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Abstract

Efforts are focused on the effects of operating parameters, i.e., die shapes (DS), PVA ratio (PR), and additives (AT), on the physical and mechanical properties of corn-PVA extrudates in this study. The cellular structure of biodegradable extruded foams are studied and the extrudates are evaluated as cushioning materials. The process variables are the operating conditions, DS (O, ∞, Δ, and 0), PR (40, 50, 60%), and AT (8%) (sodium bicarbonate (NaHCO³), calcium carbonate (CaCO₃), calcium hydroxide (Ca(OH)₂)). The experimental setup is a 4 × 3 × 3 factorial design. Samples of each treatment are collected and the physical and mechanical properties are measured and analyzed using the PROC ANOVA and PROC CORR of the SAS 6.0 software package. Moreover, the cellular structures of the extrudates are observed by using a scanning electron microscope. The experimental results indicate that: (a) the change of DS has a significant effect on the longitudinal expansion, bulk density, and compressibility of the extrudates; (b) the change of PR has a significant effect on the longitudinal expansion, bulk density, and compressibility of the extrudates; (c) the change of AT has a significant effect on the longitudinal expansion, bulk density, and compressibility of the extrudates; (d) the most uniform cell is obtained with the O-shaped die, as compared with other die shapes. A moderate cell wall is obtained with the O-shaped die. The largest cell sizes are found in PVA 60% with CaCO₃. However, the smallest cell sizes are found in PVA 60% with NaHCO₃. Changing the types of additives from NaHCO₃ to CaCO₃, and CaCO₃ to Ca(OH)₂ increases the cell size and cell wall thickness.

Keywords

die shapes additives cellular structure biodegradable cushioning extruded foams

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Effects of Die Shapes and Additives on the Physical and Mechanical Properties,and Cellular Structure of Biodegradable Cushioning Extruded Foams

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