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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High speed thermal imaging of complex micromoulding flows
The thermal characteristics of the boundary between the polymer melt and mould tool are important considerations for injection moulding processes but are particularly relevant for microinjection moulding or thin walled processes where the high surface area to volume ratio and small product masses results in internal morphologies and resulting mechanical properties which can be highly influenced by the thermal field. In this paper we describe work to measure thermal fields and characterise the cooling behaviour of a micromoulding process using high speed thermal imaging techniques to better understand the thermal behaviour.
Silicone Elastomers - Clear as Glass Transparent Liquid Silicone Rubbers For Lighting Applications
For many years PC and PMMA were materials of choice for optical applications beside glass. These poly- meric materials have advantages such as weight reduction, increased freedom in design complexity, and better manufacturing economics due to lower energy consumption and less post processing when com- pared to glass. One has to also consider the tradeoffs when making a decision to use thermoplastics due to their less superior thermal, UV and chemical resistance against glass.A new alternative is now available with the "glass-clear" LSR7OOO silicone elastomer family from Mo- mentive Performance Materials. This new material combines the physical property benefits of silicones, ease & high productivity process advantage of liquid silicone rubbers (LSR) and an optical transparency of 95%. Since silicone polymers have an inorganic backbone, it offers better thermal and UV resistance when compared against thermoplastics.LED Lighting demands a combination of extreme material properties. For this application typically re- quires materials to withstand the harsh blue light radiation in combination with a maximum lamp temper- ature of up to 150?C for 100,000 hrs, which is the lifetime of a typical LED System. Due to its inorganic backbone, LSR7OOO offers superior performance in this extreme environment compared to other trans- parent organic plastics. LSR7OOO provides an outstanding thermal, UV, and blue light stability which makes this material an ideal candidate for the production of lenses for high power LEDs in the automotive and consumer lighting markets.Liquid Silicone Rubber Processing also brings various advantages. Due to its elastomeric properties, molded in stress and birefringence on finished parts are minimized. Material waste is reduced to a mini- mum through cold runner technology. Due to its low viscosity and processing conditions, LSRs are able to replicate parts with intricate details.This paper gives an overview of the special material properties of the ultra-transparent LSR7OOO and compares physical data to commercial optical thermoplastics. Application examples highlight present and future use of this innovative material. For many years PC and PMMA were materials of choice for optical applications beside glass. These poly- meric materials have advantages such as weight reduction, increased freedom in design complexity, and better manufacturing economics due to lower energy consumption and less post processing when com- pared to glass. One has to also consider the tradeoffs when making a decision to use thermoplastics due to their less superior thermal, UV and chemical resistance against glass. A new alternative is now available with the glass-clear" LSR7OOO silicone elastomer family from Mo- mentive Performance Materials. This paper gives an overview of the special material properties of the ultra-transparent LSR7OOO and compares physical data to commercial optical thermoplastics. Application examples highlight present and future use of this innovative material molded in stress and birefringence on finished parts are minimized. Material waste is reduced to a mini- mum through cold runner technology. Due to its low viscosity and processing conditions
Investigation of Crosslinking and Crystallization Behaviors of Polyethylene Blends
Crosslinking kinetics and its influence on the subsequent crystallization of polyethylene blends were investigated by rheological measurements and thermal analysis. Results indicate that addition of small amount of polyolefin elastomer (POE) in the HDPE matrix does not accelerate the crosslinking process and the final crosslinking degree of the blends is independent of the molecular weight of each component. Crosslinking can significantly retard the crystallization process and decrease the crystallinity due to the hindrance on chain folding caused by the formation of the network structure.
An Electro-active Actuator Made With Cellulose / Gamma Ferric Oxide / Polypyrrole
This paper reports a Method of fabricating electromechanical actuators for drug delivery. The actuators are fabricated from regenerated cellulose/ magnetic ferric oxide nanoparticles coated with polypyrrole. The actuators undergo a bending deformation when exposed to an electric field. In this paper, the properties of the actuator scaffolds are reported, including the magnitude of the displacements. The actuators can be operated in air at low voltages by consuming low electrical power. The surface and cross-sectional morphologies of the actuators were observed by SEM. The material synthesized in this study may have potential application in the development of electromechanical actuators.
Modification of PVC with bio-based PHA rubber. Part 2.
