SPE Library

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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Conference Proceedings

Technology for Ultra-pure Recycled PP

John Layman, February 2020

Consumers increasingly expect and demand sustainable products without performance and price trade-offs, and companies, like P&G, have established long-term sustainability goals that include the use of large percentages recycled resins in their products and packaging. To satisfy consumers’ expectations and achieve companies’ goals, P&G has developed a novel purification technology that converts contaminated recycled resins into virgin-like resins. The proprietary technology is based on the use of a hydrocarbon solvent at elevated temperature and pressure, and a novel combination of standard chemical engineering unit operations, such as liquid – liquid extraction, sedimentation, size exclusion and adsorbent filtrations, and devolatilization. These processes purify the recycled resins via removal of odor, volatile organic chemicals, and other organic and particulate contaminants and additives. Initial focus of the technology is on polypropylene (PP); however, purifications of other polymers are currently under development. The PP purification technology was patented by P&G and licensed to Innventure, which launched PureCycle Technologies (PCT) in September 2015 to commercialize the technology. The 70-ton capacity pilot plant started operation in July 2019, and commercialization is slated to start in 2021/22 with a ~50 kta capacity plant.

Surface Characterization of Polyolefins Modified by Surface Initiated Radical Polymerization

Atsushi Takahara, February 2020

Direct surface modification of polymer films by surface-initiated polymerizations has been carried out. The introduction of initiating sites on the polymer materials and successive polymerization produce surface-tethered polymer chains on the polymer surface. The surface-selective modification controls the surface properties such as wetting, lubrication, and adhesion without sacrificing the bulk performances. Among various procedures for the initiating group introduction and subsequent polymerization proposed so far, this study focuses polymer brush grafting to polymer films through surface-initiated radical polymerizations. Researches on grafting polymer chains to five different types of solid polymers, poly(methyl methacrylate)-based copolymer, Br-containing polyolefins, poly(butylene terephthalate) (PBT), poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-co-TrFE)], and poly(ether-ether ketone) (PEEK) are summarized. The surface-initiated polymerization produces thick stable polymer brush layer on polymer films with various morphologies. The polymer surfaces are homogeneously covered with polymer brushes without serious defects to change the surface properties without sacrificing the bulk performances and the morphology.

Stochastic Estimation of the Lifetime of Polyethylene Pipe with Arbitrarily Located Defects (Paper)

Byoung-Ho Choi, February 2020

Polyethylene is one of most popular materials for various piping applications. There are three failure modes for polyethylene pipes, i.e. ductile fracture with large plastic deformation (mode I), quasi-brittle fracture with slow crack growth (mode II) and mechano-chemical fracture with localized degradation (mode III), and mode II failure mode is frequently observed from field fracture samples. So, according to standard tests from ISO and ASTM, the resistance to slow crack growth of pipe-grade polyethylene resins should be evaluated. However, it is commonly observed that there is quite large scatter of test results, and many factors such as defect locations, defect sizes, loading conditions, specimen geometry etc. should be considered to analyze test results. So, stochastic approaches are required to estimate the lifetime of polyethylene pipe under mode II failure. In this study, slow crack growth behaviors of polyethylene pipe are simulated for defects with arbitrarily located defects, and the simulation results are analyzed by a continuous probability function. In many cases, it is observed that slow crack growth with mode II failure is in discontinuous manner, so the crack layer theory with new Green’s functions is applied to simulate the slow crack growth behavior from the arbitrarily located defect.

Stochastic Estimation of the Lifetime of Polyethylene Pipe with Arbitrarily Located Defects (Presentation)

Byoung-Ho Choi, February 2020

Leverage Materials Science to Frozen Food Packaging (Paper)

Jong-Young Lee, February 2020

Polyethylene (PE) is widely used in packaging applications today due to its low cost, good processability, and superior toughness. Coextruded blown films are commonly used in PE-based frozen food packaging, with linear low density polyethylene (LLDPE) making up more than 80% of the structure. In recent years, there has been a strong desire to down-gauge the film while maintaining the incumbent packaging abuse performance. Therefore, a LLDPE resin with better abuse performance at cold temperature (< 0 °C) is needed to satisfy the market need. Much research has been done to establish the relationship between the molecular architecture of PE and the dart impact resistance (related to the toughness) at room temperature, but the knowledge at cold temperature is still very limited. Based on our study, high dart impact resistance of LLDPE film at room temperature does not guarantee high dart impact at cold temperatures. Therefore, more knowledge is needed about the cold temperature toughness of LLDPE. In this paper, we provide a fundamental understanding of the influence the basic molecular architecture (e.g. melt index, molecular weight distribution, glass transition temperature) of LLDPE resin has on the dart impact resistance at cold temperature. Dart impact resistance is measured on LLDPE blown films using an Instrumented Dart Impact instrument in a temperature controlled chamber. The results provide guidance for film converters to select LLDPE products to meet the abuse performance needs of PE-based frozen food packaging.

