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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Predicting How the Cooling and Resulting Shrinkage of Plastics Affect the Shape and Straightness of Extruded Profiles
During the extrusion of complex plastic profiles, the parts often distort and bow during the cooling phase of the process. The traditional methods of dealing with this are to use heat lamps to re-warm certain sections to remove the bow or to apply jigs to distort the part in the opposite direction so that when it cools, it comes back into the proper shape. A method to look at the cooling requirements of a particular profile is proposed along with a method to calculate how the part should be cooled in order to avoid distortion and bow.
Pressure Dependent Viscosity of Polymer Melts
Pressure dependent viscosity and juncture loss were measured by means of a new capillary rheometer developed at pressure up to 100 MPa and over wide shear-rate range from 5.0E+02/s to 5.0E+05/s for four polymer melts (HDPE, GPPS, HIPS, and PC) through simultaneous measurement of pressure at the entrance and exit of the capillary during applying counter pressure to the exit by means of a needle valve located in the downstream. Pressure dependent viscosity and juncture loss play an important role to improve the accuracy of simulation with a CAE program. However, there are few data in high shear-rate range corresponding to actual molding. Pressure loss in the flow path increases unexpectedly with increase of hydraulic pressure applied. The most adequate equation for fitting viscosity seems to be the Cross-WLF equation. The magnitude of the pressure parameter D3 lies in the range of 10E-07 K/Pa for these polymers.
How to Organise a Modern Plastic Company to Have Success in a Turbulent Environment?
Today's conditions in business activities, only short-term planning possibilities, necessity for everyday adaptation to situations within the company, require new organisational forms, new ways of managing the companies and, in a way, new people. Since today's companies are the target of constant selection, comparable to the one in nature, and their environment is unpredictable, it is no wonder that knowledge acquired by natural sciences is being increasingly implemented in the field of organisation. Modern business conditions have forced the managers to search for similarities with those scientific fields that have just begun to develop, and that try to establish some kind of order in the haphazard phenomena. Recognising similarities between the world of nature and an enterprise have led to the creation of numerous new organisational concepts, which have found their application also in plastic companies.
Measuring Viscosity of Filled Polymer Systems
This paper investigates the use of a Helical Barrel Rheometer to measure the viscosity of filled polymer systems. A Helical Barrel Rheometer is an online rheometer developed at the Polymer Processing Institute. The HBR allows us to measure the viscosity of polymer systems under conditions close to that encountered in processing. The viscosity measurement does not require measuring either the torque or the flowrate. The rheometer does not require an entrance correction, avoids bridging of filler particles during measurement and also takes care of the orientation of fillers encountered in processing. This paper uses polypropylene/talc as a filled polymer system. Three different concentrations of three different grades of talc were used to measure the viscosity and a comparison with conventional capillary viscometer was made.
A Study of the Effect of Chlorinated Water on Engineering Thermoplastics at Elevated Temperatures
Hot water plumbing applications can often be a severe environment for both metals and plastics. Continual exposure to elevated temperature as well as the oxidative effects of disinfectants such as chlorine can reduce the lifetime of plumbing components. A study was recently conducted to determine the potential degradation effects of hot chlorinated water on several engineering thermoplastics. Weight loss, tensile strength and elongation properties, burst strength retention and microscopy were used to examine the material behavior as a function of exposure time. This data will provide a basis for determining which engineering thermoplastics will be suitable for long-term exposure in hot, potable water.
Morphology and Mechanical Behaviour of Polypropylene Hot Plate Welds
Polypropylene tensile bars were hot plate welded and analyzed by microscopy and mechanical tests. The welding process originated deep modifications in the microstructure and shape of the bars at the weld zone. It was observed that the weld morphology was affected not only by the welding parameters but also by the thermal history of the components. The occurrence of oriented textures, coarse spherulites, voids or sharp notches at the beads are determinant morphological factors on the weld quality. The performance of the welds is dependent on the type of testing method used. The tensile impact test showed to be potentially good for quality control, as the fracture behavior was affected by the overall morphology.
Clear and High Heat Resistant TPEs
There is a market need for soft (35 - 70 Shore A) clear TPEs with heat resistance high enough for repeated boilable applications. Flexible PVC meets most of the requirements, but it is out of the scope of this work. Styrenic Block Copolymer based compounds have been developed to fill this need. Important parameters, such as molecular weight of the base polymer, surface quality of the molded part and rheology of the material, have been correlated with clarity and heat resistance. Some of the myths about the clarity of SBC compounds will also be discussed.
