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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A Study on the Mechanical Properties of Recycling PC/ABS Blends Produced by Vent-Type Injection Molding
The mechanical properties of recycling PC/ABS blends produced by three kinds of molding conditions were discussed, including such parameters such as the cylinder temperature and the type of injection molding processes. Mechanical properties and the degradation rate with the increase of recycling times were investigated. The comparison of different cylinder temperature produced by vent-type injection molding was conducted, also the research between cent-type injection molding and non-vent-type injection molding, based on the detailed SEM observation on the fracture surfaces after Izod impact test. It can be found that, with the increase of recycling times, the material produced by vent-type injection molding machine demonstrated higher mechanical properties and lower degradation rate in mechanical properties than non-vent-type injection molding machine.
Research on Mechanical Coupling Strength and Coupling Design of the ABS Injection Molding
The ABS resin was widely used in automobiles, electric products, household appliances, building materials and household goods due to being inexpensive. Components which could be easily replaced were welcomed in structural design, as well. In the past, there had been much research on reinforced fiber plastics, but seldom on ABS resin. In this paper ABS resin specimens with an open hole were used to be tested and evaluated. The test specimens were fixed with both screws and rivet pin, which had the same diameter as the open hole. In this experiment, the specimens were placed between two flat steel plates and hand tight with screw (pitch 1mm and depth 0.7mm) or rivet pin. The load-displacement curves were recorded and analyzed, with the failure mode of the fracture section observed. By comparing the joint properties of ABS specimens on both cases including screw and rivet pin, it was obvious that screw had an advantage over rivet pin. In addition, the gate position relative to the flow direction had an influence. This experiment result was useful to shorten the design time, reduce costs and enhance the reliability of the products.
Fabrication of Glass mat Thermoplastic composite by Needling Punching Process
As well known, non-woven materials, because of simple preparation Process and wide range of applications, attract more and more attention. Needle punch process is widely used in textile area and expresses excellent performance. The introduced thickness-direction fibers via needle punched process play an important role to reinforce the composite in thickness which can minimizes delaminating problems. In this research, short glass fiber mat and plastic fabric produced by PP were used to fabricate thermoplastic composite through hot press process. The glass mat and thermoplastic mat were punched before hot pressing. This research mainly includes two parts, that is, effect of composites in different molding temperature on tensile properties, and the influence of composites in different needling density on tensile properties. Finally, cross sectional observations of molded sample were carried out using a scanning electron microscope (SEM), and the fracture characteristics were evaluated.
Critical Parameters of Generating PMMA Nanocellular Foam
In this study, Poly(methyl methacrylate) (PMMA) nano-cellular foams were successfully manufactured using two-step solid state foaming. PMMA of three different molecular weights was saturated in CO2 at 2000 psi (13.78MPa) and at different temperatures and the samples were subsequently foamed in a hot medium.
The results show that although the CO2 solubilities in PMMA of different molecular weights are similar, the morphology of the PMMA foams was very different. Nanofoams with a cell size of about 30-40 nm, and cell density of 1016cells / cm3 were successfully prepared using high molecular weight PMMA. The lowest relative density of the foam is around 0.25. However, PMMA of medium and low molecular weight could not generate nanocellular foams under the same processing conditions. The results first report that viscosity is one of the critical issues that affects the preparation of PMMA nanofoam.
Multi-Layer Rotational Molding of PE-PA Utilizing a Mulitphase Interlayer to Generate Mechanical Adhesion
Rotational molding is a plastic processing method for the production of seamless hollow bodies. Polyethylene is the by far most commonly used polymer in this process. Building up multi-layer parts containing a PE layer, is limited to few material combinations due to missing specific adhesion of PE to most other polymers. In this work, the possibility to produce multi-layer parts out of supposedly incompatible PE and Polyamide 12 is investigated. The adhesion between the layers was accomplished by mechanical adhesion within a multiphase interlayer. The peel strength was measured as a function of different processing parameters and layer setups. Additionally, the fracture behavior was characterized optically. Overall a significant increase of the peel strength was observed. The major influencing factors on the bonding strength were detected and characterized.
