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The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Recycling

Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.

Mechanical Recycling of Polyethylene Bottle Caps — Characterization of the Various Material States Along the Process Value Chain

M. Hassan Akhras, Paul J. Freudenthaler, Joerg Fischer, March 2023

This study provides a practical demonstration of an open-loop recycling process by creating a pilot product using a defined post-consumer plastic waste stream. The study aims to investigate the possible changes in the material property profile throughout the whole recycling process. Additionally, it also aims to generate the necessary data for the implementation of digital product passport (DPP) as a potential material traceability tool.High density polyethylene (PE-HD) beverage bottle caps were selected as the targeted input waste stream. Two collection methods, informal and formal, were employed in this case study. To ensure a high purity level of materials before entering the recycling process, both input fractions were hand-sorted after the collection step. Subsequently, materials were shredded and re-granulated before being converted into the finished pilot product, which was defined as a frisbee (i.e., flying disc).To characterize the material property profile of the different material states, several measurements including melt mass-flow rate (MFR), differential scanning calorimetry (DSC), and mechanical tests were carried out. The informal collection led to a higher material purity as the other fraction had a more prominent melting peak of polypropylene (PP), which led to a slightly higher MFR value of this input fraction. However, no significant changes in the MFR values of the other materials were observed. In terms of the mechanical properties, the tensile stiffness and strength increased after processing. In contrast, the Charpy notched impact strength of the recyclates seemed to be slightly lower than that of both input streams.

Sustainability in Rotomolding

Denis Rodrigue, Ph.D., March 2023

In order to achieve more sustainability in rotomolded parts, several options are currently investigated. In this presentation, three possibilities are presented with typical examples produced at the lab scale (still under investigation). The first option is to use recycled resins instead of virgin ones. In this case, the recycled/virgin ratio can be change over the whole range of concentration; i.e. 0 to 100% recycled content. The second option is to add biobased fillers such as lignocellulosic fibres to get “greener” materials. In this case, the origin (wood, plants, etc.) and the particle size (mesh) are highly important. Finally, there is the possibility to use biosourced resins as the matrix. In this case, there is limitations in terms of availability and suitability of the resins for rotomolding processing, but good parts can be achieved after some optimization of the processing conditions (temperature, time, speed, etc.). Nevertheless, there is also the possibility to combine these options for specific applications (automotive, building, construction, outdoor, etc.). To get a clearer picture of the situation, typical examples will be presented and discussed in terms of physical and mechanical properties. Comparisons with petroleum-based resins is also included to determine the most interesting candidates for future developments.

circPLAST-mr - The Austrian Flagship Project on Mechanical Recycling of Plastics

Joerg Fischer, Reinhold W. Lang, March 2023

Initial situation, problem and motivation: The achievement of future EU and Austrian targets for mechanical recycling rates of plastic waste and the minimization of the EU plastic waste levy for non-recycled plastic packaging waste require significant improvements in all individual process steps of mechanical plastics recycling. For example, in order to achieve the EU target of a mechanical recycling rate for plastic packaging waste of at least 55% by 2030, the output efficiencies in the 3 essential process steps, (a) collection, (b) sorting and pre- processing, and (c) conversion & recovery, must be increased from the current Austrian status of approx. 58% for process steps (a) and (b) and approx. 78% for process step (c), to 80-85% (!) for each of these process steps.Objectives and intended outcom es: Building on the existing competences of the partners involved (11 scientific partners, 14 company partners), a further significant increase in knowledge and competence with regard to the entire recycling process loop is to be achieved through comprehensive and interactive integration and participation of the partners in the research program as an overall objective, which is indispensable for the achievement of the very demanding political target quotas. On the one hand, this knowledge generation relates in particular to necessary process and materials technology aspects and measures, but on the other hand also to logistical requirements for waste and material flow management. From this, 4 concrete main objectives including expected results are derived: (1) to identify and explore further, so far unused potentials for the mechanical recycling of plastics, (2) to define, implement and test key process steps on a laboratory/pilot scale, (3) to demonstrate the eco-efficient "marketability" of increased quantities of recycled plastics through exemplary products with improved quality and performance characteristics, and (4) to demonstrate the principle scalability of the laboratory/pilot processes to production scale (case studies).Innovation content and sustainability: The integrative and coordinated consideration of all process steps in the mechanical recycling of plastics, together with the structure and design of the research program, defined by the selected classes of material flows, plastics and products a s well as the process steps to be researched in the individual work packages and the associated effects on the material quality characteristics of the recyclates, form the overarching framework for the "conceptual" innovation content of this flagship project. Important innovation components also result from the use of digital technologies and modern, intelligent sensor technologies. This will enable the technical and the economic-ecological optimization of all process steps along the entire value chain of m echanical recycling of plastic waste from both separate collection and mixed waste. In the material flow management, special attention is paid to energy efficiency, the potential use of renewable energy technologies and the recycling of water including any additives (chemicals). The commercial implementation of the research results in future industrial practice is ensured not least by the main objectives (3) and (4) described above.

