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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Selectivity and Reactivity in the Chlorination of PVC Model Compounds in Radical-Complexing Solvents
A potential route to the preparation of poly(1,2-dichloroethylene) (PDCE) through the selective chlorination of poly(vinyl chloride) (PVC) was explored. Certain solvents can play a very important role during free-radical chlorination because they form complexes with the free chlorine atom and thus change the chlorination pattern. In our work, the photochlorination of three model compounds for PVC, namely, 2,4-dichloropentane, 3-chloropentane, and 4-chloroheptane, was carried out with molecular chlorine in the absence or presence of complexing solvents. The effects of these solvents on the chlorination selectivity for these model compounds were explored. During the conventional chlorination of alkyl chlorides with molecular chlorine, a bridged-radical intermediate is believed to be involved, and for this reason, vicinal chlorides are the major products. However, we found that because of polar effects and resonance stabilization, the yields of geminal chlorides increased significantly in the presence of complexing solvents. Such solvents also are well known to decrease reactivity in free-radical chlorinations with Cl2. Thus, for both of these reasons, the chlorination of PVC with Cl2 in complexing solvents is unlikely to be useful for the preparation of PDCE.
Structure – Property Relationships in Lightly Crosslinked Polyolefin Foams
It is well known that viscoelastic behavior strongly affects the properties of lightly crosslinked cellular polymers (e.g., thermoformability, primary and secondary foamability). Polyolefin foams, crosslinked to equivalent gel levels by either irradiation (< Tm) or peroxide (>Tm) processes, exhibit different viscoelastic characteristics in the melt state. This implies that polymer crosslinking and foam expansion dynamics play critical and sometimes interrelated roles in defining material properties, and that sol/gel measurements alone cannot adequately characterize these networks due to entropic (i.e., network order) effects. The effect of network order on the viscoelastic properties of crosslinked cellular polyethylene was systematically studied as described herein.
Impact of Fiber Orientation Distribution within a D-LFT Strand on Warpage of a Compression Molded Part
The fiber orientation distribution within an LFT charge was measured using micro-computerized tomography (?CT). With a ?CT data processing software package based on a grey value threshold algorithm, the local fiber orientation could be quantified. A 3D mold filling simulation that considers the initial orientation of the D-LFT strand was performed. The results of the fiber orientation distribution of the finished part were compared with results based on the assumption of a perfectly random initial fiber orientation. The initial fiber orientation has an impact on the final orientation depending on certain conditions such as mold coverage. Furthermore, small divergences in the final fiber orientation can lead to 50% variations in warpage predictions.
Improving Electrical Conductivity in Carbon Nanotube Composites Using Supercritical Carbon Dioxide
The interconnectivity of carbon nanotubes (CNT) in a composite plays a significant role in determining its electrical conductivity. Treating CNT with supercritical carbon dioxide (scCO2) decreases CNT bundle size benignly increasing the overall surface area of the CNT available for polymer interactions during melt compounding. Previous work has focused on improving the scCO2 treatment of highly entangled CNT for use in electrically conductive thermoplastic nanocomposites. This work investigates the effect of scCO2 treatment on less entangled, yet longer CNT with greater potential to enhance electrical conductivity (EC). Following scCO2 treatment CNT/polycarbonate nanocomposites were melt compounded. The resulting materials were analyzed for morphology using transmission electron microscopy (TEM) and optical microscopy. Furthermore, the electrical properties of the composites were studied. The onset of electrical percolation was observed to decrease significantly with scCO2 treatment.
Clean and Cost-Saving: New Developments for Meeting Medical Molding Challenges
Medical products understandably must meet the highest level of quality and consistency due to the nature of their use. This often puts difficult demands on molders of plastic medical products who must work hard to meet quality restrictions through elimination of such things as hydraulic fluid and other contaminants in the molding area. As with all manufacturing there is the additional demand for reducing costs in a competitive market and this is always challenging. Finally, the global effort toward sustainability in manufacturing challenges molders and mold builders alike to jointly plan and implement more green manufacturing processes via a reduction in energy usage among other things. This paper will discuss the use of innovations within the injection mold manufacturing and molding markets that will help medical molders achieve clean room molding, cost reductions, and lower energy consumption.
