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.
Rheological testing of new material formulations can require significant quantities, specifically when considering development of new chemistries at the laboratory scale. In order to minimize the quantity of material required for evaluation, we are developing approaches suitable for characterization of high solids content formulations using micro-capillary rheometry. The goal of this investigation is to design and produce a micro-capillary rheometer capable of characterizing basic rheological properties, such as viscosity and shear-thinning behavior, while requiring the least amount of sample possible. In our current design, we implement a micro-dispensing approach combined with calibrated force transducers. With this approach we can further elucidate an understanding of the differences between typical capillary rheometry and behavior at reduced dimension flow fields. Issues such as pressure relaxation and free volume compaction can therefore be studied through readily modified geometries and testing rates. This design will lead to a better understanding of micro-capillary rheometer design and enable a unique approach for rheology measurements for new chemistries and formulations, including high solids content formulations (up to 60+ vol%). Additionally, this framework will facilitate the study of a variety of flow geometries applicable to a wide range of applications including precision dispensing of adhesives and sealants, and direct ink write additive manufacturing.
This conference paper presents the investigations, results and findings from the research project "Tool-integrated assistance system for production control of highly complex and demanding component specifications" (acronym in German WASABI). The project investigates the possible use of sensor technology in combination with machine learning methods for the prediction of quality-determining component features on large-format plastic products. Furthermore, the information obtained will be used to propose target-oriented recommendations for action based on the predicted feature characteristics. An outer skin component (bumper) from the automotive sector was defined as the reference product for the investigations into the prediction possibilities of demanding component specifications. The injection molding tool required for production was designed as part of the project work and equipped with a variety of different sensor types (including pressure, melt contact, displacement measurement). The recording of the measurement signals is realized by a self-developed hardware system concept. The aim of the research is to predict various quality-determining characteristics from the fields of geometry (including total length) and surface (including sink marks). In the course of the project, extensive tests were carried out to generate a meaningful database. Through analysis and evaluation, it was possible to define the positions and number of sensors that provide a high level of information. Ultimately, three different approaches of machine learning methods could be learned for the prediction of component qualities and the prediction of corrective actions. These structures could be verified in laboratory environment by appropriate test data sets.
A method was developed for fabricating recycled composites from post-consumer polyethylene terephthalate (PET) carpets and recycled PET resins. Compression molding of the components under different pressures, temperatures, and compositions was performed. Preliminary molding conditions were arrived at based on analyzing the differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and melt viscosity data for different raw material combinations. Molding factors were screened to define applicable ranges for each parameter. The effects of configuration and composition of components, temperature, molding time, and pressure were considered in the screening process. Mechanical properties of composites were determined by 3-point flexural (according to ASTM D790) and creep tests. The molded materials showed acceptable mechanical strength and modulus values required for structural applications.
The shear rate-dependent viscosity of natural rubber and three types of synthetic rubber was measured using the Rubber Screw Rheometer. Viscosity values with Mooney viscometer, which has traditionally measured rubber viscosity, have a high correlation with the values of RSR shear rate 10 [1/s]. Thus the Mooney Viscosity value can be estimated using the RSR shear viscosity measurement. Also, in the case of virgin rubber, the accuracy of the measured value increases when it has a pre-shear history. It was confirmed that the viscosity measurement value was a measurement value having a deviation within +3% when comparing the three times repeated measurements. The measured value was correlated to Mooney Viscosity successfully with a first- order equation.
There has been a common goal among various researchers across the globe to investigate sustainable and high-strength materials as a suitable replacement for metallic materials in many industrial sectors. Many products obtained through reinforcing steel can potentially be replaced with those synthetic fibers such as carbon and glass to overcome the critical issues pertaining to dimension stability along with the creep effect that could pose complications in applications such as belts driving heavy machinery. In the current study, Steel, Carbon and glass fibers were reinforced in TPU matrix and manufactured by compression molding. The resulting composite materials were then tested for tensile analysis. After comparing the mechanical properties of the fibers, it was observed that the carbon/TPU showed the highest load-bearing capacity, followed by steel and glass reinforced TPU composites. The results also opened up the possibilities for carbon fibers to be a suitable replacement candidate to the steel cords that are used in applications such as conveyor belts for providing the required tensile strength.
