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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Enhancing Cell Nucleation for a Novel Microcellular Injection Molding Process Using Gas-Laden-Pellets
A novel and cost-effective method of microcellular injection molding using gas-laden pellets has been developed. In this study, several methods, as well as their combinations to enhance the gas-laden pellets’ foamability, have been attempted including (a) enhancing homogeneous nucleation by blending N2- and CO2-laden pellets to create an N2/CO2 synergetic effect, (b) enhancing heterogeneous nucleation by incorporating talc as a nucleating agent, and (c) enhancing heterogeneous nucleation by compounding PP/HDPE immiscible blends. The results show that these methods effectively improved the cell nucleation rate and cell morphology. Moreover, it was found that these methods could also be superimposed on one another without conflict, thus leading to further improvements.
The Newly Developed Fluorine Type Epoxy Resin Having Excellent Adhesion and Low Dk/Df Characteristics
The mobile communication devices require high speed transmission of large volume data and reduction in size and weight. When signal is transtitted in high speed and frequency on PCB, signal integrity becomes a big problem. One of the most widely used methods to solve the problem is to apply materials having good adhesion and low Dk/Df characteristics. Although various materials are available for the purpose, they tend to be expensive and require special care during the fabrication process. Therefore, PCB makers have been looking for more affordable and easily handleable materials that can be implemented outstanding adhesion and low Dk/Df. To meet these demands, we have developed epoxy resins containing fluorine. This fluorine type epoxy resins are obtained by applying fluorine based materials having high adhesion and low Dk/Df properties. So after epoxidation, the introduction of fluorine into the chain of the epoxy resin resulted in improving the adhesion and dielectric properties.
Experimental Studies on Extrusion Process of Polypropylene Double-Lumen Micro Tube in Medical Applications
A polymer micro tube with multi-lumen is difficult to fabricate. In this study, an extrusion die of double-lumen micro tube was designed and fabricated. Different processing conditions affecting the ovality and the thickness uniformity were investigated. The results indicated that the contour ovality was significantly influenced by gas flow rate, screw speed, die temperature and vacuum degree of water tank. The thickness uniformity of micro tube was determined by the die design method and the manufacturing precision. The desired double-lumen tube with an outer diameter of 1.6 mm was obtained by the optimization of processing conditions.
Improving Foaming Properties of Low Melt-Strength Polyethylene via Controlled Crosslinking
Crosslinking is widely used to improve foaming properties for low melt-strength polyethylene. However, premature crosslinking will not only suppress the growth of microcells, but also severely affect the melt processibility. It is thus very difficult to obtain highly crosslinked foamed polyethylene products. This paper describe a novel foaming process through manipulating the viscoelasticity of the polymer melt in response to the decomposition of the chemical blowing agent (BA). Practical guidelines to achieve low density polyethylene foam products with high crosslinking degree are provided.
The Gas Counter Pressure Effect on the Carbon Fiber Orientation Distribution Study in Injection Molding
With a large demand of polymer composites in all manner of industries, product development has focused on good mechanical strength and functionality with fiber composites. The key of development lies on the control of fiber orientation and distribution. This study applies Gas Counter Pressure(GCP) in injection molding to investigate the fiber orientation on different layers of thickness(core, shear and skin) and numerous part locations(far, center, and near as referred to the entrance of gate). As a result, the counter pressure is directly related to fiber orientation. Under the molding parameters of 80°C mold temperature, 230°C melted temperature, and 10cm3/s injection speed, the higher counter pressure, the greater anisotropic fiber distribution. Since GCP forced the core to skin, the most anisotropic distribution is on core layer, then the orientation and skin layer in sequence. For the fiber orientation in part, it has better anisotropic fiber distribution around the area farther from the gate, which is because the fiber orientation perpendicular to the cross section of product is affected dramatically by the pressure. In addition, a simulation tool, Moldex3D, is utilized to verify experiment results. The simulation shows high agreement with experiment on the trend of various locations. It can be proved that injection molding with GCP can increase disturbing level effectively.
