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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Intelligent Guidance of the Melt Front in Injection Molding Machines
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.
Polyblends of Polyphenylene Ether with Styrene-Ethylene/Butylene-Styrene Block Copolymer
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.
Survey of Plastics Education in U. S. Colleges and Universities
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.
Survival of the Fittest: Utilizing E-Commerce as an Integral Part of Your Marketing Plan
Business-to-Business e-commerce has even greater potential than consumer focused e-commerce. We currently are in a transition from the Industrial Age to the Information Age. E-commerce is introducing new business models in many industries. This paper will describe how and why that is as well as how you can harness the power of the Internet as part of your marketing strategy and business development tools for the next decade.
Design of an Injection Mold with Removable Plates Using CAE
The objective of this work was to design a mold of normalized test specimen to evaluate mechanical polymer properties with removable plates to inject each specimen independently using computed-aided engineering (CAE). The design was validated through simulation program of the injection process C-MOLD. Four cooling systems, the position of the entrance and the percentage of shrinkage were evaluated. There were no differences between the cooling systems studied. The maximum shrinkage was less than 2% and no part warpage was observed
Design of an Injection Mold Using C-MOLD Software
The purpose of this paper was to design a security cap and its injection mold using CAD/CAE tools. C-MOLD and Pro/ENGINEER softwares and the Concurrent Engineering Method were applied. The part and its mold were successfully designed in only 20 weeks.
Dynamic Rheological Properties of HDPE/Ethylene-Alpha-Olefin Copolymer Blends
The blends of linear and branched polyethylenes have received much attention in recent years. Many studies have been carried out to evaluate the miscibility of these mixtures and its influence on the final properties. There still some degree of controversy on the issue of melt miscibility even though partial co-crystallization has been demonstrated for some of these systems.
Make Flat Sheet Using Contrabend Rolls
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."
Bubble Growth in a Solvent-Polymer Solution
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.
Flexible Polyolefins and Low Density Polyethylene Blends for Film Extrusion Applications
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.
Foamed Polymer Sandwich Composites Reinforced with Three-Dimensional Filler
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."
ANSI Standards Combined with European Hazard Ranking Methods Provide Plastic Web Processors with Powerful Tools for Enhancing Workplace Safety
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.
Continuous Polymerization of Polycaprolactone in a Modular Co-Rotating Twin Screw Extruder
Bulk polymerization of e-caprolactone (CL) has been carried out in a modular intermeshing co-rotating twin screw extruder using aluminum isopropoxide as a coordination-insertion" initiator under a range of processing condition including temperature profiles throughput and screw speed. This homo-polymerization was investigated for various ratios of monomer to initiator. GPC analysis demonstrated that significant quantities of oligomers were produced together with high molecular weight polymer under different reaction temperatures. For continuous polymerization at 130°C using a modular co-rotating twin screw extruder high molecular weight up to 200000 were produced without substantial oligomers by increasing the ratio of monomer to initiator."
Surface Delamination of an Injection Molded Medical Device Using Flexible PVC
An autoclavable medical device was designed using flexible PVC. The device was injection molded and subsequently was exposed to steam autoclaving. Surface delamination was observed in the adjacent area of the gate. Investigations on material properties, pigment dispersion, and residual stresses were conducted. It appeared that by simply controlling the molded-in stresses, the defect could be minimized. In a Design of Experiment (DOE) study, the key molding parameters were identified.
Rheology of Randomly Branched Polymers
The molecular structure of randomly branched polymers is understood using percolation theory. Once the chain length between branch points and the extent of reaction relative to the gel point are specified by synthesis, both the molecular structure and the linear viscoelastic response can be determined using simple models. We demonstrate these ideas using randomly branched polymers with known chain lengths between branch points. Then we exploit this finding to characterize the chain length between branch points for polyethylenes from knowledge of their weight-average molecular weight and zero-shear-rate viscosity.
