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.
In this work, a mechanistic fiber model is used to study the behavior of fibers as they move through the gate of an injection mold. The model represents fibers as chains of interconnected beam elements and includes effects such as fiber flexibility, interaction between fibers and fiber attrition. The ability to successfully injection mold a fiber reinforced part is affected by the gate design. Therefore, it is important to model flow through the gate in order to adequately study the filling and packing of the part. The simulations show how the deceleration of the melt as it leaves the gate and enters the mold cavity results in fiber buckling and damage.
Use of transparent plastics is commonly preferred over glass in clear housewares applications due to their resistance to breakage, lighter weight, and design flexibility. Eastman Tritan™ copolyester is an alternative material to polycarbonate, styrene acrylonitrile (SAN), modified styrenics, and acrylics, which are traditionally used in housewares applications. In materials selection, it is important to connect generic datasheet information for materials with performance of materials in real use conditions through fitness for use (FFU) testing. Clarity, scratch resistance, heat resistance, toughness, chemical resistance, and dishwasher durability are some of the major attributes that are commonly compared in FFU testing of housewares. This paper discusses the respective pros and cons of materials, and demonstrates the excellent balance of properties of Tritan™ for durable housewares applications.
Handheld electronic devices, including wireless phones and diagnostic devices, are used in hospital settings where they are repeatedly exposed to cleaning agents and disinfectants. Polycarbonate (PC) and PC blends are common engineering thermoplastics used for device enclosures/components. While these materials are generally tough, certain chemical environments can contribute to catastrophic brittle failure at relatively low stress levels. The purpose of this paper is to illustrate the susceptibility of PC to hospital disinfectant chemicals and provide a practical example of stress-cracking in the PC housing of a handheld medical device.
Polymers have a unique combination of properties, making them the material of choice for a wide range of applications in the market place. Research and development of polymer technology continues to expand the possible applications as well as the ability to create tailored solutions for specific needs. Ionizing radiation, especially from a highly-penetrating electron beam accelerator, is an effective and well-established tool used in the polymer industry to expand functionality, improve properties, and create custom-tailored solutions by the modification of polymers. There are two premier events in the world highlighting the latest research and development involving the irradiation of polymers: the International Meeting on Radiation Processing (IMRP) and the Ionizing Radiation and Polymers (IRaP) conference. This paper, based upon the most recent of these two conferences and other recent publications, will discuss how the use of polymers continues to expand through the use of electron beam processing and other forms of irradiation. Three areas of research and development will be highlighted: the expansion of mature technology into new arenas, the application of the technology to biopolymers, and additional novel applications which are being explored and largely still in their infancy.
The mechanical properties of two biomedical grades of polyetheretherketone (PEEK) from different manufacturers were compared with respect to degree of crystallinity. The polymer chemistry and structure of the two materials were verified using DSC, DMA, and FTIR. Modulus and strength were both showed to be proportional to the degree of crystallinity in annealed amorphous PEEK films ranging from 10 to 35%. Failure strain and toughness remained unaffected. Samples from PEEK-OPTIMA LT1 placards demonstrated a 22% higher modulus and 10% higher strength values compared to samples from Zeniva ZA-500 placards in strain-to-failure tests. The increase in mechanical properties was attributed to PEEK- OPTIMA LT1 having a higher degree of crystallinity. Finally, the degree of crystallinity was shown to vary between 27 and 36% within a spinal implant made from PEEK.
A micro-compounder using ultrasonic assisted technology has been developed and used for the dispersion of multi walled carbon nanotubes (CNTs) to produce polymer nanocomposites. This process is continuous and can be easily adapted to equipment that is currently being used commercially. The effects of compounding with and without ultrasound on torque, power consumption, rheological, morphological, mechanical and electrical properties in polyetheretherketone (PEEK) filled with 0-5 wt. % CNT were evaluated. Ultrasonically treated nanocomposites show increased viscosity with a slight improvement in mechanical properties. An electrical percolation of less than 1 wt. % was observed. Samples ultrasonically treated at 10 ?m showed a significant increase in viscosity due to improved dispersion at the molecular level. The incorporation of CNTs into PEEK showed up to a 15% increase in modulus with loadings up to 5 wt. % CNT and a significant decrease in electrical resistivity at CNT loading of 1 wt. %. The rheological percolation is observed to be between 2 and 5% and the electrical percolation is observed to be below 1 wt. % loading. Further investigation of the interaction between the CNTs and the matrix are in progress.
Cold gas plasma may be applied to medical and life science substrates for the permanent re-engineering of the molecular surface properties of polymers, elastomers, metals and ceramics to provide unique surfaces that do not affect the bulk properties of the material. Examples of applications include: amination, coating/ink adhesion, biocompatibility, non-fouling, or wettability to aqueous and oleo reagents. A plasma is an excited gas comprised of metastable molecular fragments that are able to polymerize or covalently graft to a surface. Methods of creating a plasmas vary from continuous wave to pulsed plasma; use of simple inert gases to complex monomers; or unique chamber designs allowing facile batch processing or treatment in-line.
