SPE Library

Agile Formulation of Recycled Polymers

Dr. Mark Sullivan and Hannah Melia, December 2023

Polymer recyclates have a variation in properties that can affect the end properties of recycled polymers. In this session, Dr. Mark Sullivan and Hannah Melia of Citrine Informatics will present a case study to show how AI can be used to rapidly reformulate recycled polymers to maximize the use of recyclates while consistently meeting end customer requirements. Learn from Citrine's experience from more than 10 years working in machine learning for materials and chemicals development.

Introduction to Plastics

Jeff Jansen, January 2024

Plastics are the most versatile materials ever invented, and have become a universal material, used for everything from water bottles to wings on combat aircraft to implanted artificial joints. Thermoplastic materials display properties that are unique when compared to other materials and have contributed greatly to the quality of our everyday life. At this moment, you are almost certain to be touching plastic. Yet, while plastics play such an important role, we do not always understand the fundamental concepts of their production, compounding, end properties, and use. If words such as polymer, thermoplastic, creep, amorphous, and modulus are outside your normal vocabulary, this presentation is for you. At the conclusion of this presentation, you will understand:

• How polymers build molecular weight through polymerization and its importance in the performance of thermoplastics.
• The role that polymer structure plays in shaping the key characteristics of plastics.
• How crystallinity the plays an important role in determining the properties of plastics.
• The essentials of viscoelasticity.

The usefulness of thermoplastics is attributed to the fact that they provide a wide range of properties and can be changed into products by relatively simple and inexpensive fabrication means. In order to take full advantage of these materials, it is important to have a clear understanding of their composition and elementary properties.

Revisiting the Sustainability of Flame Retardant Ethane Bis(pentabromophenyl): Assessing the Degradation Throughout its Lifecycle

Rajeev Mathur, March 2023

Photolytic and thermal degradation are important processes to the overall sustainability and environmental impact of a flame retardant for a given commercial application. Details on accelerated photolytic aging and recycling studies of ethane bis(pentabromophenyl) (EBP), often called decabromodiphenyl ethane (DBDPE), will be presented.

Parting Ways With PFAS Through Novel Fluorine-Free PPAs

Joshua Heidebrecht, March 2023

Due to the viscoelastic flow characteristics of polyethylene (PE) and the interaction of molten PE with metallurgy of a die surface, flow instabilities occur after exceeding a certain shear rate, temperature or mean velocity, which was initially discovered in 1958. This flow instability and melt fracture leads to an undesirable product appearance and can negatively impact product properties due to the emergence of a “sharkskin” morphology of produced film. In addition, melt fracture is one of the first instabilities that occurs at higher throughput, which can limit rates of commercial applications. Although the flow characteristics of polyethylene cannot be modified easily, specialty additives such as polymer processing aids (PPAs) can deposit on the die surface, inducing slip and enhancing flow. With this additional lubrication, die pressure can be lowered and the onset for melt fracture can be delayed, leading to significant commercial rate improvements. Fluoropolymers are ubiquitous within the field of PPAs for polyethylene and incorporate fully-fluorinated carbons to reduce interactions of the molten polyethylene and the die surface. While the efficacy of fluoropolymers to delay the onset of melt fracture is well described, the current regulatory landscape is progressing rapidly for the broad ban of perfluoroalkyl substances, which incorporates fluoropolymers. Although the chemistry and migration of fluoropolymers is quite different than that of perfluorooctanoic acid and perfluorooctanesulfonic acid which bans initially targeted, the current legislations are covering all compounds with at least one fully fluorinated carbon. Regarding plastic packaging, there are multiple states that have passed bans effective in 2023, with additional regulations going through the US and EU that come into effect within the next few years. For converters and film producers to maintain current rates and product morphology, new PFAS-Free technology needs to be developed and implemented within a very short timeframe. This presentation will provide insight into the mechanism at which processing aids lubricate the die and reduce melt fracture, cover academic and literature-based PFAS-Free PPA technologies and deliver an overview into the development of PFAS-Free PPAs at NOVA Chemicals. The performance of NOVA Chemicals fluorine-free PPA technology and efficacy towards melt fracture clearing will be presented alongside the effectiveness of fluorine-free PPA to prevent die lip build up.

