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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Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.
Evolution of Structural Hierarchy in Uniaxially Deformed Poly Lactic Acid Films as Followed by Spectral Birefringence Technique and Others
Polylactic acid, PLA, is a relatively new biodegradable polymer primarily used for biomedical as well as mass-market packaging applications. PLLA is a polyester comprising repeating units of the lactide residue with an asymmetric carbon atom. Because of its biodegradability to nontoxic products and good plastic properties of that polymer makes it suitable for use in film studies. De Santis and Kovacs showed that the unit cell of PLLA is pseudo-orthorhombic with dimensions of a=10.7 Å, b=6.45 Å, c= 27.8 Å and ?=?=?=90°, where the molecules assume a 10/3 helical conformation. (1).Eling et al reported the existence of another modification, which they called ?-crystal modification (2) Hoogsteen et al. studied the influence of the preparation conditions on the presence of the crystal modification (3). Fischer et al investigated solution grown crystals of lactide polymers (4). Also Kalb and Pennings estimated the crystallization of PLLA from bulk state and solution (5). Tadakazu and Masuko investigated the relationship between the fine structure of PLLA and its physical properties (6). The need for polymeric biodegradable films is well established. The use of films occurs in the packaging and disposable article industries. In light of depleting landfill space and adequate disposal sites, there is a need for biodegradable films. Currently films from nylon, polypropylene, polyethylene, polystyrene, PVC, are noncompostable, which is undesirable from an enviromental point of view (7). In this paper, we present our results on the development of structure in uniaxial and biaxial stretching of PLA and subsequent heat setting process as followed by the new spectral birefringence technique we adapted for rapid acquisition of birefringence during the course of heat setting.
Time Dependent Crack Growth in Polyethylene with Emphasis on Environmental Attack
This research seeks to determine the effect of chlorinated hot water on slow crack growth resistance in polyethylene using a test methodology that is quick and inexpensive. This will be done through the use of three point bend tests on specimens completely immersed in a bath of chlorinated hot water. The results will then be compared with results from the same test run without chlorinated hot water. Comparative data will be used to determine chlorine's effect.
Fish Oil Polymeric Systems: Synthesis, Structure, Properties and Their Relationships
Fish oil or conjugated fish oil was copolymerized with divinylbenzene and norbornadiene or dicyclopentadiene using BF3·OEt2 as an initiator in an effort to develop useful biodegradable polymers with rationally designed structures from natural renewable resources. Dynamic mechanical analysis, DSC, TGA and nuclear magnetic resonance spectroscopy have been used to characterize the resulting fish oil polymers. The results show that viable fish oil products ranging from rubbers to hard plastics may be synthesized by changing the type and amount of the comonomers used. The fish oil products are thermosetting polymers having highly crosslinked structures, glass transition temperatures ranging from 50 to 130°C, room temperature modulus of about 109 Pa, and excellent thermal stability, making the products useful for applications where current biodegradable plastics are not useable.
Hyperboidal Rotary Cutter - Modeling and Application in Recycling of Polyethylene Film in Pelletizing-Line Aggregation
Recycling of polyethylene films  is carried out by their disintegration into regular flakes - the process is difficult because of dimensional (large surface, small thickness) and property (flexibility and rebound) characteristics of the films. The disintegration is typically carried out with the knife mills  which constitute the first units of the recycling line. Traditional mills operate on the principle of pressurized knife cutting  since it allows to carry on the disintegration at a narrow slit between cutting edges of the fixed (stationary) and the mobile (rotary) knives of the mill. Because of parallel arrangement of the edges and large surfaces of the films which call for high cutting forces the process induces strong vibrations [3, 4]. The latter are eliminated in the hyperboloidal - rotary cutting mill developed recently and evaluated in our lab .
In-Line Granulation - A Key to Reduced Edge Trim Recycle Costs
In-line granulation, the size reducing of plastic trim as it comes off an extruder, tenter, frame, slitter or other production machine has many advantages over conventional trim handling methods. Small granulator size is an inherent requirement because of the limited installation space around these production machines and sound pressure levels must be low because of the proximity of the granulator to the machine operator. Precision Cutters, Inc. (PCI), has developed a unique line of small, very efficient, high productivity in-line granulators that meet all size and operating requirements for use in this advanced, closed, one-step trim to granulate process. The engineering principles of film granulation and throughput rates in kgs/kw-hr (lbs/hp-hr) are covered.
Mechanical and Thermal Properties and Leacheate Analysis of Carpet Residue/Polyethylene Prototypes for Building and Construction Applications
A complex carpet residue is obtained as a byproduct in the tertiary recycling of nylon-6 fibers from used carpets. It consists of mainly polypropylene, styrene-butadiene rubber and calcium carbonate, and is potentially a low cost, high volume waste stream with consistent properties. In this study, composites of carpet residue with polyethylene were evaluated for building and construction applications. As received carpet residue was first compounded with low density polyethylene, homogenized and devolatilized in a twin screw extruder. Later, blocks were prepared by the intrusion process and tested for their mechanical and thermal properties as well as the leaching characteristics of heavy metals and organic carbon. It was demonstrated that the prototypes of these blocks can be potential candidates for use in a novel thermal spacer application.
