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

A Study of Rolling Resistance of Electrospun Polymer Fabrics
Shing-Chung Wong, Shuwen Chen, Ashenafi Hegana, Ashenafi Hegana, May 2013

Rolling resistance contributes to 6-10% of the overall fuel consumption of vehicles. Little is understood on the relationship between rolling resistance and surface characteristics such as adhesion, surface asperities and topology. In this study, we evaluate the rolling resistance using a free oscillation of a pendulum. Different substrate materials such as asphalt, rubber, wood, high-density polyethylene (HDPE), nylon, polycaprolactone (PCL) and poly(vinylidene fluoride) (PVDF) were tested by a laboratory fabricated pendulum steel roller. The damping factor is examined using an envelope analysis technique based on Hilbert transform methodology. The rolling resistance is found to depend on viscoelastic properties, adhesion and surface characteristics. The damping factor is the highest for asphalt and the second highest for rubber. The damping factor of electrospun polymer fabrics lies somewhere in between those pertaining to asphalt and more rigid substrates such as steel and copper

Key figures for describing and comparing the energy consumption of injection molding processes
Matthias Düngen, Markus Hardge, Michael Koch, May 2013

This paper deals with energy consumption data for a broad variety of injection molded parts. An analysis shows that key figures can be derived for comparison and reference purposes and allow the evaluation of the energy efficiency in a part dependent production process. The key figures comprise material properties and part geometries to build a focus relative to these particular part characteristics independent of category or application. This approach goes beyond the widely applied method of examining a machine specific energy consumption data. A significant potential of energy reduction for most analyzed injection molding processes is expected.

Microcellular injection molding of in-situ modified Poly(Ethylene Terephthalate) with supercritical nitrogen
Zhenhao Xi, Fanglin Zhang, Tao Liu, Ling Zhao, Lih-Sheng Turng, May 2013

The microcellular injection molding (commercially known as MuCell) of in-situ polymerization-modified PET (m-PET) was performed using supercritical nitrogen as the physical blowing agent. Based on design of experiment (DOE) matrices, the influence of operating conditions on mechanical properties of molded samples were studied systematically for two kinds of m-PETs, namely, n-m-PET and m-m-PET synthesized using pentaerythritol (PENTA) and pyromellitic dianhydride (PMDA) as modifying monomers, respectively. The optimal conditions for injection molding were obtained by analyzing the signal-to-noise (S/N) ratio of the tensile strength of the molded samples. The specific mechanical properties, especially the impact strength, of the microcellular samples under these conditions increased significantly. Scanning electron microscope (SEM) analyses showed a uniform cell structure in the molded specimens with an average cell size of around 35 ?m. The m-m-PET modified with PMDA generated a slightly finer cell structure and a higher cell density than the n-m-PET.

Equipment and Material Considerations for Microcellular Foaming
Luis Zalamea, Simon Dominey, May 2013

Microcellular foaming processes are now proven technologies and integral part of the “mainstream” in polymer conversion operations. The present paper is a joint effort between two companies (Dow and Mucell) to address key aspects necessary to achieve a more efficient use of materials and resources via physical foaming. The paper reviews in detail all aspects that influence performance, paying special attention to the synergies that arise between hardware and material selection. A comparison of performance between chemical and physical blowing is analyzed, highlighting the advantages of microcellular foaming.

High Temperature Aesthetic Grade Liquid Crystal Polymers for Consumer Applications: Not Just For Connectors Anymore
Mark Tyler, May 2013

For many years the use of high flowing engineered resins, such as Liquid Crystal Polymer (LCP), have been used for very detailed and intricate parts in the electronics and connector industries where function and performance far outweigh any need for coloristic attributes. Today we find the uses of such resins extending out to more visible consumer products that need the performance and functionality of the LCP with the additional demand of excellent aesthetics. This paper looks to show where the coloring of LCP and the producing of aesthetically pleasing parts has brought LCP’s from behind the scenes to center stage for the consumer products industry.