Leverage Materials Science to Frozen Food Packaging (Presentation)

Jong-Young Lee, February 2020

Scratch Behavior of Polymer Coatings

Mohammad Hossain, February 2020

Polymer coatings have been widely used to improve the tribological performance of various products in electronics, optics, and automotive applications. To further enhance the tribological performance, multilayer polymeric coating and/or single layer composite coating can be applied on polymer substrate. In this study, three-dimensional finite element method (FEM) modeling has been carried out to explain the scratch-induced deformation and damage mechanisms observed in polymer/composite coatings applied on polymer substrate. The stress and strain field analysis using FEM explains the mechanics behind the observed scratch behavior of coating systems. The results show that coating layer thickness and mechanical properties significantly affect the scratch resistance of coating systems. Furthermore, anisotropic behavior of composite coating can significantly influence the scratch behavior. The study provides useful insights toward designing surface damage resistant coating systems.

On Characterization of Dart Impact Resistance of Thin Plastic Films

Bikramjit Mukherjee, February 2020

We investigate the role of film/dart friction on the results of dart impact test used to characterize toughness of plastic films against impact (biaxial loading) at a high speed (~3 m/s). Utilizing an instrumented dart impact (IDI) capability, impact tests were conducted for plastic films exhibiting a wide range of dart impact values under standard test conditions. A Steel dart and a Polytetrafluoroethylene (PTFE)-coated dart were used with the former representing a high-friction interaction and the latter a low-friction one at the film/dart interface. Our results indicate that differentiation between films on the basis of their impact toughness may change dramatically depending on friction. Load-displacement curves obtained from the IDI tests, a simplistic analysis of forces, failed samples, finite element simulations, and high-speed tensile tests help us rationalize our findings about the effect of friction on impact toughness of films.

New Styrenic Block-copolymer Impact Modifiers for TPO Compounds

Amit Desai, February 2020

Polypropylene (PP) is commonly used in various interior and exterior parts of an automobile for several reasons, such as low cost and ability to tailor properties using additives. These compounded PP formulations are also referred to as thermoplastic polyolefin or TPO. A key additive used in these TPO compounds is an impact modifier to improve the impact resistance of the part. In this presentation, we discuss development of new styrenic block-copolymers (SBCs) as an impact modifier for TPO compounds. Typically, a combination of polyolefinic elastomer (POE) and SBCs are used as impact modifiers for TPO, which provides an appropriate balance of cost and impact performance. In these formulations, the role of the SBC is to compatibilize the POE with PP and achieve a desirable morphology (mainly desirable elastomer domain size and distribution), which results in acceptable impact performance. In this presentation, we report development of a series of polymers to further increase the compatibility of SBC with POE and PP and consequently improve the impact resistance. A few of these new polymers led to a significant increase in impact strength compared to existing formulation without significantly affecting other physical properties, such as stiffness and melt flow. We also performed morphological investigations to confirm the hypothesis of improved compatibilization leading to better impact resistance. These new impact modifiers can enable the use of TPO compounds in newer applications demanding higher performance, such as thin-walled and low-density parts.

EOS Polymer Laser Sintering: Enabling Applications Through New Materials

Cary Baur, February 2020

EOS specializes in laser sintering technology, which uses thermoplastic powder, along precise thermal control and laser power, to produce three-dimensional parts from a digital file. Our technology is widely used across many industries, from flame retardant polyamides for ductwork in commercial aircraft to PEKK - carbon filled materials for high temperature, chemically resistant, and high mechanical strength applications such as brackets and valves for oil and gas, automotive, and aerospace. Our focus is on providing machines that can utilize many materials to meet our customers' needs and a wide selection of custom materials targeted at their specific application criteria. This presentation provides an overview of how our technology works, what types of materials we use, and how we approach material development to enable new, advanced applications with our customers.

HP Multi Jet Fusion Additive Manufacturing - the Technology and Fit into Production Manufacturing (Paper)

Barbara Arnold-Feret, February 2020

Additive manufacturing and polyolefins seem to have been a match made in heaven. However, the very characteristics of polyolefins that made it an ideal material for molding and other plastics processing can made it more of a challenge in the additive manufacturing side. Where some of the additive manufacturing equipment currently on the market utilizes polyolefins as a functional building material, the polyolefin material can create a cross road in performance. These issues can affect accuracy, strength, and speed of platform issues in use. An outline of how HP deals with the processing of plastics using Multi Jet Fusion (MJF) and with explainations, details and breakdowns to de-mythicize the MJF process is presented. Understanding the process helps understand where polyolefins fit into the HP MJF printing material universe. To explain the details of the Multi Jet Fusion (MJF) process, familiarity with the mechanism of how the fusion of the plastic is done and the basics of the interface need exploration. This paper is an overview of the MJF process, why the process serves as a unique method of manufacturing and summarizes the HP materials roadmap as of January 2020.