Novel Analytical Toolkit for the Development of Halogen Free Flame Retardant (HFFR) Polypropylene Compounds

Swaraj Paul, March 2023

Polymer materials are made fire resistant basically by controlling either the bulk properties of polymers i.e., the condensed phase or by controlling the gas phase chemistry i.e., the volatiles that are formed due to polymer degradation under burning conditions or by controlling both. This suggests that if materials could be designed with low specific mass loss rates under fire conditions, the amounts of volatiles formed would be substantially reduced resulting into less combustion and thereby less heat generation. The latter would result into less increase of surface or ignition temperature of the materials resulting into less thermal degradation of materials. This suggests that important parameters that control the condensed phase properties of polymers to make them fire resistant are surface or ignition temperature and the kinetic degradation parameters of the materials. Another parameter that has a great influence on the fire properties is the gas phase chemistry, which in turn, is controlled by the volatiles formed during the burning process. The volatiles formed differs both with respect to flammability and generation of heat of combustion. This suggests that both the total amount of volatiles and the chemical composition of the volatiles formed because of burning are important to improve fire resistance properties of the materials. Therefore, preferred volatile compositions are also presumed to be effectively improve the fire properties of the materials. Furthermore, in phosphorus (P) and Phosphorus-Nitrogen (P-N) based (PFR) halogen free flame-retardant systems, it has been suggested that formation of P and PO radicals in the gas phase are important to obtain good fire-resistant properties because they both function as effective radical quenchers and char formers resulting into less heat generation. For radical quenching presence of phosphorus in the form of P and PO radicals in the gas phase are important. This suggests that distribution of phosphorus both in the condensed and in the gas phase should play an important role in controlling the fire properties. This proposes that selection of suitable PFR compounds that renders a preferred P distribution in the gas and in the condensed phase is important to obtain good fire resistance properties. Unfortunately, quantitative estimations of the above-mentioned parameters are lacking in the literature. In this presentation, we shall present a toolkit to experimentally measure these parameters for different HFFR PP model compounds and their correlations to the UL94V results. The study shows that we obtain a good agreement between these quantitative parameters and UL94V tests. This suggests that our toolbox could be very helpful and effective tool both to characterize and develop new and effective HFFR formulations instead of using single point UL94V tests that are being commonly used today.

A Numerical Study on the Fiber Detachment affecting the Complex Stress State at Microstructural Level of Unidirectional Fiber Reinforced Plastics

Nicolas Rozo López, March 2023

The fatigue performance of unidirectional fiberreinforced plastics is subjected to complex damage mechanisms, dependency on the load direction, and straindependent material behavior. In addition, the strength of the fiber/matrix interface is one of the main influential fa ctors on the composites’ fa tigue life. Its characterization, however, is effortful and the results are prone to large scatter. Moreover, the microstructure within the composite leads to a complex stress-strain field that changes with each fiber break, or detachment. So far, this resulting internal stress-strain fields only have been possible to be investigated by numerical approaches. In this work, a single fiber break model was extended to a representative volume element model (RVE) within the finite element method. A composite material made of carbon fibers and epoxy resin is being investigated. The behavior of the two constituents is assumed to be orthotropic and isotropic elastic, respectively. The complex microstructure is represented by a random fiber distribution generated with a sequential expansion algorithm, and periodic boundary conditions are applied. The fiber strength is modeled as a Weibull-distribution. A parameter study is carried out to analyze the influence of the fiber/matrix detachment rate on the internal stress distribution. Principal Component Analysis (PCA) is introduced to reduce the dimensionality of the problem. The obtained results show that PCA can reduce successfully complex stress-strain fields to an eigenvalue and eigenvector problem. Furthermore, the simulations show that the fiber detachment length correlates with the number of load cycles.

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.

