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.
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?
Not an SPE member? Join today!
| = Members Only |
|
Categories
|
Conference Proceedings
The Effect of Reprocessing on Mechanical Properties of Polypropylene
Polypropylene (PP) was injection molded up to 20 runs to study the effect of recycling procedures. The influence of the recycling was studied by observing changes in melt viscosity, tensile and impact resistance properties. The main effect of recycling was decrease in melt viscosity, which is attributed to molecular weight reduction. The observed degradation processes only slightly affected the small strain properties of the materials studied. However, break properties were affected apparently. All the tensile properties related to breaking as well as impact resistance of recycled polypropylene decreased with recycling.
Formation of Part Defects in Water-Assisted Injection Molding (WAIM): Influence of Process and Material Parameters
Water-assisted injection molding (WAIM) enables the production of hollow or partially hollow products, having a higher quality and lower process cost when compared to products produced with other and earlier developed plastic processing techniques. However, the occurrence of (unwanted) defects in the final product is one of the current limitations of the WAIM process, for which in available research until now no clear explanations exists. In this study, the influence of process and material parameters on the occurrence of part defects was examined in a pre-defined reference experiment. With a qualitative defect analysis, it was found that within the reference setting a high water temperature, a low melt temperature and water holding pressure as well as the addition of nucleating agents are more favorable. The experimentally observed changes in defect occurrence, under influence of the applied parameter variation, can herewith be explained with the proposed definitions of the different defect types and their responsible formation mechanisms. In this way, the principle mechanisms behind the formation of part defects are enclosed in these definitions and mechanisms, which hence contribute to a more fundamental understanding of the WAIM process.
Binary Blends of Cycloolefin Copolymers
Binary blends of different grades of cycloolefin copolymers (COC) were prepared at different compositions via compounding in a twin-screw extruder. Thermal, mechanical and rheological properties of the COC blends were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rotational rheometry. Results revealed the differences in the miscibility of different grades of COCs. This could be attributed to differences in the microstructures of the COCs determined by their synthesis method (catalyst type) and norbornene content of each component. Blends of Topas 8007 and Topas 5013 were immiscible but they were compatible to a certain degree. Two distinct Tg’s were observed at DSC and DMA, with a slight shift upon changing the composition of the blends. DSC data was used to model this behavior using two parameter Kwei model for the prediction of the Tg for the immiscible COC blends (8007/5013). Rheology data of the blends revealed that the phase inversion occurs at 45%-55% for the blends of two different Tg COCs. On the other hand Topas 8007 and Topas 6013 blends were miscible and single Tg was observed at DSC. Fox equation was used to model the Tg behavior of the miscible blends and the experimental results were in close agreement with the model.
Physics-Based Film Blowing Modeling to Enhance Empirical Film Property Predictions from Polymer and Processing Parameters
In this paper physics-based modeling of the film blowing process is combined with empirical film property relations. A hybrid approach for polymer processing-property prediction is provided. A continuum mechanics model is implemented to enhance the nominal fabrication input with calculated stresses, strains, and related parameters. Nominal and calculated parameters are candidate inputs for empirical property prediction. Data is used from various (linear low-density polyethylene) LLDPE resins, run under different conditions at laboratory and commercial-scale film blowing lines. The results based on temperature-dependent Newtonian constitutive relation indicate that the strategy lead to significant improvement of a quality of prediction of certain film properties.
Curing Study of a Green" Thermosetting Resin"
A series of green" thermosetting resins oligomers of bis(hydroxyalkylene)-2-mercaptosuccinate has been reported recently [12]. Curing in these thermosetting resins results from crosslinking via pendant thiol groups. As part of an effort to realize and assess the potential of these resins as sustainable materialsthe curing process was investigated using differential scanning calorimetry (DSC) and rheology. The progression of physical and mechanical properties such as the glass transition temperature (Tg) and the shear moduluswas monitored as a function of time and temperature. Tg of the resin was found to increase with curing and the averaged Tg of the fully cured resin was found to be 72.6 K ± 1.2 K higher than uncured resin. The increase in Tg corresponded with the change in rheological properties. The shear modulus obtained for fully cured samples reached a high modulus of 6.5 × 106 Pa at 200 °C. Additionallythe gel point was measured from the crossover of the storage and loss moduli. Based on the gel points the apparent activation energy of curing also was determined."
