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Medical Plastics

Effects of Ionizing Irradiation on Mechanical Properties of Polymeric Medical Devices
Md Kamrul Hasan, Ph.D., March 2023

The chemical and physical effects of ionizing radiation on polymeric materials is reviewed with a primary focus on radiation sterilization of disposable medical device materials.

Chemical Formulary, Dual UV & Heat Curability, and Thermo Property & Behavior of a Medical-Grade, UV-Curable Epoxy Adhesive
Xiaoping Guo, Ph.D., March 2023

In the present paper, we have studied thermal properties and thermo-chemical stability of a medical-grade adhesive comprised of a cationic, cycloaliphatic epoxy resin system by using differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA) techniques. Then, we have explored UV curability of the adhesive by performing a series of the UV-cure experiments using special photo- DSC (or p-DSC) technique and investigated relevant relationship of resultant thermal properties and thermochemical stability of such UV-cured adhesive materials with the underlying UV irradiances during UV curing. Thereafter, we have further examined thermal curability for various post-UV cured adhesive materials by conducting a series of the thermal-cure experiments and measured the ultimate glass transition temperatures of resultant adhesive materials at various “fully-cured” states with using a conventional DSC technique. According to these thermal analysis tests, p-DSC UV-cure experiments, and DSC thermal-cure experiments, we are able to thoroughly understand effects of UV irradiances applied during UV curing on dual UV-thermal curability and resultant thermal properties of various resultant adhesive materials at the “fully-cured” solid states to provide pertinent scientific insights on relevant adhesive handling and processing operations in making medical devices.

Justification of a Molten Polymer Process Change to a Legally Marketed Medical Device Via Comparative Statistical Analysis of Thermal Stabilities of Material
Xiaoping Guo, Ph.D., March 2023

In an attempt to attest and justify that a polymeric medical device as possibly affected by some polymer process change(s) of device manufacturing would be substantially equivalent to relevant legally-marketed counterpart in view of its biological safety and functional effectiveness, a practical approach for statistically evaluating inherent thermo-chemical stability of polymer, namely activation energy of thermal degradation that is closely dependent of the underlying thermal history of device manufacturing, is proposed in compliance to relevant regulations and industrial guidelines. Accordingly, a series of thermogravimetric analysis (TGA) experiments can be comparatively conducted per ASTM E1641 standard practice and then kinetically studied to determine the measured activation-energy means for some “test” polymer samples taken from affected device, compared to some “control” polymer samples taken from relevant legallymarketed device, using the so-called Ozawa-Flynn-Wall analytical method. The statistical equivalence or superiority of affected device, compared to legally-marketed device, can be then technically assessed by performing the pertinent two-sample (Welch) t-test on any statistical differences in the so-measured activation-energy means between the affected and “control” polymer samples.

Multicomponent Injection Molding With Liquid Silicone Rubber (LSR) and Acrylonitrile-Butadiene-Styrene (ABS) for Medical Device Applications
Mohammad Ali Nikousaleh, Ralf-Urs Giesen, Ph.D., March 2023

Multi-component injection molding of liquid silicone rubber (LSR) with thermoplastics, such as PBT or polyamide, is used in the manufacturing process for many components in the automotive industry and in the field of sanitary technology. Due to its hypoallergenic properties, biocompatibility, and resistance to the majority of liquid medications, liquid silicone rubbers are a promising alternative material for use in medical applications. They can be used over a wide temperature range and they are physiologically well tolerated and can be sterilized in various ways. Standard thermoplastics, such as acrylonitrile butadiene styrene (ABS), cannot be overmolded with silicone rubbers in injection molding because of their low heat deflection temperature. With the right production method that combines the processing of silicone rubber and thermoplastics, it would be possible to replace the formerly expensive production and assembly of individual components. Such an integrated production technology makes it possible to realize high-performance new products economically and at the same time, to improve product safety for the patient through simplified, more highly automated and higher-quality production. In this investigation, we applied ABS grades, approved for medical applications, to show how ABS-LSR test specimens regarding the VDI guideline 2019 could be produced using variothermal mold heating and special surface treatment of ABS. Here we will show the development and challenges of a new 2C-molding technology for LSR – thermoplastic parts. For the quality of the later product, the adhesion between thermoplastic and LSR is the decisive feature and depends not only on the injection molding process, but also on the material pairing and the treatment process. Here, we succeeded to manufacture multifunctional products for medical devices through various partial pretratment methods of the thermoplastic surface. In addition, the effect of sterilization (gamma and eto) and artificial aging (humidity and temperature) and of such components on the adhesive bond is indicated.

