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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Conference Proceedings
Geometrical Effects On Fiber Micro-Structure Variations And The Influences On Long Fiber Reinforced Thermoplastics (Frt) Parts
Chao-Tsai Huang, May 2018
Due to its great potential and capability, the fiber-reinforced thermoplastics (FRT) material and technology have been applied into industry recently. However, due to the microstructures of fiber inside plastic matrix are very complex, they are not easy to be visualized. The connection from microstructures to the final shrinkage/warpage is far from our understanding. In this study, we have performed a benchmark with three standard specimens based on ASTM D638 where those specimens have different gate designs. Due to the geometrical effect, the warpage behaviors are quite different for those three specimens. Although we expect long fiber reinforced to enhance strength, it causes one specimen warped downward and bended inward, another warped upward, and the other slightly upward at the same time. The difference might be due to the interaction of the entrance effect of molten plastic with fiber content to cause high asymmetrical fiber orientation distribution (FOD). Moreover, the experimental study is also performed to validate the simulation results. From short shot testing to the warpage and bending measurement for each individual model, overall, the tendency for both numerical simulation and experimental results is in a reasonable agreement. However, some deviation still existed which needs for further study.
Experimental Study On Fiber Matrix Separation During Compression Molding Of Fiber Reinforced Rib Structures
Christoph Kuhn, May 2018
The use of long fiber reinforced polymers in compression molding has significant advantages for application in automotive large scale production due to its suitability for cost-effective, low fiber attrition production. During processing, fiber reinforced material is compression molded into geometries with complex features like ribs, bosses and connector points. Inside ribbed structures, earlier experiments have shown significant deviations in fiber content with longer fibers. These deviations are caused by increasing fiber interaction, leading to a separation of fiber and matrix phase during flow – the phenomenon of Fiber Matrix Separation (FMS). While these early experiments have exposed the leading factors on the appearance of FMS, a deeper understanding of the observed effects is necessary. In the presented paper, experiments in compression molding with a simple ribbed plate tool are conducted. During the experiments, the initial fiber length and charge location are varied and their influence on the fiber filling during processing is investigated. Therefore, the compression molded components are investigated regarding their fiber properties with pyrolysis and CT imaging. Results show, that the fiber length is the most significant factor on FMS in complex geometries and leads to extensive FMS. Generally with longer fibers, more FMS appears. Furthermore, the initial charge position is vital for fiber behavior during filling. With the charge positioned underneath the rib, fibers are prone to display excessive bridging, leading to an increase in FMS. With longer flow paths, the fibers are able to align inside the polymer flow and are smoothly dragged into the upper rib regions with less interaction. A generous rib base radius supports the fiber access and minimizes FMS. In addition to the fiber property analysis, mechanical component tests are conducted. Test results show a significant decrease in mechanical properties due to FMS. In conclusion with the earlier experiments, design guidelines are derived and furthermore, the gathered information is applied to a simulative approach on FMS with a Mechanistic Model.
Fundamental Understanding Of Tribological Behavior Of Multiphase Polymeric Systems Using Fem Modeling
Mohammad Hossain, May 2018
Three-dimensional finite element method (FEM) modeling has been carried out to study the influence of dispersed particles on tribological behavior of multiphase polymeric systems. Specifically, effects of particle type and volume fraction on scratch behavior of multiphase polymeric systems have been investigated. The FEM findings correlate well with the experimentally observed scratch-induced damages. The results show that type and concentration of particles can drastically affect the stress and strain field development during the scratching process.
Effects Of Different Fillers On The Thermo-Mechanical Properties And Coefficient Of Linear Thermal Expansion Of Polypropylene Composites
Manjusri Misra, May 2018
We study and report on the effect of different fillers on the coefficient of linear thermal expansion (CLTE) of polypropylene (PP) by melt extrusion technique. We examine and review the effect of some fibers such as glass fiber and carbon fibers as well as traditional mineral filler like talc. Moreover, we study the effect of new biocarbon as an environmentally friendly filler on the CLTE of neat PP and compare with the previous samples. On the basis of these results, properties and potential applications of PP composites are discussed.
