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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Lexington Peterson, Brandon Birchmeier, March 2023
The macro-issues the plastics industry is trying to resolve today pertain to sustainability, supply chain shortages, and the lack of skilled labor. Within the injection molding sector, manufacturers typically perform a full validation when a mold is moved to a different injection molding machine (IMM) or there is a material change. These full validations are labor-intensive, expensive, and not sustainable. Moreover, these methods may or may not utilize scientific molding principles. There has been a demand for a standard “part process” development method to transfer a mold between IMMs that is more efficient and can embrace variation in resins. iMFLUX’s Auto-Viscosity Adjust (AVA) technology has made doing so easier with its low, constant pressure injection molding process. This adaptive technology enables the molding process to automatically adjust parameters in real-time around parts’ response. This research focuses on developing a regenerative part process with low, constant pressure that is independent of resin and machine. Using AVA and cavity pressure sensors, two molds’ processes were transferred to another capable press with the original process, no user adjustments, and parts were studied for visual and dimensional integrity. It was determined that iMFLUX can automatically regenerate optimized part processes in different IMMs deemed capable with negligible part variation as seen from the visual and dimensional results. This is the first time an intelligent controller can autonomously redevelop and validate a part process to mold parts within spec despite varying IMMs and resins.
Glass-filled engineering polymers are a staple in the automotive, aerospace, and medical industries. However, understanding the influence of glass fibers on the crystallization behaviors of these polymers is not trivial - especially at heating and cooling rates encountered during melt processing. Sample preparation plays an important role in the success of thermal analysis. For conventional differential scanning calorimetry (DSC) characterization, larger sample size is often used for composites than neat resin to mitigate the impact of possible filler inhomogeneity. Because the sample is quite small (thickness of less than 20 µm and a mass of less than 1000 ng) for fast scanning calorimetry (FSC), the potential impact of sample preparation on data reliability is very significant. In this study we explore and quantify the effect of sample preparation for DSC and FSC on crystallization kinetics in a wide temperature range using three grades, Poly(ether ether ketone) (PEEK), and its glass-fiber-filled composites (PEEK with 15 wt% and 30 wt% glass fiber) were studied, and X-ray computed tomography (XCT) with an ultrahigh-resolution was performed to reconstruct the interior structure of the composite pellets. When the sample thicknesses is less than 50 µm, the PEEK sample sliced perpendicular to the fiber flow direction have good filler homogeneity and always have a lower coefficient of variation than pellets sliced along the fiber flow direction. Furthermore, the data collected by both FSC and DSC were fitted and showed that FSC and DSC analysis can be reasonably used to predict the kinetics of composite materials.
In injection molding of fiber-reinforced thermoplastics, in the presence of physical obstacles, such as cores, or for geometries that require multiple gates, weld lines develop where flow fronts rejoin. Regions affected by the presence of weld surfaces show worse mechanical properties. In fact, these areas are characterized by incomplete welding between the flow fronts and the presence of undesirable inclusions and porosity. In addition, due to the fountain-like flow in cavities, fibers on the weld line are unfavorably arranged and are unable to reorient themselves in the flow direction. If the incident flow fronts exhibit no pressure gradient during the defect formation and the holding phase, the morphology of the weld surface remains unchanged until the end of the process. By inducing a pressure imbalance after the formation of the weld line, on the other hand, it is possible to promote the interpenetration of one front into the other and significantly modify the local morphology. A dynamic packing stage during the first part of the holding phase therefore allows for improved matrix interdiffusion at the interface and fibers reorientation in the flow direction. Gas Assisted Injection Molding (GAPP) is a novel technology that allows for the dynamic packing of weld lines using only a single injection unit. Thanks to miniaturized gas injectors, it is possible to manipulate the molten polymer in the cavity and generate a flow through the weld surface. The dynamic packing achieved using GAPP allows for the elimination of weld lines in the core layer of the molded part, significantly increasing its mechanical performance. For a 35% glass fiber reinforced polypropylene, an increase in tensile strength and stiffness of 240% and 21.5%, respectively, can be observed in the defect region. GAPP can be implemented to solve weld line strength problems in all parts made of fiber-reinforced thermoplastics that require high mechanical performance, such as supports, brackets, cooling fans, pulleys, and other structural parts.
Prof. Dr.-Ing. Christian Hopmann, Moritz Mascher, M.Sc. RWTH, Christoph Zimmermann, M.Sc., March 2023
In this work, a practical and simulative study of the surface roughness of the injection mold cavity and the corresponding heat transfer between the plastic melt and the mold cavity was conducted. The work shows that slightly longer flow paths can be achieved through the rougher mold surface, which indicates to a lower heat transfer. However, the influence is small compared to other influences such as the used molding compound or the injection pressure. An analysis of the structural replica over the flow path shows a clear decrease in the structural height towards the end of the flow path, i.e. with decreasing pressure and lower melt temperature. To describe the influence of microstructures on the heat transfer using injection molding simulations accurately, a model calibration is used.
