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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A key element in successfully molding high quality PET (Polyethylene Terephthalate) preforms is the delivery of molten plastic to each cavity in a rheologically similar manner. This has been a significant challenge in light of the shear/viscosity and crystalline behavior of bottle grade PET in its molten state. This paper will review the economics of molding PET preforms, the impact of improved performance on profitability, design philosophies for molding PET preforms and hot runner technologies that are now available to confront historical issues in the PET preform molding process. These new technologies, applied to molding PET preforms, will help converters improve their bottom lines.
Agricultural mulch films that are used to cover soil of crop rows contribute to earlier maturation of crops and higher yield. Incineration and landfill disposals are the most common means of disposal of the incumbent polyethylene mulch films; these are not environmentally friendly options. Biodegradable mulch films that can be rototilled into the soil after crop harvest are a promising alternative to offset problems such as landfill disposal, and film retrieval and disposal costs. In this study, an in-house laboratory scale test method has been developed in which the rate of disintegration, as a result of biodegradation, of films based on polyhydroxybutanoic acid (PHB) copolymers were investigated in a soil environment using residual weight loss method. The influence of soil composition, moisture levels in the soil and industry-standard anti-microbial additive in the film composition on the rate of disintegration of PHB copolymer films will be discussed.
Dielectrostriction is a rheodielectric phenomenon that relates the variation of dielectric properties of a material with deformation. For an initially isotropic material, two independent material coefficients, ?ñ1 and ?ñ2, are required to describe dielectrostriction in terms of strain. Deformation affects a materialƒ??s dielectric properties in two ways: (a) by introducing anisotropy in the material, which is characterized by ?ñ1; and (b) by changing the volume density of the polarizable species, which is associated with 1ƒ?3?ñ1 + ?ñ2. Purely viscous fluids will remain isotropic during any flow-induced deformation and therefore the coefficient, ?ñ1, is always zero. In this paper, the dielectrostriction effect is studied on viscoelastic materials with varying elasticity. The coefficient, ?ñ1, is measured by a planar capacitance sensor rosette. Also, the relationship between the coefficient, ?ñ1, and the material elasticity is discussed.
Potentially toxic chemicals such as heavy metals phthalates and halogenated organic compounds are currently found in many consumer products and are cause of great concern. The authors employed XRF methodology in extensive testing for hazardous chemicals contained in plastic components of over 450 domestic and imported 2006-2009 model year cars in 130 children’s car seats and 3 700 (2007-2008) children’s products including toys. Over 13 000 individual samples are included in the database. Handheld and non-destructive X-ray Fluorescence Spectroscopy (XRF) yields data of most elements at ppm and higher levels with good correlation to time consuming and destructive traditional analytical techniques. The presentation of data includes analysis of trends in the use of brominated flame retardants (BFRs) PVC lead and heavy metals in plastics with emphasis on relevance to public health. Methodologies to translate the test data into a relative product rating system have been developed and published for consumer use (see healthytoys.org and healthycars.org).
Potentially toxic chemicals, such as heavy metals, phthalates, and halogenated organic compounds are currently found in many consumer products and are cause of great concern. The authors employed XRF methodology in extensive testing for hazardous chemicals contained in plastic components of over 450 domestic and imported 2006-2009 model year cars, in 130 childrenƒ??s car seats, and 3,700 (2007-2008) childrenƒ??s products including toys. Over 13,000 individual samples are included in the database. Handheld and non-destructive X-ray Fluorescence Spectroscopy (XRF) yields data of most elements at ppm and higher levels with good correlation to time consuming and destructive traditional analytical techniques. The presentation of data includes analysis of trends in the use of brominated flame retardants (BFRs), PVC, lead, and heavy metals in plastics with emphasis on relevance to public health. Methodologies to translate the test data into a relative product rating system have been developed and published for consumer use (see healthytoys.org and healthycars.org).
As the use of tandem extrusion lines for producing quality structured foams expands, the need for better cooling screws is receiving increased attention. In a tandem extrusion line, the role of the cooling extruder is to homogenize the melt, and to efficiently remove heat from the gas-laden melt, without excessive viscous heat generation. There are a variety of design elements that are commonly applied to cooling screws, but the use of multiple flights is the most common. However, it is not clear how multi-flight configurations lead to better overall performance. This paper presents a numerical study of the effect of multi-flight screw configurations on the homogenizing and cooling of a polymer melt. Various characteristics of the melt flow and heat transfer in multiflight screws are compared to those of a corresponding single-flight design.
