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.
Mechanical and thermal properties of epoxy have been modified through blending of diglycidylether of bisphenol A (0.1 mol) with polydimethylsiloxane (PDMS) at concentration ranging 1.0 to 3.0 phr of resin at 1400 psi and 90±10C for 1hr in supercritical carbon dioxide (scCO2), followed by curing with triethylenetetramine (10 phr) at 40±10C.The formation of synthesized epoxy silicone blends (ESBs) has been ascertained through ultraviolet –visible (Uv-vis), Fourier transformed infrared (FT-IR), X-ray diffraction (XRD) spectra and microscopy. With PDMS concentration, the compressive, tensile strength, Rockwell hardness (R scale), fringe values and crystallinity of ESBs were decreased with simultaneous increase in their impact strength, resistance against wear and thermal stability. Key words: Supercritical carbon dioxide, Polymer blends, Spectra, Morphology, Mechanical and thermal properties.
Thin wall injection moulding is a difficult process. High viscosity polymeric material is injected into a mould by high speed and high pressure. A special instrumented injection mould was designed for the investigation of the cavity filling of injection mould. Rheological measurement can be carried out with different wall thickness slit die inserts. The pressure can be measured during the filling, the packing and the cooling stages as well. The pressure drop during the filling can be used for determination the flow properties of the material. The measured cavity pressure of the injection cycle is proper for the validation if thin wall injection moulding simulation. The filling of the dies was simulated by Moldex3D software.
Chemical oxidative copolymerization of pyrrole with thiophene was conducted using ferric chloride initiator at 90 °C, 1200 psi over 24 hours in supercritical carbon dioxide (scCO2). Polymerizations were conducted with different concentration ratios of pyrrole to thiophene 1:0, 0:1, 1:1 and 1:2 in a 100 mL high-pressure batch reactor. Polymerization yield which was up to 56.7 % in homopolymerizations was found to decrease in copolymerizations at molar ratio of pyrrole to thiophene 1:1 .The polymers were characterized by ultraviolet visible (Uv-vis), Fourier transformed infrared (FT-IR) spectra, elemental analysis, gel permeation chromatography (GPC), simultaneous thermogravimetricdifferential thermal analysis-differential thermogravimetry (TG-DTA-DTG), electrical conductivity and atomic force microscopy (AFM). Key words: Supercritical carbon dioxide, Polymerization, Polypyrrole, Polythiophene, Copolymers, Characterization.
In the present study, the friction and wear properties of two high temperature resistant polymers, an amorphous polyetherimide (PEI) and a crystalline polyetheretherketone (PEEK), have been investigated at specific combinations of high pressure, velocity and temperature against smooth steel counterparts. The effects of internal lubricant, polytetrafluoroethylene (PTFE) and PTFE with short fiber reinforcements (carbon fiber) are outlined. The tests were performed on a thrustwasher testing machine under dry sliding conditions. Different analytical techniques were employed to study the correlation between the transfer layer and wear properties. Lubricated and lubricated-reinforced compounds showed excellent wear properties compared to pristine resins throughout all PV conditions.
Plastic Wood Composites, or commonly known as WPC, are a novel and interesting alternative to the usage of wood in certain applications, improving the properties of the final products thanks to the polymers intrinsic properties. However, compatibilization between the polymer matrix and the wood fibers or particles is a key factor that must be taken into consideration. Hydrophilic fibers are not compatible with hydrophobic polymer matrices, such as polyethylene or polypropylene (the main used polymers due to their processing temperatures and the low degradation temperature wood possess). The present research aimed to develop WPC using as the natural fiber recycled wood obtained from out-of-use leisure sailing ships. The objectives of the research presented and added new challenges on the development of such natural composites, posed by the state of the wood to be used, usually contaminated with salt, rests of minerals and rests of organic matter, so an excellent decontaminating process was a must. Once the wood conditioning processes were completed, a conventional extrusion process was carried out to obtain the WPC. The polymers used as polymer matrix were Low Density Polyethylene (LDPE) and Polypropylene (PP). Four different concentrations of wood fibers were used (10%, 20%, 30%, 40%) in order to determine their properties according to the fiber concentration. Also, two different compatibilizers for wood and polymers were used to check their behavior, as well as composites without compatibilizers were obtained. Finally, characterization techniques, including SEM microscopy, mechanical and impact properties and aging tests were carried out for all the developed WPC composites. Results indicate which were the best wood concentration on the composites as well as the best compatibilizer and its concentration on the final composite.
Three polypropylene-based materials (two talc-filled compounds and one unfilled homopolymer) were tested with two in-plane shear test methods (Iosipescu and V-notched rail). The three materials behaved differently in the shear tests. Most notably, cracks developed in tension near the notches for the particle-filled materials, while the unfilled homopolymer did not fracture. There were also differences between the materials regarding strain localisation between the notches, and thickness change in the sheared section. The stress-strain curves obtained with the two shear tests were quite similar.