The Impossible Part-On the Verge of Failure?
There have been several occasions in the past where part designs have been proposed which require non-traditional approaches to manufacturing. Even with run-of-the-mill designs it seems prudent to do computer flow simulations to verify that a part is manufacturable. The case history described below details how a product was deemed impossible"; the flow simulation verified that it was "impossible" and yet the project was pursued and has now passed the prototyping stage. This paper describes a project where some risk was taken and may provide the drive to explore new limits."
Studies on the Rotomolding of Liquid Crystalline Polymers
This paper is concerned with the rotomolding of thermotropic liquid crystalline polymers (TLCPs) for the purpose of generating tank liners with excellent barrier to oxygen. The major issues involved include whether the TLCPs can be ground to provide resins suitable for rotomolding (~40 mesh size powder) and their ability to fuse together to provide adequate strength and barrier properties. With the use of appropriate grinding techniques, the TLCPs were found to fuse well to provide strength and stiffness significantly greater than that of HDPE.
Designing a TPO Using ETP Modification Technology
Elastomeric Thermoplastic (ETP) is a patented alloying technology that utilizes ethylene copolymer resins to modify flexible thermoplastic polyolefin (TPO) systems. It is based on the reactive blending of a partially neutralized acid copolymer (ionomer), an epoxy functionalized ethylene copolymer, and a standard TPO. The reaction between the epoxy groups of the ethylene copolymer and the free acid groups of the ionomer results in a partially cross-linked system that forms an in-situ alloy with the TPO. This alloy imparts increased melt strength to the TPO, permitting significant increases in thermoforming performance and grain retention. By varying the amount and type of Surlyn® ionomer within the alloy, a desired mix of mechanical properties, forming performance, and hand can be obtained. As the automotive industry moves toward developing interior components based on thermoplastic polyolefins (TPOs), this ability to customize a TPO-based material for specific applications provides a key advantage for the design engineer. For example, instrument panel skins can now be produced with reduced weight, reduced fogging, and better resistance to heat and UV radiation relative to PVC/ABS, but yet possess the ability to undergo deep draws during thermoforming while maintaining grain definition. Alternatively, formulations have been developed specifically for molded-in-color injection-molded soft-touch surfaces, which require a different balance of melt behavior and physical properties. In this study, we report on the relationship between ionomer content and physical properties in ETP modified TPO systems. The effect of incorporating an ionomer containing a softening acrylate comonomer on the feel" of the modified TPO material as quantified by flexural modulus and durometer is also discussed."
Design of Experiment (DOE) Procedures to Evaluate Ultrasonic Weldability of Materials
Usage of Thermoplastic Olefin (TPO) is a common trend for automotive interior parts. TPO is a copolymer of Polypropylene (PP) and Polyethylene (PE) for rubber constituent and the TPO evaluated contains 20% of talc. Considering the facts that PP and PE are semi-crystalline thermoplastics with high molecular weight and that TPO contains rubber, talc, and reground material, weldability of the material has been always in question. Especially since the ultrasonic welding process deploys several tens of microns of vibration amplitude for welding, energy from ultrasonic vibration can be dissipated easily before effective heating of materials for welding. Therefore, evaluation of material weldability is an important requirement for material selection.
Effect of the Interaction Coefficient in the Prediction of the Fiber Orientation of Injection Molded Glass Fiber Reinforced Polycarbonate
The mechanical properties of injection molded parts in glass reinforced materials is sensitive to processing. A successful design requires a good estimate of performance before production. The product performance is strongly affected by the fiber orientation field. It is complex and varies tri-dimensionally in the moldings. Some commercial simulation programs already allow the prediction of the fiber orientation induced by the injection flow. However the simulations depend on the definition of the fiber interaction coefficient. C-Mold simulations were made to determine the best fit to experimental results varying the interaction coefficient between neighboring fibers in center gated circular flat discs.
