Suresh Subramonian

Anion-exchange resins from vinylbenzyl choride: control of hydrolysis during polymerization

Abstract Anion-exchange resins can be prepared by amination of vinylbenzyl chloride-divinylbenzene (VBC-DVB) copolymers. A limitation of the VBC route is that significant hydrolysis of benzyl chloride to benzyl alcohol occurs during copolymerization, which can reduce the ion-exchange capacity of the final resin. This article documents a novel technique to control hydrolysis with a staged polymerization process using a package of azo and peroxy initiators. The polymerization is initiated at low temperature to minimize hydrolysis, run to high conversion at moderate temperature and completed at high temperature to burn off residual monomer. The aqueous phase is buffered with bicarbonate salt to prevent low pH conditions. The technique effectively controls hydrolysis to less than 5%, producing a high capacity anion-exchange resin. The technique can be used to synthesize VBC-DVB resins that are equivalent to conventional styrene-DVB resins by incorporating additional crosslinking agent during polymerization to compensate for the lack of methylene bridging during functionalization

Acoustics and forming of novel polyolefin blend foams

Novel acoustical materials have been developed for sound absorption and insulation. The materials are macrocellular thermoplastic foams made from blends of polyethylene and polypropylene. The closed cell foams exhibit good acoustic performance over a broad frequency range and are especially effective at low frequencies. The foams are able to withstand high service temperature environments in industrial applications. Other advantages, relative to conventional acoustic media, include resilience, structural integrity, ease of fabrication, moisture resistance and recyclability. Techniques to improve the acoustical performance by profiling the foam with Helmholtz resonators and quarter wave attenuators are discussed. Forming is the shaping of thermoplastic foams by the application of heat and pressure. This process is used to make acoustic parts with the desired shape and size for space constrained applications such as appliance and automotive. This process can also be used to modify the skin quality and surface aesthetics of the foam. Studies were conducted in laboratory scale equipment to determine the process conditions for forming polyolefin foam and to evaluate the effect on cell structure, foam properties and acoustics. Techniques to preserve the acoustical performance of the foam during the forming process are reviewed.

Novel soft touch, low abrasion, fine cell polyolefin foams

Recent technical breakthroughs have enabled the development of soft touch, fine cell, noncrosslinked polyolefin foams. By optimizing the foam formulation and processing/forming conditions, the foam properties and performance attributes have been tailored to match that of crosslinked polyolefin foams in automotive material handling applications. Environmental pressures have created an unmet market need for a 100% recyclable, low-cost replacement product. This article details the physical properties, cushioning characteristics, abrasion performance, and thermoformability of the tough, resilient foams. The durable foams absorb shock, dampen vibration, and protect fragile products with high-quality surfaces from abrasion during handling, storage, and transportation. The foams thermoform over a relatively broad temperature range at low-to-moderate draws to produce well-defined fabricated products that closely match the mold contours while preserving cellular structure. The unique attributes of the noncrosslinked foams facilitate their penetration into several market segments currently dominated by crosslinked foams.

Properties and applications of novel acoustical foams

This paper describes the unique properties of a new line of novel acoustical materials that has been developed for sound and vibration management. The materials are macrocellular thermoplastic foams made from polyolefin resin blends. Fire retardant grades have been developed to meet a variety of building and construction fire codes. The foams have several advantages over incumbent materials, including structural integrity, moisture resistance, ease of fabrication/installation and recyclability. This paper also reviews a case study involving the use of the new foams to significantly dampen the sound level of a noisy industrial facility. The sound pressure levels and reverberation decay times were measured in the target area with an integrating, real time 1/3‐oct spectrum analyzer. Architectural acoustical analysis was performed using ray diagrams and Sabine calculations for determining the amount and optimal placement of the absorptive media to reduce the reverberant noise fields and sound reinforcing refl...