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

Interactions of Pesticides and Stabilizers in PE Films for Agricultural Use

Edina Epacher, Béla Pukánszky, May 1999

Polyethylene films used in agriculture are subjected to the effect of oxygen, UV radiation, rain etc. Beside these usual effects encountered in outdoor applications, also the pesticides used for the protection of the crop may influence the degradation and lifetime of the films. In an attempt to determine the interaction of pesticides and some frequently used light stabilizers in PE, films containing three different stabilizer packages were exposed to the effect of 24 commercial pesticide formulations. The effect of UV radiation was modeled by Xenotest aging. The measurement of oxidative stability after exposure indicated that pesticides interact with the stabilizers, indeed. UV and FTIR spectroscopy gave further information about these interactions. Mechanical properties of the films deteriorated considerably after exposure at some pesticide/stabilizer package combinations. According to their effect pesticides could be classified into three groups: inert compounds, formulations with moderate effect and harmful substances. Mainly formulations having sulphur as an active component belonged to this third group due to the activity of sulphur in radical reactions.

Crystallization and Morphology of Propylene/Pentene Random Copolymers

P. Juhász, K. Belina, May 1999

Crystallization and melting behavior of propulene/1-pentene random copolymers were studied. WAXD and d.s.c. measurements of isothermal crystallized samples confirm that the copolymers contain the ? crystal form in large quantity. The content of ? form increases with increasing pentene content and crystallization temperature. We found a limitation in the relative ? content around 60-65%. The efficiency of pentene comonomer is much higher than of ethylene. The equilibrium melting point decreases with pentene content in a non-linear fashion and the values are much lower than the theoretical ones.

Rapid Heating and Curing of Structural Adhesives by Infrared and Radio Frequency

Kin Ming Kwan, Chung Yuan Wu, Avraham Benatar, May 1999

Structural adhesive requires a considerate curing time to achieve handling strength at room temperature. Conventional heating and curing methods are unable to cure adhesives in minutes because of the slow heat input rate to the system. Infrared heating can penetrate into the adhesive to accelerate the reaction process in a very short time. Radio frequency heating produced substantial energy input to the adhesive through the dielectric loss of the polar molecules under rapid changing electric field. The effect of operating parameters on green strength produced from these methods were studied and compared to that cured at room temperature. Both methods show significant reduction in cure time to obtain a strong bond in less than three minutes.

Optimization of Contact Hot Plate Welding of HDPE

Bovornchok Poopat, Chung-Yuan Wu, Avraham Benatar, Joon B. Park, May 1999

The hot plate welding process is widely used for welding of thermoplastics. To optimize the welding processes, melt layer thickness, welding displacement and squeeze-out ratio are used as control parameters. Contact hot plate welding of high density polyethylene (HDPE) was investigated. The melt layer thickness of the high density polyethylene samples during heating was measured. The mathematical relationship between melt layer thickness and hot plate temperature and heating time was developed and used as control parameters. The effects of welding parameters (melt layer thickness, weld displacement and squeeze-out ratio) on joint quality are presented. The results show that the maximum attainable joint strength is 100% of the bulk material strength. A minimum melt layer thickness of 2.5 mm (total from both sides) is required to produce good quality joints. A minimum weld displacement of 0.7 mm (both sides) or a squeeze-out ratio of 0.3 is also required to produce good quality joints.

Hot Plate Welding of Polypropylene and Talc Reinforced Polypropylene Composites

Chung-Yuan Wu, Bovornchok Poopat, Avraham Benatar, Joon B. Park, May 1999

A systematic study of polypropylene and talc reinforced polypropylene using hot plate welding was conducted. The control parameters, welding displacement, melt layer thickness, and ratio of weld displacement to melt layer thickness were studied. A constant pressuring method was evaluated. Approximate equations were obtained experimentally to calculate the melt layer thickness based on the hot plate temperature and heating time. It is found that the maximum joint strength depends on the talc concentration. The maximum joint strength for 0% and 40% talc reinforced polypropylene was 97% and 54% of the bulk strength, respectively.

