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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Multi-walled carbon nanotubes (MWCNTs) were employed to improve the mechanical properties and electrical conductivity of syndiotactic polystyrene (sPS) aerogels by exploiting MWCNTs connectivity within the sPS network. The MWCNTs/sPS composite gels were prepared using thermo-reversible gelation process, whereby a hot solution of sPS and a dispersion of Kentera- modified MWNCTs were mixed and cooled at room temperature. Subsequently, MWCNTs/sPS aerogels were obtained by drying the gels under supercritical condition. The morphology of MWCNTs/sPS aerogels was investigated by scanning electron microscopy. The effect of MWCNTs on mechanical and electrical properties of the aerogels was studied. It was seen that the morphology of the aerogels remained almost unaltered with the introduction of MWCNTs. The compressive modulus of the composite aerogels increased compared to the native aerogels. The electrical conductivity enhanced significantly in the presence of a low volume percentage of MWCNTs. In addition, the electrical conductivity increased with compression.
Long fiber-reinforced thermoplastic (FRT) composites widespread use in automotive industrial fabrication is more of a requirement than short FRTs. Mechanical properties of FRT products are dominated upon fiber orientation within the part. Recently, we proposed a new mathematic orientation model for two considerations of the interaction and diffusion between the fibers and the fluid [U.S. Patent Pending in USPTO with Application No. 13/168,211 (2011)], namely, iARD- RPR (Improved Anisotropic Rotary Diffusion Model combined with Retarding Principal Rate Model). Following the well- known Jeffery Hydrodynamic Model, this iARD-RPR Model can well determine the evolution of orientation, suitably for long FRTs. In this study, we employed these models to simulate numerically that the long FRT fluid with polypropylene matrix flows through a center gated disk. As a result, predictions of shell-core-structure orientation distribution, through the thickness measured at three regions of the near-entry, the lubrication, and the near-end-of-filling along the radial direction of the disk, were in good agreement with experimental observations.
Blending immiscible polymers with the addition of Nano- additives is a very suitable method for tailoring the properties of materials. Carbon nanotubes (CNT’s) have shown in recent years to be versatile filler influencing several properties favorably. One property of concern is electrical conductivity of multi-walled CNT’s (MWCNT’s) which can be transferred into insulating matrices by filler percolation. These materials will strongly influence modern electronics, energy delivery, and anywhere composite materials are used presently. Drop Shape Analysis using a variety of test liquids to gather mean contact angle measurements is combined with Owens-Wendt theory of surface energy determining values for each sample. Atomic Force microscopy permitted examination of localization properties of the MWCNT’s with and without reactive component directly impacting thermal conduction and ductility.
The continuous demand of high performance materials with key properties requires the optimization of polymerization and post-reactor treatment processes. A multiscale characterization approach including techniques such as rheology, fractionation and NMR has proven to be essential to understand the links between polymerization conditions, molecular structural properties and end performance. Rheology is a preferred candidate for analytical characterization, since its use provides combined knowledge on molecular characteristics and processability. A key parameter for the performance of materials during processing is the so-called LCB. Rheology, in particular methods exploring the longest relaxation mechanisms, is known to provide a significant insight into the type and amount of longer chains incorporated during polymerization. Most of the existing rheological parameters used by Industry and Academia, to correlate molecular structure and processability, are based on techniques that are often time consuming and which, for most of the cases, are only applicable to a given class of materials. The increasing need to reduce “time to market” requires the development of more sophisticated and efficient characterization tools. The combination of different non-linear viscoelastic methods presented within this work will provide further insight into the links between molecular structural properties and polymerization conditions. The use of the Large Amplitude Oscillatory Shear (LAOS) together with uniaxial extensional flow measurements can bring new understanding on the nature of the non-linear viscoelastic response of LCB materials and its correlation with molecular characteristics.
In this paper, polyamidoamine (PAMAM) dendrimer was grafted onto MWCNTs, then initiated the controlled PS polymerization by ATRP method. The grafted MWCNTs were charactered in detail. Furthermore, PS/grafted- MWCNTs nanocomposites were prepared by solution blending and applied for ScCO2 foaming process. Compared with the neat PS foam, this nanocomposites foam exhibits higher cell density and smaller cell size, indicating that the grafted MWCNTs employ excellent heterogeneous nucleating effect.