Novel Flame Retardants Based on Ionic Liquids for PMMA, PC and TPU Plastics

Yanjie”Jeff” Xu, April 2021

Inovia Materials LLC is positioned to develop new generation flame retardants and flow enhancers based on ionic liquids, to replace and expand the applications of traditional additives with high “green chemistry” qualities, superior performance and enhanced properties. we have developed new flow enhancers for PC, TPU, TPAE and high-performance plastics: PAR, PPA, PPS, PSU, PEI, PEEK, etc. Our flowing enhancers have superior thermal stability (400 degree C TGA), perfect compatibility (ionic liquids being tailorable), significant increase melt flow index at very low loading level, and mild effects on the physical-mechanical properties of plastics. We welcome product application opportunities from industries.

Characterization and Processing of Thermally Conducting Thermoplastic Elastomers For A Microclimate

Szetong de Cleir, May 2020

A commercially available grade of thermally conducting TPE was characterized and processed into tubing for use in a microclimate cooling system. This paper details the material characterization, extrusion of the resin into tubing, and the evaluation of tubing properties. A series of extrusion trials was conducted to establish a relationship between processing parameters. It shows there is a weak relationship between draw ratio and tensile properties. At last, future work is proposed to further improve the thermal conductivity of this material.

Characterization of Polycarbonate – Using Thermogravemetric-Rheology Analysis

Jamal Al Sadi, May 2020

The objective of this work is to study the rheological characteristic of the formulations and the processing of plastic production. In this work, introduced two polycarbonate resins were melt blended using two different twin-screw extruders, targeted to investigate the PC blends on the characterization behavior of the grade. Formulation and processing parameters showed an excellent effect on controlling the viscosity. The research aims to identify the underlying science by conducting a systematic study of two stages. First, the polycarbonate 30/70% (Grade-3) was chosen from historical data mining extracted in our project as was showing a high number of adjustment; the material was melt-blended using (Coperion) a Co-rotating twin-screw extruder (SB). The two polycarbonate resins (PC1/PC2) were PC1 content (30wt%-pph) of MFI (25gm/10mins) and PC2 content (70 wt.%-pph) of MFI (6.5gm/10mins). The grades also included four different color pigments and three additives. The second stage, the same material was included the same composition were blended in steps of eleven in a Thermo Haake Mini Lab II twin-screw micro compounder (ML). The steps (%PC1/%PC2) were (100%/0%), (90%/10%), (80%, 20%)… (0%/100%). This resulted in eleven batches. The rheological behavior of the compositions with pigment (WP), without pigments and additive (WOP) at 280 0C have been characterized through experimental measurements. The viscosity measurements of Variation PC blends of (30-70%) and at (0%, 30%, and 100%) were characterized at certain processing of (SB) and (ML). Thermogravimetric analysis (TGA) was performed under the effect of heating rate, Glass transition temperature (Tg) for PCs blends was measured and related it is affected by the minute variation blends, viscosities, and the various interactions indicated a significant effect on color changes.

Comparison of Longevity of PE- and PP-based TPO Waterproofing Membranes

Yushan Hu, May 2020

This study compared the longevity performance of polypropylene (PP) and polyethylene (PE) based thermoplastic polyolefin (TPO) waterproofing membranes. It was demonstrated that PE-TPO outperformed PP-TPO for both heat aging and standard UV aging in terms of tensile property retention, weight retention and resistance of surface cracking. Better longevity for PE-TPO is attributed to the lack of tertiary carbon which is intrinsic to PP and prone to chain scission.

Development of Shape Memory Thermoplastic Polyurethane (TPU)/Polylactic Acid (PLA) Polymer Blend

Yuelei Guo, May 2020

Shape memory polymers represent a family of stimuli-responsive materials that can be used in many applications. Polylactic acid (PLA) is a type of shape memory polymers that is biocompatible and biodegradable. By blending PLA with thermoplastic polyurethane (TPU), its shape memory effect would be improved. This study aims to optimize the shape memory effect of TPU/PLA polymer material systems and investigate the influence of material compositions and processing conditions on their shape memory effects. Blends were fabricated with different compositions and/or different thermal history. Experimental results revealed that the addition of TPU increased the recovery but decreased the fixity at the same time. Overall, the 65/35 TPU/PLA blend has the best shape memory performance. The duration of stretching at the transition temperature in the process of the test of the shape memory properties influenced the crystallization of samples. The sample could show a bad shape memory effect if the stretching time is too long.