Influence of Macroscopic Contaminations on Mechanical Properties of Model and Post-Consumer Polypropylene Recyclates

Ines Traxler, Klaus Fellner, Joerg Fischer, March 2023

Due to insufficient sorting and recycling, macroscopic contaminations remain in post-consumer polyolefin recyclates. It is known that these contaminations affect the mechanical properties of the recyclates, as they constitute defects and thus crack initiators. However, the influences of different types and amounts of macroscopic contaminants have not yet been analyzed systematically.In this study, to close this knowledge gap, virgin polypropylene (PP) was systematically contaminated with paper, aluminum, sand, wood, in-mold labels, jute fibers and long glass-fibers. Additionally, three commercially available post-consumer PP recyclates were investigated. In a two-stage process, all materials were injection-molded into plates and subsequently milled to specimens. The specimens underwent (i) tensile tests at 50 mm/min, (ii) intermediate-rate tensile tests at 2000 mm/min, and (iii) tensile impact tests. Further, optical microscopy was used to measure the dimensions of the defects on the fracture surfaces.First, the influences of various types and quantities of contamination were evaluated. No significant effects were detected, as the matrix material was very brittle. Compared to the virgin reference grade, most samples showed lower strain-at-break values, except for those with labels and long glass-fibers, for which strain values increased. All PP post- consumer recyclates exhibited a more pronounced ductile behavior, although the contaminations incorporated gave rise to relatively high standard deviations. Second, in a comparison of various testing speeds, a greater influence of contaminants was detected in test (iii). Samples taken from a position close to the sprue had better mechanical properties than samples taken from the opposite side of the plate, as contaminants tend to flow to the end of the produced part. Finally, a non-linear relationship between the energy needed for fracture in testing methods (ii) and (iii) and the dimensions of the contamination on the fracture surface was found.

Simulated Closed-Loop Recycling of Electronics Plastic

Allison Ward, Nicolas Sunderland, Ph.D., March 2023

Mechanical recycling is one of the most economical pathways to reduce the environmental impacts of plastics. High-value, engineered plastics such as polycarbonate (PC) are being recycled at increasing quantities to the point that the supply of high-quality post-consumer recycled (PCR) polycarbonate is seen as an upcoming bottleneck to meet growing demand. There is an urgency to scale recycling of high-value, engineered plastics from the waste stream into new electronics. Accessible sources of recycled PC are still limited to select applications such as headlamps, construction sheets, and water barrels. In order to utilize material from additional waste sources, focus needs to be on addressing complicated waste types (PC with additives or PC-blends), reprocessing approaches to remove contamination (metals), and development of robust performance recycled content plastics. Mixed-plastic waste is commonly downcycled today and presents many challenges for the value chain from re-processing to the scale of e-waste collection. It is encouraging that many electronics brands have created take-back programs to increase collection rates and support scaling recycling technologies. However, today only a fraction of the electronics manufactured enter the recycling stream. Lack of volume and consistency in waste material streams present another challenge for the industry. Dell, Covestro, and MPT together investigated the effects on material properties, processing, and component quality levels through multiple rounds of simulated closed-loop recycling with positive results. A PC/ABS + talc blend was used as the base production material to add reground scrap parts and mold new laptop components. A total of three recycling loops were tested (equivalent to ~32 years), increasing regrind content by 20% each loop. Impacts of UV monocoat paint on the recycling process were also examined. Results showed the material could be recycled several times and still retain high performance. Paint had a minimal impact on the recycled material performance. Closed-loop recycling of PC and PC blends can offer an efficient pathway to recycle laptop plastic materials. The recycling process from collection, dismantling, and sorting is critical to influence the quality of e-waste to be further developed for second-life use. Laptop brand manufacturers also use a common framework of materials primarily based around polycarbonate and polycarbonate blends, creating an opportunity for scale. Circular design principals must be considered for long-term recycling success and support circular e-waste models.