Russell G. Speight, Paul A. Brincat, Vishak D. Perumal, March 2023
Injection molding simula tion bega n in the 1970’s, with
technology advancing to the present day. In parallel,
material testing technology has evolved over the same
period, to meet the increased accuracy demands of
simulation. The accuracy of injection molding simulation
is influenced by many factors such as: (i) modeling of part
geometry, (ii) runner and nozzle, (iii) mesh type and
density, (iv) mathematical finite element solution, (v)
injection molding machine process settings, and (vi)
material data. The focus of this paper is material data, from
the latest material testing methodologies, outlining
technological evolution to meet the demands of the highest
Accumulated used polymers and tires cause several ecosystem issues in landfills. A practical method was proposed to reuse recycled polyethylene terephthalate (rPET) and ground tire rubber (GTR) powder by melt composite process. A composite material was developed in this work using GTR for reinforcement and rPET for matrix. The effect of two non-reactive (styrene-butadiene-styrene (SBS) and styrene-ethylene-butadiene-styrene (SEBS)) and three reactive (ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA), ethylene-glycidyl methacrylate (EGMA) and SEBS grafted with maleic anhydride (SEBS-g-MA) coupling agents on the mechanical properties of the composite material were evaluated. Mechanical tensile and impact strength properties were evaluated to determine how coupling agents affect composite behavior. All reactive coupling agents improve the mechanical behavior of composite materials, whereas non-reactive ones have little effect. EMA-GMA and EGMA are more reactive with rPET than SEBS-g-MA. Using 10 wt% of EMA-GMA in the composite of rPET/GTR (4:1) increases the tensile strain and impact strength (950% and 23%, respectively) and decreases maximum tensile strength and Young’s modulus (16% and 35%, respectively).
Polyolefins functionalized with reactive side groups are known to provide improved properties to blends of incompatible resins including processability, homogeneity, and mechanical properties. However, experimentation and use of compatibilizers are limited to virgin based grafted resins, which incurs additional costs for processors. Thus, there is increasing interest in upcycling post-consumer polyolefins to higher value secondary feedstock streams that offer interfacial adhesion of polymer blends. In this work, we propose a melt grafting strategy to achieve reactive functionality and apply the method to post-consumer polypropylene with the purpose of demonstrating recycled polyolefins capabilities as compatibilizers. Experiments are performed using a semi-batch co-rotating micro-conical twin screw extruder at various screw speeds and temperatures. The torque and grafting percentages are controlled by varying the concentration of dicumyl peroxide and maleic anhydride. The functionalized polypropylenes are characterized using spectroscopy and thermal analysis techniques to determine the grafted content and resulting processing behavior. The reactive extrusion process is compared with that for functionalizing virgin polypropylene, and the scale up and economics are discussed.
The Association of Plastic Recyclers (APR) has published several methods for evaluating the recyclability of polyethylene plastic films. Although the methods are developed for lab-scale process equipment, a large amount of film is typically required for a complete evaluation. To accelerate screening of new film structures and compositions, we have developed a small-scale workflow based on a LabTech Micro Blown Film Line. It only requires 200 grams of materials to blow a film for film properties characterization. In this paper, we will present three case studies to demonstrate this workflow. First case study is the effect of paper label residuals in the post-consumer recyclate (PCR) on the film properties. Second case study is on the recyclability of a PVOH coated film. And the third case study is on the effect of compatibilizer (RETAINTM 3000 Polymer Compatibilizer from Dow) on the recyclability of an EVOH containing multilayer film. The advantages of this workflow are: 1) low materials consumption (200 grams vs > 4 lbs per formulation); 2) fast elimination of formulations that cannot be used in the blown film process; and 3) film properties that provide some indication or ranking of the formulations with different recycle content. Although this workflow may not have high resolution of film properties for complicated film formulations (such as those using a small amount of compatibilizer), it accelerates recyclability assessments for blown film.
Multi-materials plastic films are especially important in our daily food packaging. It can combine different polymers to achieve a range of properties, which can’t achieve by mono-material film. It can protect the food, increase the shelf life of packaged food, and reduce the food waste. However, the recycling of the multi-material packaging film faces big challenges due to the incompatibility of different materials. With the increasing awareness of plastic pollution issues, there is a clear and present need to find a way to recycle multi-material film structures to support the goals of the circular economy. Compatibilizer can help improve the compatibility of polar and non-polar components in the films by increasing the interfacial adhesion between the two phases. In the research, we developed a novel polyethylene (PE)/Polyamide (PA) or ethylene vinyl alcohol (EVOH) compatibilizer. Based on the tensile, dart impact and tear test results, with loading of this novel compatibilizer to the PA or EVOH at 1:10 ratio, up to 20% PA or EVOH can be incorporated into PE stream without scarifying too much mechanical properties and meet the Association of Plastic Recycler (APR) recognition requirements. The microscopy pictures clearly showed that the compatibilized blend has a homogeneous morphology while the blend without compatibilizer has clear 2 phases. This novel compatibilizer provides the possibility of recycle-ready multi-material film structure design and improve the sustainability of the multi-material films.
