SPE Library

This report describes a simple solvent-based technique for the separation of tris(nonylphenyl) phosphite (TNPP) from a LLDPE (linear-low density polyethylene) resin, as well as subse-quent analysis. The solvent extracts" were ana-lyzed as is using 31P-NMR and/or liquid chroma-tography techniques. The analytical results showed that the main reaction product formed during the compounding step was tris(nonylphenyl) phosphate (PV) by way of phosphite (PIII) oxidation. It was further shown that the phosphite did not undergo any hydrolysis reaction as determined by analyzing for nonyl-phenol and "acid phosphite" levels. Lastly the HPLC method was shown to be viable in the concurrent analysis for both components in typically used phenolic and phosphite antioxidant blends."

Simultaneous volume and enthalpy relaxation behaviour of a-PMMA stimulated a by double-step temperature jump is studied. For both types of relaxation a memory effect following the up-jump can be observed, which is weakened by increasing of preannealing time. A constant relationship between both quantities during the sample expansion has been found. From the dependence of excess enthalpy vs. specific volume, an apparent bulk modulus, Ka, was calculated (Kubat, 1998). Its values increase with pre-annealing time and approach to a maximum value. The modulus can be used for quantification of the thermodynamic equilibrium.

Digital electronic imaging using Charge Coupled Devices (CCD) has become popular due to its mass adoption in digital imaging applications. These sensors are moderate in resolution, extremely sensitive, offer wide dynamic range, and compared with photo-multipliers are capable of withstanding exposure to bright light without damage. These characteristics made CCD detectors ideal for chemiluminescence (CL) studies for polymer oxidative degradation.We have adapted a CCD imager with a differential scanning calorimeter (DSC) for simultaneous oxidative induction time (OIT) and CL studies. In addition, these CCD imagers are inherently area detectors, making them easily adapted for multiple sample studies or situations where sample heterogeneity exists. Advantages and considerations of CCD CL technique will be presented.

Recent developments in plastic materials and processing have opened up product design opportunities that have been heretofore impossible. Designers have utilized plastic materials in a variety of new applications in automotive, consumer, packaging, personal care, electronics, sports and leisure, construction and appliance products.Plastic materials like thermoplastic elastomers, conductive and reinforced products, alloys and blends, etc. have enabled breakthrough designs and new functional products. Process developments like co-extrusion, multi-shot molding, foams and in-mold decorating have accelerated the penetration of plastics into new applications. Design and collaboration tools like CAD (computer-aided design) and rapid prototyping and tooling have contributed to reduction in the product development cycle and time to market.This presentation will review some case studies, which are illustrative and identify the challenges and the opportunities facing thermoplastics today and into the future.

By means of new probe design and rapid data acquisition of 1,900 Hz repetition rate, we have succeeded in in-line ultrasonic monitoring of residence time distribution (RTD) at the melting, mixing, and pumping zones as well as at the die exit of a W&P 30-mm twin-screw extruder by mounting the ultrasonic probes on the extruder barrel over the screw elements. The experimental systems were LDPE, CaCO3 -filled LDPE and a Kraton/LDPE blend. For the first time the ultrasonic data of each of the extruder functional zones will be presented. The performance of the ultrasonic approach was evaluated against a conventional optical RTD measurement method by using an optical sensor side by side with one ultrasonic probe at the mixing zone of the extruder. Good agreements were obtained. An advantage of the presented ultrasonic technique is that in addition to RTD, it may provide simultaneously other process related information including material composition, filler dispersion, viscosity, etc.

Nondestructive three-dimensional refractive index measurements are used for the determination of both crystallinity and orientation in thin polymer films. The prism wave-guide coupler is particularly suited for three-dimensional isotropic and anisotropic thin film studies because of the quantitative character of the information obtained and the ease of data acquisition. It has been limited, however, to measuring the refractive index of transparent or weakly absorbing films. The present study show s that by using a modified prism wave-guide coupler it is possible to determine the complex refractive index over a range from transparent to highly absorbing films from the internally reflected light intensity. Thus both the refractive index, n, and the extinction coefficient coefficient, k, and hence the real, ?1, and imaginary, ?2, parts of the dielectric function, can be obtained. This method is used to determine the anisotropic three-dimensional ?1 and ?2 values of spin coated EB and HCl doped ES polyaniline films at two very different wavelengths.