PolyFusion, LLC has recently introduced an antimicrobial master batch for thermoplastics. The master batch is being marketed under the name of SafeTouch® and remains effective against microbes for the usable life of the plastic product. The primary antimicrobial utilized in the master batch is a patented silane antimicrobial trade named BIOSAFE HM 4100. SafeTouch®/ HM 4100 represents the “next generation” of antimicrobials for the plastics industry. The master batch is differentiated by its fast mode of action evaluated on the ASTM, E2149:10 dynamic contact protocol having a (1-hr) test timeline. By comparison, ion exchange and phenol based antimicrobials are tested on a (24-hr) test timeline via a sterile cover slip test protocol. Adding antimicrobials to thermoplastics is as much art as science. Knowledge of appropriate techniques, to have the antimicrobial available at the surface, is essential. PolyFusion has developed various protocols for designing SafeTouch master batches. Antimicrobial efficacy data from thermoplastic systems using these master batches will be discussed.
Effect of the two crystallization enhancement strategies, i.e. nucleation and plasticization, which are commonly used to promote polylactide (PLA) homocrystallization was investigated on the stereocomplex formation between poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA). The goal was to enhance the kinetics and yield of stereocomplex formation from the melt for future applications in PLA melt processing. Blends with 5% PDLA with nucleating agent and/or plasticizer were prepared via melt-blending and characterized by differential scanning calorimetry (DSC) technique. Results suggest that combination of nucleation and plasticization is very effective in simultaneous enhancement of stereocomplex formation and homocrystallization.
Molecular orientation is a polymer property directly affected by the method in which it was processed. Both amorphous and crystalline sections of a polymeric part can be oriented through the use of a specialized injection molding process known as Vibration-Assisted Injection Molding (VAIM). By changing the molding process parameters, different levels of molecular orientation can be achieved. Polymer samples with various levels of molecular orientation will present different mechanical and chemical properties. Biocompatible polymer parts containing tailored levels of molecular orientation may broaden the use of such substrates for tissue engineering applications. Some persuasive results obtained at the end of this study denoted that the modified molecular orientation could influence the degradation manner of PLA specimens. Based on this investigation, it appears that specimens with higher levels of molecular orientation have an enhanced tensile strength along the orientation direction and these samples are more resistant to hydrolysis, indicated by a slower degradation rate.
An analytical method for estimating the bulk melt temperature in the injection molding process by means of in-mold temperature sensors data has been validated. The method was evaluated for experimental data and data acquired with a computer simulation of the process. The simulation considered the heat flux and heat accumulation throughout the cycle in the mold. For the simulation, a full 3D model of the mold geometry was developed. Most trends correlated for both simulated and experimental data; however, the magnitude of the predictions varied due to the sensitivity of the analysis to the parameters.
Mold performance is measured by key factors including: cycle time, cavitation, efficiency, parts/hour, mold set-up time, and maintenance requirements. For parts like caps and closures these factors are critical to overall part costs. In this paper we will look at methods for improving mold performance by evaluating tooling for a closure. Cost savings will be evaluated by comparing unscrewing style tooling to collapsing cores. There will also be a review of recent advances in collapsing cores which have allowed for additional gains, including: efficient part ejection, faster conversion or replacement, and reduced set up time.
A newly developed technique allows production of pellets with a spherical shape and size in the micrometer-scale. This is achieved by extruding a polymer melt through a capillary and perturbing it with a hot air stream. Experimental measurements are used to model such process of micropelletization in dimensionless form. In this work, critical capillary numbers have been estimated and increments in pellet size are obtained as a function of process variables. This would contribute to avoid the necessity of simulation or experimental test of the process when predicting pellet size as a function of processing conditions.
Performing load distribution analyses on plastic gears allows one to predict the effects of gear tooth microgeometry on the noise and stress performance of the gear pair. This paper seeks to identify the “best” profile crown for the minimization of corner contact and transmission error for a 5:1 ratio spur gear pair. Following the microgeometry selection, a study of the effects of the temperature and tolerance stack-up on the performance is shown. When accounting for the tolerance and temperature effects, it is shown that there is a shift in contact towards the end of contact for the two worst case temperature situations and for one of the cases, transmission error remained unchanged but in the other extreme case transmission error increased, but still was under the original perfect involute gear set. It is interesting to note that because of the very fine pitch and the loading being very low because of the plastic gear capacity, the microgeometry corrections seem to be so small that they might be considered impossible to manufacture. This is one of the great quandaries facing the plastic gear designer who wishes to minimize the noise of plastic gears.
