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
A High Performance Phosphite Stabilizer
Organophosphites are an important class of stabilizers for polymers. They retard polymer degradation during melt processing by reaction with the reactive peroxidic intermediates that arise from oxidation of the polymer at high temperature. Moreover, phosphites can be used synergistically with hindered phenol stabilizers to provide a superior stabilization package that will allow the processor to expand the range of processing conditions without losing desired physical properties due to polymer degradation. As can be seen in table 1, phosphites have a wide variety of physical properties. One important property is resistance towards hydrolysis in the bulk state, because if a phosphite is sensitive to hydrolysis, difficulties in storage and handling can occur, especially in warm, humid climates. Recently we developed a phosphite (phosphite 7) that showed excellent hydrolysis resistance, but a question that quickly arose was, Does a phosphite with good resistance to hydrolysis have good activity as a polymer process stabilizer?" In order to answer this question we studied a key property of phosphites: their ability to react with peroxide intermediates in the oxidation cycle. The phosphites were oxidized in two hydrocarbon solvents which could serve as models for HDPE and PP: a C14-17 paraffin and poly-1-decene oligomer respectively. Then we compared the reactivity of the phosphite during oxidation with hydrolysis resistance to see if there is any direct correlation between the two properties. In addition we examined the activity of phosphites in multiple pass extrusions in order to compare the oxidations rates in a model system with processing activity during extrusion."
A High Performance Phosphite Stabilizer
Organophosphites are an important class of stabilizers for polymers. They retard polymer degradation during melt processing by reaction with the reactive peroxidic intermediates that arise from oxidation of the polymer at high temperature. Moreover, phosphites can be used synergistically with hindered phenol stabilizers to provide a superior stabilization package that will allow the processor to expand the range of processing conditions without losing desired physical properties due to polymer degradation. As can be seen in table 1, phosphites have a wide variety of physical properties. One important property is resistance towards hydrolysis in the bulk state, because if a phosphite is sensitive to hydrolysis, difficulties in storage and handling can occur, especially in warm, humid climates. Recently we developed a phosphite (phosphite 7) that showed excellent hydrolysis resistance, but a question that quickly arose was, Does a phosphite with good resistance to hydrolysis have good activity as a polymer process stabilizer?" In order to answer this question we studied a key property of phosphites: their ability to react with peroxide intermediates in the oxidation cycle. The phosphites were oxidized in two hydrocarbon solvents which could serve as models for HDPE and PP: a C14-17 paraffin and poly-1-decene oligomer respectively. Then we compared the reactivity of the phosphite during oxidation with hydrolysis resistance to see if there is any direct correlation between the two properties. In addition we examined the activity of phosphites in multiple pass extrusions in order to compare the oxidations rates in a model system with processing activity during extrusion."
Blends of Flexible Polypropylene and High Density Polyethylene
This study focused on the melt blending of flexible polypropylene (FPP), a polyolefin with controlled levels of propylene comonomer, with high-density polyethylene (HDPE). Specifically, FPP of melt flow 2.8 g/10 min and melt temperature of 146 °C was combined with a HDPE of melt flow 4.0 g/10 min via single screw extrusion. Blends were prepared at 20, 50 and 80 % FPP in the HDPE material, and properties were evaluated as compared to the pure resins. The blends were subjected to injection molding and mechanical properties were determined, including modulus, tensile strength, and impact resistance values, along with an examination of the ability of the FPP to modify the softness and flexibility of the HDPE material.
Polymer-Layered Silicate Nanocomposites: Emerging Scientific and Commercial Opportunities
Polymer nanocomposites represent a radical alternative to conventionally (macroscopically) filled polymers. Because of their nanometer-size dispersion the nanocomposites exhibit markedly improved properties when compared to the pure polymers or conventional composites. These include increased modulus and strength, outstanding barrier properties, increased solvent and heat resistance and decreased flammability. In my presentation I will review the physical and mechanical properties of nanocomposites and discuss them in terms of their static (neutron scattering and computer simulations) and dynamic (including NMR and dielectric relaxation) properties.
