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.
The SPE Library is just one of the great benefits of being an SPE member! Are you taking advantage of all of your SPE Benefits?
Attributed to the confinement effect and unique properties, multilayer nanostructures have attracted extensive attention. Coarse-grained molecular dynamics simulations were carried out to understand the interfacial microstructure and mechanical properties of multilayer low molecular weight polypropylene (PP) films by comparison with those of the corresponding bulk material. The molecular order parameter, radius of gyration and end-to-end distance of the chains were calculated. Out of surprise, in the multilayer PP films, the confinement effects make the polymer chains at the interfaces keep being highly ordered, extended and perpendicular to the normal of the interfaces, and those in the layer keep unordered and shrunk, with little interlayer interpenetration. However, for their bulk material, all polymer chains are in the state of being highly extended, ordered, and crystallized. These results are distinct from those of general flexible linear polymers. We found that the dependence of the tensile strength of the multilayer PP film on the degree of interfacial integration between the layers is weak. The distinction of the microstructure between the multilayer films and its bulk material is a critical factor that influences the fracture behavior of material. These findings would give rise to better understandings about the mechanical properties and crystalline behaviors of the multilayer polymer films.
Short glass fibers are widely employed in reinforcement of nylon compounds to significantly improve mechanical properties. These properties are dictated by fiber length and orientation distributions in the compounds. Fiber breakage takes place during the compounding process. When the fibers break into sub-critical length, the reinforcement of the compound is limited. This paper used a full factorial design investigating the effects of nylon’s viscosity and twin screw extruder’s screw configuration on glass fiber length retention and mechanical properties of the final compounds.
The main aim of this work was to investigate the enhancement of flame retardancy of unsaturated polyester resin (UPR) based on DOPO derivatives-DHP and aluminum hypophosphite (AHP). The UPR/DHP/AHP composites were characterized by UL-94 vertical combustion tests, limiting oxygen index (LOI), microscale combustion calorimetry (MCC), and thermogravimetric analysis/infrared spectrometry (TG-IR) tests. These results reveal that the flame retardancy of UPR/DHP/AHP composites is significantly enhanced, such as passed UL-94 V-0 classification, decreased peak heat release rate (PHRR) maximally by 40.3% and total heat release (THR) maximally by 18.5%. TG-IR results demonstrate that the incorporation of DHP and AHP in the composites could reduce flammable gas amounts and capture free radicals in gas phase. SEM images show that a dense and compact char layer is formed during the combustion.
A process for obtaining improved mechanical properties for immiscible polymer blends was proposed and proved valid for the system of polypropylene (PP) and polystyrene (PS). By minimizing the jet stretch applied to the fiber precursor and implementing a standalone hot drawing stage, the Young’s modulus and tensile strength of the processed fiber were shown to be greatly improved. The mechanisms responsible for improved modulus and tensile strength, achieved via low jet stretch and subsequent hot drawing, are quantitatively explored and explained. A model with logarithmic strain relaxation is provided to explain the radical distribution of the area of PS phases. Empirical models for predicting Young’s modulus were also used and compared with experimental data to identify the best fitting model.
Jens P. Siepmann, Johannes Wortberg, Felix A. Heinzler, May 2017
For the production of injection molded parts with a subsequent electroplated coating, technical polymers like acrylonitrile butadiene styrene or polycarbonate/ acrylonitrile butadiene styrene blends are used. The quality of these parts is affected by both the electroplating parameters and the properties of the surface and subsurface structures of the injection molded part. Processing parameters influence these structures during injection molding and hence are responsible for the adhesion of the polymer and the metal ,. The effects on the resulting caverns in polymer surfaces (after etching) caused by changing injection molding parameters are investigated. For this purpose, relevant processing parameters affecting the surface structure are examined. Furthermore, image analysis is applied as an objective evaluation method to quantify the two-dimensional shape of caverns. This analysis is based on electron microscope (SEM) images of chemical etched polymer part surfaces (ABS, PC/ABS). Meaningful key figures, such as roundness, degree of orientation, caverns/µm², and area of caverns, are emerged to quantify the surface structure. An ABS and PC/ABS material is tested and compared, and coherences between the shape of the caverns, processing parameters, material properties, and geometry influences are elaborated.
