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.
The evaluation and development of validated models for the nonlinear viscoelastic (VE) behavior of materials is an important area of research which has impact on a number of industrial processes including those in the food industry. Various nonlinear VE models have been developed over the years and evaluated for petroleum-based polymers; however, our understanding of the nonlinear VE behavior of biopolymers of industrial import lags our understanding of synthetic polymers. In the work reported herein, the nonlinear VE behavior of suspensions (20 % by weight in deionized water) of defatted oat flour, oat bran, barley flour, and oat flour were investigated. The rheological properties were measured using a Rheometrics Series IV controlled-strain rheometer equipped with a cone and plate fixture. The measurements were conducted at 23 ± 0.1°C. The rheological data were interpreted using a strain separable K-BKZ type (Wagner) model. The K-BKZ model was found to provide an accurate description of the rheological behavior of the four flour suspensions.
Thermotropic Liquid Crystalline Polymers (TLCPs) possess the lowest oxygen and humidity permeabilities among commercial polymers. However, TLCPs are highly incompatible with conventional polymers (polyolefins, polyesters), due to their unique composition and morphology. To compatibilize TLCPs with conventional polymers, a variety of polymers were evaluated having various functional groups like maleic anhydride, epoxy, acrylic acid etc. Using Ethylene Glycidyl Metha Acrylate (EGMA), three and five layer films containing TLCPs were prepared by conventional coextrusion. Experimental results have shown that a 10 ?m TLCP layer with polypropylene or polyester, increased the barrier to oxygen by a factor of 120 compared to neat polypropylene and by a factor of 40 compared to neat polyester, respectively. Furthermore, five layer films demonstrated higher barrier and stiffness properties compared to three layers films having identical overall composition. These unique barrier properties of TLCPs containing multi-layer films can compete commercially with EVOH and PVDC containing coextruded films, and can be further shaped by thermoforming and blow molding for high barrier packaging applications.
The fracture and deformation behaviors in polypropylene homopolymer toughened by metallocene catalyzed poly-ethylene elastomer are unknown. It is desired to understand the fracture and deformation mechanisms of PP toughened by the elastomer using standard puncture tests, J-integral fracture initiation toughness and tensile dilatometry. Preliminary results show that impact toughness of PP homopolymer was greatly enhanced in the presence of the elastomer. Volumetric strains were measured to estimate the degree of dilatational deformation relative to volume-conserving shear yielding.
In this work a wide series of copolymers of styrene and n-butyl methacrylate are investigated in terms of their physical and free volume properties. The study follows on from recently published work in which the relaxational and intermolecular coupling properties of this copolymer series was examined. It is found that even though the glass transition of polystyrene is higher than that of poly (n-butylmethacrylate), it has a lower density and higher molecular free volume fraction. The free volume fraction behaviour is complex, all copolymer values showing greater free volume fraction than the homopolymers. This correlates with a negative deviation over the Fox Tg behaviour of the copolymer. This is despite the moderately monotonic variation in the individual aspects of free volume (size and number of free volume pores). There are some dramatic changes in these properties at the extreme values of comonomer concentrations.
Nucleation results are presented for polyethylene sheet extrusion while using volatile carbon dioxide without any nucleating agent to study homogeneous nucleation. Since the extrusion pressure has to exceed the system pressure, mechanical superheat was calculated from the processing pressure. The experimental results show a different distribution from the conventional nucleation predictions, based on either chemical superheat or mechanical superheat. Also noted was the shear energy dependence. Various nucleation mechanisms are discussed to address the energy role played by shear in foam extrusion.
A mathematical model was developed for the simulation of film blowing including the effects of flow-induced crystallization, viscoelasticity, and film cooling. The microstructural model is based on the formulation of Doufas et al. Our model predicts the location of the freezeline naturally as a result of crystallization and the stresses at the frost line, which are closely related to the mechanical and physical film properties. Depending on the processing conditions, our model predicts uniaxial or biaxial film stretching.
The paper describes process monitoring applications by spectroscopic methods for polymer/additive analysis, polymer melt analysis, additive quantitation, QA/QC purposes, on-line compositional polymer analysis, in-situ reaction monitoring (cure kinetics, polymerisation, color designation, molecular interactions, monitoring of extrusion processes, real-time measurements and use of fiber optics. In particular, the current status of on-line multicomponent additive analysis in the polymer melt by means of UV-VIS spectroscopy will be illustrated.
This work investigates the influence of various extrusion parameters on the physical properties of rubber modified polystyrene sheets. The extrusion parameters under consideration are melt temperature, chill-roll temperature, line speed and sheet thickness. Optimum extrusion conditions for producing polystyrene sheet feedstock are discussed.
In the present paper the numerical simulation software 'NASPLAN' is presented allowing the intelligent guidance of the flow at the filling stage in an injection machine. NASPLAN allows the guidance of melt flow through prescribed p-q Time profiles. Especially the use of negative pressure is proved to be of great importance for the guidance of the Melt Front Advancement. This procedure leads to balance flow for complex geometry parts and multi-cavity molds. The primary objective of NASLAN compared to the conventional software is the improved part quality, by minimizing the flow defects (such as warpage, non-uniform shrinkage, sink marks). Additionally, the filling stage is completed in less time with the need of lower injection pressure. A simple part is adapted as a test case in order to visualize the effects of the above procedure.