Morphological Development of Latex Particles in a Solvent-Free Extrusion Process
This paper reports on the influence of factors involved in the preparation of polyester latex in an aqueous medium using a twin screw extruder. In this work, screw speed was found to have no influence on the residence time (or axial mixing) in the process while the resin-to-water ratio in the early dispersion zone appeared to significantly affect both residence time and particle size. In an attempt to visualize the melt in the dispersion zone, conditions inside the extruder were used to hamper phase inversion. A morphological study of samples under such conditions by scanning electron microscopy showed a bi-continuous matrix formed stratified fibrils and nodular-extended clusters as mechanical action worked to increase the interfacial area between the water and resin leading up to the phase inversion point. Increasing the water content in the dispersion zone had the qualitative effect of increasing the presence of the bicontinuous morphology.
New Polycarbonate-Polysiloxane Copolymer Blend Resins for Consumer Electronic Applications
Developments in mobile phone housings place more and more demanding requirements on thermoplastic materials with respect to impact, flow and chemical resistance. Polycarbonate-polysiloxane copolymer resins offer significant improvements in low temperature impact and chemical resistance compared to polycarbonate resins. This improvement is most significant at high polysiloxane contents, but such copolymer resins can suffer from aesthetic issues, like pearlescence and gate blush, due to the presence of relatively large siloxane domains within the polycarbonate matrix. This paper discusses new polycarbonate-polysiloxane copolymer blends that offer good chemical resistance and excellent flow and low temperature impact, with aesthetics very similar to polycarbonate resins.
Improved Nanocomposite Dispersions Produced by a Melt-Mastication Process
Described is a new processing technique termed Melt-Mastication (MM), for improved nanocomposite dispersion. Compared to a conventional melt processing technique, MM improves the dispersion of fumed silica, halloysite nanotubes, and expanded graphite in isotactic polypropylene (iPP) and linear low density polyethylene (LLDPE). Transmission optical microscopy shows MM fragments nanoparticle clusters above a critical size (~8-10 ?m). Differential Scanning Calorimetry indicates the crystallization temperature increases for composites processed by MM. Modest improvements in storage modulus (5-7%) are also observed after MM. Melt-Mastication employs conventional processing equipment, and therefore presents a promising opportunity to improve commercial processing of polyolefin nanocomposites.
High Flow SF Ultem™ Resin Materials for High Heat Thin Wall Consumer Electronics Application
Trends in consumer electronics towards design freedom, miniaturization, high modulus, weight reduction and lower system costs have resulted in an increased usage of high flow high heat thermoplastics. SABIC recently introduced its Ultem™ SF resin portfolio, a family of high flow glass filled polyetherimide polymers. The resin has outstanding mechanical properties and dimensional stability at elevated temperature and increased flow ability compared with that of the traditional GF filled Ultem™ resin grades. This paper will compare properties of Ultem™ SF resins with the GF PES materials. Some potential application of Ultem™ SF resin grades will also be discussed.
Reactive Extrusion of Cross Linked Block Copolymers - Structure and Potential as Impact Modifier for Pa 6
Recent studies show that blending PA 6 with a novel polyether block copolymer results in blends with high impact strength and high stiffness compared to conventional rubber blends. The block copolymers used as impact modifiers were prepared by continuous anionic polymerization in a reactive extrusion process (REX) using a twin screw extruder. They are semi crystalline and partially cross linked in contrast to commonly used amorphous and uncured rubbers. The structure of the blends was analyzed using different analysis methods like atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Due to the cross linked structure of the block copolymers, the particles in the blends are not spherical like the particles of conventional rubbers. The differences in molecular structure, miscibility and grafting of the impact modifiers result in different mechanical properties and very different blend morphologies.