This work describes a novel, high-speed twin-screw extrusion process applied to blends of bioplastics. The blends were chosen for their ability to combine synergistic polymers to produce more robust bioplastics with diverse properties. The influence of interfacial reaction was also studied, both from the perspective of morphology development and final properties improvements. Immiscible PLA/PA11 blends were successfully compatibilized by in-situ reactive twin-screw extrusion. During processing, the molecular weight of PLA sharply decreased due to chain scission. Mechanical property improvement was realized through processing parameter optimization and addition of a chain extender.
Iman Soltani, Bradley Losey, James D. Martin, Richard J. Spontak, May 2017
This research studied the morphologies of layer-bylayer (LBL) assemblies, comprising clay and alternative polyelectrolyte layers of polyethyleneimine (PEI) and sulfonated polyethyleneterephthalate (PETi). The samples prepared with such coatings on polystyrene, showed very low permeability values against gases, like oxygen, that can be considered as the lowest recorded value for this polymer. Transmission electron microscopy and x-ray diffractometry pointed to the increased level of intercalation and orientation of LBL assemblies, below a certain range of montmorillonite (MMT) concentration in deionized water, above which LBL assemblies’ gas barrier improvement leveled out. These results may be connected to the possible decreased level of MMT dispersion in its suspension and its increased viscosity. Comparing the LBL assemblies formed from two alternative polyelectrolytes used, the ones comprising PEI showed better orientation and regularity levels. It may conjecture that PEI makes more significant interactions than PETi, with clay platelets surfaces.
Grooved-bore, single-screw extruders are commonly used in Europe, and they are used to a lesser extent in North America. In North America, they are often used as the extruders for blown film, blow molding, and pipe processes where the discharge temperatures need to be relatively low and the rates high. Screw designers for grooved-bore machines are very good at providing screws that discharge at low temperatures and high rates, but they typically are not focused on providing a gel-free extrudate. This paper will discuss methods to mitigate gels for grooved-bore machines running polyethylene (PE) resins.
Martin Spörk, Chethan Savandaiah, Florian Arbeiter, Stephan Schuschnigg, Clemens Holzer, Montanuniversitaet Leoben, May 2017
Fused filament fabrication (FFF) has the potential to enter industrial application due to the possibility of producing complex designs in limited series. However, currently only a limited number of materials is commercially available for use in this process. This study aims at expanding the material range for FFF towards polypropylene (PP) by modifying it with 30 vol.-% of glass spheres and a compatiblizer. Furthermore, the difference between hollow borosilicate and solid inorganic soda lime glass spheres of the same mean filler diameter was examined. In this paper the shrinkage upon solidification, the thermal behavior of the compounds, the mechanical properties of the filaments, and the viscosity of the molten materials were analyzed, as these properties are decisive parameters for a successful printing process. Additionally, the adhesion between the filament and various printing surfaces is addressed and all results are compared to PLA, a well-established FFF filament material. It was observed that the addition of spherical glass fillers leads to a reduction in shrinkage and an increase in the crystallization temperature, while the degree of crystallinity remains unaltered. The efficiency of the compatibilizer depends distinctly on the used glass type. Well-compatibilized compounds reveal yield stresses similar to unfilled PP and lead to a decrease in the overall viscosity. The PP-based compounds investigated do not adhere to the standard printing bed (mirror). However, they exhibit a tendency to stick to surfaces with similar polarity, such as PP-films.
Sven Staperfeld, Thorsten Krumpholz, Jan-Gerd Pennekamp, May 2017
In the Particle-foam Composite Injection Molding (PCIM) process a compact material is injection molded onto foam. PCIM parts combine the positive properties of both material types, compact materials and particle foam in one part. This means it is possible to manufacture parts with thermal insulation properties, force absorbing properties, a high degree of stiffness and attached elements like snap-fits and screw fittings for example. The University of Applied Sciences Osnabrueck examines the adhesion properties between these components. This results in a mechanical characterization of PCIM parts, which will allow dimensioning of these composites in the development phase of PCIM products. The project is supported by the Federal Ministry of Education and Research (BMBF) and the companies Arburg, Krallmann and Ruch Novaplast are project partners.