New Technology for Dyeable Polypropylenes
Approximately three billion pounds of polypropylene is consumed annually in fiber applications. Despite this success, one of the drawbacks to using polypropylene fiber remains its inherent lack of dyeability. In this paper we describe how a polypropylene resin can be modified via a blending process to produce a material that is readily dyeable and colorfast. In order to make the polypropylene dyeable, a reaction product of a maleated polypropylene and a polyether amine is blended into the fiber grade resin. The polypropylene portion of the maleated polypropylene co-crystallizes with the base resin, thus locking in the polyether portion of the molecule. This polyether molecule, with its high polarity, then allows the dyes to be absorbed. In these experiments fibers were spun using this modified material, fabrics were knitted, and dye testing was carried out. The results reveal that this modified polypropylene dyes several times better than the unmodified control.
Critical Conditions for the Onset of Unstable Flows of Molten Polymers
A simple method to predict the critical shear stress and the critical shear rate for the onset of melt flow instabilities in capillary flow is presented. The method, earlier reported for polyisoprene, employed a bulk stable viscoelastic constitutive equation that contains a hardening parameter ?. The parameter ? is solely determined by the molecular characteristics of the polymer. Below we compare predictions of the critical shear stress with experimental data for some common polymers.
A Unique Benzoate Plasticizer for Reducing Viscosity and Fusion Temperature
Plastisol viscosity reduction and control is an important property specification in many vinyl plastisol formulations. A unique benzoate plasticizer is under development that functions as a viscosity reducer. It also is a high solvating plasticizer in standard plastisol systems. Data will be presented on the effect of the new benzoate plasticizer on phthalate and benzoate containing plastisols and vinyl sheet properties.
Using Branched Polypropylene as a Melt Strength Modifier-Improvement in Sheet Sag Resistance
Blends of conventional polypropylene (PP) and branched PP (bPP) enable PP to perform well in applications where extensional flow dominates, such as blow molding, thermoforming and foaming. Sag resistance tests shows a significant improvement in sag time of extruded sheet as the content of bPP increases, up to 30-wt.%. These blends (PP/bPP) show synergistic increases in melt tension while providing excellent processability by maintaining low viscosity.
The Establishment of a Processing Window for Thin Wall Injection Molding of Syndiotactic Polystyrene
This study examined the effects of injection molding conditions and critical design parameters on the filling, dimensional stability, and crystallization of syndiotactic polystyrene (sPS) parts. Part wall thickness was the primary factor affecting filling, shrinkage, and crystallization. While injection velocity was secondary influence during, mold temperature was the minor factor for crystallization and shrinkage. Melt temperature and gate dimensions had little or no effect on filling or part properties.
LCP Droplet Deformation in Fiber Spinning of Self-Reinforced Composites
The development of morphology during fiber spinning of blends of polyesters (PET and PBT) with LCP (PET/HBA) was studied. The quantitative predictions of the blend morphologies under isothermal and non-isothermal conditions were obtained using a droplet deformation criteria based on the reduced capillary number and the affine deformation theory. The temperature, radius, velocity, and strain rate profiles of 60/40 polyester/LCP fibers along the spin line were calculated using Kase and Matsuo's theory for fiber spinning under the steady-state condition. Simulation of breakup of LCP phase during fiber spinning of the blend based on the dimensionless breakup time indicated the absence of their breakup. The flow curves of the blends at various temperatures required to carry out simulation were obtained. Initial and final sizes of LCP phase were examined by SEM and image analysis. The calculated diameters of LCP fibrils in the fibers were found to be in agreement with the measured values.
On-Line Rheological Measurements
Rheometers are being used increasingly as sensors for process control. This is because of the sensitivity of rheological properties to polymer characteristics such as molecular weight. The process rheometers now being used are mostly of the on-line, pressure flow type, in which a gear pump feeds a capillary or slit, and the pressure drop is measured. For process control applications, the signal delay associated with the flow of melt from the main flow to the capillary or slit slows the system response, and this problem has been addressed by the use of a larger sampling line together with a bypass around the rheometer. Other recent advances are aimed at providing a more extensive characterization of the melt.
A New Generation of High-Performance PVC Alloys
Newly developed alloys of flexible poly(vinyl chloride) [PVC] and polyolefin elastomers have been shown to exhibit improved physical properties compared to conventional flexible PVC control compounds. In particular the new alloys display enhanced electrical properties, better high temperature stability, greater low temperature flexibility, and superior gas barrier properties. In addition, the following study demonstrated that PVC/polyolefin rubber alloys have potential utility in many applications where conventional flexible vinyl compounds do not meet certain end-use performance requirements.
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