Jo Ann Ratto

Processing, performance and biodegradability of a thermoplastic aliphatic polyester/starch system

Abstract Composites of a biodegradable thermoplastic aliphatic polyester, polybutylene succinate adipate (PBSA), with granular corn starch were investigated for processability, mechanical and thermal properties, and biodegradability. The PBSA/starch films were prepared with starch contents of 5%–30% by weight and processed by blown film extrusion. Increasing the starch content led to an increase in modulus and decreases in tensile strength, elongation to break and toughness. The rate of biodegradation in soil, as measured by respirometry, increased significantly as the starch content was increased to 20% and then plateaued. Scanning electron microscopy revealed that the starch granules were embedded in the continuous-phase PBSA and that starch promotes the biodegradation of PBSA. Gel permeation chromatography indicated a molecular weight decrease for the PBSA after soil exposure and confirmed that biodegradation was enhanced by the presence of starch. The results demonstrated that the biodegradable PBSA/starch system has mechanical properties useful for blown film applications.

Phase behavior study of chitosan/polyamide blends

Blends of chitosan with strongly crystalline polyamides (nylon-4 and nylon-6) and weakly crystalline polyamides (caprolactam/laurolactam and Zytel®) were investigated. Phase behavior, morphology, interactions with water, mechanical properties, and catalytic reactivity were studied. Films were made from formic acid solutions with the chitosan concentrations ranging from 5% to 95% (w/w). The 80% deacetylated chitosan is in the salt, neutral, or copper chelate form. All the blends have higher relative water contents than does the pure chitosan. Dry neutral chitosan shows a relaxation centered at approximately 90°C which is attributed to local motion. The phase behavior of the blends is influenced by preparation conditions such as the drying temperature. Characterization of blends by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) suggests partial miscibility of chitosan with nylon-4 and lack of miscibility in the remaining cases. Blending with nylon-4 enhances mechanical properties with marked antiplasticization in blends containing 90% chitosan. Catalytic activity of the chitosan is enhanced by blending with nylon-4. Salt and neutral forms of chitosan appear to be equally effective.

A Study of Barrier Properties of LDPE Nanocomposite Films Under Extreme Environmental Conditions

Pure and nanoclay montmorillonite layered silicates, MLS) embedded within low density polyethylene (LDPE) composite films were tested under extreme environmental conditions (i.e. conditioned air of varying temperature-relative humidity combinations: 10oC and 90% RH, 40oC and 20% RH, and 40oC and 90% RH) to determine the effects of nanoclay expansion on water vapor barrier properties. Results from Differential Scanning Calorimetery (DSC) and Thermogravimetric Analysis (TGA) confirmed that the presence of nanoparticles (MLS) within LDPE films increased the thermal quality and stability of the films. A 19 day moisture stability study using nine salt solutions that range between 11.3% to 93.6% relative humidity indicated that the presence of nanoclay particles (MLS) and relative humidity did not negatively impact the hygroscopic (water vapor) barrier properties of the films.

Ras Labs-CASIS-ISS NL experiment for synthetic muscle returned to Earth: resistance to ionizing radiation

