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

EFFECTS OF ANNEALING TIME AND TEMPERATURE ON THE CRYSTALLINITY AND DYNAMIC MECHANICAL BEHAVIOR OF INJECTION MOLDED POLYLACTIC ACID (PLA)

Yottha Srithep, Paul Nealey, Lih-Sheng Turng, May 2012

The effects of annealing time and temperature on the crystallinity of poly(lactic acid) (PLA) were investigated. The degree of crystallinity observed after short annealing times resembled those observed at cooler temperatures, suggesting a time–temperature superposition relationship. Crystallinity isotherms in the logarithmic scale were shifted horizontally along the log-time axis and a master curve was constructed. Dynamic mechanical analysis showed that an increase in crystallinity increased the glass transition temperature and improved the storage modulus.

EFFECT OF THE MOLECULAR STRUCTURE OF PLASTICIZER ON THE MORPHOLOGY OF POLYMER BLENDS WITH THERMOPLASTIC STARCH

Ata Taghizadeh, Basil D. Favis, May 2012

In this study, two different plasticizers from the polyol family have been used in the preparation of thermoplastic starch. The effect of these plasticizers on the interfacial modification of thermoplastic starch/polyethylene mixtures has been examined. When a higher molecular weight plasticizer is used, a different emulsification behaviour is observed for compatibilized systems. The number average droplet size decreases much more effectively with compatibilizer content than the volume average diameter. This behaviour is attributed to the chemical structure of the plasticizer. The mechanical properties of these systems are also presented.

MORPHOLOGY OF POLY(LACTIC ACID)/POLY(BUTYLENE ADIPATE-CO-TEREPHTHALATE) BLENDS AND ITS COMPOSITE WITH SPHERICAL SILICA PARTICLES

Ebrahim Jalili Dil, Pierre Carreau, Sepehr Ravati, Basil Favis, May 2012

In this work the detailed morphology of poly(lactic acid)/ poly (butylene adipate-co-terephthalate) has been carried out for the first time. The morphology of PLA/PBAT blends with different compositions was studied and limits of the co-continuity region were determined using rheological measurements and image analysis. Particle size analysis and breaking thread experiments showed that PLA/PBAT is a very low interfacial tension polymer blend. Moreover, composites of PLA/PBAT/spherical silica particles were prepared and the localization of silica particles in this blend was studied.

CARBON NANOTUBES IN BLENDS OF THERMOPLASTIC STARCH/POLYCAPROLACTONE CARBON NANOTUBES IN BLENDS OF THERMOPLASTIC STARCH/POLYCAPROLACTONE

Ata Taghizadeh, Basil D. Favis Ata Taghizadeh, Basil D. Favis, May 2012

Polycaprolactone (PCL) has been blended with thermoplastic starch (TPS) and carbon nanotubes in different compositions. The localisation of solid particles is an influential factor in filled polymer blends. Hence, SEM and TEM images have been used to investigate the morphology and localisation of nanofilled-polymer blends. .The blending of a semicrystalline polymer with another polymer or nanofillers will also change the thermal properties of the polymers in different ways. This change has been studied by non-isothermal crystallization curve analyses. These results were interconnected in such a way that it was possible to confirm the localisation from thermal properties.

SELECTIVE LOCALIZATION OF SPHERICAL SILICA PARTICLES IN HETEROPHASE POLY(LACTIC ACID)/ LOW DENSITY POLYETHYLENE BLENDS

Ebrahim Jalili Dil, Basil Favis, May 2012

In this article, different strategies to control the localization of spherical silica particles in Poly(lactic acid)/ Low density polyethylene blends were studied. These strategies include different sequences of addition of components and compatibilization. Results show that using these different strategies, the controlled localization of silica particles in either the matrix or in the dispersed phase can be achieved. Long processing times used in this study show that the observed localization is stable and does not change with further processing.

HIGHLY GAS PERMEABLE UV CURED, PERFLUORINATED ACRYLATE MODIFIED THIOL-ENE NETWORKS WITH TUNABLE TRANSPORT PROPERTIES

James Goetz, Brian Greenhoe, Sergei Nazarenko, May 2012

Optically clear perfluorinated acrylate modified thiol- ene network films were prepared via a two-step approach, first by modifying multifunctional thiols with perfluorinated acrylates of different length followed by UV curing in the presence of multifunctional enes. By increasing the length of the perfluorinated species, free volume of the networks was shown to noticeably increase. As a result, oxygen permeability showed more than a three order of magnitude improvement with the increase of the length of perflurinated moieties as compared to unmodified network. Water vapor permeability also increased but to a critical level.