Simulating the directionality of liquid crystalline polymers
Arash Ahmadzadegan, Michael A. Zimmerman, Anil Saigal, May 2013

In this paper a practical method of modeling directionality of crystals in liquid crystalline polymers (LCPs) is studied. The main components of this method represent the effects of shear on crystals, the effects of crystals on each other and the effects of movement of crystals with the flow. The implementation of this simulation is done by coding a user defined function (UDF) in ANSYS® FLUENT®. The results of the simulation are shown in two and three dimensions. The presented results show promising closeness to the physical phenomenon associated with the directionality of LCPs. The proposed method can be used as an estimation of the directionality of crystallines during the processing.

Crystallographic Analysis of Electrospun Poly(?-caprolactone) Nanofibers by 2-D Wide-angle X-ray Diffraction (2D WXRD)
Xiaofeng Wang, Jing Jiang, Jin Sha, Haibin Zhao, Jian Han, Lih-Sheng Turng, Qian Li, May 2013

The crystalline morphology of electrospun PCL nanofibers was studied. Random and aligned nanofibers were obtained by a conventional plate collector and a two-parallel-conductive-plate collector, respectively. Scanning electron microscopy (SEM) and 2D wide-angle X-ray diffraction (2D WXRD) were employed to characterize the nanofibers. The degree of crystallinity of aligned nanofibers was higher than that of randomly aligned nanofibers. The crystallites in the nanofibers were highly oriented along the nanofiber axis, as were the molecular chains. The estimated crystallite size in the nanofibers suggested that a single nanofiber was composed of dozens of nanofibrils and a nanofibril was further composed of crystallites along the nanofiber axis with an amorphous region of extended PCL molecular chains between neighboring crystallites.

Mechanical Properties of Interconnected Porous Elastomers Fabricated by a Microsphere-Templating Casting Process
Yifeng Hong, Haibo Gong, Jack G. Zhou, Donggang Yao, May 2013

The mechanical properties of interconnected porous polysiloxane elastomers under tension and compression were studied in this work. The porous elastomer was found to be highly deformable and had non-affined tensile deformation. The increase of pre-set strains and strain rates in cyclic tension and compression resulted in an increase of stresses at pre-set strains and hysteresis. The permanent sets after unloading process non-linearly decreased as the strain rates were lowered in cyclic compression while the strain rates seemed to have very limited influence over permanent sets in cyclic tensile testing.

Crystallization of Polypropylene: The Effect of Shear and Temperature
Savvas Hatzikiriakos, Maziar Derakshandeh, Mahmoud Ansari, Antonios Doufas, May 2013

The final mechanical properties of a plastic product which is made of semi-crystalline polymers depend significantly on the molecular properties and the applied processing conditions. Particularly, the formation of flow induced structures via polymer crystallization plays a major role in defining the final attributes of the product. In this paper, the effects of shearing and temperature on the flow induced crystallization of several polypropylenes are examined using rheometry. Generally, strain and strain rate found to enhance crystallization in simple shear at temperatures between the melting and crystallization points. The effects of molecular weight and its distribution are also examined and observed to have a strong influence on flow induced crystallization structures.

Microcellular Foaming of Poly(lactide acid)/Nanosized Calcium Carbonate Composites
Dajiong Fu, Wenhao Zhang, Binyi Chen, Peng Yu, Xiangfang Peng, May 2013

This article focused on the study of the effect of nanosized CaCO3 on foam morphology of PLA using CO2 as the foaming agent. The thermal properties were investigated through the TG and DSC methods. The presentation of CaCO3 acted as nucleation site to facilitate the crystallization of PLA that resulted the greatly increase of PLA crystallization up to 69.14%. The SEM results showed that the addition of CaCO3 significantly improved the foam morphology, cell size decreased and cell density increased greatly. When the content of CaCO3 is 30wt%, they are similar to the content of 20wt%. Because of the incompatibility of CaCO3 and PLA, the addition of CaCO3 decreased the mechanical properties of PLA.

