Development Of Standard Test Methods Research Articles

The melt rheology of poly‐ε‐caprolactam/polypropylene alloy: A VAMAS round‐robin study

AbstractThe melt rheology of commercial poly‐ε‐caprolactam/polypropylene blend, Orgalloy R‐6000 was studied by a number of university, industrial, and government laboratories as part of the Versailles Project on Advanced Materials and Standards (VAMAS), Technical Working Party on polymer blends round‐robin research program. The objective of the organization is to facilitate the development of standard test methods for the characterization of such complex materials. The program was established to evaluate proposed test methods for characterization of the melt rheology of commercial blends. Orgalloy R‐6000 was studied in both shear and extensional flows. A number of the laboratories also compared its rheology to that of a polypropylene and a polyamide that are similar to those that were used to produce it. This material showed all the viscoelastic properties expected of molten thermoplastics but was found to be significantly more elastic than its constituent materials. The poor quantitative agreement of the interlaboratory results indicate that improvements in the standardization of test methodologies and sample conditioning for such hydroscopic materials is necessary.

Bioceramics: From Concept to Clinic

Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo‐skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass‐ceramics), or porous for tissue ingrowth (hydroxyapatite‐coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long‐term (20‐year) mechanical reliability under load is still needed.