Leveraging the Chemistry and Properties of Polycarbonate to Achieve Maximum Productivity, Lower Energy Consumption, Reduce Waste and Lower Carbon Footprint
Joshua Wagner, March 2023

In addition to polymers based on non-fossil feedstocks that help reduce carbon footprint or blends that incorporate recycled content to reduce waste, there additional strategies a manufacturer can pursue to further lower energy consumption and material usage. In this presentation, we delve into polycarbonate materials chemistry and property profile to point out cases where the material and process innovations come together to maximize productivity and lower energy consumption or even lower material consumption to reduce waste. How these fit together in a greater context of plastics manufacturers looking to be part of an emerging circular economy will also be discussed.

Investigation Of The Induced Electric Field Molecular Alignment Of Sliver-Based Solvate Ionic Liquid (SIL) And Silver Nanoparticles (AgNPs) In A Toughened Epoxy Resin Composite
Ahmed Al-Qatatsheh, Anna Sokolova, Nishar Hameed, March 2023

We report using the coordinated silver (I) complex based on SIL in a toughened epoxy resin composite to enable electrical and thermomechanical properties. The toughened epoxy resin was aligned at the molecular level utilizing an electric field, demonstrating a relatively high electric conductivity, energy storage, and rapid curing behaviour that can save energy, reduce unnecessary heat, and optimize capital and operating costs. Applying Small Angle Neutron Scattering (SANS), our work thoroughly studied the effect of alignment changes on the silver (I) complex and AgNPs under an applied electrical field and assessed the stability of the alignment after the electric field was constantly removed. Furthermore, the in-situ SANS investigation of the kinetic effects under external impulse influence helped identify the clusters of silver under an external electric field in various composite matrices. This technology can be used for accurate noninvasive blood circulation; increasing material electrical conductivity by applying induced electric field molecular alignment can tremendously increase sensor sensitivity. This approach opens the door to the next generation of thermoset polymers with multifunctional properties.

Melting Performance Analysis Of A Single-Screw Extruder With A NSB Screw
Xiaofei Sun, Ryan A. Pratt, Mark A. Spalding, Jeffery A. Myers, Robert A. Barr, Aaron F. Spalding, June 2022

A recent design of a new screw referred to as the No Solid Bed (NSB) screw was introduced and the initial operation was presented [1]. This new screw has channels in the transition section that do not allow a compacted solid bed to form. The data presented here compliments the data that was previously published.

Relative Humidity Effects on Accelerated Aging of Medical-Grade Polymers: Should ASTM F1980 be Revised to Recommend Constant RH Instead of Constant Moisture Content?
Aniruddha Palsule, Rachel Jacobs, Martin Gibler, Robert J. Klein, June 2022

ASTM F1980 provides a methodology for accelerated aging of sterile barrier systems for medical devices, and is also widely used as the definitive guide for accelerated aging of medical devices and pharmaceutical packaging. ASTM F1980-16, as well as previous versions going back to 2007, emphasize that when increasing temperature to accelerate aging, it is preferable to decrease relative humidity so as to maintain an approximately constant moisture content. However, there is a revision under consideration by the ASTM F02.50 committee that would dramatically change this guidance to indicate a preference (although allowing for other options) to keep relative humidity approximately constant. This change is based on somewhat limited test data and literature review published recently by Thor et al. In this paper, we perform a study looking at eight resins (PP, COC, ABS, PC/PET, Copolyester, PBT, PA66gf, PUR) that have been aged at 60C and three different RH levels to evaluate the impact on aging. Our findings to date indicate that: (i) yes, it is likely that RH should be held constant when increasing temperature in order to keep moisture constant in the resins at a similar level; and (ii) for the medical-grade resins evaluated here, RH level does not significantly impact the physical aging mechanism. We also recommend that further accelerated aging studies are performed to more thoroughly evaluate the impact of moisture content on Q10 factors, corrosion rates, and other endpoints before this dramatic change is made to the ASTM F1980 standard.

Automated Optimization Of A Block-Head-Mixer With An Innovative Algorithm
Felix Vorjohann, Lucas Schulz, Mirco Janßen, Reinhard Schiffers, June 2022

CFD-Simulations are a common tool to design and optimize mixing elements. The manual evaluation and experience-based derivation of an optimized geometry is still an iterative process which is time consuming. In this paper an automated algorithm is developed and tested for a mainly distributive Block-Head-Mixer. To automatically evaluate the flow field of each geometry variant, quality criteria are introduced which enable the assessment of the mixing capability. The investigation showed that the quality criteria are suitable to evaluate the flow field and an optimized candidate compared to a starting geometry could be found automatically.

