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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Workflow for Enhanced Fiber Orientation Prediction of Short Fiber-reinforced Thermoplastics
Susanne Kugler, May 2020

In this paper a workflow is proposed for an enhanced fiber orientation prediction in injection molding of short fiber-reinforced thermoplastics. The workflow is easy-to-use, as the final fiber orientation prediction is integrated into the commercial software Moldflow®. For a given material with polymer matrix P and a volume fraction x of fibers, four steps have to be performed: 1) Generating a representative volume element (in the following, referred to as cell) with volume fraction x and mean fiber length, 2) Shearing of the cell using a mechanistic fiber simulation, 3) Calculating the transient fiber orientation tensor and fitting macroscopic parameters and 4) Performing the fiber orientation analysis with the optimized macroscopic parameters in Moldflow®. Based on experimental data, the pARD-RSC model was selected as macroscopic simulation model. It was implemented in Moldflow® via the Solver API feature. The enhanced workflow is validated at the example of two industrial applications with different polymer matrices and different fiber volume fractions. With the proposed workflow, we observe equal or higher accuracy of fiber orientation estimation in comparison to Moldflow® fiber orientation models RSC and MRD.

Review of PE Pipe Lifetime Prediction Based on Pent Test
I. Sedat Gunes, Feina Cao, Sadhan C. Jana, May 2010

A new method of evaluating polyethylene (PE) pipe brittle failure time has been recently proposed. The method consists of an extrapolation of the failure time in standard PENT test to brittle failure time of PE pipes of arbitrary diameter and wall thickness at various loads and temperatures. The method is based on several assumptions that have not been adequately addressed in [1]. This paper presents a detailed review of the theoretical and experimental basis of the extrapolation proposed in [1] and reveals its limitations. A fracture mechanics analysis of the PENT test is presented. It requires evaluation of parameters in power law" equation of the slow crack growth (SCG). Thus a specimen whose stress intensity factor (SIF) is independent of crack length has been used to serve this purpose. Such specimen allows an accurate determination of crack growth rate vs. SIF relationship and thus predicts the duration of SCG stage of brittle fracture process at various temperatures. The study indicates that the formula proposed in [1] can be used for materials ranking with respect to SCG resistance within a limited temperature range but is inadequate for estimation of lifetime in brittle fracture."

Water Vapor Transport Properties of Shape Memory Polyurethane Nanocomposites
I. Sedat Gunes , Feina Cao , Sadhan C. Jana, May 2010

In this paper water vapor permeability (WVP) of thermoplastic polyurethane nanocomposites with crystalline soft segments was evaluated. Organoclay nano-size silicon carbide (SiC) and a high structure carbon black (CB) were mixed with shape memory polyurethane (SMPU) based on semi-crystalline soft segments. All nanocomposites were prepared by bulk polymerization using a Brabender internal mixer. Compression molded specimens were used in the determination of WVP. The results indicated that the presence of silicon carbide augmented WVP by reducing the soft segment crystallinity whereas that of organoclay reduced the WVP considerably due to excellent exfoliation.

Polymer Clay Nanocomposites of Linear Low Density Polyethylene (LLDPE) and Polyoxymethylene (POM)
M. Shahlari, P. L. Roberts and S. Lee, May 2008

Polymer-clay nanocomposites involving a blend of two otherwise incompatible thermoplastic polymers were prepared and investigated for the effects of adding organically modified clay. Linear low density polyethylene (LLDPE) and polyoxymethylene (POM) at several composition ratios (70/30, 50/50, 30/70) were melt mixed with 5% Cloisite 15A and 5% Cloisite 30B, respectively. Their blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The LLDPE/POM (70/30) blend nanocomposites incorporating Cloisite 15A showed co-continuous morphology according to the SEM images, while those with Cloisite 30B showed some limited levels of compatibility. Further, Cloisite 15A improved the melting temperature of LLDPE and POM while Cloisite 30B had no significant effect on the LLDPE melting temperature but increased the melting temperature of POM. As for the LLDPE/POM (30/70) blends, Cloisite 15A made the two originally incompatible phases indistinguishable, while the blends containing Cloisite 30B showed a significant decrease in the domain sizes. However, the blend samples without organoclay incorporation did not exhibit any compatibility and the dispersed phase was totally segregated. TGA results showed that addition of clay decreased POM degradation temperature but there was no significant changes detected in PE’s. The clay’s compatibility with one or both polymers is shown to make a significant difference in the blend morphology and compatibilization mechanisms of the polymer-clay nanocomposites, which are phenomenologically explained in this paper.

Evaluation of Shape Memory Properties of Polyurethane Nanocomposites with High Hard Segment Content
F. Cao | S. C. Jana, May 2008

Shape memory polyurethane (SMPU) with high hard segment content offers good shape recovery ratio and high recovery stress. This study considered further improvement of shape recovery stress with the introduction of nanoclay. Reactive nanoclay particles were tethered onto polyurethane chains via urethane groups and provided extra crosslink points. This led to increase of modulus and recovery stress, e.g., a recovery stress of 19 MPa with 5 wt% clay compared to 13.5 MPa for unfilled PU. The recovery ratio of SMPU was not influenced by the addition of clay. The influence of stretching rate, stretching ratio, and stretching temperature on shape recovery force was studied.

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