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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A Safe and Low-Odor Organic Peroxide Formulation Designed for the Rotational Molding of Crosslinked Polyethylene
The rotational molding industry has experienced safety, hygiene and quality issues when using 2,5- methyl-2,5-di(tbutylperoxy) hexyne-3 (referred to as P-H3 in this paper). P-H3 at >93% assay is the traditional organic peroxide crosslinker for the rotational molding of crosslinked HDPE. P-H3 is classified as a subsidiary explosive based upon United Nations and USA safety testing. Furthermore P-H3 exhibits undesirable air and skin hygiene issues during the manufacturing and handling of crosslinked parts due to the primary skin irritants that are created when P-H3 decomposes to crosslink the HDPE. These low molecular weight triple bond by-products are also responsible for the discoloration of the crosslinked HDPE. The under-cure and general “inconsistency of cure” quality issues are traced to the incompatibility and volatility of P-H3 in the HDPE molding powder. Years of safety testing and R&D culminated in the development of Luperox® MIX (referred to as P-MX in this paper), specifically designed for the safe and reliable rotational molding of crosslinked HDPE. P-MX is a homogeneous blend of m/p-di(t-butylperoxy)diisopropylbenzene, triallyl cyanurate and a free-radical trap. The data in this technical paper demonstrates how P-MX addresses certain safety, hygiene and quality issues of P-H3. P- MX is a homogeneous solid at room temperature, with a 45°C melting point.
The Application of Rheological Techniques in Selecting Plasticizers for PVC Processing
This paper focuses on three different rheometric techniques to analyze how dibenzoate and other plasticizers affect flexible polyvinyl chloride (PVC) processability. Both plastisol and melt compounds will be considered. This analysis includes the use of a research rheometer in an oscillatory mode to evaluate plastisols. A torque rheometer was used to evaluate melt compound formulations. New dibenzoate plasticizers and a new monobenzoate have been introduced and the nature of the solvator class of these new benzoates will be evaluated.
Thermal Stability of Castor Oil Derived Polyurethanes
Polyurethanes synthesized using both unmodified and epoxidized, ring opened castor oil as a polyol were prepared and their thermal properties tested using thermogravimetric analysis and differential scanning calorimetry. Chemical changes upon degradation were investigated using Fourier transform infrared spectroscopy. The kinetics of degradation were elucidated using the Flynn-Wall and Flynn procedures. Epoxidized castor oil produces a rigid polyurethane exhibiting glassy behavior at ambient temperatures. All methods to determine activation energy of degradation indicate that, in a nitrogen environment, polyurethanes from unmodified castor oil are more thermally stable than those from modified castor oil. The appearance of peaks corresponding to amines, amides, and esters in FITR analysis of degraded samples suggests that the initial degradation step of the polyurethanes studied is the breaking of the urethane bond.
Effects of Glycerin Antifreeze on CPVC
There are multiple applications where chlorinated poly(vinyl chloride) (CPVC) may come in contact with glycerin. One common application is in fire suppression systems that could be subjected to subfreezing temperatures. Chlorinated poly(vinyl chloride) is increasingly being used for these systems in place of metal because of its many advantages, including the ease of installation, weight reduction, cost benefits and chemical resistance. When CPVC piping is used in an area that has the potential to freeze, an antifreeze solution must be used in the fire suppression systems to suppress the freezing temperature of the water and reduce possibility of failure of the piping system. Glycerin is a commonly used antifreeze for this application. The following article discusses the effects of using glycerin with CPVC piping and presents a case study of the use of bio-derived glycerin as an antifreeze agent. In general, it was found that glycerin from the bio-diesel industry had adverse effects on the CPVC.
Fabrication and Characterization of Polyvinyl Alcohol (PVA)/Nanofibrillated Cellulose (NFC) Filaments
This paper presents a new process to fabricate single polyvinyl alcohol (PVA)/nanofibrillated cellulose (NFC) filament and its tensile properties at various ratios (0.5 ~ 3 wt %) of NFC. The fabrication process generally contains four steps: NFC isolation, preparation of PVA/NFC solution, gel spinning and drying, and filament stretching. The ultimate strength of PVA/NFC increased by almost 2 times, compared with stretched neat PVA filament. In order to ensure that the NFC fibers disperse well in PVA solution, high shear processing was employed. To study the possible degradation of PVA caused by high shear, the parallel plate rheometer was used to investigate the viscosity of PVA/NFC solutions. The PVA crystal orientation in PVA/NFC filament was also characterized by wide angle x-ray diffraction (WAXD).
