SPE Library

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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Conference Proceedings

PLA melt crystallization and stereocomplex formation enhancement by means of nucleation and plasticization

Sajjad Saeidlou, Michel A. Huneault, Hongbo Li, Chul B. Park, May 2013

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.

An Investigation of Vibration-Assisted Injection Molding Manufactured Polymer Material and The Effect of Molecular Orientation on Biodegradation Activity

Qi Li, John W. Rodgers, John P. Coulter, May 2013

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.

Validation of an Analytical Method to Estimate the Bulk Melt Temperature from In-Mold Temperature Data

Gabriel A. Mendible, Stephen Johnston, May 2013

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.

Improving Mold Efficiency through Optimization of Collapsing Core Technology

Alan Hickok, May 2013

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 Dimensional Analysis of the Micropelletization Process Using Rayleigh Distrubances

William Aquite, Tim Osswald, Brett Kelly, Emily Burris, May 2013

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.

A procedure for evaluating the effect of microgeometry modifications on mixed material gears operating under extreme conditions of tolerance and temperature

Donald Houser, May 2013

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.

Understanding of Shrink Films through Viscoelastic Behavior of Polymer Films

Chieh-wen Chen, Hoang Pham, Andrew J. Poslinski, May 2013

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.

Thermal and Crystallization Behavior of Poly(Lactic Acid) and Poly(Trimethylene Terephthalate) Blend Fibers

Sirada Padee, Jessada Wong On, Teerapong Chaichalermwong, Supaphorn Thumsorn, Prayoon Surin, Chaiyaprek Apawet, Narin Kaabbuathong, Narongchai O-Charoen, Natee Srisawat, May 2013

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.

The Role of Surface Interactions in Renewable Poly(Butylene Succinate)-Silica Nanocomposites

Margaret Sobkowicz, Xun Chen, JeongIn Gug, May 2013

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.

Broadband Dielectric Spectroscopy of Carbon Nanotube Filled Polystyrene Foamed Nanocomposites

Mehdi Mahmoodi, Simon Park, Mohammad Arjmand, Uttandaraman Sundararaj, May 2013

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.

Performance Evaluation and Morphology Observation of PET/PP Blends in Injection Molding

Tadashi Otsuka, May 2013

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: Investigation of Properties via Experimental and Theoretical Routes

Srikanth Pilla, Lih-Sheng Turng, May 2013

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.

Heat Seal Characteristic of Environmental Friendly Films From Thermoplastic Rice Starch Filled Poly(Lactic Acid)

Supaphorn Thumsorn, Kazushi Yamada, Sommai Pivsa-Art, Ken Miyata, Hiroyuki Hamada, May 2013

An environmental friendly 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/TPS blend films were heat sealed by a heat seal tester at a heat bar temperature of 90 and 100 °C. The heat seal time was varied from 0.5 to 2.0 s with a constant seal pressure of 0.2 MPa. The effect of heat seal conditions on heat seal properties of PLA/TPS films was investigated. Heat sealed strength was carried out by peel testing. Differential scanning calorimetry was used to analyze thermal properties and crystallinity of the heat sealed PLA/TPS films. From the results, heat sealed strength of PLA/TPS blend films decreased when increasing the heat sealed times. PLA films was peelable at the heat sealed temperature of 90 °C. PLA/TPS heat sealed films exhibited greater crystallinity than the PLA heat sealed film.

Characterization of Polyethylene Pipe Degradation by FTIR Microspectroscopy Imaging Method

Kiyomi Okada, Tetsuya Tsujii, Tatsuro Ueda, Kazushi Yamada, Hiroyuki Nishimura, May 2013

Polyethylene (PE) pipe life time prediction was carried out by using FTIR micro spectroscopy imaging and DTA analysis. The FTIR imaging method was used for considering the rapid change of the yield stress ratio of the specimen by the tensile test due to thermal degradation of PE after the hot air exposure at 120 °C. From the results, PE structural change took place after the reduction of antioxidant in the specimen. The results have been in an agreement with the evaluation of DTA analysis for the surface and inside area of the specimen. The FTIR micro spectroscopy transmission and ATR imaging method makes it possible to exactly and easy clarify the degradation mechanism of the PE pipe.

