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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Acrylic Impact Modifiers for PVC: Core-shell modifier chemistry and performance
Part 2 of the All Things PVC Workshop series. The speaker will review the basics of core-shell chemistry focusing on acrylic technology and its advantages for mechanical property improvement and weatherability in PVC formulating. Core principles of mechanical property improvement via stress concentrators for PVC matrices and formulations will be presented. In addition to rheology and mechanical property enhancement via acrylic chemistry, the presentation will also provide perspective on choosing the best impact modifier based on specific formulation needs or application types where standards vary based on the final needs of the vinyl building product, for example. The talk will follow-up on the principles covered in the introduction to PVC Gelation and Formulation.
Comparison of Additive and Conventional Tooling on Injection Molded Part Properties
Additive tooling can make injection molding viable for low volume production, reducing tooling cost and lead-time. This studycomparesthe final properties of injection-molded samples manufactured with a steel mold and two sets of 3D printed polymerinserts using material jetting (Digital ABSfrom Stratasys) and stereolithography(Toughfrom Formlabs). Results show thatthe Digital ABS insertsfailed after100 cycles, while the Tough insertsfailed after15 cycles. Parts producedwith steelmold and Tough and Digital ABS inserts exhibited a shrinkage of approximately3%, 6% and 9% respectively. The shrinkage and ultimate tensile strength was directly proportional to the degree of crystallinity measured using differential scanning calorimetry(DSC).
Extrusion Technologies for Low Temperature Compounding
For many applications the ability to continuously compound at low temperatures can be extremely beneficial. However, many challenges prevent traditional setups from being functional, particularly for applications requiring a high degree of mixing with extreme cooling or simultaneous temperature control. This paper addresses and experimentally validates four different technologies for compounding materials at low temperatures.
Finite Element Modeling on Barrel Mar Behavior of Amorphous Polymers
Mar damage on polymer surfaces has become a significant concern over a wide range of engineering applications. To gain insight into the strategies for improving mar damage resistance of polymers, it is necessary to learn about why and how mar damage is formed and how it is related to constitutive parameters such as Young’s modulus and yield stress, etc. In this study, three model amorphous polymers, i.e., PMMA, PC, and PS, were investigated using a well-established ASTM/ISO scratch testing in combination with the finite element method (FEM) parametric study to gain the fundamental structure-property relationships to furtherly understand mar damage. It is found that the total plastic energy dissipation during mar process correlates well with mar damage formation and can possibly be chosen as the criterion for mar damage formation. Three-dimensional FEM parametric study was further performed based on the verified mar damage criterion.
High Temperature Extensional Rheology Measurements to Understand Anti-Drip Properties
We have used a novel custom-built capillary break up rheometer to understand the polymer decomposition mechanisms and effects of FR salts on the polycarbonates. The objective of the present study is to optimize the concentration of FR salts on the polycarbonate resins to improve dripping properties under flame.
Minimizing Interfacial Orientation During Processing of Immiscible Blends
An interface between two immiscible polymer phases represents a material weakness due to reduced cohesive adhesion. For a co-continuous polymer blend, this interface can be viewed as an elastic membrane. From continuum mechanics, we show that the deformation of this interface during normal melt processing is largely affine, involving a slow relaxation process as compared with the relaxation process of the polymer chain. Accordingly we propose a processing strategy to minimize the development of the unwanted interfacial orientation and yet promote the development of molecular orientation so that a strong blend material can be fabricated. Some experimental results are provided and discussed.
Modern Rheological Techniques for Polymer Analysis: Capillary Rheometer, Screw Rheometer, and Melt Strength Tester
As a result of measuring the shear viscosity on a capillary rheometer and the screw rheometer, a viscosity function corresponding to 6 decades of shear rate of 0.1 to 10,000 [1 / s] was obtained. We have identified a new method for identifying crossover point with a single temperature measurement without performing complex ‘Time-Temperature-Superposition’. Also shear viscosity and melt strength functions were compared for eight LDPE grades. It was found that the melt strength showed a completely different behavior for similar melt index materials.