Development of a Predictive Power Law Relationship for Concentrated Slurries, Part 2: Experiment and Processing Implications
It is well established that the addition of solid particles into polymers can increase the melt viscosity significantly by perturbing the flow field and through particle-particle interactions or particle network formation [1-3]. Highly-filled polymer compounds can present processing challenges, including high screw shaft torque, energy consumption, pressure and melt temperature. This paper describes an evaluation of the effects of filler concentration on melt processing. The experimental results using a batch mixer are linked to the theoretical treatment of the rheology as a particulate percolating system with power-law behavior . The implications of the increase in viscosity with filler concentration on polymer processing will be discussed from a practical engineering perspective.
Rheology as a Tool to Evaluate Polymer/Active Pharmaceutical Ingredient (API) Solid Dispersions
Despite significant advances have been achieved in applying amorphous solid dispersion to enhance bioavailability of poorly soluble active pharmaceutical ingredients (APIs), there remain challenges in characterizing the microstructures of solid dispersions and correlating their performance with microstructures. This study focused on utilizing rheology as a tool to investigate and evaluate several model polymer/API solid dispersions prepared by various techniques with different mixing capabilities. Rheological responses of different model solid dispersions displayed a strong correlation between microstructures and viscoelastic properties. For the currently studied system, storage modulus and viscosities versus frequency of different solid dispersions indicated that the incorporation of API imparted a plasticizing effect to the polymer matrix. In comparison, crystalline/aggregated forms of the API exhibited a more elastic response than its amorphous/dispersed counterparts. In addition, a temperature ramp interrogation of a physical mixture of polymer and API captured a critical temperature, at which a transition in slope observed in the damping factor was attributed to the dissolution of crystalline API into the polymer.
Rheology Optimized Processing Temperature for Preparation of Amorphous Solid Dispersions via Hot Melt Extrusion (HME)
The production of amorphous solid dispersions via hot melt extrusion (HME) relies on elevated temperature, applied mechanical force and prolonged residence time, which can result in potential degradation and decomposition of thermally-sensitive components. In this study, the rheological properties of a physical mixture of polymer/active pharmaceutical ingredient (API) were utilized to guide HME processing temperature. A critical temperature, which is substantially lower (~13°C) than the melting point of crystalline API, was captured during a temperature ramp examination and regarded as the critical point at which the API molecularly dissolves into the polymer. After identification, solid dispersions were prepared by HME processing below, on, or above the recognized critical temperature and characterized by scanning electron microscopy, hot stage microscopy, Xray diffraction, differential scanning calorimetry and rheology. Physicochemical properties of resultant solid dispersions indicated that the obtained critical temperature is sufficient for the polymer/API system to reach a molecular-level mixing, manifested by the transparent and smooth appearance of extrudates, absence of API crystalline diffraction and melting peaks, and dramatically decreased complex viscosity. Once the critical temperature is achieved, further raising temperature only results in limited improvement of the dispersion, reflected by slightly reduced storage modulus and complex viscosity.
A Critical Review of a New Joint Test Proposed in NCHRP Report 190
Pipe joint performance is a critical factor in the overall pipe system success. Design of joints is more complex than the design of the pipe wall. There are many different joint designs manufactured and marketed by the pipe industry for non-pressure pipe designs. The recent National Cooperative Research Program (NCHRP) project report 190 attempts to address the structural performance, largely based on shear failure at the joint. This project did a very good job of analyzing the shear and rotation stresses for concrete, corrugated steel, PVC, and HDPE on a limited number of joints. There are practical issues with the recommended test. This paper focuses only on the thermoplastic pipe designs.
Bonding of Plastics
Many types of polymers are not weldable. For example, thermoset polymers cannot be welded. While thermoplastic polymers are considered weldable as a class, most combinations of dissimilar plastics cannot be welded. Even plastics within the same generic grouping may not weld easily because of high crystallinity or high melting temperature, widely differing melt flow indices, or high melt viscosity.
In this presentation, the basics of adhesive bonding of plastics will be given. This will serve as review for some and introduction for others. General topics include surface preparations and primers, joint design, selection of adhesives, and some specific ideas on bonding of difficult materials such as fluoropolymers and elastomers.