Benefits of Hollow Glass Microspheres in Glass Fiber Reinforced Thermoplastics

Baris Yalcin, Steve E. Amos, Mark J. Williams, Ibrahim S. Gunes, Stefan Friedrich, Marcel Doering, May 2013

Hollow Glass Microspheres, due to their unique spherical geometry and low density, provide several benefits in glass fiber reinforced composites. They help produce lighter weight parts in order to achieve stringent fuel economy targets for automotive and aerospace manufacturers. They also provide productivity benefits through shorter cooling times, enhanced dimensional stability and less warpage – helping to reduce waste and improve throughput. This paper demonstrates these benefits with effective formulation strategies in glass fiber filled polypropylene and polyamides.

Viscoelastic Simulation of Bi-Layer Coextrusion in a Square Die: An Analysis of Viscous Encapsulation

Mahesh Gupta, May 2013

The Giesekus model is used for viscoelastic simulation of a bi-layer flow in a square die. In contrast to the experimental data reported in the literature, in the present work even with viscoelastic effects included in the simulation, encapsulation of a high viscosity polymer by a lower viscosity polymer could not be captured. Since the viscous encapsulation could not be captured with a purely viscous formulation either, it is concluded that the difference in the wettability and surface tension of the two polymers is probably the major factor resulting in the encapsulation.

Precision Milling of Hardened Tool Steel for Micro Mold Making

Florian Böhmermann, Oltmann Riemer, May 2013

High volume production of micro parts from metals or plastics requires appropriate replication processes like micro metal forming or micro injection molding. Regardless which replication process is applied micro molds and their manufacture - very often made from hardened tool steels - are crucial for an economic success. Here precision milling has shown its great potential and examples for the mold making as well as replication are given. Nevertheless, the decisive measure for parts’ quality are often their mechanical properties and testing of micro parts shows specific challenges.

Methodology for Generation of Time-Temperature-Transformation (TTT): Solid and Cellular EPDM rubber

Nora Catalina Restrepo-Zapata, Tim A. Osswald, Juan Pablo Hernandez-Ortiz, May 2013

The vulcanization kinetics of solid and cellular EPDM is studied using Differential Scanning Calorimetry (DSC). This study uses dynamic DSC to obtain the total heat of vulcanization and isothermal DSCs show the reaction rate behavior at constant temperatures and the presence of the diffusion in the process, using a novel technique (quasi-isothermal tests). Modeling employs modified Hernandez-Ortiz and Osswald methodology that uses a non-linear regression routine and is based on Kamal-Sourour model to calculate the kinetic variables of the reaction; also includes DiBenedetto’s equation to find the diffusion variables. The TTT-cure diagrams are built by numerical integration of the adjusted kinetic model and vitrification line is calculated by the change of glass transition temperature (Tg) with curing degree.

Effect of process parameters on properties of devulcanized rubber obtained from a supercritical CO2 assisted devulcanization process

Mohammad Meysami, Prashant Mutyala, Shuihan Zhu, Costas Tzoganakis, May 2013

Continuous devulcanization of tire rubber crumb was performed using supercritical CO2 in an industrial scale twin screw extruder. A reasonably high throughput extrusion process has been developed and the effect of processing conditions has been studied. Using a fractional factorial design in three levels, the effects of process temperature, screw speed, and feed rate on the sol and gel fractions and degree of devulcanization of devulcanized rubber have been investigated.

Using Novel Ethylene-maleic anhydride (EMAh) Copolymers To Upgrade Recycled Nylon To Match or Exceed Prime Virgin Nylon Performance

Ashok Adur, May 2013

Nylon is widely used in many applications. There is a vast amount of recycled nylon coming from the carpet and textile and other industries. Due to degradation and loss of viscosity, this recycled nylon has reduced performance and limited its use. The unique chemistry of alternating copolymers of ethylene and maleic anhydride provide several advantages for upgrading recycled nylon. This paper discusses the results obtained with compounding prime grade nylon as well as recycled nylon with the addition of small quantities of this copolymer and specific property improvements for applications in injection molded compounds. The resulting compounds are performance that can match or exceed prime virgin nylon at 30-50% cost savings.