The Research On Environmental Air Hardening Watersoluble Polymer Binder And Hardening Mechanism

As the increasing requirements of environmental protection, to exploit a non-toxic, non-polluting, efficient foundry binder is becoming an urgent requirement. Polyvinyl alcohol(Polyvinyl Alcohol, PVA) is an organic macromolecular compound, which is water-souble, innoxious and harmless to environment. PVA is used for the main material, to develop an air hardening environmental foundry binder is signality.The primary coverage of the task is that polyvinyl alcohol is used for the main material, according to using the hardening accelerator, firming agent, cross-linking agent, coupling agent, carbon dioxide gas, and modifing to polyvinyl alcohol, the hardening process can be designed which uses polyvinyl alcohol binder. The process could meet the needs of rapid molding and core making, and it satisfies the requirement of foundry practice.First, accordding to the physical appearance of polyvinyl alcohol, choosing the proper solvent to prepare the solution of different concentrations. The polyvinyl alcohol sand would scleroses by using calcium hydroxide, cement and carbon dioxide gas. Accordding to lots of experiments to find out the optimum technology: m(PVA): m(Ca(OH)2): m(cement): m(B reagent): m(sand)=50: 30: 30: 3: 1000, the consistency of PVA solution is 18%.Second, to choose proper modifier and modification through the molecular structure and chemical property of polyvinyl alcohol. Accordding to the orthoqonal test, the best modification technics is gained. In PVA solution whose dosage is 100g and consistency is 18%, the dosage of formaldehyde is 6g, the dosage of catalyst is 0.4ml, the modification temperatrue is between 80℃and 85℃, the modification time is 120min, and the influence of modification on the PVA sand is certain. To choose the suitable cross-linking agent and coupling agent, the influence of them on the PVA sand is certain through experiments, and the optimal dosage is worked out: m(PVA): m(boric acid): m(silicane)=100: 0.6: 8.3. The adhesion mechanism is studied through SEM and infrared spectrum, the cause that the PVA sand′s compression strength is set up and increasing is also indicated.Finally, the performance of polyvinyl alcohol sand, such as pressive strength, service life, gas-formong property, collapsibility, is tested, and the production verification and economical efficiency are also tested. The results of experiments show that the polyvinyl alcohol sand has good processing property, it could meet the need of requirement of foundry practice, it could cut the cost and has obvious economic benefit, and it is also beneficial to be popularized and applied.