Molecular weight effects on solution rheology of pullulan and mechanical properties of its films

Lazaridou, Athina; Βiliaderis, Costas G.; Kontogiorgos, Vassilis

doi:10.1016/s0144-8617(02)00302-8

Cited by 128 publications

(85 citation statements)

References 69 publications

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“…Good agreement is obtained between the two cellulose samples despite the widely different molecular weights. This was expected, as the glass transition temperature should be independent of polymer size in this range (DP [ 200), as has been found in starch like polymers (Lazaridou et al 2003;Orford et al 1989).…”

Section: Thermal Transitionssupporting

confidence: 53%

The glass transition and crystallization of ball milled cellulose

et al. 2010

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Samples of ball milled cellulose were prepared by ball milling pulps from eucalyptus and softwood (spruce/pine). Water sorption isotherms were obtained by both dynamic vapor sorption and equilibration over saturated salt solutions, in the water content range of 5-42% db (db = dry basis; water as a % age of total solids). Dynamic mechanical analysis using a pocket technique showed a water content dependent thermal transition occurring at the same temperature for the two pulp samples, which was interpreted as a glass transition. Fitting the data to a Couchman-Karasz relationship predicted a value for T g of the dry cellulose of approximately 478 K, which was similar to values previously reported for other dry polysaccharides. No clear glass transition could be observed calorimetrically, although an endotherm at approximately 333 K was measured, which in polymers is normally attributed to enthalpic relaxation, however the lack of dependence of this endotherm on water content suggests that the melting of some weak associations, such as residual hydrogen bonds, could be a more credible explanation. An exotherm was also observed on heating, which was dependent on water content and which was attributed to partial crystallization of the cellulose. This was confirmed by Wide angle X-ray diffraction and cross polarization magic angle spinning 13C NMR (CPMAS NMR). The recrystallisation was predominantly to form I of cellulose. This was thought to be caused by a small amount of residual form I (probably less than 5%) acting as a template for the crystallizing material. Differential scanning calorimetry reheat curves showed the appearance of freezable water for water contents higher than 20%, as a result of a transfer of water to the amorphous phase following crystallization. The increase in cellulose rigidity following crystallization was also confirmed by CPMAS NMR relaxation. Low resolution proton NMR T 2 relaxation suggested the presence of proton water/cellulose exchange, which was active at water contents of 20% and above

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Section: Thermal Transitionssupporting

confidence: 53%

The glass transition and crystallization of ball milled cellulose

et al. 2010

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“…Mechanical adhesion: adhesion occurs by the penetration of adhesive in irregular surface, pores or micro-cavities [15]. Adsorption adhesion: adhesion occurs due to inter-atomic or inter-molecular forces between adhesive and adherend molecules, based on associated energy (in kJ/mol) covalent (150-950), ionic (400-800), H-bond (40) and van der Walls (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) forces are respectably considered to be strong in above order [16]. Electrostatic adhesion: adhesion occurs due to electrostatic forces at interface having difference in electrical charges, this adhesion is applicable between non-compatible materials such as polymeric and metallic substances [16].…”

Section: Background Information Of Adhesionmentioning

confidence: 99%

“…gums, polysaccharides, oligomers and monomers. For carrying adhesive properties, the fundamental structural feature of polysaccharides mainly comprises of high molecular weights and polar-functional groups [2,3]. Polymer based adhesives must have many physical, chemical and mechanical properties to promote adhesion.…”

Section: Introductionmentioning

confidence: 99%

Chitosan: Emergence as potent candidate for green adhesive market

Patel

2015

Biochemical Engineering Journal

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“…Mechanical strength of edible chitosan films was also significantly decreased indicated by the decreasing tensile strength along with the increase of glycerol concentration (25-125%) (Thakhiew et al, 2010). This also happened in pullulan films with water as plasticizer (Lazaridou, Biliaderis, & Kontogiorgos, 2003). The loss modulus of the flaxseed gum films were not significantly affected by the glycerol concentration.…”

Section: Dynamic Mechanical Properties Affected By Glycerol Concentramentioning

confidence: 91%