Physical Properties of Clay-Polymer Nanocomposite Coatings
Clay-polymer nanocomposites have recently received significant attention from the industrial community because of their wide range of novel physical properties. The dispersion of clay particles in a polymer matrix can result in the formation of three general types of composite structure: (1) Conventional composites that contain clay layers unintercalated in a face-to-face aggregation with macroscopic segregation of the clay and the polymeric phases. (2) Intercalated clay composites that are formed by the insertion of one or more molecular layers of polymer into the clay host galleries. (3) Exfoliated clay composites where singular clay platelets are dispersed in a continuous polymer matrix. It is the presence of clay as described in (2) and (3) that is of interest in coatings for practical applications. Intercalation and exfoliation of clay can be conveniently monitored by measuring the (001) basal plane spacing of the clay platelets using X-ray diffraction (XRD). In this work, XRD revealed significant information about the morphology of the clay-polymer nanocomposites which, in turn, determined the physical performance of the coatings. Commercially available synthetic smectite clay, identified as a transparent, environmentally benign nanoparticulate material, has been studied in various polymeric matrices. Depending on the polymeric species, the basal plane spacing of the clay platelets ranged from 13.5 to 40 Angstroms. Details about the XRD results and the corresponding changes in the physical performance of the clay-polymer nanocomposite coatings will be presented.
A New Family of Intercalated Clays for Clay/Polymer Nanocomposites
Over the past decade a new family of materials called nanocomposites have emerged as potentially important commercial composites for engineering and packaging applications. These materials have normally contained a smectite clay as the nanosize component of the composite. These materials are naturally occurring minerals that exhibit large aspect ratios and one dimension in the nanometer range. These minerals however, are normally very hydrophilic and, therefore must be surface modified in order to render them compatible with most polymers or monomers. This paper reports a series of new surface modified clays for use in nanocomposites and some application to nanocomposites. In recent years a family of surface modified clays has been developed that do not involve the use of onium ions. This paper will describe these new methods of surface modifications and examples of how they can be applied to polymer nanocomposites.
Property Retention Index of Thermoplastic Composites
The use of thermoplastic polymers, reinforced with a variety of man made products, including fibrous glass, Kevlar*, polyester, and nylon fabrics, has been growing aggressively in recent years. Combining dissimilar polymer matrices as the impregnating skins allows for unusual combinations of functional properties. One major problem, unlike their sister thermosetting composites, is the lack of crosslinking, which ensures functional integrity, especially at elevated temperatures. This is offset, however, by enhanced impact toughness which most thermosetting composites cannot offer. The scope of this study was to investigate the property retention index (PRI) of a range of thermoplastic mat composites (TMC) and to evaluate the PRI for selected physical properties, including torsional modulus and flexural behavior. The role of the impregnating resin, the reinforcement type/physical form, and fabrication/assembly scheme shall be reported.
Comparison of Blow Molding Software Results to Actual Wall Thicknesses
This paper will compare and contrast output from blow molding software to actual molded parts. The software being studied is a 3D shell element blow molding simulation package. With the rapid growth of blow molding today there is a need for simulation software, which will help processors, mold builders, and part designers. This software may help to reduce the time to market by eliminating design guesswork based on past experience. This study will examine one oval bottle and compare actual wall thicknesses to the software. A mold and a laser mic will be used to determine actual volumes, diameters and thicknesses along the parison.
Correlation of Experimental Data Using Simple and Complex Bottle Shapes with Blow Molding Simulation Software
The purpose of this paper is to reduce design iterations in blow molding design by producing better products and reducing the time to market. The software being used can provide a good starting point for the design and initial process. This paper will provide published data on thickness predictions from the software and the actual values obtained from molded parts. Both simple and complex geometry will be tested. The geometry used at the start is a cylindrical bottle, followed by an oval bottle. The oval bottle will provide a good opportunity to see the thickness variations at the further extremes. The software predicts the thickness by using 3D shell elements.
Development of an Apparatus to Measure Hoop Strength of Various Materials
Throughout the packaging industry decisions are often made concerning types of bottles to use for certain container applications. When deciding which type of bottle is suitable for a product one aspect is the hoop strength of the bottle. This hoop strength is measured by air pressure testing the bottles. Using the guidelines set forth in ASTM D 2561, an apparatus that consists of a pressure regulator and explosion chamber, an average hoop strengths were determined for each HDPE bottle. The results of the hoop strength testing will show the mechanical differences between the bottle types and material types. It will be shown that the apparatus can also be used to determine the increase in diameter of each bottle with pressure. It can also be used to determine long term creep properties. The specimen sizes provided variables to explore the hoop strengths of HDPE. Conclusions were made on the different hoop strengths of the different specimens.