Foaming Morphology of Microcellular Injection Molded Parts - Simulation and Experimental Characterization
Tai-Yi Shiu, Yuan-Jung Chang, Chao-Tsai Huang, Chia-Hsiang Hsu, Rong-Yu Chang, Shyh-Shin Hwang, May 2013

We present the morphological study of microcellular injection molded product using amorphous and semi-crystalline polymers with nitrogen. The cellular structure and cell distribution probed by scanning electron microscope (SEM) were compared with three-dimensional simulation of cell size and density distribution. The morphological comparisons between SEM photos and simulations were analyzed for three different locations along the flow direction. Good agreement between simulation and real molded part prove the capability of commercial CAE software in 3D prediction of microcellular foaming process; furthermore, expensive morphological study from SEM can be economically assisted by simulation tool for industrial application.

Preparation an dMicrocellular Foaming Investigation of Poly (Lactic Acid)/Talc Composites
Zhang Wen-Hao, Fu Da-jiong, Chen Bin-yi, Wang Tao, Peng Xiang-fang, May 2013

This study investigated the influence of talc content on the mechanical/thermal properties and crystallization behavior of PLA/talc composites. Talc was compounded with poly (lactic acid) (PLA) via a triple screw extruder, and the foaming properties of the blends were investigated by using a homemade foaming device. Carbon dioxide was used as the blowing agent. The impact strength were significantly increased (by 10%-31%) at the expense of a certain degree of reduction of tensile strength. Owing to the nucleation effect of talc, the 5% talc blends received the maximum crystallinity (43.8%). Furthermore, when the talc content was 10%, the foaming sample obtained the maximum cell density and the minimum cell size.

A Nanoscaled Three Dimensional Structure Created By Using Electrospun Poly(?-Caprolactone) (PCL) Nanofibers and Induced PCL Crystallization
Xiaofeng Wang, Xiaofeng Wang, Max R. Salick, Xiaodong Wang, Zhixiang Cui, Yiyan Peng, Jian Han, Lih-Sheng Turng, Qian Li, May 2013

A nanoscale, three-dimensional structure consisting of poly(?-caprolactone) (PCL) nanofibers covered by periodically spaced PCL crystal lamellae was successfully created using a self-induced crystallization method. The shish-kebab structure was obtained by inducing PCL crystallization on electrospun PCL nanofibers immersed in a PCL solution followed by solvent evaporation. The resulting structure highly resembled the nanotopography of natural collagen nanofibrils in the extracellular matrix (ECM) of natural tissues and thus could be a good in vitro model for tissue engineering scaffolds.

Predication of Weld Joint Long-Term Strength Under Creep Conditions
Haiying Zhang, Haiying Zhang, Alexander Chudnovsky, Prasanna Kondapalli, William McMaster, Ankur Bhosale, Douglas Shearin, May 2013

Based on failure analysis of glass reinforced Polyamide (PA) weld joints, this paper proposes a thermodynamic model for weld joint lifetime using continuum damage mechanics and Eyring kinetic equation for damage growth. It presents the formulation of the model, and uses the accelerated test data to estimate basic parameters: activation energy and activation volume of fracture. The model is also validated by comparison its predictions with a relatively low temperature test data.

Use of a Stack Mould to Increase the Productivity and the Quality in the Injection Molding
Maria V. Candal Pazos, Orlando Pelliccioni, María E. Fernández, May 2013

The main objective of this research was to study the effect of the injection process conditions over the quality and final properties of plastic parts made in stack moulds. For that, there were used CAD/CAE tools. As a result, it was obtained that when the melt and mold temperatures are increased, the volumetric shrinkage of the molded parts is also increased, and this coincides with the obtained results in hot runners’ moulds. By other hand, when the holding/packing pressure is increased, it is observed a decrease in the parts volumetric shrinkage, as well as in cold and hot runners’ moulds. When the melt temperature increased and the injection velocity decreased, the residual stress in the plastic parts are reduced.