Organic polymers are a commercially important class of materials that are being increasingly used in outdoor applications such as paints, coatings, sealants, siding and roofing membranes, to name just a few. One of the most damaging elements in the outdoor environment is ultraviolet (UV) radiation, both alone and in conjunction with moisture and temperature. Conventional ways of predicting the weatherability" or service life of a polymer involve either outdoor testing performed in real time or accelerated laboratory testing using artificial UV sources neither of which have proven to be entirely successful.The High Performance Polymeric Building Materials Group at NIST is developing a reliability-based methodology for predicting the service life of a polymeric material in outdoor environments. The NIST approach makes use of methodologies that are well-established in the biological and medical communities. In the course of advancing this new methodology a number of novel instruments for conducting UV exposures have been developed. The basis for the new predictive methodology and the novel instruments used for laboratory UV weathering will be discussed."

The bonding in polypropylene (PP)/glass composites is inherently weak due to the non-reactive polypropylene matrix. Traditional sizings are only useful in increasing the interfacial strength when compatibilizers are added to the matrix. Currently, maleated polypropylene (mPP) is widely used to improve the bonding in PP/glass composites; therefore, the overall properties of the composite are improved.A better understanding of the contributions of the mPP's is desired. This research investigates the interphase in PP/glass composites using in-situ Near-IR fiber optic techniques and glass bead composite mechanical properties.The in-situ infrared technique utilizes a lead doped high refractive index silica glass fiber. The Near-IR source is guided down a single fiber. An evanescent wave is used to concentrate the area of investigation to the interphase. The glass fibers are coated with ??aminopropyltrimethoxy silane (??APS). The results compare several commercial grades of maleated polypropylene blended with a 20 MFI homo-polypropylene. Overall mechanical properties of the injection-molded composites will be analyzed in conjunction with the infrared studies.

In injection molding processes, an air gap is formed between the cavity steel and plastic part as shrinkage occurs throughout the cooling phase. Considering the significant difference between the thermal conductivity of P-20 steel (41 W/m·?C) and air (0.0383 W/m·?C), the air gap is a potential medium for creating an asymmetric conductive heat transfer within the plastic part. This assumption of different heat transfer behavior was studied by using finite element analysis and flow simulation packages. The results were contrasted to those of the symmetric behavior. The conclusions made discuss the practical needs of considering the air gap formation in cooling designs and its probable impact on qualities of plastic parts.

The use of spectroscopic techniques in the analysis of polymer production processes is becoming more prevalent. At-process methods allow for real-time information on a variety of melt characteristics to be collected. Several analytical techniques are being explored for in-line and on-line use during extrusion processing of polymer melts, with a view to characterising polymers for process monitoring and control.In-line ultrasonic velocity measurements have been made simultaneously with on-line mid- and near- infrared and in-line Raman Spectroscopy during single screw extrusion of a range of blends of an HDPE and a PP. The sensitivity of these techniques to changes in blend composition is being assessed and compared. The techniques show very close agreement in monitoring the dynamics of change from one blend composition to another.

This paper reports on a method of integrating extrusion die design with state-of-the-art computer-aided design programs. The design of a coat hanger extrusion die is automatically optimized using a parametric based three-dimensional polymer flow simulation algorithm. The optimal parameters determined by the optimization algorithm are input to a parametric-based computer-aided-design program to yield tool path for die fabrication. A prototype coat hanger die is fabricated according to the material selection and process conditions specified. Experimental flow distributions match the predicted flow distributions within acceptable experimental error. Because this approach employs three-dimensional flow analysis, it can readily be extended to profile die design.

Automobile companies are looking with increasing frequency at composites (engineering polymers based matrix) to reduce weight, cost and to improve the recyclability of their powertrains.Air Intake Manifolds (AIM's) and Integrated Air/Fuel Systems (IAFS) have emerged as prime candidates for conversion from metal to composites and market penetration in North America is above 80%.This paper will present the state of the art for materials in these applications including real life examples and analysis.Also we will share some of DuPont new offerings in these market that provide significant system cost reduction while performing better in a more demanding environment.

Ballistic performance of fiber-reinforced composites with different fabric structures and configurations was studied. Composites with Kevlar-KM2 ripstop fabric performed better against smaller size projectiles due to the effective fiber failure through constraining of the fibers, while hybrid composites constructed from ripstop fabric of Kevlar-KM2 and Spectra-1000 show an advantage with larger projectiles due to the effective strain energy absorption. Hybrid composite configuration of these two structures exhibited overall performance improvement.

