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Thermoformed polyethylene terephthalate (PET) produce trays (clamshells) produced by a large retail supplier using virgin resin were compared to PET clamshells containing 30, 70, or 100% recycled-PET (RPET). Comparisons were made of functional groups, ultravioletvisible (UV-Vis) light absorption, and thermal properties. An increase in the crystallization temperature was observed as RPET increased when compared to virgin PET. This suggests that the crystallization temperature (Tc) may be used as a quantitative indicator for determining the amount of RPET in a plastic composite.
In today's competitive world, speed to the global market plays a major role in overall success of a conversion program. When it comes to metal to plastic conversion, most designers still think in terms of direct part-for-part replacement which adds both cost and time to the overall development cycle. In order to expedite the conversion process, there have been significant developments in polymer science, plastic processing and simulation technologies. The new range of HPEP compounds offers the best price-performance options, whereas the latest wave of simulation technology provides a reliable method to predict part performance. This paper talks explains the importance of understanding material properties and the re-designing for plastics to reduce product development cycle time. It also discusses the new development in simulation technology, commonly known as computer aided engineering (CAE) integration.
Injection molding although widely extended as one of the main replication technologies has shown important limitations when applied to the manufacture of plastic parts in the micro and mini scale. The present work describes a new moulding process based on the fusion ofthat has been thermoplastics materials via ultrasounds developed in the Sonoplast European project. First experimental achievements led to an innovative concept of mould and ultrasound moulding machine for the production of plastic parts (micro and mini). In addition the molding process management is simplified and directed by few machine parameters differing from conventional injection molding. The ultrasound molding process is extremely fast and with reduced filling pressures achieves a very good reproduction of the mould micro details. Besides it has been possible to obtain reductions about 50% on sprue volumes (around 0,16 g of plastic per shot) comparing with a conventional microinjection machine. Moreover, process energy consumption and power requirements are between 500 and 1200J and 200 and 500W, respectively. Finally, rheological analysis showed that no noticeable degradation process occurred after processing; equally, tensile testing gave better mechanical performance retention, comparing with traditional microinjection processes.
This paper examines the effect that blending two biodegradable polymers has on the thermal properties and morphology of the resultant foams blown with carbon dioxide (CO2). Polylactic acid (PLA) Polyhydroxybutyrate-co-valerate (PHBV) and blends of both were foamed and characterized in terms of thermal characteristics relative density cell size and foam morphology. The results indicate that although PLA and PHBV are immiscible the presence of small quantities of PHBV could lead to low density foams with finer more uniform cells.
A new commercial iron-based oxygen scavenging montmorillonite clay (MMT-Fe), was analyzed for its oxygen scavenging capacity. In a subsequent step, it was incorporated by solution casting into PLA to obtain a brown colored nanocomposite sheet with significant oxygen scavenging properties. Since PLA is known to exhibit shortages in barrier properties to gases, which conventional existing nanoclay formulations cannot overcome, the potential of combining the passive barrier properties of nanoclays with a novel functionalization capable of scavenge oxygen from the packaging headspace shows strong potential in high barrier packaging applications of oxygen sensitive products.
Plug-assist thermoforming is a well known technique in polymer processing due to its interesting features. The dynamic value of driving-force for the stretching process is determined based on equilibrium equation. This amount of force is required for applying to a plug in order to stretch a sheet. It is used for calculation of the required theoretical work, and power of a plug-assist thermoforming process. By using a non-linear viscoelastic rheological model in the proposed mathematical model, its validity was examined by performing experimental tests on ABS sheets.
PLA nanobiocomposite films containing cellulose nanowhiskers (CNW) were obtained by solution casting. The cellulose nanowhiskers, prepared by acid hydrolysis of microfibers of highly alpha purified cellulose, consisted of nanofibers of typically 60 to 160 nm in length and 10 to 20 nm in thickness. The nanocomposites were prepared by incorporating 1, 2, 3 and 5 wt.-% of the CNW into the PLA matrix. The morphology and mass transport properties of the films were investigated by SEM, TEM, AFM, optical microscopy, OTR and WVTR.
Melt compounded polymer blends such as PP/HDPE blends from post consumer waste have often been reported to exhibit poor mechanical properties. This work reports on the potential improvement in performance of PP/HDPE blends using polypropylene copolymers as compatibilizers. The properties of the PP/HDPE blends in general progressively varied from that of 100% HDPE to 100% PP. Analysis showed some improvements in mechanical performance of the blends with the addition of PP copolymers, but DMTA results suggest no improvement in compatibility.
The contact between solid polypropylene (PP) and AISI P20 steel with 38 HRC was studied for several average roughness of the steelƒ??s surface. An instrumented pin-on-disk tribometer was used to measure the friction force during contact. The conditions used allow approaching to limited studied PP ƒ?? AISI P20 steel tribosystem. A high influence of adhesive wear was observed and related to high local temperatures in the PP surface. The aim of this research was to determine the contact characteristics between solid PP and AISI P20 steel during dry sliding in a pin-on-disk system. This experimental study brings valuable results about the interaction between surfaces types of contact and friction and wear phenomena.
The contact between solid polypropylene (PP) and AISI P20 steel with 38 HRC was studied for several average roughness of the steel’s surface. An instrumented pin-on-disk tribometer was used to measure the friction force during contact. The conditions used allow approaching to limited studied PP – AISI P20 steel tribosystem. A high influence of adhesive wear was observed and related to high local temperatures in the PP surface. The aim of this research was to determine the contact characteristics between solid PP and AISI P20 steel during dry sliding in a pin-on-disk system. This experimental study brings valuable results about the interaction between surfaces, types of contact and friction and wear phenomena.