In this study, PET was combined with a latent metal oxide reagent, CaO, which allowed the PET to hydrolyze when submerged in water, breaking down the polymer chain and forming calcium terephthalate as a nontoxic byproduct. PET/CaO composites were mixed at 10, 20, and 30 wt% CaO, and 0.001” thick films were prepared by compression molding. These films were degraded in water at 90°C for varying amounts of time. Puncture testing, optical microscopy, FTIR, and TGA were performed to probe the degradation of the material and verify that it was producing the products that were expected from the reaction. The PET/CaO composites were shown to be degradable in water, with a significant loss in mechanical properties after only an hour. The rate of degradation was strongly dependent on the concentration of CaO, with significantly faster degradation at higher concentrations.
In flexible packaging, film thickness transitions can be problematic regions to seal due to their propensity for leaking, as well as the high seal pressure required to create a continuous seal over the transition. A compliant anvil can be used to decrease the required seal pressure, as the hot tool will be able to contact both the thick and thin regions of the packaging, with compression of the compliant anvil. However, a compliant anvil cannot be used in a double-sided heating process. Therefore, in a double-sided heating process, high seal pressures must be utilized in order to reduce the film thickness in the thick region, to facilitate tool to film contact in the thin region. In this study, the required seal pressure needed to create continuous (non-leaking) seals over a 4-film to 8-film thickness transition was explored, with both a rigid and conformable anvil. With a rigid anvil 3.25 MPa was required to consistently create continuous seals. With a conformable anvil 0.87 MPa was required to consistently create continuous seals.
Cyclic olefin copolymers (COC) provide manufacturers and converters with an opportunity to create thin, stiff, high performance polyolefin packaging products. COC provides an unexpected, but essential benefit that enables the manufacture of high-density polyethylene (HDPE) containers by reheat injection stretch blow molding. COC has good dimensional stability and excellent heat resistance, minimizes distortion of PE exposed to thermal and mechanical stresses.
For several decades, the Tait model has been used in simulation software to describe the volumetric mechanical behavior of thermoplastic polymers as they cool. It is used to compute the residual strains and stresses of the polymer as it solidifies, but there is a problem. Many data sets have coefficients where there exists a discontinuity at the transition between the molten and solid domains. This paper outlines some basic checks that can be done to detect this problem and a procedure to fit the coefficients to data so that this problem does not arise.
Vibration welding flash occurs when molten polymer flows under pressure from the weld interface. This study examines the formation of small hair-like fibrils during vibration welding. Polypropylene and nylon 6 plates were butt-welded and the assemblies were assessed using a high-speed camera and digital microscopy. A mechanism has been proposed whereby initial asperities at the weld interface first melt to form a polymer pool. Thermal expansion of this pool allows polymer to be extruded laterally towards the edge of the weld interface. The extrudate is rolled up to form fibrils that can eventually grow to several millimeters in length.
Electromagnetic interference (EMI) is a common problem encountered by electronic devices, especially in electric vehicles. External electromagnetic (EM) waves affect the operation of an electronic device by interfering with the internal EM signals. To provide EMI shielding, various materials were studied, and the measured electromagnetic shielding effectiveness (SE) data are presented in this study. The main factors affecting EMI SE are quantified statistically – filler loading, shield thickness, and base polymer resin matrix. Long steel fiber thermoplastics provide the highest EMI SE, at over 60 dB at frequencies ranging from 30 MHz to 20 GHz, and at thickness as low as 1.6 mm. It is also demonstrated that carbon fiber filled thermoplastics can provide EMI shielding at levels greater than 50 dB.