Preliminary Evaluation on the Influence of Gas Counter Pressure on the Process Flow Characteristics, Molecular Orientation and Qualities of Injection Molded Parts
In this study, various polymer materials (PP, PS), product thicknesses (0.6 mm, 1.2 mm), and flow rates (5 cm3/s, 10 cm3/s, 15 cm3/s, 20 cm3/s, 30 cm3/s) were discovered by utilizing a developed molding technology called Gas Counter Pressure (GCP). Both conventional and GCP molding were performed to compare the associated influences on part shrinkage, mechanical properties, crystallinity, and shape of Melt-Front Area (MFA). The results show not only simulatively, but also experimentally that the shrinkage is reduced under GCP condition. What’s more, the degree of elastic module is enhanced, and the average ratios of tensile strength for both 0.6-mm-thick PP and 1.2-mm-thick PP increase 0.1937% and 4.6014% respectively due to the holding effect applied under GCP condition while the average ratio of tensile strength for PS decreases 1.8994% owing to the restricted molecular orientation. Furthermore, average ratio of crystallinity decreases either 1.987% (0.6 mm) or 2.560% (1.2 mm). In addition, Scanning Electron Microscope (SEM) diagram illustrates that the profile of melt-front for GCP molding is obviously flattened.
Polyvinyl Alcohol Foaming with CO2 and Water as Co-Blowing Agents
This paper investigated the continuous extrusion foaming of a biodegradable polymer, polyvinyl alcohol (PVOH), using supercritical carbon dioxide (scCO2) as the blowing agent. As-received PVOH pellets were first compounded with water to decrease the melting point of PVOH. In addition, the water can help to reduce the potential for thermal degradation during the extrusion foaming process. Furthermore, water also served as a co-blowing agent together with scCO2 to achieve high expansion and high cell density biodegradable polymer foams. The effect of scCO2 content and die temperature variations on the expansion ratio and cellular morphology of the PVOH foam were examined systematically.
Tack Property and Cure Behavior of High Performance Carbon/Epoxy Prepreg
The cure kinetics and tack properties of carbon/epoxy prepreg and epoxy resin were investigated. The effects of cure temperature on the cure kinetics were investigated with dynamic DSC and isothermal DSC analysis. The cure temperature range was 180-240°C and heating rate was 2-40°C/min, respectively. Activation energies were determined for resins from dynamic DSC tests by using Ozawa and Kissinger models. Consequently, the activation energy for epoxy resin increased as a function of conversion. Tack property of carbon/epoxy prepreg was measured by using probe tack test. The influence of contact time, contact force, debonding rate and plate temperature on the carbon/epoxy prepreg tack was investigated.
Heating System Optimization Design for Rapid Thermal Cycling Mold Using Particle Swarm Optimization and Finite Element Method
Heating efficiency and cavity surface temperature distribution are two key factors for the design of heating system in rapid thermal cycling molding (RTCM) mold with electric heating. Aiming at high heating efficiency and uniform cavity surface temperature distribution, an optimization method combining particle swarm optimization (PSO) with finite element method (FEM) is proposed to design the electric-heating system in RTCM mold. To verify the effectiveness of this method, the PSO-FEM method is applied to design the electric-heating system for an automotive spoiler blow mold. The results demonstrate that the proposed optimization design method can effectively obtain the optimal design parameters and significantly facilitate the heating system design process compared with the trial and error design method. Based on the optimized design parameters, an electric-heating RTCM blow mold of the spoiler is constructed and utilized to mold the automotive spoilers. The blow molding experiments conducted using the constructed RTCM mold show that the surface quality of the molded spoilers is dramatically improved.