Klaus Straka, Bernhard Praher, Michael Hettrich-Keller, Georg Steinbichler, May 2017
Previous attempts to accurately measure the real polymer melt temperature in the screw chamber have failed due to the challenging metrological boundary conditions (high pressure, high temperature, rotational and axial screw movement) in the plasticizing unit. We developed a novel ultrasound system - based on reflection measurements - for the online determination of these important process parameter. The system is compared to an infra-red- (IR-) camera system, which measures the melt temperature during an air shot in front of the nozzle. The recorded data of the measurement systems are used to study the influence of process parameter variations on the melt temperature profile in the screw chamber of a reciprocating single screw plasticizing unit.
The poly (lactic acid) (PLA) crystallization behavior was investigated during an extrusion process via visualization techniques. Effects of various processing parameters, such as extruder barrel temperature profiles, the system pressure, the flow rate, and the blowing agent content, on formation of PLA crystallites in the melt flow were discussed. Various observations and results are reported. First, the PLA crystallites were visualized by decreasing the barrel temperature at a low flow rate. Then, it was visualized and quantified that a sudden increase in the flow rate, under the identical cooling protocol, enhanced the PLA crystallization dramatically. Moreover, by introduction of CO2 into the system, the PLA crystallites formed at a lower temperature profile. Finally, it was revealed that the induced crystallites improved the foaming behavior of extruded foams through minimizing the cell coalescence.
Filling ratio is an important process parameter related to the residence time distribution and thermal history of resin in a twin-screw extruder. This study presents a theoretical method of filling ratio distribution calculated by our newly developed 2.5 D Hele–Shaw flow model and finite element method. The calculated filling ratio distribution of a full-flight screw was validated by on-line measurement of resin volume with the laser light section method. The calculation and measurement results were in good agreement.
Ballistic clay is used as a backing material for standards-based ballistic resistance tests for the purposes of providing a measure of the energy transferred to the body when a threat is defeated. However, this material exhibits complex thermomechanical behavior under actual usage conditions. In this work, we characterize rheological properties of the standard backing clay material, Roma Plastilina No. 1, used for body armor testing, using a rubber process analyzer. Test methods employed include oscillatory strain sweep, frequency sweep, and oscillatory strain ramp. The results show that the material is highly nonlinear, thermorheologically complex, and thixotropic. The modulus decreases under dynamic deformation and partially recovers when the deformation is discontinued. Experimental protocols developed in this study can be applied for the characterization of other synthetic clay systems.
Most plastics products are made from a base polymer mixed with complex blends of materials known collectively as additives, to ensure that the physical, mechanical and surface properties of the final product is optimised in all aspects. This will include safer, cleaner product possessing optimal colour and properties. Fine additives such as fillers or coloured pigments are most widely used and the improved technique for dispersing particles into polymer is highly demanding in industrial practice. A USV (ultra-sonication and vibration) assisted process during twin screw extrusion system was implemented and the dispersion results tested in our labs and the technology transferred to our industrial partner’s manufacturing facility. Particle additives such as clay, organic and inorganic pigments were compounded and tested using USV assisted twin screw extrusion.
Cyclic olefin copolymers (COC) offer many benefits for packaging films, including stiffness, strength, transparency, gloss, heat resistance, improved thermoforming, moisture, and alcohol barrier to name a few. Using full factorial experimental design, COC glass transition temperature, COC modification and blow-up ratio were studied to show how COC influences performance of several key blown film properties. Three-layer packaging films can be engineered with modified COC to provide higher than expected toughness, strength, and stiffness. By splitting COC into at least two layers in five layer structures, further significant property enhancements are possible without changing COC content.