Ultrasonic welding (USW) is a surface mating process where absorbed moisture in the surfaces of hydrophilic materials can negatively affect the weld joint quality and strength. USW is a secondary processing operation that is performed post-molding or extruding. Hence, during the storage time between primary processing and USW, the parts are susceptible to moisture absorption. Therefore, it is necessary to characterize the moisture sensitivity to meet the specified weld strength. Moisture sensitivity of Industrial standard test parts (ISTeP) made with PLA, PBS, and PLA/PBS 25/75 blend was characterized for USW in this study. ISTeP parts were moisture conditioned for one week at different relative humidity (RH) levels and then tested for weld strength. It was found that the weld strength decreased with increase in RH for 100% PLA ISTePs but it was not statistically significant. Above 65% RH, weld strength of 100% PBS was significantly decreased. Scanning electron microscopy of weld areas after the pull test revealed an increased amount of trapped porosity in the fractured surfaces of high relative humidity samples. It was also demonstrated that PBS and PLA/PBS composite can be ultrasonic welded.
This work demonstrates the efficacy of amorphous polyhydroxyalkanoate (a-PHA) copolymers in enhancing the impact strength of PLA without compromising the compostability and bio-based carbon content of the final product. The influence of PHA polymer composition on the performance of PLA will be highlighted for applications including thermoforming, film and injection molding. Finally, the morphology of the blend will be used to explain the impact modification mechanism. Blends of 100% bio-based and fully biodegradable a-PHA and PLA exhibit good toughness and clarity in injection molding, extruded sheet and blown film. It will be shown that the level of toughness increase and modulus reduction can be tuned by blend composition.
Ethylene-octane copolymer (EOC) with high octane content (45 wt.%) was cross-linked via electron beam irradiation at different dosages (30, 60, 90, and 120 kGy). Effect of irradiation dosage on thermal and mechanical properties was studied. When compared to low density polyethylene, EOC exhibited higher degree of cross-linking reflected in increased gel content, higher elastic modulus (G’), and lower tan obtained by rheology measurement at 150 °C. Cross-linking caused improvement in high temperature creep and also in elastic properties at room and elevated temperatures. Differential scanning calorimetry revealed that e-beam irradiation has caused a gradual reduction in crystallinity and a presence of a fraction with higher melting temperature. In the case of EOC, as the extent of cross-linking increased, stress at break showed an increasing trend whereas irradiation dosage had an inverse effect on elongation at break which could be aroused from the formation of crosslink networks. Radiation dosage has positive effect on thermal stability estimated by thermogravimetric analysis. After 30 min of thermal degradation at 220 °C, slightly higher C=O peak for cross-linked sample was found by Fourier transform infrared spectroscopy while for room temperature samples no C=O peak was detected.
In this paper, the tensile properties of indoor and outdoor post-consumer recycled (PCR) polycarbonates (PC) have been compared with virgin PC at various aging conditions. 50% recycled PCs showed comparable tensile strength at breakage (~70 MPa) and maximum strain (~190 - 200%) before aging, when compared to virgin PC of same MFR of ~10 g/10 min. Three different high temperature and high humidity aging conditions were investigated: 40oC 90% RH, 60oC 90% RH, and 85oC 85% RH for up to 500 hours. Strength at breakage was found to decrease as the aging stress or aging time (with the same aging condition) was increased. Both the indoor resins were comparable in strength up to 60oC 90% RH. But in 85oC 85% RH both showed significant drop in strength. On the other hand, outdoor PCR resin showed much better performance (only ~12% degradation) in 85oC 85% RH compared to other two indoor resins (25 - 40% degradation). Outdoor UV aging characteristics were also compared between 0%, 50% and 75% PCR and degradation up to 600 hours were found to be within 5%.
