1:30 pm – 6:30 pm:
(Moderators: Jennifer Hoffman and Todd Menna)-Room S322
1:30 pm – 2:30 pm:
KEYNOTE: Tan Delta – The Dimensionless Property That Tells You Almost Everything You Need To Know About A Polymeric Material
Michael Sepe, Michael P. Sepe, LLC
Dynamic mechanical analysis (DMA) has been a useful technique for characterizing polymeric materials for over fifty years. Often material comparisons focus on elastic modulus since it is a property similar to something we are familiar with from published data sheets. But a less well known property that arises from DMA, tan delta, provides immense insight into a wide range of behaviors in polymers. This paper will review the definition of this property and illustrate some examples of how it can be used to assess the relative performance of polymeric materials for short-term and long-term use.
2:30 pm – 3:00 pm:
Fractography: The Science & Art of Determining How Plastics Break
Farzana Ansari, Senior Associate, Exponent
In recent decades, the engineering industry has seen a stronger emphasis on cost- and energy-efficient materials. As a result, polymers have increasingly been adopted in load-bearing applications, replacing traditional “engineering materials” such as metals and ceramics in multiple industries, from aerospace vehicles to medical devices. With this transition comes an increased need for understanding how such load-bearing polymers inevitably fail, especially with respect to cracking and fracture. Fractography – the science and art of “reading” fracture surfaces – is a powerful failure analysis tool for dealing with fractured plastic components. Fracture surface features can tell a story regarding the stress state and environment a polymer experienced during fracture, potentially eliminating hours of exploratory testing to replicate the exact failure mechanism.
3:00 pm – 3:30 pm:
Failure Analysis Using FT-IR and Raman Microspectroscopy
Rui Chen, Thermo Fisher Scientific
Failure analysis is a critical aspect of product development and manufacturing across many industries, including aerospace, transportation, medical device, construction, and consumer products. There are many types of defects that may lead to product failure. For example, deviations in chemical composition and distribution homogeneity could cause failures of many polymer and plastic materials. Contaminations such as particles and/or inclusions are another common cause for material failures. Holistic failure analyses often require a multi-faceted and multi-technique approach to product and material investigations. Vibrational spectroscopy, including both FT-IR and Raman, has long been an integral part of the toolbox for failure analysis. Infrared and Raman spectroscopy can provide fast and accurate identification of the chemical composition, both organic and inorganic, of the defective product materials. For those extremely small defects that require a spatially resolved analysis, FTIR and Raman microscope allows for spectral measurement on the sample with high spatial resolution and thereby reveal the chemical composition of the area of concern. In this presentation, the fundamentals of FT-IR and Raman spectroscopy will be reviewed with a particular emphasis on microscopy and sampling techniques. A wide range of real-world failure analyses using FT-IR and Raman will be presented. The complementarity between FT-IR and Raman will also be discussed.
3:30 pm – 4:00 pm:
How to use Thermoanalytical Methods for Failure Analysis
Tobias Pflock, NETZSCH-Gerätebau
Thermal analysis is one of the most prominent techniques to find out about failures of plastic parts. The talk will comprise the most important methods such as DSC (Differential Scanning Calorimetry), TGA (Thermogravimetry), TMA (Thermomechanical Analysis) and DMA (Dynamic Mechanical Analysis) and relate them to following application questions: • How can I identify polymers better in failure analysis? • How can I find out about the composition of a polymer compound? • What is the reason for part shrinkage after processing and what does that have to do with internal stresses? • How does temperature influence the mechanical performance of my part and what does a glass transition really look like?
4:00 pm – 4:30 pm:
Investigation of the Efect of Stabilizer System, Medium and Teprature on the Fatigue Crack Growth Resistance of Polypropylene for a Proper Material Selection
Joerg Fischer, Johannes Kepler University Linz – Institute of Polymeric Materials and Testing
For a proper selection of materials for solar-thermal applications, the failure behavior of various polypropylene (PP) grades was investigated by fatigue crack growth (FCG) experiments. The four tested material grades differed in their stabilizer system. To determine the effect of environmental media (chlorinated water with a chlorine content of 5 ppm, air and deionized water) and elevated temperatures (95°C and 80°C), cracked round bar specimens were tested on an electro-dynamic testing machine equipped with a special desigend media containment. Tests at all environmental conditions revealed a significant influence of the stabilizer systems on the FCG resistance. While at all conditions the stabilization with a hindered amine light stabilizer resulted in the best FCG behavior, depending on the environmental loading different PP grades showed the worst FCG resistance. In terms of media dependence of the crack growth behavior, for all PP grades, the best and worst FCG behavior were obtained in deionized water and chlorinated water, respectively. Results received from tests under two different temperatures showed that the FCG resistance decreased with increasing temperature in all tested environments and for all PP grades.
