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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Comparison of the Processing Properties of Thermoplastic Elastomers and Thermoplastics Using Gas Assisted Injection Molding
The process of gas assisted injection molding (GAIM) with thermoplastic materials has been investigated comprehensively in recent years. This has been done using both experimental and numerical (mostly finite-element-method) studies. In the study presented in this paper the possibilities of using thermoplastic elastomers (TPE) within this process are shown and compared to typical thermoplastic polymers. The results include the obtained residual wall thicknesses and measurements of gas front velocities. The minimal wall thicknesses obtained with TPE materials and thermoplastics at high gas pressures within this study are of similar level. The values for lower pressure levels however are significantly influenced by the rheological properties of the particular materials. The distinctive shear thinning of the TPE materials and the Newtonian flow behavior of the thermoplastics used in this study have major influence on the melt displacement velocity and the residual wall thickness.
Ultrathin Nanolayer Films for High Energy Density, High Temperature Capacitors
Fabrication of multilayer dielectric films to improve the dielectric properties was demonstrated by combining two or more polymers as a layered structure via coextrusion process. Recently, process innovations in film production scale-up of thin nanolayered films was demonstrated at PolymerPlus. Using conventionally used film metallization and capacitor winding capabilities nanolayer film capacitor prototypes were also created. Use of high temperature and high energy density films was demonstrated in capacitor applications. Recent results on effect of multilayer film thickness and number of layers on the dielectric performance is discussed in this paper.
Nonwoven Filters via a Novel, Continuous Melt Coextrusion Process
A novel melt co-extrusion process with two-dimensional multiplication technology created a fiber-film mat with polymer layer dimensions comparable with conventional fibers. When the layers were exfoliated using a high pressure water jet delamination technique a fibrous filter media were fabricated. The filter media made from polypropylene (PP) / polyamide 6 (PA6) system exhibited microscale fibers with uniform fiber distribution and superior mechanical properties. Previously, improved filter surface area and porosity, and decreased the mean pore size was demonstrated with increasing film draw ratio prior to delamination. In current work, applications of this filter for water removal in fuel filters are demonstrated. In addition, PolymerPlus has also demonstrated fabrication of continuous large filter media sheets demonstrating scalability. This melt process based, flexible technology can be extended to other melt-processable polymers for various liquid or gas filtration applications.
Effect of Acrylic Core-Shell Impact Modifier on Processing and Thermo-Mechanical Properties of Stereocomplex Poly(lactic acid)
Injection molding grade PLLA/PDLA compounds have been developed by melt blending. The article reports in particular about influence of acrylic core-shell impact modifier on crystallization behavior, thermo-mechanical properties of the compounds and injection molding cycle time. DSC results have shown formation of stereocomplex crystalline structure in compounds. Addition of impact modifier displays no influence on melting point or enthalpy of crystalline structure. Plasticization of compounds resulted in decrease of tensile properties, however impact strength has increased. Additionally a peak of maximum loading with additive was observed. Plasticizing effect due to addition of core-shell entities was confirmed by sharp increase of elongation at break. Only marginal effect on heat distortion temperature of the compounds was found. Increasing content of the toughening agent caused lowering of materials’ flowability. Influence of impact modifier on resulting injection molding cycle time was insignificant.
Rapid Photo-Oxidation of UV-Stabilized Polypropylene Fiber Due to an External Antagonist
Polypropylene fiber in an outdoor carpet exhibited unusual photo-oxidation behavior that occurred in some cases in as little as 3 months. Degradation rate and severity were shown to be dependent on exposure to materials the carpet came into contact with after manufacturing. Other causes of increased UV sensitivity were also identified. Since the failure manifested as a consistent change in color, colorimetry was used as a simple diagnostic tool. Mechanisms for accelerated degradation are discussed whereby the effectiveness of hindered amine light stabilizers (HALS) is disrupted by external antagonists.
