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

Abrasive Wear and Speed Relationship in Technical Compounding

Gonzalo Marulanda-Paz, Shashank G. Kasliwal, Jerry Jones, Alan Malott, Brian R. Fritz, May 2015

An accelerated wear test was performed in a 60 mm TriVolution? compounder. An aluminum element was placed before the melt zone of the extruder where wear was expected to be highest. 50 lb of an abrasive compound were mixed in the extruder and the weight of the elements was measured before and after the test. The test was repeated at different speeds. It was found that with increasing speed a rapid increase in wear per pound of material could be observed. It was determined that it is beneficial to operate the extruder at low speed and high torque as this produces less wear than operating at high speeds and low torques.

Aging of Physical Properties in Ionomers Modified with Fatty Acid Salts

John P. Bishop, James R. de Garavilla, Keith C. Andersen, May 2015

The physical property aging that occurs in ethylene-based ionomers is primarily due to the formation of secondary crystals, which proceeds slowly over the course of several weeks. Modification of ionomers with fatty acid salts, which results in useful materials for the golf ball application, causes a strong suppression of primary crystallization and enhances the relative amount of secondary crystallization that occurs. Thus, the aging that occurs in ionomers modified with fatty acid salts is more pronounced than in standard unmodified ionomers. Exposure to moisture during room-temperature aging also increases the magnitude of physical property aging in ionomers modified with fatty acid salts.

Durability Studies of Biodegradable Polymers under Accelerated Weathering Conditions

Rajendran Muthuraj, Manjusri Misra, Amar Mohanty, May 2015

Poly (butylene adipate-co-terephthalate), (PBAT) and poly (butylene succinate), (PBS) are promising biodegradable polyesters whose blends have gained great attention in wide range of applications. However, there are some drawbacks to the use of these biodegradable polymer blends in durable applications. The main disadvantage of these materials is hydrolytic degradation at elevated temperature and humidity. In this study, we have assessed the durability of PBAT, PBS and PBS/PBAT blends at 50 oC with 90% relative humidity (RH) for duration of up to 18 days. The mechanical properties of these polyesters were evaluated before and after 18 days of conditioning at 50 oC with 90% RH. The mechanical properties of the polyesters were affected with increasing conditioning time. This can be attributed to the susceptibility of ester bonds to hydrolytic degradation at elevated temperature and humidity. The hydrolytic degradation was further confirmed by scanning electron microscopy

Validation of a New Material Model for Thermoforming and Blow Molding Simulation

Benoit Debbaut, Fr‚d‚ric Fradet, Hossam Metwally, May 2015

A new material model is proposed for the simulation of thermoforming and blow molding processes. The material model is based on simple traction experiemnets where the elongation viscosity is given as a funtion of strain. To validate the material models, thermoforming experiments are carried out on typical punnet geometrey. Experimental measurements of thickness distribution at the end of the formoing process are compared to the numerical data obtained using the new material model. Material distribution comaprison show excellent agreement.

Mechanical Property Enhancement in Recycled High-Density Polyethylene (rHDPE) via Solid-State Pulverization Methods

Katsuyuki Wakabayashi, Evan Miu, Samuel Jubb, Andrew Fox, May 2015

Low-temperature, solid-state pulverization processes are explored for transformation of postconsumer, recycled HDPE (rHDPE) into value-added applications. A process called solid-state/ melt extrusion (SSME), comprising sequential solid-state pulverization and melt extrusion in a single twin screw extruder, was found to impart significant morphological and rheological changes in rHDPE, which in turn lead to improvements in tensile ductility and toughness to the level of those found in typical neat, virgin HDPE.

