ABSTRACT
The widespread use of carpets in residential and commercial buildings and their relatively short life span result in large volumes of carpet being landfilled. A potential solution to this problem is the use of post-consumer carpet fibers in concrete. To this end, this paper systematically identifies the common fiber types in a typical post-consumer carpet fiber bale and evaluates their durability under exposure to varying levels of alkalinity. The tensile strengths and toughness of the fibers belonging to the nylon and polyethylene terephthalate (PET) families (the dominant fibers in most post-consumer carpets) are reduced by up to 50% following exposure to extreme alkalinity, the reasons for which are determined using spectroscopic and microscopic evaluations. The chloride ion transport resistance of concretes (~40 MPa strength) containing 2.5% carpet fibers by volume (~25 kg of fibers per cubic meter of concrete) is comparable to that of the control mixture, while mortar mixtures containing the same volume fraction of carpet fibers demonstrate negligible enhancement in expansion and loss of strength when exposed to 1 N NaOH. This study shows that moderate-strength concretes (~40 MPa) for conventional building and infrastructure applications can be proportioned using the chosen volume of carpet fibers without an appreciable loss of performance. Consideration of low volume fractions of carpet fibers in low-to-moderate-strength concretes thus provides a sustainable avenue for the use of these otherwise landfilled materials in construction applications.
ABSTRACT
All-trans-retinoic acid reverses malignant cell growth and induces cell differentiation and apoptosis. Poor aqueous solubility and uncertain bioavailability are the limiting factors for using all-trans-retinoic acid for tumor therapy. The objective of present study was to encapsulate the hydrophobic drug all-trans-retinoic acid in the polymer poly (lactide-coglycolide). The encapsulation was expected to improve the bioavailability and solubility of the drug. Oil in water single emulsion solvent evaporation technique used for the preparation efficiently encapsulated about 60% of the drug. The drug release profile showed a biphasic pattern with 70% of the drug being released in first 48 hrs and the residual drug showing a slow controlled release reaching up to 8 days. The particle size of 150-200 nm as determined with TEM was ideal for tumor targeting. All-trans-retinoic acid loaded nanoparticles were efficient to induce differentiation and blocked the proliferation of HL-60 cells invitro. These studies also revealed that the dosage of drug required for the therapeutic effects have been reduced efficiently. Our studies thereby demonstrate that Poly (lactide-co-glycolide) based nanoparticles may be efficient for parenteral administration of the drug.
