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.
This work investigates the potential of the Weld-Bonding concept to improve the fatigue performance of friction spot joints. Therefore, friction spot joints of AA2024-T3/CF-PPS (carbon-fiber-reinforced polyphenylene sulfide) were produced with an additional thermoplastic film interlayer. Two joining conditions manufactured with low and high heat inputs were investigated. The fatigue performance of those joints was evaluated at 35%, 50% and 75% of their respective ultimate lap shear force (ULSF). It was observed that process-related microvoids decreased the fatigue strength of the joints in high cycle fatigue (HCF). Superior fatigue life of the joints with interlayer in comparison with those without interlayer was observed. At 105 cycles, typical qualification requirement of the aircraft industry, the interlayer joint showed fatigue strength of 51% of ULSF, whereas the fatigue strength of the joint without interlayer was 37% of ULSF. In the whole spectrum, the joint with interlayer showed a fatigue life approximately four times higher than the joint without interlayer.
Due to the rising demand of lightweight constructions as well as saving material, the density and weight of thermoplastic parts can be influenced significantly by using the thermoplastic foam injection molding process. The characteristic three-layer structure which is originated by the foam injection molding, a microcellular foamed core is surrounded by a non-cellular skin layer, results in a weight saving and leads to an increased specific bending stiffness with a simultaneous low tendency to warp. Whereas the established welding processes for solid parts have already achieved a high degree of perfection within the last decades, the joining of microcellular thermoplastics is a novel. The structure as well as the remaining foaming agent within the part represents a challenge for welding, which can cause great difficulties in the process. Unfortunately, there are no standards or experiences for welding such foamed parts yet.The present investigation researched the welding behavior of foam injection molded parts in comparison to their solid counterpart in dependence on fiber reinforcement and joint type. In contrast to solid parts, the welding behavior shows a significant time-dependence in case of foam injection molded parts for the various materials.
Fusion deposition modeling of PLA was studied to determine the effect of build orientation and fill-level on mechanical properties of tensile test samples. This was used to assist in the design and FDM manufacture of airless tires for the NASA rover competition. It was found that the failure and energy at break increased with increasing fill-level for flat built tensile samples, and there was evidence of crazing prior to failure. For the upright built tensile samples, the effect of fill-level on failure load and energy at break was small for fill-levels between 20% and 80%, with large increase for fill-level of 100%. However, for all fill-levels for the upright build samples, the failure load and energy at break were much lower than for the flat build samples. For tire types, the threaded tire in the upright build orientation has the highest failure load with the lowest deflection.
Many technologies exist for joining plastics, and each process has its advantages and compromises. Processes are selected based on the application and customer needs. This presentation examines vibration welding and compares it to Clean Vibration Welding (CVT), also known as vibration with infrared pre-heat. Vibration welding offers excellent strength, process speed, material compatibility, and the ability to weld large parts. However, vibration alone uses friction and high forces, resulting in particulate and unsightly “flash.” CVT adds an IR preheat step to create molten plastic prior to the vibration welding. The result is a cleaner joint with virtually no particulate, which allows more three-dimensional design flexibility and is ideal for applications with aesthetic requirements. Through material testing in a laboratory setup, engineers from Emerson demonstrate the results of CVT welding found on Branson products, and established a relationship between “changeover time” and weld appearance.
Polymer material selection for new medical device applications and also sustaining existing business presents challenge due to wide range of polymer manufacturer, grades available in the market. In addition, changing business climate results in acquisition of large corporations; causing consolidation of businesses and obsolescence of polymer grades.New methodology was presented to systematically analyze various factors for polymer equivalency. Besides engineering specifications, business factors with weighting/scoring approach were introduced to capture overall impact on business. Physical, mechanical, thermal property evaluation of polymers helps compare various resin grades available. Evaluation of Design and Process impact captures any potential risk to design, process or patient. As in many cases, changing polymer results in regulatory submission which may be lengthy process for medical device applications. In case of new product development, capturing overall impact assures new device development process can be completed in timely manner.