Experimental Verification On Moldex3D Fiber Orientation Prediction In High Fiber Concentrations
Huan-Chang Tseng, May 2018
An accurate predictive analysis of fiber orientation is crucial for practical injection molded fiber composite applications. Recently, an objective model, iARD-RPR (Improved Anisotropic Rotary Diffusion and Retarding Principal Rate), has been significant to provide anisotropic distribution of fiber orientation, such as the well-known skin-shell-core structure. The micro-computed tomography (micro-CT) scan is state-of-the-art technique for measuring a very high 3D resolution of a specimen’s fiber orientation data. According to the micro-CT experiments and injection molding simulations with the iARD-RPR computation, we investigate changes in fiber orientation distributions for different fiber concentrations in rectangle plate. Comparisons of the fiber orientation predictions with the validated experimental data are also presented herein.
Synthesis, Characterization And Water Application Of Microcellular Injection Molded Ppgma/Mmt Nanocomposites
shyh-shin hwang, May 2018
This study investigated the effects of MMT (0.5, 1, 3 wt%) loading on thermo-mechanical, adsorption properties of microcellular injection molded PPgMA nanocomposites. The injection molding process was done by non-foam and microcellular molding. Results showed that the dispersion from TEM pictures, some of MMT are intercalated and some of them are exfoliated structures. This 0.5 wt % loading of MMT had the best tensile strength for solid molding while it is 1.0 wt% loading for microcellular molding on PPgMA material. This is the results of MA grafted PP. Tensile strength is related to the filler dispersion in the matrix. Good dispersion resulted in good tensile strength. It had the highest storage modulus for 0.5 wt% MMT loading PPgMA/MMT nanocomposites from the DMA test results. TGA results showed that thermal degradation can be increased with addition of MMT into matrix. SEM morphology showed that with addition of MMT, cell size decreased and cell density increased. Heavy metal adsorption test showed that MMT can adsorb Pb(II) more efficient than that of neat PPgMA.
Preparation Of Polypropylene Single-Polymer Composites With Graphene Nanoplatelets By Film-Stacking
Mingwang SHAO, May 2018
Polypropylene single-polymer composites (PP SPCs) are the materials where both the reinforcing phase and the matrix phase are PP. Graphene nanoplatelets (GNPs) have good mechanical properties because of its unique structure. In this study, GNPs were used as one kind of nanofiller to add in PP SPCs to improve its thermal properties and tensile properties. The PP-GNPs SPCs were prepared by film-stacking method. Differential scanning calorimeter experiments (DSC) were executed to determine the hot pressing temperature and investigate the thermal properties. Influences of the GNPs content on the tensile properties of PP SPCs were studied through the tensile tests. The results show that the melting peak temperature and tensile properties increase with the increase of GNPs content.
An Investigation Of Rheological Properties Of Polypropylene Single-Polymer Composites
Mingxing Yu, May 2018
Polypropylene single-polymer composites (PP SPCs), whose matrix and reinforcement came from identical type of polymers, were fabricated by an approach of applying undercooled polymer melt. The undercooling method could enlarge the processing temperature windows thus realize the fabrication of SPCs without destroy the reinforcement structures. Rheology could be used in the processing of the SPCs, however there is little investigations. This work was done with the aim to investigate the effect of undercooling compaction temperature from 125 oC to 145 oC on rheological properties of PP SPCs by dynamic rheological measurements. The linear viscoelastic range (LVE) was measured for strain sweep. And it was found that complex viscosity of PP SPCs increased as the temperature increased, whereas the storage modulus decreased during frequency sweep. Moreover, the photography of morphology before and after tests revealed a positive correlation between the degree of shrinkage and the compaction temperature. Overall, the effects of temperature on rheological and morphology properties of PP SPCs are strictly dependent upon the molecular structure parameters.
Influence Of The Fiber-Matrix-Interaction On The Fracture Behavior Of Regenerated Cellulose Fiber Reinforced Polypropylene
Jan-Christoph Zarges, May 2018
This investigation focuses on the fiber-matrix-interaction of man-made cellulose fibers (RCF) in a PP matrix with an additional MAPP content using an energetic evaluation of the single fiber pull-out test (SFPT). Furthermore glass fibers were characterized for reference purposes. With the SFPT the interfacial shear strength (IFFS) and the critical fiber length (lc) as well as the consumed energy of a fiber pull-out and a fiber rupture were determined. In a following step the resulting values of lc were related to the fiber length distribution in injection molded specimens. It was shown that, based on the longer RCF in the specimen, theoretically more fiber ruptures appear in the RCF composites. But the RCF composites also contain a higher number of long fibers, consuming a higher amount of energy by being pulled out during a composite failure. The length-dependent consumed energy of a fiber pull-out was increased by using MAPP but simultaneously the critical fiber length was significantly reduced.