Effects of Supercritical Carbon Dioxide Processing on the Crystallization of Polyvinylidene Fluoride
Polyvinylidene fluoride (PVDF) is an environmentally friendly, durable and low-cost alternative to traditional piezoelectric materials in sensors and actuators. PVDF is a semi-crystalline polymer with different crystal phases. Among them, the polar ß-phase is the crystalline structure that is responsible for its piezoelectric property. Conventional technology for promoting ß-phase crystals in PVDF is mechanical stretching. In this paper, processing of PVDF with supercritical carbon dioxide (ScCO2) was investigated to examine its effect on PVDF’s crystallization behavior. In the long-run, elucidation of potential strategies to tailor PVDF’s crystal structures would help to identify feasible route to tailor PVDF’s crystalline structure for emerging applications including sensing and energy harvesting. The foam morphology of PVDF was analyzed by scanning electronic microscopy while its crystallization behavior was studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. Experimental results reveal that PVDF samples foamed at 120°C and 160°C under 2000 psi showed the highest crystallinity (54%) and volume expansion ratio (15.4 times), respectively. The crystallinity increase in ScCO2 processed PVDF represents a 16% increase over that of its compression-molded samples.
Study of Fiber Length and Modeling of Partially Compacted, Commingled Polypropylene Glass Fiber Fleece Composites
In this work we investigated the influence of glass fiber content, number of layers and initial length on the residual fiber length and the properties of partially compacted composites made of commingled polypropylene and glass fibers. Furthermore, we wanted to develop a model to predict the properties of such composites. We found, that despite of a significant degradation of fiber length due to the processing, increasing glass fiber content and initial fiber length leads to higher portions of longer fibers and mechanical properties are improved, but only when the porosity remains among certain levels. Porosity is therefore the critical factor influencing this type of composites. The modeling of the elastic modulus was found satisfactory for composites with porosity volume content under 0.5.
Mechanical, Thermal and Electrical Property Enhancement of Graphene-Polymer Nanocomposites
In this work, NanoXplore’s proprietary graphene nanoplatelets, heXo-G V20, are melt-extruded into thermoplastics LLDPE, HDPE and TPU. Graphene is shown to effectively increase the stiffness and the strength of a matrix TPU. The flexural and tensile moduli increase with loading levels of graphene whereas the tensile strength increases at low loading levels, but does not further increase at higher graphene concentrations. A ten fold increase in thermal conductivity was achieved by adding heXo-G V20 graphene to LLDPE matrix. The thermal conductivity percolation threshold was reached at 10% loading. At 1% loading of graphene the onset of the decomposition temperature and maximum weight loss temperatures were shifted by about 50°C, significantly improving the thermal stability of the PE matrix. Fourteen orders of magnitude increase in electrical conductivity of HDPE was obtained at 30% loading of graphene. Excellent EMI shielding of 40 dB was achieved with 20 wt% addition of graphene in a TPU matrix.
Influence of Glass Transition Temperature on Mechanical and Self-Healing Behavior of Polymers Bearing Hindered Urea Bonds
Considerable interest has been placed on polymers which can intrinsically self-heal. Numerous studies have shown that polymer networks bearing dynamic covalent bonds exhibit the ability to self-repair. The focus of this paper is to describe the synthesis and characterization of polymer networks of varying rigidity bearing hindered urea bonds (HUB) based on 1-(tert-butyl)-1-ethylurea (TBEU). Results indicate that the partial substitution of Hexamethylene Diisocyanate (HMDI) with an aromatic diisocyanate (m-Xylylene Diisocyanate, XDI) results in a predictable increase in Tg and a corresponding increase in both modulus and tensile strength at break. Furthermore, polymers containing up to 50mol% XDI were shown to self-heal, though the efficacy decreases with increasing XDI content at constant healing conditions (60°C/12 hours).
The Composite of High-Density Polyethylene/Polycarbonate Prepared by a New Co-Rotating Non-Twin Screws Extruder
In this paper, the composites of High-Density Polyethylene /Polycarbonate were prepared by a new co-rotating non-twin screws extruder. The WANCE electronic universal testing machine, Anton Paar rotational rheometer, differential scanning calorimetry analysis and scanning electron microscope (SEM) were used to test composites in our experiments to show the ability and characteristic of new equipment. The results show that the new equipment has excellent mixing ability and the potential to replace the traditional twin-screw extruder with the development of composite materials.
