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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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.
The Study on the Cell Size and Cell Density Distribution in Microcellular Injection Process with Dynamic Mold Temperature Control Assistance Technology
MuCell® (Microcellular injection molding) is a well-known green molding technology, but the surface defects are the common limitation for its application. Nowadays, the cosmetic drawback of MuCell® process could be resolved via high mold surface temperature and gas counter pressure control. The purpose of this study is to realize the correlation of cell size and density between microcellular injection molding in different mold temperature and composite mold inserts (M333, QC-10 and M333 combination, and QC-10). The numerical approach was also discussed with Moldex3D. In the experimental results of rapid cooling between three kinds of mold-insert design, the QC-10 insert has the best cooling efficiency to achieve 10 °C/sec. When the initial mold temperature was set at 120 °C, the average cell size can also be reduced from 192.92?m, 123.95?m, and 84.97?m, with the cooling rate 1.1°C/sec, 5.1°C/sec, and 10.9°C/sec individually. The DMTC (dynamic mold temperature control) was proved that it not only improves surface quality of product but controls the cell quality in microcellular injection molding effectively.
Investigation on the Powder Concentration Distribution and Surface Quality for Metal Injection Molding
Metal powder injection molding (MIM) is the combination of conventional injection molding and powder metallurgy process. Through de-binding and sintering after molded by high-precision mold, metal injection molding can allows complex parts to be shaped at once and in highly mass production. Most of the MIM studies focus on the binder they used for feedstock but the research of the processing and solving the defects such as shrinkage, warpage and black line was lacked. In this study, the objective is to discover the surface defects caused by powder-binder separation and verified by numerical approach. The results show that the optimum molding parameters when injection speed is 80mm/sec and mold temperature is 40°C has the best surface quality which powder and concentration difference of binder can be reduced from 45.33% to 2.73%.
Injection Molding of Ultra High Flow Elastomers
The injection molding process parameters and the elastomeric components play a major role on the final properties of the injection molded parts. In this paper, a Design of Experiment (DOE) was used to investigate the effect of injection molding process parameters and the molecular weight of the elastomer on the properties of the injection molded parts. It was observed that dry blending of a low molecular weight/low viscosity polyolefin elastomer with a polypropylene random copolymer (RCP) in an at-press injection molding process, significantly improved the dispersed morphology of the elastomer domains in the continuous matrix phase. Therefore, the parts made with a blend of 200 MI, 0.870 g/cc ethylene-octene copolymer and a 20 MFR polypropylene random copolymer had a finer dispersed morphology than the parts made with a 5MI, 0.870 g/cc ethylene-octene copolymer which is difficult to disperse into the RCP matrix. As a result, the fine dispersion of low molecular weight elastomer (200MI, 0.870 g/cc) in 20 MFR RCP resulted in good impact strength. Another improvement was observed in the weld-line strength due to the homogeneity of the elastomer domain in RCP matrix.
A Method to Characterize Blowing Agent Concentration Effects during Polymer Processing
During processing of foamed polymer products, variations in the mix of the polymer powder and blowing agent (BA) can lead to unpredictable thickness and porosity in the final product. Alterations can result from non-homogeneous mixing, due to broad ratios of particle size of polymer powder and BA. This paper evaluates methods of determining blowing agent composition in PVC powder mixtures. Quantifying small ranges of BA content (1-2%) in PVC compound yields higher costs and challenges in the characterization when tested through standard methods. Such methods include TGA and DSC. This is mostly because they are based on mass determination. A method for quantifying such small concentrations based on determining the volume of gas-released was developed; this volume is the gas that does not dissolve in the solid. It can be assumed that the solubility of the gas in the solid is constant, therefore the free gas volume would be constant for a specific concentration of blowing agent. From this point gas volume will refer only to free gas or undissolved gas. Volume changes in blowing agents are two orders of magnitude higher when compared to mass changes. In this method the volume of free gas released during foaming formation is quantified and related to the amount of BA. This technique can address quality control and process tuning in the field of foaming powder blends.
Hierarchically Porous Polymeric Materials from Ternary Polymer Blends
Hierarchically porous polymeric materials with controllable pore size were successfully generated through a ternary polymer blending strategy. Polylactide/highdensity polyethylene/styrene-ethylene/butylene-styrene copolymer (PLA/HDPE/SEBS) was used as a model system to demonstrate this technique. After melt blending, the SEBS was driven into the HDPE phase owing to the presence of the PE block in the copolymer. With proper volume fractions of HDPE/PLA/SEBS (e.g., 25/50/25), a bi-modal, dual co-continuous morphology was obtained and hierarchically porous polymeric materials were further generated by selectively removing the PLA and SEBS phases. Annealing and composition variation were further employed to control the pore size and it is shown that the length scales, for each of the two co-continuous morphologies, can be controlled independently.
Radiopaque Filler Enhances Nanocomposite Catheter Shaft Performance
Nylon 12 and polyether block amide nanocomposites are being used to stiffen catheter shafts. Montmorillonite clay is the filler of choice to make the nanocomposite. Typically the construction is a dual layer where one layer is the nanocomposite and the second layer is a radiopaque layer. We are evaluating the possibility of combining radiopaque properties along with the nano fillers to enhance strength as well be visible under fluoroscopy. Our study is also aimed at looking at the effect of particle shape of the radiopaque filler on the final properties of the material. We want to evaluate if synergy exists between the nano particles and radiopaque fillers to further enhance the physical properties of the material.
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