Synergistic effect of cellulose nanowhiskers reinforcement and dicarboxylic acids crosslinking towards polyvinyl alcohol properties

Abstract

In the presented work, a significant increase in the tensile strength of the PVA composite material is reported. The obtained best value of 122 MPa and 14.6% swelling shows the excellent synergistic effect of both crosslinker and reinforcement material. The composite films were prepared by simple mechanical dispersion of reinforcement material, bacterial cellulose nanowhiskers (BCNW) into PVA solution followed by crosslinking with diacids, succinic acid (SuA), and adipic acid (AdA). The effect of aliphatic carbon chain length of crosslinker on thermal, mechanical, and water uptake properties is evaluated and discussed in detail. Neat PVA had the strength of 37.3 MPa. With 5% reinforcement of BCNW, that is, without crosslinking, it exhibited 97% increase, that is, 74.5 MPa. With crosslinking of 15 mmol of SuA and AdA PVA films for 2 h had excellent thermal properties with swelling percentage of 19 and 26.6% and tensile strength of 103 and 67 MPa, respectively. The best result obtained was for 5% BCNW–PVA films crosslinked with 15 mmol SuA. These results were explained on the basis of synergetic crosslinking and extended hydrogen bonding between PVA and reinforcement material. The composite films can be used as biological implants, a membrane for pervaporation and filtration system, etc. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2515–2525

Rapid synthesis of high strength cellulose–poly(vinyl alcohol) (PVA) biocompatible composite films via microwave crosslinking

“…Crosslinking results in the formation of tartrate crosslinks at the expense of hydroxyl groups leading to an increase of carbonyl bond intensity at the expense of hydroxyl band. Hence, the ratio of (–C=O)/(–OH) bands for crosslinked and noncrosslinked samples is measured to confirm crosslinking as described earlier . For 35% w/w TA crosslinked PVA prepared by CH and MW methods, the values of intensity ratio (–C=O/–OH) are measured as 0.5 and 0.53 respectively, which is higher compared to PVA (0.34), confirming crosslinking.…”

“…Crosslinking PVA and cellulose not only improves mechanical strength but also impart better thermal and water resistance to the composite due to the covalent bond formation. Crosslinking hydroxyl groups between PVA chains using dicarboxylic acids, tricarboxylic acids, diisocyanates, and organosilanes is demonstrated in earlier studies. As both the PVA and cellulose have similar hydroxyls groups, it is expected that PVA and cellulose can be crosslinked using di–tri carboxylic acid and dialdehydes.…”

“…BCNW were prepared by acid hydrolysis of bacterial cellulose pellicles grown using Acetobacter xylinum (ATCC 700178) as described by Sonker et al . Bacterial cellulose pellicles were first homogenized using a tissue homogenizer (IKA T 18 digital ULTRA‐TURRAX) for 2 h. The homogenized bacterial cellulose was acid hydrolyzed by adding 63.5 wt % sulfuric acid with continuous stirring at 45 °C for 4 h. The acid was neutralized with 1 M sodium hydroxide to stop the hydrolysis and extra acid and salts were removed with deionized (DI) water using multiple centrifugation cycles (19 000 g for 30 min).…”

“…Crosslinking is usually performed by conventionally heating (CH) solid physical mixture of cellulose, PVA, and crosslinker in a hot air oven for 2–4 h . Microwave (MW) irradiation is reported to result in similar mechanical, thermal, and water resistance properties of PVA crosslinked with tartaric acid (TA) while consuming one‐eighth the period required in CH …”

“…In the present study, MW is used to develop PVA biocomposite based on the synergistic effect of bacterial cellulose nanowhiskers (BCNW) reinforcement and a TA crosslinking. To show synergy between nanoreinforcement and crosslinking, 5% BCNW concentration for nanoreinforcement is taken as described elsewhere . Similarly, 35% w/w concentration of TA is used as crosslinker .…”