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Conference Proceedings

INVESTIGATION ON THE TEAR PROPERTY OF POLYETHYLENE BLOWN FILMS AT VARIABLE ANGLES

Byoung-Ho Choi , Rajen Patel , A. Willem deGroot , Mehmet Demirors , Lizhi Liu , Kenneth Anderson, May 2010

Tear is a key physical property of polyethylene (PE) blown films. There are many variables which affect the overall tear property such as tear path, plastic deformation wake, and so on. In this study, five blown PE films were prepared and tested by the Elmendorf tear test at five sampling angles, i.e. 0 (MD), 30, 45, 60, 90 (CD) degrees.Tear values were analyzed statistically and the variation of the tear data was investigated based on the observation of the tear samples. The mechanism of severely curved crack, i.e. J-tear, was also studied to understand the tear property variation of blown PE films.

MANUFACTURING AND CHARACTERIZATION OF NANO-COMPOSITE LINEAR STRAIN SENSORS

Donald Baird, May 2010

This study explores the potential of using polymer nanocomposites for a strain sensor application. This work focuses on the development of such strain sensors made by casting vapor-grown carbon fiber (VGCF) reinforced polydimethylsiloxane (PDMS). The tensile properties are determined as a function of the VGCF content. Furthermore, the percolation threshold is determined; and the electrical conductivity of nanocomposites with VGCF content above the percolation threshold is measured. Finally, the relationship between electrical conductivity and mechanical strain is determined for loading/unloading cycles to verify the durability and repeatability of the sensors.

CORRELATION OF FILM CASTING BEHAVIOR WITH NON-LINEAR RHEOLOGY FOR A SERIES OF HDPE’S WITH DIFFERENT DEGREES OF SPARSE LONG CHAIN BRANCHING

Donald G. Baird, May 2010

The degree of film-width reduction or necking during film-casting is analyzed for several metallocene-catalyzed high density polyethylenes HDPE with varying degrees of sparse long-chain branching LCB. It is found that the addition of sparse LCB reduces the degree of necking to a greater degree than broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios.

CORRELATION OF FILM CASTING BEHAVIOR WITH NON-LINEAR RHEOLOGY FOR A SERIES OF HDPE'S WITH DIFFERENT DEGREES OF SPARSE LONG CHAIN BRANCHING

Donald G. Baird, May 2010

The degree of film-width reduction or necking during film-casting is analyzed for several metallocene-catalyzed high density polyethylenes, HDPE, with varying degrees of sparse long-chain branching, LCB. It is found that the addition of sparse LCB reduces the degree of necking to a greater degree than broadening the MWD. Analysis of the uniaxial extensional and dynamic shear rheology with the pom-pom constitutive model reveals that a distribution of branches along shorter relaxation time modes is important in reducing necking at higher drawdown ratios.

MODELING INTERFACIAL STRENGTH OF POLYBUTYLENE SUCCINATE(PBS)/POLYPROPYLENE(PP) MULTILAYER INJECTION-MOLDED PART USING FINITE ELEMENT METHODS

Siu N. Leung, Anson Wong, Chul B. Park, May 2010

Polypropylene (PP)-based sandwich injection moldings containing biodegradable polymers in the core were carried out. Interfacial adhesion between the skin and the core is essential for obtaining sufficient mechanical strength for commercial applications. In order to investigate the interfacial strength between the skin and the core, the ASTM/ISO scratch test was used and critical delamination load for delamination was determined. For comparison, an 180o peel test was also conducted, whereby the skin was peeled off from the core, to measure its adhesive force in a different way. Numerical simulation using FEM was applied to these experiments to study interfacial strength. Destruction of the interfacial layer was defined by either a critical stress or critical strain criterion. The critical strain criterion appears to better describe the phenomenon in these two experiments. FEM simulation could qualitatively correlate with these behaviors, suggesting that delamination could be described as a strain dominant phenomenon.