Computer Simulation of Polymers with Intermediate Order: The Discovery of a Novel Helix-Kink" Architecture"
X-ray diffraction patterns for polymers with splits in the classic Amorphous Halo" pattern are difficult to predict using molecular modeling. These polymers contain a level of order intermediate between that of a crystal and a truly amorphous polymer that is not simply a combination of the two (semicrystalline). We have accurately predicted the Wide Angle X-ray Diffraction (WAXD) pattern for 23 erythro di-isotactic poly(norbornene) (PNB)a polymer with promising application as an interlayer dielectric or a photoresist material in the microelectronics industry. Molecular modeling predicts this polymer exists in the glassy state in a helical conformation that is occasionally disrupted by kinks. Comparison to other modeling results on poly(t-butyl acetylene) (PTBA)suggests that both these polymers belong to a new class of polymers that contain this helix-kink conformation. This conformation is what is responsible for the viscosity behavior of PNB and it may be useful in understanding both viscosity and membrane barrier properties for this class of polymers."
Computer Simulation of Polymers with Intermediate Order: The Discovery of a Novel Helix-Kink" Architecture"
X-ray diffraction patterns for polymers with splits in the classic Amorphous Halo" pattern are difficult to predict using molecular modeling. These polymers contain a level of order intermediate between that of a crystal and a truly amorphous polymer that is not simply a combination of the two (semicrystalline). We have accurately predicted the Wide Angle X-ray Diffraction (WAXD) pattern for 23 erythro di-isotactic poly(norbornene) (PNB) a polymer with promising application as an interlayer dielectric or a photoresist material in the microelectronics industry. Molecular modeling predicts this polymer exists in the glassy state in a helical conformation that is occasionally disrupted by kinks. Comparison to other modeling results on poly(t-butyl acetylene) (PTBA)suggests that both these polymers belong to a new class of polymers that contain this helix-kink conformation. This conformation is what is responsible for the viscosity behavior of PNB and it may be useful in understanding both viscosity and membrane barrier properties for this class of polymers."
Molecular Modeling of Elastic and Photoelastic Relationships for Crosslinked Polymer Networks: A Statistical Segment Approach
The polymer chain is considered to comprise of freely orienting statistical segments having a distribution of vector lengths and polarizabilities, which are utilized to develop stress-elongation and birefringence-elongation relationships for crosslinked polymer networks. This formulation provides an accurate fit of poly(cis-isoprene) and polyethylene stress-elongation data over a wide elongation range, using two physical parameters. These fitted parameters yield objective predictions of birefringence-elongation relationships. This approach incorporates primary molecular structural features in modeling mechanical and optical properties of rubbery polymer networks.
A Study of Polymer/Clay Nanocomposites for Biodegradable Applications
A series of biodegradable polymer/clay nanocomposites have been prepared using two techniques: in-situ polymerization and twin screw extrusion. These samples containing 5-25% clay and polycaprolatone (PCL) were characterized with regard to processability, biodegradability, morphology, thermal behavior and mechanical properties. The processing at different screw speeds (20, 40, 60 rpm) did not alter the polymer/clay interactions. Biodegradation results in soil showed 50% mineralization of PCL/clay in 50 days as compared to 10% for the pure PCL film. X-ray diffraction patterns demonstrated that the polymer had different degrees of intercalation in the silicate layers of the clay. Dynamic mechanical analysis showed no change in the PCL glass transition temperature with the addition of clay.
Stress Relaxation of Semi-Crystalline Polyester Films: Aging Rate Effects
Using stress relaxation measurements, we describe the kinetics of the physical aging process for two semi-crystalline, biaxially stretched polyester films, PET and PEN, within their respective ? transition regimes. By applying the principles of time-aging time and time-aging temperature equivalence, we establish the temperature dependence of the corresponding aging acceleration factors over a temperature range spanning from ca. Tg -40°C to Tg. The results for both materials show significant increase in the rate of physical aging at ca. 20°C below the glass transition temperature. However, the increase in aging rate is approximately tenfold higher for PET, implying that the segmental mobility of this polymer is significantly higher at the corresponding temperature.
