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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Polymer Analysis
Failure Analysis of Products with Plastic to Metal Threaded Connections
Gaurav Nagalia | Anand R. Shah, April 2021
Many products and assembled systems of different products require the use of threaded plastic to threaded metal connection to provide the mechanical integrity required for the service application. While there are design guidelines and industry acceptable standard specifications related to the design of the different thread profiles used in the connection of plastic to plastic or connection of metal to metal threaded components, there is very limited information available for designing a plastic to metal threaded connection. Generally, designing a mechanical connection between a plastic threaded component and a metal threaded component is discouraged. However, in some applications this cannot be avoided and as such the lack of understanding related to plastic to metal threaded connection leads to product failures when such connections are made or designed improperly into products. This paper reports two case studies of product failures where plastic to metal threaded connections contributed to product failure that caused either personal injury or personal property loss. A failure analysis investigation was conducted to evaluate the thread design in two products in which plastic to metal threaded connections were involved in the product failure. In the first case-study, the thread connection was found to be insufficient in the mechanical strength and in the second case study the root cause of failure was determined to be excessive tightening of the female threaded plastic component onto a male threaded metal component.
Failure Analysis Case Study: The Good and the Bad PVC Cable Coatings
Sergey Shilov, April 2021
Polyvinylchloride (PVC) is the most commonly used thermoplastic resin for electrical cable coatings. PVC that hardens after polymerization is not suitable for insulating and protecting wires and cables. The necessary mechanical, thermal, and electrical levels can only be reached with the addition of softeners, stabilizers, and fillers. Composition of the good and the bad PVC samples were analyzed using FTIR spectroscopy and TG analysis. It was found that ditridecyl phthalate was used as a softener in both samples. Magnesium oxide was used as a filler in one sample. The higher amount of water that present in the sample at room temperature and evolves during the first stage of PVC decomposition might be responsible for the low heat resistance of one sample.
Analytical Characterization of Commercial Foams for Consumer Bedding Applications
Praveen Boopalachandran, May 2020
The objective of this study was to characterize popular commercial bed-in-a-box mattress and visco topper foams, which are the benchmark bedding products in the market. These products were advertised as gel infused foams that offer superior thermal conductivity and support. Multiple techniques were utilized to identify the composition of the foams. In summary, the commercial “green” and “gray” bedding polyurethane (PU) foams were similar in composition, and they were made of glycerin-initiated PO/EO based polyols. It also showed the incorporation of styrene-acrylonitrile (SAN) in the polymer backbone. The isocyanate part was consistent with an aromatic isocyanate identified as methylene diphenyl diisocyanate (MDI). In addition, the blue gel polymers that were infused to these foams were polyurethane based material. Furthermore, the black particle in the “gray” foam that was advertised as heating wicking material was graphite-based additive.
Foaming of PVC Using Ultra High Molecular Weight Acrylic Processing Aids
Manoj Nerkar, May 2020
Polyvinyl Chloride (PVC) foaming was studied as a function of high molecular weight acrylic processing aids. It was demonstrated that an ultra-high molecular weight processing aid is 25-30% more efficient than relatively lower, but still high, molecular weight acrylic processing aids. The higher Mw processing aid provided similar foaming performance at lower loading levels. Foaming reduced the density of PVC compounds to 0.32-0.34 g/cc. More than 1000% expansion was achieved in the melt extrusion process using a chemical blowing agent. Fusion characteristics were also studied. Fusion times for initial fusion peaks were in the range of 42-44 seconds while the fusion times of the second fusion peaks were in the range of 74-94 seconds. The higher molecular weight processing aid maintained fusion characteristics of PVC compounds, warranting no significant changes in extrusion process.
Morphology and Mechanical Performance of Pipe Grade HDPE Exposed to Chlorinated Water
Andrew Hagen, May 2020
Thin samples of a pipe-grade polyethylene with a bimodal molecular weight distribution were exposed to 5ppm 70C chlorinated water for up to 3000 hours. The samples were characterized by tensile tests, size-exclusion chromatography, infrared spectroscopy, and differential scanning calorimetry. Throughout exposure, the molecular weight data showed evidence of degradation: weight-average molecular weight was reduced, and a shift in the molecular weight distribution from a bimodal to a unimodal distribution (decreased dispersity). After 2250 hours of exposure, brittle behavior was observed, in which the average elongation at break was 12%. At this level of degradation, the weight-average molecular weight was 9 % of its undegraded value, and the crystallinity had increased from 70% to 85%. Average tensile strength was reduced from 31.8 to 16.6 MPa. The data imply that the presence of short-chain branching may inhibit chemicrystallization and subsequently delay the onset of brittle behavior.
Novel Method of Compounding Cellulose Nanocrystal Suspensions into Polylactic Acid and Polyvinyl Acetate Blends
Ronald Sabo, PhD, May 2020
Cellulose nanocrystal (CNC) suspensions were compounded into blends of poly(lactic acid)(PLA) and poly(vinyl acetate)(PVAc) using a novel wet compounding approach in which drying and compounding werecarried out simultaneously. The resulting CNC/PLA composites were compared with those produced using a more traditional method of freeze-drying CNC suspensions followed bymelt-blending into PLA. CNCs in wet compounded composites appeared to be well-dispersed in the PLA/PVAc blends, and films extruded from these compounds exhibited high transparency compared with melt-blended composites. Gel permeation chromatography indicated that molecular weight degradation due to wet compounding was comparable to that from melt blending. The formulation, including surfactant modified CNCsand PVAc processing aids, played a significant role in the dispersion and properties of the nanocomposites. The elimination of a stand-alone drying stepfor cellulose nanomaterials can potentially overcome some of the challenges associatedwith producing thermoplastic cellulose nanocomposites and help advance commercialization of these materials.
Reverse Engineering and Failure Analysis of Materials and Polymers Using Infrared and Raman Spectroscopy
Sergey Shilov, May 2020
Failure analysis and reverse engineering can greatly expedite product development. Infrared and Raman spectroscopy is the among the most powerful tools for this application because each molecule has a unique infrared and Raman signature. Infrared and Raman microscopy was successfully used to identify foreign particles on elastomers and to depth profile multilayer polymer film. Details of the measurement techniques are discussed.
Reduced Order Kinetic Model for Corrosion of High-Density Polyethylene in Bleach Solutions
Susan Mantell, May 2020
A reduced order kinetics model is proposed for the corrosion of polyethylene in bleach solution. Hypochlorous acid (ClOH) is considered as the oxidizing agent which is formed from the hydrolysis of bleach. The model simulates the diffusion of ClOH into the non-polar polymer matrix followed by its dissociation into radicals. The reaction between the radicals and the polymer is phenomenologically modeled using an ordinary differential equation. The model is suitable for coupling with mechanical models for life-time analyses of polymers members under mechanical loading and exposure to corrosion. The model captures the effect of the chain oxidation process which causes the accelerated aging of the polymer.
Studies of Material Properties of Htpb- Based Composite Under Aging Conditions
Jaehee Jeong, May 2020
Hydroxyl-terminated polybutadiene (HTPB)-based rubber composite is usually used for solid propellant binder. In order to investigate the long-term material properties in the storage environment, it is recommended to set up the conditions refer to MIL-STD-810G. After aged for 100, 200, 300 hours with different temperature and humidity conditions, the key properties, i.e. tensile test, Fourier transform infrared spectroscopy (FTIR), and surface morphologies were examined. Also, by using these experimental data, diffusion model using finite element method suggested. This study will be useful for the life evaluation of HTPB-based composites considering diffusion.
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