Grantee Research Project Results
Final Report: Adding Glycerine to Eco-Friendly Golf Tees to Accelerate Biodegradability and Improve Fabrication
EPA Grant Number: SU834736Title: Adding Glycerine to Eco-Friendly Golf Tees to Accelerate Biodegradability and Improve Fabrication
Investigators: Tatara, Robert A. , Clarizio, Stephen , Ryan, Corey , Shanafield, John
Institution: Northern Illinois University
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $9,860
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Chemical Safety , P3 Awards , Sustainable and Healthy Communities
Objective:
The overall purpose of the proposed study was to formulate a novel biomaterial using corn processing and biodiesel coproducts, DDGS and glycerine, respectively. This project enhances sustainability by providing alternative, higher value utilization for agricultural coproducts. This bio-based material is less costly than current biodegradable resins. Additionally, it can reduce the amount of resin manufactured from petroleum raw materials in plastic products. Thus green plastics are more competitive; the planet’s oil reserves are conserved; and the amount of plastic disposed of, at the end of a product’s useful life, is reduced. An additional benefit of such a biofilled material is to increase the rate of biodegradability of the plastic with the potential of creating a greener one. Overall, this work impacts sustainability on a global level by minimizing the environmental impact of plastic products while lowering costs and conserving non-renewable resources. Specifically, one goal was to create a commercially viable golf tee. Tees and blends were mechanically evaluated: tensile strength, material stiffness, ductility, hardness, and toughness.
PLA and corn-starch are two commercially-available green resins having thermoplastic processing characteristics. Glycerine is an accepted plasticizing agent already in use with conventional resins. DDGS has been employed as filler in combination with various resins. Generally, fillers may improve the plastic material’s overall properties but, in some cases, may actually slightly degrade some mechanical properties, such as tensile strength and ductility. Selection of an appropriate filler is based upon cost, availability, compatibility with the resin, effects on product properties, abrasiveness, effect on processing, moisture absorption, and other factors. Fillers are typically added in concentrations ranging from 10% to 50% (by weight).
Summary/Accomplishments (Outputs/Outcomes):
The polylactic acid (PLA), a biodegradable and biocompatible polymer resin that is commercially available, was mixed by weight with distillers dried grains with solubles (DDGS) and glycerine by the project partner, United States Department of Agriculture (USDA) through its Northern Grains Insects Research Laboratory (NGIRL) in Brookings, South Dakota. The mixing occurred at low shear with a room temperature tumbling action to preserve the DDGS fibers integrity while allowing the glycerine to be absorbed by the DDGS. Blend compositions were selected based on a DOE (Design of Experiment) approach. DDGS content was 0, 20, 50, and 80% while glycerine content was 0, 5, 10, and 15%; the remainder 10 to 80% was PLA. This results in 4 x 3 x 2 = 24 treatment combinations, each injection molded 3 times (three replicates at each condition), for a total of 72 runs. Each blend was prepared as a 2-pound batch to mold tensile bars and golf tees. The DDGS was in its raw, flaked form, then fractionated at NGIRL to remove the high-value components, such as protein and fat, and to concentrate the high-fiber component. The flaked DDGS is coarse with larger particle size and is the natural state when produced in an ethanol plant. Glycerine was obtained from a commercial biodiesel facility.
Figure E.1 presents the ultimate tensile strength for the DDGS/glycerine/PLA material. Also available in this figure are results from a previous biomaterial/golf tee project utilizing a corn-starch instead of PLA as the resin (“Eco-Friendly Golf Tees Filled with Corn-Based DDGS,” EPA P3 Project Final Report, March 31, 2008). The results indicate that substitution of PLA for the corn-starch increased strength or maintained strength at a lower concentration of resin. For example, the 20/15/65 PLA blend exceeded the tensile strength of the previous pure starch case. This amounts to replacing 1/3 of the resin with biofuel coproducts which should decease costs and improve biodegradability. The 50/15/35 PLA data matched the strength of the 75% starch case; this demonstrates that glycerine does not negatively impact strength and does improve fabrication. Previously, DDGS concentration greater than 25% was not easily processed. Now, with the addition of glycerine, 50% DDGS is easily molded. Even the 80/5/15 could be processed; although the strength is somewhat low it would be adequate for some applications and is still about 1/3 the strength of the pure corn-starch while composed of 85% biofuel coproduct. The 20/15/65 PLA blend is similar in stiffness to the low-DDGS content starch. Higher coproduct inclusion deceases stiffness by 50%. Figure E.2 presents the hardness and indicates that the current blends are comparable to the DDGS-starch composites. Also available in the figure is wood data; the PLA blends are similar in hardness. The flexibility of a biomaterial is given in terms of its elongation to break. This is expressed by the percentage that the material strains (stretches) until it fractures. Testing indicates that all PLA formulations are rather brittle with less than 3% elongation. But the 50/15/35 case had the same flexibility as the 75% starch resin. So the presence of the glycerine adds ductility to the DDGS as the DDGS is present in twice the concentration. Another possibility is that the glycerine provides more binding strength to the DDGS fibers which holds the resin matrix together longer.
