molecules.
Animal Health Component
45%
Research Effort Categories
Basic
10%
Applied
45%
Developmental
45%
Goals / Objectives
Plastic manufacture and incineration are a significant contributor to global greenhouse gas emissions (up to 13%). Further, the accumulation of non-biodegradable plastics in waterways and oceans is a growing problem. This project aims to replace large-volume petrochemical plastics, such as polyethylene and polypropylene, with a family of renewable and biodegradable bioplastics with equal or better performance at an equal or lesser cost than existing petrochemical alternatives. These bioplastics will have an estimated 75% lower carbon footprint and a benign end of life, whether they are collected and up-cycled to new products or accidentally dispersed into the environment and degrade to natural molecules. Sust-Chem's renewable thermoplastics are made of the polyacetal poly(2,5-dihydroxy-1,4-dioxane), a.k.a. PDHDO. PDHDO can be obtained by the condensation of glycolaldehyde dimer, also known as 2,5-dihydroxy-1,4-dioxane, DHDO. In prior work we developed a process of making our bioplastic via catalysis by a Lewis acid and repeated the process an multigram scale with laboratory equipment. We demonstrated the product had properties similar to low density polyethylene.The objective of this USDA Phase I project is to increase the molecular weight of the product and develop a scalable, reproducible, and cost-effective process to manufacture our bioplastic at scale. Further we want to demonstrate processing in thin film form with commercial equipment. A successful project will demonstrate the commercial manufacturability of our bioplastic and use in thin film applications for bags and packaging.The overall technical objective of this USDA project is to demonstrate that PDHDO can be used as an LDPE replacement in thin film applications. Technical objective of this Phase I project include:1. Improve the polymerization process to reach a polymer with molecular weight of 30,000-50,000 Dalton which it the molecular weight of LDPE for film applications. Scale up production to kilograms quantities2. Demonstrate thin film processing using available commercial equipment. We plan to evaluate several methods to process PDHDO in thin film forms with existing industrial equipment.3. Characterize the properties of the thin film and begin identifying initial target applications and compare to the properties of the status quo material. Key performance metrics will include water absorption, and tensile and tear strength in thin film form.4. Carry out an engineering, cost and lifecycle analysis to demonstrate economic viability, and estimate the environmental impact and confirm the GHG reduction potential of our bioplastic. This analysis will include of the monomer (GA), dimer (DHDO) and polymer (PDHDO).
Project Methods
G.1. Task 1. Optimization of catalytic process In this Phase I project we will use raw material (GA and DHDO) sourced from Topsoe, which will provide samples at no cost to the project. Our goal is to optimize our catalytic process for the synthesis of PDHDO. The focus of this task is on improving the synthesis to increase the molecular weight (MW) of the product targeting a product with MW in the range of 30,000 - 50,000 Dalton. With higher MW, we expect the polymer to have improved mechanical properties such as tensile strength, tear strength and thermal resistance. In our prior work, we used a commercial grade of DHDO with purity of 95%. In this work we will use DHDO obtained from Topsoe which has very high purity (>99.5%) and high crystallinity. Monomer purity is very important to obtain high MW polymers since monomer impurities may cause chain termination. In fact, improving monomer purity from 95% to 99.5% can, in principle, increase the molecular weight by a 10X factor (Zang 2016).Our prior work showed that scandium triflate was a good catalyst for the polymerization of DHDO. In this project we will explore other Lewis acid catalysts including boron trifluoride and lanthanum, yttrium and ytterbium salts. We will also look at additional polymerization solvents to avoid the polymer chains crashing out of solution as their MW increases. This may require a slow switch from a polar solvent at the beginning of the polymerization reaction where the monomer (a polar molecule) is the predominant species to a less polar solvent at the end when polymer chains of increasing MW are formed.We will also explore methods to obtain longer chain polymers with enhanced performance characteristics by carrying out the reaction in two steps, where in the first step we build a pre-polymer as described above and in the second step we couple these pre-polymeric chains to form a high MW product using specific coupling reagents. This two-step approach is actually used in industry to manufacture other condensation polymers such as poly(ethylene terephthalate) (PET) and polyoxymethylene (POM). Finally we will investigate solventless polymerization in the molten state to promote chain growth after the initial pre-polymerization step. This process is also used to manufacture POM of high MW.Another objective of Task 1 is to investigate ways of removing water from the reaction without using vacuum. Because the polymerization