Fractographic Examination of Failures in Polycarbonate and Polyacetal due to Impact, Tensile, Fatigue, and Creep Mechanisms
Fractography is a powerful tool in the failure analyst’s arsenal, allowing unknown conditions that led to a failure to be revealed by examination of a fracture surface. In this study, fractures generated by different failure mechanisms were examined by scanning electron microscopy (SEM) to discern key characteristics and distinguishing features. Amorphous polycarbonate (PC) and semicrystalline acetal homopolymer were fractured by impact, tensile overload, cyclic fatigue, and creep. SEM images are provided and discussed.
Impact Modification of PLA Using Biobased, Biodegradable Mirel PHB Copolymers
This work will focus on an approach to improve the impact toughness of poly (lactic acid) or PLA without compromising the biobased carbon content and compostability of PLA. Specifically, low-crystallinity and amorphous PHB copolymers were demonstrated to be very effective in improving the toughness of PLA at modest loading levels of 10-20 weight percent. This presentation will also compare the above approach with urethane, butadiene and acrylic impact modifiers along with the impact modification provided by other compostable polymers such as PBS and PBAT. Of particular significance is the extent of impact modification provided by an amorphous PHB copolymer (M4300 @ 10-20% loading) wherein the blend demonstrates a combination of mechanical properties that rival those of some engineering thermoplastics. Morphological considerations for the observed improvement in impact performance will also be highlighted.
The World's Highest Heat Melt-Processable Amorphous Thermoplastic
A new class of high performance amorphous thermoplastic polyimide (TPI) resin has been designed with a glass transition temperature exceeding 300°C while still being 100% melt-processable. Further, this novel material has been bestowed with the highest UL (Underwriter’s laboratory) RTI rating in the world for an unfilled thermoplastic. The polymeric material offers outstanding high temperature strength and dimensional stability which makes it attractive to be positioned in applications with an emerging need of such materials that are truly melt-processable while giving as-molded properties for end use.
Complex Fiber Orientation Distributions within Injection Molded End-Gated Plaques
The Method of Ellipses has been applied to short and long fiber polymer composites in order to quantify the fiber orientation distribution within the end-gated plaque. Short and long glass fibers with post- processing average fiber lengths of 0.364 and 3.90 mm, respectively, have been studied at multiple percentages of mold flow, including at the gate and entry region and near the advancing front. Additionally, orientation data has been acquired for short glass fibers at multiple locations of plaque width including near the side mold wall. Preliminary data suggests that the orientation of short and long glass fibers is similar along the centerline of the plaque, with both fiber lengths developing the predicted core-shell structure at moderate to high percentages of mold fill. However, short glass fibers exhibit a broad and relatively uniform orientation distribution in the regions of complex flow at high percentages of plaque width, with a substantial increase in flow-aligned fibers. Work is ongoing to complete analysis of long glass fibers in regions of complex flow near the side walls of the mold.
Material Optimization and Performance Evaluation of PolyVinyl Alcohol (PVOH) Films in Fresh and Salt Water for Decelerator Applications
Material optimization of biodegradable and water soluble polymers along with the influence of fresh and salt water conditions on the performance of polyvinyl alcohol-based films was examined for a U.S. Naval sonobuoy decelerator application. PVOH films of various thicknesses were produced on a manufacturing-scale lamination line using a solvent-based adhesive. Salt water and its temperature significantly influenced dissolution properties of the films. Mechanical properties of the as-received and laminated films were also examined and reported.