Poly(ethylene terephthalate) [PET] from off-gradesof industrial manufacturer was depolymerised usingexcess ethylene glycol [EG] in the presence of metalacetate. Influences of the reaction time volume of EG and catalysts concentrations on the yield of theglycolysis products were investigated. In this study wehad three 3-level factors for reaction time volume ofEG and catalysts concentrations on the basis ofTaguchi's statistical method. The optimal conditionsare reaction time of 3 h molar ratio (EG to PET) of 5 weight ratio (catalyst to PET) of 0.25 wt%. Theglycolysis products were analysed for hydroxyl valueand identified by DSC and VPO. The optimum samplewas used to produce unsaturated polyester resin [UPR]by maleic anhydride [MA]. The samples alsocharacterized well by FT-IR 1HNMR and 13CNMR.
Traditionally pultrusion dies have been fabricated using conventional machining. However rapid tooling techniques permit the construction of complex preform and die cross-sections which may be used to pultrude interlocking fastenerless joint designs. For rapid construction of naval structures like ship deckhouses 3-D printing a rapid prototyping technique was utilized to develop a new snap fit joint pultrusion die. 3-D printing required approximately 115 man-hours less than conventional machining. Furthermore an innovative and cost effective multi-modular die has been developed and implemented in manufacturing a snap fit joint for scale ship deck houses.
Traditionally, pultrusion dies have been fabricated using conventional machining. However, rapid tooling techniques permit the construction of complex preform and die cross-sections, which may be used to pultrude interlocking, fastenerless joint designs. For rapid construction of naval structures, like ship deckhouses, 3-D printing a rapid prototyping technique was utilized to develop a new snap fit joint pultrusion die. 3-D printing required approximately 115 man-hours less than conventional machining. Furthermore, an innovative and cost effective multi-modular die has been developed and implemented in manufacturing a snap fit joint for scale ship deck houses.
The object of this experiment is to investigate the effects of gate design, shear history, processing conditions, and melt rotation on gate blush and tiger striping. The part being molded and examined is a .101 meter impact disk. The parts were measured using a visual measurement system based on the quality of the surface finish. The materials in question are TPE, PC/PET blend, PC/ABS blend, and Acetal. Shear history increases gate blush on molded parts. Injection velocity alters tiger striping while a low melt temperature eliminated tiger stripes on the part.
Reactions were performed between a low molecular weight, highly functionalized polyethylene and a polyetherdiamine, in a resin kettle and a melt blender. In both cases, a one-component reactive prepolymer was formed. The prepolymer converted into a thermoset on subsequent melt processing at elevated temperatures. The low viscosity of the starting materials and the reactive prepolymer allows mixing and molding of these materials using equipment that works at significantly lower shear and pressures than conventional extruders and injection molding equipment.
In the field of tribology, scratch, mar and abrasion are often misconstrued as interchangeable terms. Using the current state of the art as a basis, a new testing methodology has been devised that allows abrasion resistance to be evaluated and defined in a unique way.Model thermoplastic olefins with 'good' and 'poor' surface damage resistance were tested for abrasion resistance using an adaptation of a standardized scratch testing methodology. It will be shown that changes in gloss and surface roughness show a positive physical correlation. Novel software for automatic tribological analysis will also be introduced.
We have studied the properties of MWCNT composites based on a polypropylene (semi-crystalline) and a polycarbonate (amorphous) matrix. Nanocomposites were prepared under different mixing conditions by diluting highly concentrated masterbatches. To promote nanotube dispersion in polypropylene nanocomposites and in order to investigate the effect of dispersion level on the properties of nanocomposites, different types of maleic anhydride grafted polypropylene were used including Polybond PB3150, Polybond PB3002 and Epolene E43. The state of dispersion was further analyzed by Scanning Electron Microscopy (SEM). The electrical percolation threshold of the PP/MWCNT composites is somehow less than that of the PC composites; however, the percolation threshold and the conductivity level above the threshold are completely dependent on nanotube dispersion in nanocomposite. Based on DSC results, the crystallinity of PP/MWCNT samples increases with the MWCNT content.