Accelerated aging is used throughout the Medical Device sector and other sectors to evaluate materials and devices in an accelerated fashion. If used properly, it can shave years off of validation efforts. If used improperly, it can generate misleading or completely incorrect data about the resins and products in question. This paper explores the fundamental principles and provides supporting data. It is critical to understand the four primary modes of aging for polymers: (1) physical aging (embrittlement and loss of free volume); (2) chemical aging, which includes oxidation, chemical damage, sterilization, etc.; (3) sustained strain cracking, creep rupture, and environmental stress cracking; and (4) fatigue. For sustained strain or sustained load environments, stress relaxation and creep are also key factors. A case study is presented for polycarbonate and copolyester resins that are undergoing physical aging, sustained strain cracking, and environmental stress cracking (ESC), and a model presented to account for the various factors.
Drug delivery devices like multi-dose pens and auto-injectors help patients manage their conditions in the comfort of their own homes. The drug inside these devices is traditionally packaged in a glass cartridge or syringe. Polymer containers are available alternatives for drug delivery devices but their substitution for glass containers is complicated by regulatory, cost, and practical drug filling process considerations. This talk will highlight the current state of polymer drug container technology, identify situations when glass packaging issues are solved by polymer containers, and review the key selection, processing, and regulatory requirements polymers must meet in this demanding application.
Implantable thermoplastic polyurethanes (TPU) have been utilized in the medical industry for decades due to their combination of biocompatibility, abrasion resistance, and processability. Attempts to improve the biological stability of TPUs have been an area of intense activity and have resulted in a number of different formulations [1-5]. It has been observed that the nature of the soft segment in the TPUs is the primary factor in controlling the biostability of the final polyurethane. In many studies [5 – 9] it was seen that siloxane based soft segments presented the best performance in in vitro and in vivo tests and materials based on siloxane based soft segments are most suitable for long term implant applications. In this study, the results from various in vitro and in vivo tests are put together focusing on the performance of a siloxane based TPU (Optim) in cardiac lead insulation applications. The performance of Optim is compared with other materials, primarily polyether based TPUs.
Thermoplastic polyurethanes (TPU) are a common choice as a biomaterial for many medical devices, especially devices requiring long term implantation. Many of the desirable properties of TPUs as biomaterials are directly related to their unique microstructure, containing both hard and soft polymer segments. However, this microstructure can be influenced by a number of factors present both before and during the device manufacturing process. Because components for medical device applications are held to a high quality standard that requires consistency between parts, changes to the polymer microstructure can have a significant impact on the completed part. Further complicating their processing, medical device parts are often smaller and require a lower throughput in production than non-medical device parts. In this study, the effects of storage conditions, drying conditions, and process settings were evaluated in order to understand how changes in these factors impact important material properties.
Medical tubing extruded of a commercially-available PEBA (poly(ether-b-amide)) copolymer resin, namely Pebax® 4033 SA01 MED, was surface-extracted using a typical nonpolar solvent, n-hexane. After the completion of solvent evaporation, the obtained extractive solution was dried into waxy specimens, which were then chemically characterized using ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) and GPC (gel permeation chromatography) methods. It is determined that the surface extractives of medical tubing contain the oligomeric polyether reactant residual existing in the PEBA resin and various low MW (molecular weight) species rich in polyether segments. Thermal analysis on the as-received tubing and the PEBA resin was conducted using DSC (differential scanning calorimetry) technique. The relevant results suggest that the surface extractives, though they are loosely attached onto the surface of medical tubing, are fully miscible with the bulk PEBA material upon melting. The mechanism for the formation of the surface extractives during tubing extrusion and applicable effects on post-extrusion process development for making medical devices are discussed.