Sean Teller, Jorgen S. Bergström, Gregory R. Freeburn, May 2017
Finite element analysis plays a crucial role in modern engineering problems, enabling engineers to predict the response of designed parts at any point in the design process. Specifying a constitutive model that accurately captures the mechanical response of a polymer material is paramount to obtaining useful results. In order to understand the capabilities of commercial FE packages used to simulate problems involving polymers, we have tested the uniaxial response of polyamide in tension and compression over six decades of strain rate. We then calibrated four constitutive models to the experimental data: an Abaqus Parallel Rheological Framework model, the LS-DYNA SAMP-1 model, the ANSYS Bergström-Boyce model, and the PolyUMod Three Network model. We compared the performance of the four models in predicting the experimental data; the Three Network model had the lowest error. Additionally, we compared the runtime of a simple test case for each model; the ANSYS Bergström-Boyce model being the fastest.
Jan Teuwsen, Sebastian Goris, Tim A. Osswald, May 2017
The deformation of the material during injection molding of fiber filled composites causes a process-induced change in the fiber configuration. The local fiber orientation, fiber concentration, and fiber length within the molded part varies in thickness direction and along the flow path. This heterogeneous fiber microstructure inevitably results in anisotropic and locally varying mechanical properties. This paper presents a detailed experimental analysis of the microstructure of long glass fiber reinforced polypropylene (PP) plates and its influence on the mechanical properties. Large and thin center-gated plates are injection molded with three different nominal fiber concentrations (20, 40, and 60 wt%) and an initial fiber length of 15 mm. The analysis comprises local fiber orientation, fiber concentration, and fiber length measurements conducted by means of advanced measurement techniques, including micro-computed tomography (µCT) and digital image processing. Tensile test results reveal the correlation between the process-induced fiber configuration and the mechanical properties. The results of this experimental study verify a distinct seven-layered fiber orientation pattern for industry relevant nominal fiber concentrations. Besides a nominal fiber concentration and flow length dependent reduction of the average fiber length, the measurements suggest a non-uniform fiber orientation and fiber concentration distribution through the part thickness and along the flow path. Tensile test results show that tensile modulus increases with nominal fiber concentration, whereas tensile strength does not increase above 40 wt%. The process-induced fiber configuration causes a larger degree of anisotropy of the mechanical performance in high fiber-filled components (40 wt% and 60 wt%).
Joel Thambi, Julien Cathelin, Erik Stam, Sepehr Harsiny, Tim van Erp, May 2017
Lifetime evaluation methodologies are gaining more focus and importance in the area of fiber reinforced engineering thermoplastics. Plastic applications are potentially subjected to harsh environments, where the lifetime of components can be significantly reduced. Failure due to fatigue and its consequent lifetime evaluation is particularly based on empirical studies, due to the interaction of multiple factors. The methodology proposed here based on 3D-optical techniques together with digital image correlations (DIC), establishes a generalized energy based fatigue model. The methodology is illustrated on a short fiber reinforced plastic (SFRP) specimen, typically used as a representative part in pressurized fluid applications. This fatigue model will include different influential parameters like ????-ratio, pressure, temperature, and the presence of a weldline, which are seen as critical parameters for failure. The fatigue model is developed using algorithms with surface strain energy density (SSED) that acts as a damage parameter of the component lifetime.
Plastic sheet is prestretched in a plane strain fashion as predicted by the Mooney-Rivlin constitutive equation of state. Once the plastic sheet is heated to its desired thermoforming temperature range, it is ready to be stretched into on onto the mold. The sheet is stretched differential pressure across its surface. To achieve a more uniform part wall thickness the sheet is often prestretched. Prestretching is achieved either by differential air pressure or by mechanic means. In the latter case, a shaped solid is pressed into the sheet prior to applying differential pressure. The solid, usually referred to as a plug or pusher, stretches the sheet into or over the mold, prior to the sheet touching the mold surface. After I briefly discuss the general characteristics of the stretching of thermoplastic sheet during thermoforming, I focus on the plastic sheet response during the mechanical prestretching phase of the thermoforming process.
84 countries and 60k+ stakeholders strong, SPE unites
professionals worldwide – helping them succeed and strengthening their skills through networking,
events, training, and knowledge sharing.
No matter where you work in the plastics industry value
you're a scientist, engineer,
technical personnel or a senior executive-nor what your background is, education, gender, culture or
age-we are here to serve you.
Our members needs are our passion. We work hard so that we
can ensure that
everyone has the tools necessary to meet her or his personal & professional goals.
Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.