Effects of Biodiesel on Plastics
Many chemicals have the ability to attack on plastics as solvents and can lead to failure. In some cases, the source of the solvent is not well defined. In this study, the effect of biodiesel, a fatty acid methyl ester, on various plastics, namely polyamide 6 (PA 6), polycarbonate (PC), acrylonitrile-butadiene- styrene (ABS) and ABS/PC plastic blends was studied. Various feedstocks of biodiesel were also studied, including, soy bean oil (new and used), animal fat (tallow), corn oil as well as choice white grease. The plastics samples were tested under ASTM standard where a predefined strain is applied to the samples prior to exposure to the solvent (biodiesel). It was found that under the majority of combinations, other than PA 6, cracking was seen within 12 hours, and with ABS/PC and PC cracking was seen in minutes. Thus, it has been shown that biodiesel can be a degrading solvent for engineering plastics, such as PC, ABS and ABS/PC blends.
The Effect of Processing Flows on Polystyrene/Nanotube Nanocomposite Conductivity and Structure: 3D Visualization of Cluster Distributions
The electrical conductivity of polymer nanotube composites can be dramatically modified during processing steps. We examine the interplay between processing, the multi wall carbon nanotube (MWCNT) network structure and the resulting conductivity through 3D measurements of cluster size distributions and orientation. We discover that the nanotubes assemble into clusters whose mass distribution follows a classic power law with a slope of approximately -1. This mass distribution is relatively insensitive to the imposed flows over our accessible shear range, even though the conductivity changes by orders of magnitude. The orientation distribution of the MWCNTs within the clusters is strongly dependent on the flow type and its magnitude, but does not correlate with conductivity. These results point to the dominant role played by the nanotube –nanotube contact resistance as a determinate of composite conductivity.
Investigation of Cold-Runner Injection Molding Processing Parameters and Their Effects on Product Optical Properties
This paper describes current efforts to investigate and expand melt modulation capabilities to control the packing parameters of cold-runner based injection molding processes. Packing parameters, including packing pressure and packing time, have significant impact on the internal molecular orientations, mechanical properties and optical performance of injection molded polymeric products. The investigation focuses on manipulating and controlling packing parameters in order to produce molded parts with different optical properties in each injection molding cycle. Numerical simulations of common thermoplastic optical polymers, such as PMMA, PC, and PS and some experimental results are also presented.
Investigation of Fracture in Polymers Using a Cohesive Zone Model
Polymers are increasingly being used for engineering structures and medical devices because of their excellent corrosion resistance and low cost compared with metals. However, the lifetime of plastics used in severe environments is significantly reduced due to environmental stress cracking (ESC). Current understanding of ESC in polymers is mostly empirical. In this paper, a methodology for investigating ESC in polymers is presented. The proposed approach, based on the cohesive zone model (CZM), is capable to characterize the degradation in the fracture zone explicitly, independent from the bulk material. In our preliminary investigation, the fracture on an elastic-plastic material was simulated, and the results were compared to a published paper. The simulation outcome indicates that the CZM is an effective tool to study fracture propagation in polymers under ESC.
Effect of Ladder-like Polysilsesquioxane on the Surface and Thermomechanical Properties of Polyimide Based Block Copolymers
A novel type of polyimide (PI)-polyurea (PU) block copolymers containing polysilsesquioxane was successfully prepared by reacting ladder-like polysilsesquioxane (LPS) with poly(amide acid)-b-polyurea, followed solution film casting and thermal imdization. The LPS composed of mercapto and fluoride side groups was synthesized by using the sol –gel and monomer self-assembly methods. The resulting hybrid films have outstanding surface and thermomechanical properties. The dynamic contact angles (DCA) and dynamic mechanical thermal analysis (DMA) were used to study the surface energy and mechanical properties of the hybrid films. The presence of LPS containing fluoride and mercapto side groups dramatically increased in the degree of imidization by low temperature curing (150°C).
Specific Mold Filling Characteristics of Highly Filled Phenolic Injection Molding Compounds
The objective of the study is to analyze the influence of the mold filling behavior during injection molding of phenolic compounds on mechanical properties. Injection molding filling studies, mechanical testing and optical microscopy were done while varying mold geometry (injection gate and cavity height), mold temperature and injection rate during injection molding a highly filled phenolic compound. It was found that the mold filling behavior varies with changing the injection molding parameters as well as the mold geometry. In consequence of this the mechanical properties change according to the resulting reinforcement orientation.