Rheology of Hard-Metal Carbide Compounds

Berenika Hausnerová, Petr Sáha, May 1999

The results of an investigation of steady-state and oscillatory flow properties of hard-metal carbide powder compounds are presented. These highly concentrated compounds are intended for powder injection moulding (PIM) technology. The volume concentrations of powders, containing mainly tungsten carbide and cobalt alloy, differing in particle size distributions, varied up to 57.5 vol. %. The model relations, correlating relative viscosities with volume fraction of filler and shear rate (shear stress), were used in order to attain maximum volume fraction of powder in the compound. At the concentrations near the maximum loading an unstable flow was observed, which has been found to be influenced by the particle size distribution of the powder used as well as its concentration. In some cases, the instabilities were suppressed by repeated extrusion.

Positive and Negative Electrorheological Effect of Poly(Methyl Methacrylate) Dispersions Stabilized by the Block Copolymer Steric Stabilizer

Vladimír Pavlínek, Petr Sáha, Otakar Quadrat, Jaroslav Stejskal, May 1999

A change of viscosity of the poly(methyl methacrylate) dispersions in decane stabilized with polystyrene-block-poly(ethylene-co-propylene) copolymer after application of an external electric field depends on the character of its original structure. When the mutual particle interactions are low, the organized structure formed in the electric field causes an increase in the viscosity of the dispersion and a positive electrorheological effect appears. If, due to strong interactions, a gel-like network particle structure exists, an application of the electric field causes a breakdown of this structure, the viscosity of the system decreases and negative electrorheological effect occurs. The type of rheological response is thus influenced by composition of dispersions.

Morphology and Compression after Impact Strength Relationship in Rubber-Toughened Composites

B.J. Derkowski, J.A. Avila, S.E. Eschmann, May 1999

Morphology and compression after impact (CAI) strength relationships in rubber-toughened high performance composites are investigated using quantitative image analysis. A group of six quasi-isotropic carbon fiber-epoxy composites, with variations in CAI strength were analyzed to reveal how the particle size, particle size distribution, and location of rubber particles affect the CAI strength values and the corresponding damage mechanisms. It is found that the CAI strength of rubber-toughened composites is greatly affected by the size and size distribution of rubber particles in the interlaminar regions of the composite. In general, high CAI strength composites exhibit more uniform particle size distribution and spread evenly across the interlaminar regions. Whereas, for low CAI strength composites, the rubber particles tend to cluster together and have wide size distribution.

A New High-Performance LLDPE for Blown Film Applications

Harry Mavridis, May 1999

Conventional Ziegler-Natta catalyzed LLDPEs combine good mechanical properties with moderate processability. Efforts to enhance LLDPE properties further, through metallocene catalysts for example, generally result in a processability penalty. The present work describes a new development in LLDPE technology which produces resins with significant improvement in mechanical properties without sacrificing processability. Detailed blown film results show the performance improvement achieved by the new resins, compared to conventional LLDPEs, and the downgauging potential offered by the property improvement.

The Effect of Film Winding Tension and Melt Temperature on COF and Other Properties of PE Blown Film

Brian H. Schumann, Jeffrey J. Wooster, May 1999

A designed experiment has been conducted to determine the effects of sealant layer melt temperature and film winding tension on the coefficient of friction (COF) and other physical and optical properties of a coextruded blown film containing a polyolefin plastomer as the sealant layer. A statistical design program was used to model the quantitative response of the various film properties to the control variables evaluated. Evaluation of the data indicated that only the COF had a significant response to the control variables. As the winding tension of the rolls increased, the COF increased dramatically.

The Use of Polymer Processing Aids to Reduce Gel Formation in Polyolefin Plastomer Extrusion

Susan S. Woods, Stephen E. Amos, May 1999

Polymer additives have long been linked to gel formation and reduction in polyolefin film extrusion. Several hypothesis about these additive/gel links have been empirically explored in a controlled blown film experiment. A study comparing gel levels in a metallocene catalyzed polyolefin plastomer was done on a lab size blown film line with a groove feed extruder. A photo imaging process was used to count gel levels, per unit area, during a significant portion of each run. Additive packages were varied to determine the effect of potential gel reducing additives. The data support the hypothesis that Dynamar™ polymer processing aids can reduce the amount of gel particles in the film.