Study of Ketoprofen’S Dissolution in Polyethylene Oxide Formulations Prepared by Hot Melt Extrusion
Solubility parameters have been used as an approach to predict active pharmaceutical ingredients solubility in a polymeric excipient. The solubility is important because it dictates the processing window for hot melt extrusion and the stability of the formulation during storage. Nevertheless, it is challenging and complicated to predict the solubility and there is very few published studies in the field. In this study Film Casting Technique, Differential Scanning Calorimetry, Thermal Gravimetric Analysis, and Hot Melt Extrusion process were used to study and analyze the solubility of ketoprofen in polyethylene oxide (Polyox™ N10). The outcomes from the different method and techniques implemented were consistent and the best results were obtained with the maximum concentration of ketoprofen. The suggested processing temperature was 70°C and 70 rpm for the rotor rotation speed. The stability of the samples were monitored by two months. The methodology used in this study can be applied to analyze and investigate other drug-polymer pairs.
Product Quality Control for Single Screw Extrusion Process
As a major polymer processing technique, single screw polymer extrusion is a continuous process, during which material properties, machine variables, and process variables interact with each other to determine the final product quality. In order to achieve the desired product quality, the industry has been focused primarily on the control of critical process variables such as melt pressure and barrel temperatures. Recently, increasingly stringent customer demand on product quality has forced the machine maker to put more effort on the control performance. This paper first defines the extrusion product quality into two categories: precision and accuracy. The extrusion product precision control can be achieved by good process variables control, while the quality accuracy is a joint effect of the machine variable and process variables. The characteristic of the extrusion product quality shows as multivariable, non-linear, large time delay, hence advanced control algorithm must be employed in the product quality control. The control scheme is implemented experimentally via a self-developed controller on an industrial pilot-scale single screw extrusion process. Some representative results are presented to highlight the advantages and limitations of the control strategy.
Development of Advanced Microlayer Coextruded Films for Optical and Packaging Applications
Advanced optical and packaging films were developed by using microlayer coextrusion process technology with improved flow design and processing control. Combinations of layers and biaxial stretching provided enhanced optical properties. Films with broad band and wavelength-selective reflection were developed. The relationships of layer arrangement and processing control to properties were discussed. The high rate processes led to enhanced iridescent and optical filtering products for decorative packaging, energy control and consumer applications. The layered coextrusion process helped enable films and sheets with improved properties beneficial for packaging and consumer applications.
Development of a Flexible Polymer Joining Center Capable of Performing Multiple Joining Processes Using Different Methods in a Single Cycle
Goal of this research is the implementation of a flexible polymer joining center as a prototype machine integrating different friction welding methods. This prototype joining cell combines (a) flexibility by being capable of performing joining processes in any order in a single flow with (b) modularity by integrating unified interfaces for exchanging joining modules, and (c) scalability by offering a wide range of setups for smaller to larger work pieces. Corresponding interfaces to up- and downstream processes enable implementation in fully automated environments.
This paper will give a brief overview of the introduced technology and its current status, and present results from first welding experiments with non-reinforced PP and 30% glass fiber reinforced PA 66, mainly investigating reproducibility of welding results, and give an indication of overall welding quality potential.
Influence of Filler Dispersion on Electrical and Rheological Properties of Pc/San Blends with Graphite Nanoplates or Expanded Graphite
The effect of Graphite Nanoplates (GnPs) and Expanded Graphite (EG) on electrical and rheological properties was investigated in co-continuous melt-mixed polycarbonate (PC) /poly(styrene-acrylonitrile) = 60/40 wt% prepared using micro-compounder in two steps. Mixing conditions in premixing the fillers into PC were varied. Similar to carbon nanotubes (CNTs), GnPs and EG tend to localize in PC. Improved filler dispersion for samples exposed to higher mixing energy in the premixing step resulted in larger increase of complex viscosity and storage modulus. However, electrical resistivity was lower in samples which experienced lower mixing energy. Comparing EG and GnP, the effects are quite similar. EG showed a slightly better electrical performance.