Analysis of the Flow Front Profile by In-Line Visualization of the Filling Stage
Using a special tool designed with the purpose to visualize the melt flow across the thickness dimension of the mold cavity [l], an experimental investigation was made to assess the polymer melt behavior in specific processing conditions. The aim of the work is to visualize some unexpected flow front behaviors in the selected injection molding conditions. The design of the mold enables to adjust the location of a special glass window along the material flow path. The mold feed is based on a hot runner system. The results presented are direct visualization images of the melt front.
Fracture and Fatigue Properties of Injection-Molded Short Glass Fiber-Reinforced Poly(cyclohexylene-dimethylene-terephthalates)s (PCT) as a Function of Molding Conditions
Summary The static fracture toughness (Kc) and fatigue crack propagation (FCP) behavior of injection-molded short glass fiber (GF) reinforced poly(cyclohexylene-dimethylene- terephthalate) (PCT) composites were determined as a function of material parameters (with and without flame retardant) and molding conditions (injection speed and plaque thickness were varied). The anisotropy in the fracture mechanical response of GF-PCT, determined on compact tension (CT) specimens notched along and transverse to the mold filling direction (L- and T-notching, respectively) was interpreted by considering the molding-induced microstructure (GF layering and alignment). It was established that the effect of injection molding speed is negligible at the same specimen thickness. By contrast, increasing thickness strongly affected the GF structuring and thus the related fracture mechanical response.
Toughening of Epoxy Resins by Partially Decomposed Polyurethane Waste
Hygrothermally decomposed polyurethane (HD-PUR) of polyester type has been used as a cost-efficient impact modifier in tri- and tetrafunctional epoxy (EP) resins. The PUR modifier was added between 5 and 80 wt.% to the EP prior its crosslinking with a diamine compound (Diaminodiphenylsulphone, DDS). The fracture toughness (Kc) and -energy (Gc) of the modified resins were determined on static loaded compact tension (CT) specimens at ambient temperature. The mean molecular weight between crosslinks (Mc) was determined from the rubbery plateau modulus of dynamic mechanical thermal analysis (DMTA) spectra. The change in the Kc and Gc as a function of Mc followed the prediction of the rubber elasticity theory. The efficiency of the PUR modifier was compared with that of a carbonyl terminated liquid nitrile rubber (CTBN). DMTA and fractographic inspection revealed that the PUR modifier was not only present in a dispersed phase of the EP matrix but participated in the build-up of the EP crosslinked network structure. Thus HD-PUR works as active diluent and phase separating additive at the same time. As HD-PUR can be regarded as an amine-functionalized rubber, it was used as hardener alone (by replacing DDS) in some EP formulations.
Thermoplastic Elastomers of Poly(ethylene terephthalate) and Grafted Rubber Blends
Thermoplastic elastomers containing 50 wt.% poly(ethylene terephthalate) (PET) and 50 wt.% rubber with and without glycidyl methacrylate (GMA) functionalization were produced by melt blending. In some cases the method of dynamic curing was also adopted. The static tensile properties and dynamic-mechanical thermal analysis (DMTA) response of the systems were studied. The phase morphology of the blends was of interpenetrating network (IPN) type according to fractographic and DMTA results. It was established that the best mechanical performance exhibited those blends which contained a GMA-grafted nitrile rubber (NBR-g-GMA). The effect of dynamic dynamic curing, for which a two-step procedure was developed, was marginal. Cost reduction opportunities of the recipes by using high-volume polyolefins have also been explored.
Structure/Process/Part Quality Relationship for BMC Injection Molding
Thanks to its qualities and performances, BMC injection molding has nowadays reached a satisfactory maturity level. But nevertheless, this technology remains complex. Thus, the aim of the present study is to determine the technological parameters capable of improving the surface quality of the molded parts. The experiments are performed with a semi-industrial mold for rectangular plate. A first Taguchi Design Of Experiments was used in order to quantify the effect of the feeding, filling, holding and curing parameters on the surface quality. It was completed by a second hybrid DOE, the aim of which was to estimate more precisely the incidence of the main key factors (mold surface temperature, injection flow rate and holding pressure) previously identified. These results have been then confirmed with a different gate location and a modified geometry.
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