Micro molding drug delivery devices to micron tolerances requires extreme fine tuning of existing injection molding technologies. Unlike conventional or macro molding, micron tolerances require unconventional tooling, molding, automation, and metrology practices to achieve Cpk of 1.33 or better. This paper identifies and analyzes these 4 key factors to molding parts to micron tolerances: 1. Tooling precision2. Micro Molding Process Control 3. Micro automated assembly4. CT scanning metrologyCase studies of micron tolerances for implants and drug delivery devices (transdermal patches, injection, and slow release devices) will be presented.
Ethylene Vinyl Acetate Copolymer: Review of high value pharmaceutical applications The potential for use of polymers in controlled drug delivery systems has been long recognized. Since their appearance in the literature, a wide range of degradable and non-degradable polymers have been demonstrated in drug delivery. The significance and features of ethylene-vinyl acetate (EVA) copolymers in initial research and development led to commercial drug delivery systems. This review examines the breadth of EVA use in drug delivery, and will aid the researcher in locating key references and experimental results, as well as understanding the features of EVA as a highly versatile, biocompatible polymer for drug delivery devices.
This study sought to produce effective antimicrobial catheters via bi- layer extrusion. Catheter samples were extruded with inner and outer layers of biocompatible thermoplastic polyurethanes (TPU). The inner layer of low durometer was compounded with PureEaseTM processing additive, and the outer tube with Agion® AD anti-microbial zeolite. Agion® concentration, outer layer tube thickness, and processing thermal history were considered. The antimicrobial bi-layer catheters were highly effective at inhibiting cell division and reducing the number of organisms by a 5 log reduction for CRE, and 3 log reduction for MRSA. The thickness of the outer tube did not influence the catheters antimicrobial effectiveness. It is concluded that bi-layer extrusion is a viable method for obtaining highly efficient, low-cost antimicrobial catheters.
Ensuring product integrity across every component, subsystem, and system of a medical device has never posed a greater challenge. Engineering organizations are addressing this challenge by increasing the use of modeling and simulation tools across the entire product architecture and throughout the product development cycle – from functional analysis through detailed design to system verification. This approach necessitates the use of a broad array of physics modeling and other software tools. And while each individual tool may be effective at performing deep comprehensive analysis, product groups are often operating in silos, each using their own set of tools, engineering processes, and associated expertise to understand their areas of product performance. This approach can delay the understanding of the complete system, leading to delayed timelines, redesigns, and other unwanted outcomes. Using an insulin pump as an example, this talk will review how digital prototyping and systems engineering can address the needs of interdisciplinary product development teams. This more holistic approach enables engineers from diverse backgrounds to share expertise and experience as they design an optimal product.
There is growing interest in the identification, quantitation, and risk assessment of leachable species and degradation products of polymeric medical device components. Degradation and extractable & leachable studies usually follow a two-step program. In the first step, an exaggerated extraction is conducted using simple solvent conditions more aggressive than those anticipated to be realized in a clinical setting in order to determine the complete extraction profile and to identify the potential extraction compounds, desired or undesired. In the second step, a leaching study is conducted that attempts to simulate the clinical environment of the target application. The simulated leaching environment often comprises a more complex biological matrix than those used for extraction, which in turn complicates the chemical analysis assays used to identify and quantify the leaching materials. In this presentation, we show examples of studies that required a more detailed testing assay to identify and quantify compounds coming from implanted medical devices.
Purpose: Evaluate the feasibility of compression molding manufactured silicone rubber which the surface infiltrative characteristic is super hydrophobic, realize and compare the effect of super hydrophobic surface to several cellular biological characteristics of human lens epithelial cell line SRA01/04 with ordinary hydrophobic surface. Methods: The silicone rubber of super hydrophobic micro surface and ordinary hydrophobic surface were manufactured by Vacuum defoamation and compression molding, and tested the property of the surface by measuring contact angle, electron microscope scan experiment and evaluation transparency. In vitro, the effect of super hydrophobic silicone rubber on cell proliferation, cell adhesion ability and cell morphological changes by SRA01/04 cells were examined. Results: The surface contact angle of super-hydrophobic silicone was greater than that of smooth silicone (153.8 vs. 116). The super-hydrophobic surface exhibited a micron-scale palisade structureunder scanning electron microscopy. However, cell number per 50× microscopic field on super-hydrophobic surfaces was markedly reduced 24 and 72 h post-seeding compared to smooth surfaces (p<0.01). Cells were cuboidal or spherical after72 h on super-hydrophobic surfaces, and exhibitednumerous surface microvilli with fluff-base polarity, while cells on smooth surfaces exhibited morphological characteristics of EMT.Conclusions: This study applies compression molding manufactured the super hydrophobic surface silicone rubber successfully. The super hydrophobic surface inhibits cell proliferation, adhesion. It could be a novel way to prevent cells’ proliferation with mechanical mechanism.Acknowledgements:This project was supported by the grants from the National Natural Science Foundation of China (81400384).