Core Surface Treatments to Investigate Adhesion of Thermoplastic Coatings for Aerospace Fasteners

Nicole Hoekstra, Evan Deans, Adrian Ohlfs, David Rider, Nicole Larson, Kevin Bussard, Darmo Tandjung, Panade Sattayatam, James DelPinto, May 2015

Hybrid designs consisting of a thermoplastic coating molded around non-thermoplastic cores are being investigated for use in aerospace fastener applications; however, interfacial adhesion between these materials is a challenging prospect. This paper examines the performance of tensile bars made from core materials that have been encapsulated with various engineering thermoplastics. The goal of this investigation is to determine if surface treatments on the core materials improve the peak torque and tensile load. The surface treatments explored include surface abrasion, a thermoset polyurethane primer, and an amino-silane coating. These treatments were applied to steel, aluminum, and carbon fiber/epoxy cores which were subsequently encapsulated with Polyoxymethylene (POM), Polyphenylene Sulfide (PPS) or Polyetherimide (PEI). Surface abrasion was the only surface treatment that had an effect on the adhesion between the resins and cores. Neither Polyurethane nor the silane treatment appeared to have a significant effect either positively or negatively on adhesion. The use of carbon cores proved to have a negative effect on adhesion compared to the metallic cores. Thermal analysis revealed reduced crystallinity may have had an effect on the PPS samples molded, significantly lowering their performance.

Using in Mold Pressure Sensors to Monitor the Microcellular Injection Molding Process

Levi Kishbaugh, May 2015

The MuCell ? process for producing microcellular injection molded parts is accepted as a technology for providing a more dimensionally stable part through a reduction in residual stress with increased productivity over compact molded parts. As commercial acceptance of the process grows, processors want to apply currently accepted methods of in-mold process monitoring. However, these methods do not necessarily transfer directly to the microcellular foam molding process due to significantly different in-mold pressure conditions that result from the fact that cell growth provides the packing pressure.

This paper will look at typical pressure profiles for the microcellular foaming processes and how these can be used to monitor the process for part consistency.

Blue Undertone Enhancement of Black and Grey Pp Injection Molded Parts for Automotive with Ultramarine Blues

Nathan W. Karszes, May 2015

Polypropylene has become the leading polymer for automotive applications. Black and grey are the most popular colors in injection molded parts for that industry. In the case of blacks, desired properties are: high jetness, high bluish undertone, good mechanical properties, good surface appearance, good weatherability and high gloss (depending on the application). The highest performing Carbon Blacks all alone cannot reach the target black color requested by the automotive industry. Either they have high jetness but lack blue undertone or they have high blue undertone but lack jetness. This paper intends to prove that High Performance Ultramarine Blues are a very suitable option to enhance the blue undertone of black colored PP injection molded parts while not damaging other key characteristics as jetness, mechanical properties and weather fastness. Moreover, the paper highlights the benefits High Performance Ultramarine Blues show when formulating greys by increasing its blue undertone and hence improving aesthetics by removing the yellowish undertone more associated to brownish/dirty greys.

High Performance Cellulosics for Demanding Medical Device Applications

Lea C. Paslay, May 2015

The increased use of disinfectants to combat hospital-acquired infections (HAIs) has created materials engineering challenges for medical device manufactures and designers. As disinfecting frequency increases, chemical resistance, e.g., environmental stress cracking, becomes increasingly important for materials historically used to manufacture medical devices. Although the chemical resistance requirements for materials are becoming more stringent, device designs continue to be complicated and intricate, limiting manufacturers? abilities to transition to a highly chemical resistant material if the material does not also exhibit ease of processing. This work investigates and outlines the processing and chemical resistance advantages of Eastman Tenite? propionate 360, a material manufactured from the bio-renewable resource, cellulose.

Fundamentals of Optimized Mold Cooling System Design for Injection Molds

Brenda L. Clark, May 2015

Mold cooling has evolved, just like mold machining has required faster machining, new mold cooling components are increasing efficiency of required mold cooling. Advancements through the years as specialized material selections for cooling components, conformal cooling inserts, and back again to components utilizing standard machining practices. There are new mold cooling components used to reduce machining time by reducing mold component lengths and therefore shortening plate thickness. Historically mold cooling was designed to circulate water or cooling medium through the mold base plates primarily and not necessarily within the cavities or cores. This practice usually required many different levels of cooling lines and thicker mold plate assemblies. The newer advancements create a circulation that is now optimized within mold plates and specialized within the cavities and cores to reduce mold heights.