An Assessment of Landfill-Bound Mixed Plastic Waste From Material Recovery Facilities (MRFs) in the United States

Victor Sanfins Cecon, March 2023

Victor received his Bachelor's degree in Chemical Engineering from the Federal University of Sao Carlos (UFSCar, Brazil) in 2019 and is currently pursuing a Ph.D. in Food Science and Technology at Iowa State University under the supervision of Dr. Keith Vorst. During his undergraduate studies, he was a visiting scholar at the University of British Columbia (UBC, Canada) for one year and an R&D intern for 1.5 years at 3M Brazil. His research focuses on the mechanical and chemical recycling of landfill-diverted mixed plastic waste with the use of several polymer processing and characterization techniques, as part of the efforts of the Chemical Upcycling of Waste Plastics (CUWP) center.

EVOH for Pharmaceutical Sustainable Forming Films

Edgard Chow, March 2023

Blister packs is one of the most important presentations in the pharmaceutical industry. As we all know, the brand owners and the global market are being pushed by the sustainability trends and regulations to look for alternatives towards recyclability. Typical structures of blister packs contain not friendly materials like PVC, PVDC OR PCTFE. This conference will present some test of structures using EVOH and COC creating a blister packaging with high barrier and excellent optical properties that also are design for mechanical recycling.

Ensuring the Safe Use of Recycled Polymer Resins Through the Development of Testing for Volatile Organic Compounds. Discussion on Methodology and Results

Kevin Guigley, Ph.D., March 2023

It is well known that melt processing post-consumer (PCR) or post-industrial (PIR) recycled resins can generate foul odors due to contamination and/or thermal degradation. Additional components, such as printing inks and adhesives in plastic packaging, may be viewed as contaminates in the recycled resin and can contribute to this problem. Some of these odors could be from volatile organic compounds, VOC’s, with known safety concerns. With a growing need in the flexible packaging industry to increase circularity through the use of PCR and PIR materials, there comes an increase in risk for health concerns and food safety. Amcor has developed methods using gas chromatography, GC, along with heated headspace sampling, HS, to chemically identify and measure the VOC released from PCR/PIR that have known safety concerns such as acrolein, methyl acrolein, and benzene. These methods help Amcor evaluate the quality of PCR/PIR sources to determine feasibility for certain applications, and aid in the design of next-generation recycle ready packaging films. This will be a discussion on the development of the testing methods along with results of VOC analysis.