Pressure is a critical parameter that affects the degree of supersaturation within a polymer-gas solution when foaming. In most previous studies on cell nucleation, a uniform pressure throughout the solution was assumed. Although this assumption may be acceptable when no nucleating agent has been added, its validity is questionable when nucleating agents are present. The discontinuity at the interface between the nucleating agent and surrounding material is a potential heterogeneous nucleation site, and so the stress field around a particle will be different from the bulk. In light of this, this paper presents a numerical analysis to investigate the pressure profile around cell nucleating agents. Such an investigation is expected to provide new insights to understand cell nucleation phenomena.
Innovative electrospinning techniques were explored to facilitate the production of large electrospun silk mats for applications related to wound dressings. Limitations experienced producing experimental grade materials were attributed to the intermittent polymer spray inherent in the electrospinning process. Applying fundamental electrodynamics, electrostatic field gradients generated at alternative equipotential node points on a modified potential plate were shown to stably displace and orient the spinning fiber on specific vector beyond the material damaging spray zone. High speed photography and electrostatic field gradient simulation verified a sixteen degree angular displacement of the electrified fluid jet as the equipotential was repositioned from the center to the edge of a disk shaped potential plate. Additionally, the symmetrical displacement signature around the potential plate enabled concurrent multi-spinning with one commercial apparatus. This novel electrospinning approach provides the ability to create large experimental grade electrospun silk materials suitable for biocompatibility assessments related to wound dressings and establishes manufacturing standards by which electrospun silk materials may be commercially produced.
The effect of panel thickness on impact properties of ionomers, which exhibit self-healing properties, was investigated for the purpose of determining the critical thickness that is required to observe self-healing behavior upon impact of various ionomers and the unionized base resin. Self-healing closure of the impact damage zones occurred in a panel thickness range of 5.5 ƒ?? 6.0 mm and greater for all ionomers as well as the unionized base resin investigated regardless of phase morphology, counter-ion used for neutralization, and the percent neutralization of the ethylene-methacrylic acid copolymer (EMAA) base resin. Furthermore, with an increase in panel thickness there was an increase in impact energy absorbed, however, the slope of the curve shifts at a panel thickness of 0.9 mm and 8.5 mm. The shift in slope is attributed to a shift from brittle to ductile failure and a larger to smaller overall damage zone, respectively.
Many consumer products have a complex construction with multiple types of materials. This makes it difficult to recycle the products if the materials are not easily separated. A mixed recycling study was conducted for a particular multi-material product to determine the degree of material segregation required to obtain a recycled feedstock with useful properties. Toothbrushes were selected as the product for this study. These were collected from a commercial take-back program and were separated by material. Different formulations were compounded with virgin material at varying percentages and molded into ASTM test specimens for mechanical property testing.
At Antec 2008, a new single screw compounder (SSE) was introduced with newly designed mixers along the screw. These mixing elements had spiral flutes with elongational mixing (SFEM). The Elongator, hereafter SFEM, demonstrated simple processing of RPVC powder with an increased output from the historic limit of 30 rpm to a faster speed of 180 rpm at only 174 ?øC, vented, starved or flood fed. There was no need for a vacuum hopper or crammer feeder with this simple screw design.This paper presents scale up work that was performed on a 2.5' extruder with the RPVC powder. The new SSE processed RPVC powder with an increase in screw speed to 70 rpm and output temperature of only 191 ?øC, nonvented, with screw cooling, and flood feeding.This paper also presents mixing tests performed with the smaller SSE using a newly designed SFEM (hereafter SFEM-II). Two tests were performed with the RPVC powder, one using 0.5% color concentrate and the other wood flour.
Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) are two major thermal analysis techniques which can be used for failure analysis of polymers and composites. DSC and TGA offer wealth of in-depth information related to the composition, processing, structure, and properties of the materials. Important thermodynamic and kinetic parameters that determine the performance and properties of products, such as glass transition temperature, melting and crystallization, crystallinity, degree of cure, thermo-oxidative stability, and material composition, can be obtained through carefully designed experiments using individual or combined testing of DSC and TGA.
The discovery of Olefin Block Copolymers (OBC) brought opportunities to develop novel soft compounds for the consumer durables market. These new soft compounds are primarily blends that include a rigid polymer, a rubber, and an oil. This work was aimed at developing fundamental understanding on morphology development of OBC/PP/Oil blends at two different oil levels. The results showed that mechanical properties are dominated by the development of two phase morphologies at low and high rubber volume fractions. A dynamic mechanical analysis at low strains showed that the storage modulus behavior at high rubber volume fractions could be explained with known composite models.
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Society of Plastics Engineers
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