Study of Overmolding a Foamed Thermoplastic Polyurethane Layer on a Polypropylene, Polycarbonate, or Polyoxymethylene Substrate

Hrishikesh A. Kharbas, Lih-Sheng Turng, Zhikui Ma, May 2015

Products with a laminated two-layered structure can be produced by the overmolding process. In this study, a layer of thermoplastic polyurethane (TPU), foamed by the microcellular injection molding process using supercritical fluid (SCF) nitrogen, was overmolded on a polypropylene (PP), polycarbonate (PC), or polyoxymethylene (POM) substrate. The resultant composite structure had micro?cellular foamed TPU overmolded on different polymer substrates. Further mechanical testing on samples showed that a thin layer of foamed TPU increased the strain at break and the overall toughness of the sample by more than 300 %. This property could be used to design parts, where catastrophic failure needs to be avoided. Scanning electronic microscopy (SEM) images and further shear tests show that foamed TPU has better adhesion to PC than POM and PP.

Ultrasonic Treatment of PP/CNT Composites during Twin-Screw Extrusion: Effect of Screw Configuration

Jing Zhong, Avraam Isayev, May 2015

PP/CNT composites were prepared by means of an ultrasonic twin extruder with three screw configurations at ultrasonic amplitudes up to 13 ?m to compare the efficiency of different configurations in dispersing CNT in PP. Using these screw configurations, the ambient pressure in the ultrasonic zone was adjusted in order to observe the effect of pressure on ultrasonic cavitation behavior in PP and PP/CNT composites. The results indicated that the dispersion of CNT in PP is more related to the number of kneading elements in the configuration, and less to the residence time. This was explained by the mixing effect from the flow analysis network (FAN) simulation. It was also found that at the same amplitude of ultrasonic treatment PP degraded more at lower ambient pressure. Additionally, the ultrasonic treatment increased the dispersion level of CNT in PP with the best improvement not always occurring at the highest amplitude. At the lowest ambient pressure the cavitation in the polymer matrix was intense but it had not always led to the best dispersion possibly due to the suppression of the cavitation in the agglomerates. In the screw configuration of Design 2 which related to a second highest ambient pressure, composites prepared at an ultrasonic amplitude of 10 ?m exhibited elongation at break as high as is 320% compared to 247% for the untreated composites.

Melt Temperature Measurement in Compounding

Kenneth W. Russell, May 2015

The single most important parameter in compounding polymer products is melt temperature. Melt temperature has a greater impact on product quality than any other parameter in the compounding process yet it is often overlooked in both its importance and with regard to the difficulty and necessity of proper measurement.

Melt temperature is a response variable that must be controlled within a specified range to produce the highest quality compound possible. Failure to accurately measure or maintain the proper melt temperature can lead to unexplained variability in process yields, finished product properties and customer acceptance.

This paper discusses the fundamental requirements of melt temperature measurement during compounding. Properly measuring and controlling this fundamental variable is critical to consistently producing high quality polymer compounds.

Characterization of Ternary Blends of Poly(Lactic Acid), Poly(Butylene Adipate-Coterephthalate) and Polypropylene

Arturo Rodriguez-U, Manjusri Misra, Amar Mohanty, May 2015

We discuss and report on the morphology and general properties of blends composed of poly(lactic acid) (PLA), poly(butylene adipate-co-terephthalate) (PBAT), and polypropylene (PP). It is shown that PLA can be evenly dispersed in the PP matrix. However, it appears as isolated not-anchored droplets with variable size distribution. It was also found that PLA is miscible at the interphase with the PBAT. It is followed that the PLA/PBAT phases appear as indivisible units when dispersed in the PP matrix. The morphology of the blend radically changes with the addition of a terpolymer based on ethylene and/or acrylic ester and glycidyl methacrylate as well as with the incorporation of maleic anhydride grafted PP (MA-g-PP). However, the PLA and PBAT phases remain as a unit even in presence of these additives. In general, the properties of the blends depend on the PLA or PLA-PBAT to PP ratio and their inability and/or ability to form a continuous phase.