Mechanical Behavior of Fabric-Film Laminates
Inflatable structures are gaining wide support in planetary scientific missions as well as commercial applications. For such applications a new class of materials made of laminating thin homogenous films to lightweight fabrics are being considered as structural gas envelops. The emerging composite materials are a result of recent advances in the manufacturing of lightweight, high strength fibers, fabrics and scrims. The lamination of these load-carrying members with the proper gas barrier film results in a wide range of materials suitable for various loading and environmental conditions. Polyesterbased woven fabrics laminated to thin homogenous film of polyester (Mylar) are an example of this class. This fabric/film laminate is being considered for the development of a material suitable for building large gas envelopes for use in the NASA Ultra Long Duration Balloon Program (ULDB). Compared to commercial homogenous films, the material provides relatively high strength to weight ratio as well as better resistance to crack and tear propagation. The purpose of this paper is to introduce the mechanical behavior of this class of multi-layers composite and to highlight some of the concerns observed during the characterization of these laminate composites.
Mechanochemistry Effects in Recycled Polypropylene and its Blends during Solid-State Shear Pulverization (S3P)
On-going research focuses on understanding the mechanochemistry during Solid-State Shear Pulverization (S3P) of recycled polypropylene (PP) and its blends. Free radicals formed during this process act as compatibilizing agents for ordinarily incompatible polyolefin blends. It was observed earlier with Nuclear Magnetic Resonance spectroscopy that each S3P cycle converts a small portion of polypropylene chains from isotactic to atactic stereoregularity. Small amounts of such atactic chain segments impart additional levels of toughness, which offset, in part, the damage associated with the inevitable chain scission. We determined how many processing cycles S3P-made recycled PP can endure without significant loss of mechanical properties.
Modification of Cement Using Post Industrial Recycled Acrylonitril Butadiene Styrene (ABS) Latex Powder
Polymer latex modification of cement has increased the ductility of the resultant concrete. However, practical application of the concrete is limited since latex is used in a liquid form. In contrast, we have examined use of post industrial Recycled Acrylonitrile Butadiene Styrene powder (r-ABS). Pullout tests indicate an increase in adhesive bond strength between the polymer-modified mortar and steel re-bar. Thermogravimetric analysis is carried out to examine the influence of the latex on the kinetics of degradation. The results indicate a novel approach of using r-ABS in cement modification.
New Uses for Electroless Nickel in Mold Building and Design
This paper describes electroless nickel and the scope for its many applications in mold making, maintenance and repair. While most mold builders are familiar with nickel solution for rust prevention in cooling water lines, many have remained unaware of the different formulations of electroless nickel plate and its capabilities as an engineering or functional coating applied by techniques firmly established in the electronics, fire-arms, automotive and other industries. Case histories of in-mold performance illustrate correct usage, proving that electroless nickel can offer properties equivalent to hard chrome plate, yet without the problems of thickness variation, anode deployment or the ever-rising environmental penalties and costs associated with chrome plating.
Nylon 6,6 Glass Reinforced Composite Material for Automotive Air Intake Manifold Application
There are many advantages to air intake manifolds molded from Nylon 6,6 Glass reinforced composite material versus a pressure-cast aluminum manifold. Weight is significantly lowered and production costs generally are reduced. Performance improves with the precise control of the interior surface finish and reduced air induction temperatures. The Nylon 6,6 Glass reinforced composite material can be molded into intricate shapes by injection molding or lost-core process with reduced machining operations as well as Nylon 6,6 material is easily recycled. Production costs will continue to decrease as optimization of material, process and part integration increases. This study evaluates Nylon 6,6 Glass reinforced composite material in terms of the intake manifolds material key requirements such as thermal, heat aging, fatigue, impact, creep, stress and chemical resistance including multi fuels. This study would assist engineers in designing intake manifolds using Nylon 6,6 Glass reinforced composite material.
Opportunities for Solid Freeform Fabrication in Prototyping and Manufacturing
Solid Freeform Fabrication (SFF) of parts and components is an area of active development and tremendous potential. SFF is a layered manufacturing technique in which the required component/part is built from a CAD model. This model is mathematically sectioned into a number of layers and a material deposition or tool path is generated for each layer. A fabricator uses this tool path information to build the part, layer by layer. This family of manufacturing techniques offers several advantages over traditional routes, such as: no part specific tooling, fabrication of complex geometries to net shape, and greater design flexibility. There is also a significant potential for lowering cost of prototyping as well as small-scale manufacturing. Many of the SFF routes that are currently available are for fabrication of plastic, ceramic and metal parts. Some of these SFF techniques are, Stereolithography (SLA) Laminated Object Manufacturing (LOM) or Computer-Aided Manufacturing of Laminated Engineering Materials (CAM-LEM), 3D Printing (3DP)/Sander Prototyping (SP)/Droplet Deposition, and Selective Laser Sintering (SLS). Most of the SFF routes are similar in concept, i.e., model generation, followed by mathematical sectioning and layerwise building, and differ only in the method of layer fabrication. In order to manufacture ceramics and metals, the polymer based SFF methods have been adapted using powders as a second phase in a base polymer or fluid. Parts can then be made directly or indirectly. In the direct route, a green ceramic part is directly manufactured to shape. Alternately, in the indirect process, parts are made by infiltrating a ceramic or metal slurry into a polymer or metal mold made by SFF. Subsequent processing of these green parts (i.e., debinding/drying and sintering) is similar to that of traditionally manufactured components and results in a near net shape sintered part.
