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.
A technology has been developed to produce biaxially oriented films of blends of polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) using double bubble tubular film extrusion. The mechanical instabilities and the mechanisms associated with their sources of occurrence are described. The films have been structurally characterized by wide angle X-ray diffraction and optical techniques. The structure of the film is related to processing conditions.
Fibers have been melt spun from polypropylene and its blends with ethylene propylene rubber, as well as polypropylene based thermoplastic elastomers under various conditions. The spinline stresses as well as kinematics have been measured. The fibers have been structurally characterized using wide angle x-ray diffraction and birefringence and the results interpreted.
A model for flow start-up of a Newtonian liquid in an initially empty modular co-rotating twin screw extruder is developed. The changes of length of fill in front of the die and kneading disc block elements and output flow rate with time were predicted for various modular screw configurations. Experiments were also carried out on a laboratory modular machine with windows to verify the predictions. Generally, good agreement with the flow analysis was found.
The breakage of glass fibers was measured for several different types of continuous mixers including (i) Buss Kneader (ii) modular intermeshing co-rotating twin screw extruder (iii) modular intermeshing counter-rotating twin screw extruder. Comparisons are made using different screw configurations, loadings, different feeding ports and mixing elements. Downstream feeding of glass fibers and milder screw configuration favor less breakage of glass fibers.
A newly developed instrument, the Echometer measures the thickness of a barrier layer in multilayer polyethylene fuel tanks. Measurement by conventional pulse-echo ultrasound fails for thin barriers due to the large and highly frequency-dependent attenuation in polyethylene. The present instrument instead uses tone-burst excitation. Echo arrival time determines barrier depth, and frequency of minimum amplitude determines barrier thickness. Similar techniques may be applied to other layered plastic structures.
Techniques for the measurement of orientation of biaxially oriented films, sheets, and shapes using birefringence measurements based on oblique incidence of a polarized multiwavelength beam and FTIR spectroscopy in both transmission and reflection modes are presented. It is shown that sufficiently precise values can be obtained for biaxial birefringences and orientation functions, and that these techniques can be used for monitoring orientation processes as well as to control the quality of oriented articles.
A new HALS technology has been developed which provides for improved light stabilization of pigmented PC-ABS blends. Significant improvements in color stability and impact strength retention have been observed for PC-ABS systems subjected to accelerated weathering xenon arc test conditions. The new HALS technology is non-interacting with the PC-styrenic blend during melt phase extrusion compounding, as observed by capillary rheometry measurements of the stabilized polymers.
Non linear rheology of a mixture of two immiscible viscoelastic fluids undergoing high deformation flow was considered. Using Grmela's approach of compatibility of dynamics with thermodynamics, we derived a set of highly non-linear governing equations that take into account particles breakup, coalescence and the time evolution of the complex interface between the two mixture components. The proposed model recovers previous models such as Doi-Otha, Grmela and Ait-Kadi and Lee and Park models.
In this paper, some case studies are presented to illustrate the effect of processing/assembly conditions and part design on product failure. Fractography was intensely used in these investigations. Nevertheless, mechanical analysis was occasionally used. The first case illustrates the role of assembly conditions in product failure. The second case shows the effect of part design. The third case describes the combined contribution of processing/assembly conditions and part design in product failure.
Achieving parts with maximum dimensional stability coupled with minimum cycle times, is a goal of most molders. Previous studies have shown that a majority of heat contained in the molded part is removed through the core of a mold. Application of high strength, high thermal conductivity copper alloys to core, cavity, and gate areas, has led to some revelations. These data shed new light on the effect of change in temperature vs. change in thermal conductivity.
The stabilization effect of alkyltin 2-ethylhexyl mercaptopropionates was studied by the measurement of color change on heating a PVC formulation.
This paper describes the application of foundry sand moulding technology to the development of a rapid and low cost injection-moulding tooling system. An assessment of the sand / binder foundry moulding processes is presented which considers the requirements of the injection moulding process. Rapid Prototyping (RP) is used to provide a master pattern for transferring the geometry to the tool. Suitable formulations of sand, binder, hardener and curing conditions for tooling application are then discussed.
The deformation and fracture behaviour of polyamide-6/silicate nanocomposites are studied. With increasing clay content the modulus increases much more substantially than can be achieved with micron-sized clay particles, but the fracture toughness drops significantly. The micromechanisms of fracture are relatable to the microstructure of these materials. The matrix is capable of a surprising amount of shear plasticity. Rubber modification is effective in producing more crack tip damage which increases the toughness of these composites.
Polypropylene (PP) was functionalized with maleic anhydride (MAH) and diethyl maleate (DEM) in a twin-screw extruder. The functionalized PPs were mixed with a 80/20 wt./wt.% blends of polypropylene and ethylene-vinyl alcohol copolymer (EVOH) and the extruded films were stretched at the exit of the flat die. The effect of the functionalized PPs and stretching on PP/EVOH blend were investigated. Morphological analysis along with mechanical and thermomechanical analysis showed that PP-g-DEM is a good candidate for tailoring materials with enhanced barrier properties.
This paper will review the use of melt-processible rubber (MPR) in overmolding and co-extrusion with various rigid plastic substrates. Looking to improve product quality and develop new applications, plastics engineers are turning to MPR technology to cost-effectively add the high performance properties and warm, soft feel of rubber to their products. MPR exhibits superior resistance to weather, oils, chemicals, gasoline, and UV light, and is processed on conventional plastics equipment, which provides potential cost savings.
The effect of the core/skin ratio on the overall flow behaviour in the co-injection molding process was studied. A 7.6x16.4x0.7 cm3 rectangular plaque was moulded using a 150-ton Engel co-injection machine. ABS was used both for the skin and core material and PC were used only as the skin material. For visualization purposes, a black pigment was added to the core material. The results are discussed in terms of the relative viscosity, injection speed, melt and mould temperatures.
Ultrasonic pulse-echo techniques were used to monitor the entire injection molding process including the flow front advancement, the end of filling, the packing phase, the solidification and the detachment of the part from the mold. Compared to conventional pressure and temperature sensors, ultrasonic sensors are non-intrusive, have very fast response and can provide unique capabilities such as monitoring of filling and solidification, and detection of part/mold detachment from both sides of the cavity.
Roller pull-off experiments have been performed to investigate the rod strength with and without blowing agent. Low density polyethylene was melted to mix with physical blowing agent, or to liberate inert gas by decomposing chemical agent to form a homogeneous melt in the extruder. The extrudate exit a capillary die and went through a driven nip roll for force measurement at a given speed. Extensional viscosity was calculated from the pulling force and roller speed. It appears that plasticization and foaming are important factors in the stretched strength analysis.
Foam extrusion experiments were performed to study the effects of surrounding temperature variation on cell structure. Linear low density polyethylene was used with endothermic chemical blowing agent on a single screw extruder to exit from a capillary die into environments with different temperatures. Cell density, foam density, and cell morphology were investigated. The amount of chemical blowing agent and the surrounding conditions have to be viewed together to correlate with the cell density. Foam density appears to be related to gas escape from the surface during foaming.
The effect of lubricants, impact modifier, and process aid on the processing and physical properties of a rigid PVC compound have been modeled using a Central Composite designed experiment. Capillary rheology was used to evaluate the flow properties of the various formulations in the study. By modeling the rheological properties it is possible to simultaneously optimize flow, extruder conditions, and final part properties.
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Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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