USING FINITE ELEMENT ANALYSIS TO ADVANCE HEAT STAKE DESIGN

Chin-Jung Chen, Chung-Yuan Wu, May 2012

Staking is a widely used joining technique to bond similar and dissimilar materials. There are many different staking techniques, such as ultrasonic staking, hot air cold staking, heat staking, and infrared staking. Recently, impulse staking and laser staking were also reported. The concept of staking is by deforming a stud or a hollow boss to form a button (or mushroom) to mechanically hold two materials together. This work utilized finite element (FE) modeling to study the effect of stake geometry on retention force. For FEA modeling, 3-D solid models were constructed to simulate the stake under a tensile load. It was found that a minimum button height to pin diameter ratio of 0.625 was required to had necking occurred in the pin during tensile loading. In addition, smaller hole opening provided higher retention force for shorter stake; however, for a larger stake this effect is minimum. A minimum overlay at the opening is required to have necking occurred in the pin. Furthermore, difference between theoretical and practical design was also discussed.

IMPROVED APPROXIMATIONS IN THERMAL PROPERTIES FOR SINGLE SCREW EXTRUSION

Eberhard Grünschlos, María del Pilar Noriega, May 2012

Actual screw design software is capable to simulate the performance of a single screw extruder based on elaborated program codes. The aim of this work is to present improved approximations in relevant thermal properties for simulation and design of single extrusion screws in combination with analytical calculations appropriate for the industrial praxis. The developed approximation functions for thermal properties, such as, specific heat capacity, enthalpy, thermal conductivity and density, were obtained looking for small number of parameters. A comparison between the improved approximation functions, existing known functions and measured data for some common polymer families is shown.

MULTI-COMPONENT BIO-BASED BLENDS WITH POLYLACTIC ACID AND POLYHYDROXYBUTYRATE: MORPHOLOGY AND PHYSICAL PROPERTIES

Sepehr Ravati, Christine Beaulieu, Louise Deschênes, Viêt Cao, Basil Favis, May 2012

Polylactic acid (PLA) and polyhydroxybutyrate (PHB) are two of the most important polymers derived from renewable resources. In this work, the morphology and physical properties of binary blends of PLA/PHB and multi-component blends of PLA/PHB with other commodity polymers such as polystyrene (PS) or biodegradable polymers such as polycaprolactone (PCL), poly (butylene succinate) (PBS), and poly(butylene adipate-co-terephthalate)(PBAT) were examined. Completely biodegradable blends of PLA/PHB/PBAT/PCL and PLA/PHB/PBAT/PBS demonstrated some unique morphologies including triple percolated systems.

MULTICOMPONENT BIODEGRADABLE BLENDS WITH POLY(BUTYLENE SUCCINATE): PARTIAL AND COMPLETE WETTING PHENOMENA

Sepehr Ravati, Basil Favis, May 2012

PBS (Poly(butylene succinate)) is a promising emerging bioplastic with good strength and modulus, however, its elongation at break (EB) is quite low and blends with higher EB materials are a potential route to develop more balanced properties. Blends of PBS with biodegradable polymers including polycaprolactone (PCL), poly(butylene adipate-co-terephthalate) (PBAT), and poly(lactic acid) (PLA) were studied. These blends result in fully-biodegradable blends with completely different thermodynamically stable wetting behaviors and hence, significantly different potential morphological states.

FEM MODELING OF SURFACE FRICTION EFFECT ON SCRATCH-INDUCED DEFORMATION IN POLYMERS

Mohammad Motaher Hossain, Hung-Jue Sue, May 2012

Three-dimensional finite element method (FEM) parametric study was performed to investigate the effect of surface friction on scratch-induced deformation. By varying the post-yield behavior of the polymer substrate, the effect of surface friction on scratch depth and its correlation with the strain hardening slope is sought. The simulation results indicate that the onset of groove formation during the scratch process is strongly influenced by surface friction. Also, increase in strain hardening slope reduces the relative frictional effect on scratch depth.