In this study, a known viscoelastic materials model was used to apply and validate to a typical shrink film history. Literature review of critical materials properties for a published viscoelastic model was investigated and used to design series of experiments to obtain essential materials parameters (E, ?, ?l, C, and ?) in support of the chosen model for PETG films. The materials parameters were successfully obtained and technical computing software (Mathematica) was used for the integration to calculate the shrinkage. The comparison of the predicted and experimental shrinkage agreed with each other and was shown in this work.
Biodegradable poly(lactic acid) (PLA) and poly(trimethylene terephthalate) (PTT) blend fibers were prepared in this study. PLA and PTT were blended in a twin screw extruder with varied contents of PTT 0-50 wt%.The PLA/PTT blend fibers were prepared by melt spinning technique. Thermal properties and crystallization behavior of PLA/PTT blends were investigated. PLA fiber was glossy and transparent while PTT fiber was opaque. The spinning of PLA/PTT blends fiber was difficult due to the difference in melting characteristic of PLA and PTT. However, the PLA/PTT blend fiber was successfully spun at PTT content of 10 wt% with the barrel temperature of 250 °C and would be suitable for textile application.
Polymers from renewable resources are beginning to compete with conventional fossil fuel derived materials as fossil resources become increasingly expensive and difficult to extract. The same lightweight, high-strength properties of petroleum-based polymers and composites are required for renewable materials, and a better understanding of processing properties will improve their prospects in the market. One route to widening the thermophysical property window of biobased polyester poly(butylene succinate) (PBS) is the incorporation of reinforcing fillers. In this work, PBS is melt-mixed with high-surface-area fumed silica to create nanocomposites. The surface of the silica nanofiller is chemically modified to explore the effects of surface functionality on filler dispersion and required mixing energy. Rheological and thermal measurements show that structural properties of the filler have a larger influence than surface modification. Comparison of blending techniques provides guidance for improved nanocomposite preparation. The demonstrated mechanical property improvements over neat polymer enable a broader range of applications for these novel renewable materials.
This study investigated the dielectric properties of foamed multi-walled carbon nanotube / polystyrene (MWCNT/PS) nanocomposites over the broadband frequency range. Different carbon nanotube concentrations were prepared from a 20 wt.% MWCNT / PS masterbatch using a melt-mixing technique in a twin-screw extruder. A chemical blowing agent was used to foam the nanocomposites in a micro injection molding machine. A foam relative density of approximately 0.55 – 0.65 was obtained for all the samples, regardless of the MWCNT loading. Compression molding was applied to fabricate unfoamed nanocomposites for comparison purposes. Specimens were characterized by applying direct current (DC) and alternative current (AC) electrical conductivity tests and using scanning electron microscopy and dielectric spectroscopy tests. The DC electrical conductivity tests showed a large difference between the foamed and compression molded nanocomposites. The percolation threshold of the foamed nanocomposites was observed to be much higher than that of the compression molded composites. The AC conductivity of the nanocomposites showed that this material property is frequency dependent in the insulative region and that it is almost independent from frequency in the conductive region. The dielectric spectroscopy showed a higher dielectric permittivity for compression molded composites, due to the higher probability of MWCNTs neighboring each other. Since chemical foaming deteriorated the formation of a conductive network, a lower dielectric loss was observed for the foamed nanocomposites. The results of this study showed that chemical foaming of nanocomposites broadened the insulator-conductor transition, which decreases the risk of manipulating conductive polymer composites (CPCs). Furthermore, the dissipation factor decreased with the foaming of nanocomposites. Chemically foamed MWCNT/PS nanocomposites show good potential for use in charge-storage applications.
In this research, the adsorptive properties of L-Menthol, the moisture vapor transmission rate (MVTR), and the mechanical properties of poly (ethyleneterephthalate) (PET), polypropylene (PP), and their blends, fabricated by injection molding targeted the container for solutions, which containing lipophilic chemical such as L-Menthol were evaluated. The result shows that, if the content of PP is more than 50%, the MVTR can meet the global acceptance criteria. On the other hand, When the content of PET/PP=5/5, the tensile properties were lowered (This is negative), and when the ratio of PET/PP=3/7, the anti-adsorptive properties of L-Menthol was lowered (This is negative).
Biobased and biodegradable ternary blends from poly (lactic acid) (PLA), poly(3-hydroxybutyrate-co- hydroxy-valerate) (PHBV), and poly(propylene carbonate) (PPC) were melt-compounded using a K-mixer and fabricated using an injection molding machine. The miscibility, degree of crystallinity, thermal stability, and mechanical properties were investigated. The blends were observed to be immiscible. PPC provided greater thermal stability in the blends compared to PHBV. The toughness and strain-at-break of the ternary blends were far superior to that of the binary blends due to the synergistic effect of the dispersed components. The stiffness and strength of the blends were consistent with those of the PLA matrix. The existing micromechanical models fit well for stiffness but under-estimated the tensile strength. As such, a new empirical model was developed that took into consideration the flexibility that exists between the immiscible blends.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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