Coatable Wood Plastic Foams for Automotive Applications
The automotive Industry is searching for lightweight materials to decrease the energy that is needed to move a car. Especially materials that can be used for mass production are requested. Assisted injection molding methods like the water injection process are capable to fulfill these requirements. Another possibility to make thermoplastics even more light is to foam them, this causes a loss of mechanical strength. To improve the strength of the foamed material, natural fibers (NF) can be embedded. Both, the foaming and the use of NF, lead to an unsightly surface. So the surface on the exposed side has to be painted. State of the art is to coat plastic surfaces with polyurethane (PUR) . In this study an acrylonitrile butadiene styrene (ABS), reinforced with wood fibers (WF), was foamed. One aspect of the material choice was that it can be coated with PUR in a one-shot-process. The mechanical properties of NF and foam modified ABS compounds were investigated. The adhesion between ABS and PUR was also verified.
Material Concept for Large-Scale Production of Finished Colored External Body Panels in Automobile
Lightweight construction is the elementary key of the Volkswagen CO2 reduction strategy. The goal is to design a car which is efficient as possible. The reduction of energy usage during production of the car as well during moving the car leads to research of new materials and new applications in the automotive Industry. The Volkswagen CO2 reduction strategy has three Main topics: • The right material at the right place • Reach the best Customer satisfaction • Use of new Technology including multi material design for Steel, Alumina, Plastics In the case of Plastics is the use of foamed polymers in combination with In-Mold coating is one focus of Volkswagen research. The following paper shows general lightweight aspects as well the topic “class A” surface for foamed body panels with the goal to use this process in a large scale.
The Effect of Reprocessing on Mechanical Properties of Polypropylene
Polypropylene (PP) was injection molded up to 20 runs to study the effect of recycling procedures. The influence of the recycling was studied by observing changes in melt viscosity, tensile and impact resistance properties. The main effect of recycling was decrease in melt viscosity, which is attributed to molecular weight reduction. The observed degradation processes only slightly affected the small strain properties of the materials studied. However, break properties were affected apparently. All the tensile properties related to breaking as well as impact resistance of recycled polypropylene decreased with recycling.
Formation of Part Defects in Water-Assisted Injection Molding (WAIM): Influence of Process and Material Parameters
Water-assisted injection molding (WAIM) enables the production of hollow or partially hollow products, having a higher quality and lower process cost when compared to products produced with other and earlier developed plastic processing techniques. However, the occurrence of (unwanted) defects in the final product is one of the current limitations of the WAIM process, for which in available research until now no clear explanations exists. In this study, the influence of process and material parameters on the occurrence of part defects was examined in a pre-defined reference experiment. With a qualitative defect analysis, it was found that within the reference setting a high water temperature, a low melt temperature and water holding pressure as well as the addition of nucleating agents are more favorable. The experimentally observed changes in defect occurrence, under influence of the applied parameter variation, can herewith be explained with the proposed definitions of the different defect types and their responsible formation mechanisms. In this way, the principle mechanisms behind the formation of part defects are enclosed in these definitions and mechanisms, which hence contribute to a more fundamental understanding of the WAIM process.
Binary Blends of Cycloolefin Copolymers
Binary blends of different grades of cycloolefin copolymers (COC) were prepared at different compositions via compounding in a twin-screw extruder. Thermal, mechanical and rheological properties of the COC blends were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rotational rheometry. Results revealed the differences in the miscibility of different grades of COCs. This could be attributed to differences in the microstructures of the COCs determined by their synthesis method (catalyst type) and norbornene content of each component. Blends of Topas 8007 and Topas 5013 were immiscible but they were compatible to a certain degree. Two distinct Tg’s were observed at DSC and DMA, with a slight shift upon changing the composition of the blends. DSC data was used to model this behavior using two parameter Kwei model for the prediction of the Tg for the immiscible COC blends (8007/5013). Rheology data of the blends revealed that the phase inversion occurs at 45%-55% for the blends of two different Tg COCs. On the other hand Topas 8007 and Topas 6013 blends were miscible and single Tg was observed at DSC. Fox equation was used to model the Tg behavior of the miscible blends and the experimental results were in close agreement with the model.
