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.
|= Members Only|
The Effect of Thermal Relaxations on the Crack Initiation Resistance of Rotomolded Linear Low Density Polyethylenes
The objective of this paper is to provide a better understanding of how test temperature and test frequency affect the crack initiation and propagation energies of rotomoulded materials. Trials were carried out on a range of rotomolded linear low density polyethylenes. Instrumented impact tests and dynamic mechanical thermal analysis (DMTA) were carried out on each material at a wide range of temperatures and frequencies. It was found that there is a linear relationship between the crack initiation energy of the samples and the tan ? values at all test conditions. By using this relationship it is possible to predict the crack initiation energy of a polymer part over a wide range of conditions by carrying out a small number of tests.
Rotational Molding Process Control
Process control for the rotational molding industry has been continually evolving in recent years. Initially, impact strength, and bubble content in the wall of the molded parts, were used to gauge the level of cure and also to control the process. More recently, the development of the Rotolog process control device has provided a more scientific means to ensuring good process control.This paper highlights some recent work that expands upon the methods previously mentioned, applying new methodology to measure and control the process. The effects of various processing conditions are considered, in particular, with respect to the cooling cycle, and how they relate to process variation. The results outlined provide new processing knowledge that can be used to further develop the control of the rotational molding process.
Performance of a Rotationally Molded Thermotropic Liquid Crystalline Polymer
Thermotropic liquid crystalline polymers (TLCPs) have a number of potentially useful physical properties for rotational molding: excellent chemical resistance, good barrier properties, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance. However, it is possible that the nature of the molding process is such that full advantage of these properties cannot be obtained. To determine how well TLCPs perform when rotationally molded a commercially available TLCP, Vectra B 950, was studied under static conditions as well as with a single axis rotational molding unit capable of measuring the internal air temperature. The processing temperature was determined by measuring shear viscosity at several temperatures. The tensile strength and modulus of both statically molded and rotationally molded samples were measured. Samples were evaluated for complete densification by inspecting the fractured surface.
Failure Prediction in Polymer Composite, Sheet Metal Forming Dies
This paper presents a systematic approach to predict damage in a sheet metal forming die fabricated from a composite (aluminum trihydrate-filled polyurethane). The dominant die failure mode is determined based on the mechanics governing the forming process, and the fatigue life is predicted. Both numerical simulations and experiments are performed to verify the method.
Annealing Effects on the Yield and Fracture of Bisphenol-A and 4,4'-Dihydroxydiphenyl Copolycarbonates
The annealing effects on yield and fracture behavior of two different polycarbonates, one bisphenol-A-based (BPA) and one copolycarbonate of BPA and 4,4’- dihydroxydiphenyl (DOD), have been investigated. Annealing increases the yield stress, decreases the tan ? intensity at 80°C, and decreases the resistance to crack growth in both materials. The DOD material shows a slightly increased resistance to annealing compared to the conventional polycarbonate based on relative post-yield stress drops and tearing moduli of the materials.
Assessment of Plastic Failure of Polymers Due to Surface Scratches
This paper is concerned with the evaluation of plastic damage of polymeric substrate under surface scratch deformation. Employing a commercial finite element (FE) package ABAQUS®, FE analysis was performed to study the permanent damage imposed by a spherical indenter as it traverses across the surface of a polypropylene (PP) substrate. As compared to the experimental data, the numerical results make reasonably accurate prediction on the onset of scratch damage. Also, the furnished solutions aid in elucidating the fracture phenomenon encountered and the possible damage initiation during scratch.
Investigating Environmental Stress Cracking with In-Situ Contact Angle Measurements
This paper probes a hypothesis for initiation of environmental stress cracking (ESCR) based on a thermodynamic criterion for localized swelling induced by stress on the polymer. The system chosen for study is polycarbonate with oleic acid. An experimental technique involving contact angle measurements of a sessile drop as a function of stress is presented. A novel technique for contact angle measurements using refraction is also introduced.