Engineering Impact Modification of Polypropylene for Low-temp/High-strain rate Loading Conditions

Chinmay Saraf, May 2020

This communication presents a systematic investigation of polypropylene (PP) formulations modified using SEBS (Styrene-ethylene/butylene-styrene) and POE (Polyolefinic elastomer) block copolymers for impact modification. Impact performance of PP formulations containing POE, SEBS+POE and SEBS is compared under extreme conditions (high strain rate at -15°C and -30°C) and during quasi-static fracture tests at 25°C. Present work also discusses the effect of talc reinforcement on the fracture toughness of these formulations. The focus of the present work is to investigate the failure mechanisms of these formulations and understand how it correlates with the size, shape and other morphological features of the phase-separated SEBS and/or POE domains. The results show that the formation of crazes is the major energy absorbing mechanism at subzero temperatures. The 1 um domain sizes for SEBS modified PP leads to the stabilized craze formation and the highest fracture energy absorption amongst all the formulations investigated. It is shown that the effective stiffness of the dispersed phase and optimum particle size controls the damage density and energy absorption for polypropylene under extreme conditions.

Erucamide Slip Analysis in Polyethylene by GC using a Nitrogen Chemiluminescence Detector

Garry Yamashita, May 2020

Additives are commonly used in polyethylene applications to provide processing and long-term stability as well as to enhance or modify polymer performance for specific physical properties. Slip agents are one type of modifier used to alter the coefficient of friction in polyethylene films. Fatty amide based slip agents function by migrating to the surface of the film to provide a lubricating layer which enables the film surfaces to slide more easily across one another and when in contact with blown film extrusion and conversion equipment to facilitate processing. A combination of direct (e.g. XRF) and indirect (e.g. HPLC) analytical methodologies are used to measure the additive types and levels used for polyethylene applications. For slip agent analysis, the fatty amide is typically separated from the polymer matrix using an extraction technique (e.g. Soxhlet, Microwave, ASE) or by use of total polymer dissolution followed by polymer precipitation. The extract is then filtered and analyzed by a chromatographic technique, typically, HPLC-UV, GC-FID, or GC-MS. In some instances, polymer matrix signals from oligomers or other additives can interfere with the analysis. Furthermore, the slip agents from various suppliers are a mixture of fatty amides so analysis of the erucamide peak requires inherent knowledge of the specific amide distribution for the supplied slip agent. In this paper, a new and novel use of a gas chromatograph with a nitrogen chemiluminescence detector will be presented which illustrates a universal calibration of erucamide slip agents that compensates for the various amide distribution profiles from three different suppliers. This approach can also be extended to other slip agents such as behenamide and oleamide.

Functional Alkane Solvent Systems

Ying-Hua Fu, May 2020

An oligomeric hydrocarbon, Poly(α-olefins) (PAOs), were previously reported as a potential greener solvent to replace conventional alkanes solvent due to its lower toxicity, flammability and volatility. However, its poor solubility toward most organic substrate may limit its applications as solvent. This work demonstrated three strategies to introduce polarity in PAOs and recycle polar additives simultaneously: polymerization of polar monomers onto a PAO anchor, host-and-guest interaction and end-group modification of a PAO anchor, vinyl-terminated polyisobutylene (PIB). In the first method, RAFT polymerization gave a better control of polar polymers onto PIB in order to maintain hydrocarbon solubility over other two polymerizations (hydroboration/O2 initiation, ATRP polymerization). Secondly, the polar polymer, poly(isopropylacrylamide) (PNIPAM) could be successfully brought into and recover back out an alkane phase by treating with chemicals via a hydrogen bond network. The reversible solubilization of PNIPAM were used in recyclable Rhodium catalyzed hydrogenation. Lastly, a hydrophilic moiety (Hexamethylphosphoramide, HMPA) was successfully incorporated onto PIB. The hydrocarbon soluble Lewis base catalyst can be used in allylation of benzaldehyde in PAOs. Other ongoing studies are exploring this molecular recognition based solubilization with other solubilizing agents, other precipitation agents and exploring the use of this chemically responsive solubility both as a tool to prepare new solvent systems and new sorts of recyclable catalysts.