Antiwear Film Formation by ZnDTP,Detergent, and Dispersant Components of Passenger Car Motor Oils—Part II: Effects of Low-Molecular-Weight Dispersant on Film Formation

Passenger car motor oils (PCMOs) are undergoing a rapid evolution. Studies have found that some exhaust emission catalysts may be deactivated by phosphorus, largely derived from zinc dialkyldithiophosphate (ZnDTP), the mainstay antiwear and antioxidant agent in PCMO formulations for the past 50 years. Consequently, future engine oils will contain significantly reduced phosphorus levels. Since ZnDTP is the dominant antiwear and antioxidant in current PCMOs, lower phosphorus content will impact engine oil formulation strategies.

To better understand the effects of ZnDTP reduction on wear control, electrical contact resistance (ECR) studies have been carried out on blends containing ZnDTP, detergent, and low-molecular-weight (LMW) succinimide dispersant. In contrast to previous results obtained with high-molecular-weight (HMW) dispersant, the combination of ZnDTP and LMW dispersant gave an ECR trace closely resembling that of ZnDTP alone. Thus, the chemical structure of the succinimide dispersant can have a profound effect on ZnDTP antiwear film formation. ECR experiments on three-way combinations of ZnDTP + LMW succinimide dispersant + overbased phenate detergent provided a much better film than that from a similar formulation using an HMW succinimide dispersant. This study demonstrates that the ECR experiment is sensitive to the chemical structures of components controlling the function of modern PCMOs, making ECR a convenient tool to optimize the performance of the remaining ZnDTP in lower phosphorus PCMO formulations.     

Isolation and Structure Investigations of Square Banana (Musa balbisiana) Starch

Starch was isolated from unripe square banana (Musa balbisiana) fruit and characterized physically and chemically. Isolation was done with a 2³ factorial design using five replicates in the central trial. Evaluated factors were: flour: solvent ratio (1:6 ‐ 1:10, w/v); sodium bisulfite concentration (0.1 ‐ 0.3%); and soaking time (30 ‐ 60 min). Optimum starch isolation in an alkaline medium was obtained with: 1:5 (w/v) flour: solvent ratio; 0.1% sodium bisulfite concentration; and 60 min soaking time. Starch yield under these conditions was 69.8% with 94.5% purity. Starch granules had an oval‐elongate shape, a size range of 24‐68 μm, and average size of 24.6 μm. Amylose content was 22.2% and amylopectin content 77.8%. Granules had a C‐type ‐ray diffraction pattern and a degree of polymerization (DP) of 3‐20 for lengths of branch chains.     

Counselor helping model, participant ethnicity and acculturation level, and perceived counselor credibility.

An analogue research design was used to examine the relationships between participant ethnicity, acculturation level, counselor model of helping, and ratings of counselor credibility. A total of 199 community college students (109 Mexican Americans, 90 European Americans) evaluated counselor credibility after being exposed to 1 of 4 counseling vignettes. Evidence was found to support the hypothesis that ethnic background and adherence to cultural norms and behaviors are related to perceptions of counselor expertise and trustworthiness. Results also showed that loss of Mexican culture, rather than the acquisition of North American culture, is associated with less positive perceptions of counselor credibility. Contrary to the cultural barrier theory used to explain underutilization of mental health services among Mexican Americans, these results suggest that aspects of the Mexican culture support the use of counseling services among Mexican Americans. Implications for counselors and suggestions for future research are explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)