This paper describes the calibration and verification of a material model used in the numerical simulation of mechanical loading of plastic parts. The material model features strain rate dependent yield stress, pressure dependent yield stress, plastic dilatation and damage. The model was calibrated with data from tests in uniaxial tension, shear and uniaxial compression, utilising 3D digital image correlation for full-field displacement measurements. Two load cases were simulated; centrally loaded clamped plates and three-point bending of bars. The predictions of force vs. deflection were good to fair. The results are discussed in terms of deficiencies of the calibration data, heterogeneity and anisotropy of the injection-moulded components, and shortcomings of the model.
The transesterification of PET and PEN in a twin-screw extruder (TSE) was investigated. A theoretical model, able to predict the extent of transesterification reaction (X) and degree of randomness (RD) against processing parameters along the screw axis is presented. PET/PEN blends were prepared via the melt mixing process. The axial dispersion model (ADM) was developed for modeling the twin screw extruder. Extent of transesterification reaction and degree of randomness was examined via Nuclear Magnetic Resonance Spectroscopy (H-NMR). Theoretical and experimental results were in good agreement, allows the prediction of the X and RD as a function of processing parameters such as time, temperature and composition.
Using short term tests to predict future outcomes of any long term process is common in extrapolation techniques in Science, Social science and Engineering. However, in every process it is important to ascertain some sort of criterion before extrapolation techniques are employed. The criteria for predicting lifetime of an engineering plastics for the specific application must include the requirements of the test to (a) reproduce the mechanisms of field failures and (b) have a technically sound procedure for extrapolation of a the relatively short test data. We will finally propose a quantitative modeling approach as an alternative to “empirical” extrapolation.
Both industrial and scientific interest in poly(lactic acid) (PLA) increased in recent years for various reasons; hopes are rising that this material may represent an alternative to commodity polymers. In order to answer these expectations, thorough characterization and modification of poly(lactic acid) is necessary. The actual presentation focuses on the mechanical properties, especially the impact resistance of PLA. Attempts were made to improve this characteristic by blending with both rigid and elastomeric polymer grades. The blends were characterized with various techniques in order to compare toughening methods in these systems, and enlighten the relationship between interactions, structure and macroscopic properties.
Stress corrosion cracking (SCC) in polyolefin pipes usually starts as a microcrack colony within a degraded layer adjacent to the pipe surface exposed to combine action of mechanical stress and chemically aggressive environment. One can distinguish four stages of SCC: 1) microcracks initiate within the degraded polymer; 2) slow growth of individual cracks; 3) strong interaction of cracks and formation of clusters; and 4) clusters growth and crack/or cluster instability leading to the ultimate failure. The stage of crack initiation is primarily controlled by chemical degradation, and the second stage is strongly related with the effect of mechano-chemical degradation at process zone. The interaction of multiple cracks and clusters are typically observed after the many cracks grow individually. In this paper, the mechanism of crack initiation and growth due to mechano-chemical degradation is addressed and modeled.
Automotive Sunroof Systems, which have become a must have for the added comfort and styling to today s cars, increasingly rely on engineering plastics functionalities to replace metals. Structural and semi-structural Sunroof module components, Sunroof frames in particular, typically need to meet a wide range of technical requirements, with a clear focus on integration of functions, safety, cost and weight reduction. The glass-reinforced materials, thermoplastics and thermosets, currently used for Sunroof frames are mostly based on PBT/ASA, PBT, PA, PP and unsaturated polyester SMC. These products are not a perfect match for the application needs of today and the future. Glass-reinforced SMA/ABS on the other hand offers an ideal, unique combination of properties required in Sunroof frames and systems. SMA/ABS-GF compounds such as Polyscope s Xiran® SG grades have clear technical and commercial benefits: • high dimensional stability and precision • very low warpage, compliance to mold cavity shape • good performance at low wall thicknesses • high creep resistance • excellent adhesion without surface treatment • low density, high economic value • good chemical resistance • easy recyclablility with efficient waste streams.
Scope of our work has been development of a new type of coupling agent by which processing of long carbon fibre reinforced composites by injection moulding will be possible since hindering the fibres from breakage and simultaneously improving the mechanical properties. Resistance of LLDPE of 1-10% carbon fibres against tensile and flexure stresses has been investigated. Tensile strength has increased by 30% and flexure strength has gained 90% related to the neat polymer. Fibre/matrix interaction has been studied on SEM graphs and a polymer layer has been observed to be connected to the fibre in additive treated fibre containing composites.
To cope with increasing demands on ultraprecision profiling and finishing of aspheric lens molds, we have implemented an ultra nanoprecision aspheric grinding system to be mounted with an ELID(ELectrolytic Inprocess Dressing)-capability and on-line feedback capability of profile accuracy. A cemented carbide mold has successfully ground and finished to be with several nanometric surface smoothness and with ultraprecise profile accuracy by just grinding process with ELID mechanism. Some specific conditions have been investigated to achieve better accuracy and quality on molds. This paper presentation introduce those R&D activities and also discuss on the latest achievements on this topics, with showing injected aspheric lenses by the molds.