Statistical Characteristics in Uniaixal Ductile and Semi-Brittletensile Fracturein Polypropylene Films
The statistical nature of the tensile fracture behavior of isotactic polypropylene with spherulite morphology was investigated at different tensile speeds. The probability distribution curves of the fracture data (fracture time, fracture stress, fracture toughness) from more than one-hundred tests at room temperature (25°C) and at a lower temperature (4°C) near Tg were analyzed using Gaussian and Weibull distribution curves, respectively. The specimen tested at lower temperature exhibited a shorter fracture time and a higher fracture stress, whereas a similar toughness resulted for the specimen tested at 25°C. These results indicate that the fracture toughness is a criterion for fracturing under uniaxial tension, and is independent of the external test conditions, regardless of the tensile speed or temperature. The specimen tested at 4°C had a shorter craze length, which could be the reason for the stress concentration on the test sample.
Advanced Dynamic Mechanical Analysis of a Tire Sample by Nanoindentation
The viscoelastic properties of a tire sample are comprehensively studied by dynamical mechanical analysis (DMA) using nanoindentation technique with the Nanovea Mechanical Tester. We found that the tire possesses different viscoelastic mechanical properties across the tire layers. Such strategical distribution of the hardness and complex modulus at different layers meets the functionality requirements of the tire. The tire shows increased storage and loss modulus as the loading frequency increases from 0.1 to 20 Hz. The DMA frequency sweep test provides useful information on the viscoelastic behaviors of the tire running at different speeds, which is essential in improving the performance of tires for smoother and safer rides.
Mechanical Properties of Glass Fiber/ Basalt Fiber Reinforced Polypropylene Hybrid Composites Fabricated by the DFFIM Process
The direct fiber feeding injection molding (DFFIM) process is a kind of new ways which the thermoplastic material is injected with continuous fiber and molded in one operation. The objective of this research is to investigate the mechanical performances of Glass Fiber/ Basalt Fiber Reinforced Polypropylene Hybrid Composites. In this work, the hybrid composites were manufactured by DFFIM Process, where GFPP pellets were used as basic reinforcements system, continuous basalt fiber strands were used as hybrid fibers, and the PA6 and MAPP were used as coupling agent during fabrication. Mechanical testing like tensile test were carried out to investigate the hybrid effect. Optical microscope observation was taken to measure and count the fiber length. Scanning electron microscope observation of cross section was used to analysis the combination of fiber and resin. The result shows that the reinforcement of Basalt fibers and Glass fibers hybrid composites significantly influencing on the mechanical properties of the composites, and it’s found that the addition of PA6 and MAPP could also improve the mechanical properties of the GFPP/BF hybrid composites to some extent.
Improving the Adhesion of Polyolefin Elastomers
The adhesion of polyolefin compounds to polar substrates is one of the on-going challenges for many consumer and industrial applications. Due to differences in polarity and surface energy, the bonding of polyolefin thermoplastic elastomers to engineering plastics such as PET, PA, PC, PU, and other polar materials are largely unresolved. This paper discusses the development of an adhesion primer for the surface treatment of polyolefin elastomers to improve its adhesion to PET and PC in lamination and coating processes. Results indicate that adhesion primers containing maleic anhydride functionality or a combination of MAH and chlorine functionality are effective for bonding PET and PC to a polyolefin. Overall, a combination of a surface adhesion primer and the application method can be an effective solution to provide the needed bonding. Such technology can be further applied to resolve the adhesion challenges of polyolefin elastomers to polar fabrics and coatings.
Biodegradability of PLA in Compost Environment
Considering to environment issues, PLA is one of the most popular plastic and commonly used. This study is going to study the biodegradability after produced by compression molding and buried the specimens in the soil and compost condition within 7 weeks. The specimens was produced and followed pattern as following ASTM D882. Specimens are tested the changes of molecular weight, thermal properties and appearance week by week. The results show that PLA could be dissolved and disintegrated in the period. For the thermal properties, the decomposition temperature, Tg and Tm are all decreased by week and week. Molecular weight is conducted by GPC, it shows the molecular weight are dramatic decreasing from 115K to 5.1K of Mw within 7 weeks. PLA happens to absorbed moister, crystallized in high temperature, debonding, cracks, separated pieces, and disintegrated, and finally dissolved in the environment. So the PLA specimens are verified that PLA can absolutely and completely disintegration in the compost environment.
