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.
The Processing of Renewable Resources Using a Short Single Screw Extruder with a Combined Section for Solid Conveying and Plastification
Due to the growing awareness of the necessity to protect the environment, the substitution of conventional plastic materials by biodegradable materials is gaining an ever increasing importance. An application that makes sense especially with regard to economic aspects is the processing of non-modified crop on plastics processing machines. This is made possible by the concept of a single-screw extruder equipped with a metering unit with which the total amount of energy required to plasticize the material is generated exploiting the friction occuring in the solid matter. As opposed to conventional extruder designs which exhibit separate areas for conveying the material and for plasticizing the same, these two tasks are united in one section of the extruder. The concept is based on specific geometries of screw and cylinder which secure that the entire mass flow passes a shear zone situated in the material conveying zone, warranting a very efficient transmutation of energy.
Toughening of Epoxy Resins by Partially Decomposed Polyurethane Waste
Hygrothermally decomposed polyurethane (HD-PUR) of polyester type has been used as a cost-efficient impact modifier in tri- and tetrafunctional epoxy (EP) resins. The PUR modifier was added between 5 and 80 wt.% to the EP prior its crosslinking with a diamine compound (Diaminodiphenylsulphone, DDS). The fracture toughness (Kc) and -energy (Gc) of the modified resins were determined on static loaded compact tension (CT) specimens at ambient temperature. The mean molecular weight between crosslinks (Mc) was determined from the rubbery plateau modulus of dynamic mechanical thermal analysis (DMTA) spectra. The change in the Kc and Gc as a function of Mc followed the prediction of the rubber elasticity theory. The efficiency of the PUR modifier was compared with that of a carbonyl terminated liquid nitrile rubber (CTBN). DMTA and fractographic inspection revealed that the PUR modifier was not only present in a dispersed phase of the EP matrix but participated in the build-up of the EP crosslinked network structure. Thus HD-PUR works as active diluent and phase separating additive at the same time. As HD-PUR can be regarded as an amine-functionalized rubber, it was used as hardener alone (by replacing DDS) in some EP formulations.
Utilisation of Fly Ash as a Filler in Plastics
Fly ash is a by-product of the ground coal burning process used in power generation plants. Since fly ash primarily consists of inorganic materials, it is a potential filler substitute for conventional fillers in the plastic industry. In this work, the mechanical, physical, and thermal properties of fly ash filled polypropylene were determined and the effect of adding fly ash on the properties of the resin was studied. Driven by the economical potential and environmental aspect of the usage of fly ash, this study enabled us to determine the viability of coal fly ash to be used as a substitute filler in plastic resins.
A Rational Way to Reduce Number of Colorants Used
The number of colors or colorants used in your operation takes on a life of its own, ever growing in size and complexity. There are valid reasons for the growth; to better match colors, satisfy a key customer, gain more heat or light stability, improve cost or processing properties, more reliable supply or to provide a specialty product. At the time each one is introduced we are typically under some driving force to satisfy a tactical need, what the heck its just one more item, and we lack the time to take a more strategic view. Next thing you know the number has grown from 80 - 100 items to 300 or more! So, do you really need that many colors? If you had fewer colors, your operations would be much simpler and simplicity implies better, less costly more reliable operating. So why not do the job with 50 colors. Well why stop there, why not 20 or maybe 16, shucks the rainbow only has 7, ROYGBIV. You know, we see all the colors on a TV screen or CRT & they are made from just Red Green & Blue, why not 3 colors? This paper will deal with the issue of what is the right number of colors, how you can go about getting there (and maybe staying there) and finally some of the benefits you might expect.
Blends of Recycled Polyethylenes and Metallocene Impact Modifiers for Rotational Molding
This paper describes the development of blends of recycled polyethylenes suitable for rotational molding. The blends consist of recycled post-industrial polyethylene resins and polyolefin plastomer impact modifiers, produced by single-site (metallocene) catalysts. The rheological properties of the blends were found to be favorable for rotational molding. Rotomolded parts provided satisfactory low temperature impact strength and good tensile properties.
Conductive TPO for Electrostatic Painting
The TPO (Polypropylene/Elastomer) market for injection molded automotive bumper fascia is driven by cost reduction, a balance of physical properties, ease of processability, and desirable aesthetics. Global volume for this application was approximately 740 MM lbs. in 1999, nearly half of which is electrostatically painted. Decreased application costs, increased productivity, and reduced environmental emissions can be realized through system optimization. This report describes the rheological and morphological phenomena governing the development of a conductive TPO (CTPO) for enhanced electrostatic painting.
Application of Chemo-Rheology to Establish a Process Window for a New Solventless System to Manufacture Pre-Pregs and Laminates for Electronic Applications
The most common commercial processes for manufacturing pre-pregs for electronic applications use solvent-based epoxy systems. Solvents are environmentally unfriendly and contribute to voids in the pre-preg and laminate. Voids cause product variability, which is a major source of scrap in board shops. In this paper, we use chemo-rheological and kinetic measurements to identify a potential epoxy-based resin system for a solventless process, based on injection pultrusion. DSC and rheological data show that the candidate system does not react appreciably without catalyst to temperatures of 170°C or with catalyst at temperature below 110°C. The system solidifies below 105°C. It was found that the overall viscosity of the resin system is dependent upon the temperature, degree of cure, and filler content. Kinetic rate and viscosity rise expressions to be used in process modeling and optimization have been developed. A preliminary process window for the process has been established.
