Significance of grafting in curing processes initiated by UV, excimer and ionising radiation sources

Free-radical polymerization of lauryl methacrylate by differential scanning calorimetry

The polymerization of methyl methacrylate (MMA) in bulk is initiated with FeCl3 · 6H2O or FeCl3/PPh3 at 90 °C without the addition any conventional radical initiator to the polymerization system. Although the elucidation of the detailed mechanism of the initiation needs further investigation, it is likely that redox-type reactions are involved in the generation of initiating species. Once the initiating radicals are produced, the polymerization proceeds via reverse atom-transfer radical polymerization (RATRP). It was found that the polymerization is controlled up to a molecular weight of 12 900 at 92% conversion for the system using FeCl3 · 6H2O/PPh3. The chain extension experiment was carried out to confirm the controlled manner of the polymerization system. In both polymerization systems, polydispersity index and the initiator efficiency were found to be <1.4 and 0.6–0.9, respectively.

A novel initiating system for controlled radical polymerization of methyl methacrylate

Radiofrequency (RF) Ar/propylene glow discharge is utilized for grafting polypropylene onto muga silk yarn at working pressure of 1.2 × 10−1 mbar and in the of RF power range of 20–80 W. The plasma discharge is diagnosed using self-compensated emissive probe to study the variation of ion energy impinging on the substrates with RF power. From chemical compositional analysis, a possible grafting mechanism between propylene and muga yarn is proposed by considering the charge-transfer initiation through the formation of electron-donor–acceptor (EDA) complex. X-ray photoelectron spectroscopy reveals that at RF power values of 60–80 W, the ion sputtering effect becomes dominant over plasma grafting thereby leading to severe destruction in chemical structure of the polypropylene grafted (PP-grafted) muga yarns. The experimental results show that PP-grafted muga yarns exhibit improved mechanical strength and hydrophobic behavior as compared to the virgin yarn. The properties of the PP-grafted muga yarns are observed to be dependent on atomic concentration, surface morphology as well as the results obtained from plasma discharge characteristics.

Effect of Radiofrequency Plasma Assisted Grafting of Polypropylene on the Properties of Muga Silk Yarn

Polymerization of methyl methacrylate (MMA) by the charge-transfer complex formed by the interaction of sodium azide (NaN3), MMA, and carbon tetrachloride (CCl4) has been studied in dimethylsulfoxide (DMSO) medium at 60°C. The polymerization can be vastly accelerated by Lewis acids like Fe3+. This paper reports the polymerization of MMA initiated by NaN3 and CCl4 and accelerated with hexakis(dimethylsulfoxide)iron (III) perchlorate [Fe(DMSO)6] (ClO4)3 at 60°C. The rate of polymerization, Rp, was found to vary as [NaN3]0.53 and [MMA]1.43. The presence of Fe(N3)3 in the polymerization system produced well defined induction periods. The rate constant at 60°C for the interaction of poly(MMA) radical towards Fe(N3)3 was calculated to be 1.09×105 l mol−1s−1.

N.N. Dass

Papers

Charge-transfer initiation and termination