Effect of Reaction Conditions and Alkyl Chain Lengths on the Properties of Hydroxyalkyl Starch Ethers

Abstract

Starch applications in the plastics industry have been investigated intensively for many years. Unfortunately, native starch is unsuitable for most applications in polymers, because of its hydrophilic and brittle character. Modification of native starch can be a solution of this problem.In our research programme we developed an environmentally friendly process for the preparation of starch derivatives with long hydrophobic side chains based on natural products derived from vegetable fats and oils on the one hand and amylomaize starch on the other hand. In this process modification is carried out by the addition of longchain 1,2-epoxyalkanes (chain lengths varying between 6-18 C atoms) to starch in an alkaline aqueous medium. Reaction yields and molar degrees of substitution depended on chain length, reaction time, temperature and catalyst concentration. Under optimised reaction conditions molar degrees of substitution of hydroxyalkyl starch ethers for theoretical molar substitution (MS) = 3.0 decreased from MS=1.8 (C 6 starch ether) to MS=0.2 (C 18 starch ether), respectively. Hydrophobic properties of starch products were measured in order to reveal structural effects obtained at different reaction conditions. Water solubility and water absorption properties of hydroxyalkyl starch ethers decreased with increasing chain length and number of hydroxyalkyl substituents. Thermal and thermoplastic properties of starch ethers were investigated in order to determine their potential use as biodegradable polymers in the plastics industry. As expected, thermoplasticity of starch ethers increased with increasing MS and increasing chain length of the hydroxyalkyl side groups. Scheme 1. Reaction scheme for the preparation of hydroxyalkyl starch ether (MS = 1).

Preparation and Properties of Octenyl Succinic Anhydride Modified Early Indica Rice Starch

“…The pH of the aqueous slurry is important for esterification. As a catalyst, NaOH starts the reaction by the formation of alcoholate ions along the starch polymer [3,14].…”

Mass Transfer and Chemical Reaction Approach of the Kinetics of the Acetylation of Gadung Flour using Glacial Acetic Acid

“…Based on the starch acetate SEM analysis [10], it has been proven that the granula size of the acetylated starch is larger than the native one, thus, the fractional conversion of anhidroglucose in terms of weight of anhidroglucose is: (16) (17) Substitution Equation (17) to Equation (14), gives: (18) 3. Materials and Methods…”

“…The higher the pH, means the more NaOH was added. Sodium hydroxide in the acetylation reaction acts as a reaction initiator to form the alcoholate ions along the starch polymer which can activate the hydroxyl groups on the starch [16] and lead to a nucleophilic attack on acetic acid [17]. Sodium hydroxide also acts as a catalyst which can affect the swelling of the starch molecules, thereby increasing the ability of molecular diffusion around starch acetate [18].…”

Effect of reaction conditions on grafting ratio and properties of starch nanocrystals‐g‐polystyrene

“…For improving the hydrophobicity of starch nanocrystals and enhancing its compatibility with polymer matrix, a starch nanocrystals‐ g ‐polystyrene (StN‐ g ‐PS) by free radical polymerization in emulsion was synthesized in our laboratory as we reported previously . The graft copolymerization of native starch with varied monomers and the influence factors on reaction, such as initiator, monomer concentration, reaction temperature, and time have been studied . However, the graft polymerization of styrene onto a nanoscale starch has less been studied.…”

“…19 The graft copolymerization of native starch with varied monomers and the influence factors on reaction, such as initiator, monomer concentration, reaction temperature, and time have been studied. [20][21][22][23][24][25] However, the graft polymerization of styrene onto a nanoscale starch has less been studied. In this article, the effect of reaction conditions on grafting efficiency (GE), grafting ratio (GR), the grafting sites on starch backbone, as well as the properties of graft copolymers as a new nanosize filler are investigated.…”