Effects of Accelerated Aging on the Flammability of Polypropylene Based Biocomposites

Emmanuel Ogunsona, Manjusri Misra, Amar Mohanty, May 2015

A study on the flammability properties of different natural fiber reinforced polypropylene composites is done. A long term aging study by accelerated aging of the samples is performed to determine its effects on the flammability properties. These properties are determined through the limiting oxygen index (LOI) analysis and burn rate test of the samples. Results from both the LOI and burn rate tests showed an increase in the flammability of the composites as compared to the base resin, polypropylene (PP) resulting from the addition of the more flammable fibers. Under the experimental condition/ aging as studied, the flammability of the biocomposites studied by LOI remained mostly the same indicating that the composites retained their flame ignition properties. The burn rate test showed an increase in the burn rate of all the composites due to the increase in void which accelerated the heat transfer through the samples. The flammability resistance of soy meal-PP based composite was shown to be superior in comparison to other biomass filled-PP composites as studied in this work.

Microwave Synthesis of Poly (Glycerol Sebacate)

Gildas Coativy, Manjusri Misra, Amar Mohanty, May 2015

In the present work, poly (glycerol sebacate) elastomer was obtained by microwaving glycerol with sebacic acid during 128 minutes at 180øC. The power and the temperature were recorded through the reaction. They were unstable (oscillating) during the initial period of reaction (one hour), and become stable after. The step in which the power was unstable could correspond to the pre polymerization and the second step to the polymerization. Thermogravimetric analysis, attenuated total reflectance, and mass loss measurement during the process support this hypothesis.

Failure Analysis of Cross-Linked Polyethylene Pipe in Residential Plumbing and Heating Systems

Phillip Sharff, Arthur Davies, May 2015

A rash of failures in PEX-AL-PEX piping in residential domestic hot water and hydronic heating systems in the United States and Canada led to an investigation into the nature and cause of the failures. Failures, which occurred after less than 10 years of service, were characterized by blistering and splitting of the exterior pipe wall, preceded by darkening and bulging of the outer PEX layer. Laboratory examination of field samples revealed brittle microcracking of the inner PEX layer and corrosion holes in the aluminum layer precipitating hydrostatic rupture of the outer PEX layer. Tests showed that the PEX material had low gel content (indicative of inadequate crosslinking), and early depletion of the antioxidant, thus lowering the resistance to oxidative degradation. This study shows the importance of proper formulation and testing of the antioxidant package for ensuring satisfactory performance of thermoplastic pipe for the intended design life.

Rubber De-Vulcanisation Using a Planetary Extruder

Michael W. Batton, Thomas J. Malzahn, Michael Gerdon, Ralf Quack, May 2015

Elastomers are wide-meshed cross-linked (vulcanized) polymers and recycling is difficult. Thermoplastic materials can be molten by exposing them to thermal energy and put into different shapes or mixed with other ingredients to form new compounds. Elastomers do not have a melting point, in order to put them into different shapes or mix them with other materials, first the cross-linking has to be broken and the elastomer plasticized again, in other words ?de-vulcanized?. Since this is much more difficult than just melting, in comparison to thermoplastics, elastomers, due to this difficulty, were mainly reduced in size and added as filler in other materials or burned for energy and not recycled into the original raw materials. However, until today there existed no continuous economical process that has been established in the industry.

Stress-Relaxation of Polycarbonate Resins

Pierre Moulinie, Steven Owens, Daniel Williams, Yong Zhao, May 2015

The stress-relaxation behaviors of several PC-based materials are compared after being subjected to various levels of tensile strain for up to 48h. All resins tested showed decreases in stress over the course of the experiment, with most of the relaxation occurring within the first 6h. At 0.6% tensile strain, the PC-based materials we studied showed force decreases from 9-20% after 48h, much lower than what we observed for ABS or a copolyester. The consistency of our results for the PC resins studied suggests that stress-relaxation is not significant when comparing their ESCR behavior.

Microstructural Design of Porous Membrane for Effective Sound Absorption Performance

Shahrzad Ghaffari Mosanenzadeh, Hani Naguib, Noureddine Atalla, May 2015

Porous materials and foams are widely used for sound absorption purposes in different sectors. To answer the needs for light weight compact noise insulation material with high sound absorption capability, the microstructure of porous membranes can be designed for optimum performance while occupying the same volume with the same weight. Such engineered structures are known as Functionally Graded Material (FGM). In the present study, novel functionally graded foam with superior sound absorption is introduced and compared to uniform foams of the same porosity. The designed graded membrane demonstrates 20% improved performance. Foams are fabricated from bio-based polymer (Polylactide (PLA)) and are environmentally friendly.