Synthesis of Thermoresponsive Hydrogels for Atmospheric Water Vapor Harvesting

Pavani Cherukupally, Ph.D., March 2023

About 4 billion people around the world are suffering from water scarcity, which is expected to increase due to increasing global warming [1, 2]. One of the solutions to address the water scarcity challenge is to tap the 13,000 trillion of water present in the atmospheric air in the form of fog, droplets, or vapor [3]. Simple fog collection systems effectively harvest water without investing energy in highly humid environments [4], but they are ineffective in arid regions like Arizona, where the humidity is low. Alternatively, adsorbents designed to capture water vapor during colder nights and release it during the hotter day could provide a passive solution to harvest water vapor in the arid regions of the world [5,6]. Recently, porous polymeric hydrogels have been reported for water droplets harvesting from the air. The gels were fabricated with thermoresponsive polymers, such as polypyrrole chloride penetrated PNIPAM, that can switch to hydrophilic and hydrophobic structures at lower critical solution temperature (LCST) and upper critical solution temperature (UCST), respectively [7,8]. By leveraging their switchable wetting properties, the water droplets were captured during the night at higher humidity and lower temperature conditions and collected during the day at lower humidity and higher temperature conditions. However, the influence of LC/UCST on the hydrogel's chemical and morphological structures has not been investigated, as well as harvesting water vapor present in arid regions. In this work, we report the fabrication of thermoresponsive P(NIPAM-co-BzDMA) copolymeric hydrogel to collect water vapor from the air across all humidity conditions. The hydrogels were fabricated by tuning the temperatures and compositions to achieve large surface area-to-volume ratios, ordered porous structures, and excellent switch between the hydrophilic-hydrophobic wetting properties. The gels synthesized at LCST at BzDMA salt concentration of 15% could uptake 20% higher water than their counterparts. Experimental: The P(NIPAM-co-BzDMA) gels were synthesized by thermally initiated polymerization at LCST or UCST to determine the influence of their switchable hydrophilic-hydrophobic structures on the efficacy of crosslinking [9]. Then the PNIPAM was copolymerized with BzDMA salt at three concentrations of 10%, 15%, and 20% by weight. The synthesis was carried out for 4 hours under nitrogen and then freeze-dried for 12 hours in vacuum environments. The resulting porous gels were named based on their salt concentrations as P(NIPAM-co-10%BzDMA), P(NIPAM-co-15%BzDMA), and P(NIPAM-co-20%BzDMA). The surface functional groups of the hydrogels were determined using Fourier Transform Infrared Spectroscopy (FT-IR, Bruker, Germany). The morphological and crosslinking structure of the gels were evaluated using scanning electron microscopy (SEM, Hitachi Instrument, Japan). The thermoresponsive phase change behavior of the materials was verified using a Differential Scanning Calorimetry (DSC) at a heating rate of 2 C/min from 10 to 60C under a nitrogen environment (DSC, TA Instrument, USA). The switchable wetting properties of the gels were examined through water contact angles (WCA) measured at 20 and 40C. The water vapor adsorption-desorption isotherms were measured using an intelligent gravimetric analyzer (IGA, Hiden Isochema Ltd., UK). Results & Discussion: The successful synthesis of PNIPAM at LCST and UCST was confirmed from the FT-IR spectra. It showed two intense peaks at 1677 and 1563 1/cm, corresponding to C=O and N-H or C-N, respectively. The spectra also showed bimodal peaks at 1390 and 1379 1/cm from the isopropyl, peaks at 2987 and 2942 1/cm from methylene, and a broad peak at 3310 1/cm from N-H stretching [10]. Relative to LCST, the functional groups showed more intense peaks for PNIAM @UCST. It could be because the large number of oxygen radicals generated at higher temperatures could increase crosslinking of PNIPAM. The SEM images of the P(NIPAM-co-BzDMA) hydrogels showed interconnected microporous structures caused by freeze-drying [11]. Compared with PNIPAM@UCST, the PNIPAM@LCST had orderly distributed pores. The BET (Brunauer, Emmett, and Teller) surface area of the PNIPAM@UCST and PNIPAM@LCST were 2.91 mˆ2gˆ-1 and 2.67 mˆ2gˆ-1, respectively. At LCST, the slow copolymerization reaction rate and the homogeneous hydrophilic-hydrophilic structures of copolymers created orderly-distributed, uniform pores across the hydrogels. In contrast, at UCST, the fast copolymerization reaction rate and heterogeneous hydrophilic-hydrophobic networks of copolymers produced randomly-distributed, nonuniform pores. The BzDMA could react and maintain a stable morphological structure with both gels. The DSC thermograms confirmed that both PNIPAM and P(NIPAM-co-BzDMA) could change phase at approximately 32 C. Next, the WCAs measurements showed that all gels exhibit superhydrophilicity at 20C and hydrophobicity at 40 C, as intended. The adsorption-desorption isotherms of hydrogels showed an S shape curve suggesting water vapor can be harvested without losses. However, below LCST, due to superhydrophilicity of PNIPAM and P(NIPAM-co-BzDMA), the water molecules have a higher affinity to bind with the adsorbent, swell and cause a larger hysteresis loop and higher water uptake capacity. The water uptake capacity was found to be 20% highest for P(NIPAM-co-BzDMA) at 15% salt concentration than its counterparts. Conclusions: Our results suggest the influence of synthesis temperature-dependent chemical structures on the overall water vapor uptake capacities and collections was negligible. However, the gels synthesized below LCST and 15% salt concentrations slowed the copolymerization reaction rate, created uniform morphology, and delivered a higher water uptake capacity. Based on these process parameters and compositions, scalable hydrogel-based adsorbents can be designed for large-scale water vapor harvesting across all climate conditions, especially in highly-needed arid regions. References: 1. G. Meran, M. Siehlow, C. von Hirschhausen, The Economics of Water: Rules and Institutions. Springer Nature (2021). 2. M. M. Mekonnen, et al. Sci. Adv 2 (2), e1500323 (2016). 3. H. Kim, et al. Science 356 (6336), 430-434 (2017). 4. J. Ju, et al. Nat. Comm. 3 (1), 1-6 (2012). 5. N. Hanikel, et al. Nat Nanotechnol 15 (5), 348-355 (2020). 6. P.A. Kallenberger, et al. Comm. Chemistry 1(28), 1-6 (2018). 7. F. Zhao, et al. Adv. Mater. 31 (10), 1806446 (2019). 8. K. Matsumoto, et al. Nat. Comm. 9 (1) 1-7 (2018). 9. H. Yang, et al. Adv. Mater. 2013, 25 (8), 1150-1154. 10. Y. Dong, et al. Appl. Surf. Sci. 307, 7-12 (2014). 11. Z. Shen, et al. Soft Matter 8 (27), 7250-7257 (2012). 12. W. Xu, et al. ACS Cent Sci 6 (8), 1348-1354 (2020).