Metallocene Based Polyolefins for Rotational Molding Applications
Polyolefins based on metallocene catalyst technology appeared in the early 90’. These polyolefins were first used in application like blown film for metallocene polyethylenes, cast film and fibers for metallocene polypropylenes.This paper will highlight the interest of metallocene based polyolefins, polyethylene and polypropylene resins, for rotational molding applications. Polymer characteristics, processing behavior and rotomolded item properties will be compared to conventional Ziegler-Natta based resins. These new polyolefins show a real potential in terms of cylce time, dimensional properties, impact and optical properties improvements.
Effects of Particle Morphology on the Processability of Ethylene Copolymers for Rotational Molding Applications
Polymer sintering plays a major role in processes such as rotational molding, governing the heating cycle and the properties of the final parts. This work aims at determining the impact of changes in the material formulation and processing history on the sintering behavior. These changes are known to introduce variations in the material morphology and thus affect the material processability and properties of the end-product. Variations in the thermal treatment were found to have an effect on the particle morphology but a limited impact on the sintering process. It was also found that the addition of a nucleating agent can be detrimental to the sintering process. The impact of these changes, however, seems to be related to the viscosity of the material as well as the molecular structure.
Plasma Modified Polyolefin Powders for Rotational Molding
Reliable sources estimate that about 75% of molded polyolefin technical parts need surface refinement. Those surfaces have to be lacquered, dyed, glued, coated, or printed. Also, polyolefin resins offering better adhesion to PU foams are requested.The ARPLAS process offers improvements in quality, economics, and flexibility. This plasma process modifies the chemical structure of the polyolefin powder surface, that non-polar, hydrophobic materials become polar, hydrophilic materials, which can be lacquered, coated, and foamed without any other additives.The modification of the powder is achieved by implantation of functional groups into the polyolefin molecules. Characteristics of the material, i.e. impact strength, ESCR, and other major specifications remain unchanged as well as processing compared to non-modified PE.The new ARPLAS technology offers molders new application possibilities, opens up new market sectors, and reduces adhesion problems.If serious sticking/adhesive problems are to be solved, the use of ARPLAS-treated powders make sense. This is also true if an acceptable paint coating is to be applied or a strong bond is to be made with PU foam.
Electrical Conductivity of Composite Nanofibers of Polypropylene/Carbon Nanofiber and Nanotubes
The DC electrical conductivity of composite microfibers consisting of carbon nanofiber and carbon nanotube reinforced polypropylene is examined. Carbon nanofibers with an average diameter of 100 nm can serve as ideal precursor system to carbon nanotubes for the development of polymeric fibers with superior electrical, mechanical and thermal properties. Electrical conductivity of the microfibers was measured over a range in the nanofiber weight fraction of 0.5-10 percent and carbon nanotube fraction of 0.1 to 0.5 percent. The results provide a comparison between the property enhancement levels achieved in the microfiber by the addition of similar weight fractions of carbon nanofiber and carbon nanotube reinforcements in the dilute range.
Low Shear In-Mould Decoration-Processes for the Manufacture of Three-Dimensional Molded Interconnect Devices (3D-MID)
The aim of Molded Interconnect Devices is to integrate in an injection moulded part with structured plated surfaces electrical and mechanical functions. One of the promising manufacturing methods of 3D-MIDs is the In- Mould Decoration-Process, which uses a plastic-film with a circuit-pattern plated on its surface. Problems which occur sometimes in the conventional In-Mould-Decoration- Process are the damage of the circuit structure or the plastic- film due to high shear stress and pressure during injection. Another problem could be the warpage of the device. Different process-variants which are capable to overcome this difficulty like thermoplastic foam moulding and injection compression moulding were evaluated. Of major concern in the investigation was beside the warpage the adhesion between the plastic-film and the substrate depending on different process-variants of In-Mould Decoration.
Crystallization and Chemi-Crystallization of Recycled Photodegraded Polymers
Injection molded bars have been made from blends containing recycled photodegraded polymers, then subjected to further ultraviolet (UV) exposure. Crystallinity measurements have been made at different depths from the exposed surface using X-ray diffraction and differential scanning calorimetry. Complementary information in the form of molecular mass distributions has been obtained using gel permeation chromatography, and the crystallinity results are interpreted in terms of molecular scission and photo-initiated molecular defects.