Blends of biobased polyhydroxyalkanoates (PHAs) with PVC have been developed and demonstrated very unique properties when added between 5 and 30 phr. These blends promise to improve both mechanical and environmental performance of PVC. The breakthrough is based on the miscibility of PHA and PVC resins and similar processing windows. Based on the miscibility and performance requirements, specific compositions of PHA copolymers were created to improve plasticization, impact and processing modification. In impact modification, PHA rubber copolymers outperform the best available MBS core/shell impact modifiers and do not compromise PVC transparency and UV stability. In plasticization, PHA copolymers perform as high molecular weight, readily dispersible plasticizers and enable formulation of compounds with low additive migration, low extractables, volatile loss and staining. As a processing aid, the metal adhering properties of PHA copolyesters promote homogeneous shear melting of PVC particles and prevent overheating and degradation. It will be shown that due to their multifunctional performance, the PHA modifiers could significantly simplify the formulation of PVC compounds and reduce the overall amount of required additives. The PHA rubber copolymers are commercially biosynthesized by fermentation technology from renewable resources. They satisfy requirements on sustainability and biodegradability.
Fabrication of TiO2/PU Superhydrophobic Film by Nanoparticle Assisted Cast Micromolding Process
Lotus-like surfaces have attracted great attentions in recent years for their wide applications in water repellency, anti-fog and self-cleaning. This paper introduced a novel process, nanoparticle assisted cast micromolding, to create polymer film with superhydrophobic surface. Briefly, waterborne polyurethane (WPU) sol and nano TiO2/WPU sol were each cast onto the featured surfaces of the PDMS stamps replicated from fresh lotus leaves. After being dried and peeled off from the stamps, PU and TiO2/WPU replica films were created simultaneously. To the former, only high hydrophobic property was observed with static water contact angle (WCA) at 142.5°. While to the later, superhydrophobic property was obtained with WCA more than 150° and slide angle less than 3°. Scanning electron microscopy (SEM) imaging showed that the PU replica film only had the micro-papillas and the TiO2/PU replica film not only had micro papillas but also had a large number of nano structures distributed on and between the micro-papillas. Such nano and micro hierarchical structures were very similar with those on the natural lotus leaf surface, thus was the main reason for causing superhydrophobic property. Although an elastic PDMS stamp from lotus leaf was used in herein process, hard molds may also be used in theory. This study supplied an alternative technique for large scale production of polymeric films.
Temperature and Specific Mechanical Energy Profiles on a Tri-Kneader
A tri-kneader was tested against a traditional reciprocating kneader (ko-kneader) using a proprietary pre-blend of rigid PVC. The specific mechanical energy (SME) consumed was lower on the tri-kneader than in the traditional kneader (36% decrease). It was concluded that temperature control was the dominant factor affecting SME consumption. A second trial was conducted to compare SME consumption on a tri-kneader against a twin screw extruder (TSE) utilizing a proprietary color master batch with special effects. The tri-kneader showed a decrease in discharge temperature (13°C lower) and SME (45% decrease). It was concluded that the reduction in SME was mainly due to a reduction in process length.
Evaluation of Destruction Mechanism on Quasi-Isotropic GFRP
Fiber-reinforced plastic tubes can be used as permanent formwork and external reinforcement for concrete columns. Failure of such columns is often accompanied by audible noise from cracking of concrete and shifting and settling of aggregates, snapping of the inner layers of the jacket, and ultimately fiber fracture. Since the state of the concrete core is not readily visible from the outside, nondestructive evaluation tools such as acoustic emission (AE) can help assess its structural integrity. In this research, we tried to investigate the applicability of AE technique to the quasi-isotropic GFRP materials, and to correlate the AE parameters to the state of stress in concrete. As a result, it was found that the Felicity ratio depends on the internal structure of GFRP. The effect is discussed on the basis of the results of the tensile test, AE measurement, and Felicity analysis.
PLA Thermoplastic Lignin Blends
In this paper, for the first time the PLA/TPL (Thermoplastic Lignin or Plasticized Lignin) blends were developed and investigated. The PLA/TPL blends were prepared by twin-screw extrusion. The lignin and plasticizers were mixed together in the first half of the extruder to complete the plasticization of lignin. Water was removed by devolatilization at mid-extruder and the PLA matrix was mixed with the water- free TPL in the latter portion of the extruder. The PLA/TPL blends comprised 20% and 33% TPL in the PLA matrix. The TPL phase comprised 36% plasticizers in the form of glycerol and sorbitol mixtures. Very fine dispersion of TPL in the PLA matrix was obtained with the particle size less than 1µm based on SEM observation. It was found that the viscosity of the PLA/TPL blends was dramatically increased by adding a small amount of epoxy-based chain extender (CE). The PLA/TPL blends are of great interest for industrial applications such as film-blowing and foaming.