A Review on LCA Studies on Grocery Plastic Bags and Their Substitutes

Iván Darío López Gómez, Alejandro Serna Escobara, March 2023

Single-use bags have been banned or restricted around the world. Substitute alternatives have been explored, including biodegradable bags, reusable bags and the use of other materials such as paper or cotton. The Life Cycle Assessment (LCA) is the most widely accepted tool for carrying out comparative studies between alternatives. In this study, the literature on LCA of grocery bags was reviewed in search of common conclusions. In general, reusable plastic bags are identified as the alternative with the lowest environmental impact , obtaining on average a 73% reduction in the climate change index compared to the alternative with the highest impact in each analysis. Reuse and recycling have a lower environmental impact than composting, landfilling or incinerating. Open challenges are discussed, including the requirement for the development of a new index to quantify plastic leakage into the environment.

Design From Recycling: How to Design Robust Plastic Parts Maximizing Their Recycled Content

Giovanni Lucchetta, Ph.D., March 2023

With climate change worsening, people have become more conscious of their environmental impact. Companies are receiving growing pressure to use increasing content of post-consumer recycled (PCR) plastics in their products. However, PCR plastics differ from virgin materials in several mechanical, physical, and rheological properties, posing design and molding challenges for manufacturers. In this work, a polypropylene (PP) compound is produced and characterized using different contents of PCR PP to model its properties as a function of PCR content. A numerical approach is then proposed to determine the maximum content of PCR PP suitable for a given application. Furthermore, a robust design approach is proposed to identify engineering changes for both part and mold design that can make the part performance insensitive to lot-to-lot variations of the PCR properties.

Mechanical Properties of Bio-based Composite from Orange Peels

Yousef A. Mubarak, Deeb Abu Fara, March 2023

Orange peels have high cellulose content and they are available in good quantities. The present study aimed to a produce bioplastic composite based on orange peels. Orange peels were ground using a semi-automatic grinder before the pre-treatment step. The peels were immersed in a 15% sodium hydroxide NaOH solution for 4 hours at 60°C to remove the lignin, hemicelluloses, and other pectic substances. Then, they were neutralized with 1% acetic acid before being washed with distilled water and dried overnight at 60°C in a convective oven. Different natural additives, including starch, glycerol, agar-agar, and D- sorbitol, were added to the orange peels to develop the bioplastic material for optimized mechanical and plasticizing properties. To enhance the mechanical properties of the orange peel bioplastic, calcium carbonate was used in different weight percentages.The ultimate tensile strength of the orange peels bioplastic samples increased from 0.9 MP to 2.4 MPa with the addition of 8 wt% calcium carbonate. On the other hand, the fracture point decreased from 20% to almost 13% strain by the addition of calcium carbonate, the bioplastic become more brittle as the weight percentage of calcium carbonate increased. The bending tests showed that the maximum deflection achieved before fracture is equal to 12 mm and that the specimen can withstand forces up to 6.2 N. This indicates that the achieved biomaterial has a remarkable bending strength and can withstand up to 6.2 N before fracture, proving that it has a strong bending behavior. The deflection decreased by about 20% when 8 wt% of calcium carbonate existed in the matrix and the bending withstand force reduced to about 5.0 N. It is expected that applying a coating layer to the orange peels bioplastic end products makes them more attractive and expands their commercial applications.