Optimization of Thermoforming
There are many ways of optimizing the thermoforming process. However, any tuning of the processing parameters still remains a matter of experience. Using computer simulation software provides a way to explore various optimization possibilities without wasting machine production time, material and money through costly experiments. We have examined several methods of optimization using different materials, temperature, sheet thickness profiles and process parameters. For this purpose we have used the T-SIM® simulation program. This software uses a K-BKZ model capable to describe viscoelasticity and large deformation. The results of the simulations enable to determine which process parameters have the major influence and what are the pros and cons of each optimization method.
The Effect of Different Grades of Various Fillers on the Color Matching Process
What is color? “The committee on colorimetry of the Optical Society of America has defined color as consisting of the characteristics of light other than spatial and temperal inhomogenities, light being that aspect of radiant energy of which a human observer is aware through the visual sensations which arise from the stimulation of the retina”(Ahmed, p.1) Simply stated color is what we “see the result of the physical modification of light by colorants as observed by the human eye and interpreted in the brain. Knowing what color is alone is not enough we must also understand how we perceive it. The Perception of color depends on many factors such as the inherent color characteristics of an object the surroundings of an object and even by such individual factors like past experience and individual visual response characteristics. (Ahmed p.2) In order to study color one must first learn to describe observed differences in color between two objects. This can be accomplished through the use of the following three variables: hue (dominant color) value (lightness vs. darkness) and chroma (saturation or purity of color). These variables are known as the color coordinates and form the basis of the language system used in color description and specification. (Ahmed p.5)"
The Effect of Different Grades of Various Fillers on the Color Matching Process
What is color? “The committee on colorimetry of the Optical Society of America has defined color as consisting of the characteristics of light other than spatial and temperal inhomogenities, light being that aspect of radiant energy of which a human observer is aware through the visual sensations which arise from the stimulation of the retina”(Ahmed, p.1) Simply stated color is what we “see the result o fthe physical modification of light by colorants as observed by the human eye and interpreted in the brain. Knowing what color is alone is not enoughwe must also understand how we perceive it. The Perception of color depends on many factors such as the inherent color characteristics of an object the surroundings of an object and even by such individual factors like past experience and individual visual response characteristics. (Ahmed p.2) In order to study color one must first learn to describe observed differences in color between two objects. This can be accomplished through the use of the following three variables: hue (dominant color) value (lightness vs. darkness) and chroma (saturation or purity of color). These variables are known as the color coordinates and form the basis of the language system used in color description and specification. (Ahmed p.5)"
On-Line, In-Line and Off-Line Rheometry of Polyethylene
In-process rheometry (on-line & in-line) carried out during twin screw extrusion of several polyethylenes (LDPE, LLDPE and three HDPEs) is compared with conventional off-line rheometry for both shear and extensional properties. Use of two on-line and two off-line rheometers allowed comparison of data from a range of commercial instruments in order to validate their performances. In-process shear flow rheometry was undertaken using a six-sensor in-line extrusion die rheometer on a twin screw extruder. Results from the five rheometers were compared and good agreement observed between the different routes to measurement, for these relatively stable materials.
Observation of 3-D Effects in Flow Visualisation of Polymer Melts
Flow visualisation has been undertaken using a specially designed flow cell mounted on a single screw extruder, which permits laser sheet lighting of selected planes in the flow. It has therefore been possible to quantify velocity fields and entry profiles in a 180 degree entry to a slit at locations across the flow, building up, for the first time, a quantified map of velocity components in the axial (x) and transverse (y) flow directions (including at the flow cell wall). Together with stress birefringence measurements, this allows accurate assessment of extensional viscosity, which has been compared with Rheometrics Meissner results for an LDPE. In addition, a modified cell has allowed visualisation of the slit entry region in the third orthogonal direction (z), leading to first ever observations of precession of an LDPE melt in its vortex region, providing new insights into the full 3-d flow field.
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