Fundamental deformation-structure relationships in melt cast amorphous Poly(lactic acid) (PLA) films were investigated using a stretch birefringence apparatus that allows for direct measurement of true stress, true strain, and birefringence at realistic strain rates. The relationships between stress, strain, and birefringence are strongly affected by the processing conditions: temperature, stretch ratio, and stretching rate. The molecular mechanisms of this deformation and the effects of process variables on these are elucidated in this study.

In this current paper, we are discussing basic principles in materials selection, which focused on utilization of the light alloys for manufacturing of fasteners for thermoplastics applications.Proposed fastener(s) material replacement (from steel to aluminum) will allow to manage the stiffness considerations, short-term (strength) and long-term (life) performance of the assembled plastic parts for various automotive applications.The results from this investigation provide recommendations on materials pre-selection for the design of fastened thermoplastic components with improved mechanical performance.

In the plastics industry today and as has been since the start of plastic extrusion, the end user has depended on the Original Equipment Manufacturer (OEM) and/or screw manufacturer to supply them with the proper screw design for their material and process. Most processors have learned over the years a few critical points pertaining to screw design, but never totally understanding the reason why their suppliers have recommended certain aspects to the screws that they have purchased. Hopefully, this paper will explain some of the basic knowledge needed in order for an end-user to make the proper decisions when using or purchasing a new single screw for a smooth bore application.

The changes in the birefringence and the true stress-true strain behavior of cast nylon 6 and nylon 6-clay nanocomposite films are monitored online as they are stretched uniaxially below the peak melting temperature. The effects of draw temperature (100°-140°-180°C) and clay content (2 and 5 volume%) are investigated by means of online measurements and X-ray diffraction. The presence of nanoplatelets in the nylon matrix enhances the uniformity of stretching by suppressing the localized necking behavior at these essentially cold drawing temperatures. At a given stress, the birefringence decreases as the clay content increases. This is quite interesting and perhaps is related to reduction of structural connectivities by reducing the polymer entanglements in the presence of these very small nanoparticles. The development of birefringence correlates well with the strain rather than the clay content or the stretching temperature. The crystalline phase of the as-cast films is ?-form. Stretching promotes the formation of ?-crystals at all draw temperatures for nylon films. At low draw temperatures, the nanocomposite films also assume ?-phase, while at 180°C they display a mixture of ? and ? phases.

The purpose of this study is to investigate the biaxial stretchability, the structure developed, molecular orientation and shrinkage of linear low-density polyethylenes (LLDPEs) biaxially stretched using a laboratory biaxial stretcher. Seven resins having different molecular characteristics were used in this study. The effect of stretching temperature and rate on stretchability is assessed. Biaxial orientation factors for the crystalline axes as well as that of the amorphous phase were determined using FTIR spectroscopy. SEM was used to reveal the details of the crystalline stacking and shrinkage of the films was determined.

Polypropylene (PP) and Polycabonate (PC) is an immiscible polymer pair. When blended together, it separates into two phases. It generally yields poor practical properties. The final morphology of the blend has a controlling influence on its mechanical properties. In this study, Functional Polyolefin Elastomer (FPOE) is used in the blends of Polypropylene (PP) and Polycabonate (PC) as a compatibilizer to control the morphology and to strengthen the interfaces in this blending system. With addition of FPOE, the size of PC domains is reduced and interaction between different phases is greatly improved. The mechanical property of the blends with FPOE, such as impact strength, is significantly improved. FPOE can be applied for the blending of PP and PC as a new effective compatibilizer [1-8].

The mechanism of LLDPE blown film blocking has been investigated. Film specimens exhibiting different levels of blocking force were fabricated using resins with various molecular characteristics. The film surface morphology and the chemical composition were studied. Atomic Force Microscopy observations allowed to link clearly blocking with the formation of a soft layer at the films interface. This layer is made of amorphous PE chains, migrated from the bulk of the film during conditioning at 60°C. No evidence of co-crystallisation at the interface was observed. The chemical nature of the soft layer has been derived from its mechanical properties. A predictive model for film blocking is proposed based on a single molecular parameter.