Biodegradable Plasticizers for Polylactic Acid
Poly(lactic acid) [PLA] is a well known biodegradable polymer which has been used in drug delivery systems, surgical repair systems such as sutures and bone fracture fixation pins and screws. PLA is biocompatible, has a high tensile strength, and has a high elastic modulus[1,2]. However, one drawback of PLA is the low elongation at break due to a brittle fracture while under tensile and bending loads. The elongation at break of PLA is typically 3 - 5 percent. The reason for this brittle behavior is due to physical aging which occurs during storage at room temperature and has been studied extensively. Plasticization is a common technique used to increase the ductility of a brittle polymer. In the case of PLA a suitable plasticizer must be miscible with PLA so as to decrease the glass transition temperature, as well as be biodegradable and nontoxic so as to provide a useful biodegradable blend. The advantages of the plasticization are low cost, ease of processing, and the ability to alter the properties of the blends by varying the amount of plasticizer. Use of a functionalized plasticizer can be more desirable such that a chemical bond is formed with the PLA polymer thereby preventing loss of the plasticizer through migration.
Blends of Starch with Poly(Vinyl Alcohol)/Ethylene Copolymers for Use in Foam Containers
The use of foamed polymer packaging such as polystyrene (PS) cups, bowls and clamshells has decreased in recent years because of perceived environmental disadvantages. Blends of starch with poly(vinyl alcohol-co-ethylene), PVOH, a degradable, water-resistant polymer, were processed into viable alternatives to PS providing degradable polymers from renewable resources. Modulated DSC and X-ray crystallography were used to characterize the miscibility and morphology of extruded starch/PVOH blends that contained a series of plasticizers. These included combinations of water, glycerol, triacetin, citrate esters, and amino acids. The optimal blend formulation, based on miscibility, strength, aging characteristics, and capability to replace PS foam was--60-65% wheat starch, -25 -30% PVOH, and -5-10% plasticizer.
Blends of Various Proteins with Poly(Hydroxy Ester Ether)
Blends of poly (hydroxy ester ether) (PHEE), a recently developed bisphenol A ether-based synthetic biodegradable thermoplastic polymer, with a soybean protein isolate and two hydrolyzed wheat glutens were studied. Blends of the proteins with PHEE were produced from 20-70% by weight of protein content. The Young's moduli of the protein/PHEE blends falls in the range of 0.8 - 1.5 GPa with the tensile strengths ranging from 10-30 MPa. Fracture strengths of the blends ranged from 9-2 MPa-m1/2 depending on the amount of protein added. Morphological analysis indicated acceptable adhesion between the protein and PHEE phases in the blends. In general, as the protein content was increased the materials lost ductility and failed in a brittle manner; however, the mechanical properties of several compositions were comparable to current commercial thermoplastics such as polystyrene.
Combined Process Variables and Process Energy Monitoring for Injection Moulding
Good injection moulding machine control is a necessary requirement for control of the process, however there is an acknowledged lack of process understanding, related in turn to a lack of understanding of the polymer under process conditions which inhibits the development of standardised route to process control. In our laboratory, specific pressure indices in an identified low noise region of the primary injection stage of injection moulding have been found to provide a sensitive indicator of changes in a polymer, including batch to batch changes and process-induced changes, which in turn allows meaningful Statistical Process Control to be undertaken. Growing concern for environmental issues, including international standards agreements such as ISO14001, demonstrate a clear requirement to conserve energy for both environmental and cost issues. Detailed energy measurements on injection moulding machines both in the laboratory and in industry demonstrate the potential of process energy measurements as an aid to the development of a systematic management approach to the environmental concerns of an organization. Laboratory DOE studies allow a further insight into the influence of a variety of machine variable settings on the total energy consumption. We are currently in the process of combining both process variable and process energy measurements, to provide processors with the richest level of process information.
New Advances in Torque Rheometry
The torque rheometer has been an essential instrument for a wide spectrum of research and development and quality control testing laboratories throughout the years. The torque rheometer has evolved just as quickly as advances in material chemistry. Highly sophisticated software and hardware technologies have now been introduced to better serve the needs of a modern laboratory. New challenges in such areas as plastics recycling and environmentally friendly fillers for plastics are some of the needs being met by using this multifunctional instrument. This paper intends to discuss how these changes have made the instrument more relevant than ever.