Suppression Of Necking In Lldpe/Seps Rubber Bilayer Laminates
Sachin Velankar, May 2018
Semicrystalline plastics often show necking and drawing behavior in tension. In contrast, rubbery materials do not show necking, but instead stretch homogeneously. We examine the behavior of bilayer laminate composites of linear low density polyethylene (LLDPE) and styrene-ethylene/propylene-styrene (SEPS) rubber to test the extent to which the SEPS can modify the necking behavior of the LLDPE. Video recordings of tensile tests on dog-bone shaped samples were analyzed by a Digital Image Correlation (DIC) technique to quantify the degree of non-homogeneity in deformation. The LLDPE showed severe necking with a natural draw ratio exceeding 5. Upon bonding it to a rubber layer, the natural draw ratio reduced significantly. With a sufficiently large SEPS thickness, the neck was almost completely eliminated and the sample reverted to nearly-homogeneous deformation. We present a simple 1D model of the mechanics of the bilayer laminate in which the force within the bilayer is treated as a sum of the force of a Mooney-Rivlin rubber layer and an elastoplastic layer. The model predicts the decrease in natural draw ratio and the elimination of necking as rubber thickness increases, consistent with experiments.
Isolating The Effect Of Polymer-Filler Interaction On Polymer Composite Property Enhancement: The Example Of Polypropylene/Halloysite Hybrids
Tong Wei, May 2018
We prepare polypropylene (PP) composites with both pristine halloysite nanotubes (p-HNT) and PP grafted halloysite nanotubes (PP-g-HNT) using two processing techniques, solid-state shear pulverization (SSSP) and melt mixing. We address the role of isolated polymer-filler interaction effects on polymer nanocomposite property enhancement at similar, high levels of filler dispersion. As demonstrated by microscopy and rheology, nanocomposites prepared by SSSP with different fillers have very similar, well-dispersed states, eliminating differences in dispersion as a factor in property enhancements. The well-dispersed PP/PP-g-HNT nanocomposites exhibit a broad range of properties that are superior to those of PP/p-HNT, including tensile strength, PP non-isothermal crystallization onset temperature, and isothermal PP crystallization half-time. However, the Young’s modulus is the same regardless of filler modification. Only superior filler dispersion contributes to Young’s modulus enhancement in nanocomposites.
Crystallization Behavior Of Poly(Lactic Acid) Composite Nanofibers By Annealing
Jian-hua Hou, May 2018
Poly(Lactic acid) (PLA) is a typical biodegradable and bioabsorbablesemicrystalline material and has drawn extensive attention due to its excellent biodegradability, biocompatibility and mechanical properties. The semicrystalline PLA has a low crystallinity and the crystallite is imperfect which affects the properties of PLA parts. In this study, the effect of annealing on the composite nanofiber of PLA and graphene oxide(GO) and carbon nanotubes(CNT) is investigated. Nanofibers of PLA, PLA/GO and PLA/CNT are successfully prepared. A serials of characterization on crystalline morphology on the nanofibers suggest that the addition of GO and CNT enhance the crystallization of PLA and the enhancement effect of GO is better than that of CNT. Annealing improves the degree of perfection and crystallinity of PLA nanofibers. With the increased annealing temperature, the improvement becomes more significant. The results reveal that annealing is a favorable method to tuning the crystalline of PLA and its composite nanofibers, which allows to optimize other properties for the nanofibers.
