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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Blocking of LLDPE Films - Effect of Surface Morphology
The mechanism of LLDPE blown film blocking has been investigated. Film specimens exhibiting different levels of blocking force were fabricated using resins with various molecular characteristics. The film surface morphology and the chemical composition were studied. Atomic Force Microscopy observations allowed to link clearly blocking with the formation of a soft layer at the films interface. This layer is made of amorphous PE chains, migrated from the bulk of the film during conditioning at 60°C. No evidence of co-crystallisation at the interface was observed. The chemical nature of the soft layer has been derived from its mechanical properties. A predictive model for film blocking is proposed based on a single molecular parameter.
Blown PP Based Coextruded Films as an Alternative for the Flexible Packaging Industry
New PP resins are available in the market allowing for the production of coextruded or monolayer blown films with particular properties. Some advantages are associated with lower resin densities and higher modulus in comparison with other commodity resins. Currently, PP also has a significant price advantage in many market. High stiffness and high clarity can be achieved when PP is coextruded with PE, allowing for thickness reduction depending on the final application. This paper presents a comparison of mechanical and optical properties among structures using different polypropylene resins and different layer thickness.
Capacitive Sensing Dielectrometers for Noncontact Characterization of Adhesives and Epoxies
Recently developed capacitive sensor geometries provide new capabilities for characterization and manufacturing quality control of low conductivity dielectric materials. Novel geometries incorporating multiple sensing elements within a single footprint permit profiling of the properties with depth (such as dielectric constant, conductivity, loss tangent, complex permittivity and layer thicknesses) from one side of the material. These sensors permit absolute property measurements with minimal calibration requirements and noncontact measurements where the air-gap thickness is also being measured. This paper reviews the sensing technology and its use in cure monitoring of epoxies and adhesives in thick and thin film applications.
CAPE-VIT - A Different View of Education in Plastics Design
Education for the growing needs of the plastics industry is recognized as needing a different approach that will enable a quicker integration of the graduates in the working world. Under the auspices of the EU programme Leonardo da Vinci a group of universities and institutions developed a course programme and structure for preparing engineers with skills for plastics design and processing with a sound awareness of the environmental issues. Specific characteristics of the course are the project driven methodology and the integration of training periods in the industry as from the first year of the four-year long course.
Cartography in Flatland: An Overview of Analytical Techniques for Characterizing Nanocomposite Morphology
The performance advantages of certain commercial nanocomposites based on montmorillonite clays in thermoplastics are claimed to be great and the markets for these advantages large. Despite this commercial driving force, only a very small number of commercial nanocomposites are available because it has proven difficult to achieve the proper morphology for performance enhancement. Understanding, characterizing and manipulating nanocomposite morphology will play a crucial role in developing commercial thermoplastic nanocomposites. This technical presentation will outline the use of specific analytical techniques to characterize the morphology of polymer-clay based nanocomposites. It will begin by identifying the morphological information necessary in order to make better performing nanocomposites. The various techniques of x-ray diffraction, electron microscopy, optical microscopy, dynamic light scattering, atomic force microscopy, infrared spectroscopy, dielectric relaxation spectroscopy, and NMR will be described as they apply to nanocomposites.The talk will identify the deliverables of each technique, potential sources of analytical services for the technique, and special considerations associated with applying each technique to nanocomposites. The talk will conclude with a plea for the development of new techniques to provide information currently unavailable but necessary in the custom design of novel nanocomposites.
Cast-In-Place (CIP) for Joining and Repairing Live, PE, Gas Lines - II. Process Development
The term cast-in-place (CIP) describes a method for casting a non-leaking sleeve of polyethylene (PE) around the butted ends of PE pipes while the joint is leaking air at pressures up to 582 kPa. Mold development involved flow-through or vented molds with the latter providing better results with smaller injection charges. Sound sleeves were cast on pipe diameters ranging from 2.5- to 10-cm (1- to 4-in.) SDR. Aged pipe that had been buried for years was successfully joined to new yellow pipe material. Contaminants such as dissolved natural gas in the pipe wall or a solution of anti-static agents generate joints with inclusions or bubbles although strengths were good.
Cast-In-Place (CIP) for Joining and Repairing Live, PE, Gas Lines - III. Repair of Holes
The cast-in-place (CIP) approach was adapted to a simplified process for repair of holes in polyethylene (PE) pipes. The approach involves clamping an elastomerlined clamshell around the damage and, after the pressurized flow has been stopped, embedding the clamshell in a shell of PE. This work defines:Design aspects of a low-profile steel clamp including examination of several elastomeric gasket materialsDamage types that can be sealed including roughened and damaged surfacesInexpensive and portable methods for strapping the clamp securely around large holes to seal leaking gas under substantial pressureSuitable lengths for the clamp and the PE shell that is molded around it.The overall approach works quite well and clamp designs were found that will seal leaking gas at pressures up to 770 kPa. The clamp is capable of taking flattened pipe and rounding it as it seals holes that are up to 8-cm long in 6-cm diameter SDR-11 gas pipe. Clamp lengths should be no more than 1/3 the length of the cast PE sleeve.
