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Mechanical Degradation (mechanical + degradation)
Selected AbstractsMechanochemical copolymerization of poly(vinyl chloride) with methyl methylacrylate in an open mill machineJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2006Peixin He Mechanical degradation of poly(vinyl chloride) (PVC) and mechanochemical copolymerization in poly(vinyl chloride)/methyl methylacrylate (PVC/MMA) systems were studied in an open mill machine. The effects of the mastication temperature, mastication time, and additives (oxygen, THF, or hydroquinone) on the mechanical degradation of PVC were investigated. The molecular weight of PVC decreased with increasing mastication time, and the efficiency of the mechanodegradation of PVC was lowered with increasing mastication temperature. The effects of the ratio of PVC to MMA, thin-passage time, and initiator on mechanochemical copolymerization also were studied. The experimental results indicated that the degree of copolymerization increased with increasing thin-passage times up to 45 times and then remained constant. There was a maximum degree of copolymerization at a ratio of 0.22 g/mL (PVC/MMA), and the efficiency of copolymerization always decreased with increasing time. The maximum degree and efficiency of copolymerization were 5.8 and 89%, respectively. The poly(vinyl chloride- co -methyl methylacrylate) copolymer can further improve the interfacial adhesion of PVC and PMMA. Thus it improves the mechanical properties of the PVC/CPE blend more effectively than pure PMMA. J. VINYL. ADDIT. TECHNOL. 12:42,48, 2006. © 2006 Society of Plastics Engineers. [source] A block-on-ring tribocorrosion setup for combined electrochemical and friction testingLUBRICATION SCIENCE, Issue 3 2007M.S. Jellesen Abstract The combined action of corrosion and wear can cause degradation of equipment, and thereby financial losses related to the renewal or repair of damaged equipment. In the food industry, metal degradation is a major concern since metal release eventually can cause health risks for consumers. This study describes a block-on-ring testing facility used to determine sliding wear, and additionally allowing for electrochemical measurements, such as potentiodynamic polarization curves and potentiostatic monitoring of current and potential. To verify the reliability and reproducibility of this block-on-ring tribocorrosion setup, the tribological and electrochemical behaviour of stainless steel sliding against a ceramic ring in sulphuric acid has been determined. Furthermore, a case taken from the food industry has been examined. The study shows that results made on the described block-on-ring testing facility are reliable and can provide improved information about material properties when the material is exposed to combined chemical and mechanical degradation. Copyright © 2007 John Wiley & Sons, Ltd. [source] The effect of recycling on LDPE foamability: Elongational rheologyPOLYMER ENGINEERING & SCIENCE, Issue 1 2008Eddy Twite Kabamba The purpose of this work was to investigate changes in the elongational rheology of low density polyethylene (LDPE) when recycled. Both foamed and unfoamed LDPE were submitted up to 10 generations in a closed loop using constant extrusion conditions and azodicarbonamide as a chemical blowing agent. For both foamed and unfoamed polymers, decreasing elongational properties in terms of strain hardening was observed, indicating progressive loss of foamability with the number of time the polymer is recycled. It was also found that the elongational properties of the foamed polymer decreased more rapidly than its unfoamed counterpart. It is believed that higher mechanical degradation of polymer may be the result of higher deformation rates (biaxial) associated with foaming and the accumulation of blowing agent residues limiting polymer chain mobility and entanglement. POLYM. ENG. SCI., 48:11,18, 2008. © 2007 Society of Plastics Engineers [source] Carboxyl terminated polyamide 12 chain extension by reactive extrusion using a dioxazoline coupling agent.POLYMER ENGINEERING & SCIENCE, Issue 12 2002Part II: Effects of extrusion conditions Condensation reactions between a carboxyl terminated polyamide 12 and a dioxazoline carried out by reactive extrusion have been characterized in the first part of this study. In the present paper, we focus on the influence of extrusion conditions on reaction progress. Influences of screw profile, screw speed, barrel temperature and feed rate have been established. The use of a flow computation software permitted confirmation of the importance of thermal and mechanical degradations in the condensation process. [source] | ||||||||||