This Small Business Innovation Research Phase I project will effectively and efficiently recycle post-consumer plastic materials for high value applications through an innovative and environmentally benign approach known as solid-state shear pulverization (SSSP). SSSP subjects the materials to high shear and compressive forces and avoids melting. In contrast, the current technique for recycling post-consumer plastic involves batch grinding commingled, unsorted color waste to form flake scrap material followed by melt-processing, pelletizing, and finally extruding the pelletized plastic waste to form recycled plastic products. Utilization of post-consumer plastic materials processed in this manner is severely limited due to poor mechanical performance and color distribution of the resultant product. Sorting, adding compatibilizing agents and cleaning have been used to improve the final performance of the recycled product. However, these additional steps are quite expensive, rendering the use of recycled materials impractical. For the use recycled materials to become more widespread, an innovative and cost-efficient technology is needed to yield a product that is similar in both cost and performance to virgin materials. In this project, the company will use SSSP to process unsorted, uncleaned post-consumer materials to overcome these issues and manufacture cost competitive, high-value recycled consumer products.
The broader impact/commercial potential of this project is the effective recycling and utilization of post-consumer plastic materials. In 2010, only 8% of the 31 million tons of plastic waste generated in the United States was recovered for recycling. A majority of the remaining spent plastic was found in municipal solid waste streams or landfills, contributing heavily to pollution and environmental contamination. The company will use a novel approach, SSSP, to recycle materials without the need for cleaning or sorting, thereby reducing processing steps and making the use of these materials more cost competitive with virgin resins. In addition to the major environmental benefits, a successful proposal will also result in significant economic implications. It has been found that processing recycled materials alone creates nine jobs for every 15,000 tons of recovered materials. Furthermore, the increase in recycling will attract new industries, subsequently leading to an increase in the number of green jobs available. Ultimately, this innovation will enhance scientific understanding by investigating a novel, environmentally benign approach for polymer processing and will lead to the development of recycled materials that will be applicable to many industries.
The current technique for recycling post-consumer plastic involves batch grinding commingled, unsorted color waste to form flake scrap material followed by melt-extrusion (ME), pelletizing, and finally molding the pelletized plastic waste to form recycled plastic products. Utilization of post-consumer plastic materials processed in this manner is severely limited due to poor mechanical performance and color distribution of the resultant product. Sorting, adding compatibilizing agents and cleaning have been used to improve the final performance of the recycled product. However, these additional steps are quite expensive rendering the use of recycled materials impractical. For this phase I SBIR work, NuGen Polymers utilized a novel, environmentally benign, continuous, and industrially scalable process known as solid-state shear pulverization (SSSP) to effectively and efficiently recycle commingled post-consumer plastic materials without sorting, removal of labels or use of compatibilizers. By eliminating steps currently required in the recycling of post-consumer products, NuGen was able to produce recycled plastic feedstocks at a lower price, thereby making post-consumer platics more economically viable for commercial use. The results from the phase I SBIR proposal show several major advantages of SSSP and its use in recycling post-consumer plastic. The following illustrate the major findings: First, it was shown that SSSP prior to ME leads to enhanced mechanical performance and reduced variability in most mechanical properties tested as well as uniform color in almost all samples tested as compared to ME only materials. Second, SSSP prior to ME enables the processing of polymer mixtures with PVC and PET present. This is due to the fact that SSSP allows for breakup and dispersion of large polymer flakes into small micron sized filler. Essentially, because the PET flakes can be pulverized into small filler, the blend can be processed at much lower temperature, thereby reducing the degradation of PVC. Third, it was shown that all mechanical properties for the uncleaned, commingled post-consumer plastic homopolymers processed via SSSP/ME fall within ranges shown on virgin homopolymers. The only exception was the yield stress of PVC. Ultimately, the post-consumer SSSP processed materials could replace those virgin materials for many applications. Overall, SSSP enables recycling of plastics that are currently sent to the landfill in two ways. First, waste plastics that are otherwise-immiscible can be combined with traditional recycled plastics using SSSP. Second, material properties of these mixtures can be improved due to more intimate mixing and the formation of new chemical bonds. Other research has demonstrated the ability to tune the physical properties of plastic mixtures using waste fillers because SSSP forms new bonds between fillers and polymers. The broader impact/commercial potential of this project is the effective recycling and utilization of post-consumer plastic materials. In 2010, only 8% of the 230 million tons of plastic waste generated was recovered for recycling. A majority of the remaining spent plastic are found in municipal solid waste streams or landfills, resulting in poor use of non-renewable resources which contributed heavily to pollution and environmental contamination. NuGen Polymers utilizes SSSP to recycle materials without the need for cleaning or sorting, thereby reducing processing steps making the use of these materials more cost competitive with virgin resins. In addition to the major environmental benefits, successful commercialization of SSSP and large scale processing of commingled, uncleaned recycled plastics will result in significant economic implications. It has been found that processing recycled materials alone creates nine jobs for every 15,000 tons of recovered materials. Furthermore, the increase in recycling will attract new industries subsequently leading to an increase in the number of green jobs available. Ultimately, this innovation enhances scientific understanding by investigating a novel, environmentally benign approach for polymer processing and leads to the development of recycled materials that are applicable to many industries.