Development Of An Inline-Measurement System Of The Surface Temperature Of Square Hollow Profiles
Jonas Köllermeier, Volker Schöppner, June 2022

In polymer extrusion, the die temperature is normally set to the recommended temperature in order to reach a homogeneous melt. Nevertheless, the measurement of the melt and surface temperature of the product leaving the die is not state of the art due to the difficulty of an inline - measurement. As a consequence, the product temperature leaving the die is assumed as the set die temperature. Therefore, this article aims to engineer an inline-measurement system of the surface temperature of square hollow profiles immediately after leaving the die. First, two objective quality criteria to define the thermal melt homogeneity, named weighted melt temperature and radial temperature, are introduced. After that, experimental investigations are carried out for two different types of polyolefin polymers with the variation of several process parameters such as the screw speed and the die temperature. In order not to distort the product, the developed construction is based on a contactless measurement system using infrared pyrometers to measure the average surface temperature on each side of the profile. After all, rules of behavior are derived from the process and correlations between the investigated process parameters and the melt quality as well as the surface temperature are identified.

Production Of Flexible Thermally Conductive Thermoplastic Pipes By Orientation Of Filler Particles
Kevin Buchalik, Reinhard Schiffers, André Kayser, Marco Grundler, June 2022

Pipes for heat exchanger systems are usually made of metals to achieve a high level of energy transfer. Polymers, in comparison, save weight and costs and are suitable for use in corrosive and chemically aggressive environments. However, for many applications the comparatively low thermal conductivity of polymers is a disadvantage. To overcome this, polymers are usually mixed with high amounts of fillers, which transport the heat through the pipe wall. But the use of high filler ratios influences the mechanical properties of the pipe significantly. The aim of this paper is to develop a concept for a pipe extrusion die which aligns the filler particles in radial direction, so that the anisotropic material properties of the compound can be utilized and thus the amount of filler can be reduced. Consequently, the flexible material properties can be maintained as far as possible. Several die concepts are presented and their influence on the thermal and mechanical properties of the pipe are compared.

Scale Up Optimization Of Optical Nanolayer Films: Improved Thickness & Compositional Control
Michael Cantwell, Chris Oseredczuk, Mike Hus, Joseph Dooley, Michael Ponting, June 2022

A nanolayer coextruded optical film process was scaled up and optimized to show improvements in the thickness and compositional control at production level throughput rates. Adjustment of processing temperatures, implementation of online continuous gauging and automatic die lip adjusting equipment, and upgrades to the cast film pinning system led to improvements of film thickness control. A unique profile control scheme utilizing only the middle layer’s thickness instead of the total film thickness has been successfully utilized to control the critical layer’s thickness. Automation and optimization of the extruder’s feeding system provided compositional control capable of meeting tight quality specifications. With these improvements, production scale throughput rates of high-quality optical cast film capable for unique gradient refractive index (GRIN) optical applications were demonstrated.

Three Trends in Healthcare Adhesives
Joanne Moody, May 2021

With an aging global population growing, the demand for new healthcare products and telehealth systems will increase. The FDA aims to advance innovation and development in digital health while ensuring patient safety and effectiveness. Adhesives are critical in the new remote monitoring products, such as the small wearable devices that stick to skin. In addition, surgical adhesives are replacing stitches, and robotic surgical systems are rising. With healthcare adhesives, there are additional challenges in safety, performance, biocompatibility ISO 10993, and cost requirements. This paper reviews three healthcare adhesive trends: (1) topical skin adhesive patches, (2) tissue adhesives, and (3) medical device assembly and equipment adhesives.

Adhesion of Overmolded TPE to FR-PC/ABS: Effect of TPE Properties and Substrate Color Recipe
Pierre Moulinié | Godwin Suen, May 2021

Various grades of Thermoplastic Elastomer (TPE) were overmolded onto a FR-PC/ABS blend prepared with several different color recipes and tested for adhesion. All combinations prepared exhibited adhesive failure with a standardized peel test, yet showed relatively high average peak peel forces that ranged from 3.74-4.07 N/mm, which agreed well with literature values. Different color recipes for the substrate had no discernable effect on peel forces. Two-step overmolding of TPE using pre-molded (and therefore conditioned) substrates gave no significant difference to those prepared with direct 2-shot overmolding.