Effect of Molding Conditions on the Weld Line Property of Injection Molded Jute/PP Composites
Jute fiber is of not only low density and good mechanical property but also natural and degradable property. On the other hand, recyclable Polypropylene (PP) was also good choice for environmental friendly material. Injection molding is one of the most important processes to manufacture plastic composites because it is of high quality products with low cost. However, weld lines are unavoidable when two separate melt fronts rejoin during injection molding. The presence of weld lines not only detracts from the surface quality but also significantly reduces the mechanical strength of injection- molded parts. Although it is not always easy to completely eliminate weld lines, the weld line strength could be improved through suitable adjustment of molding conditions such as melt temperature, mold temperature, hold pressure, injection speed, and so on. Therefore, in this paper the weld line property of injection molded jute/PP dumbbell shape specimen was investigated. Pultrusion technique was adopted to fabricate jute/PP long fiber pellets (LFT) and the re-compound pellets of LFT, i.e. RP was made to improve the fiber distribution. Then LFT, RP were used to mold dumbbell shape specimens with or without weld line. In particular, the influence of back pressure and holding pressure on weld line strength of injection molded jute/PP dumbbell shape specimens was discussed based on tensile test and SEM observation.
New method of characterizing the fatigue behavior of thin films for acoustic applications at high frequencies
In the present work a new method to characterize the fatigue behavior of polymer films, which are used as loudspeaker membranes, with thicknesses down do 5 ?m at application relevant frequencies is presented. Furthermore the anisotropic fatigue behavior of different films was studied. Stress controlled Wöhler tests were performed at a frequency of 100 Hz in uniaxial cyclic tension. The failure mode and crack growth kinetics were described via linear elastic fracture mechanics. An extruded film exhibited significant anisotropy with superior fracture toughness in machine direction. By contrast, a solvent cast film showed only neglectable anisotropy in the fatigue-experiments.
Recent Advancements in Transparent Lexan SLX Resins: Weatherability and Phsical Properties
A new family of transparent Lexan* SLX resins, based on resorcinol phthalate, has been developed that dramatically improve the cost/performance balance over existing resorcinol phthalate containing resins. Like polycarbonate, they have an excellent balance of clarity, toughness and good processability. Unlike PC, the ITR containing resins have dramatically improved weatherability as a result of a photogenerated UV absorber (UVA) on the surface of a part. The photo generated UVA has been found to suppress the photo induced degradation of the resin which would lead to the loss in optical properties (color, transmission and haze) and a loss in physical properties.
Thermoplastic Polyurethane/Polylactic Acid Tissue Scaffold fabricated by Twin Screw Extrusion and Microcellular Injection Molding
Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. They possess rigid and flexible mechanical properties. The TPU/PLA blend tissue scaffolds at different ratios were fabricated via twin screw extrusion and microcellular injection molding techniques (a. k. a. MuCell) for the first time. Multiple test methods were used in this study. Fourier transform infrared spectroscopy (FTIR) verified the presence of the two components in the blends. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between TPU and PLA. Scanning electron microscopy (SEM) images affirmed that the PLA was dispersed as spheres or islands inside the TPU matrix, and that the phase morphology further influenced the surface roughness of cells. The blends exhibited a wide range of mechanical properties that cover most human tissue requirements. It was found from DMA and viscosity tests that 25% PLA significantly reinforces the blends at low temperatures or deformation frequencies.
Plastic Composite Material of Bamboo and Bamboo Charcoal
The use of natural fiber reinforced composites has continuously increased during recent years due to their low density, low cost and environmental friendliness. The use of bamboo biomass plastic has been examined by various researchers because bamboo has a regenerative power, and is leading the bamboo reinforced composites as biomass resources. On the other hand, the bamboo charcoal has various functions, then the following effects can be expected: Good adsorption performance, removal effect for harmful gas and moisture adjustment capability. As current study, a preliminary investigation on the mechanical properties and morphologies of polypropylene (PP) reinforced by bamboo powder and bamboo charcoal were carried out. Additionally, the effect of sandwich structure of bamboo powder and bamboo charcoal on the composites has also been carried out.