High Confidence Performance Predictions For Hybrid Thermoplastic Composite Applications
Subhransu Mohapatra, May 2018
Multi-material hybrid structures that blend continuous fiber thermoplastic composites with lower-cost options such as chopped fiber thermoplastic composites and metals is an attractive proposition for many industries, due to the potential dual benefits of lower weight and cost. High confidence in performance predictions is one of the key enablers to convert this potential into successful industry adoption. However, chopped and continuous fiber thermoplastic composites pose numerous challenges for accurate predictions, due to the inherent complexity of the material behavior. To establish confidence in predictions, a test component was designed that can be produced in a representative production process and can validate all of the many different composite failure modes. Predictive simulation procedures in multiple industry-standard commercial software platforms were established to cater for the needs from multiple industries and loading scenarios. Component level static and dynamic tests were performed on the test component and were compared with the simulation results to validate the methodology. Excellent correlations between the simulation model and the physical test results paves the way for using the methodology for yet-to-be-designed components.
The Influence Of Hygrothermal Aging On The Material Properties Of Endless Fiber-Reinforced Thermoplastics
Matthias Huettner, May 2018
The ambition of developing innovative and technically high-quality products is one of the main reasons for the growing use of fiber-reinforced plastics (FRP) in industry. In particular, the opportunity to combine lightweight construction with a high degree of design freedom and functional integration leads to the preferred use of composite materials in the automotive and aerospace industries.During the operation time the composite parts are exposed to continuously changes of environmental influences which lead to aging of the polymers. This includes frequent temperature changes, dampness, saline media and mechanical loads for instance. The aging effects, caused by the interaction with the surrounding media, result in various changes of the material properties. Strength losses, embrittlement, degradation of the molecular weight or optical changes are some examples which can occur during the aging process and may induce a prematurely failure of the composite parts.In order to predict the life time of those components, the effects of the aging process and the influences on several material properties have to be known. Hence, in the following the environmental aging of a woven fabric reinforced, a short glass fiber-reinforced and an unreinforced polyamide 6 will be investigated and the influences on the material properties will be characterized.
In-Situ Vitamin C Reduction Of Graphene Oxide For Preparing Flexible Tpu Nanocomposites With High Dielectric Permittivity
Han-xiong Huang, May 2018
Flexible thermoplastic polyurethane/reduced graphene oxide (TPU/rGO) nanocomposite sheets are prepared via in situ vitamin C reduction. X-ray photoelectron spectroscopy spectra suggest a successful reduction of the GO by vitamin C, which can enhance the interfacial polarization ability of the resultant rGO layers. X-ray diffraction patterns and transmission electron microscopy image indicate a well exfoliation of the rGO layers in the TPU matrix. This results in the formation of a rheological percolation structure in the nanocomposite with 0.75 vol% rGO, as suggested by the rheological properties. The enhanced interfacial polarization ability and the formed percolation structure of the rGO layers in the TPU matrix allow for constructing a large network of micro-capacitors. Thus high dielectric permittivity (ε′ = 151 at 1 kHz) is obtained for the nanocomposite sample with only 0.75 vol% rGO.
Draping Behavior Of Uni-Directional Tape Laminates – Experimental And Numerical Studies
Sandeep Kulkarni, May 2018
Today continuous fiber thermoplastic composites are used in various applications across the industry due to its excellent mechanical properties, which offer significant weight saving potential. In addition, thermoplastic composites are well suited for mass production and easily integrated in a hybrid overmolding processes. This enables the industry to manage cost while delivering performance. Forming or draping is an important step in the manufacturing of continuous fiber prepreg or tape based thermoplastic material forms. Different studies indicate that forming of multi-layer unidirectional (UD) laminates may result in out-of-plane wrinkling and in-plane fiber misalignment. Thus, understanding the forming behavior and having a simulation method in place for its prediction is essential for widespread acceptance of this new material. This paper presents experimental forming studies on multi-layer GF-PP UD thermoplastic composite laminates. The influence of the tool geometry and the laminate layup on forming behavior are studied. The results show that the current GF-PP UD composites are easy to shape, resulting in a large processing window. However, in some cases process induced defects arise, such as out of plane deformation, fiber waviness, ply splitting, bridging, etc. whose influence on part performance needs to be assessed and quantified. Forming simulations are performed on UD tape based laminate composites in PAM-FORM software using a visco-elastic material model, dedicated to continuous fiber composites. Numerical studies show that the predicted process induced defects such as fiber waviness and wrinkling patterns are in good agreement with experiments. With increased confidence on such a computational framework, thermo-forming simulations can help identify critical spots in the product and process design at an early stage and reduce costly product development times. Keywords— Continuous fiber composite, Unidirectional composite, Thermoforming, Wrinkling, Ply splitting, Marcelling, Numerical simulation
