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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Isothermal Crystallization of Isotactic Polypropylenes: Experiments and Simulation
The isothermal crystallization of isotactic poly?propylenes (iPP) was investigated by polarization micro?scopy (PLM). The crystal radius evolution and the transformed volume fraction were obtained by PLM experiments. In this paper, a general differential system for 2D quiescent conditions was adopted to describe the crystallization evolution of iPP. Matlab was used for the simula?tion of the crystallization evolution. There was good agreement between the experimental and simulation results of the transformed volume fraction and the radii of crystals for the 2D condition.
Thermal Analysis of Polylactic Acid and Corn Zein Composites
Polylactic acid (PLA) was blended with corn zein and various compatibilizers in order to study a composite with potentially improved barrier and thermal properties. Thermogravimetric analysis (TGA) was used to characterize the thermal stability of the composites in comparison to pure PLA, and it was determined that the thermal properties, specifically the onset degradation temperature and rate of degradation of PLA and its composites are extremely dependant on the test method utilized. In this study pure Natureworks 2002D PLA displayed onset degradation temperatures ranging from 306øC to 360øC, depending on whether or not an isothermal hold was incorporated into the TGA method. Rather than improving the thermal stability of the PLA, the addition of corn zein catalyzed the reaction, increasing the rate of degradation, and decreasing the onset degradation temperature.
A Study on the Effect of Twin-Screw Melt Blended Nano-Fillers on Polypropylene Nanocomposite Hybrid Electrical and Morphological Properties for Supercapacitor Applications
The electrical conductivity of polypropylene (PP) was improved via the addition of carbon-based nanoparticles such as graphene and multi-walled carbon nanotubes (MWCNT). In addition, a hybrid composite structure consisting of PP matrix, polyaniline conductive polymer, as well as carbon-based nanofillers. The samples were fabricated via melt blending technique which is capable for large scale industrial production. Electrical conductivity measurements determined that the electrical performance of nanocomposite was increased 10 orders of magnitudes to a maximum value of 2.5?10-4 S/cm, achieved by 20wt.% polyaniline (PAni), 5wt.% MWCNT, and 75wt.% PP samples. The increase in electrical conductivity was attributed to the formation of conductive networks observed under SEM and AFM. The samples were further characterized via TGA analysis technique to verify its content. These nanocomposites are developed for future supercapacitor current collector applications.
Effect of Glass Fiber on Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)
Bacterial polyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), with two different 3HH molar fraction were mixed with short glass using mini-extrusion and injection moulding process. The effects of short glass fiber addition on tensile properties were analyzed. The tensile strength and elastic moduli of both resins were significantly increased while failure strain decreased with increasing fiber loadings. Young's moduli of the composites at different fiber loadings were compared with five different micromechanical models. It was found that the model proposed by Pan has the best match with our data.
Characterization of Solution Cast Exfoliated Graphite Nanoplatelet / Polylactic Acid Nanocomposite Films
Exfoliated graphite nanoplatelets (GNP) / polylactic acid (PLA) composite films are fabricated using solution casting. GNP is dispersed in a chloroform suspension via ultra-sonication and the GNP/chloroform suspension is added to a PLA/chloroform solution. The solution is then casted yielding nanocomposite films with a thickness of ~200 ?m. Film morphology, examined using scanning electron microscopy (SEM), indicates minimal surface defects, but significant micro-porosity. The thermal behavior and crystal structure are examined using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The films display high crystallinity of only one à phase crystal form. The mechanical properties are greatly improved upon compression molding the films samples after solution casting due to the evaporation of remnant solvent and the decrease in micro-voids caused by the applied pressure.
On the Entanglement Density and Chain Stiffness of Copolycarbonates Containing Rigid and Flexible Linkages
Thermal and rheological properties of LexanTM XHT (rigid) and LexanTM HFD (flexible) copolymers were investigated using oscillatory rheology and thermal characterization techniques. The incorporation of 20% rigid co-monomer on a neat Lexan TM has increased the glass transition temperature (Tg) by 30øC while increasing the entanglement molecular weight by 50%. Also, for the copolymer with a flexible co-monomer, the glass transition temperature (Tg) has decreased by 20 øC while hardly affecting the entanglement molecular weight. These results suggest properties related to chain stiffness can vary in a non-linear fashion with the nature of co-polymer content.
Fatigue Performance of Fused Deposition Modeling Style 3D Printed vs. Injection Molded Ultem 9085
Advancements in fused deposition modeling (FDM) have provided an opportunity for the production of functional, lightweight parts for advanced automotive and aerospace applications. Designing reliable parts requires a thorough understanding of the tensile and fatigue properties of not only the material, but of the complex printed structures. In this paper, polyetherimide/ polycarbonate copolymer blend (PEI/PC) tensile bars were fabricated by both FDM and single- and double-gated injection molding for tensile and fatigue properties studies. FDM bars were printed vertically and horizontally to compare the anisotropic effects inherent to the fabrication method. The density of the FDM parts was also varied by controlling the degree of contact between printed toolpaths. All FDM samples exhibited lower modulus, yield/break stress, density and endurance limit compared to injection molded parts. A different fatigue behavior from classic fatigue theory was also found to occur in the FDM samples.