Mechanical Recycling Of Single-Use Polyethylene Into Materials With Variable Properties

Arun Ghosh, Ashik C. Kannan, June 2022

The post-consumer single-use polyethylene-based plastic bags supplied by the supermarket grocery stores, are converted into new materials with improved mechanical properties using a thermo-mechanical recycling process. The low-density polyethylene (LDPE) sourced from waste plastic bags, is injected into a high shear internal mixer and compounded with the additives such as acrylonitrilebutadiene copolymer or nitrile rubber (up to 10 wt%) and also treated with an organic peroxide curing agent. The resultant materials exhibit high ductility and elasticity, with a maximum tensile strength of 20.3 MPa, stiffness of 1262 MPa, elongation of approximately 500%, and impact strength of 62 kJ/m2 depending on materials compositions. These mechanical properties are profoundly higher than those of neat recycled LDPE. It is observed that the post-consumer plastics contain a significantly high amount of calcium mineral of approximately 30 wt% (13 vol %)[1], which plays a key role in improving mechanical properties during high shear blending with additives such as nitrile rubber. The melt-rheological characteristics such as complex viscosity and storage modulus of the materials are analyzed to evaluate the thermal recyclability and thermoplastic nature of the materials.

Thermal & Rheological Characterization Of Two High Density Polyethylene Grades

Phat T. Vu, Azizeh-Mitra Yousefi, June 2022

Presently, polymers such as high density polyethylene(HDPE) are utilized for an extensive array of applications because of their low weight, economical production, and exceptional physical and chemical properties. Thermal analysis and rheological measurements are the ideal techniques for characterizing the material properties of polymers. This paper employs thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and capillary rheometry to collate the contrasting nature of two HDPE resins. These resins will be referred to as HDPE A and HDPE C and are similar to two resins (Sample A and Sample C) included in a previous publication [1] that focused on blow molding parison sag and swell. TGA was used to investigate the thermal stability of these polymeric materials, as they were ultimately decomposed inside a furnace. DSC was conducted to examine the thermal transition behaviors of the polymers. Capillary rheometry was run to construct shear viscosity and extrudate swell versus shear rate data through single and twin bore configurations under varying temperatures. These measurements were conducted under testing conditions that are representative of industrial processes, such as extrusion blow molding. HDPE C was found to exhibit greater extrudate swell than HDPE A, as measured by capillary rheology measurements, and these data correspond to the earlier published results that Sample C exhibited greater parison diameter, thickness, and weight swell than Sample A as measured with a lab scale extruder.

Enhanced Compost Rate With Simultaneous Toughening By Multifunctional Particle Additives In Poly(Lactic Acid)

Caroline R. Multari, Raymond A. Pearson, June 2022

A particle additive is reported that simultaneously improves ductility and biodegradation behavior of poly(lactic acid) (PLA). Our approach explores the use of encapsulation technology to create degradation-promoting additives while limiting any breakdown of the matrix during melt extrusion and service life. In addition to promoting biodegradation such encapsulated particles are designed to enhance toughness of the matrix. Such dual use particles have the potential to broaden the uses of PLA. In this work, particle properties are examined and the accompanying tensile behavior and compostability of the composite investigated. Particles were dispersed within the PLA matrix by extrusion to 3D printer filament. Elongation at break was improved over neat PLA with limited loss of yield strength. Degradation rate in compost is accelerated and decoupled from environmental conditions by embedding a degradant material into the PLA matrix itself, aided by encapsulation technology that isolates and protects the degradant. The additive has been found to improve mechanical properties while accelerating the biodegradation of parts produced by extrusion-based methods.

Investigation Of Orotic Acid Effects On The Crystallinity Development Of Poly-Lactic Acid

Faisal J. Alzahrani, Peng Gao, Alaauldeen Duhduh, John P. Coulter, June 2022

This research investigated the effect of the addition of Orotic Acid (OA) on the crystallization kinetics of Polylactic Acid (PLA) in quiescent and non-quiescent conditions. A differential scanning calorimetry (DSC) study was used to investigate and understand the effect of the addition of orotic acid on 2500 HP PLA under quiescent conditions. DSC technique was utilized to capture the crystallinity, melting point, and other thermal parameters of PLA-OA blends. Conventional injection molding (CIM) was used to investigate the influence of adding OA into PLA under non-quiescent conditions. Two concentrations of orotic acid, 0.3 wt% and 0.7wt% were mixed with neat PLA and then investigated. It was observed that the 0.3 wt.% orotic acid provided significant improvement in crystallization kinetics by increasing the crystallinity and reducing the incubation time. Both blends under quiescent conditions showed almost the same crystallinity in which the maximum crystallinity that was observed was around 63% in the blend of the PLA/0.7OA at 85°C. For 2500HP PLA, Orotic acid (OA) showed to be an effective nucleating agent. A small amount (0.3 wt%) was sufficient to achieve 61% of crystallinity in injection molding at 80°C mold temperature.