Effect of Molding Parameters on Orientation and Tensile Properties of Polycarbonate
Pierre Moulinié | Isaac Platte | Ravishankar Ayyar | Kyle Kulwicki | Louis Somlai, May 2021

The tensile properties of two different molecular weight polycarbonates were examined in relation to injection-molding conditions, such as low and high temperatures & speeds (affecting injection pressures), that were beyond those recommended by the supplier. We found conditions that prompted higher injection pressures led to decreases in tensile elongation-at-break, with more significant decreases for higher molecular weight (and high viscosity) PC. Examination of molded samples under polarized light suggested higher degrees of molded-in stress along the flow length as an important contributor to the changes in elongation at break. Additionally, corresponding to the elongation at break, the onset of strain hardening decreased under injection molding conditions that produced higher injection pressures.

Effect of Rubber Surface Treatment on the Properties of Rotomolded Thermoplastic Elastomers
Roberto C. Vázquez-Fletes and Denis Rodrigue | Gustavo Gallardo-Paniagua | Erick O. Cisneros-López | Pedro Ortega-Gudiño | Rubén González-Núñez, May 2021

Thermoplastic elastomers (TPE) are a combination of a rubber and a thermoplastic to create a recyclable blend combining the properties of both resins. The objective of this work is to produce and characterize rotomolded parts based on polyamide 6 (PA6) as the matrix and recycled ground tire rubber (GTR) as the dispersed phase. In order to improve the adhesion between PA6 and GTR, and consequently the mechanical properties of the resulting TPE, a treatment with formic acid was used on the GTR surface. All the samples were initially mixed via dry-blending using 5 and 10% wt. of GTR and then rotomolded. For these concentrations, successful rotomolded parts were produced to report on their morphological and mechanical properties. The results show that increasing the GTR content led to lower tensile modulus and tensile strength, but higher elongation at break and impact strength compared to the neat matrix.

Polypropylene/Ground Tire Rubber (PP/GTR) Composites Produced Via Rotational Molding
Y. Dou | D. Rodrigue, May 2021

In this work, polypropylene (PP) was dry-blended with ground tire rubber (GTR) to produce composites by rotational molding. In particular, the effect of GTR content was investigated to modify the mechanical properties of the PP matrix. Each compound was characterized via morphology, density and mechanical properties (tensile, flexural and impact). As expected, the results showed that all the mechanical properties decreased with increasing GTR concentration due to its low modulus and strength. Also, the crosslinked structure of the GTR particles is believed to limit the interfacial PP-GTR interaction, thus also limiting mechanical stress transfer.

Chemical Resistance Testing of Polycarbonates and Blends With Hospital Disinfectants and Cleaners
Paul Nowatzki, May 2020

We tested an array of hospital surface disinfectants and cleaners for compatibility with several polycarbonate-based thermoplastic materials commonly used in healthcare equipment. To assess compatibility, we exposed tensile specimens to cleaners while under flexural strain, and then checked for cracking and tensile property retention. The results illustrate which cleaners are the harshest and which materials are the most chemically resistant. We also observed that periodic wiping and drying is frequently more damaging than the traditional test method of continuous wet exposure.

Development of Innovative Biocidal Nanoparticles For Use In Plastics Technology
Ruben Schlutter, May 2020

Increased demands on high-end materials focus the development on new functionalities such as biocidal effects, which are made possible by property changes in the nanoscale range of existing materials or by a combination of different material classes. Therefore nanoparticles, based on transition metal oxides have been synthesized in order to reach biocidal properties on plastic part surfaces. The influence of the nanoparticles on the thermal and mechanical properties have been characterized as well as the biocidal properties of the plastic part surfaces and of the nanoparticles itself.

Effect of Photoinitiator Concentration and Curing Time on Soybean Polyethylene Glycol Resins
Kaetlyn Byers, May 2020

Bioprinting, a subset of additive manufacturing, utilizes bioinks, which is a combination of biomaterials and live cells, to produce functional tissue. Soybean oil is a plant polymer with promising biomaterial properties for development as a bioink. Soybean oil is low cost, has excellent biodegradation, biocompatibility and low immunogenicity.Additionally, suboptimal soybean properties such as mechanical and bioactive properties can be altered and improved when combined with other polymers. The curing of resins formulated from a combination of soybean oil epoxidized acrylate and poly(ethylene glycol) diacrylate was investigated with different concentrations of the photoinitiator diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide/2-hydroxy-2-methylpropiophenone, blend (DPH) and at different curing times. Visual observations of the cured resins indicated that as the photoinitiator concentration and curing time were varied, the resins exhibited changes in flexibility and rigidity / brittleness.

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