Cold, semidilute, aqueous solutions of methylcellulose (MC) are known to undergo thermoreversible gelation when warmed. This study focuses on two MC materials with much different gelation performance (gel temperature and hot gel modulus) even though they have similar metrics of their coarse-grained chemical structure (degree-of-methylether substitution and molecular weight distribution). Small-angle neutron scattering (SANS) experiments were conducted to probe the structure of the aqueous MC materials at pre- and postgel temperatures. One material (MC1, higher gel temperature) exhibited a single almost temperature-insensitive gel characteristic length scale (ζ(c) = 1090 ± 50 Å) at postgelation temperatures. This length scale is thought to be the gel blob size between network junctions. It also coincides with the length scale between entanglement sites measured with rheology studies at pregel temperatures. The other material (MC2, lower gel temperature) exhibited two distinct length scales at all temperatures. The larger length scale decreased as temperature increased. Its value (ζ(c1) = 1046 ± 19 Å) at the lowest pregel temperature was indistinguishable from that measured for MC1, and reached a limiting value (ζ(c1) = 450 ± 19 Å) at high temperature. The smaller length scale (ζ(c2) = 120 to 240 Å) increased slightly as temperature increased, but remained on the order of the chain persistence length (130 Å) measured at pregel temperatures. The smaller blob size (ζ(c1)) of MC2 suggests a higher bond energy or a stiffer connectivity between network junctions. Moreover, the number density of these blobs, at the same reduced temperature with respect to the gel temperature, is orders of magnitude higher for the MC2 gels. Presumably, the smaller gel length scale and higher number density lead to higher hot gel modulus for the low gel temperature material.

The intrinsic nature of Research and Development (R&D) activitiesthe continuous use of new chemicals and development of cutting-edge, sustainable processes at a rapid pacecan increase the potential for Process Safety and Reactive Chemicals accidents. Industrial and academic laboratories have experienced several significant laboratory accidents and near misses. In an effort to decrease laboratory incidents, Dow, with a large global R&D presence, reviewed internal Root Cause Investigations which indicated that improvements were needed in chemical hazard recognition skills, chemical storage and handling, and inventory management. This paper presents a Dow initiative to address and combat such incidents through the charter of a multidisciplinary team composed of Reactive Chemicals, Process Safety, and Environment, Health, & Safety experts along with R&D researchers, who have collaborated to develop and deliver training modules which focus on high-interest safety topics. Module topics were chosen based on recurrence metrics and potential event severity. Modules provide laboratory personnel with basic topic knowledge, specific hazard awareness regarding the topic, and guidance on how to implement appropriate safeguards. The long-term objective is reducing the number and severity of incidents. Over two years, 10 modules have been delivered in various media; at least a quarter of global Dow R&D personnel have independently engaged with this training content, in addition to those directed to it by leaders, peers, safety experts, or training requirements. In addition to the development of enhanced training delivered via multiple platforms, the team has identified and recommended improvements or additions to existing safety management systems designed to identify hazards and control risk.