Degradation Mechanisms of Thermoplastic Polyurethane Resins
The use of polymeric materials for transparent, lightweight armor has been of great interest to the U.S. Army for a number of years. Field items such as goggles, lens, face and windshields are currently manufactured using advanced polymeric plastics. These items are designed with polymers that provide excellent optical clarity, rugged abrasion resistance, and high ballistic impact strength. However, as with any organic polymer system, these materials are susceptible to degradation over time when exposed to various environmental (i.e. sunlight, moisture, temperature) conditions. This structural degradation (1-4) will eventually comprise the original integrity of the materials' desired properties. In this study, the impact of accelerated weathering upon newly developed polyurethane based thermoplastic materials was investigated. A fluorescent ultraviolet (UV)/condensation weathering tester was selected for the exposure study. The materials were characterized by UV/VIS spectroscopy and FT-IR spectroscopy. The results reveal that the urethane linkages undergo a scission reaction upon UV exposure drastically affecting the mechanical properties of the material. Furthermore, these urethane scissions produce a yellowing of the polyurethane which can inhibit its use where optical clarity in important.
Development of High Quality Recycled Polyethylene Resins for the Replacement of Virgin Resins
Dairy and fruit juice bottles are a major source of post consumer recycled high density polyethylene (PCR HDPE). The recycled HDPE has limited post-consumer applications due to its poor stress crack resistance (SCR). This paper presents a review of a test method for SCR and some preliminary results of the development of recycled HDPE blends with improved SCR. The improvement has been achieved with the addition of a modifier, and results indicate that there is a potential to incorporate the use of recycled HDPE in non-pressure pipe applications. These customised blends have been tested for SCR according to the Notched Constant Ligament Stress (NCLS) test. The NCLS test is a new test method (ASTM F17.40) which is currently under development. The NCLS test will be used to determine the susceptibility of HDPE resins to slow crack growth (SCG) under a constant ligament stress in an accelerated environment. The results from the test will subsequently be correlated with field performance results.
Environmental Lining Systems - Raising the Standards
Annually, the United Kingdom deposits around 20 million tonnes(1) and the United States around 2 billion tonnes(2) of waste into landfill. To protect the environment from the harmful effects of leachate from the waste, landfill sites are protected using a system of thermoplastic liners, typically made from polyethylene. Due to manufacturing limitations on the size of the lining sheets, welding is employed to join adjacent sheets at the landfill site. This paper reviews current welding practices, the industry approach to quality, and discusses the moves towards certification of welding personnel in order to raise standards across the industry.
Environmental Stress Cracking of PC in Contact with Aqueous Solutions
The environmental stress cracking (ESC) behavior of some plastics is very well examined. Especially for polyethylene the mechanisms are nearly clear. For amorphous thermoplastics this mechanisms were examined in many researches, but are still not really clear. Especially for polycarbonat (PC) in contact with aqueous solutions systematic examinations of the ESC behavior are rare. In this paper examinations of the ESC behavior of PC in different aqueous solutions are presented. The tests were done by a medium-tensile-creep test. Different pH-values of water and a surfactant were examined about their influence on the ESC behavior. Also distinctive types of PC and their influence on the ESC behavior were examined. It is determined that the ESC of PC in contact with aqueous solutions is not only, like classical approach, controlled by physical effects. A large effect of chemical mechanism is also part of the failure mechanism.
The Effect of Blending on the Viscosity Reduction of Recycled Milk Bottle Grade HDPE
Post-consumer plastic waste in Australia contains over 50,000 tonnes p.a. of HDPE blow moulded bottles, with half still ending up in landfill. Recycled milk-bottle grade HDPE is known to be too high in molecular weight for processing by injection molding. In this study, the target was to make injection-molded compositions with a content of the recycled material of 75% or higher by blending with commodity plastics. The results of rheological, thermal and mechanical studies of the blends are presented.
Environmentally Friendly Plasticizers for Polyvinyl Chloride (PVC) Resins
There has been increased interest in developing alternatives to phthalate plasticizers used in the processing of polyvinyl chloride (PVC). This paper describes research on modifying the composition of vegetables oils such as soybean oil for use as primary plasticizers for PVC. Advanced computational chemistry and modeling studies have been conducted to correlate structures of modified soybean oil with their compatibilities in PVC resin. The new soy oil derived plasticizers have excellent plasticizing efficiency with significantly reduced migration and volatility. Properties and performance of the new modified soy oil compositions as primary plasticizers in typical PVC formulations are summarized and compared to those of a standard phthalate PVC plasticizer.
The Recycling of Thermoset Materials into Thermoplastic Composites
Thermoset process scrap costs companies millions of dollars annually. Specific thermoplastics could benefit from the addition of recycled thermoset material. The incorporation of thermoset regrind into thermoplastic material would provide a viable alternative for the thermoset scrap that is currently sent to the landfills.
Extrusion/Compression of Long Fiber Thermoplastic Composites
It is becoming common for long fiber-reinforced thermo-plastics (LFT) to replace existing GMT-type applications as well as to capture new applications. This is especially true in the European automotive industry, where the market for parts made from LFT is experiencing tremendous growth. The following paper discusses the available materials, the mechanical and physical properties, machine techniques and processing details of the LFT process. It will also discuss potential applications for LFT. The paper will cover different process techniques such as direct processing and make comparisons with other processes. An explanation on the effects that LFT has on properties and economics will be made. It will show how the economics can be improved by adding recycled material to the process. This paper will provide a better understanding of the LFT-process and how you could get benefits from this process.
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