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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Crystallization Characteristic and Heat Seal Properties of Biodegradable Films
Biodegradable polymer film was prepared from poly(lactic acid)/thermoplastic starch (PLA/TPS) blend by cast film process at 0, 5 and 10 wt% of TPS. The PLA and PLA/TPS blend films were heat sealed at heat sealed temperature of 90 and 100 °C. The heat seal time was varied from 0.5 to 2.0 s with a pressure of 0.2 MPa. The effect of heat sealed conditions on heat seal properties of PLA and PLA/TPS films was investigated. Heat sealed strength of PLA/TPS blend films decreased when increasing the heat sealed times. PLA/TPS heat sealed films exhibited greater crystallinity than the PLA heat sealed film, which characterized by crystallization kinetic study.
Acoustic Process Analysis of Rubber Compounding
Properties of rubber compounds differ batch-wise. This can lead to waste and, thus, it is desirable to reduce these variations. One reason for quality variations of rubber compounds is the discontinuous way of compounding in internal mixers. Mixing effects make it difficult to adjust the process parameters of internal mixers in order to guarantee constant qualities. Experienced operators of internal mixers observe that characteristic noises during the mixing process can be correlated with the state of mixing. Thus, a project has been started to use these mixing noises for the development of a control system for internal mixers, which is able to characterize the state of the rubber compound. First, a measurement system has been implemented which allows the online visualization and recording of the mixing noise. It is systematically analyzed how the mixing noise is related to the state of mixing and the resulting elastomeric properties. The results show a correlation between filler incorporation and the characteristic sounds.
An Interconnected Porous Poly(?-Caprolactone) Structure Fabricated by Micro-Cellular Injection Molding Combined with Chemical Foaming and Particulate Leaching
In tissue engineering applications, a scaffold containing an interconnected porous structure is often highly desired, since these interconnected pores allow nutrients and signaling molecules to rapidly diffuse into the material. A mass production method of fabricating a porous structure, microcellular injection molding, was combined with chemical foaming and particulate leaching methods to fabricate an interconnected porous structure made of poly(?-caprolactone) (PCL). Sodium bicarbonate (SB) was employed as the chemical foaming agent. The results showed that the interconnected porous structures of poly(?-caprolactone) were successfully obtained based on different material compositions. Sodium bicarbonate not only generated carbon dioxide as a gas blowing agent, but also served as the heterogeneous nuclei for the gas bubbles. Sodium bicarbonate and its byproduct, sodium carbonate, also became the porogens in the subsequent particulate leaching process. The morphology of the pores and interconnectivity were discussed in this paper. These interconnected porous structures have the potential to be used for tissue engineering scaffolds.
Application of Visual Mold for the Effect of Counter Pressure Mechanism on Gas-Assisted Injection Molding Process
Gas assisted injection molding refers to injecting gas into the short shot melt in the packing stage. Compressed gas is used as the medium to push melt and maintain pressure. Cost is saved by hollowed core. Therefore, the hollow rate and penetration length are required in end product quality. This study visualizes molding flow and uses a gas counter pressure mechanism in the gas assisted molding process. The melt flow behavior is influenced by controlling the counter pressure, making it possible to discuss the effect of a counter pressure mechanism on the hollow rate of gas assisted molded articles. This study designs an in-mold visible mold and uses a clip-shape cavity for an experiment on gas assisted injection molding with a counter pressure mechanism. The flow field of two-phase fluid and the fountain effect under different counter pressure conditions are observed by high-speed photography and adding particles. The relationships among the penetration length of the finished product, the hollowed evenness and the molding parameters are analyzed, and a database of gas assisted injection molding under counter pressure mechanism is created. The experimental results show that when the gas counter-pressure is applied to the gas-assisted molding, although the hollow area is reduced, the penetration length of the finished product can be increased, so as to make the hollow quality uniform. In addition, it is observed in the fiber orientation that the interlayer structural orientation is made uniform as the counter pressure increases, meaning the counter pressure can reduce the shrinkage of a finished product.