Recycled Carpet-Reinforced Composites From Polyester Carpet And Recycled Pet Resin

Mohamadreza Y. Azarfam, Anuj Maheshwari, Frank D. Blum, Siddhesh Chaudhari, Clinton Switzer, Ranji Vaidyanathan, Jay C. Hanan, June 2022

A method was developed for fabricating recycled composites from post-consumer polyethylene terephthalate (PET) carpets and recycled PET resins. Compression molding of the components under different pressures, temperatures, and compositions was performed. Preliminary molding conditions were arrived at based on analyzing the differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and melt viscosity data for different raw material combinations. Molding factors were screened to define applicable ranges for each parameter. The effects of configuration and composition of components, temperature, molding time, and pressure were considered in the screening process. Mechanical properties of composites were determined by 3-point flexural (according to ASTM D790) and creep tests. The molded materials showed acceptable mechanical strength and modulus values required for structural applications.

Moisture Sensitivity Characterization In Pla/Pbs Parts During Ultrasonic Welding

Raihan Quader, David Grewell, Lokesh Narayanan, Leo Klinstein, Bill Reed, June 2022

Ultrasonic welding (USW) is a surface mating process where absorbed moisture in the surfaces of hydrophilic materials can negatively affect the weld joint quality and strength. USW is a secondary processing operation that is performed post-molding or extruding. Hence, during the storage time between primary processing and USW, the parts are susceptible to moisture absorption. Therefore, it is necessary to characterize the moisture sensitivity to meet the specified weld strength. Moisture sensitivity of Industrial standard test parts (ISTeP) made with PLA, PBS, and PLA/PBS 25/75 blend was characterized for USW in this study. ISTeP parts were moisture conditioned for one week at different relative humidity (RH) levels and then tested for weld strength. It was found that the weld strength decreased with increase in RH for 100% PLA ISTePs but it was not statistically significant. Above 65% RH, weld strength of 100% PBS was significantly decreased. Scanning electron microscopy of weld areas after the pull test revealed an increased amount of trapped porosity in the fractured surfaces of high relative humidity samples. It was also demonstrated that PBS and PLA/PBS composite can be ultrasonic welded.

Long Term Aging Characteristics Of Post-Consumer Recycled (Pcr) Polycarbonates

Rashed Islam, Jacki Laiz, Dolaphine Kwok, Swanand Vaidya, Ayyana Chakravartula, June 2022

In this paper, the tensile properties of indoor and outdoor post-consumer recycled (PCR) polycarbonates (PC) have been compared with virgin PC at various aging conditions. 50% recycled PCs showed comparable tensile strength at breakage (~70 MPa) and maximum strain (~190 - 200%) before aging, when compared to virgin PC of same MFR of ~10 g/10 min. Three different high temperature and high humidity aging conditions were investigated: 40oC 90% RH, 60oC 90% RH, and 85oC 85% RH for up to 500 hours. Strength at breakage was found to decrease as the aging stress or aging time (with the same aging condition) was increased. Both the indoor resins were comparable in strength up to 60oC 90% RH. But in 85oC 85% RH both showed significant drop in strength. On the other hand, outdoor PCR resin showed much better performance (only ~12% degradation) in 85oC 85% RH compared to other two indoor resins (25 - 40% degradation). Outdoor UV aging characteristics were also compared between 0%, 50% and 75% PCR and degradation up to 600 hours were found to be within 5%.

Improving The Ductility Of Recycled Pet For Plastic Lumber Applications

Richard P. Heggs, Prabhat Krishnaswamy, June 2022

Recycling of plastic waste at Forward Operating Bases. (FOBs) is continuing to be a topic of considerable interest to the Department of Defense. A previous paper [1] by the current authors described the need and opportunity to convert this waste stream to plastic lumber that could be used by the warfighter for various construction applications at forward operating bases (FOBs). The selected technique of flow intrusion molding of recycled PET (rPET) into 1 inch by 1 inch by 36 inch test specimens showed feasibility of this recycling technique and the resulting specimens were very stiff with high modulus but they failed during testing in a brittle fashion with fragmentation. This is not a desirable failure mode and work was conducted to improve the ductility of the plastic lumber specimens using both chain extenders and impact modifiers. This paper describes the investigation of using additives to improve ductility and therefore the utility of rPET to make plastic lumber using flow intrusion molding and the resulting performance characteristics.