The resistance to a sudden blow or force (impact resistance) is shown in Figure E.3. In these data, actual golf tees were fabricated and impact-tested by swinging a pendulum-weighted hammer and breaking the tee. All the golf tees are relatively brittle, regardless of the material formulation. For comparison, a commercial wood tee is included in the series of tests. The 20/15/65P tee has similar impact strength to the 35/0/65 starch blend from the previous study. But the toughness is not greatly reduced from the pure PLA data indicating that PLA is generally more brittle than the starch. Any starch/glycerine blends may have better toughness.
Figure E.1. Ultimate Tensile Strength of PLA Blends; coded by weight percent: DDGS/Glycerine/Resin (P = PLA, S = starch)
Figure E.2. Surface Hardness of PLA Blends; coded by weight percent: DDGS/Glycerine/Resin (P = PLA, S = starch)
Figure E.3. Relative Impact Resistance of Golf Tees.
Conclusions:
The data already processed demonstrate the viability of the corn-based DDGS/biodiesel glycerine/PLA material. (Figure E.4 shows a sample pair of tees manufactured from a 20/15/65 PLA blend along with a pair composed of pure PLA.) Total biofuel coproduct concentrations between 35% to 80% represent reasonable inclusion values as sufficient mechanical strength is retained and a proportionally greater amount of the more expensive resin is replaced. The successful manufacture of the golf tees using these blends demonstrates that there is opportunity to provide a more green plastic product. An additional benefit is the expected accelerated biodegradability of the blends, compared to pure resin, wood, or current marketplace golf tees. Qualitative inspection of the golf tees shows a good smooth surface, typical of injection-molded parts. The DDGS also provided a rich, wood-like color. The general appearance resembles commercially-available tees in the marketplace.
This project definitely shows potential to effect positive impacts in moving towards sustainability, by reducing the need for petroleum inputs in plastics as well as by potentially improving the end-of-life biodegradability of plastic products. It is an adaptation of existing materials to a novel use. The current project in the Phase I form is successful. The combination of manufacturing improvement with the addition of glycerine with mechanical and physical properties testing has produced results for a prototype material. More testing would be promising and would shed light on future directions for expanded research. The disciplines represented by the team members from the Department of Technology contributed to the research effort, including the consideration of plastics properties, manufacturability, market drivers, and other factors in taking an overall systems approach to sustainability.
It is believed that this type of novel, platform technology has implications for applicability and transferability to a wide variety of industry realms in both the developed and developing world. For example, the plastics industry in the United States alone is one of the five largest industries, earning more than $320 billion in annual sales and employing over one million people. This industry continues to grow as plastics replace more traditional materials such as metals, wood, ceramics, and glass. Furthermore, the increasing demands of the global arena and the developing world will likely create even more opportunities for positively and proactively influencing global sustainability. Further work should include improving the properties of corn-based DDGS with resin blends, seeking other biodegradable resins compatible with DDGS, and obtaining added design properties for such bio-based green materials. Additional design properties may be thermal, optical, electrical, density, or others. Likewise research ought to be able to identify more product opportunities for DDGS in combination with glycerine.
Figure E.4. Photographic View of Golf Tees Fabricated from Bio-Blends.
Supplemental Keywords:
green chemistry, waste reduction, waste minimization, environmentally conscious manufacturing, biomaterials, biofillers, biobased plastics, green plastics, biodegradability, biocomposites, plastics technology, sustainability, renewabilityThe 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.