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.
This work probes a hypothesis for initiation of environmental stress cracking (ESCR) based on a thermodynamic criterion for localized stress induced swelling. The threshold metric involves observation of solid-vapor surface energy and contact angle of a liquid on a loaded polymer substrate and thus inference of solidliquid interfacial surface energy with respect to substrate stress. The intent is to develop a screening technique for ESCR that is not limited by the kinetics of the crazing event.
Biobased neat unsaturated polyester materials containing epoxidized methyl soyate (EMS) and their clay nanocomposites were processed with cobalt naphthenate as a promoter and 2-butanone peroxide as an initiator. A certain amount of unsaturated polyester resin (UPE) was replaced by EMS. The combination of the UPE and EMS resulted in an excellent combination, to a new biobased thermoset material showing relatively high elastic modulus and the constant glass transition temperature with up to 25 wt.% replacements with EMS. Izod impact strength was almost constant while changing the amount of EMS and adding clay nanoplatelets.
Three types of polylactide (PLA) composites, namely, PLA/nanoclay, PLA/core-shell rubber, and PLA/nanoclay/ core-shell rubber were melt compounded via a co-rotating twin-screw extruder. The effects of two types of organically modified nanoclay (i.e., Cloisite®30B and 20A), two types of core-shell rubber (i.e., Paraloid EXL2330 and EXL2314), and the combination of nanoclay and rubber on the mechanical properties of the composites were investigated. In comparison with pure PLA, both types of PLA/5wt% nanoclay composites showed an increased modulus, a slightly reduced tensile strength, a similar impact strength, and a significantly reduced strain at break. PLA/EXL2330 composites with a rubber loading level of 10wt% or higher exhibited much higher impact strength but lower modulus and strength when compared to pure PLA. The simultaneous addition of 5wt% nanoclay (Cloisite®30B) and 20wt% EXL2330 resulted in a PLA composite with a 134% increase in impact strength, a 6% increase in strain at break, a similar modulus, and a 28% reduction in tensile strength as compared to pure PLA.
Polymeric and composite materials from plant derived fiber (Natural/Bio-fiber) and crop-derived plastics (Bio-plastic) are novel materials of the 21st century and have the potential to be of great importance to the materials world, not only as a solution to growing environmental threat but also as a solution to alleviating the uncertainty of petroleum supply. As this new generation of biobased polymers enters the commercial market, success in competing with established petroleum based polymers will depend on their performance, properties and cost as determined primarily in the commercial marketplace. While environmental consciousness continues to grow, and some governmental programs have been established to assist with the entrée of biobased materials into the marketplace. E.g., the US Research and Development Act of 2000 along with Presidential Executive Orders 13134 & 13104 and the “Farm Bill” signed by President Bush on May 13, 2002, have a goal of achieving a performance/cost ratio competitive with petroleum-based polymers for value-added applications. The technology road map for plant/crop-based renewable resources 2020, sponsored by the U.S. Department of Agriculture (USDA) and the U.S. Department of Energy (DOE), has set a goal of increasing the utilization of basic chemicals from biobased renewable resources of 10% by 2020, and further increase to 50% by 2050.While the chemistry, reaction pathways and processing steps to producing biobased chemicals and polymers are relatively straight forward, it is the use of these materials in high performance, value-added applications that will be critically important to achieve sustainability and economic viability. The most promising path to achieve sustainability and economic viability is through the addition of biofibers to biobased polymers to produce biocomposites. Research underway in the Composite Materials and Structures Center at Michigan State University and other Universities has been directed at defining, de
Diabetes is one of most common and widespread diseases. As high as 6% of the world population suffers from diabetes, which, including its complications, is the fourth most important cause of mortality and the main cause of permanent blindness. In the United States alone, 16 million people, nearly one in 17 people, have diabetes. More than 2,000 new cases are diagnosed every day. Most patients require three to four injections of insulin a day. In addition to patient compliance problems, chronic subcutaneous injection may cause side effects, such as lipoatrophy or lipohypertrophy. Oral delivery of insulin has been elusive due to acidic and enzymatic degradation of insulin in the gastrointestinal tract.Oral delivery of insulin is more preferable to subcutaneous injections, because it may provide a better glucose homeostasis and decrease the chances of peripheral hyperinsulinaemia, which is linked to neuropathy and retinoendopathy. Successful oral delivery has not been achieved due to various challenges regarding the sustainability of peptides in the gastrointestinal tract. Typical oral bioavailability of proteins is generally less than 1-2 % because of the numerous physiological barriers in the digestive tract. Ingested proteins become subjected to acidic degradation in the stomach, luminal degradation by enzymes in the intestine, and intracellular degradation. Since proteins are built with peptide linkages, they are susceptible to acidic degradation. It has been shown that some proteins do have some bioavailability when administered directly into the intestine, bypassing the acidic milieu of the stomach.  Various polymer matrices have been designed for enteric coatings with adequate pH-response to protect insulin in the stomach. Polyacrylates Eudragit RS1 and RS2 showed bioavailabilities of 9.3-12.7 % due to their ability to release insulin further down in the gastrointestinal tract at pH 7.5-8.0. Polymer nanospheres have been studied for oral delivery. Accordin
In this study the co-extrusion and use of a cyclicalpha olefin and metallocene polyethylene for medical and packaging applications was investigated. The combination of these materials are cost competitive and provides the opportunities for an environmentally friendly disposal and possible recycling. A film with alternating polyethylene, cyclic- alpha olefin, and polyethylene layers was coextruded with the use of three extruders leading into a multi-layer feedblock. The film was tested for oxygen and water permeability, tensile properties, falling dart impact strength, and tear strength. An economic analysis of the fabrication of the film for the use in medical and packaging applications was also constructed. The study demonstrated that the co-extrusion of a cyclo-olefin and metallocene polyethylene provides an opportunity for environmental means of disposal and a means of fabrication.