of DHDO is a dehydration reaction, the process improves if the water byproduct is removed quickly. There are many ways of removing water, including using toluene as cosolvent to form an azeotrope or refluxing trough molecular sieves or P2O5 or by using specific selective membranes.Intermediates and polymers prepared in Task 1 will be purified according to standard organic chemistry protocols and the chemical structures and molecular weights of our products will be determined by 1H and 13C-NMR, elemental analysis, and GPC using the service of outside analytical laboratories (Colorado School of Mines, NMR facility; Huffman Laboratories, Golden, CO; and Scientific Polymer Products, Inc, Ontario, NY, respectively). At the end of Task 1 we will select one or more of the best polymerization methods and produce a sufficient amount (kilograms) for the processing trials of Task 2.G.2. Task 2. Evaluation of processability to make thin filmsIn Task 2 we will evaluate various processes to transform PDHDO into thin film forms. Casting from solutions will be our first approach to prepare specimens. This will give us a preliminary idea of the film properties, although we are aware that this is not a process of commercial interest. We will then evaluate whether our polymers can undergo melt processing. We will measure the viscosity of the molten state and the polymer stability when in the molten state. We will then carry out preliminary trials to evaluate processing from the molten state including preparation of films by hot press (available at Sust-Chem). We will then send a batch of PDHDO pellets to Automated Manufacturing System (AMS, West Palm Beach, FL - https://ams-plasticextrusions.com/pages/ams-lab-testing). AMS offers R&D plastic extrusion trial services to customers that want to attempt processing of new polymers on their equipment. AMS has several extrusion lines, including a 3D Filament Extrusion Line with 1.5" Extruder, a 2 Roll Cast Film System with Dual Payoffs and Winder System & 1" Extruder, a Blown Film Tower with 1" Extruder, and a 3.5" Extruder. The facility has a cost of $1,200/day and we have budgeted four days for this Phase I proposal. The budget also includes a two-day trip of the PI to Palm Beach, FL to oversee the processing trials. A successful Task 2 will lead to the manufacture of several PDHDO film prototypes of various thicknesses. At the end of Task 2 we will select one or two best performing film prototypes for the testing in Task 3.G.3. Task 3. Characterization of polymer filmsThe objective of Task 3 is to characterize the physical-mechanical properties of PDHDO in thin film form and determine whether it is a suitable candidate for LDPE replacement in packaging applications. We also want to demonstrate enzymatic degradation.Thermal Properties. Glass transitions and melting points will be measured by Differential Scanning Calorimetry (DSC). The thermal stability will be assessed by Thermal Gravimetric Analysis (TGA) at MSE supplies LLC, Tucson AZ.Mechanical properties. The tensile and tear strength properties (modulus and ultimate strength) will be measured according to ASTM D638 (tensile) and ASTM D1922 (tear) at ARDL, Akron OH. The mechanical properties of our materials will be compared to those of current renewable and petroleum-based film polymers.Barrier properties. Permeability of water vapor will be measured using a gravimetric method in house per ASTM D570 and compared to those of thin films of LDPE of comparable thickness. TheOxygen Transmission Rate(OTR) will be measured via ASTM D3985 at Inertek, Louisville CO.Degradation. Hydrolytic degradation will be measured by recording the weight loss of samples versus immersion time in various buffered solutions at different pH. Due to Phase I budget and time limitation, biodegradability testing against ASTM D6691 (aerobic in marine environment), ASTM D5338 (aerobic in soil), and ASTM D5511 (anerobic in soil) will be studied in Phase IIResults from Tasks 3 will be used to identify promising applications for first market entry and to attract potential end users and customers.G.4. Task 4. Lifecycle and technoeconomic analysisIn Task 4 Sust-Chem and its partners will carry out preliminary analyses to evaluate the economic feasibility and potential environmental impact of PDHDO at scale. We will begin with analysis of the production of GA from biomass-derived glucose, followed by formation of the GA dimer and the subsequent polymerization process. For the economics of the production of GA and DHDO we will work in close collaboration with Topsoe. For an estimate of the cost of the polymerization step we will rely on published literature and consult with our collaborators at NREL who has extensive modelling capabilities. Given the funding, these efforts will be preliminary in Phase I, but will expand in Phase II to provide more rigorous TEA and LCA analyses. The data produced in this Phase I effort is essential to putting Sust-Chem's technology into perspective, in terms of both economic competitiveness as well as in quantifying GHG emissions. Opportunities for cost reduction and further lowering the carbon intensity of this process (compared to the incumbent production method for polyethylene) will be delineated in the Phase I work.