Global plastics recycling rates are low and the market share of recycled plastics is less than 10% at the moment. People are searching for different ways to further improving the recycle rates for plastics, especially for PET. However, companies’ sustainability efforts have been hampered because recycled PET (rPET) can exhibit poor mechanical properties compared to virgin PET (vPET) due to the lower intrinsic viscosity (IV). At Kaneka, we know additives can significantly improve the prospects for recycled plastics. The newly developed IV booster MV-01 showed promising performance when used in rPET. The study shows that at low dosing level MV-01 in rPET can improve the IV to the same level as vPET even after 4 passes. In addition, the mechanical property, transparency, YI, and Haze are all well maintained. Therefore the recycle content of PET can be significantly improved after adding MV-01 to the PET compound.
Tim Dawsey and Ram K. Gupta National Institute for Materials Advancement, Pittsburg State University, 1701 South Broadway Street, Pittsburg, Kansas 66762, United States The current shift from solely depending on petroleum sources to seeking renewable alternatives is attributable to their fast depletion, erratic prices, and the need to reduce our carbon footprint. For instance, the polyurethane industry currently calls for renewable (and less toxic) polyols and isocyanates for their synthesis over the traditional petroleum-based ones. To tackle these issues, we have investigated the role of vegetable/fruit oils in the preparation of polyurethane foams. Different approaches such as thiol-ene click chemistry and epoxidation, followed by ring opening, were used to convert these oils into polyols. The effect of the synthesis process on the properties of polyurethanes was studied. One of the major issues in polyurethanes is their high flammability. To reduce the flammability of polyurethane foams, different types of flame-retardants (additive and reactive) were investigated during the foaming process. The effect of flame-retardants on the physicomechanical and flammability of the foams was investigated in detail. Most of the foams displayed density in the range of 30-55 kg/m3 which is suitable for many applications. The compressive strengths of these foams were higher than 160 kN/m2. Except for some high concentrations of flame retardants, most of the foams showed closed cells greater than 90%. It was found that the burning time of the foams reduced significantly after the addition of flame retardants. For example, foam prepared using sunflower oil-based polyols showed a reduction in burning time from 79 seconds to 2 seconds after the addition of 13.61 wt.% of dimethyl methyl phosphonate. The effect of various flame-retardants and the role of bio-based polyols on the properties of polyurethane foams will be discussed. Our research suggests that a variety of bio-based materials can be used for the polyurethane industries with a reduced impact on the environment.
This presentation provides an example of comparative Life Cycle Assessment for fossil-based and bio-based polymers that are non-compostable and compostable respectively. In this instance, fossil-based and non-compostable gloves made from polyethylene were compared with our commercial bio-based and compostable gloves utilizing ISO 14040:2006, ISO 14044:2006 and ISO 22526:2020 standards. As bio-based materials are created on a much shorter timescale than fossil-fuel reserves, some consider bio-based polymers to be a form of carbon sequestration. This means that bio-based polymers can be said to have a lower feedstock carbon emission burden than fossil-based alternatives. A major discrepancy, however, when comparing fossil-based and bio-based materials largely arises due to how biogenic carbon is accounted. This normally stems from how bio-based materials have their system boundaries drawn, where sequestration of CO2 is immediately tied to end-of-life emissions and taken as a net zero summation. This handling is the current methodology employed by the European Union Product Environmental Footprint (EU PEF) which states, “removals and emissions of biogenic carbon sources shall be kept separated in the resource use and emissions profile”. We compare this mindset to that of ISO standards and give a representative understanding where fair comparisons are possible for fossil-based and bio-based plastics, and when fossil-based materials are preferentially benefited with this tactic. In doing so, this presentation will provide the audience with an understanding on the bias LCA methods have against bio-based materials when biogenic carbon is not properly accounted for and give specific criteria which allows for a fair comparison with their fossil-based counterparts.
PHAs or polyhydroxyalkanoates are recognized for their unique ability to biodegrade in many natural environments including marine, home compost and industrial compost sites. As a result, PHAs are used in many applications where end of life is a critical value proposition. We have previously highlighted the value proposition of blending an amorphous grade of PHA (PHACT A1000P) from CJ Biomaterials in various compostable product formulations including those based on PLA, PBS, PBAT and starch. In this presentation, we will address new opportunities for A1000P in the non-compostable space. Specifically, we will highlight applications where incorporating A1000P into the formulation brings benefits that include biobased carbon content, flexibility and toughness. Examples will include enhancing the performance of products based on Acetal polymers, Nylon-11 and Nylon-12 and EVA.
Combining its own technology in polymerization and polymer rheology, Kaneka North America provides the processing aid to enhance the melt strength of bioplastics like PLA. The poor melt strength of PLA causes drawdown and sagging in the melt process, leading to low productivity. The processing aid dramatically increased the melt strength of PLA at 1 % loading level. During the extrusion process, it reacts to PLA and creates a comb structure. But it didn’t affect optical properties without forming gels. It was also designed to keep the melt viscosity low so that the processing rates can be high. It worked for PHA as well. The 1% addition doesn’t impact on the certification of biodegradability. This technology could enable access to more cost-competitive and sustainable bioplastics with a broader application window. Blow molding of bottles, film blowing, fiber spinning, and foaming could be facilitated by the materials exhibiting the high melt strength.
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
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.
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.
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.
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.
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.
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