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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GPC CONTROL OF HOT-RUNNER TEMPERATURE IN INJECTION MOLDING
Injection molding is one of the most popular polymer processing techniques in plastics industries. Hot runner has become a standard component of injection molding molds due to a number of advantages, including reduction in raw material consumption, greater production rate, and lower power consumption. Hot-runner temperature distribution plays an important role in final product quality. A multi-input-multi-output (MIMO) generalized predictive control (GPC) is developed, implemented and tested for hot-runner temperature control on a reciprocating-screw injection molding machine. Experimental results prove that GPC can control hot-runner temperature accurately.
EFFECT OF EXPANDABLE THERMOPLASTIC MICROSPHERES ON MICROCELLULAR INJECTION MOLDED POLYLACTIC ACID (PLA): MICROSTRUCTURE, SURFACE ROUGHNESS, AND TENSILE PROPERTIES
Expandable thermoplastic microspheres were employed as chemical blowing agents to produce biodegradable polylactic acid parts. The surface characteristics of the samples were evaluated with a 2D surface roughness analyzer and a white-light 3D surface profiler. It was found that microcellular injection molded parts with ETM exhibit good surface quality, similar to conventional solid injection molded parts. The tensile properties of injection molded PLA samples with variable ETM weight ratios have been investigated. As shown by the testing results, the cell microstructures play an important role in the surface quality and mechanical properties.
THE EFFECT OF BROAD ORTHOGONAL COMPOSITION DISTRIBUTION ON ENVIRONMENTAL STRESS CRACK RESISTANCE IN POLYETHYLENE
Environmental stress crack resistance (ESCR) is a critical mechanical property for polyethylene in injection and rotational molding applications. Based on a very well characterized matrix of materials with widely varying densities and melt index, we have looked at broad orthogonal composition distribution (BOCD) as a means of improving ESCR without the processability and stiffness debits. Through blending high melt index, high density components with low density, low melt index components to a target MI/ density, ESCR improvements of up to two orders of magnitude are evident over their single component counterparts.
MEASUREMENT OF INTERFACIAL TENSION AND THREAD/DROPLET KINETICS VIA POLYMER MELT MICROFLUIDICS
We present a novel platform for measurement of droplet dynamics and interfacial tension via polymer melt microfluidics (PMM). We utilize a flow focusing technique to form droplets or threads which then travel down a central channel. Upon cessation of flow, we monitor the relaxation of the droplets and threads and extract their interfacial tension. We demonstrate the technique using a polystyrene/polyamide (PS/PA) system and use the deformed droplet retraction method (DDRM) to determine the interfacial tension without any pre-processing of the samples in a confined geometry. The result agrees well with that of a previous work.
SUBSTRATE EFFECTS ON THE CONFINED CRYSTALLIZATION OF POLYCAPROLACTONE IN COEXTRUDED NANOLAYERED FILMS
This paper examines the structure-property relationships of poly (caprolactone) (PCL) nanolayers confined by various polymer substrates. AFM, gas transport, and WAXS characterizations were utilized to demonstrate that confined PCL nanolayers crystallized as large in-plane lamellae of high aspect ratio. This phenomenon, previously observed only for poly(ethylene oxide) (PEO), may be a more general phenomenon of crystalline polymers. In-plane PCL lamellae were as effective as PEO in reducing the oxygen permeability by more than 2 orders of magnitude. Additionally, the confining polymer substrate was found to affect to orientation of the PCL nanolayers due to chemical compatibility or epitaxial induced crystallization.
BIO-PLASTIC SHEETS FROM MBM PROTEINS
The processability of meat-and-bone-meal (MBM) proteins via thermal routes was investigated. Batch compounding and compression molding were used to determine optimal compositions and processing parameters. The sheets were studied for their water vapor permeability, mechanical properties and environmental aging effects. The relative humidity (RH) of the ambient air played a significant role in the processing of the compounded protein.. Sheets were formed at 40-50% RH. As expected, mechanical properties of the sheets were also found to be moisture sensitive. Particle size of MBM raw material was also found to significantly affect the texture and mechanical properties of sheets.
