SPE Library

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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Conference Proceedings

Characterization of the Interfacial Regions in Multilayer Coatings by NEXAFS Microscopy

Carl G. Zimba, Harald Ade, A.P. Smith, May 2000

Characterization of polymer interfaces is an important analytical need in many areas of technology. Many techniques, that provide the requisite spatial resolution, provide limited quantitative chemical information. On the other hand, techniques, that provide the desired level of quantitative chemical information, have limited spatial resolution. A relatively new analytical tool, Near-Edge X-ray Absorption Fine Structure (NEXAFS) microscopy [1- 4], provides a unique combination of chemical specificity and spatial resolution that is particularly well-suited for characterization of interfaces in polymer coating, blends and composites. In this paper, the application of NEXAFS microscopy to a multilayer polymer coating is discussed.

Rheological and Blown Film Characterization of Binary Blends of Metallocene-Catalyzed LLDPEs

Rajendra K. Krishnaswamy, David C. Rohlfing, Bryan E. Hauger, May 2000

The advent of metallocene catalyst technology has created several opportunities in the worldwide packaging film marketplace. In this work, we explore the effects of blending two metallocene-catalyzed LLDPEs of reasonably differing molecular weights. Specifically, the shear rheology, quiescent and shear-induced crystallization characteristics, and blown film performance were investigated as a function of blend composition. The presence of small amounts of longer molecules was found to have significant effects on the shear-induced crystallization kinetics and blown film orientation of the blends; this was explained in terms of an increasing number of extended chain nuclei for crystallization with increasing molecular weight. Lastly, the biaxial orientation features in the crystalline and non-crystalline phases of the blend blown films were also characterized and used in explaining the Elmendorf tear and dart impact performance of the blown films.

High Performance Rigid Flexible Combinations Made of Thermoplastic and Liquid Silicone Rubber

S. Boßhammer, E. Henze, May 2000

The injection molding of LSR represents a cost-efficient process for the production of high quality rubber parts for technical applications. Due to excellent material properties at extreme temperatures silicone rubbers offer various advantages for the production of soft/rigid combinations in comparison to thermoplastic elastomers. A new kind of LSR is presented which exhibits excellent adhesion properties to engineering thermoplastics. The process and the adhesion mechanism is designed in a way that no mold coating is required. A systematic analysis of the injection molding process points out suitable material combinations and indicates the influence of process parameters on adhesion strength.

Simulation of the Filling and Curing Phase in Injection Molding of Liquid Silicone Rubber (LSR)

E. Haberstroh, W. Michaeli, E. Henze, May 2000

The injection molding of Liquid Silicone Rubber (LSR) represents a cost-efficient process for the production of high quality rubber parts. Due to the extreme thermal conditions in the mold and the very low material viscosity a precise subvolumetric filling of the cavity is required to avoid flash formation. Modeling flow properties, curing characteristics and as the pvT-behavior creates the basis for an unified simulation of the injection molding process. The implementation of these models into a process simulation software makes it possible to calculate the filling phase considering a subvolumetric filling and to simulate the course of cavity pressure during the heating phase.

Optimising Nano Filler Performance in Selected Nylons

Charles J. O’Neil, Lawrence A. Acquarulo, Jr., Jianwei Xu, May 2000

A class of polymer materials having significantly improved properties has emerged. This class of material is being referred to as polymer nano composites. Typical of this class is the nano clay filled Nylon 6 family. We have recently found that by exposing the nano clay filled Nylon 6 materials to ionizing irradiation at low levels, 3 - 5 megarads that we further improve the flex-modulus. We have also found that this technology can be applied to Nylon 12. This technology is new to the 12.

Analytical System for Measuring Thermally Generated VOC Emissions from Polymers

Q. Xiang, S. Mitra, S. Dey, M. Xanthos, May 2000

An analytical instrument and procedures were developed to investigate the thermally generated VOC emissions from different polymers with a flame ionization detector (FID). This system was applied to estimate the upper limit of VOC emissions from recyclable 100% carpet residue by exaggerating its thermal exposure at a predetermined temperature. The pattern of VOC emissions was also studied for the 100% carpet residue as well as its composite (80% carpet residue + 20% virgin LDPE), and virgin resins (PP and LDPE).

Load-Carrying Ability of Injection Molded Products with Holes

Anton J. Heidweiller, Marcel J.M. van der Zwet, May 2000

The mechanical loadability distribution around a molded-in hole in a polystyrene plate has been analyzed using flatwise bending. Four different injection molding conditions have been applied. Birefringence measurements have been carried out to analyze the molecular orientation. The weld line is the weakest point, but the loadability reduction is small when it is related to the loadability perpendicular to the molecular orientation. Almost no effect of variation of process conditions was found.

