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.
During the production of injection moulded components made of semi-crystalline thermoplastics, the material is locally exposed to different thermal conditions and thermal histories. While in the injection phase the surface layer material that gets in direct contact with the cold mould wall solidifies at cooling rates of up to 700 K/s, the core layer material solidifies at cooling rates of ~1 K/s, especially for thick-walled components. This results in variation of crystallisation degree throughout the thickness of the component. Typically, an increasing crystallisation degree is related to an increase in thermal conductivity of a polymer. Since the heat of the whole component is transferred through the surface layers, where a low crystallisation degree is expected, the prevailing reduced thermal conductivity effects the injection moulding process significantly. To measure the crystallisation degree dependent thermal conductivity, a method using a Flash- DSC is presented and tested with isotactic polypropylene. To reduce effects of the Flash-DSC measurement itself a large parameter sweep is used to calibrate the measurement instrument. Using the Flash-DSC, however, delivered an inverse relation of thermal coefficient and crystallisation degree which contrasts with literature, which expects a direct proportional relation.
Mass Spectrometry (MS) has become an indispensable tool for polymer analysis and has been widely used to study polymer structure and composition, end-groups and additives, molecular weight distribution, degree of polymerization, and so on. MS analysis is extremely sensitive, allowing the detection and identification of minor polymer components and synthesis by-products, as well as low-level impurities and products of decomposition. Matrix Assisted Laser Desorption Ionization (MALDI) MS is a well-established method of polymer characterization that continues to be developed and improved with new generations of MS instruments, bringing new analytical capabilities and enhanced performance. Modern MALDI-MS instruments generate rich chemical information highly specific for polymer structural analysis, copolymer composition and complex polymer mixtures characterization, and can even be used for imaging of synthetic polymer surfaces. Because of its unique capabilities, this technology has been widely used in a great variety of polymer analysis applications in both academic and industrial settings. In some cases, MALDI-MS is the only technique that can provide the information required to solve a practical problem. It allows for rapid MS analysis where no prior sample treatment or extensive separation is needed, including characterization of challenging insoluble polymers. TIMS technology has redefined the capabilities of Ion Mobility separation by providing an unmatched combination of resolution, speed, robustness and sensitivity. In polymer analysis applications, the timsTOF instruments expand the analytical boundaries by combining the TIMS technology with ultra-high-performance MS and providing an additional dimension for separation of complex polymer mixtures and structural analysis of challenging polymer compositions. Compatible with HPLS-ESI, GC-APCI and MALDI workflows, Bruker timsTOF fleX is a go-to multitool for a modern polymer lab.
There are unique opportunities to develop coatings for non-urea fertilizers and provide desired performance such as enhanced controlled nutrient release and dust resistance. The key contributions from this work; provided advanced analytical solutions to evaluate fertilizer coating quality and developed quantitative QC tools for nutrient release and dust resistance. In conclusion, developed hydrophobic polyurethane fertilizer coating solutions that provides significant shelf stability and controlled nutrient release.
The strength that glass reinforcement can impart to plastic materials is phenomenal. Glass fiber reinforced plastics offer enhanced mechanical properties, particularly strength and stiffness over unfilled materials. Their use is widespread in a wide variety of applications where mechanical integrity is essential. However, this benefit is not without its challenges. This presentation will focus on the investigation of failures of components manufactured from glass fiber reinforced plastics. The goal of a failure analysis is to identify the mechanism and cause of the component failure - to distinguish how and why the part broke. This presentation will explore the challenges unique to glass fiber reinforced materials and techniques that can be used to gain the maximum information from these failures.
We developed a rheo-Raman spectroscopic system by combining a Raman spectroscope and rheometer to investigate the flow-induced crystallization behavior of polyethylene. Conformational changes that occurred during the flow-induced crystallization such as the formation of consecutive trans sequences or crystalline structure can be detected using Raman spectroscopy. We confirmed that no crystallization takes place at 130 ºC without shear flow because the fraction of the consecutive trans sequences and the crystalline structure was almost zero for 60 min. In the case of the flow-induced crystallization at 130 ºC with a shear flow of 100 s-1 for 30 s, the fraction of the long-consecutive trans sequences composed of more than 10 trans conformers increased with increasing time while the crystallinity was almost zero after applying the shear flow to the sample. Moreover, the long-consecutive trans sequences were formed as the precursor of the crystalline structure only at the shear rate with the Weisenberg number, which is the product of the shear rate and the Rouse relaxation time, greater than unity. These results suggest that the long-consecutive trans sequences are formed as precursors of the crystalline structure due to the stretching of the molecular chains under shear flow.