Physics-Based Film Blowing Modeling to Enhance Empirical Film Property Predictions from Polymer and Processing Parameters
In this paper physics-based modeling of the film blowing process is combined with empirical film property relations. A hybrid approach for polymer processing-property prediction is provided. A continuum mechanics model is implemented to enhance the nominal fabrication input with calculated stresses, strains, and related parameters. Nominal and calculated parameters are candidate inputs for empirical property prediction. Data is used from various (linear low-density polyethylene) LLDPE resins, run under different conditions at laboratory and commercial-scale film blowing lines. The results based on temperature-dependent Newtonian constitutive relation indicate that the strategy lead to significant improvement of a quality of prediction of certain film properties.
Curing Study of a Green" Thermosetting Resin"
A series of green" thermosetting resins oligomers of bis(hydroxyalkylene)-2-mercaptosuccinate has been reported recently . Curing in these thermosetting resins results from crosslinking via pendant thiol groups. As part of an effort to realize and assess the potential of these resins as sustainable materialsthe curing process was investigated using differential scanning calorimetry (DSC) and rheology. The progression of physical and mechanical properties such as the glass transition temperature (Tg) and the shear moduluswas monitored as a function of time and temperature. Tg of the resin was found to increase with curing and the averaged Tg of the fully cured resin was found to be 72.6 K ± 1.2 K higher than uncured resin. The increase in Tg corresponded with the change in rheological properties. The shear modulus obtained for fully cured samples reached a high modulus of 6.5 × 106 Pa at 200 °C. Additionallythe gel point was measured from the crossover of the storage and loss moduli. Based on the gel points the apparent activation energy of curing also was determined."
Unexpected Dependence of Hydrolytic Performance of PC/ABS Blends: Specificity of Buffer Cation Type
Compromised performance of hydrolytic stability has previously been shown in emulsion-ABS impact modified PC blends, resulting from acidic residual surfactants and coagulants in the impact modifiers. To neutralize the residual emulsifiers and coagulants in emulsion-ABS, buffers were added to the blends during the compounding step. A comparison of PC molecular weight retention upon hydroaging between blends with added buffers in different cation forms revealed enhanced hydrostability in blends added with a cation specific buffer. The addition of buffer containing the specific cation presented here holds promise as an effective strategy for improving hydrostability in PC/emulsion-ABS blends during compounding.
Thermal and Rheological Behavior of Plasticized Polyacrylonitrile and Melt Spinning of Precursor Fibers
While there is tremendous interest in the melt spinning of polyacrylonitrile (PAN) with presence of plasticizers, the behavior of plasticized PAN melt and the spinning process have not been adequately investigated so far. In this paper the melting and rheological behavior was studied for PAN plasticized with water or water and a second plasticizer. A lab scale pressurized fiber spinning system was developed and used to generate melt-spun fibers as carbon fiber precursors. The morphological and mechanical properties of the fibers were evaluated and compared with commercial wet-spun fibers. The meltspun PAN fibers have surface and mechanical properties similar to those of commercial fibers.
Morphological and Rheological Properties of PBS/Silica Nanocomposite Manufactured Using a High-Speed Twin-Screw Compounder
The effects of silica chemistry and high-speed compounding on the morphology and rheology of poly(butylene succinate) (PBS)/fumed silica nanocomposites were investigated in this work. The filler content of the nanocomposites was determined by thermogravimetric analysis and matched estimated values well. Depending on the distribution and surface chemistry of fillers, distinct surface texture could be identified in the PBS/silica nanocomposites. Using high-speed mixing and compatibilizing surface functionalizations can result in enhanced polymer-particle interactions and influence the composite rheology dramatically. The relaxation hierarchy can be identified from the linear viscoelastic response of PBS compounded with mixture of modified and pure fumed silica particles.
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