Research Article
SN Applied Sciences (2020) 2:1577 | https://doi.org/10.1007/s42452-020-03313-w
expressed in g. In TOC analyzer, liquid supernatant contain- ing residual chitosan was introduced into the combustion tube which was filled with an oxidation catalyst, generally platinum catalyst and heated to 680 °C. The sample was burnt in the combustion tube and as a result the TC (total carbon) components of the sample were converted into carbon dioxide which was then detected by NDIR (non- dispersive infrared) gas analyzer. Similarly, inorganic car- bon IC was determined by acidifying the sample to evolve carbon-di-oxide. In both the cases, calibration curves are generated with IC and TC standard solutions to evaluate TOC (TC–IC) of the samples. The obtained filler pellets were then dried at 30 °C for their subsequent characterization
phase transformation is indeed a result of molecular reor- ganization between polymer and mineral [21, 22]. Many researchers have already evaluated chitosan as a filler modifier for papermaking application but the influ- ence of chitosan on structural changes in PCC during the modification process and their effect on paper properties was given less importance in the reported literature. In the present work, a simple route of integrating chitosan with mineral filler PCC was established for developing chitosan/ PCC composite filler. Detailed characterization of crystal growth and morphology of PCC in the presence of this polymer were stressed so as to evaluate the performance of the corresponding composite as strength and filler retention additive in cellulose integrated paper material.
2.3 Characterization of fillers
The chemical group analysis was done by FTIR (Fou- rier transform infrared spectrophotometry) through the Perkin Elmer spectrophotometer in a transmission mode conducting 16 scans at a resolution of 4 cm −1 to acquire absorption spectra between 4000 and 500 cm −1 . Samples were diluted with KBr (potassium bromide) to form pressed pellets. Further phase transformation phe- nomenon was studied by examining the crystal struc- ture through WAXD [RIGAKU ULTIMA IV Wide-angle X-ray diffractometer at a scan rate of 4°/min over a range of 2 θ = 5°–80°. The operating voltage was 40 kV with a cur- rent 30 mA. The radiation source was Nickel filtered CuKα ( λ = 1.5406 Å). Next, the thermal stability of modified and unmodified PCC was observed by thermogravimetric analysis (TGA) by TA instrument, USA in a temperature range between 40 and 900 °C at 10 °C/min in a nitrogen atmosphere with 60 ml/min gas flow rate. The weight of the samples varied from 10 to 20 mg. Further, par- ticle size distribution was obtained from the PSD ana- lyzer (LA960, Horiba Ltd., Kyoto, Japan). The principle is based on static light scattering Mie theory. Approxi- mately, 0.1 g of fillers was dispersed in 100 ml distilled water and ultra-sonicated for at least 30 min prior to zeta potential measurements by ZetaPlus zeta poten- tial analyzer (Brookhaven, 205 H2oltsville, NY, USA) [26]. Image analysis of flocs was also carried out by the opti- cal microscope (Motic B1 Series). At first, modified and unmodified filler slurries were diluted to 0.2%, and one drop of the suspension was placed on the glass slides. The glass slides were then air-dried for further investiga- tion. Crystal morphology was examined by TESCAN MIRA 3 Field Emission Scanning Electron Microscope. A very little amount of sample was gold sputtered for 1 min prior to imaging. Images were taken at a magnification of 25 kX, 5kX and 2 kX with an accelerating voltage 10 kV.
2 Experimental methods
2.1 Materials
Chitosan from shrimp shells with deacetylation > 75% was procured from Hi-media, India. Precipitated Calcium car- bonate (PCC) and bleached Hardwood pulp were obtained from Paper mill, India. Hydrochloric acid (HCl) and acetic acid used in the whole study were of analytical grade. The filler suspension slurry was alkaline with pH 10.4.
2.2 Method of preparing modified PCC fillers
1 g of powder filler was dispersed in 50 ml of distilled water with a mechanical stirrer for at least 2 h before modifica- tion. 1% chitosan was dissolved in an aqueous solution of 0.1% HCl or 1% acetic acid under constant stirring at 60 °C prior to the experiments [25]. Then, 0.045 g chitosan in solution form was loaded onto the filler slurry followed by mixing for at least 30 min in water bath shaker at room temperature. The polymer percentage calculated on the basis of oven-dried (OD) PCC was 4.5%. No other auxiliary chemical was used to maintain the pH for precipitation of chitosan on PCC particles. After that, the samples were centrifuged at 3000 rpm for 10 min. The supernatant was collected for calculating the sorbed amount of chitosan by analyzing the total organic carbon (TOC) of the samples through the TOC analyzer (TOC-LCPH, Shimadzu). Depos- ited amount D A was determined by the following equation
1 −
C
C
× 100
A (%) =
2
(1)
D
M
C 1 and C 2 are the added and residual amounts of chitosan after treatment. M is the mass of PCC. All the units are
Vol.:(0123456789)
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