In anticipation of deep space travel, new materials are being explored to assist and relieve humans in dangerous environments, such as high radiation, extreme temperature, and extreme pressure. Ras Labs Synthetic Muscle™ – electroactive polymers (EAPs) that contract and expand at low voltages – which mimic the unique gentle-yet-strong nature of human tissue, is a potential asset to manned space travel through protective gear and human assist robotics and for unmanned space exploration through deep space. Gen 3 Synthetic Muscle™ was proven to be resistant to extreme temperatures, and there were indications that these materials would also be radiation resistant. The purpose of the Ras Labs-CASIS-ISS Experiment was to test the radiation resistivity of the third and fourth generation of these EAPs, as well as to make them even more radiation resistant. On Earth, exposure of the Generation 3 and Generation 4 EAPs to a Cs-137 radiation source for 47.8 hours with a total dose of 305.931 kRad of gamma radiation was performed at the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) at Princeton University, followed by pH, peroxide, Shore Hardness durometer, and electroactivity testing to determine the inherent radiation resistivity of these contractile EAPs, and to determine whether the EAPs could be made even more radiation resistant through the application of appropriate additives and coatings. The on Earth preliminary tests determined that selected Ras Labs EAPs were not only inherently radiation resistant, but with the appropriate coatings and additives, could be made even more radiation resistant. G-force testing to over 10 G’s was performed at US Army’s ARDEC Labs, with excellent results, in preparation for space flight to the International Space Station National Laboratory (ISS-NL). Selected samples of Generation 3 and Generation 4 Synthetic Muscle™, with various additives and coatings, were launched to the ISS-NL on April 14, 2015 on the SpaceX CRS-6 payload, and after 1+ year space exposure, returned to Earth on May 11, 2016 on SpaceX CRS-8. The results were very good, with the survival of all flown samples, which compared very well with the ground control samples. The most significant change observed was color change (yellowing) in some of the flown EAP samples, which in polymers can be indicative of accelerated aging. While the Synthetic Muscle Experiment was in orbit on the ISS-NL, photo events occur every 4 to 6 weeks to observe any changes, such as color, in the samples. Both the 32 flown EAP samples and 32 ground control samples were tested for pH, material integrity, durometer, and electroactivity, with very good results. The samples were also analyzed using stereo microscopy, scanning electron microscopy (SEM)), and energy dispersive X-ray spectroscopy (EDS). Smart electroactive polymer based materials and actuators promise to transform prostheses and robots, allowing for the treatment, reduction, and prevention of debilitating injury and fatalities, and to further our exploration by land, sea, air, and space.

Ras Labs.-CASIS-ISS NL experiment for synthetic muscle: resistance to ionizing radiation

In anticipation of deep space travel, new materials are being explored to assist and relieve humans in dangerous environments, such as high radiation, extreme temperature, and extreme pressure. Ras Labs Synthetic Muscle – electroactive polymers (EAPs) that contract and expand at low voltages – which mimic the unique gentle-yet-strong nature of human tissue, is a potential asset to manned space travel through protective gear and human assist robotics and for unmanned space exploration through deep space. Generation 3 Synthetic Muscle was proven to be resistant to extreme temperatures, and there were indications that these materials may also be radiation resistant. The purpose of the Ras Labs-CASIS-ISS Experiment is to test the radiation resistivity of the third and fourth generation of these EAPs, as well as to make them even more radiation resistant or radiation hardened. On Earth, exposure of the Generation 3 and Generation 4 EAPs to a Cs-137 radiation source for 47.8 hours with a total dose of 305.931 kRad of gamma radiation was performed at the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) at Princeton University, followed by pH, peroxide, Shore Hardness Durometry, and electroactivity testing to determine the inherent radiation resistivity of these contractile EAPs and to determine whether the EAPs could be made even more radiation resistant through the application of appropriate additives and coatings. The on Earth preliminary tests determined that selected Ras Labs EAPs were not only inherently radiation resistant, but with the appropriate coatings and additives, could be made even more radiation resistant. Gforce testing to over 10 G’s was performed at US Army’s ARDEC Labs, with excellent results, in preparation for space flight to the International Space Station National Laboratory (ISS-NL). Selected samples of Generation 3 and Generation 4 Synthetic Muscle™, with various additives and coatings, were launched to the ISS-NL on April, 14 2015 on the SpaceX-6 payload, and will return to Earth in 2016. The most significant change from the on Earth radiation exposure was color change in the irradiated EAP samples, which in polymers can be indicative of accelerated aging. There was visible yellowing in the irradiated samples compared to the control samples, which were not irradiated and were clear and colorless. While the Synthetic Muscle Experiment is in orbit on the ISS-NL, photo events occur every 4 to 6 weeks to observe any changes, such as color, in the samples. The bulk of the testing will occur when these EAP samples return back to Earth, and will be compared to the duplicate experiment that remains on Earth (the control experiment). Smart electroactive polymer based materials and actuators promise to transform prostheses and robots, allowing for the treatment, reduction, and prevention of debilitating injury and fatalities, and to further our exploration by land, sea, air, and space.