Unexpected Dependence of Hydrolytic Performance of PC/ABS Blends: Specificity of Buffer Cation Type
Compromised performance of hydrolytic stability has previously been shown in emulsion-ABS impact modified PC blends, resulting from acidic residual surfactants and coagulants in the impact modifiers. To neutralize the residual emulsifiers and coagulants in emulsion-ABS, buffers were added to the blends during the compounding step. A comparison of PC molecular weight retention upon hydroaging between blends with added buffers in different cation forms revealed enhanced hydrostability in blends added with a cation specific buffer. The addition of buffer containing the specific cation presented here holds promise as an effective strategy for improving hydrostability in PC/emulsion-ABS blends during compounding.
Thermal and Rheological Behavior of Plasticized Polyacrylonitrile and Melt Spinning of Precursor Fibers
While there is tremendous interest in the melt spinning of polyacrylonitrile (PAN) with presence of plasticizers, the behavior of plasticized PAN melt and the spinning process have not been adequately investigated so far. In this paper the melting and rheological behavior was studied for PAN plasticized with water or water and a second plasticizer. A lab scale pressurized fiber spinning system was developed and used to generate melt-spun fibers as carbon fiber precursors. The morphological and mechanical properties of the fibers were evaluated and compared with commercial wet-spun fibers. The meltspun PAN fibers have surface and mechanical properties similar to those of commercial fibers.
Morphological and Rheological Properties of PBS/Silica Nanocomposite Manufactured Using a High-Speed Twin-Screw Compounder
The effects of silica chemistry and high-speed compounding on the morphology and rheology of poly(butylene succinate) (PBS)/fumed silica nanocomposites were investigated in this work. The filler content of the nanocomposites was determined by thermogravimetric analysis and matched estimated values well. Depending on the distribution and surface chemistry of fillers, distinct surface texture could be identified in the PBS/silica nanocomposites. Using high-speed mixing and compatibilizing surface functionalizations can result in enhanced polymer-particle interactions and influence the composite rheology dramatically. The relaxation hierarchy can be identified from the linear viscoelastic response of PBS compounded with mixture of modified and pure fumed silica particles.
Composition Dependence on the Mechanical Behavior of Hydrophobic Lignocellulose-Reinforced Poly (Trimethylene) Terephthalate Composites
Lignocellulosic fiber-reinforced thermoplastic composites offer many property and environmental benefits. The major issue to overcome is moisture absorption due to the hydrophilic nature of the lignocellulosic component. The aim of this work is to combine hydrophobic natural fibers (NF) and a thermoplastic to produce a novel wood polymer composite that offers moisture resistance, dimensional stability, and resistance to microbial attack. Hydrophobic NFs are combined with polytrimethylene terephthalate using a novel, injection molding method and the flexural, tensile, and impact resistance mechanical properties presented.
Property Development of Semi-Crystalline Polymers in Sintering Processes
In additive manufacturing processes such as Selective Laser Sintering (SLS) and Selective Mask Sintering (SMS), shrinkage and warpage effects tend to be some of the major sources of error that affect dimensional stability and part quality. Most of these inaccuracies are due to thermal processes that take place over time. The present work includes an experimental and analytical approach to study the relationship between crystallization and development of mechanical properties over time during the sintering process. These properties are necessary when predicting shrinkage and residual stress build up during the crystallization process.
Post-Consumer Recycle (PCR) Solution for PC/ABS Blends
To meet the continued commitment on environmental sustainability, SABICTM has developed and commercialized PCR PC/ABS blends portfolio, which provide more options for customer to choose Cycoloy product. PCR Cycoloy grades are all PC/ABS blends containing 30~35% recycled polycarbonate from post-consumer CD and/or water bottle. RCM6123 and RCM6134 are filled grades, while RCY6214, RCY6113, RCY6013 and RCY6713 are non-filled. These grades were developed for various applications with additional value on environmental sustainability. At the same time, in most applications they showed comparable properties to corresponding virgin grade.