Optimizing Process Condition of Resin Transfer Molding: Determining Material Properties for Numerical Simulation
Herein, we present the recent development in permeability measurement by an optical visualization method. We applied this technique to investigate materials commonly used in wind turbine industry, such as different types of fiber mats, distribution medium, PVC core material. Wind turbine industry utilizes predominately resin transfer molding (RTM) process to manufacture the components. The traditional-trail-error method in this case is not practical due to the high cost of producing the components. To the best of our knowledge, this is the first example of using an optical method in conjunction with a simulation tool to obtain out of plane (K33) permeability. The results demonstrate the promising potential of permeability measurement by the optical visualization method, and great relevance to industrially important processes such as RTM. The measured material properties are then used in process simulation to obtain optimal process conditions of RTM.
Predict and Solve Stress Mark on Product's Cosmetic Surface Using Controlled Sequential Valve Gating Simulation
Surface defect like stress mark has been a major issue in automotive part produced by Sequential Valve Gating (SVG). This defect may still even show up as uneven gloss after painting and drying, which is critical for cosmetic surface appearance. To solve it, controlled SVG has been developed by which the valve pin's velocity profile can be set. Nevertheless, manufacturers still face challenges in optimizing their velocity profile to avoid the defect. Moldex3D adopts a moving mesh boundary technique to support the pin movement simulation. Viscoelastic (VE) fluid property is also considered to compute and illustrate the appearance of flow-induced residual stress for the stress-mark prediction. The results show that the controlled velocity profile can eliminate the residual stress pattern at the gate which can be an indicator to resolve the uneven gloss for a spoiler product.
Ink-Wash and Warpage Defect Prediction from the in-Mold Decoration Process Simulation
We introduced in this paper a simulation tool designed to predict the most common defects related to the in-mold decoration process. Ink-wash is the most obvious aesthetic problem caused by high temperature or high shear from the incoming melt. Warpage is another dimensional uncertainty defect due to the poor heat conduction of the film. Overcoming these problems often requires mold fixing including critical gate location change. Mold filling simulation could help identify these potential problems in the early mold design stage. However, conventional simulation techniques require tedious work of thin layer mesh making of the decoration film. It is therefore essential to develop a quick preprocess tool without losing simulation accuracy.
Long Fiber Orientation and Structural Analysis Using Moldex3D, Digimat and ABAQUS Simulations
Long fiber-reinforced thermoplastic composites open up exciting new possibilities for the green automotive industry, owing to excellent mechanical properties, advantageous weight reduction, and economical fuel consumption. However, fiber microstructure including fiber orientation and fiber length, is a very critical issue to cause anisotropy in mechanical properties and warps. For an injection-molded, long-glass fiber composite part, we use Moldex3D to obtain an accurate fiber orientation prediction. Thus, mechanical properties depending on the predicted orientation is calculated via Digimat. It is ultimate to explore changes in stress with respect to strain in the ABAQUS structural analysis. All of the predictions are compared with experiments herein.
Effect of Multi-Walled Carbon Nanotubes on Poly(e-Caprolactone) Foaming Behavior
In this paper, we investigated the effect of multi-walled carbon nanotubes (MWCNT) on the foaming behavior of poly(e-caprolactone) (PCL). The PCL/MWCNT nanocomposites prepared using HAAKE Rheometer, and the resulted composites were subsequently foamed using supercritical carbon dioxide (Sc-CO2) foaming technology. Results showed that the involvement of MWCNT promoted crystallization of PCL matrix and improved the crystallinity of PCL matrix, which is attributed to the enhancement of melt strength. Morphological analysis presented that the MWCNT was well-dispersion in the PCL matrix at low loading. In Sc-CO2 foaming process, the addition of MWCNTs led to higher cell densities, smaller cell sizes and uniform cell morphology in the composite foams. The results indicated that the MWCNT nanoparticle acted as a heterogeneous nucleation agent in the PCL matrix, and provided more nucleation site during the foaming process.
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