A NEW INTERPRETATION TO THE TALC-ENHANCED POLYMERIC FOAMING PROCESS

Siu N. Leung , Anson Wong , Chul B. Park, May 2010

Cell nucleating agents are commonly used in polymeric foaming processes to enhance cell nucleation. It has been widely believed that the enhancement was through the promotion of heterogeneous nucleation. Even though it has been observed by other researchers that additional bubbles were nucleated near the growing cells despite the low gas concentration the mechanisms have not yet been clearly identified. It seems that with the presence of talc particles the shear and/or extensional fields generated by the growing cells that are near them have a stronger effect on bubble nucleation than the depleted gas concentration. Using the concept of the critical radius for bubble nucleation and the stress fields generated around the talc particles this paper presents a mechanism of cell nucleation for this case.

A NEW INTERPRETATION TO THE TALC-ENHANCED POLYMERIC FOAMING PROCESS

Siu N. Leung , Anson Wong , Chul B. Park, May 2010

Cell nucleating agents are commonly used in polymeric foaming processes to enhance cell nucleation.It has been widely believed that the enhancement was through the promotion of heterogeneous nucleation. Even though it has been observed by other researchers that additional bubbles were nucleated near the growing cells despite the low gas concentration, the mechanisms have not yet been clearly identified. It seems that, with the presence of talc particles, the shear and/or extensional fields generated by the growing cells that are near them have a stronger effect on bubble nucleation than the depleted gas concentration. Using the concept of the critical radius for bubble nucleation and the stress fields generated around the talc particles, this paper presents a mechanism of cell nucleation for this case

TRACKING PHASE SEPARATION KINETICS OF BLOCK COPOLYMER SOLUTIONS USING DYNAMIC MECHANICAL MEASUREMENTS

Vandita Pai-Paranjape, André Van Zyl, Jan Pleun Lens, Dake Shen, May 2010

Rheology is used to track the phase separation kinetics of block copolymer solutions during processing and then modeled using the Avrami equation. Previous studies dealt explicitly with disorder-order transitions following shallow temperature quenches. To make this work applicable to the processing of solution-cast films, styrenic block copolymers in solvents of varying selectivity are cast as thin, dilute samples and dried isothermally so that various constant-concentration kinetics can be tracked. Rheology proves to be useful in tracking both rapid and slow kinetics of diblock and triblock styrenic copolymers in toluene. It is found that the diblock copolymer undergoes faster ordering than a triblock copolymer of comparable molecular weight. A competition between thermodynamic driving forces and kinetic suppression of the phase separation exists as concentration changes. AFM images are provided to confirm the kinetic data and to understand the meaning of the Avrami exponent values determined for the different systems studied.

SCRATCH-RESISTANT TRANSPARENT POLYCARBONATES WITH ECO-COMPLIANT FLAME PROPERTIES

Vandita Pai-Paranjape , André Van Zyl , Dake Shen, May 2010

Polycarbonate resins possessing high surface hardness and improved scratch resistance have been developed for injection molding applications. Due to their transparent nature and good balance of physical and mechanical properties these resins find applications in the business equipment mobile phone and electronic device industries. They also possess increased resistance to oxygen and / or water vapor migration making them suitable candidates for medical packaging. New developments in the area of flame retardancy will be discussed in this paper.

SCRATCH-RESISTANT, TRANSPARENT POLYCARBONATES WITH ECO-COMPLIANT

Vandita Pai-Paranjape , André Van Zyl , Jan Pleun Lens , Dake Shen, May 2010

Polycarbonate resins possessing high surface hardness and improved scratch resistance have been developed for injection molding applications. Due to their transparent nature and good balance of physical and mechanical properties, these resins find applications in the business equipment, mobile phone and electronic device industries. They also possess increased resistance to oxygen and / or water vapor migration, making them suitable candidates for medical packaging. New developments in the area of flame retardancy will be discussed in this paper.