Thin-Wall Injection Molding

S.C. Chen, H.S. Peng, L.T. Huang, C.T. Chang, D.Y. Wei, R.C. Ruo, May 2000

A precision monitoring system for high speed thin-wall injection molding machine was build so that hydraulic pressure, nozzle pressure, injection speed, filling to packing switchover and cavity pressures can be monitored during the whole molding process. Tensile test specimens of 2.5 mm, 1.2 mm, 1 mm and 0.8 mm thick were molded. It was found that as part becomes thinner the pressure prediction of CAE simulation gets worse and the errors range from about 50% to more than 100%. Filling time, proper filling to packing switchover, gate size, holding pressure and mold temperature were found to be the critical factors to successful molding and part quality. When part becomes thinner, residual stress is higher and affects part strength more significantly. When molding industrial thin parts, the residual stress concentrates around gate area, bosses and area where part thickness varies. Thickness reduction for the housing of computer dictionary can be achieved without great reduction in structural performance when localized thinning design is implemented.

Parison Wall Control Systems for Extrusion Blow Molding Equipment

Michael Thielen, May 2000

For a uniform wallthickness and layerthickness distribution even in complex-shaped blowmolded articles the parison has to be adjusted accordingly. Important developments in recent years were: • The Static Flexible Deformable Ring" SFDR and the "Partial Wall Thickness Control" PWDS for sophisticated articles. • The "Wallthickness Location Control" WDLS controls the actual position of wall thickness points which may "wander" e.g. due to changing raw material conditions. • The "Radial Wallthickness Control" RWDS for wallthickness control in bows of 3-dimensionally bent (3D-) parts. • A uniform layer thickness distribution in multilayer parts is achieved with a gravimetric throughput control system. "

Viscoplastic Analysis of Hot Embossing in Microfabrication

Yi-Je Juang, L. James Lee, Kurt W. Koelling, May 2000

In MEMS (micro electromechanical system), the hot embossing process has been mentioned as one of the major fabrication techniques, which is capable of making polymer microstructures for both low volume prototyping and high volume production. This is due to its simple process, relatively low tooling cost, high replication accuracy, and relatively high throughput. In order to minimize the process cycle time, the embossing temperature is set slightly above the glass transition temperature (Tg), while the de-embossing temperature is slightly below Tg. Since the polymer is deformed near Tg, its flow behavior during molding is substantially different from that at high temperature processes such as injection molding and extrusion. Also, the residual stresses resulting from the thermal cycle and compression force will profoundly influence the replication accuracy and optical properties of the molded parts. In order to establish the relationship between the residual stresses, replication accuracy, rheological behavior, and processing variables, we carried out a viscoplastic analysis and a series of hot embossing experiments. Two optical polymers, polyvinyl butyral (PVB) and polycarbonate (PC) were used in this study. The rheological property was characterized through both dynamic and transient shear viscosity measurements using the RMS-800 and a tensile test. Optical and SEM photos of replicates were taken at different processing conditions to determine the replication accuracy and birefringence pattern.

Biodegradable Laminates and Composites Containing Starch and Poly(hydroxyester-ethers)

R.L. Shogren, J.W. Lawton, W.M. Doane, J.L. Willett, May 2000

Poly(hydroxyester-ethers) (PHEE) were added to a variety of thermoplastic starch composites in order to improve the mechanical and water-resistant properties of these systems. Thin film coatings of PHEE's were found to adhere well to starch sheets and foams and provided resistance to cold water over short periods of time (hours-days). Adhesion was decreased by high water or glycerol contents in the starch and was increased by addition of partially hydrolysed polyvinyl alcohol. Extruded starch foam peanuts containing 5-20% PHEE were found to have a thin surface layer consisting mainly of PHEE. This probably explains, at least in part, why the starch/PHEE foams have a higher expansion ratio, greater water resistance and reduced friability compared to foams made from starch alone.

A Gram of Prevention: Additives to Improve UV Stability and Processability of Rotomolded Parts

Thomas Steele, Leonard Davis, May 2000

As the size of the rotomolding market increases, so do customers expectations for a longer service life and alternative resins. Small amounts of UV stabilizers and antioxidants can greatly improve the service life of a molded part as well as address some of the special challenges present in the rotomolding industry today. This paper will address the current issues in rotomolding and how UV and AO technology can be used to provide protection to the molded part.

Stabilization of TPE's

Leonard Davis, May 2000

A rational approach to the stabilization of thermoplastic elastomers (TPE's) is an extension of the known technology to stabilize the constituent polymer resins. Hindered amine light stabilizers and ultraviolet light absorbers are effective in polypropylene and polyethylene. They can also be used to stabilize multiphase TPE's, based on polyolefin copolymers, against the effects of long term exposure to light and heat.

Epoxy + Montmorillonite Nanocomposite: Effect of Composition on the Catalyzed Reaction Rate

Peter Butzloff, Nandika Anne D'Souza, May 2000

Differential scanning Calorimetry was used to determine the effect of incremental change in composition of alkonium ion substituted montmorillonite clay dispersed in thermoset epoxy with a simple diamine hardener. Catalytic effects due the reactivity of the reinforcement are shown to be variable with composition. Infra-red analysis of the epoxy monomer indicate a change in the morphology of the molecular reinforcement may alter the ability of the reactants to come into contact even before the chemical reaction has begun.