IN-LINE MEASUREMENT APPARATUS FOR RESIDENCE TIME DISTRIBUTION IN TWIN-SCREW EXTRUDER AND ITS APPLICATION IN POLYMER PROCESSING

Cailiang Zhang, Xueping Gu, Jiajun Wang, Lianfang Feng, Guohua Hu, May 2012

The simulation of thermally and flow induced crystallization behavior of semi-crystalline polymers is of great engineering significance in polymer processing like injection, blow molding and extrusion. However, its key technology for practical application remains to be difficult. In the study, the mathematical model of three- dimensional thermally and flow induced crystallization of polymer melts obeying Phan-Thien and Tanner (PTT) constitutive model is established. A penalty finite element/finite difference method is introduced to solve the nonlinear governing equations. The computation stability is improved by using the discrete elastic-viscous split stress (DEVSS) algorithm incorporating the streamline upwind scheme. A modified Schneider’s approach is employed to discriminate the relative roles of the thermal and the flow state on the crystallization phenomenon. Two driving causes for the crystallization of polypropylene in extrusion process including the thermal and the flow state are investigated. Both the crystalline distribution and crystalline size of polypropylene are obtained based on the proposed mathematical model and numerical scheme.

RHEOLOGICAL CHARACTERIZATION OF INJECTION MOULDING GRADE THERMOTROPIC LIQUID CRYSTAL POLYMERS (LCPS)

Ahmed Rahman, Rahul K Gupta, Sati N. Bhattacharya, Shishir Ray, Franco Costa, May 2012

Liquid Crystal Polymers (LCPs) are advanced high temperature processing polymers with unique physical properties. It contains rigid rod like molecules, which exhibit structural orientation during the flow process at one or two dimensional level. Rheological behaviour of unfilled LCPs and filled (glass fibre) LCPs were characterized with ARES and Capillary rheometer at low and high shear rates. The complex viscosities (h*) as well as shear viscosities (h) showed a typical shear- thinning behaviour. LCPs exhibit anomalous rheological behaviour with shear and temperature. Viscosity reduced at low shear rate region because of the tumbling nature of rod like molecules. The abnormal temperature dependence of the viscosities can be explained by the transition of anisotropic rod-like molecules to isotropic molecules with increase in temperature. In steady shear flow, it was observed that rotational transformation occur from direction of flow to surface direction, which leads to first negative normal stress difference (N1) with shear rate. Stress relaxation conducted after cessation of shear flow to prove the molecular dynamics. Multiple overshoot observed due to tumbling, which was varying with temperature and shear rate.

EFFECT OF PLASTICIZER ON THE PHYSICAL PROPERTIES OF TRI-ACETYL CELLULOSE FILM

Hongsuk Kim, Ho-Jong Kang, May 2012

Tri acetyl cellulose (TAC) is not a good material for the chain stretching due to its main chain rigidity. Plasticizers were introduced to increase the chain flexibility and the effect of plasticizer on physical properties of TAC film was studied. The lowering of glass transition temperature, melting temperature and crystallinity were found and this was understood that plasticizer provided the main chain mobility by reducing interaction between TAC molecules. These made possible to stretch the TAC chain under low stretching temperature and resulted in the development of birefringence in TAC film which indicated the characteristic of retardation film

QUALITY OPTIMIZATION OF INJECTION-MOLDED PLASTIC LENSES VIA MODEL FREE OPTIMIZATION METHOD

Xiangsong Kong, Shengqiang Zhu, Yi Yang, Zhijiang Shao, Xi Chen, Lingyu Zhu, May 2012

Quality is the key to injection-molded plastic optical lenses. To improve the lens quality, a systematic model-free optimization (MFO) method is proposed to minimize the part quality subjected to specified range of focal length. Rather than building a model to correlate the relations between process variables and quality variables, this method online optimize the process by directly using the measurement for function evaluation. An iteration termination control methodology is developed and integrated for the quality optimization. The effectiveness of the MFO has been demonstrated through experiments.

AN EXPERIMENTAL STUDY ON THE DIMENSIONAL CHARACTERISTICS OF 7 INCH LIGHT GUIDE PLATE MANUFACTURED BY INJECTION/COMPRESSION MOLDING WITH RAPID HEATING OF A MOLD

