Solution Plasma Treatment Research Articles

Degradation of β-chitosan by solution plasma process (SPP)

In this work, the solution plasma process (SPP) is used to treat β-chitosan solutions in order to induce the degradation of chitosan. The effects of solution plasma on the properties of chitosan solutions are investigated. The treatment time was varied from 0 to 300 min. The plasma-treated chitosan was characterized by the following methods; molecular weight by GPC, viscosity, crystal structure by XRD, chemical characteristics by FT-IR, solubility by UV–vis spectrophotometer, and fractional analysis. The results showed that after treatment with plasma for 15–120 min, the viscosity of the chitosan solution and apparent molecular weight of chitosans decreased remarkably, when compared to those of untreated sample. Longer treatment times had less effect on both viscosity and molecular weight of the samples. This suggested that the degradation process of chitosan occurred during plasma treatment. The XRD analysis showed that the crystallinity of chitosan was destroyed, resulting in amorphous structure. FT-IR analysis revealed that chemical structure of chitosan was not affected by solution plasma treatment. The %yield of water-soluble chitosan was increased with increasing plasma treatment time. These results implied that solution plasma process is able to induce the degradation of chitosan solutions.

Preparation of low molecular weight chitosan using solution plasma system

Abstract The solution plasma system was introduced to treat chitosan solution in order to prepare low molecular weight chitosan. The plasma treatment time was varied from 0 min to 300 min. The plasma-treated chitosan was characterized including viscosity, molecular weight by GPC, and chemical characteristics by FT-IR. The results showed that after treated with plasma for 15–60 min, the viscosity of chitosan solution and apparent molecular weight of chitosans were remarkably decreased, compared to those of untreated sample. Longer treatment time had less effect on both viscosity and molecular weight of samples. Eventually, long treatment time (≥180 min) showed no influence on both viscosity and apparent molecular weight. This suggested that the degradation process of chitosan occurred during plasma treatment. FT-IR analysis revealed that chemical structure of chitosan was not affected by solution plasma treatment. TOF-MS results showed that chitooligosaccharides with the degree of polymerization of 2–8 were also generated by solution plasma treatment. The results suggested that solution plasma system could be a potential method for the preparation of low molecular weight chitosan and chitooligosaccharides.

Study of carboxylic functionalization of polypropylene surface using the underwater plasma technique

Non-equilibrium solution plasma treatment of polymer surfaces in water offers the possibility of more dense and selective polymer surface functionalization in comparison to the well-known and frequently used low-pressure oxygen plasma. Functional groups are introduced when the polymer surface contacts the plasma moderated solution especially water solutions. The emission of ions, electrons, energy-rich neutrals and complexes, produced by the ion avalanche are limited by quenching, with the aid of the ambient water phase. The UV-radiation produced in plasma formation also helps to moderate the reaction solution further by producing additional excited, ionized/dissociated molecules. Thus, monotype functional groups equipped polymer surfaces, preferably OH groups, originating from the dissociated water molecules, could be produced more selectively. An interesting feature of the technique is its flexibility to use a wide variety of additives in the water phase. Another way to modify polymer surfaces is the deposition of plasma polymers carrying functional groups as carboxylic groups used in this work. Acetic acid, acrylic acid, maleic and itaconic acid were used as additive monomers. Acetic acid is not a chemically polymerizing monomer but it could polymerize by monomer/molecular fragmentation and recombination to a cross linked layer. The other monomers form preferably water-soluble polymers on a chemical way. Only the fragmented fraction of these monomers could form an insoluble coating by cross linking to substrate. The XPS analysis was used to track the alterations in –O-CO- bond percentage on the PP surface. To identify the -COOH groups on substrate surface unambiguously, which have survived the plasma polymerization process, the derivatization with trifluoroethanol was performed.