Abstract
The aim of this study is to analyze the various compositions of polyvinyl alcohol (PVA) and starch blends. The blends have been cross-linked with glyoxal to enhance its properties. The hydroxyl groups of PVA and starch react with glyoxal via formation of acetal bonds; hence crosslinking could take place. The cross-linking of glyoxal is observed in various analytical methods such as DSC and FTIR. The cross-linked blends showed better thermal and mechanical properties. Viscosity, tensile shear strength, pencil hardness and ultimate stress were evaluated to estimate the changes due to cross-linking. It was observed that the cross-linking is directly proportional to starch, since the starch hydroxyl groups are easily accessible for reacting. The cross-linked blend showed better cohesion between its chains, thereby increasing glass transition temperature. It was reflected in the subsequent increase in tensile strength properties.
Highlights
Starch is a relatively inexpensive and renewable product that can be obtained from multiple plant sources and that has been extensively used as wet end additive, coating binder, sizing agent, adhesive, and textile size [1] [2]
Recent studies have focused on formaldehyde-free wood adhesives, which are obtained through the reaction between a cross-linker and a blend of starch with other polymers, such as starch/polyvinyl alcohol [8], starch/tannin [9] [10]
The glyoxal acts as a cross-linker for polyvinyl alcohol (PVA)/S, which has led to subsequent viscosity
Summary
Starch is a relatively inexpensive and renewable product that can be obtained from multiple plant sources and that has been extensively used as wet end additive, coating binder, sizing agent, adhesive, and textile size [1] [2]. A few studies have been conducted on the potential of utilizing starch as wood adhesive. Recent studies have focused on formaldehyde-free wood adhesives, which are obtained through the reaction between a cross-linker and a blend of starch with other polymers, such as starch/polyvinyl alcohol [8], starch/tannin [9] [10]. [11] and starch/isocyanates [12]. Such wood adhesives cannot be used at room temperature because the required curing temperature is usually over 100 ̊C [13]. Many efforts have been exerted to develop starch-based polymers as alternatives of petroleum-based polymers [14] [15] [16]
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