Inki Min, Seokkwan Hong, Yongju Lee, JeongJim Kang, Kyunghwan Yoon, May 2012

From micro featured optical products made by conventional injection molding(CIM) the defects of inhomogeneous shrinkage and incomplete filling of micro pattern can be found easily because of concentrated residual stresses near gate and the formation of frozen layer. To reduce the inhomogeneous shrinkage in thickness direction injection/compression molding(ICM) can be used by applying compression of mold rather than applying packing pressure through the gate. To achieve better transcription of micro pattern on the product from the mold rapid heating and cooling molding(RHCM) has shown the advantages by heating the mold surface above glass transition temperature of polymer used. In the present study a series of experiments using ICM combined with RHCM named RICM(RHCM+ICM) was conducted to increase both the transcription ratio of micro pattern and the uniformity of thickness for 7 inch sized BLU-LGP(Backlight unit-light guide plate). As a result, the standard deviation of thickness was reduce from 0.024(ICM)~0.025(RHCM only) mm to 0.005(RICM) ~0.007(ICM) mm by apply compression process. In the cases of CIM and ICM average transcription ratio of micro pattern showed 42.0% and 63.2%, respectively. On the other hand, the transcription ratio of micro pattern in the cases of RHCM and RICM showed almost 100% while the mold temperature reached above glass transition temperature. By the application of ICM combined with RHCM both the transcription ratio of micro pattern and the uniformity of thickness can be improved dramatically even the maximum mold temperature of RICM was 10°C lower than the case of RHCM only.

BIOMASS MATERIALS, SHAPE MEMORY POLYURETHANE

Jia Hong Li, May 2012

In this study, the aliphatic or aromatic isocyanates and poly-alcohols was used to synthesize polyurethane with shape memory function, which the polyol was derived from the biomass polylactic acid (PLA). The recycled PLA was degraded into the low molecular weight PLA (Mw 1,000) and the chain extension agent (1,4-butanediol, BDO) reaction was added to form biomass polyol. The analysis of Fourier transform infrared spectroscopy (FTIR) and Gel permeation chromatography (GPC) were proved the synthesis of polyol. The recovery ratio of shape memory and mechanical properties of polyurethane were improved significantly due to the urea structure, the biomass polyurethane with shape memory could be increased up to 95% of recovery ratio. Different isocyanate (hexamethylene diisocyanate, HDI, or 4,4- diphenylmethene diisocyanate, MDI) were compared and found that the functional group of aromatic was better than that of aliphatic in the synthesis of polyurethane with shape memory behavior.

INJECTION VELOCITY CONTROL USING 2D MODEL PREDICTIVE ITERATIVE LEARNING ALGORITHM

Yi Yang, J. Shi, F. Gao, May 2012

As a typical batch process, injection molding has the following unique features compared to traditional continuous processes: repeatability, two-dimensional dynamics and stages based operations. A sophisticated control algorithm shall exploit all these features. In this paper, a systematic two-dimensional model predictive iterative learning control algorithm is introduced to control the injection molding process with the injection velocity as an application example. The experimental results prove that the control algorithm has good performance and robustness.

THE STRUCTURE AND PROPERTIES OF PLA/PP POROUS FILM

C. Chau, J. Williams, S. Solovyov, T. Powers, P. Koch, May 2012

Polylactic acid and polypropylene were melt blended and extruded into 3-10 mil films. Differential scanning calorimetry studies showed the polymer blends, unlike the neat PP and PLA materials, exhibited crystallization exotherm in heating scans with a crystallization point varied with the ratio of PLA to PP. This melt crystallization behavior was enhanced with the increase of the content of PLA from 25 to 75%. The polymer blends also showed multiple melting points ranging from approximately 140 to 175°C depending on the ratio of the two polymers and the heating rate. The formation of a new crystallization temperature, the shifting of the melting points, and/or the formation of new melting points suggested some compatibility between PP and PLA. Upon uniaxial stretching, the originally translucent films showed strong stress-whitening phenomena with widespread porous structure developed in the whitened region. SEM showed fibrils with a typical diameter of 2 micron and voids or pores of approximately 5 micron developed in the whitened region. The partial compatibility between PLA and PP could have contributed to the homogeneity of the stress-whitening and the porous structure in the film. The porous films provided two folds or higher increase in oxygen transmission rate depending on the material composition and draw ratio. The structural development and the potential use of the porous PLA/PP films in packaging application are discussed.

DECISION TREE CLASSIFIER FOR ANALYSIS OF PARAMETERS ASSOCIATION CAUSING POLYMER COLOR MISMATCH

Farid Bourennani, Jamal Alsadi, Ghaus M. Rizvi, Daniel Ross, May 2012

Nowadays, most manufacturing companies store their data electronically. The selection of the appropriate data mining algorithm for exploration of this data can quickly identify issues leading to process improvement and cost reduction. In this paper, The Decision Tree Classifier (DTC) is used for plastic color mismatch parameters analysis. Especially, the relationship between polymer grade, color, type, line of production, and ingredients supplier is analyzed. DTC Results showed interesting and evident relationships between certain parameters.