Polyphenylene ether (PPE) and styrene-ethylene /butylene-styrene block copolymer (SEBS) were melt blended in ratios from 100/0 to 50/50. Balancing the molecular rigidity of PPE vs. the molecular flexibility of SEBS produced the expected qualitative effects on properties. Quantitatively, tensile modulus and tensile and flexural strengths gave monotonic curves for properties vs. polyblend ratio. All other properties - melt index, flexural modulus, ultimate elongation, impact strength, and heat deflection temperature - gave more complex curves. Practically, addition of SEBS produced significant increases in melt index, ultimate elongation, and impact strength, along with decreases in rigid properties.
Inquiries to 234 schools found 66 which offered courses in plastics, for a total of 2492 credit hours. Classifying these by subject matter showed 768 credits in polymer science, 324 in plastics in general, 125 in plastic materials, 238 in structure and properties, 568 in processing, 170 in product design, and 299 in other applications of polymers. The plastics industry began in 1868 (1) reached commodity status in the 1940’s (2), and has been growing in size and diversity ever since. The earliest plastics entrepreneurs came from other fields, and educated themselves. With the continuing and expanding growth in numbers of materials and processes, and in the intensity of polymer science and engineering, the need for higher education specifically in polymers and plastics has also grown exponentially.
Most plastic sheet produced today is made using a typical three-roll sheet stack. Material is passed through a preset gap between the rolls to form the final thickness of the sheet. The variation in this gap is related to the bending of the chill roll, which is a major factor in the gage variation of the sheet. Producing flat sheet" has always been the goal of the sheet producer. Until recently there has been little advancement in cooling roll construction as it relates to bending in the cross line direction. The Contrabend Reverse Bending Roll has been developed to greatly reduce the effect of roll deflection on sheet thickness variation. This work will explore the Contrabend concept and compare the bending to standard chill rolls."
A model for the growth of a non-ideal gas spherical bubble in a quiescent viscous liquid is presented. The growth of the bubble in the solvent-polymer solution is assumed to be controlled by momentum, heat, and mass transfer. Using the integral method, the differential transport equations were transformed into ordinary differential equations, which were numerically solved. The numerical results show that the pressure inside the bubble can increase to extremely high values before it decreases to a value close to the ambient pressure. It was also found that at low solvent concentrations heat transfer is not important, and the usual isothermal assumption can be applied. The relevance of this work to the process of polymer melt devolatilization is discussed.
This paper will cover the details of piece part design particular to the rotational molding process. Ribs, bosses, wall thicknesses, parallel walls, internal and external corners, openings, draft angles and undercuts will be discussed. Joining features, such as inserts, hinges and molded-in threads, will also be reviewed.
At first glance the Rotomold process is a fairly simple one. Its capabilities are exiting and have opened new avenues for creative industrial designs including complex shapes and rugged structural parts. Successful Rotomolded designs can be obtained by keeping a few guidelines in mind from concept through to product generation. This portion of the program will cover the areas that need to be considered during the design process. Items to be highlighted are basic design guidelines, features that can compromise, complicate and delay a project and what to ask a molder about specific designs.
Roto-mold is a versatile process which accomplishes many objectives which are difficult or impossible in other processes. It also has some special problems which complicate the aesthetic aspects of a design. Industrial designers working with engineers are uniquely qualified to design for this process.
Rotational molding is a plastics molding process that is noted for producing seamless, hollow parts. The process is capable of molding complex, thin-walled, hollow parts in small and extremely large sizes. This paper will explain what the process is, how it works, and why the manufacturers of durable plastic products should be aware of this process's impressive capabilities.
Polyethylene/i-PP(isotactic/crystalline) blends have been studied for years. However, these blends indicate a phase separation that detracts from compatibility and alters properties. It is expected that a combination of a novel less-crystalline polypropylene (FPO) with LDPE will allow for greater compatibility over a wide composition range. The LDPE/FPO blends appear semicompatible. Specifically, film extrusion processability increases, blocking decreases, along with better film appearance, and improvements in tensile strength without a decrease in flexibility. Alternatively, toughness, elongation and impact resistance increase. These enhanced properties may lend the blends to potential packaging applications.
Open-pore flexible polyurethane (PUR) foam with various pore sizes (1 - 8 mm) was used as filler to reinforce low-density closed-cell PUR flexible foam. The final composite has a sandwich structure, where the core zone has foam-in-foam" structure and skin zones are unreinforced PUR foams. Compared to the regular non-sandwich one-layer PUR flexible foam the sandwich composite exhibits improved mechanical properties: the support factor can be increased up to 65 percent and the compressive force deflection value can be increased almost 100 percent while the density of the composite increases only 25 percent."
A set of four safety standards for film, sheet, coating & laminating, and plastic web winding machinery has been developed under the sponsorship of SPI, and accepted as consensus standards by ANSI. The author reviews some of the more significant requirements of these standards. The standards represent an excellent tool against which to audit existing processing lines to identify hazards to personnel. The European Community has evolved a standard (EN 1050)*1 methodology for identifying and ranking the hazards in processing plants. This methodology is outlined in detail. By utilizing both of these approaches in tandem, hazards can be identified by the auditing against the appropriate ANSI standards, the identified hazards ranked for probable degree of harm to personnel, then safeguarding actions prioritized to obtain the most benefit from the minimum effort.
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Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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