STUDY OF INJECTION MOLDED MICROCELLULAR POLYLACTIDE (PLA)/POLY(BUTYLENES ADIPATE-CO-TEREPHTHALATE) (PBAT) BLENDS WITH VARIOUS COMPOSITION RATIOS
Foamed PLA/PBAT blends were processed via the microcellular injection molding process using supercritical N2 as a blowing agent. The effect of composition ratio on cell morphology, thermal properties, and mechanical properties of microcellular PLA/PBAT blends was investigated. Results showed that neat PLA presented a relatively small cell size and the cell size became larger from the skin to the central area. With increasing PBAT content, the cell size also increased, while the size distribution of the cells became uniform. The thermal properties of PLA, especially Tg, were slightly affected by the addition of PBAT. The crystallization behavior was noticeably influenced.
RHEOLOGICAL MEASUREMENTS OF LOW DENSITY POLYETHYLENE (LDPE)/SUPERCRITICAL NITROGEN (N2) WITH A SLIT-DIE RHEOMETER AND THE USE OF NUMERICAL SIMULATION
In this study, the rheological behaviors of single-phase LDPE/N2 solutions at various gas contents are measured using a high-pressure slit-die rheometer. The resulting rheology data of LDPE/N2 are curve fit using the Cross-WLF model, which were then used in simulation of microcellular injection molding processes. The pressure effect on the shear viscosity is also studied. In addition, A 3D plot of viscosity as a function of shear rate, pressure and temperatures has been constructed, which is more profound at high pressures, low temperatures, and low shear rates.
10-YEAR OUTDOOR WEATHERING OF MOLDED-IN-COLOR ASA RESIN
Acrylonitrile-styrene-acrylate (ASA) alloy formulated in nineteen high chroma colors were exposed for 10 years of natural (outdoor) weathering in Florida and in Arizona, and 10,000 kJ/m2 of artificial accelerated weathering testing under ASTM G26 protocol. Exposed specimens were evaluated numerically and visually to assess the color shift, and ten out of nineteen colors demonstrated excellent color stability after 10 years of outdoor exposure. It was observed that both colorant package and weathering protocol are the key factors for determining the color durability of the formulated blends. The accelerated test appeared over-predicting color shift observed in the natural weathering tests.
EXTENSIONAL RHEOLOGY OF RAW NATURAL RUBBER FROM NEW CLONES OF HEVEA BRASILIENSIS
Natural rubber (NR) is a biopolymer whose properties depend on the structure of the 1,4-cis polyisoprene chains, non-rubber constituents, environmental conditions. NR has been characterized by traditional methods, but these cannot effectively account for clone's differences. The aim of this work is to use extensional rheology to characterize and differentiate NR samples as for clone type and season of the year. Three IAC 300 series and RRIM 600 clones of Hevea brasiliensis tapped between October 2006 and August 2008 were investigated. The extensional viscosity varied considerably and was more sensitive than any other traditional property, being fundamental for monitoring purposes.
AN ENGINEERING APPROACH TO THE CORRECTION OF ROTATIONAL FLOW CALCULATIONS FOR SINGLE-SCREW EXTRUDERS - EQUATION CORRECTION
Simulation of single-screw extruder screws using the standard pseudo-Newtonian method is known to deviate from measured performance. Part of this deviation is caused by the calculation of the drag flow rate. Previous research has shown that the calculation of the drag flow rate using this method is higher than that in the actual channel, causing the pressure gradient to be incorrectly adjusted to compensate for the error in the drag flow term. The research here provides the correction factors for rotational flow (historically known as drag flow) such that axial pressure gradients can be quickly and accurately calculated.
DESIGN ASPECTS OF DISCONTINUOUS MOLD COOLING TECHNIQUES
The use of pulsed cold water instead of tempered coolant is suggested to be a versatile and cost-efficient technique for the cooling of injection molds. But the advantages and limitations of such discontinuous cooling strategies are still a controversial issue. In this paper the behavior of a discontinuous temperature control system is analyzed. The heat balance of a test mold is monitored and the inter?ªaction of adjacent cooling circuits is identified. It is demonstrated that the appropriate placement of the sensor whose signal is used as an input variable for the temperature control system is of crucial importance.
DEVELOPMENT OF A REACTIVE EXTRUSION PROCESS FOR THE CONTINUOUS SYNTHESIS OF POLYESTERAMIDES
Polyesteramides are among degradable polymers, which are of great interest for a wide variety of applications. In this paper we report a novel reactive extrusion process for the continuous synthesis of polyesteramides. It is based on anionic ring-opening polymerization of e-caprolactam in the melt of commercially available polyester - polycaprolactone. By this means polyesteramides of different chemical compositions were successfully prepared with high yield. Process simulation was carried out using obtained process and material data.