The Influence of Stress on Peel Strength of Acid Copolymers to Foil

Barry A. Morris, May 1999

As an acid copolymer is converted in the extrusion coating process, it undergoes considerable stress and orientation. This stress arises from shear forces in the extruder and die, from extensional forces as the melt curtain is drawn down and from shrinkage forces during crystallization. It is hypothesized that these stresses may influence peel strength by impacting tensile properties and residual stress at the foil-polymer interface. Relationships are developed between stress and common processing parameters such as air gap, die gap, melt temperature and line speed. An experiment is described where processing parameters were changed in a systematic way to alter the stress imposed on the polymer. Data is presented which strongly supports the hypothesis, and provides an understanding as to the role and impact of various processing parameters.

Munsell Color Science Laboratory Industrial Color Difference Consortium - Current Initiatives and Future Directions

Roy S. Berns, May 1999

There is a continual need for automated approaches to defining color quality within the industrial community. It is well known that color vision is a most complex process with many variables affecting visual color tolerances. Although much progress has been made, as all professionals in this field are likely to agree, much remains to be done. One of the very few such efforts internationally is the RIT Munsell Color Science Laboratory's Industrial Color Difference Consortium, started in 1995. The Society of Plastics Engineers is one of ten members. This paper will summarize recent research and future initiatives.

Automation in Thermal-Analytical Instrumentation and SPC Helps in Supplier Quality

Vijay N. Reddy, May 1999

Defect prevention and reduction of variation are described as minimum expectations in the fundamental quality systems. There are strong relationships between reduction in variation, zero defects and ultimately the cost. Heavy reliance is placed on in-process inspection, testing and on-line monitoring of process parameters. Statistical process controls (SPC) and control charts are used to determine the process capability index (Cpk). Thermogravimetric analysis (TGA) is widely used to measure product quality. We will discuss the use of Robotics-TGA and SPC that has come to the aid of process engineers to improve Cpk in production of polymer based devices for automotive applications.

Snap Tie Cones Made from Recycled PET and HDPE

Bryan Failing, May 1999

To address the growing environmental concern, Santa Clara University's Plastics Recycling Laboratory chose a relatively inexpensive product with low structural demands to open a new market for 100% recycled material products. Snap tie cones, used in construction to space wall forms prior to pouring the concrete, were injection molded from recycled PET and HDPE and tested against the cones used in industry made from HIPS. Four tests- dimensional checks, compression, impact, and creep- were designed and conducted. The commercial cones along with ones made of recycled PET and HDPE were tested before and after ultraviolet (UV) exposure. The data analysis shows that the recycled PET cones outperform their industry counterpart, while recycled HDPE did not perform as well. This leads to the conclusion that recycled PET is a viable alternative to HIPS in this application.

Testing of Recycled PET Rebar Chair

Todd Jenkins, May 1999

Small chairs for supporting reinforcing steel in concrete slabs were molded from recycled PET. The performance of these chairs was tested relative to plastic chairs available on the market. Four tests were used to evaluate the chairs. The tests were designed to evaluate impact, compression, and UV degradation strengths of the chairs, as well as the adhesion between the PET and concrete. The recycled PET chairs performed better than commercial chairs under compression, but did not allow for flow of the concrete. The impact performance of recycled chairs was very comparable to the commercial chairs. UV results are embedded in the impact and compression tests.

Effects of Drying Parameters on Recycled PET

Scott Kennedy, May 1999

With the rising usage of plastic PET bottles and the rising need to recycle them, there is an increasing demand to refine the recycling process. It is very important to have the recycling process be cost and time efficient. The focus of this study is on the drying aspect of the recycling of PET. In this experiment, different parameters of the drying process were varied, specifically the time and the temperature. The strength was not significantly affected by time or temperature of drying. The melt index data showed that drying the PET at 177°C gave the best results. The overall best results seemed to be at 177°C, and a time around six hours. Longer or shorter drying times appear to degrade the material.

A High Performance Phosphite Stabilizer

Daryl Stein, Don Stevenson, May 1999

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

Daryl Stein, Don Stevenson, May 1999

Blends of Flexible Polypropylene and High Density Polyethylene

Nupur Patel, May 1999

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.