INFLUENCE OF THE INJECTION MOULDING PROCESSING PARAMETERS TO THE MECHANICAL PROPERTIES OF MICROCELLULAR FOAMED POLYCARBONATE

A.K. Bledzki , M. Rohleder , H. Kirschling, May 2010

Since many years microcellular foamed materials have been produced. The advantages are all well known but to improve the properties of the material it is necessary to understand the interrelationship between the morphology and the mechanical properties. Furthermore it is important to know how the processing parameters influence the morphology and the properties of the produced part. By understanding the relation between processing parameters and the consequential properties it becomes possible to create microcellular foamed parts with exactly defined properties. Equations by means of linear regression were created and the main influence processing parameters extracted. Out of this it is possible to define a processing window which leads to best mechanical properties for each specific load type.

INFLUENCE OF THE INJECTION MOULDING PROCESSING PARAMETERS TO THE MECHANICAL PROPERTIES OF MICROCELLULAR FOAMED POLYCARBONATE

A.K. Bledzki , M. Rohleder , H. Kirschling, May 2010

Since many years microcellular foamed materials have been produced. The advantages are all well known, but to improve the properties of the material it is necessary to understand the interrelationship between the morphology and the mechanical properties. Furthermore, it is important to know how the processing parameters influence the morphology and the properties of the produced part. By understanding the relation between processing parameters and the consequential properties, it becomes possible to create microcellular foamed parts with exactly defined properties. Equations by means of linear regression were created and the main influence processing parameters extracted. Out of this it is possible to define a processing window which leads to best mechanical properties for each specific load type.

APPLICATION OF TAGUCHI METHOD ON NYLON6 NANOCOMPOSITES THIN WALL IN MOLD DECORATION MOLDING

Kapil C. Sheth, Robert R. Gallucci, Gurulingamurthy Haralur, May 2010

Nylon6 and Nylon6 nanocomposites (addition of 2.0 wt% and 4.0 wt% Montmorillonite) were used as molding material for in mold decoration (IMD) molding (square plate specimen with thickness of 1.0mm). The Taguchi method with orthogonal arrays was used to determine important factors affecting ink washout in thin wall IMD molding. It was found that the significant contributing factors in the descending order were injection speed (29.30%), nanocomposites additives (21.62%) and film type (15.26%); moreover, higher melt temperature, higher mold temperature and lower injection would increase moldability for Nylon6 nanocomposites (4.0 wt%) combined with 0.125 mm thick PC film.

EFFECT OF CLAY ON THE MECHANICAL / THERMAL PROPERTIES OF MICROCELLULAR INJECTION MOLDED LOW DENSITY POLYETHYLENE NANOCOMPOSITES

Peming Hsu , Jui-Pin Yang , Shyh-shin Hwang , Ying-Zhong Lai, May 2010

In this study, the effect of MMT content on the mechanical/thermal properties of low density polyethylene (LDPE) was studied. Maleated LDPE was compounded in a kneader with different montmorillonite (MMT) loadings.The maleic anhydride(MA)-grafted LDPE (LDPEgMA) nanocomposites were then molded by conventional and microcellular injection molding process. The effect of MMT content on the mechanical/thermal properties was investigated.The results showed that LDPEgMA nanocomposites (up to 5 wt.% MMT loading) have better tensile strength and wear resistance than their neat counterparts, using either the conventional or microcellular injection molding process. In addition to the mechanical properties, the LDPEgMA nanocomposites also have better foaming property (i.e., cell size and cell density) than their neat counterparts. The thermal stability of the LDPE material is also improved by the addition of MMT.

INFLUENCE OF SURFACE TEXTURE ON SCRATCH BEHAVIORS OF INJECTION INFLUENCE OF SURFACE TEXTURE ON SCRATCH BEHAVIORS OF INJECTION

Naveen K. Singh, Alan Lesser, May 2010

A standard scratch test based on ISO19252 was conducted with injection molded plastics using a spherical shape scratch tip with a diameter of 5 mm. Effect of spherical patterns distance on scratch behavior was investigated. The spherical pattern size was 0.8 mm in diameter and the distance was varied in 0.5, 0.9 and 1.2 mm. The critical normal load for onset of pattern shape change decreased with increasing distance between spherical patterns, i.e. shorter distance led to higher scratch resistances. Polarizing optical microscope (POM) observation showed that yielded zone size in sub-surface increased as the distance between spherical patterns increased.