Recycling of plastic waste at Forward Operating Bases. (FOBs) is continuing to be a topic of considerable interest to the Department of Defense. A previous paper  by the current authors described the need and opportunity to convert this waste stream to plastic lumber that could be used by the warfighter for various construction applications at forward operating bases (FOBs). The selected technique of flow intrusion molding of recycled PET (rPET) into 1 inch by 1 inch by 36 inch test specimens showed feasibility of this recycling technique and the resulting specimens were very stiff with high modulus but they failed during testing in a brittle fashion with fragmentation. This is not a desirable failure mode and work was conducted to improve the ductility of the plastic lumber specimens using both chain extenders and impact modifiers. This paper describes the investigation of using additives to improve ductility and therefore the utility of rPET to make plastic lumber using flow intrusion molding and the resulting performance characteristics.
This paper describes the development of innovative temperature control concepts for use in additively manufactured inserts based on CO2. These have been successfully investigated for their suitability in small batch production. The additive manufacturing processes have been evaluated in terms of their suitability for the production of mold inserts. It has been possible to reduce the time required to prepare the inserts. In the investigation of suitable plastics, POM has proven to be suitable. Of the generative manufacturing processes investigated, stereolithography was found to be suitable. Robust manufacturing in the injection molding process with the other additive manufacturing processes was not possible. The manufactured components were examined with regard to their properties and compared with conventionally injection-molded components. It was found that a clear dependence on the manufacturing process of the insert used for production can be observed, especially in the crystalline microstructure of the manufactured components. This makes it difficult to use additively manufactured tool inserts in small-batch production, since the resulting properties of the components in terms of crystallinity and thus distortion are not comparable with injection-molded components. In further investigations, the minimum necessary thermal properties of the printing materials must be determined in order to ensure robust small series production with component crystallinity comparable to the injection molding process.
Aqueous polyurethane dispersions based on castor oil and lignin sulphonate (LS) were successfully synthesized in homogenous solution with no organic volatile compounds and excellent dispersion stability. Transparent thin films of PU-LS with different LS contents were obtained via solution (dispersion) cast technique. The glass transition temperatures (Tgs) of the PU-LS films were evaluated from the dynamic mechanical analysis (DMA) at 1 Hz and 2 oC/min heating rate. The Tg was found to be strongly influenced by the incorporation of the small LS content. The Tg (temperature of tand peak maximum) for PU-LS film with LS content lower than or equal 3 wt.% increases considerable with increasing the concentration of LS. For higher concentrations, no significant additional increase in the Tg was observed. The crosslink density was also calculated from the elastic modulus at a temperature of 40 oC higher than the Tg based on the rubber elasticity theory. The crosslink density increases with increasing the LS content of the thin films. The thermal-induced shape-memory effect was investigated using DMA according to cyclic thermomechanical tensile tests. The PU-LS thin film was found to have an excellent shape-memory effect and the recovery was strongly dependent on the LS content. Fast recovery (17 sec) to the permeant shape was observed once the temporary shape sample was immersed in water bath at the programming temperature.
A seamless modeling framework from injection molding simulation to anisotropic structural analysis is presented. Key features of the framework are anisotropic material modeling and fiber orientation data mapping, aspects that are facilitated by coupling Moldex3D, Digimat, and ANSYS software. The approach is exercised by modeling the mechanical response of injection molded tensile specimens with single and dual gates made of a thermoplastic resin with 20% glass fiber weight fraction. It is reassured that local fiber orientation is crucial for an accurate prediction of the mechanical strength of dual-gated tensile specimens with a weld line. Unlike the isotropic modeling approach, typical features of stress and strain concentrations along the weld line are clearly demonstrated. The capability of the approach is further highlighted by accurately predicting the break-off torque of a screw head used to adjust the seal compression in cable entry ports of optical closures.
The effects of the processing parameters on the curing of continuous carbon fiber composite made from Hexcel AS4/8552 prepreg tape are studied. A commercial process simulation finite element method, that takes in account the residual stresses due to chemical, thermal, and mechanical shrinkages, is utilized. This method solves the curing process sequentially. In the first step, the distribution of temperature and degree of cure in the composite is computed. In the second step, the information from the previous step is used to calculate the stress evolution during cure. At the end of the second step, the composite deformation due to tool removal is also calculated. The impact of three different process parameters on the final degree of cure and the residual stresses are studied in detail.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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