HP Multi Jet Fusion Additive Manufacturing - the Technology and Fit into Production Manufacturing (Presentation)

Barbara Arnold-Feret, February 2020

Determination of Interfacial Strength in Semi-rigid Laminates

Glendimar Molero, February 2020

A testing methodology to evaluate the adhesive strength of epoxy coatings and multi-layered polymeric laminates was developed by implementing a linearly increasing normal load scratch test. Finite element methods (FEM) modeling was also carried out to quantitatively investigate the corresponding stress profile that causes delamination to occur during scratching. By including the exact material constitutive behavior, surface characteristics, and geometry of each laminate layer in the numerical framework, the delamination strength of the laminates can be quantitatively determined using numerical modeling. The determination of the delamination strength between the weakest layer is possible by normalizing geometric factors and material properties in the FEM model. This procedure can be employed to improve laminate performance through changes in formulation and processing conditions.

Tie Layer Adhesion Chemistry for Multilayer Packaging

Mou Paul, February 2020

Multilayer packaging is an integral part of today’s life ranging in applications from food packaging to medical, consumer and industrial applications. By virtue of a multilayer structure, a combination of functionalities can be achieved which is not possible with a single layer structure. Orientation of multilayer films is important for various commercial packaging forms, especially when they are related to shrink such as barrier shrink bags, retail skin packaging, shrink films etc. Orientation enhances barrier properties and improves mechanical properties and can support packaging weight reduction. This is of a significant interest in light of sustainable packaging as oriented films can help to reach the goal of packaging waste reduction. In a multilayer film, a compatibilizer or a tie resin is often needed to adhere together the dissimilar polymers such as apolar polyethylene or polypropylene with polar substrates such as polyamides, ethylene vinyl alcohol (EVOH), polyesters, glass, paper, metal, coatings. Maleic anhydride grafted polymers, ethylene- acid copolymers, ionomers, ethylene-ester copolymers are some common examples of tie resins. The adhesive property of a tie resin is very critical for delivering the total functionality of a multilayer package. It becomes even more challenging when the packaging fabrication involves orientation and shrink as stretching and orientation can significantly reduce interlayer adhesion. A thorough review of the factors that influence adhesion at highly oriented structures can facilitate fundamental understanding and product strategy development. This paper will focus on a review of tie resins and how it impacts adhesion in multilayer packaging, particularly on oriented films. A major thrust will be given to understand the influence of molecular architecture of the tie resins and the interaction of tie layers with other layers on the adhesion properties. Effect of processing on tie layers will also be discussed. The paper will concentrate on journal and patent literature including brief summary of impactful data and will aim to establish fundamental understanding on adhesion in highly oriented structures.

Glass Filled Polypropylene with Improved Heat and Chemical Stability

Jing Liu, February 2020

In response to the high demand on lightweighting in the automotive industry, various reinforced polypropylene solutions have been explored and developed. Properties of filled polypropylene which have been greatly improved include stiffness, impact strength, higher fluidity and heat and chemical resistance. Thanks to these improvements, a broader range of performance requirements formerly exclusive to engineering plastics can now be achieved by polypropylene solutions alone. In this paper, we will discuss the development of PolyOne’s short-glass-fiber reinforced polypropylene which provides enhanced stiffness and impact properties, along with excellent heat and chemical stability.

Fundamentals of Twin-screw Compounding - Effective Mixing, the Key to Product Quality

Justyn Pyz, February 2020

The process for compounding thermoplastic formulations, both highly filled fiber or mineral products as well as color and additive MB, is comprised of several unit operations. These typically include: feedstock introduction, polymer or polymer/pigment melt-mixing, distributive/dispersive mixing of pigments/minerals/additives, removal of volatiles, and pressurization for die discharge. However, at the end of the day, if the fiber, mineral or pigment is not properly mixed into the polymer matrix, the product is not saleable. While the above list denotes a specific unit operation associated with mixing, mixing occurs along the entire length of the screw configuration in the co-rotating fully intermeshing twin screw extruder. It can range from dispersive mixing (i.e. wide disc kneading block combinations as part of, for example, titanium dioxide incorporation) to distributive mixing (that occurs during melt conveying as a result of rotation of screw bushings). Mixing in the screw bushings results from material reorientation in the apex region and circulatory flow induced by drag forces in the screw channel. The magnitude of the resultant mixing at any point along the screw depends upon the extruder barrel and screw configuration, characteristics of the materials being processed, and operating conditions. The required type and intensity of mixing depends on 1) the process task (talc filled vs. carbon black based MB), and 2) the relative physical and rheological properties of the materials being mixed. Independent of material parameters, mechanical energy input will vary according to basic extruder geometry characteristics (2 lobe vs. 3-lobe, outer diameter/inner diameter ratio [Do/Di]), element configuration, as well as operating conditions such as RPM, throughput rate, degree of fill, and barrel temperature profile. Material parameters such as viscosity, viscosity differential, elasticity, interfacial surface tension, thermal stability, as well as imposed discharge constraints, such as material temperature, particle size, and particle size distribution will dictate as well as limit the type and intensity of mixing necessary (or allowed) to accomplish the unit operation. This presentation provides a further discussion of the issues noted above as well as associated examples especially considering Polyolefins.