A New Styrenic Block Copolymer Designed for Polyolefin-like Processing for Compounding, Films and Fibers
Block copolymers are highly valued for their ability to be extruded and injection molded in combination with other materials. However, they are typically processed in the phase separated state. The high melt elasticity of the phase separated block copolymer leads to a variety of problems with mixing and small dimension articles such as films, fibers and thin walled parts. A new hydrogenated styrenic block copolymer has been designed to process as a single phase melt but retain its two phase nature at use temperatures to provide strength and creep resistance. The processing and resulting properties of the pure polymer and combinations with a variety of polyolefins will be explored.
Abrasive Wear and Speed Relationship in Technical Compounding
An accelerated wear test was performed in a 60 mm TriVolution? compounder. An aluminum element was placed before the melt zone of the extruder where wear was expected to be highest. 50 lb of an abrasive compound were mixed in the extruder and the weight of the elements was measured before and after the test. The test was repeated at different speeds. It was found that with increasing speed a rapid increase in wear per pound of material could be observed. It was determined that it is beneficial to operate the extruder at low speed and high torque as this produces less wear than operating at high speeds and low torques.
Aging of Physical Properties in Ionomers Modified with Fatty Acid Salts
The physical property aging that occurs in ethylene-based ionomers is primarily due to the formation of secondary crystals, which proceeds slowly over the course of several weeks. Modification of ionomers with fatty acid salts, which results in useful materials for the golf ball application, causes a strong suppression of primary crystallization and enhances the relative amount of secondary crystallization that occurs. Thus, the aging that occurs in ionomers modified with fatty acid salts is more pronounced than in standard unmodified ionomers. Exposure to moisture during room-temperature aging also increases the magnitude of physical property aging in ionomers modified with fatty acid salts.
Durability Studies of Biodegradable Polymers under Accelerated Weathering Conditions
Poly (butylene adipate-co-terephthalate), (PBAT) and poly (butylene succinate), (PBS) are promising biodegradable polyesters whose blends have gained great attention in wide range of applications. However, there are some drawbacks to the use of these biodegradable polymer blends in durable applications. The main disadvantage of these materials is hydrolytic degradation at elevated temperature and humidity. In this study, we have assessed the durability of PBAT, PBS and PBS/PBAT blends at 50 oC with 90% relative humidity (RH) for duration of up to 18 days. The mechanical properties of these polyesters were evaluated before and after 18 days of conditioning at 50 oC with 90% RH. The mechanical properties of the polyesters were affected with increasing conditioning time. This can be attributed to the susceptibility of ester bonds to hydrolytic degradation at elevated temperature and humidity. The hydrolytic degradation was further confirmed by scanning electron microscopy
Mechanical Property Enhancement in Recycled High-Density Polyethylene (rHDPE) via Solid-State Pulverization Methods
Low-temperature, solid-state pulverization processes are explored for transformation of postconsumer, recycled HDPE (rHDPE) into value-added applications. A process called solid-state/ melt extrusion (SSME), comprising sequential solid-state pulverization and melt extrusion in a single twin screw extruder, was found to impart significant morphological and rheological changes in rHDPE, which in turn lead to improvements in tensile ductility and toughness to the level of those found in typical neat, virgin HDPE.
Core Surface Treatments to Investigate Adhesion of Thermoplastic Coatings for Aerospace Fasteners
Hybrid designs consisting of a thermoplastic coating molded around non-thermoplastic cores are being investigated for use in aerospace fastener applications; however, interfacial adhesion between these materials is a challenging prospect. This paper examines the performance of tensile bars made from core materials that have been encapsulated with various engineering thermoplastics. The goal of this investigation is to determine if surface treatments on the core materials improve the peak torque and tensile load. The surface treatments explored include surface abrasion, a thermoset polyurethane primer, and an amino-silane coating. These treatments were applied to steel, aluminum, and carbon fiber/epoxy cores which were subsequently encapsulated with Polyoxymethylene (POM), Polyphenylene Sulfide (PPS) or Polyetherimide (PEI). Surface abrasion was the only surface treatment that had an effect on the adhesion between the resins and cores. Neither Polyurethane nor the silane treatment appeared to have a significant effect either positively or negatively on adhesion. The use of carbon cores proved to have a negative effect on adhesion compared to the metallic cores. Thermal analysis revealed reduced crystallinity may have had an effect on the PPS samples molded, significantly lowering their performance.
Using in Mold Pressure Sensors to Monitor the Microcellular Injection Molding Process
The MuCell ? process for producing microcellular injection molded parts is accepted as a technology for providing a more dimensionally stable part through a reduction in residual stress with increased productivity over compact molded parts. As commercial acceptance of the process grows, processors want to apply currently accepted methods of in-mold process monitoring. However, these methods do not necessarily transfer directly to the microcellular foam molding process due to significantly different in-mold pressure conditions that result from the fact that cell growth provides the packing pressure.
This paper will look at typical pressure profiles for the microcellular foaming processes and how these can be used to monitor the process for part consistency.