Processing of thermoplastics during injection molding and blow molding usually includes rapid cooling with rates up to 103 K/s and solidification at high supercooling. Fast scanning calorimetry (FSC), an advanced calorimetry, is able to cover high processing rates and wide temperature windows by just using a few nanograms of the sample. With the advent of FSC, the crystallization fingerprint of many thermoplastics has been revealed. In this work, we expand the existing capability of FSC by coupling it with other techniques, including micro-IR spectroscopy (Micro-IR), atomic force microscopy (AFM), polarized optical microscopy (POM), and X-ray computed tomography (XCT). Polymorphism and morphology transition associated with processing conditions will be discussed in polyamide 66, polyamide 6, poly (ether ether) ketone and its composites. A more accurate simulation of plastic solidification can be achieved using fast scanning calorimetry and related technology.
A variety of questions may arise in the UV-curing process of polymeric materials. For example, when does UV-curing start? When is UV-curing complete? What is the reactivity of the resin? What is the glass transition temperature after curing? Which photo initiator does show best performance? How does mechanical property of the cured material change in UV-curing process? Differential Scanning Calorimetry (DSC), Dielectric Analysis (DEA) and Dynamic Mechanical Analysis (DMA) offer effective means to help to answer these questions. DSC measures reaction enthalpy and degree of cure initiated by radiation. DEA allows for the measurement of changes in the dielectric properties related with ion mobility and dipole alignment during cure. Compared with DSC, DEA is good for fast cure system because data acquisition rate is less than 5ms and more sensitive to small change in cure process when close to the end of cure. DMA measures modulus changes during UV-curing process. These thermal analysis methods are indispensable in both R&D and quality control in the area of UV cure.
The paper describes the development of a variothermal process, which increases the mold surface temperature during the injection molding process without significantly extending the cycle time and minimizes unintentionally heated mold areas. To this end, the possibility of achieving the desired effects by direct introduction of heated gases into the mold cavity is being investigated. By addressing central issues such as gas distribution geometry, injection possibilities, required gas temperatures or the possibility of process implementation in a demonstrator mold, it was possible to develop a process with which it is possible to achieve temperature optimization for visually appealing parts within seconds. This means that weld lines, streaks or uneven mold impressions can be concealed even on flat parts.
Due to the recent and ongoing pandemic – COVID-19 – there was an urgency to determine a method to delay the continuously rapid development of the new virus. As a result, Ultraviolet-C (UVC) light, also known as Ultraviolet Germicidal Irradiation (UVGI), has been in higher demand because of its known ability to disinfect quickly and effectively. However, because of its short wavelength/higher energy, either 222nm or 254nm, material degradation is usually much more accelerated than Ultraviolet-A (UVA) or Ultraviolet-B (UVB). At this moment, this study only observed color change when exposing polystyrene to UVC light, and it is believed that this is one of the first studies, if not the first, conducted with this material. Polystyrene was selected because of its availability, abundance of relevant research (ie. UVA/UVB exposure results), and its use in weathering standards. Additionally, since there are no standards specifically about UVC exposure, this preliminary research may provide some direction.
The overall goal of the project targets the development of a product containing a rheology modifier additive in polyethylene (PE). This product is being sold to film converters for addition to the extruders of blown-film lines together with LLDPE resins. This increases the melt-strength during processing and the shrink tension for collation shrink films, enabling reduction in LDPE content and resultant tougher films. A tougher film will allow down-gauging and hence reduce material consumption, increasing the sustainability component for customers. This study focuses on the development of an analytical method at Dow to measure the concentration of the rheology modifier additive in PE. The method was validated and implemented successfully.
Foamed parts are being produced in ever greater quantities. This is done, on the one hand, to save weight and, on the other hand, to take advantage of the greater design freedom in the layout of foamed components. Until now, quality control of the foam structure has hardly been possible without destructive testing methods. Therefore, a test method is presented to qualitatively evaluate the foam structure of foamed components without destruction.
This paper describes the use of differential scanning calorimetry (DSC), modulated DSC, and dynamic mechanical analysis to characterize different regions of thermoformed beverage cups made from polylactic acid. These techniques demonstrated the differences in crystallinity and mechanical strength of the cup based on the location of the specimen. These techniques can guide the processor in resin selection and processing conditions.
Understanding heat shrink film properties and behavior will help optimize shrink wrap formation in packaging applications. Two experiments were conducted to better understand shrink properties of PE film. The first experiment was to collect data on film shrink ratios. The second experiment was an attempt to compare film preshrunk and post-shrunk mechanical properties. For this, a fixture was developed to quantify film shrink under isothermal heating. The film submersion tool successfully yielded films that were shrunk at different temperatures and demonstrated a method applicable for analyzing properties of heat shrink film at various stages of the shrinking process. Further work is focused at developing correlations between preshrunk properties to post-shrunk properties.