Validation of Polyethylene Pipe in Potable Water Systems
A new methodology has been developed to assess the performance of polyethylene pipe compounds in potable water applications. The methodology is the result of several connected research programs undertaken to both develop and validate a model capable of estimating performance of PE pipe in potable water applications. The validation methodology is based on testing specimens at accelerated conditions in accordance with the approach developed in ASTM F2263 to determine the minimum Stress Class at aggressive end-use environments. The resulting projections are seen to be in good agreement with those projected from full ASTM F2263 testing and, hence, provide an alternate approach for projecting PE pipe compound performance in potable water applications. The approach is also well suited for use in developing minimum performance validation criteria.
State-Of-The-Art Additive in Automotive Plastic Applications or How Performance and Aesthetics Can Meet Sustainability
Innovation in additives continuously enhances the offering to the plastic industry. Conversion processes of engineering thermoplastics compounds can be very demanding, especially when reinforced with fillers like glass fibers. Performance, quality, productivity and weight reduction are the automotive industry drivers for plastic applications, combining excellence and awareness. The answer to these needs is the development of specific additives or solutions which provide to the compounds, outstanding protection and process improvement ability, with a particular focus on sustainability.
A Mechanism for Solid Bed Breakup in Single-Screw Extruders - Solid Bed Shape Change
It is well known that solid bed breakup in plasticating single-screw extruders can lead to defects in the downstream product, reduced rates, and process instabilities. After a review of the mechanism of solid bed melting an enhanced discussion will be presented regarding a new concept for solid bed break up. The literature generally attributes this breakup to pressure gradients emanating from the beginning of the metering section of the screw. In a previous paper  a new mechanism was proposed that was developed as a result of the physics of the melting mechanism and fluid flows associated with screw rotation physics. During the discussion after the presentation of this new mechanism at ANTEC 2013, questions were raised as to the assumptions made regarding the shape change of the solid bed during melting which the authors proposed was a result of the flow that occurs as a result of the new mechanism. In this paper more data will be presented that will help define this new concept.
Determination of Kinetic Cure Parameters Considering Specific Heat Temperature Dependence
In this work, an algebraic-differential equations (EAD) system is applied to estimate parameters using both isothermal and non-isothermal data. Temperature dependence of the specific heat is considered inside the EAD as an algebraic restriction. The estimation procedure is based on the use of a mass and energy balance in DSC furnace. The approach found all kinetic parameters by using deterministic and heuristic algorithms. The results show that the use of an energy balance is a good methodology to estimate cure kinetic parameters of both isothermal and non-isothermal experiments.
Morphology and Physical Properties of Biodegradable Multicomponent Blends with Polylactic Acid
Poly(lactic acid) (PLA) is one of the most promising biodegradable aliphatic polyesters derived from renewable resources and has received significant attention over the last decade. The blending of PLA with poly(butylene adipate-co-terephthalate) (PBAT) and poly(butylene succinate) (PBS) is employed to overcome its inherent drawbacks. All prepared fully biodegradable blends show a thermodynamically stable complete wetting behavior which was in good agreement with the thermodynamic analysis. The results for the ternary blends demonstrate a viable route towards the achievement of biodegradable polymers systems with a highly balanced property set.
Development of Hybrid Magnetic Nanoparticles Aimed to Collect Crude Oil in Aqueous Environments
Well-defined, magnetic shell crosslinked knedel-like nanoparticles (MSCKs) with hydrodynamic diameters ca. 70 nm were constructed through the co-assembly of amphiphilic block copolymers of PAA20-b-PS280 and oleic acid-stabilized magnetic iron oxide nanoparticles. These hybrid nanomaterials were designed as sequestering agents for hydrocarbons present in crude oil. Their combination of amphiphilic organic domains, for aqueous solution dispersibility and capture of hydrophobic guest molecules, with inorganic core particles for magnetic responsivity, make these nanomaterials uniquely qualified for oil spill remediation. The employment of these MSCKs in contaminated water resulted in the successful removal of the hydrophobic pollutants at a ratio of 10 mg of oil per 1 mg of MSCK. Using a magnet, the loaded nanoparticles were isolated and through “rinsing” in an ethanol sonicating bath, they were regenerated for reuse with no loss of their loading capacity.