Blue Undertone Enhancement of Black and Grey Pp Injection Molded Parts for Automotive with Ultramarine Blues
Polypropylene has become the leading polymer for automotive applications. Black and grey are the most popular colors in injection molded parts for that industry. In the case of blacks, desired properties are: high jetness, high bluish undertone, good mechanical properties, good surface appearance, good weatherability and high gloss (depending on the application). The highest performing Carbon Blacks all alone cannot reach the target black color requested by the automotive industry. Either they have high jetness but lack blue undertone or they have high blue undertone but lack jetness. This paper intends to prove that High Performance Ultramarine Blues are a very suitable option to enhance the blue undertone of black colored PP injection molded parts while not damaging other key characteristics as jetness, mechanical properties and weather fastness. Moreover, the paper highlights the benefits High Performance Ultramarine Blues show when formulating greys by increasing its blue undertone and hence improving aesthetics by removing the yellowish undertone more associated to brownish/dirty greys.
High Performance Cellulosics for Demanding Medical Device Applications
The increased use of disinfectants to combat hospital-acquired infections (HAIs) has created materials engineering challenges for medical device manufactures and designers. As disinfecting frequency increases, chemical resistance, e.g., environmental stress cracking, becomes increasingly important for materials historically used to manufacture medical devices. Although the chemical resistance requirements for materials are becoming more stringent, device designs continue to be complicated and intricate, limiting manufacturers? abilities to transition to a highly chemical resistant material if the material does not also exhibit ease of processing. This work investigates and outlines the processing and chemical resistance advantages of Eastman Tenite? propionate 360, a material manufactured from the bio-renewable resource, cellulose.
Fundamentals of Optimized Mold Cooling System Design for Injection Molds
Mold cooling has evolved, just like mold machining has required faster machining, new mold cooling components are increasing efficiency of required mold cooling. Advancements through the years as specialized material selections for cooling components, conformal cooling inserts, and back again to components utilizing standard machining practices. There are new mold cooling components used to reduce machining time by reducing mold component lengths and therefore shortening plate thickness. Historically mold cooling was designed to circulate water or cooling medium through the mold base plates primarily and not necessarily within the cavities or cores. This practice usually required many different levels of cooling lines and thicker mold plate assemblies. The newer advancements create a circulation that is now optimized within mold plates and specialized within the cavities and cores to reduce mold heights.
Study of Overmolding a Foamed Thermoplastic Polyurethane Layer on a Polypropylene, Polycarbonate, or Polyoxymethylene Substrate
Products with a laminated two-layered structure can be produced by the overmolding process. In this study, a layer of thermoplastic polyurethane (TPU), foamed by the microcellular injection molding process using supercritical fluid (SCF) nitrogen, was overmolded on a polypropylene (PP), polycarbonate (PC), or polyoxymethylene (POM) substrate. The resultant composite structure had micro?cellular foamed TPU overmolded on different polymer substrates. Further mechanical testing on samples showed that a thin layer of foamed TPU increased the strain at break and the overall toughness of the sample by more than 300 %. This property could be used to design parts, where catastrophic failure needs to be avoided. Scanning electronic microscopy (SEM) images and further shear tests show that foamed TPU has better adhesion to PC than POM and PP.
Ultrasonic Treatment of PP/CNT Composites during Twin-Screw Extrusion: Effect of Screw Configuration
PP/CNT composites were prepared by means of an ultrasonic twin extruder with three screw configurations at ultrasonic amplitudes up to 13 ?m to compare the efficiency of different configurations in dispersing CNT in PP. Using these screw configurations, the ambient pressure in the ultrasonic zone was adjusted in order to observe the effect of pressure on ultrasonic cavitation behavior in PP and PP/CNT composites. The results indicated that the dispersion of CNT in PP is more related to the number of kneading elements in the configuration, and less to the residence time. This was explained by the mixing effect from the flow analysis network (FAN) simulation. It was also found that at the same amplitude of ultrasonic treatment PP degraded more at lower ambient pressure. Additionally, the ultrasonic treatment increased the dispersion level of CNT in PP with the best improvement not always occurring at the highest amplitude. At the lowest ambient pressure the cavitation in the polymer matrix was intense but it had not always led to the best dispersion possibly due to the suppression of the cavitation in the agglomerates. In the screw configuration of Design 2 which related to a second highest ambient pressure, composites prepared at an ultrasonic amplitude of 10 ?m exhibited elongation at break as high as is 320% compared to 247% for the untreated composites.
Melt Temperature Measurement in Compounding
The single most important parameter in compounding polymer products is melt temperature. Melt temperature has a greater impact on product quality than any other parameter in the compounding process yet it is often overlooked in both its importance and with regard to the difficulty and necessity of proper measurement.
Melt temperature is a response variable that must be controlled within a specified range to produce the highest quality compound possible. Failure to accurately measure or maintain the proper melt temperature can lead to unexplained variability in process yields, finished product properties and customer acceptance.
This paper discusses the fundamental requirements of melt temperature measurement during compounding. Properly measuring and controlling this fundamental variable is critical to consistently producing high quality polymer compounds.
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