SPE Library

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. [1] 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.[2] 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.

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.

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.

This work investigated the addition of Polycaprolactone (PCl) and Sodium Tripolyphosphate (TPP) to the biodegradable polymer chitosan, via the preparation method of dry blending, followed by compression. The improvement in mechanical properties and suitability for biomedical applications were determined through the changes in surface characteristics, crystallinity and mechanical properties. It was found that the differences in melting temperature, contact angle and phase transition temperatures (tan ?) were highly dependent on the ratio of PCl and chitosan in each blend.

Research objective is to establish manufacturing-related design rules and procedures for engineering design of injection molded thermoplastics parts, and to investigate application of novel materials to support development of design for sustainability. Outputs of numerical injection molding simulations have been compared with tensile and tensile-impact test results for different geometry-material combinations. Combination with simulation results on thick-walled parts reported earlier has led to a systematic with predictive capability of simulation outputs for differences in mechanical performance.

Biodegradable copolyesters are processed primarily through extrusion and injection moulding. This paper presents preliminary investigations into the grinding and rotational moulding characteristics of commercially available biodegradable copolyester. Cryogenic grinding and subsequent rotational moulding experiments on the copolyester resin resulted in complete mouldings of uniform wall thickness being produced. It was observed that peak internal mould air temperatures of approximately 150 degC are required in order to produce acceptable mouldings.

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.

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.

The corn gluten meal (CGM) is one of the major byproducts of ethanol industries. The current use of CGM is more towards livestock feed. This research looks forward in using CGM in making novel biodegradable plastics by blending with one petroleum-derived biodegradable polymer like poly (?-caprolactone), PCL. The CGM was plasticized with glycerol and destructurized with guanidine hydrochloride (GHCl) followed by blending with PCL. Extrusion followed by injection molding processing was adopted in fabricating the new blended green materials. The processing conditions affected the performance of the blends. The resulting green materials were studied for their mechanical properties using dynamic mechanical analyzer (DMA), united testing system (UTS) and izod impact tester.

The trend toward increased usage of renewable resources has led to the growing popularity of wood-filled materials. These emerging materials require extensive testing – beginning with formulation and ending with the final manufactured product. In the early stages of development, it is possible to acquire data comparing differences between recipes utilizing a Mixer/Measuring Head. The given blend can be compounded with a customized twin screw extruder and torque rheometer. Finally, a single screw extruder can quantify the rheology of the compound using a capillary die. The objective of this work is to investigate the behavior of a polyolefin based wood-filled compound using a torque rheometer.