The dynamic and dielectric relaxations of of maleic anhydride grafted polypropylene (PPgMA) and its clay filled nanocomposites with different degree of clay exfoliation have been investigated. Fully and partially exfoliated samples were prepared through powered sonication and melt blend respectively. Ourresults indicated that both mechanical and relaxations can be identified with dynamic mechnaical analysis. Only a single relaxation process due to interfacial polarization was observed in broadband dielectric measurements. Dielectric dispersion parameters including dielectric strength and peak relaxation frequency were identified and appeared sensitive to the degree of clay exfoliation.
It is well-documented that plastics surface modification techniques can greatly improve the acceptance of a wide variety of coatings, adhesives and inks for improved decoration, painting and adhesive assembly. By increasing the hydrophilic characteristics and surface-free energy of plastics, bond strengths can be improved dramatically. It is theorized that interlayer adhesion between decorating and assembly formulations can also be improved by applying atmospheric plasma surface modification techniques. This study examines experimental data which relate correlations between surface modification and interlayer adhesions of inks, coatings and adhesives.
The continued evolution of non-contact scanning methods has led to the development of highly effective tools for investigative metrology. Structured white light scanning technologies in particular can now generate a wealth of data for identifying and quantifying nearly all aspects of part geometry. When applied to the development process for plastic parts and products, such tools can be invaluable in evaluating design, material, tooling, and process related issues. This paper recounts the implementation of structured light scanning, automation, and data processes at Motorola, and reviews its impact on a variety of applications.
In this study, long fiber pellets were used to make hemp/glass hybrid reinforced polypropylene (PP) composites by injection molding process. The mechanical property and the fracture behavior of both welded and un-welded dumbbell specimens were investigated in tensile test. It is found that in hybrid composites, the optimum hybrid ratio exists for both high tensile modulus and tensile strength. The interface property between fibers and PP were discussed based on the observation and weld strength. Last, rule of mixture was used to calculate the practical modules and strength of both hemp and glass fiber in injection molded composites from the monotonic specimens. Then the calculated results were applied again into rule of mixture for hybrid composite which involved both glass and hemp fiber. It is found that the prediction results are much closed to the experimental data.
Molding processes typically utilize a velocity controlled filling stage followed by a pressure controlled packing stage. The short term and long term effectiveness of seven different switchover methods are considered including: 1) ram position 2) injection time 3) machine pressure 4) nozzle pressure 5) runner pressure near the sprue 6) cavity pressure near the gate and 7) cavity temperature at the end of flow. The results indicated that the machine controlled switchover methods (ram position injection time and machine pressure) had a lower short term variation in the quality of the molded parts but the other switchover methods were more robust with respect to rejecting long term process variation.
Molding processes typically utilize a velocity controlled filling stage followed by a pressure controlled packing stage. The short term and long term effectiveness of seven different switchover methods are considered, including: 1) ram position, 2) injection time, 3) machine pressure, 4) nozzle pressure, 5) runner pressure near the sprue, 6) cavity pressure near the gate, and 7) cavity temperature at the end of flow. The results indicated that the machine controlled switchover methods (ram position, injection time, and machine pressure) had a lower short term variation in the quality of the molded parts, but the other switchover methods were more robust with respect to rejecting long term process variation.
Thermoplastic olefin elastomers (TPO)/montmorillonite (MMT) nanocomposites prepared by kneader and melt compounding methods were used in this study. The organoclay TPO nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content and preparation methods on the mechanical/thermal properties was investigated. The results show that the mechanical properties increase as the clay content increased for both the kneader and melt compounding processes. The foaming by kneader had better cell density than that of melt compounding, and cell size decreased as the clay loading increased. The addition of MMT also improved the thermal stability of the TPO/clay nanocomposites. The XRD results show that the nanocomposites having an intercalated layered structure.
In-mold forming (IMF) is a new injection molding technique to produce high-performance light-weight parts. Unlike the conventional process the novel molding technology is particularly suitable for mass production because its cycle times are short cost-effective and efficient. In this process a pre-heated fiber-reinforced thermoplastic sheet is formed in the injection molding machine followed by instantaneous overmolding thus forming short glass fiber reinforced thermoplastic ribs to reinforce the structure. To show the manufacturing procedure as well as the new molding devices required the system was implemented for the example of a steering column connection.
In-mold forming (IMF) is a new injection molding technique to produce high-performance light-weight parts.Unlike the conventional process, the novel molding technology is particularly suitable for mass production, because its cycle times are short, cost-effective and efficient.In this process, a pre-heated fiber-reinforced thermoplastic sheet is formed in the injection molding machine, followed by instantaneous overmolding, thus forming short glass fiber reinforced thermoplastic ribs to reinforce the structure. To show the manufacturing procedure as well as the new molding devices required, the system was implemented for the example of a steering column connection.
Kneader reactors are used for combined unitary processing in the polymer industry for devolatilization, compounding or polymerization. In the past, mass transport prediction for devolatilization operations in kneader reactors did not match experimental results, when diffusion was assumed as sole driving force. It was detected that there is an additional concentration and temperature dependent driving force that triggers enhanced transport at finite solvent concentrations by orders of magnitude. The author suggests that the underlying root cause is likely micro bubble formation within the polymer melt. An attempt to model this additional mass transport mechanism is presented.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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