The Design, Construction and Operation of Equipment to Investigate the Response of Open, Coloured, uPVC Profiles to Solar Gain
Laminated and dark coloured uPVC profiles, when exposed to sunlight during normal use, may occasionally suffer deformation. To gain a greater understanding of this phenomenon, a number of test rigs were developed to recreate the temperature increase, through the use of infrared heating elements, to simulate varying intensities of solar radiation.
Considerations for Relating Artificial Laboratory and Natural Outdoor Weathering Durability Testing
This paper reviews considerations for linking laboratory and outdoor reference exposure weathering durability data. Laboratory considerations include designing experiments and developing predictive functions using xenon arc devices. Reference exposure considerations include monitoring meteorological and irradiance exposure variables in Florida and Arizona. Exposure data is compared for polycarbonate.
Control of Directional Electrical Conductivities in Carbon Black-Thermoplastic Exrtrusions Produced by Chaotic Advection
Whereas prior related work involved batch devices, an industrially relevant continuous flow chaotic mixing process has been used in this study to form structured distributions of carbon black in extruded films. Methods were also applicable to other extrusion profiles. Carbon black masterbatch was formed into numerous filamentary striations that yielded conducting states at low overall compositions. A range of electrical properties were selectable via process parameter specification. Differences in directional conductivities along the width and length of the film were controllably obtained. The progressive formation of structure was related to electrical properties and process conditions.
Nondestructive Characterization of Orientation in Thick Cast and Drawn Polyaniline Films
Polyaniline (PANI) films 20 to 50 microns thick cast from N, N’-dimethylpropylene urea (DMPU) solution and stretched to different draw ratios were examined. The thickness of these visibly opaque PANI films posed severe limitations on available structural characterization tools. NIR wave guide coupling, X-ray diffraction and FTIR infrared dichroism methods were used. Two new infrared transition moment angles for weakly absorbing bands were determined for the PANI molecule. This allowed the Hermans’ orientation function for the thick PANI films to be determined nondestructively.
Improving Gel Compatibility of Polyolefinic Polymers for Loose Buffer Tubes in Fiber Optic Cables
Loose buffer tube designs in fiber optic cables (FOC) generally include hydrocarbon oil based gels to fill the tubes for mechanical and moisture protection. Conventional olefinic polymers typically show reduced performance in compatibility testing due to a high level of hydrocarbon oil permeability. In particular, impact-modified polypropylene (IMPP) requires specially formulated and, therefore, more expensive gels to retain modulus and tensile properties after oil exposure. Described herein is the gel compatibility performance of a developmental product made with INSPIRE* Performance Polymers that provide a substantially improved balance of impact toughness, high modulus and gel compatibility for the optic buffer tube application versus the conventional polyolefin materials currently used. Also outlined are preliminary results of ongoing material studies targeting further improvement in gel compatibility performance.
Investigation of Packaging Properties as a Function of Filler Microstructure
Fillers are used in the molding compounds to minimize the stress of electronic packaging by reducing the coefficient of thermal expansion (CTE) mismatch between the silicon die and the molding compounds.This study concentrates on the effect of filler particle spatial distribution. Quantitative measures of the particle distribution were experimental determined, including area fraction, size and interparticle distance (IPD). A 2×3×3 ANOVA test was also conducted to assess the statistical significance of these variations of measures. The difference of filler volume fraction at different positions within one chip can be as big as 10%, and cause a CTE difference of about 4 ppm/°C.
Conductive Polymer Blends for Injection-Molded Bipolar Plates
This work aims at developing lightweight low-cost bipolar plates for use in proton exchange membranes (PEM) fuel cells. New material formulations using polypropylene (PP) and polyphenylene sulfide (PPS) as matrices and carbon black, graphite, and carbon fibers as conductive additives were developed. These formulations have properties suitable for bipolar plate manufacturing, such as good chemical resistance, sufficient fluidity, and high electrical and thermal conductivity. Two prototype plates of different design were successfully fabricated by over-molding aluminum plates or simply by injecting the high conductive materials into the final shape.
We're sorry, but your current web site security status does not grant you access to the resource you are attempting to view.
Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
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
Note: if there are more than three authors you may use the first author's name and et al. EG Brown, H. L. et al.
If you need help with citations, visit www.citationmachine.net