Catastrophic Failure of the No-Slip Condition at the Wall during Torsional Flows and Development of Gross Surface Irregularities during Capillary Flow of Three Polymers
Wall slip behavior of three polymers was studied using flow visualization in cone-and-plate and parallel plate flows. The straight line marker technique and high speed cinematography were used to investigate the temperature-dependent wall slip behavior of a high density polyethylene, HDPE, a polydimethylsiloxane, PDMS, and an oxetane based thermoplastic elastomer, BAMO/AMMO. Capillary rheometry was also used to obtain data on the flow curves and to study the surface topology of extrudates. The straight line marker technique allowed the precise determination of the critical shear stress values for the onset of the catastrophic failure of the no-slip condition, which were determined to be 0.22 MPa for the HDPE and 0.073 MPa for PDMS, both of which were independent of temperature. In the vicinity of these critical shear stresses the extrudates of HDPE and PDMS exhibited surface distortions during capillary flow. The thermoplastic elastomer, BAMO-AMMO, on the other hand, did not exhibit any catastrophic failure of its no-slip condition and the surfaces of its extrudates remained smooth even at relatively high shear rates during capillary flow.
Cellulose Fiber Reinforced Polypropylene: Compounding and Properties Study
The physical properties and processing limitations of polypropylene copolymer compounded with hardwood and softwood cellulose fiber were investigated in this study. The use of maleic anhydride grafted polypropylene as a coupling agent between the cellulose fiber and the polypropylene copolymer was also explored. The addition of the maleic anhydride grafted polypropylene showed improvements to the tensile, flexural, izod impact, and heat deflection temperature properties of the cellulose fiber reinforced blends. The performance properties of the cellulose fiber reinforced materials are also compared to polypropylene blends utilizing more traditional thermoplastic reinforcements: glass fibers, talc, and wollastonite.
Challenges in Winding Flexible Packaging Film
Every Flexible Film Producer is faced with the challenge of producing quality rolls of film products. This paper will assist in overcoming the challenges in winding flexible packaging films. It addresses the definition of a quality roll of film and the importance of inwound tension in consistently producing good quality rolls. It then discusses the winding principles used on all winders to control inwound tension or roll hardness. It explains how to determine the proper amount of web tension for various types of films and the principles of nip and gap winding. Then the basic types of center, surface and combination center/surface winders will be compared with the advantages and disadvantages of each. After the discussion of how roll hardness is achieved, methods of measuring roll hardness are presented. Finally, other roll defects to avoid in producing quality rolls of film will be listed and the book Roll and Web Terminology" will be brought to the audience's attention for them to learn more about the causes and cures of common roll and web defects."
Chaotic Mixing as a Means to Develop Nano-Scale Structures in Polymeric Materials
Nanoscale materials are often produced either by breaking down larger structures or by assembling them directly from their smaller constituents. Another approach is to establish processing conditions where initially large component domains intermingle and refine over time to eventually give materials with nanoscale features. In this paper, the potential of chaotic mixing to develop in situ fine-scale structures and promote molecular-scale interactions are described. Due to induced chaotic motions, melt domains stretch and fold recursively. Structure is evolved in lieu of being broken down as occurs typically in common blending. Hierarchical associations among components can arise with relation to some natural materials. Examples of materials are shown that have been produced. Several opportunities are discussed that may allow the manufacture of bulk quantities.
Characterising the Biaxial Properties of Materials Used in Thermoforming and Blow Molding
In most thermoforming or blow molding processes a heated plastic sheet undergoes rapid deformation into the shape of a mold. Typically a wide range of deformation modes may be observed across its surface, ranging from planar through to equi-biaxial. Data from conventional uniaxial tests is often used to simulate this behavior, but it is recognized that neither the speed nor mode of deformation is correct. In this paper the development of a biaxial testing machine is described. Test results for a number of common materials are presented and the results are compared to uniaxial tests.
Characterization of Apparent Viscosity with Respect to a PVC-Wood Fiber Extrusion Process
Wood fiber-thermoplastic compounds were introduced into the marketplace during the mid-1990’s. These compounds are currently being molded or extruded into useful products.As these products grow in complexity, the variability within these compounds must necessarily be reduced in order to maintain or reduce scrap during these secondary processes. But just how much variability these processes can actually tolerate is a non-trivial problem involving design, process and material variables.This paper will discuss the results of a Design of Experiments conducted to determine the maximum apparent viscosity variability that a profile extrusion process is able to tolerate in a PVC-WF compound.