4:30 pm – 5:00 pm:
Fracture Properties of HDPE Exposed to Chlorinated Water
Susan Mantell, University of Minnesota
HDPE is often used in applications that include both structural and environmental loads. In this study, the effect of an oxidative environment on HDPE mechanical performance is evaluated. Thin 75 micron HDPE samples are exposed to 5ppm chlorinated water at 70C for up to 1250 hours. Changes in polymer morphology as a function of exposure time are evaluated and compared with fracture and tensile test data. FTIR data show an increase in the carbonyl group after 250 hours of exposure, while GPC data show a 20-50% loss in molecular weight after 500 hours exposure. The decrease in molecular weight is associated with shortening of the higher molecular weight chains. Essential work of fracture data and strain at break show significant loss in ductility for exposed samples. This set of data demonstrates the correlation between morphology changes and embrittlement in unimodal HDPE.
5:00 pm – 5:30 pm:
Fatigue Resistance and Failure Characterization of Glass Fiber Reinforced PA Grades
Patrick R. Bradler, Institute of Polymeric Materials and Testing – Johannes Kepler University Linz
The fatigue crack growth and failure behavior of five different short glass fiber reinforced polyamide (PA) grades was investigated on specimen level using compact type (CT) specimens. By using a testing device enabling superimposed mechanical and environmental loading, the effect of environmental conditions (23°C in air and 80°C in water), matrix material (polyamide 66 and polyamide 6T/6I) and glass fiber content (30 w%, 40 w% and 50 w%) on the fatigue crack growth kinetics was determined. Tests at 80°C in water exhibited an inferior fatigue crack growth resistance. Furthermore, for PA grades with a similar glass fiber content, an influence of the matrix material was revealed. PA grades with a higher glass fiber content indicate a better fatigue crack growth and failure behavior.
5:30 pm – 6:00 pm:
Raman Spectroscopic Detection of Microscopic Structural Changes in Polyethylene During Photdegradation
Yusuke Hiejima, Kanazawa University
Raman spectroscopy is applied to elucidate microscopic structural changes in low-density polyethylene under ultraviolet irradiation. The crystallinity estimated with the 1418 cm-1 band shows a stepwise increase at ~600 h accompanied by obvious decrease of the molecular weight, suggesting chemicrystallization. The increase of crystallinity and the thinning of amorphous layer at ~600 h lead to macroscopic shrinkage of the specimen, inducing the formation of surface cracks. It is also suggested that contraction of interchain distance and conformational changes take place gradually during photodegradation.
6:00 pm – 6:30 pm:
Any Bulging or Paneling Issues for Your Packages?
Jay Yuan, Stress Engineering Services, Inc.
Bottle Internal Pressure Analysis and Test for Hot Fill (BIPATH) is a container, closure, and process design and optimization program for packages that experience pressure or vacuum during any part of the supply chain. It was originally developed for the hot fill PET bottle design at Stress Engineering Services, Inc. (SES) in 2006. Over the years, BIPATH has evolved and expanded to encompass a wide range of container types and pressure/vacuum-prone filling, processing and distribution systems. The container types include injection/extrusion blow-molded plastic bottles and cans, injection-molded or thermoformed tubs and cups, and aluminum and steel cans. The pressure/vacuum-prone filling, processing and distribution systems include hot fill, retort, high pressure process (HPP), carbonation, nitrogen dosing, steam flushing, altitude and temperature change in distribution, air-shipping, product out-gas or oxygen consumption, oxygen/CO2 ingress or egress and plastic creep deformation over time. BIPATH calculates the package pressure allowable, which is the pressure or vacuum that the package can sustain without any unacceptable deformations or distortions, and the package pressure residual, which is the pressure or vacuum generated inside the package. The ratio of the pressure allowable and pressure residual, known as package pressure safety factor, offers bottle suppliers and brand owners a simplistic way to measure how well (or bad) the package would perform at the early stage of the package and product development process since no physical bottle or finished good samples are required for the BIPATH program. The pressure or vacuum can be better managed and optimized using BIPATH through changes in container and closure design, product content, process conditions (pressure, temperature and duration profiles), and shelf life commitment. The validity and versatility of BIPATH program in managing the pressure or vacuum has been demonstrated in real world packaging and process design and optimization since 2006. The theoretical foundation of the program and a case study are presented in this paper.