Acoustic properties of polymer compounds are an important consideration for many applications. Currently there is a standard test method for the determination of the sound impedance and absorption properties of materials but there is no such test for the property of sound transmission loss (STL). The equipment used for the impedance and absorption standard test can, however, be adapted to measure the sound transmission property. The objective of this project was, therefore, to assess this testing method for STL and to carry out an initial investigation on the relationship between the structure of plastic compounds and their acoustic transmission property.
Microwave heating has a number of advantages in comparison to the conventional method due to the ability to heat a part of polymeric material directly through specific interaction of electromagnetic radiation with selected types of materials. Most thermoplastics are relatively transparent for microwave irradiation and they do not absorb microwaves to a sufficient extent to be heated. In such case, enhanced microwave heating can result from the use of fillers such as carbon black. In this paper, the ability of different thermoplastic polymers as polyurethane, poly(vinyl chloride) and carbon black filled polypropylene to absorb microwave irradiation and to be foamed using chemical blowing agents is discussed. The temperature changes of such materials as the heating effect under microwave irradiation with various power were investigated. Selected polymeric materials with additive of chemical blowing agents were foamed under microwave irradiation and the influence of foaming conditions on cell structure and apparent density of porous products was analyzed.
Polyamides are widely used in many applications. There is a vast amount of recycled polyamide coming from the carpet and textile and other industries. Due to degradation and loss of viscosity, this recycled polyamide has reduced performance and limited its use. The unique chemistry of alternating copolymers of ethylene and maleic anhydride provide several advantages for upgrading recycled polyamide. This paper discusses the results obtained with compounding prime grade polyamide as well as recycled polyamide with the addition of small quantities of this copolymer and specific property improvements for applications in injection molded compounds.
Processes to print, stamp, mark, label or otherwise deposit graphics onto molded plastic products are collectively known as plastics decorating. Given decorating processes, graphic types and production requirements, no single decorating method fits all projects and, conversely, most projects have more than one viable decorating method. For your latest new product design or redesign, one challenge is determining which decorating processes are options. This challenge is an equation of sorts with several factors to consider including: 1. graphics details required; 2. molded plastic part characteristics; and 3. production demands. The following pages guide a discussion of these factors.
Although the process of selecting the right polymer for new medical devices has not changed very much in the last 10 to 15 years, the degree of complication seems to have grown exponentially. The variety of specially designed materials, the number of suppliers, some under the same name or others with a new corporate moniker, and the availability of reference databases puts a glut of information into the hands of the design engineers. But how does one successfully navigate through this information and decide on the one material that is best for their particular application. It is much more difficult to find live technical support from either suppliers or from database providers. With staff reductions and department consolidations, many companies have also lost experts from their library of specialists that in the past have led the selection of the optimum polymer for new applications. No longer do companies have the historical databank of material expertise or on-staff resources for guiding new project efforts. The level of experience in many companies is down while the breadth of knowledge is much more focused. This coupled with the evolution of far more complicated devices that often combine advances in multiple new technologies such as conductive polymers, shape memory materials, drug eluting devices and polymers that dissolve in the body all complicate the process of selecting the right polymer for the application. Medical devices designers and engineers are tasked with selecting just the right polymer for their devices; and this requires keeping in mind all the various requirements that must be satisfied including functional requirements, chemical and biological requirements and manufacturing, assembly and sterilization. Collectively, results of the evaluation of the materials used in the construction of medical device and the function of the devices together contribute to what many refer to as the biocompatibility of the device.
Composites of poly(caprolactone) (PCL) and multiwalled carbon nanotubes (MWCNTs) were produced by melt-mixing in a small scale compounder by varying the screw speed between 25 and 400 rpm at a constant mixing time of two minutes. By that, different levels of dispersions, as assessed by quantitative analysis of area ratio of remaining primary agglomerates from light microscopy, were achieved. With increasing screw speed the state of dispersion increases and levels off starting at about 100 rpm. Melt rheological properties were measured in frequency sweeps. Interestingly, distinct differences in the complex viscosity * and the storage modulus G’ were found in dependence on the agglomerate area ratio, whereas the loss modulus G’’ was not much influenced. The storage modulus at 0.1 rad/s initially increased with decreasing area ratios, showing that especially the storage modulus is very sensitive to the nanotubes dispersion state. It increased up to a mixing speed of about 75 rpm illustrating improved dispersion followed by a decrease when further increasing the speed. As GPC investigation showed no significant differences in the degradation of the PCL matrix depending on the rotation speed, the effect of decreasing rheological parameter was assigned to nanotube shortening. Both effects improved dispersion and nanotube shortening are also reflected in the electrical resistivity values of compression molded samples. Here, up to 75 rpm a decrease in resistivity due to the better dispersion was observed, whereas above 75 rpm, where dispersion had leveled off, again an increase was found reflecting the reduction in nanotube aspect ratio. Thus, it could be shown that rheological measurements are suitable to detect differences in the dispersion state in composites with a fixed type of CNTs and concentration but also the effect of nanotube shortening reflected in lower aspect ratios.
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