Surface quality of profile extruded from recycled uPVC has been examined using a novel on-line visualization system and surface interferometry. A calibrated strip profile was extruded from various grades of recycled uPVC window frame. Surface defects were monitored using a high-frequency line-scan camera and categorised in terms of size, shape and position. Surface roughness was measured using a white light interferometer. PVC recovery method, batch variation and processing conditions were found to affect surface quality of the extrudate.
Polycaprolactone (PCL)/thermoplastic starch (TPS) biodegradable blends were prepared via a one-step extrusion system over the entire range of composition at different viscosity ratios. A detailed morphology analysis of the PCL/TPS blends was investigated by electron microscopy after selective extraction. Through a judicious combination of concentration control and processing conditions, the volume average diameter of TPS droplets can be closely controlled from 0.5 to 16?m. The rheological behavior of these blends is also examined in depth.
Some polymers based on renewable resources like starch containing materials can be plasticated by extrusion processing. Foams based on theses materials have an increasing importance in packaging applications, but also insulation materials have been developed. Starch contains water, which can work as a physical blowing agent for processing of these foams. The foaming process depends on process parameters like the pressure gradient in the die as well as on material properties like rheology. The main target is the production of foams with low density, high expansion ratio and a homogenous cell structure.The foaming process starts in the flow channel of the die. The cell nucleation process can be investigated by a die design with transparent inserts in the flow channel. The influence of process parameters on cell nucleation was determined. It could be shown that a higher pressure gradient in the die leads to a higher expansion ratio and thus to a later cell nucleation.Furthermore, the rheological properties also have an impact on the foaming behavior of molten starch. Shear viscosity is influenced by melt temperature, water content and mechanical energy input during the extrusion process. In this work, the dependency of the flow properties on process parameters was investigated in order to quantify the differences in pressure build-up caused by changes in screw speed and the resulting consequences on viscosity.
The chemical structure of crosslinked polyethylene (PEX) prevents easy reprocessability. Crosslinking of the polymer backbone covalently bonds it to another polymer chain. This bond prevents chain slippage and therefore any further melt processing. With an increase in time or temperature the crosslinking reaction will proceed, increasing its molecular weight to a point where it can not be processed a second time. The objective of this research is to determine a time window such that the crosslinked material can be reground and reprocessed using conventional melt processing equipment before the crosslinking reaction proceeds to a point where the material becomes unprocessable.
Biodegradable blends of amorphous Poly(lactic acid) (PLA) and polycaprolactone (PCL) have been developed by melt blending. The morphology of these materials was characterized by means of WAXD and TEM, showing that silicate layers of the kaolinite (chemically modified kaolinite) were intercalated and evenly distributed within the biodegradable matrix. Mechanical, thermal and gas barrier properties of the different blends and nanocomposites were studied and the effect of clay addition on the above-mentioned properties was evaluated.
Extensive use of plastic products in a country like the Czech Republic make the recycling of plastic unavoidable. This also is influenced by a host of factors such as increasing price of raw materials (oil and other semi processed products), growing concern for ecology and environment, etc. However, recycling is not only the technology alone, but it also includes issues such as legislation, both social and most importantly economics. The present study attempts to describe the economic conditions that influence the performance of plastic recycling companies. The paper analyses the conditions of development of plastic recycling companies in the Czech Republic using Economic Value Added (EVA) indicator.
Polylactide (PLA) polymers are among the most promising plastic made from renewable resources. Thermal stablization of these polymers remains a challenging issue of their industrial processing. We have studied the effect of TNPP in the scope of preventing the molecular weight reduction of PLA at its processing temperature. The stabilizing effect of TNPP was found to strongly depend on the concentration used.