Characterization of Ethylene-Vinyl Chloride-Like Copolymers Synthesized by Ring-Opening Metathesis Polymerization (ROMP)
A series of chlorine containing ethylene copolymers with controlled molecular microstructure have been made using ring opening metathesis polymerization (ROMP). In contrast to traditional methods currently used in industry, this synthesis permits the control of the exact chlorine content along the macromolecular chain. In some cases, the placement of chlorine along the polymer backbone is also controlled. The properties of these ethylene vinyl chloride-like copolymers (EVC) are compared to traditionally chlorinated polyethylene (CPE) as well as to ethylene octene (EO) and ethylene styrene (ES), copolymers synthesized by metallocene catalysis.
Characterization of Fluorinated Polycarbonate Thin Films
SF6/Ar plasma treatment using an RF discharge was carried out for the surface fluorination of bisfenol-A polycarbonate films. The potential utility of this treatment for improving polycarbonate gas barrier properties was investigated. Treatment was done with variation on time exposure to plasma and SF6 concentration. Fourier transform infrared spectroscopy attenuated total reflection (FTIR-ATR), x-ray photoelectron spectroscopy (XPS), and contact angle measurements were used for surface characterization. It was found that plasma fluorinated surfaces lead to a considerable improvement on polymer gas barrier properties for all treatment conditions studied.
Characterization of Heat Sealing Part on Plastic Films
Mechanical properties of heat sealed part on plastic films consisting of oriented polypropylene (OPP) and cast polypropylene (CPP) films were investigated and the relationship between crystalline structure and the mechanical properties were discussed. The crystallinity of the heat sealed part affected the mechanical property. Consequently the high total crystallinity of both OPP and CPP gave the high mechanical properties, and also the orientation of the crystalline structure in OPP film was an important factor. The optimum condition for heat sealing was the temperature at which the highest crystallinity was obtained and also the orientation was not released.
Characterization of Metallocene EPDMs Crosslinked by Peroxide and ?-Radiation
Two metallocene EPDMs with the same weight fraction of ethylene were crosslinked by dicumyl peroxide and ?-radiation. Several amounts of peroxide were dispersed in a Leistritz corrotating twin-screw extruder at 85ºC, 55 rpm and 2 kg/h of mass flow rate. Besides, different ?-radiation doses were used. The gel content was determined in boiling decahydronaphtalene, and the crosslinking process was monitored by FTIR spectroscopy. The thermal properties were found by DSC and DMA. The mechanical properties, hardness (Shore A), compression set and tensile were also obtained.
Characterization of Molecular Weight Degradation of Polyamides by Gel Permeation Chromatography
Polyamides are susceptible to attack by environmental pollutants. The surface layer is degraded and the development of a critical thickness of this layer results in a catastrophic loss of mechanical properties. In this work nylon was exposed to nitrogen oxides and the fracture strength was measured. After a period of no change the fracture strength decreased dramatically. Exposed samples were microtomed and the molecular weight distribution of nylon was determined, as a function of depth from the surface, by Gel Permeation Chromatography (GPC). A critical depth for degradation was established beyond which the specimen exhibited unacceptably low fracture strength.
Characterization of Phase Partitioning of Additives in Rubber Modified Plastics
The phase partitioning of additives in polymer blends has a large impact on the performance of the blend. Since solubility characteristics and processing of the blends influences partitioning, it is necessary to be able to quantify the level of the additive present in each phase. An NMR method to quantify this partitioning has been developed and is based on the fact that the rubber phase and molecules dissolved therein, can be easily distinguished due to this phase’s enhanced motional characteristics. Examples will be presented for the quantification of phase partitioning within rubber modified styrenic materials.
Characterization of Phenolic Composites Reinforced with Jute/Cotton Hybrid Fabrics
The mechanical and dynamic-mechanical properties of novolac type phenolic composite reinforced with jute-cotton hybrid woven fabric were investigated as a function of fiber orientation and type. Scanning electron microscopy (SEM) was carried out to investigate the fiber-matrix adhesion. Results showed that the composite properties are strongly influenced by the test direction and yarns characteristics. The highest tensile, flexural and impact strengths and moduli (Young’s, flexural and storage) were found along the jute yarns direction and decreased with increasing test angle. Nevertheless, failure occurred in a catastrophic manner. Along the cotton yarns direction the composite exhibited a controlled failure mode. Jute fiber exhibited a better interaction with the matrix than cotton; the former has a higher irregular surface due to its multicellular nature, which promotes a mechanical adhesion at the interface. The combination of jute/cotton properties in this composite is suitable for lightweight structural applications, this is, jute promotes a higher reinforcing effect while cotton fiber avoid catastrophic failure.
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