Effect Of Freeze-Drying On The Morphology Of Dried Cellulose Nanocrystals (Cncs) And Tensile Properties Of Poly(Lactic) Acid-Cnc Composites
Nicole Stark, May 2018
Cellulose nanocrystals (CNCs) are routinely produced as aqueous suspensions. These are then typically freeze-dried in order to be added into polymeric composites using melt-blending. However, dispersing freeze-dried CNCs into hydrophobic polymers is a challenge. In this study, our objective was to advance our understanding of the impact of freeze-drying methods on the morphology of dried cellulose nanocrystals (CNCs), and on the tensile properties of the resulting PLA-CNC nanocomposites. CNCs were prepared as aqueous suspensions with 10.7% solids content using a sulfuric acid method, and freeze-dried using a procedure typical to our laboratory. In addition, the CNC aqueous suspension was diluted to 1% and directly freeze-dried or sonicated for 10 or 30 minutes, flash frozen, and freeze-dried. The particle size and morphology of the CNCs before and after freeze drying were determined by microscopy. CNCs were then incorporated into PLA using melt-blending extrusion and injection molding. The PLA-CNC nanocomposites were tested for thermal and mechanical properties. Before freeze-drying, CNCs were nano-scale, while agglomerations were observed after freeze-drying. The agglomerate sizes were reduced with dilution and/or increased sonication time, with fibrillar structures observable after sonication. PLA-CNC composites containing CNCs that were subjected to dilution, sonication for 30 minutes, flash frozen and freeze-dried had higher tensile modulus and strength compared with the other treatments.
Property Characterization Of Injection Molded Hybrid Composites
Gangjian Guo, May 2018
Hybrid composites with two or more fillers offer advantages such as improved mechanical properties and balanced performance/cost ratio. They have been increasingly used in many industries such as automotive and aerospace industry. The properties of hybrid composites largely depend on the matrix material, the type and the content of fillers, the filler distribution in the matrix, and the interfacial bonding between the fillers and the matrix. Wood fiber (WF), glass fiber (GF), and carbon fiber (CF) have been used in a variety of polymer composites applications. This study applies the injection molding process, and investigates the tensile properties, water absorption, burning behavior, and surface roughness of pure polypropylene (PP), PP/WF composites, PP/GF composites, PP/CF composites, PP/WF/GF hybrid composites, and PP/WF/CF hybrid composites. This study would provide guidance for choosing composites for different applications in consideration of cost and performance.
In-Situ Synthesis Of Poly(Ethylene Terephthalate) Graphene Nanocomposites
Vahid Shabafrooz, May 2018
Fabrication of graphene-based poly(ethylene terephthalate) (PET) nanocomposites through in-situ polymerization is demonstrated. With the goal of improving the incorporation and dispersion of graphene in the PET matrix, an ultrasonic exfoliation method was employed in ethylene glycol (EG), a raw material used in PET synthesis. The graphene EG dispersions were used as precursors to fabricate PET nanocomposites. Transmission electron microscopy (TEM) was used to evaluate the level of exfoliation of graphene in the dispersions. Mechanical testing showed at 2 wt. % concentration of graphene, the elastic modulus and the tensile strength of PET increased by 22% and 10%, respectively. Differential scanning calorimetry (DSC) measurements were performed to evaluate the percent crystallinity, and it was observed that addition of graphene at 2 wt. % increased the crystallinity of PET by 33%. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to study morphology and microstructure of the PET nanocomposites, respectively.
Virtual Characterization Of Prepreg Platelet Length Effect On Tensile Properties Of Coupons With Stochastic Morphology
Sergey Kravchenko, May 2018
Progressive failure analysis is herein used to study the damaged deformation up to ultimate failure in prepreg platelet-based tensile coupons with stochastic morphology. Computational damage mechanics approaches (continuum and discrete) are utilized for constitutive modelling and addressing complex interacting/competing damage mechanisms. The developed failure analysis allows for virtual characterization of how the composite structure details, meaning the platelet geometry and system morphology (geometrical arrangement and orientation distribution of platelets), define the effective properties of a platelet-molded composite system, its stiffness, strength and variability in properties.
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