We have connected viscoelastic recovery (healing) in sliding wear to free volume in polymers by using pressure-volume-temperature (P-V-T) results and the Hartmann equation of state. A linear relationship was found for all polymers studied with a wide variety of chemical structures, except for polystyrene (PS). Examination of the effect of the indenter force level applied in sliding wear on the healing shows that recovery is practically independent of that level. Strain hardening in sliding wear was observed for all materials except PS, the exception attributed to brittleness. Therefore, we have formulated a quantitative definition of brittleness in terms of elongation at break and storage modulus. Further, we provide a formula relating the brittleness to sliding wear recovery; the formula is obeyed with high accuracy by all materials including PS. High recovery values correspond to low brittleness, and vice versa. Our definition of brittleness can be used as a design criterion for choosing polymers for specific applications.

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Four different composite mixtures with varying amounts of expanded vermiculite were exposed to high temperatures of 300, 600, 900 and 1100uC for 6 h. Physical and mechanical properties including unit weight, porosity, water absorption, residual compressive strength, residual splitting tensile strength and also ultrasonic pulse velocity were determined after air cooling. Microstructures were investigated by scanning electron microscopy. Lightweight concrete with vermiculite shows a good performance at elevated temperatures. Expanded vermiculite is a significant lightweight aggregate for cementitious materials which are used for fire resistance applications. Concrete with vermiculite can be used as cement based refractory.

We have subjected polycarbonate (PC), low density polyethylene (LDPE), polystyrene (PS), polypropylene (PP), and Hytrel® (HY, a thermoplastic elastomer) to atmospheric pressure oxygen plasma treatment for varying amounts of time. Effects of the treatment have been evaluated in terms of the water wetting angle, dynamic friction, scratch resistance, and sliding wear. Although PS, PP, and HY do not undergo significant tribological changes as a result of the interaction with plasma, PC and LDPE show more pronounced and useful effects, such as a lowering of dynamic friction in PC and wear reduction in LDPE. These results can be explained in terms of the changes in chemical structures and increase of hydrophilicity. Based on the effects of oxygen plasma treatment on PC and LDPE, these two polymers have been subjected to longer oxygen plasma treatments and to argon, nitrogen, and air plasmas. Resulting effects on friction and scratch resistance are compared to determine the mechanisms responsible for the various surface behaviors. Chemical surface modification—as represented by changing contact angles—contributes to the tribological responses. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Drag reduction (DR) agents are used in several ppm concentrations to accelerate significantly the flow through conduits in oil pipelines, oil well operations, flood water disposal, fire fighting, field irrigation, transport of suspensions and slurries, sewage systems, water heating and cooling systems, airplane tank filling, marine systems, and also in biomedical systems including blood flow. The drag reduction agents are typically high molecular mass polymers; in industrial applications they undergo mechanical degradation in turbulent flow. We provide an equation that describes quantitatively the degradation, thus predicting drag reduction as a function of time and of the concentration of the drag reduction agent. We report how grafting a polymer on the backbone of a different polymer affects the drag reduction efficacy. Our grafted polymer undergoes degradation by flow turbulence more slowly and also provides high levels of drag reduction efficacy at much lower concentrations than homopolymers do.

Oil sorbents-namely materials that can be used to extract oil after a spill-were fabricated from nonwoven polyethylene terephthalate (NWPET) fibers modified by the adherence of crosslinked polymer coatings to the fiber surface. The NWPET fibers, which serve as a structural support for the applied functional coatings, were produced from recycled PET (polyethylene terephthalate) bottles. The oil absorbing coatings were comprised of crosslinked homopolymers and copolymers based on octadecyl acrylate (ODA), maleic anhydride (MA), and related esters of MA. The crosslinked polymer networks were synthesized by both suspension and bulk polymerization techniques using divinylbenzene (DVB) as the crosslinking agent. Efficacy of the coated NWPET fibers as oil sorbers was determined by oil absorption tests in toluene and in 10% crude oil in toluene. Rigidity, porosity and swelling of the crosslinked polymers were evaluated and correlated to the chemical structures, composition, and reaction media. Suspension polymerization yielded the desired morphology and function, providing higher porosity and in consequence a high absorption capacity.