Ultrasonic devulcanization of tire rubber of different particle sizes in twin-screw extruder
The present study is devoted to ultrasonic devulcanization of tire rubber particles of 10 and 30 meshes by means of a new ultrasonic twin-screw extruder. Ultrasonic amplitude and devulcanization temperature were varied at a fixed frequency of 40 kHz. The die pressure and ultrasonic power consumption during devulcanization were recorded. Degree of devulcanization was investigated by measuring the crosslink density, gel fraction and revulcanization behavior. Rubber of 30 mesh exhibited a lower die pressure and higher degree of devulcanization than those of rubber of 10 mesh. Due to the higher level of devulcanization and lower viscosity of devulcanized rubbers at higher amplitudes, the temperature of devulcanized rubbers at the die was reduced with an increase of the ultrasonic amplitude. Cole-Cole plots, crosslink density and gel fraction of devulcanized and revulcanized rubbers, revulcanization behavior, and modulus of revulcanizates separated in two distinct groups based on the level of devulcanization and effect on molecular structure of devulcanized rubber. Revulcanizates with a greater degree of devulcanization exhibited higher elongation at break, while those with a lower degree of devulcanization exhibited higher strength and modulus. Revulcanizates of rubber of 30 mesh exhibited a consistently higher elongation at break. The normalized gel fraction versus normalized crosslink density was described by a unique function independent of the processing conditions and rubber particle size.
Sustainable Materials for Horticultural Application
Bioplastic materials were compounded utilizing soy, poly-lactic acid (PLA) and poly-hydroxyalkanoate (PHA) biopolymers along with ethanol industry co-products and biomass additives to manufacture horticultural plant containers. Various formulations and processing conditions were studied to improve mechanical properties of the plastics. These materials were developed and compounded at Iowa State University and subsequently injection molded into 4.5 inch greenhouse pots at R&D/Leverage, Lee's Summit, Missouri. The bioplastic pots were evaluated for their performance by studying plant growth of vegetable and ornament crops grown in them under greenhouse and field conditions. The pots were also characterized for degradation and water retention. Commercial polypropylene pots, 4.5” green color, were used as the control treatment for the study. Comprehensive growth studies along with degradation results identified numerous bioplastic types that performed as well as or better than commercial polypropylene plant containers. Among the different material types, SPA-PLA, a blend of soy and PLA resins, was observed to produce the best results in terms of plant growth compared to polypropylene plastic pots during plant production. This is attributed to the slow release of fertilizing compounds during the degradation of soy protein. Certain bioplastic pot types were observed to retain soil moisture content over a longer time period than pots made from other environmentally friendly materials, such as paper or peat moss. Such properties are considered beneficial during the plant production cycle when using horticultural pots because they require less watering.
Film Casting of LLDPE/Clay Nanocomposites Without and With Compatibilizer with the Aid of Ultrasonic Treatment
One step process for ultrasonic compounding and film casting consisting of an ultrasonic extruder followed by a cast film machine was used to prepare cast films of linear low density polyethylene (LLDPE) and LLDPE/Clay 20A nanocomposites. Cast films of LLDPE, 90/10 LLDPE/compatibilizer, 95/5 LLDPE/Clay and 85/5/10 LLDPE/Clay/compatibilizer were prepared at take up speed of 1.524 cm/s (3 ft/min) and different ultrasonic amplitudes. The die pressure and ultrasonic power consumption were measured. X-ray patterns, NMR, FT-IR, thermal, and gas permeability properties of cast films were studied. The mechanical properties of the prepared films in the machine and transverse directions were measured. Cast films of LLDPE and 95/5 LLDPE/Clay nanocomposites were transparent, while cast films lost their transparency with addition of compatibilizers. The compatibilizer with higher maleic anhydride grafting showed better properties. The strength and oxygen permeability results improved significantly due to the addition of compatibilizer and ultrasonic treatments.
Mold Maintenance: A Strategy for Optimizing Mold Performance
All mold builders perform mold repair, usually on molds they built. But few strategize to also offer ongoing mold maintenance services. A system has been developed for training and certifying mold builders and to put in place a documentation software system that enables them to serve as an extension of molders' toolrooms, thus freeing up a molder's employees for only the most specialized on- site emergency mold repair work. This system, dubbed 'Certified Maintenance Provider', consists of training, software installation, and subsequent auditing, in order to position a mold builder to become a source for maintenance within the immediate region.
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