Simple and Concise Design Rules for Rapid Prototyping

Barbara J. Arnold-Feret, May 2000

Shortening the design cycle by using rapid prototyping is a standard for injection molding product creation throughout the world. Developing new products while being aware of each type of prototyping technology allows the designer to judge fit, function, esthetics, economics, and product features prior to cutting a production tool; saving money and time. The use of several prototyping processes, including stereolithography (SLA) and laser sintering (SLS) are detailed with updated information on new tolerance standards and new materials.

Predictive Control of Melt Temperature Incorporating the Effect of Screw Rotation

Rickey Dubay, Janet Beyea, May 2000

Controlling the plastic melt temperature along the barrel of an injection molding machine is important for the overall product quality. In order to achieve good control performance, other process interactions such as the rotating screw should be incorporated into the controller design. The use of model-based predictive control (MPC) allows coupled processes to be model in a dynamic matrix in order to calculate the control moves to each process. By applying this control approach, higher rotating screw speeds and melt plastization back-pressure can be utilized without the effects of temperature oscillations and material degradation.

Interfacial Anchoring in Semi-Crystalline Blends

K.A. Chaffin, F.S. Bates, P. Brant, May 2000

We demonstrate that anchoring of entangled interfacial chains is responsible for toughness in immiscible blends containing a semi-crystalline component. Interfacial anchors are formed when entangled chains crystallize into lamellae, creating entanglements in the phase boundary that have chain ends secured in crystallites. The proposed toughening mechanism was demonstrated with isotactic polypropylene and polyethylene. Both scattering experiments and imaging showed that non-crystalline material placed at the phase boundary decouples the interface, diluting the number of interfacial anchors. As the degree of interfacial anchoring was reduced, the failure mode changed from bulk iPP failure to interfacial failure, reducing the tensile toughness and elongation by 40%. The interfacial structure was probed directly with peel tests. When an interfacial crack was propagated through a highly anchored interface, the 90° peel strength was 15 times greater than for a crack propagated through an interface that had no significant interfacial anchoring.

Characterization of Polyethylene Blends by Using Novel Techniques Such as the Successive Self-Nucleation and Annealing (SSA) and the Fourier Self-Deconvolution IR Spectroscopy (FSD-IR)

Juan D. Sierra, Silvio Ospina, Norberto Montoya, María del Pilar Noriega, Tim A. Osswald, May 2000

At the present, the plastic film industry has been using complex blends of Polyethylene to meet the demands of better mechanical properties, excellent sealability and adequate runnability in the processing machinery. Thus the characterization and the evaluation of processing properties are of great importance for the plastic industry. According to the present study successive self-nucleation and annealing SSA and the Fourier Self Deconvolution IR Spectroscopy, is a valuable tool for characterization of complex blends of Polyethylenes. By using the above mentioned techniques it is possible quantify metallocene Polymers and traditional LLDPEs from LDPE binary and ternary blends.

Application of the Crack Layer Model for Understanding of the Correlation between Lifetime and Creep Behavior in Polyethylene

J. Fan, D. Chen, Y. Shulkin, A. Chudnovsky, N. Jivraj, K. Sehanobish, May 2000

A closely coupled system comprising of a crack and a process zone (PZ), i.e., a domain of crazed material ahead of the crack, commonly observed in polyethylenes (PEs), constitutes the crack layer (CL). According to the CL theory, slow crack growth in polyethylenes is largely a result of degradation of the process zone material. The CL theory has been applied to model some features of slow crack growth in PE, such as the discontinuous manner of the process, the widely reported specifics of fracture surface morphology, the stress and temperature dependence of lifetime, as well as the crack speed-stress intensity factor (SIF) relation. In the present work, a simplified version of the CL theory is employed to explain and generalize the correlation between the lifetime of PE pipes in brittle mode fracture and the so-called Creep Rate Deceleration Factor (CRDF) of drawn PE.

Ductile Failure and Delayed Necking in Polyethylene

W. Zhou, D. Chen, Y. Shulkin, A. Chudnovsky, N. Jivraj, K. Sehanobish, S. Wu, May 2000

Analysis of polyethylene (PE) pipes ductile failure (ballooning) suggests that it is directly related to the delayed necking phenomena and time to ductile failure of PE pipe can be evaluated as the time to delayed necking. The necking in polyethylene (PE) is studied under displacement control (ramp test) and load control (creep) conditions. In ramp tests the dependence of the yielding and drawing stresses on strain rate are established using specimens of a European PE 100 pipe grade HDPE, It is shown that both stresses decrease with decrease of strain rate and approach a common value, the characteristic stress. In creep tests of the above material, the relation of time-to-necking vs. applied stress is obtained. It is proposed to employ the testing procedure on tensile specimens for estimation of time-to-ductile failure in PE pipes. The characteristic stress is suggested to be an indicator of the ductile-to-brittle transition in failure mechanism.