BIAXIALLY ORIENTED MULTILAYERED POLYMER FILMS FOR ENERGY STORAGE APPLICATIONS
Polymer films with enhanced dielectric properties are essential for the production of high energy density polymer film capacitors. By capitalizing on the synergistic effects of microlayering and biaxial orientation, polymer films using PET and a PVDF copolymer were produced which exhibit breakdown fields as high as 1000 kV/mm and energy densities as high as 16.2 J cc-1. Using needle/plane electrodes the fracture zones were investigated and it was evident that the layered films possessed a different fracture mechanism when compared to the single component films.
LASER SINTERING PROCESSES: PRACTICAL VERIFICATION OF PARTICLE COALESCENCE FOR POLYAMIDES AND THERMOPLASTIC ELASTOMERS
Polymer laser sintering is an Additive Manufacturing technology that has been implemented in a variety of industries from automotive and aerospace to the sports and leisure sector. This paper will explore the use of hot stage microscopy (HSM) and differential scanning calorimetry (DSC) to measure and observe powder polymer behavior with respect to the requirements for laser sintering. By observing this behaviour in a range of polyamides and thermoplastic elastomers, the results can be used as a tool for improved development of future materials, and potentially for process optimization, allowing laser sintering to compete in high volume manufacturing environments.
INVESTIGATION OF THE EXPANSION BEHAVIOR OF PE-LD FOAMED WITH CO2
The combination of PE-LD and CO2 to extrude foamed semi-finished products is widely spread. Especially for the extrusion of foamed sheets the decrease in density and cell size leads to an effect, which reveals a wavy pattern transverse to the machine direction and is known as corrugation. Since this effect has not been investigated yet, it is systematically investigated in a research project at the IKV. The aim of the project is to determine the foaming, process and foam parameters which lead to corrugation and thereafter develop strategies to minimize the corrugation in foamed sheet extrusion.
EXPERIMENTAL STUDY ON INJECTION MOLDING OF WHEAT-STRAW/HDPE COMPOSITES
Filling polymers with wheat straw can be environmentally responsible and reduce cost. Nowadays most composites with natural fibers are processed by compression molding. This study examined the feasibility of manufacturing wheat-straw and high-density polyethylene composites by injection molding. MFI and thermal analysis of composites with different wheat straw contents were characterized. Mechanical properties of injection molded composites were measured. It has been found the melt points of all composites were about 135C. The fluidity, tensile and impact strengthes of the composites decreased while the wheat straw content increased. However, the flexural strength increased slightly with the increase in wheat-straw content.
BOSS DESIGN AND OPTIMIZATION FOR MICROCELLULAR FOAM INJECTION MOLDED PARTS
There are two basic models companies following when implementing the MuCell microcellular foam injection molding process. The first and most common implementation is to apply the technology to a part designed for solid. The second implementation involves parts designed specifically to optimize performance with the microcellular foam process. In either case, the customer needs to understand the expected performance of the fastening mechanism. This study identifies the achieveable fastening performance with screws when using boss designs for standard solid injection molding and also identifies the optimum design geometry for microcellular foam molded boss design.
MICRO INJECTION MOLDING: CHARACTERIZATION OF CAVITY FILLING PROCESS
Based on reciprocating micro injection molding machine, this paper characterizes the influence of machine process parameters and its transition response from velocity control to pressure control (V-P transition) on the micro cavity filling process. The method of Design of Experiment was employed to systematically and statistically investigate the effect of machine parameters on actual cavity filling process, which was described by the defined process characteristic values (PCVs). The statistical analysis indicated that injection speed was dominated factor affecting all PCVs in cavity filling process. It was also found that the machine V-P transition have significant effects on cavity filling.
EVALUATION OF BIODEGRADABLE COPOLYESTER RESINS WITH INCREASED GREEN CONTENT
Three different biodegradable copolyesters with increased green content (starting from 31 %) made from recycled post consumer poly(ethylene terephthalate) (PET) were evaluated in comparison to commercial poly(butylene terephthalate-co-adipate) (PBAT) in terms of thermal, rheology, and physical properties. The melting temperature of the resins is lower compared to commercial PBAT due to the presence of isophthalate and traces of diethylene glycol (DEG) linkages from PET. The melt flow values are 2.5 times higher than those of commercial PBAT, which has extensive branching. New resins show low crystallinity, high flexibility, and no break at maximum elongation compared to commercial PBAT.
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