THE RELATIONSHIP BETWEEN TUBULAR LOW-DENSITY POLYETHYLENE (LDPE) BLOWN-FILM OPTICS AND MOLECULAR STRUCTURE

Jaap den Doelder , Teresa Karjala , Mehmet Demirors, May 2010

LDPE product development is accelerated by understanding the relationships between process, structure, rheology, fabrication, and end-use properties. This paper describes the data analysis of a large set of tubular LDPEs.Focus is put on film optics in relation to structure, including fabrication condition effects. It is found that haze, gloss, and clarity are largely independent in the good-optics range. Good optics is found to be related to narrow molecular weight distribution, whereas melt index and density play a secondary role. It is advised to use topology-generating models to further quantify structural features in relation to optics.

3D FORMING OF GENUINE WOOD VENEER AND IN-MOLD LAMINATION WITH WOOD-PLASTIC-COMPOSITES (WPC) IN ONE INJECTION MOLDING CYCLE

C. Funke , H. Potente , V. Schöppner, May 2010

This paper covers the development of an innovative composite material together with a specialized process for 3D formed parts made of Wood-Plastic-Composites (WPC) with genuine wooden surface. Special preprocessed veneers are 3D formed and in-mold laminated with polypropylene-based WPC simultaneously. Questions relating to adhesive strength and warpage of the two components and the injection molding of WPC are analysed and discussed. Another key issue is the scientific derivation of the rheological behaviour of WPC, the optimization of the injection molding process for WPC and the analysis of the warpage between the two materials veneer and WPC

DEVELOPMENT OF AN ALTERNATIVE PROCESS TECHNOLOGY FOR MULTI-COMPONENT INJECTION MOULDING

R. Kleeschulte , H. Potente, May 2010

Multi-component injection molding technology is increasingly developing into a key technology in polymer processing. A common problem encountered with the overmoulding process is that the aspired bond strength cannot be achieved. Based on consolidated findings from the fields of welding and refining of plastic parts, a number of different approaches will be investigated, particularly with regard to improving the process. The first step involves a higher temperature level inside the core than in the standard process. According to the theories of diffusion and adhesion, a higher temperature will improve the diffusion or wetting. The second step is a modified surface structure between the two components. Coated and eroded exchangeable disks have an influence on the peel stress. The results are shown in this paper.

RECENT ADVANCES IN JOINING OF POLYMER AND POLYMER-METAL HYBRID STRUCTURES BY FRICTION-BASED SPOT WELDING TECHNIQUES

Jeffrey C. Haley, Jeff S. Borke, May 2010

Friction Stir Spot Welding (FSSW), Friction Spot Welding (FSpW) and Friction Spot Joining (FSpJ) are new joining technologies for lap joint connections. Due to the increasing importance of thermoplastics and lightweight alloys in industrial applications, such as for the automotive and aircraft industries, efforts have been made to develop new joining methods for similar and dissimilar polymer/metal structures. This study introduces these joining technologies and reports about recent developments with PMMA and PPS-GF / Mg hybrid joints. Good strength and improved microstructure were achieved in the joints. These positive characteristics illustrate the potential of these techniques as an alternative fabrication technology.

THE INTERPLAY BETWEEN POLYMER POLYDISPERSITY AND FILM GAUGE IN HDPE BARRIER FILMS: HOW POLYDISPERSITY CONTROLS THE GAUGE DEPENDENCE OF FILM BARRIER PROPERTIES

Jeffrey C. Haley , Jeff S. Borke, May 2010

We studied the barrier properties of films produced from eleven different HDPE resins as a function of film thickness. The gauge-normalized water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) depend on film thickness for samples with a larger z-average molecular weight and the gauge-normalized WVTR and OTR are independent of film thickness for samples with a smaller z-average molecular weight. We also find that WVTR tracks with the average degree of crystallinity of the film as determined by DSC and that the dependence of film crystallinity on film thickness apparently accounts for the dependence of WVTR on film thickness.