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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NOUVEL NON-LINEAR RHEOLOGICAL PARAMETERS FOR POLYOLEFIN QUALITY CONTROL
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.
PREPARATION OF MWCNTS GRAFTED WITH POLYAMIDOAMINE DENDRIMER AND ITS EFFECT ON POLYSTYRENE SCCO2 FOAMING
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.
THE STUDY ON MESOPOROUS SILICA IN POLYLACTIDE SUPERCRITIAL CO2 FOAMING AND THERMAL PROPERTIE
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 IN-MOLD SENSOR DESIGN FOR MEASUREMENT OF MELT PRESSURE, TEMPERATURE, VELOCITY, AND VISCOSITY
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.
STRESS ANALYSIS FOR POLYMER COMPOSITES
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.
TRANSFORMATION OF MEASURED P-V-T DATA INTO MOLFDLOW SOFTWARE
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.
FRICTION SPOT JOINING OF ALUMINUM 6181-T4 AND CARBON FIBER REINFORCED POLY(PHENYLENE SULFIDE)
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.
THERMAL PROPERTIES OF LIQUID CRYSTALLINE EPOXY RESIN/ GLASS FIBER-REINFORCED NYLON 66
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
ALUMINUM PIGMENT TROUBLE SHOOTING FOR PLASTICS
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.
STUDY ON STRUCTURE FORMATION OF PVA NANOFIBERS SPUN BY FREE SURFACE ELECTROSPINNING
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.
COMPARISON OF COMMON ELECTRICAL TESTING METHODS FOR THE MEASUREMENT OF INJECTION MOLDED PC/CNT COMPOSITES
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.
MULTI-DISCIPLINE PROBLEM SOLVING IN A MULTI-FACETED GLOBAL TECHNICAL STRUCTURE
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.
ULTRAPRECISION MOLD MANUFACTURE FOR MICRO INJECTION MOLDED MICRO OPTICS
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.
ANALYSIS OF WOOD PARTICLE DRYING FOR ROTOMOLDING APPLICATION
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.
COMPARISON OF WATER-QUENCH VERSUS AIR-QUENCH BLOWN FILM PROCESSES – PART II: THERMOFORMABILITY
This paper investigates the film property differences between water-quench versus the traditional air-quench blown film samples. In Part I, it was found that the overall crystallinity of the water- quench film was much lower than that of the air-quench film. This resulted in higher WVTR and OTR values. The effect of process parameters such as water ring position, water temperature and annealing temperatures on the final film properties were found to be insignificant. In the second part of this study, thermoformability of the samples will be investigated in detail. Thermoforming trials were performed on both a batch former and an automated Multivac thermoformer.
PURE PERFORMANCE: THIN WALLED FLUOROPOLYMER CONTAINERS
High temperature fluoropolymers are a likely material of choice for critical components in demanding applications. Fabrication methods for producing three-dimensional, thin walled, hollow objects using these materials include assembling films and molded fitments utilizing welding operations. An alternate technique has been developed which eliminates the need for these assembly steps. This method rapidly produces containers suitable for environments between -165°F and 350°F while exhibiting superior mechanical, optical, gas barrier and chemical resistance properties.
EFFECT OF CLAY CONCENTRATION ON THE RHEOLOGICAL PROPERTIES OF TRIBLOCK COPOLYMERS NANOCOMPOSITES
Block copolymers are materials with many applications in the field of thermoplastic elastomers. Their properties can be further improved by the addition of nanoclays. However, the morphological and rheological properties of these hybrid materials are not very well known. In this work, the effects of clay concentration on the evolution of morphology of two block copolymers, (SEBS and SEBS-MA), presenting an aligned cylindrical morphology, when submitted to elongational flows was studied. The elongational test was performed using a Sentmanat elongational rheometer and the morphology of the clay-containing block copolymers was studied using small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM).
CONTINUING STUDIES OF DUCTILE-BRITTLE TRANSITION OF THE SECOND KIND
A transition from a continuous to discontinuous crack propagation and associated changes in crack growth equations has been reported in our previous work. Such transition was named Ductile-Brittle transition of the second kind (DBT2). Recent advances in continuing studies of DBT2 are reported in this paper. The highlights of an experimental program designed to understand the root causes of DBT2 are briefly described. It is found that the temperature, at which DBT2 takes place, shortly “transition temperature 2” (TT2) depends on stress field characterized by stress intensity factor (SIF). TT2 dependency on SIF is expressed in form of DBT2 diagram. It suggests that DBT2 may take place in a process of crack growth at a given temperature. This suggestion is confirmed by direct observations in the present program as well as by the fractographic analysis of HDPE pipe brittle fracture in temperature accelerated long-term sustained pressure test. The DBT2 diagram is a valuable tool for design of an accelerated testing for lifetime of PE structures in durable applications.
NATURAL FIBER REINFORCED THERMOPLASTICS (NFRTP) PROCESSED BY ROTOMOLDING
In this work, wood fibers/linear medium-density polyethylene (LMDPE) composites were produced by rotational molding. The effect of wood particle sizes (0-1700 microns) along with wood contents (0-20 wt.%) were examined. In particular, the simple dry-blending technique was used to introduce the wood particles inside the polymer matrix before feeding the mixture to the rotational mold. From the samples produced, a complete characterization was performed in terms of density, morphology, as well as tensile, flexural and impact properties. The results indicate that increasing wood content increases both the Young’s modulus and the flexural modulus, while decreasing ultimate strength, strain at break and impact strength. Depending on the wood particle size, an optimum wood concentration was obtained for the range of parameters studied, especially when a mixture of different wood sizes is used.
OVERCOMING TECHNOLOGICAL ISSUES ASSOCIATED WITH COLOR ADDITIVES IN POLYMERS VIA SOLID-STATE SHEAR PULVERIZATION
A continuous, industrially scalable process known as solid-state shear pulverization was used to disperse colorant materials in polypropylene, which was followed by melt-processing. This novel two-step technique was shown to overcome several issues often encountered with conventional melt-processing, which include the elimination of “swirl patterns” and color shifting. We also show through this two-step procedure that we can achieve a similar color to a part made only by melt-processing by using approximately 25% less colorant.
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