UV Curing Behavior of Polydimethylsiloxane Toughened Acrylate
Ultraviolet (UV) curing characteristics of polydimethylsiloxane(PDMS) toughened acrylate was investigated by photo DSC. PDMS was introduced as a rubber toughening phase in the acrylate coating on plastic film to avoid the crack formation. It was found that the crack formation in acrylate coated thin film was disappeared by adding PDMS but PDMS interrupted UV curing of acrylate. The lowering of UV curing by PDMS could be minimized when PDMS having higher methylvinylsiloxane content in PDMS was mixed with acrylate due to the UV curing between methylvinylsiloxane and acrylate.
Surface Modification of Polymeric Surfaces Using Reactive Gas Technology
Traditional methods to activate surfaces include corona and plasma treatment, which have some drawbacks. This presentation describes a technology for modifying polymeric substrates, which has proven effective for improving the performance of existing products and for facilitating activation of “difficult to modify” materials such as PP and PE. The treatment involves using Inhance Technologies’ proprietary reactive gas atmosphere technology that creates permanent high surface energy. The treatment can be carried out on 3 dimensional as well as 2 dimensional structures. The treatment gives tenacious adhesion and allows use of a broad array of continuous phase systems including epoxies, polyester, polyurethane, concrete, water based coatings and others. The surface modification chemistry can be very rapid, often a few seconds, which enables processing to be done continuously and on-line.
Novel Melt Filtration Technology for Challenging Recyclate
The American market for recycled plastic offers both enormous economic potential and strategic challenges. Especially in light of the domestic shale oil boom, recyclers must find ways to maintain competitive advantage in the market. Tackling increasingly contaminated, wet and hard-to-process materials offers a path to this end. Co-rotating twin screw extruders are well suited for accepting plastic regrind of different shapes, bulk densities and contamination levels. Energy extensive drying steps after the washing process can be eliminated, when steam and moisture is removed in special venting barrels. In this paper, process experiences with a novel continuous melt filter are presented, which offers superior processing and flexibility for recyclers to capture untapped value. The functionality and processing potential of this filter in combination with the twin screw extruder is explained by using examples from the post- industrial recycling market, the automotive recycling effort and as well as the post-consumer recycling sources.
Investigating the Full-Face Joining of Polymer-Metal Hybrid Structures
Hybrid structures consisting of metal inserts and injection molded ribbing offer both a cost-efficient production technique and an excellent ratio of mechanical performance to weight. Thus, this technique has found its use a million times over for the fabrication of lightweight parts, especially in automotive applications. Currently, joining both families of materials is achieved by form-fit and frictional joints due to its easy process integration. This paper presents a new approach by joining both materials adhesively in the process of the In-Mold- Assembly and shows the lightweight potential to be additionally tapped.
Developing Flexible Packaging with Pilot Scale Equipment
Preparing package materials on a pilot scale production line allows validation of both materials (fit-for-use) and processes (fit-to-make). The process generates samples for a full array of testing including customer packaging-machine trials and shelf-life testing. This paper will discuss pilot scale test design especially the importance of establishing clear and limited objectives for validation, and available options for responding to reduced time-to-market expectations. Scalability from the pilot to production will be reviewed. Examples from the development of non-foil high barrier packaging from the US Soldier Science Center Development program for Meals Ready to Eat (MRE) will be cited. The recently completed SAM North America pilot lab for Flexible Films and laminations will demonstrate the added flexibility of the pilot scale production approach.
Optimizing the Co-Extrusion Process for Multi-Layer Line
Co-extrusion presents the processor with many distinct advantages in terms of flexibilities, product quality, and economics. On the other hand, a co-extrusion package will not solve all of a processor’s problems automatically. To ensure that the evolution to extrusion will be as simple as possible, it is essential that all aspects of the process are carefully considered, from initial specification of the line, through to the actual operation of equipment, package design, installation, operation, and process assistance utilizing process simulation software. These matters are discussed in the detail in the following paper.
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.
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