The development of Poly(vinylideneflouride) (PVDF) material with high electroactive properties is of great interest for its use in energy harvesting. This study is concerned with producing PVDF filaments to be fed into a Fused Filament Fabrication (FFF) 3D printer to broaden the horizon for printing complex energy harvesters. An extrusion process followed by post treatments was applied and the processing conditions were varied as they play a crucial role in altering the phases within PVDF and its crystallinity. The correlation between the parameters and the resultant properties of the PVDF filament was made using combination of Fourier-transform infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) characterization techniques. The optimized processing conditions were found to be 230 ᴼC for extrusion temperature and 4.5 – 6.5 stretching ratio. This led to the fabrication of an electroactive PVDF filament with 80% β-phase content and 50 to 55% degree of crystallinity.
Ethylene-methacrylic acid (EMAA) copolymers are converted to ionomers (ionic functionality) through the partial neutralization of their carboxylic acid groups. These ionic groups are randomly distributed along the polymer backbone, and various cations (i.e., Na, Zn, Mg, Li, etc.) can be incorporated into the ionic functionality to modify their properties. Some unique properties that these ionomers exhibit include high melt strength, excellent toughness and optical clarity. These desired properties make the ionomers ideal for applications that include packaging, decorative perfume and spirit caps and capstock decking. This study was focused on the use of Fourier-Transform Infrared (FTIR) spectroscopy to study EMAA copolymers partially neutralized with Zn cations. FTIR was also used to measure the degree of neutralization of ionomers. The % neutralization method was developed internally, and it was applied to extract the experimental neutralization values with comparison to theoretical values for EMAA–Zn ionomers. The values were in good agreement with the expected neutralization levels. Chemical mapping of the acid band (C=O stretch) and carboxylate band (COO- stretch) in EMAA–Zn ionomer indicated that their distribution on a micro-scale in the selected cross-section were homogeneous. The FTIR method was also used to study EMAA copolymers neutralized by mixed metal Zn and Na cations and compare with EMAA ionomers neutralized by single metal cation. For the mixtures, a new carboxylate band appeared around 1569 cm-1, which was assigned to the COO- stretch. Based on the unique peak position, it suggests that there are interactions between the zinc and sodium cations.
Predicting useful remaining life of cables in nuclear power plants is a topic of growing interest as plants continue to age. A typical electrical cable consists of polymeric materials, such as the cable jacket and insulation, which are susceptible to degradation due to exposure to both elevated temperatures and gamma irradiation over decades of service. In this work two insulation materials, crosslinked polyethylene (XLPE) and ethylene propylene diene (EPDM) elastomer, were characterized to quantify aging using total color difference and indenter modulus. Since the effects of thermal and gamma radiation are not additive but coupled, the effects of different aging scenarios including sequential and simultaneous aging were also evaluated. In the case of sequential aging, two aging scenarios were explored where the order in which thermal and gamma radiation received were altered. Total color difference of XLPE showed that sequentially aged insulation specimens, which received radiation first, degraded slightly more at maximum exposure than specimens which received thermal first. Similarly, in the case of EPDM, the extent of degradation evaluated using total color difference was found to be most severe in the case of sequentially aged insulation specimens which received radiation first. Indenter modulus was found to be insensitive to aging for XLPE but trended for EPDM. The largest variations were observed for the sequentially aged insulation specimens which received radiation first, similar to what was observed for total color difference.
An instrumented hot end has been developed to monitor the pressure in Fused Filament Fabrication, and is used as an in-line rheometer to characterize the viscosity of an acrylonitrile butadiene styrene (ABS) material. Additional analysis was performed on the transient pressure data to consider compressibility effects and nozzle drool. The range of flow rates was identified at which the pressure in the hot end was most stable. Stabilization time given compressibility effects was also evaluated.
With advances in computing technology, applications of computer-aided engineering (CAE) technology are becoming widespread in diverse industries. Specifically, machine learning is now being applied to fields such as that of materials design and production which is the field within which this study focuses. However, problems in implementing this technology arise in regard to lengthy analysis times and a lack of suitability in regard to on-site, real-time judgments during some production processes. This study addresses these issues in regard to the problems of applying CAE to the injection molding production process where quite complex factors inhibit its effective utilization. In this study, an artificial neural network, namely a Back Propagation Neural Network (BPNN), is utilized to render results predictions for the injection molding process. By inputting the plastic temperature, mold temperature, injection speed, holding pressure, and holding time in the molding parameters, these five results are more accurately predicted: EOF pressure and maximum cooling time, warpage along Z-axis, shrinkage along X-axis and shrinkage along Y-axis. This study first uses CAE analysis data as training data and reduces the error value to less than 5% through the Taguchi Method and the Random Shuffle Method which we introduce herein, and then successfully transfers the network which CAE data analysis has predicted to the actual machine for verification with the use of transfer learning. Of particular interest, is this study's use of a Back Propagation Neural Network (BPNN) to train a dedicated prediction network through using different, large amounts of data for training the network, which is proven fast and that can predict results accurately using our optimized model.
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.
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.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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