A Novel Continuously Initiated Polymerization by One-Atmosphere Low Temperature Plasma Device

A novel atmospheric plasma device developed in this paper, which is more effective and convenient to study the plasma-initiated polymerization (PIP) than conventional setup. The structure and mechanism of the device is introduced. Some plasma-initiated polymerization experiments are carried out on the device, and the conversion of AA (Acrylic acid) and AM (Acryl amide) atmospheric (N2) plasma polymerization are respectively 89% and 94% after 120 h post polymerization, whereby IR spectra of the product (AA, AM). Our PIP result are confirmed.

Numerical Analysis of Plasma Initiated Polymerization

Plasma initiated polymerization is a kind of well-known radical polymerization mechanism, but it has the ＇living＇ polymerization feature and produces ultra-high molecular weight polymer. In order to explain such phenomena, we calculate the basic data of plasma initiated polymerization of methylmethacrylate （MMA） according to the principle of polymer physics and chemistry. It results in that the radical concentration ranges from 10^-12mol/L to 10^-16mol/L corresponding to the radical life in 10^4s to 10^8s, which means the radicals have a long lifetime. Moreover because of the long lifetime radicals it causes a unique feature rather than the common radical polymerization, and also shows no ＂living polymerization＂. It is noticed in experiments that there are two key factors playing important roles. One is the effective radical amount produced during the plasma discharging while the another is the diffusion factor.

Studies on the Mechanism of Methyl Methacrylate Polymerization Initiated by Volatile and Nonvolatile Products of Methyl Methacrylate Plasma

he volatile (VPP) and nonvolatile (NVPP) products of methyl methacrylate(MMA) reaction in plasma chamber were used as initiators of MMA polymeriza-tion. From the structure analyses of the two initiators, the measurement of poly-merization kinetics, and the determination of the molecular weight of resultantpolymers , we found tliat MMA polymerization initiated by NVPP is a typical radical mechanism of polymerization which undergoes a process of continuous initiationand bifunction termination , while VPP-initiated polymerization suggested a mech-anism of living radical process fpolymerization with instantaneous initiation , chain-transfer to monomer , without termination).

Effect of actuating frequency on plasma assisted detonation initiation

Aiming at studying the influence of actuating frequency on plasma assisted detonation initiation by alternating current dielectric barrier discharge, a loosely coupled method is used to simulate the detonation initiation process of a hydrogenoxygen mixture in a detonation tube at different actuating frequencies. Both the discharge products and the detonation forming process which is assisted by the plasma are analyzed. It is found that the patterns of the temporal and spatial distributions of discharge products in one cycle are not changed by the actuating frequency. However, the concentration of every species decreases as the actuating frequency rises, and atom O is the most sensitive to this variation, which is related to the decrease of discharge power. With respect to the reaction flow of the detonation tube, the deflagration-todetonation transition（DDT） time and distance both increase as the actuating frequency rises, but the degree of effect on DDT development during flow field evolution is erratic. Generally, the actuating frequency affects none of the amplitude value of the pressure, temperature, species concentration of the flow field, and the combustion degree within the reaction zone.

Influence of the initial transient state of plasma and hydrogen pre-treatment on the interface properties of a silicon heterojunction fabricated by PECVD

Amorphous/crystalline silicon heterojunctions（a-Si：H/c-Si SHJ） were prepared by plasma-enhanced chemical vapor deposition（PECVD）.The influence of the initial transient state of the plasma and the hydrogen pre-treatment on the interfacial properties of the heteroj unctions was studied.Experimental results indicate that： （1） The instability of plasma in the initial stage will damage the surface of c-Si.Using a shutter to shield the substrate for 100 s from the starting discharge can prevent the influence of the instable plasma process on the Si surface and also the interface between a-Si and c-Si.（2） The effect of hydrogen pre-treatment on interfacial passivation is constrained by the extent of hydrogen plasma bombardment and the optimal time for hydrogen pre-treatment is about 60 s.