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.
Pressure Shear Pulverization (PSP) Process for Thermoplastic and Thermoset Waste
A novel process of pulverization known as Pressure Shear Pulverization (PSP) process has been developed for thermoplastics (PE, PP, PS, PVC, PA, PET and/or their mixtures), thermosets (polyurethanes and phenolics), composites, and various blends (thermoplastics and paper). PSP is a proprietary, non-extrusion process and is realized inside a specially designed pulverization head. It is very different from cryogenic grinding, various versions of solid state shear extrusion (SSSE), and other size reduction processes. PSP has several advantages, namely, high output, low specific energy consumption, and low cost of pulverization head. PSP process is capable of producing coarse to very fine particles by manipulating the processing parameters. This paper deals with the development of pulverization of pre-consumer cross-linked LDPE foam waste and LDPE/Paper mixture by PSP process. As a model system, the processibility and properties of virgin LDPE have been studied. Physical properties of LDPE foam waste and polymeric powder have been determined and compared to understand the behavior of polymer under the combined action of thermally and mechanically induced stresses. Lab-scale and pilot-scale PSP machines have been designed and constructed.
Processability and Trends in the Mechanical Properties of Low Density Polyethylene Parts Produced Using Increasing Levels of Commingled Recyclate as a Filler
As the plastics industry is increasingly confronted with environmental demands and regulations, the need for successful and reliable recycling programs is greater than ever. One of the keys to the success of these recycling programs and to the success of recycled resins is identifying feasible end uses for commingled recycled polymers. One possibility is for plastics manufacturers to specify commingled recycled resins, as a filler, in their products. This can provide savings for the manufacturer, while helping to promote plastics recycling. When specifying the level of commingled recycled resin to be used in a product, the designer must consider the net effect it will have on the processability and the mechanical properties of the part. This study will examine and attempt to predict the net effect of increasing the level of commingled post-consumer and post-industrial recyclate, used as a filler, in the production of low-density polyethylene parts.
Rapid Heating and Curing of Structural Adhesives by Infrared and Radio Frequency
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.
Recycling of Xerographic Toners
The objective of this research is to find ecologically and economically acceptable routes to utilize excess xerographic toner from manufacturing and returned toner cartridges. This black toner is a polymer composite comprised of a styrene-based copolymer, carbon black and other additives. The mechanical properties of toners are specifically designed to allow attrition to 10-20 µm particles. Thus the bulk mechanical properties are not desirable for load bearing applications typical of consumer plastics. Reactive and non-reactive blending of toner with other polymers have been used to enhance the mechanical properties. The blends and alloys produced exhibit a transition from brittle to ductile behavior as exhibited by impact energy data. Thus a family of polymeric systems of variable properties versus cost compromise can be created.
Reusing XLPE from Electrical Cable Waste: Cable Separation, Processing and Blend Properties
The recycling of power transmission cable was investigated by using different kinds of separation and reprocessing methods. The cross-linked polyethylene (XLPE) insulation of the cable, serving as a part of a broader study of the reprocessing of cross-linked thermoplastics, presented a specific challenge in separation. Separation of the XLPE from the other components of the cable was attempted by thermo-chemical, microwave and thermo-mechanical means. All three methods were able to separate the cable, and the relative advantages and disadvantages are discussed. Following separation, the following processing techniques were attempted: compression molding, extruding, and injection molding with and without preheating XLPE crumb. It was found that by preheating the XLPE and injection molding with high injection pressure, the neat XLPE could processed. Possible mechanisms for the flow and reconsolidation of XLPE crumb were hypothesized and investigated. Blends of XLPE crumb (0.3 to 3 mm particles) in either HDPE or LDPE were prepared and the tensile properties were evaluated.
Snap Tie Cones Made from Recycled PET and HDPE
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.
Stress Relaxation of Polyolefin-Based, Oriented, Glass-Fiber Materials
Samples of recycled plastic lumber constituted of a mixture of two different polyolefins and an inorganic glass were subjected to short-term stress relaxation tests. In addition, stress-strain tests were carried out at different rates of stress and strain for both full-sized lumber profiles and smaller samples machined from the larger pieces. The results from the short-term stress-strain tests were used in conjunction with a mathematical model to calculate values of stress as a function of time for the relaxation experiments. Calculated values are in good agreement with experimental stress relaxation data. The feasibility of extending this model to predict long-term time-dependent behavior is discussed.
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