Screw Design for Ultra-High-Speed, Quad-Screw Extrusion
The effect of screw programming on the performance of an ultra-high-speed, 15 mm quad-screw extruder was investigated by processing low-density polyethylene with four screw programs, no active barrel cooling (to evaluate viscous dissipation), and screw speeds of 500-2000 rpm. Observations indicated that kneading blocks were needed for timely melting of polymer pellets. Large increases in barrel temperature occurred with mixing, rather than melting, kneading blocks. Kneading block design had limited effects on power consumption but significantly affected residence time, melt temperature, and drive torque. All designs produced significant reductions in the viscosity of the extrudate, which previously has improved mixing.
The Use of Multi-Wave Oscillation To Expedite Testing and Provide Key Rheological Information
Dynamic oscillatory testing is usually performed in a point-by-point fashion. For example, in a frequency sweep, the test material is subjected to oscillation at a particular frequency, equilibrium conditions are attained, and the experiment progresses to the next, discrete frequency. With isothermal tests or temperature ramps, testing is performed at 1 particular frequency, e.g., 1 Hz (6.28 rad/sec). The method discussed in this paper, Multi-wave oscillation, allows one to impose multiple frequencies simultaneously. This enables testing at multiple frequencies in less time than by the conventional method and is particularly useful in characterizing curing systems in isothermal time sweeps or temperature ramps. With some curing systems, especially where there is no Storage Modulus – Loss Modulus crossover point in the experimental timeframe, this enables one to determine an objective gel point, which is defined as the point where tan delta (= Loss Modulus/Storage Modulus) is independent of frequency.
Using a Micro Blown Film Line for Formulation Screening
A LabTech Ultra Micro Combi line (Microline), the smallest blown film line in the world, was used to conduct blown film formulation screening with a set of LLDPE/LDPE blends. A sample cutting pattern was developed to enable preparation of crease-free test specimens from the small layflat made on the Microline. Haze, dart A, tear (MD, TD) and tensile (MD, CD) were tested using the film made by the Microline. By carefully controlling the time to frost line on the Microline to match the time to frost line on the larger scale lines, it was found that dart A, tear (MD, TD) and tensile (MD) of the Microline film were correlated with those of the larger scale lines films. These film properties can be used for formulation screening with minimal consumption of materials (~150 g per film sample). Haze and tensile (CD) properties did not correlate with those of the larger scale lines films. Future work will investigate the cause of these deviations.
Viscoelastic Measurement and Injection Molding Simulation of Amorphous Polymer: From Liquid to Solid
The viscoelastic properties under wide temperature range (from viscous to glassy state) and various flow field are studied in this work for a commercial amorphous polymer. It is found that multi-mode EPTT model can describe all measured properties well including dynamic modulus, steady shear viscosity, first normal stress difference, and transient extensional viscosity. 3D flow VE simulation are conducted to validate the applicability of the fitted model and parameters by comparing with the injection pressure in filling and packing stages.
Viscosity Characterization and Transient Flow Simulation and Visualization of Ptfe Paste Extrusion
The shear viscosity of polytetrafluoroethylene (PTFE) paste and its flow behavior during paste extrusion were investigated. Frequency sweeps using a parallel plate rheometer were performed on compression molded samples of PTFE paste made from fine powder PTFE mixed with ethanol as a lubricant. Various grits of sandpaper were used to reduce slip of PTFE paste on the walls. A viscosity model was generated and COMSOL Multiphysics was used to create a time-dependent flow simulation of PTFE through a paste extruder. The simulated results were compared to experimental data of actual paste extrusion. Due to simplifications used in the model, the simulated extrusion pressure over time differed in both magnitude and slope when compared to the experimental data. The simulated velocity profile was compared to flow visualization experiments, showing good agreement in wider regions of the extruder. Despite these drawbacks, the experiments and simulated model provided useful information about the flow within the paste extruder.
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