In the last few years, UV curable coatings have gained great interest among numerous automotive OEMs and finishers because it allows for more efficient manufacturing, improved performance properties and an overall more environmentally friendly process. In consideration of this interest, the automotive lighting sector should be evaluated as a benchmark for early UV technology success as well as continued innovation in terms of appearance, performance and processing advantages.
In order to develop a potentially environmentally safe alternative to conventional paint removal methods we are investigating the enzymatic degradation of liquid polyurethane-based coatings and their films. A simple protocol for degradation has been developed using aqueous buffer solutions at 37 °C and an optimum pH. Two enzymes were selected, namely am esterase from Bacillus sp. and a protease (papain) that could potentially attack ester and urethane linkages. The extent of degradation was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and weight loss. Results indicate higher activity for the papain enzyme depending on the type of paint, enzyme concentration and conditions of application.
Use of mixtures of blowing agents in thermoplastic foam extrusion has been an industrial practice for a long time. However it has gained renewed interest in the past few years due to the introduction of difficult-to-process alternative gases, targeted as potential replacement for the banned ozone-depleting blowing agents. Reasons for blending physical foaming agents (PFA) are numerous. The incentives may be economical, environmental or technical. With respect to that latter factor, blending suitable PFA’s is often regarded as providing a better control of processing conditions. For example, a specific PFA could be selected for its inflation performance and blended with other co-blowing agents chosen for their stabilizing role. Although considerable amount of work has been done in that area, very little information has been disclosed in open literature.Carbon dioxide (CO2) has been reported as an interesting candidate for low-density polystyrene (PS) foaming, although the required concentrations are associated with high processing pressure due to the low solubility of the gas. Thus stable processing conditions are difficult to achieve. This work studies the effect of blending CO2 with ethanol (EtOH) as a co-blowing agent for PS foaming. Extrusion foaming performance of this mixture will be discussed, with respect to its solubility (i.e. degassing conditions) and rheological behavior. The function of each blowing agent during the process will be analyzed with respect to the plasticization, nucleation, expansion and stabilization phases. Attention will also be paid to the interaction involving the two PFA components.
The fracture behavior of two natural fiber composites was investigated. Tensile and fracture tests were performed on sisal reinforced HIPS and sisal/starch based composites. An increasing trend of stiffness with fiber content was found in both cases, whereas tensile strength decreased for sisal/HIPS composites. A maximum in sisal/HIPS composites quasi-static fracture toughness with fiber loading was observed, while they exhibited lower impact toughness values than HIPS. For the biodegradable composites, fracture toughness increased with fiber content and it depends on fiber orientation. In puncture tests, these composites exhibited higher values of fracture energy than neat matrix and fiber orientation affected the damage zone.
Polymer-based biomedical micro/nanodevices containing environmentally sensitive biomolecules are attracting increased interest. A critical requirement is the ability to assemble these devices at low temperatures in order to minimize denaturization. Studies of polymer thin films revealed that the properties at the polymer surface differed from those in the bulk. It was found that glass transition temperatures (Tg) at the polymer-air surface was substantially lower than the bulk Tg and increased toward the bulk value with depth from the surface. Subcritical CO2 could enhance the chain mobility and greatly depress Tg near the surface. Benefiting from this, we successfully demonstrated low temperature bonding of polymeric micro/nanostructures. The original micro/nanostructures are perfectly preserved after bonding.
The study investigated the growth and adhesion of normal human osteoblasts (NHOst) to two different biodegradable systems. These materials included polycaprolactone (PCL) and polycaprolactone/ hydroxyapatite (PCL/HA) composite.We studied the attachment of osteoblasts to two-dimensional films of these materials. We specifically looked at the potential of these two biodegradable systems to promote bone tissue growth. The materials were cast into two-dimensional films. They were evaluated for functionality, growth and adhesion at designated intervals using microscopy and bone-specific alkaline phosphatase (BAP) and osteocalcin (OC) immunoassays.The cells on the composite scaffold produced more BAP than the cells alone or on the PCL scaffold. However, the cells on both types of scaffolds showed lower levels of OC than the cells alone.
Thermal instability and hydrolysis have been the major factors and driving force behind the continued efforts by researchers to improve the properties of recycled poly(ethylene terephthalate) (RPET) in order for them to be considered useful. This study aims at enhancing the resistance of RPET moldings to hygrothermal aging without making any chemical modifications to the resin. The only means of modification that is done here is through alterations in terms of processing conditions and techniques. The sandwich injection molding technique is capable of producing specimens with a distinctive skin and core structure. Water absorption rate of the sandwich moldings was found to be much lower compared to conventionally molded specimens. Tensile and bending properties have also shown significant improvement favoring the sandwich specimens. The change in morphology due to ‘double-resin-flow’ in sandwich injection moldings could have created a layer between the skin and core that has excellent barrier properties that prevents water absorption into the inner parts of the specimens.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
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