In this paper, mesoporous silica (SiO2) was prepared by the template polyamidoamine (PAMAM) dendrimers, then modified with polylactide (PLA) by solution blending. PLA/SiO2 composites were charactered in detail. The results showed mesoporous silica could improve the thermal stability of PLA. Microcellular foams of the composites were prepared by supercritical fluid carbon dioxide foaming and exhibited a higher cell density and smaller cell size compared with the pure PLA foam, indicating that the well dispersed SiO2 can act as a well heterogeneous nucleation agent.
A multivariate sensor is designed with a piezoelectric ring and an infrared detector for measurement of melt pressure and temperature. The infrared detector includes a thermistor for measurement of the mold temperature. The polymer melt velocity is estimated by inspecting the transient melt temperature signal. The melt viscosity is then estimated from rheological models as the slope of the melt pressure relative to the melt velocity. Experiments confirm the validity of the approach.
Injection molding process induced residual stress and the corresponding thermo-mechanical properties are passed to a structural analysis mesh with a point-based mapping mechanism and direct hook-up method into a structural analysis package. This mapping method enables a huge amount of data passing more accurately between dissimilar mesh models for the same parts without interface files, and the results calculated with different material and stress models used in molding simulations can be directly available to a structural analysis. Stress analysis on a buckle set is provided for engineering design and material selection consideration with the capability of this mapping mechanism.
Special applications in plastic engineering require new different polymers. Therefore new polymers and additives are constantly being developed. A lot of these special polymers are not available in data bases and cannot be used in simulation software. But it is becoming more and more important to know as much as possible about polymers in order to avoid problems in product development and the manufacturing process. So the polymers have to be tested. This paper shows a possibility of measuring points of a p-v-T chart and transforming them into a mathematic model to do simulation with the specific material afterwards.
Due to the increasing use of polymer-metal multi- material structures in automotive and aerospace industries, joining technology has grown in importance. Available techniques to join polymer-metal multi-material structures have been identified to be either too expensive, limited in performance or not environmental friendly. This work intends to investigate the feasibility of the new Friction Spot Joining technology on aluminum AA6181-T4 / poly(phenylene sulfide) laminate structures. Friction spot lap joints with high mechanical strength (29 MPa) were produced and investigated in terms of process temperature (average peak temperatures from 224 to 316 °C) microstructure and compared with similar joints available in the literature. Joints obtained by friction spot presented mechanical performance similar or superior to other available techniques used for joining polymer-metal structures. This is an indicative of the potential of this new technology to produce high performance metal-polymer multi-material structures.
We investigated the nucleation effect of well exfoliated and dispersed GO sheets on polystyrene scCO2 foaming. To get PS/GO nanocomposites with well exfoliated GO sheets, a method based on latex concept were employed. The characterizations based on XRD and TEM demonstrated the exfoliation and well dispersion of GO sheets in polymer matrix. The scCO2 foaming were carried out and the results showed the well exfoliated GO sheets could be a high efficient nucleation agent.
Composites of Liquid crystalline epoxy resin(LCE) 3,3',5,5'-Tetramethylbiphenyl-4,4'-diyl bis(4-(oxiran-2-yl methoxy)benzoate) (M1) and glass fiber-reinforced nylon 66 (M2) were prepared by HAAKE 400P. Thermal properties of the composite were examined with TGA and measured with dynamic differential scanning calorimetry (DSC). It showed that the initial decomposition temperature of M2 increased by about 8°C by adding 7% wt M1, indicating the improvement of thermal stability. The melting point of composites decreased by 12°C compared to M2 as the content of M1 increased, showing the improvement of processing property
This paper investigates the differences in film properties between water-quench versus the traditional air-quench blown film process. The effect of process parameters such as water ring position, water temperature and annealing temperatures on the final film properties were studied. Barrier properties such as water-vapour transmission rate (WVTR) and oxygen transmission rate (OTR) were also compared. Results were correlated to the crystallinity differences observed between the samples using optical microscopy and WAXD.