Vapor-Foamed Injection Molding of Polycarbonate Using Sodium Chloride and Active Carbon as Nucleating Agents
This paper presents a new process for producing vapor-foamed polycarbonate (PC) parts using water vapor as the physical blowing agent and two kinds of nucleating agents, namely, sodium chloride (NaCl) particles and active carbon (AC) powder. The effects of these two nucleating agents on the surface roughness, mechanical properties, and microstructure of solid and foamed parts were characterized. The results were compared with microcellular injection molded parts using supercritical fluid (SCF) nitrogen as the physical blowing agent without a nucleating agent. The water vapor-foamed PC parts with NaCl as the nucleating agent had a smooth surface comparable to that of solid injection molded parts. Foamed PC parts with AC had desirable specific mechanical properties as well as an advantageous average weight reduction of 16.4 wt%. AC powder, serving as nucleating agents, water carrier, and reinforcing fillers, positively improved the microcellular structure and mechanical properties of vapor-foamed PC parts. Based on infrared spectrometry (IR) and gel permeation chromatography (GPC) results, the melt compounding processing to incorporate the nucleating agent and the vapor-foaming process caused minor thermal degradation and hydrolytic degradation, respectively. Without the nucleating agent, vapor-foamed PC parts exhibited much larger and fewer bubbles within the molded parts.
Enhancing Cell Nucleation for a Novel Microcellular Injection Molding Process Using Gas-Laden-Pellets
A novel and cost-effective method of microcellular injection molding using gas-laden pellets has been developed. In this study, several methods, as well as their combinations to enhance the gas-laden pellets’ foamability, have been attempted including (a) enhancing homogeneous nucleation by blending N2- and CO2-laden pellets to create an N2/CO2 synergetic effect, (b) enhancing heterogeneous nucleation by incorporating talc as a nucleating agent, and (c) enhancing heterogeneous nucleation by compounding PP/HDPE immiscible blends. The results show that these methods effectively improved the cell nucleation rate and cell morphology. Moreover, it was found that these methods could also be superimposed on one another without conflict, thus leading to further improvements.
The Newly Developed Fluorine Type Epoxy Resin Having Excellent Adhesion and Low Dk/Df Characteristics
The mobile communication devices require high speed transmission of large volume data and reduction in size and weight. When signal is transtitted in high speed and frequency on PCB, signal integrity becomes a big problem. One of the most widely used methods to solve the problem is to apply materials having good adhesion and low Dk/Df characteristics. Although various materials are available for the purpose, they tend to be expensive and require special care during the fabrication process. Therefore, PCB makers have been looking for more affordable and easily handleable materials that can be implemented outstanding adhesion and low Dk/Df. To meet these demands, we have developed epoxy resins containing fluorine. This fluorine type epoxy resins are obtained by applying fluorine based materials having high adhesion and low Dk/Df properties. So after epoxidation, the introduction of fluorine into the chain of the epoxy resin resulted in improving the adhesion and dielectric properties.
Experimental Studies on Extrusion Process of Polypropylene Double-Lumen Micro Tube in Medical Applications
A polymer micro tube with multi-lumen is difficult to fabricate. In this study, an extrusion die of double-lumen micro tube was designed and fabricated. Different processing conditions affecting the ovality and the thickness uniformity were investigated. The results indicated that the contour ovality was significantly influenced by gas flow rate, screw speed, die temperature and vacuum degree of water tank. The thickness uniformity of micro tube was determined by the die design method and the manufacturing precision. The desired double-lumen tube with an outer diameter of 1.6 mm was obtained by the optimization of processing conditions.
Improving Foaming Properties of Low Melt-Strength Polyethylene via Controlled Crosslinking
Crosslinking is widely used to improve foaming properties for low melt-strength polyethylene. However, premature crosslinking will not only suppress the growth of microcells, but also severely affect the melt processibility. It is thus very difficult to obtain highly crosslinked foamed polyethylene products. This paper describe a novel foaming process through manipulating the viscoelasticity of the polymer melt in response to the decomposition of the chemical blowing agent (BA). Practical guidelines to achieve low density polyethylene foam products with high crosslinking degree are provided.
