Small deformation viscoelastic and thermal behaviours of pomegranate seed pips CMC gels

Abstract

The current investigation presents an exploration in phase behaviour of carboxymethyl cellulose (CMC) produced from pomegranate seed pips compared to low and high viscosity CMCs (LMCMC and HMCMC) primarily at low solid concentrations. Cellulose was extracted with 10 % NaOH at 35°C for 22 h from pomegranate seed pips and converted to CMC by etherification process. Thermomechanical analysis and micro-imaging were carried out using small deformation dynamic oscillation in shear, modulated differential scanning calorimetry (MDSC) and scanning electron microscopy (SEM). The results emphasize the importance of molecular interaction and the degree of substitution in produced CMC. Thermal gravimetric analysis (TGA) thermograms showed an initial weight loss in pomegranate seed pips CMC (PSCMC) sample, which we attribute to presence of amount of moisture in sample powder. MDSC analysis of PSCMC showed five different peaks at 84, 104, 173, 307 and 361°C. Moreover, G' and G" changes were found to be dependent on both concentration and frequency. The results of frequency sweep and tan δ indicate that PSCMC solutions can be classified as weak gels.

Electrostatic and Hydrophobic Interactions in NaCMC Aqueous Solutions: Effect of Degree of Substitution

“…Concentrated solutions of heterogeneous samples are reportedly thixotropic − and can form gels. − ,− Fuller and co-workers inferred from rheo-optical measurements that for DS ≤ 1 semidilute and concentrated NaCMC solutions are highly aggregated.…”

Characterization of Sodium Carboxymethyl Cellulose Aqueous Solutions to Support Complex Product Formulation: A Rheology and Light Scattering Study

“…12 Despite its broad use in industry, Na CMC behavior in solution is still relatively poorly understood and is the subject of research from both fundamental 1,[13][14][15][16] and applied perspectives. 10,[17][18][19][20] The polyelectrolyte nature of Na CMC is, in itself, a reason for this poor understanding since many questions remain about the behavior of charged polymers in solution, 16,21 and especially in saltfree solutions; one example concerns the origin of the 'slow' relaxation mode typically observed using Light Scattering (LS), whose presence is not predicted by standard theory. [22][23][24] Given the biological origin of Na CMC, it typically has a high polydispersity of the chain length distribution 1,5,25,26 (common values of Mw/Mn are around 1.7-4.5 1,5,13,25,26 ).…”

“…The crystallinity of the cellulose raw material, 3,25,27 and/or the amount and the distribution of the carboxymethyl groups along the chains. 3,19,[28][29][30] can also vary. Commercial Na CMCs typically have an average of 0.4-1.5 carboxymethyl groups per monomer, which is referred to as the absolute Degree of Substitution (DS).…”

“…For example, in the case of toothpaste, Na CMC is responsible for toothpaste performance, including toothpaste stability in its container, dispensing, in-mouth behavior, and rinsing of the sink after use . Despite its broad use in industry, Na CMC behavior in solution is still relatively poorly understood and is the subject of research from both fundamental ,− and applied perspectives. ,− The polyelectrolyte nature of Na CMC is, in itself, a reason for this poor understanding since many questions remain about the behavior of charged polymers in solution , and especially in salt-free solutions; one example concerns the origin of the “slow” relaxation mode typically observed using light scattering (LS), whose presence is not predicted by standard theory. − …”

“…Given the biological origin of Na CMC, it typically has a high polydispersity of the chain length distribution ,,, (common values of M w / M n are around 1.7–4.5 ,,,, ). The crystallinity of the cellulose raw material ,, and/or the amount and the distribution of the carboxymethyl groups along the chains ,,− can also vary. Commercial Na CMCs typically have an average of 0.4–1.5 carboxymethyl groups per monomer, which is referred to as the absolute degree of substitution (DS). , These charged carboxymethyl groups are key to the behavior of Na CMC in solution as they confer its water-solubility to Na CMC.…”