Sodium silicate and hydrolyzed collagen as a hybrid core binder for pollution prevention in foundries.

Open Access
Author:
Allen, Joshua F
Graduate Program:
Environmental Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 29, 2014
Committee Members:
  • Fred Scott Cannon, Thesis Advisor
  • Robert Carl Voigt, Thesis Advisor
  • Peggy Ann Johnson, Thesis Advisor
Keywords:
  • Metal casting
  • air emissions
  • stack test
  • core binder
  • foundry
  • pollution prevention
  • collagen
  • sodium silicate
Abstract:
Pollution management is an essential task in the manufacturing of cast metals. Conventional foundry production practices are currently being challenged by ever tightening environmental regulations. Herein, an emerging pollution prevention core binder is studied as a potential sustainable and cost efficient alternative to help meet volatile organic compound (VOC) air emission standards. Petrochemical sand core binders are favored for their thermal stress resistance during metal pouring and then for their ability to subsequently shake-out after metal solidification. However, when the molten metal is poured into the mold and around the petrochemical cores, the core binder decomposition releases VOCs that are then released into the surrounding environment. The goal of this research was to evaluate and advance the development of a sodium silicate and hydrolyzed collagen core binder to prevent VOC formation by petrochemical binder replacement. The first study discussed in this thesis is of a full-scale demonstration of 244 sodium silicate and hydrolyzed collagen bonded sand cores used in casting trials in a production foundry. The results showed that no core-related casting scrap rate was achieved and that core shake-out was satisfactory. These favorable results were achieved with proper storage of the cores before they were used. Following this trial, lab scale studies were performed to evaluate core binder performance. These studies revealed optimum binder levels to develop tensile strength returns at ambient temperatures. Conventional sodium silicate catalysts were not a viable means of core box curing and the hybrid sodium silicate and hydrolyzed collagen binder system was hydroscopic. This information, along with many core making efficiency improvements, was used to carry out a large scale casting demonstration with 3,476 cores. During the use of these cores at a full-scale foundry, pouring, cooling, and shake-out VOC emissions were 31% higher when conventional phenolic urethane cores were used than when these novel trial cores were used. In conclusion, this thesis supports sodium silicate and hydrolyzed collagen as a niche VOC-reducing alternative to petrochemical binders with the caveat that future work is needed to enhance core-related casting surfaces and storage humidity resistance of cores.