Compatibilizers to Improve Regrind Utilization and Recycling of Multilayer Barrier Rigid Packaging

Hyunwoo Kim, February 2020

Blow molded or thermoformed multilayer containers of polyolefin with barrier polymers like ethylene vinyl alcohol (EVOH) or polyamide (PA) are being offered as a sustainable packaging solution for oxygen or chemical barrier. It is common that the trim scrap materials are recycled back to the packaging article as a regrind layer. Recycling of the trim scrap materials from the multilayer articles of these incompatible polymers is not straightforward. Without proper compatibilization, recycling of the multilayer packaging structures can result in undesirable results such as large un-melts and gels, poor processability, and deterioration of the properties of the finished products. One solution to this recycling challenge is to utilize functionalized polyolefin materials to compatibilize the immiscible polymers in the recycled stream. Compatibilizers like polyethylene resins functionalized with polar functional groups can effectively promote the mixing of polyolefin resins with polar EVOH or PA polymers. In this work, we evaluated functionalized polyethylene products as a compatibilizer for the polyolefin/barrier regrind from the multilayer articles to address the utilization challenge of post industrial recycled materials.

Recycling and Sustainability: Plastic Industry Challenges and How to Face Them

Jungdu Kim, February 2020

In the last 50 years, plastic materials have become one of the most important material used in the most diverse range of end-use applications. They have their benefits as well as challenges. In the recent years, plastic has been under scrutiny for its impact on environment. To understand the plastic challenge, it is important to look at a larger picture. Many aspects must be taken into consideration when selecting material: technical properties, economical aspects and environmental impact. Understanding all criteria is key to select the most sustainable material. SONGWON will explain how it can enable the industry to overcome some of the recycling challenges. It will show the importance of sustainability and the concrete actions it is taking to continuously become more sustainable.

Material Options for TPO Waterproofing Membranes

Yushan Hu, February 2020

Fast developments in thermoplastic polyolefin (TPO) waterproofing membranes demand polyolefin systems that can help manufacturers develop custom-tailored formulations to fit specific designs, production processes, and end-use requirements. Though polypropylene (PP) based material formulations are industry norm for TPO membranes that provide a heat resistant and low cost solution, there are still unmet needs for the roofing applications. Recent advances in polyolefin catalysis allowed the polyethylene (PE) architecture that combines good thermal resistance and high flexibility at the same time. These PE based materials opens up new material options for waterproofing membranes with superior longevity, improved flexibility and broad welding characteristics.

Characterization of the Field Failure of Polyethylene Pipe Using Slow Crack Growth Tests (Paper)

Byoung-Ho Choi, February 2020

Due to its excellent mechanical, physical, and chemical properties, polyethylene is being widely used as a substitute for conventional metal pipes. Especially, in the case of polyethylene pipes, it is very important to secure long-term lifetime, therefore, various standard test methods to evaluate long-term lifetime with various fracture mechanisms have been proposed in ISO or ASTM. Among various failure mechanisms of pipe-grade polyethylene materials, slow crack growth (SCG) may be frequently occurred in actual filed conditions, so various standard test specimens such as PENT, FNCT, CRB have been developed to evaluate SCG characteristics. However, the existing SCG tests are reported to be difficult to evaluate SCG properties of the recently developed pipe polyethylene material in time due to technical issues, and to overcome these issues, a new test specimen, Stiffness-Constant K (SCK) specimen, has been recently proposed. In this study, CRB and SCK specimens were used to evaluate the integrity of polyethylene pipes that were damaged during portable water transportation. The CRB test was used for the evaluation of crack initiation characteristics of the pipe, and the SCK specimen was used for evaluating SCG characteristics of the pipe. The SCG characteristics of the damaged polyethylene piping materials were compared with the regular polyethylene materials to analyze the root causes of the failure of the polyethylene piping materials in use.