Demand for high performance polymeric materials and composites continues to increase for the Medical Device Industry as minimally-invasive procedures gain popularity.With a vast library of available types and grades, polymers offer design flexibility for a wide range of applications, allowing for the development of customized solutions based on the critical design requirements for a product or application. A variety of considerations influence polymer selection such as performance, biocompatibility and other regulatory requirements, ease of secondary processing for finishing operations such as bonding or shaping or molding, among other specifications. Minimally-invasive, image-guided techniques require X-ray detection for intraoperative guidance and maneuvering. Since polymers are X-ray transparent, radiopaque (RO) fillers are incorporated into polymer matrices through compounding processes. Such mixing processes produce uniform mixtures consisting of polymer(s), functional additive(s), filler(s), yielding customized polymer compounds.This presentation reviews how high-performance polymers and their compounds meet increasingly challenging design requirements for use in medical devices.
“Part Process” Development and Validation for Multiple Machines:A Medical Device OEM Consortium formed to challenge the traditional plastic part validation process to facilitate moving a mold between machines – from Validation into Production.Much has been written and said regarding the “what and how-to” as it relates to process development and moving a mold between machines for the medical device industry. The Consortium member panel executed it - the economics of adopting this approach could potentially not only save tens to hundreds of thousands of dollars for each move (depending upon the number of molds), but the speed-to-market advantages and operations flexibility would be simply invaluable.
Engineering polymers are increasingly recognized as replacements for metal and ceramics in medical and pharmaceutical devices such as injection pens, inhalers, lancing devices and surgical instruments. These devices contain moving parts that must function efficiently with a low coefficient of friction, low noise and no wear, starting with the first activation. Regulatory requirements must also be met and Celanese has developed the portfolio of Medical Technology grades to address this requirement.Medical device performance has to be achieved in complex design environments including movements against different types of materials that are operating across a range of temperatures and chemical environments and a range of speeds and forces in operation. Their light weight and dimensional accuracy is achieved through precision molding. This, combined with good sliding performance, distinguishes these plastics from metal. Furthermore, appearance and functional color techniques are necessary to ensure device functionality. For example, for the application of a marking on a device to assure correct calibration and dosing, appropriate Medical Technology polymers have to be applied. This paper reviews traditional polymers with and without external lubricants. It also gives an overview of tribologically modified polymers that operate effectively without the aid of external lubricants including a new concept for mass colored plastics.
Over the years, the need for multifunctional medical tubing systems have grown tremendously subsequently increasing the precision tubing design and manufacturing consideration. The requirements smaller dimension along with enhanced mechanical and flexibility characteristics have resulted in elevating the complexity in manufacturing and design considerations, hence higher cost per device. A research gap exists in scientific understanding on the use of nanofillers to match similar characteristics medical tubes. This lack of understanding and industrial transition exists due to filler agglomeration at low aspect ratio and uneven dispersion within the polymer matrix. This study investigates ability of supercritical fluid technology to exfoliate graphene filler particles in order to enhance the mechanical, homogeneity and even dispersion of particles within Pebax matrix. A one step direct scCO2-assisted extrusion to exfoliate and provide even dispersion was demonstrated. These properties were verified using thermomechanical and electrical characterisation.
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