The use of aluminum pigments to give a metallic or glitter effect in polymers has been popular for enhancing the value of plastic parts. Due to their large particle size, aluminum pigments can present some challenges. This paper provides information on the proper aluminum pigment and carrier selection. Recommended methods for blending and compounding will be discussed as proper dispersion can prevent some issues. The use of aluminum pigments in both liquid and solid polymer systems are presented. The focus of this paper is on Trouble Shooting of problems that occur when using aluminum pigments. This paper focuses on issues related to aluminum pigment processing and the finished part appearance. Plastic part fabrication processes can pose challenges, so recommendations are made to trouble shoot these problems and suggest solutions. Problems such as agglomeration, gassing, process orientation, color measurement, plate-out, flow and weld lines are addressed. Some issues such as flow and weld lines can occur with glass flakes and mica pigments as well as aluminum pigments.
Polycarbonate composites were prepared with as-received and surface functionalized carbon nanotubes (CNT). The anisotropic thermal conductivity was measured using two separate steady-state techniques for the in-plane and through-plane conductivity. The non-covalent surface treatment of the CNT was seen to improve the thermal conductivity of the composites. In addition, the consistency in the thermal conductivity enhancement due to surface treatment illustrates that the functionalization did not adversely affect the intrinsic thermal conductivity of the CNT.
It is important to modify internal structure of nanofibers in order to increase the mechanical properties. We aim to control the internal structure by changing spinning conditions in free surface electrospinning. In this study, effects of electrical conductivity of polymer solution and spinning distance on internal structure of PVA nanofibers were investigated. In order to change electrical conductivity, ionic salts were added into the solution for electrospinning. By increasing electrical conductivity and decreasing spinning distance, i.e. increasing electrostatic force to draw the polymer jet in electrospinning process, d-spacing of the (1 0 1) plane was found to decrease, i.e. packing of polymer chains was enhanced.
The measured electrical properties of polycarbonate (PC) and carbon nanotube (CNT) composites depend not only on the quality of dispersion achieved during compounding, but also the conditions used to injection mold and test the resistivity of a specimen. This study compares the information provided by various two-probe and four-probe test methods in the context of a simple injection molding optimization study. The test methods represent a variety of commonly cited test procedures based on published standards relevant to the conductive composites industry. Varying the injection speed and barrel temperature profile significantly impacted the measured bulk and localized electrical resistivity as measured using all test methods. Discrepancies between the test methods also varied with molding conditions, reflecting the complex features of injection molded CNT composites. Finally, this study addresses the resulting implications for evaluating the electrical performance of CNT composites.
Today's global economic environment frequently demands that our companies have more than one center for technical competence. However those same economic demands seldom allow for creating two or multiple separate and equal facilities. This therefore necessitates the development of different sites with basic overlap, but perhaps individual specialized capabilities and personnel. These sites and Specialists can then communicate and take a coordinated team approach to solving customer, application, or manufacturing challenges when needed. In this discussion we will attempt to elaborate on a particular instance that serves as a good example of team work in an environment such as described.
Diamond Micro Chiseling (DMC) has recently been developed as an ultraprecision machining process for the manufacture of structured optical molds. This process allows the generation of prismatic microstructures at a size between 50 ?m and 500 ?m, which cannot be manufactured by conventional processes like turning, milling or planning. Prismatic geometries are achieved by using specifically designed V-shaped diamond tools, a special tool kinematics and an ultraprecise 5-axis machine tool. Representative examples of these structures are corner-cube retroreflectors in the abovementioned size. In this paper main developments for the successful application of the DMC process will be demonstrated and examples for micro injection molded plastic micro optics will be given. Machine requirements, process and control developments as well as characterization of machined mold structures and replicated parts will be shown.
This study focused on estimating the moisture content inside wood particles when dry-blended with polyethylene powder to produce wood/polymer composites (WPC) for application in a rotomolding process. The effects of different parameters on the dynamics of drying were evaluated: initial moisture content of the wood particles, total thickness of the powder bed, temperature ramp and wood concentration in the mixture. As expected, higher initial humidity took longer to obtain equilibrium moisture and higher material thickness led to slower drying dynamics (time to equilibrium). On the other hand, increasing the temperature ramp decreased drying time. From the results obtained, it is clear that drying the wood particles before blending with the polymer is not necessary for rotomolding applications as most of the humidity will have left before the polymer starts melting and sticks to the mold walls.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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