Rheological Analysis of Branched-Polypropylene Produced through Reactive Extrusion
Traditionally, polypropylene (PP) has not performed well in polymer processing dominated by extensional flow due to a lack of melt strength. High melt strength (HMS) can be achieved in PP through the introduction of long chain branching (LCB). These branches introduce a large amount of chain entanglements, enabling PP to perform well in extensional flow processing. The characterization of long chain branched PP is not trivial and requires some expertise and advanced analytical analysis. This work will briefly review a variety of rheological techniques, both shear and extensional, that can be used to detect varying levels of LCB in PP.
Crosslinked Polyurea Aerogels
The structure-property relationships of polyurea aerogels made using two aromatic diamines and a triamine crosslinker are compared. Diamines were chosen based on previous work reported on polyimide aerogels. Polyurea segments were created by reacting one diamine species with 4,4’-diphenylmethane diisocyanate (MDI) in anhydrous N-methyl-2-pyrrolidone (NMP). These isocyanate-capped segments were crosslinked with 1,3,5 triaminophenoxylbenzene (TAB). Gels were dried under supercritical condition after exchanging the solvent with liquid carbon dioxide. The aerogel articles were obtained with density between 0.20 and 0.23 g/cm3, average pore sizes between 11-15 nm, porosity between 81-86%, and surface area between 111 and 394 m2/g, and onset of thermal decomposition at 250 °C.
Development of Polypropylene Microporous Hydrophilic Membranes by Blending with Acrylic Acid Grafted Polypropylene
Cast films based on a polypropylene (PP) blended with a commercial acrylic acid grafted polypropylene (AA-g-PP) through melt extrusion were prepared in order to develop hydrophilic microporous membranes. FTIR analyses showed that the addition of the modifier changed the crystalline lamellar structure and, consequently, the membrane morphology. Scanning electron microscopy (SEM) images showed smaller pore size and lower number of pores as the modifier content was increased. Oxygen content of the precursor film surface was determined using XPS. Water vapor permeability (WVTR) was significantly higher at a low concentration of the modifier, compared to the neat PP. This is attributed to the introduction of polar groups on the surface, with a small change in the crystalline structure.
The Effect of Isomer on the Thermal and Rheological Properties of Polyetherimides
Thermal and rheological properties of poly-(ether-imides) with Meta and Para monomer isomer types were investigated using oscillatory rheology and thermal characterization techniques. The poly-(ether-imide) synthesized from Para based isomer showed an improved Tg with superior chemical resistance while still maintaining at least 90% of the flow properties. The observed shift in Tg and minimal differences in shear thinning index were most likely due to differences in entanglement density and relaxation dynamics between the polymers. Additionally, we have attempted to show-case the predictive capabilities of non-linear vs linear rheology in differentiating the structure-property relationship between isomer types.
Thermo-Mechanical and Morphological Properties of Clay/Nylon-6-Epoxy Nanocomposites
A novel procedure to synthesize in-situ clay/nylon-6 composite suspension was explored via anionic solution polymerization. The suspension was efficiently blended with water-based epoxy resin using mechanical stirrer at room temperature. Hence, a 3-component coating system was obtained consisting of nano clay, nylon-6 and epoxy resin. Large number of coatings and films were prepared with variation in clay and nylon-6 loading. Concentration of clay was found to have profound effect on crystallinity of nylon-6, thereby affecting the overall properties of clay/nylon/epoxy composite. All the films were characterized for thermal and dynamic mechanical behavior using Differential Scanning calorimeter (DSC) and Dynamic Mechanical Analysis (DMA). Lower amount of clay was found to increase the crystallinity of nylon-6 which in turn increased the plasticization of epoxy resin indicated by reduction in Tg. A multiphase morphology with distinct amorphous and crystalline zones was observed under Scanning Electron Microscopy (SEM). A remarkable symmetrical morphology with branched dendritic crystal structure was observed for few of the clay/nylon/epoxy system.
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