Injection Molding of Rigid Vinyls
Paul Mastro, May 2013

Rigid Polyvinyl Chloride and Chlorinated Polyvinylchloride are highly viscous materials that are susceptible to thermal degradation. This combination makes them very challenging to process consistently and often require temperature conditions that are quite a bit different than what someone who has processed other thermoplastics is used to. Also, these materials require some special modifications to the molding machine to facilitate processing. By understanding how the polymer is responding to the process conditions imposed on it, a stable, repeatable process can be established that will produce consistent, high quality parts

Processing effects on permanent electrically conductive HDPE- Conductive Carbon Black composites
Daniele Bonacchi, Christine Van Bellingen, May 2013

Conductive carbon black is still today the most used solution to give permanent electrical conductivity to plastic materials. Electrical conductivity of the final material is known to be affected by processing history and especially final transformation processes as they can induce changes in the filler properties or distribution. In a recent work we highlighted the large difference in the percolation curves of the electrical resistivity of compression and injection molded samples of conductive and extraconductive carbon black loaded HDPE. Such difference can be addressed to different effects such as surface induced segregation, carbon black structure reduction or different crystallization of the polymeric matrix. In this work we investigate by simple but specific tests the relative importance of these factors evaluating their contribution to the modification of the final electrical properties of the material.

Thermo-Mechanical Property Prediction for Long Fiber-Filled Thermoplastics Composites
Xiaoshi Jin, Jin Wang, May 2013

Following on from the long fiber orientation and long fiber breakage model implementations in the past, long fiber enhanced polymer composite property calculation models have been implemented for long fiber-filled injection moldings. These long fiber composite properties are useful in terms of residual stress calculation, warpage prediction and subsequent structural analysis. Major differences between long fiber and short fiber composite property enhancements include the non-uniform fiber length distribution across injection molded parts and possible de-bonding between fiber and matrix. This paper addresses these differences by presenting a recently implemented micro-mechanical models specific to long fiber composites, which makes use of calculated long fiber orientation and fiber length distributions. A case study on fiber orientation distribution (FOD), fiber length distribution (FLD) and subsequent long fiber composite property distributions are given for injection molding simulation.

PVDF/ Carbon Nanotubes/Nanoclay Nanocomposites For Piezolectric Applications
Farhad Sadeghi, Ali Sarvi, Uttandaraman Sundararaj, May 2013

Poly(vinylidene) fluoride (PVDF) nanocomposite samples were prepared by incorporation of carbon nanotubes (CNT) and nanoclay into PVDF using a twin screw extruder. Carbon nanotube was added to improve electrical conductivity and nanoclay was included to enhance ? crystal formation for piezoelectric property. X-ray diffraction (XRD) results showed that partial melt intercalation of PVDF in clay was achieved. The XRD results also revealed that CNT and nanocaly addition increased ? phase crystal amount in PVDF. FTIR spectroscopy measurements confirmed the XRD results and showed that the effect of nanoclay on ? phase crystal formation of PVDF was more prominent than CNT. It was found that shear rate applied during crystallization would improve ? phase crystal formation but only for the neat PVDF. Conductivity results showed that addition of CNT improved conductivity as a percolation of 2 wt. % was observed. It was found that clay incorporation into CNT nanocomposite could improve conductivity more.

Simulation of Cooling Using a New Model for the Determination of the Thermal Diffusivity in Injection Molding by Means of the Radial Function Method (RFM)
Iván D. López, Alberto Naranjo, May 2013

A numerical simulation using a meshless method is developed to describe the cooling of injection molded slits of different thicknesses with an improved thermal diffusivity model that considers the effect of cooling rates and processing conditions. For the filling phase, the fountain flow effect is taken in account. Numerical results are analyzed by examining the effects of the traditional and improved thermal diffusivity model. The predicted effect agrees well with previous measured data. For the case studied in this paper, the use of the traditional model results in a temperature underestimation.

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