The Gas Counter Pressure Effect on the Carbon Fiber Orientation Distribution Study in Injection Molding
With a large demand of polymer composites in all manner of industries, product development has focused on good mechanical strength and functionality with fiber composites. The key of development lies on the control of fiber orientation and distribution. This study applies Gas Counter Pressure(GCP) in injection molding to investigate the fiber orientation on different layers of thickness(core, shear and skin) and numerous part locations(far, center, and near as referred to the entrance of gate). As a result, the counter pressure is directly related to fiber orientation. Under the molding parameters of 80°C mold temperature, 230°C melted temperature, and 10cm3/s injection speed, the higher counter pressure, the greater anisotropic fiber distribution. Since GCP forced the core to skin, the most anisotropic distribution is on core layer, then the orientation and skin layer in sequence. For the fiber orientation in part, it has better anisotropic fiber distribution around the area farther from the gate, which is because the fiber orientation perpendicular to the cross section of product is affected dramatically by the pressure. In addition, a simulation tool, Moldex3D, is utilized to verify experiment results. The simulation shows high agreement with experiment on the trend of various locations. It can be proved that injection molding with GCP can increase disturbing level effectively.
Preliminary Evaluation on the Influence of Gas Counter Pressure on the Process Flow Characteristics, Molecular Orientation and Qualities of Injection Molded Parts
In this study, various polymer materials (PP, PS), product thicknesses (0.6 mm, 1.2 mm), and flow rates (5 cm3/s, 10 cm3/s, 15 cm3/s, 20 cm3/s, 30 cm3/s) were discovered by utilizing a developed molding technology called Gas Counter Pressure (GCP). Both conventional and GCP molding were performed to compare the associated influences on part shrinkage, mechanical properties, crystallinity, and shape of Melt-Front Area (MFA). The results show not only simulatively, but also experimentally that the shrinkage is reduced under GCP condition. What’s more, the degree of elastic module is enhanced, and the average ratios of tensile strength for both 0.6-mm-thick PP and 1.2-mm-thick PP increase 0.1937% and 4.6014% respectively due to the holding effect applied under GCP condition while the average ratio of tensile strength for PS decreases 1.8994% owing to the restricted molecular orientation. Furthermore, average ratio of crystallinity decreases either 1.987% (0.6 mm) or 2.560% (1.2 mm). In addition, Scanning Electron Microscope (SEM) diagram illustrates that the profile of melt-front for GCP molding is obviously flattened.
Polyvinyl Alcohol Foaming with CO2 and Water as Co-Blowing Agents
This paper investigated the continuous extrusion foaming of a biodegradable polymer, polyvinyl alcohol (PVOH), using supercritical carbon dioxide (scCO2) as the blowing agent. As-received PVOH pellets were first compounded with water to decrease the melting point of PVOH. In addition, the water can help to reduce the potential for thermal degradation during the extrusion foaming process. Furthermore, water also served as a co-blowing agent together with scCO2 to achieve high expansion and high cell density biodegradable polymer foams. The effect of scCO2 content and die temperature variations on the expansion ratio and cellular morphology of the PVOH foam were examined systematically.
Tack Property and Cure Behavior of High Performance Carbon/Epoxy Prepreg
The cure kinetics and tack properties of carbon/epoxy prepreg and epoxy resin were investigated. The effects of cure temperature on the cure kinetics were investigated with dynamic DSC and isothermal DSC analysis. The cure temperature range was 180-240°C and heating rate was 2-40°C/min, respectively. Activation energies were determined for resins from dynamic DSC tests by using Ozawa and Kissinger models. Consequently, the activation energy for epoxy resin increased as a function of conversion. Tack property of carbon/epoxy prepreg was measured by using probe tack test. The influence of contact time, contact force, debonding rate and plate temperature on the carbon/epoxy prepreg tack was investigated.
|
This item is only available to members
Click here to log in
If you are not currently a member,
you can click here to fill out a member
application.
We're sorry, but your current web site security status does not grant you access to the resource you are attempting to view.
.jpg)
.jpg)
.jpg)
.jpg)