Effects of Molecular Weight Changes on the Foaming Behavior of Thermoplastic Polyurethane (TPU) and its Acoustic Properties
This paper investigates the effects of molecular weight changes on the foaming behavior of thermoplastic polyurethane (TPU) and its acoustic properties. In order to vary the molecular weight of TPU, the additional melt extrusion processes are introduced and the foam samples are manufactured via injection foam molding technology. The effects of each additional extrusion process on the molecular weight changes are examined by analyzing heatcycle and rheological behaviors. In addition, the cellular morphologies and acoustic properties of injection foam molded samples are evaluated and their relationships with molecular weight changes are discussed. The foaming behaviors are varied significantly due to reduced molecular weights and different foam structures result in different acoustic performances. In general, the foamed samples from the processed TPU resin are able to achieve higher acoustic absorption coefficients.
Long-Wavelength Laser Welding of Clear Plastics Without Absorbers
The newest advancement in laser welding of plastics involves laser welding of non-pigmented plastic components with a wavelength above 1070 nm. Thermoplastics are partially absorbing in a range above 1500. When exposed to infrared energy within this wavelength range, the work pieces are heated through volumetric absorption and a weld can result. In this study, several commonly used thermoplastics, of varying thicknesses, were welded using a 1908 nm diode laser source. All thermoplastics included in the study were successfully welded. The capabilities of this approach were demonstrated with film and plaque samples.
A Device for Simulataneous In Situ Structuring and Measurement of Rheological Properties of Polymer Blends and Composites
A prototype In Situ Structuring Rheometer (ISSR) was developed to study the shear behavior of polymer blends and composites in tandem with forming material components into a variety of fine-scale structural types. The ISSR utilizes a regime of fluid mechanics known as chaotic advection which enables progressive structure development, whereby specific blend morphologies are derived in sequence from in situ structural transitions. The ISSR resembles a conventional parallel plate rheometer and as such can be incorporated into commercial rheometer instruments. The ISSR provides new means to explore interactions between material components at the micro- and nano-scales, validate theoretical rheology models, and characterize melt properties to support manufacturing processes. The ISSR design and results of initial trials are presented.
Sourcing Bioplastics from Plant-Based Wastes: Examples of Progress
Biobased plastic materials have captured much attention recently, but the raw materials for their building-blocks are typically food crops – not an ideal or sustainable approach. However, obscure biochemical processes are being used to transform organic wastes into useful compounds for polymers and plastics. This paper reviews some recent developments in researchers’ efforts toward exploiting wastes as raw materials, especially plantbased food and industrial wastes. The paper will also discuss the practical issues and commercial limitations of “upcycling” these waste materials into biobased plastics.
Thermo-physical and Optical Parameter Estimation for Pyrolysis Modeling of Fiberglass Reinforced Polymer Composites
To explore the potential use of modeling for the development of fiberglass reinforced polymers (FRPs) with good fire characteristics, parameter estimation based on comprehensive pyrolysis modeling of an FRP composite is conducted. Kinetic modeling is performed using data from TGA and DSC experiments. Different kinetic models are proposed and their effect on pyrolysis modeling is evaluated using a screening process that involves simulation of 1D FRP pyrolysis. This procedure shows that changes in simulation results (mass loss rate) are minor when different kinetic models are applied. Following this work, a sub-set of these kinetic models are used in a parameter estimation process to examine their effect on the estimated parameters. The results show that different kinetic models affect the successful completion of the estimation process. When completed successfully the estimation process demonstrates the possibility of applying numerical optimization to estimate model parameters that can be reproduced from independent standard measurements.
Predicting the Long-Term Ductile Failure of PE-100 Grades Based on Short-Term Testing
In this work, a method to predict long-term ductile failure using short-term testing is presented and validated for a high density polyethylene (PE100) pipe grade. Constant strain rate experiments, performed at different temperatures, are used to characterize the plastic flow kinetics. Combined with the hypothesis that failure occurs when a critical amount of plastic strain is surpassed, this enables prediction of the time-to-failure. We demonstrate that this method enables accurate long-term predictions of pressurized pipe certification tests (time-scale 1 year), based on an experimental procedure that takes approximately two weeks.
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