Increased Throughputs in Blown Film Extrusion by Using a Contact Cooling Sleeve
One of the most important requirements for an efficient blown film extrusion process is the cooling of the film bubble. Conventional blown film lines use air rings to cool the film bubble. A new approach to enhance the cooling power is the use of an additional contact cooling sleeve that is placed on top of the die and which cools the melt via conduction.
The influences of the use of the contact cooling sleeve on the blown film process and the resulting film properties were tested. In order to do so, process settings were varied and the mechanical and optical film properties, as well as the maximum throughput of the blown film line have been determined. These trials showed that the mechanical film properties are not significantly influenced by the use of a contact cooling sleeve. For the optical film properties, the transmission is slightly decreased while the haze of the films is increased by about 10 % absolute. With the use of a contact cooling sleeve, it is possible to increase the throughput of the blown film line especially for smaller blow-up ratios. A simulation of the cooling process of the melt within the cooling sleeve has been performed as a first step to be able to dimension cooling sleeves for different sizes of blown film lines and process conditions.
Improvement of the Extrusion Foaming Properties of Externally Plasticized Cellulose Acetate by Reactive Melt Mixing Using a Multifunctional Reactive Oligomer
Externally plasticized cellulose acetate was modified by reactive melt mixing with a multi-functional oligomer (chain extender). The modified compound was characterized in terms of molecular properties and viscosity. The reactive modification was applied in an extrusion foaming process using 1,3,3,3-tetra-fluoropropene (HFO-1234ze) as blowing agent. The reactive modification in the foam extrusion process can be used to affect the rheology and thereby foaming properties of the cellulose acetate compound to optimize the cell morphology of the resulting foam sheets or boards.
Cycle Time Reduction by Water Spray Cooling in Thermoforming
The cycle time of automated multi-station thermoforming machines is limited by the cooling time. Optimizations of heat dissipation in negative thermoforming are especially focused on the mold-side cooling. However, cooling the inner, non-mold-contact side of formed part also provides potential for increasing the total cooling rate. The injection of water spray on the non-mold-contact side during the forming step is a promising approach to reduce the cooling time in thermoforming due to better heat transfer properties or the evaporation potential. In this paper the influence of an internal water spray cooling on the deforming temperature of thermoformed cups is examined.
During water spray cooling a conflict of aims results between the maximum cooling effect and a water-residuefree cup. The injected volume of water spray significantly affects both the deforming temperature of the formed cup and the water residue. By optimizing the process a maximum injection volume of 6 ml water can be achieved for the examined 400 ml large cup with negligible residual water containing after deforming in the molded part. The results show that already minimal wetting of the partsurface results in effective cooling. To ensure negligible amount of residual water, a superposition of the water spray droplets should be avoided. Otherwise larger water droplets are created, which can not be removed by evaporation or an additional blowing process step. By using water spray, the cooling can be accelerated up to 6 K/s for the cup demonstrator. Thus, the application of water spray cooling reduces the cycle time of multistation thermoforming machines.
Highspeed Tensile Testing of Polymer Materials Considering Force-Oscillations and its Origin
The force-oscillation phenomenon describes a superimposition of force measurements with an oscillating signal which can be monitored in tensile impact testing. These oscillations become predominant with an increase of the haul-off velocity which prohibits a resilient evaluation of the measured force characteristics. Hence force-oscillations present a limiting factor to the maximum haul-off velocities in tensile impact testing and therefore a limitation to material data measurement for crash analysis in general.
The presented research looks at the phenomenon of force-oscillations on viscoelastic materials and gives an elementary investigation on its origin. Furthermore a new approach is outlined to overcome the existing limitations to tensile impact testing which enables a material data measurement basically independent of the considered haul-off velocity.
Atomized Spray as a Process Fluid for Fluid-Assisted Injection Molding
Gas- and water-assisted injection molding (GAIM, WAIM) can be used to produce hollow plastics parts. Previous research showed that the thermal properties of gas and water have a large influence on part properties and the formation of part defects. A new approach is to use atomized spray to adjust the thermal properties of the process fluid to the needs of the process and used material. The study will determine the effect of water percentage on the cooling effect of the atomized spray and the resulting part properties. High speed imaging will show effects of water coagulation on the part cooling.
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