Effect of temperature on initial stage of methyl methacrylate free radical bulk polymerization

Classic theory of free radical polymerization is based on two assumptions. The first is that the concentration of initiator is slightly changed and could be taken as a constant value. The second assumption is that the rate of initiation is equal to the rate of termination. Equation for the polymerization rate based on these assumptions can not successfully describe the initial stage of free radical polymerization. In order to solve this problem, three mathematical models were developed and used to verify of the mentioned assumptions. The models were fitted to experimental data and qualities of their fits were compared. Experimental data of isothermal bulk polymerization of methyl methacrylate were obtained by differential scanning calorimetry at 60, 70, 80 and 90°C with initiator concentration (AIBN) of 0.5 wt%. The best fit was shown by the model that assumes constant concentration of initiator during initial stage but takes into account that the rate of initiation is not equal to the rate of termination at the beginning

Novelties in macromolecular synthesis

In 2003 more than 240 million tons of polymeric materials were produced in the world. The average growth of polymer production in the last five years was about 5 wt.% and it is expected that this trend will continue up to 2008. The results of macromolecular synthesis research for a long period of time have a significant contribution to the continuous economical success of the polymeric materials industry. The most significant results achieved in the last several years in various fields of macromolecular synthesis research are presented in this article

Kontaminacija polimera teškim metalima

The contamination of important synthetic (surface unmodified) polymers by various heavy metal compounds (such as copper, manganese and lead) in aqueous medium was investigated in this study. The influence of the pH of the aqueous medium, temperature and metal type on contamination was investigated during a 10 day period. It was found that increasing pH contributed to higher polymer contamination (at higher pH 100 times for copper and up to 400 times for lead), as well as contact with easily penetrable substances. Increasing temperature decreased contamination by the metal compound for PELD and PET which was not the case for PEHD and PR.U radu je praćena kontaminacija najznačajnijih sintetskih (površinski nemodifikovanih) polimera teškim metalima (prevashodno bakrom, manganom i olovom) u vodenoj sredini. Praćen je uticaj više faktora (pH vrednost rastvora, temperatura i tip metala) tokom perioda od 10 dana. Utvrđeno je da porast pH vrednosti uzrokuje porast kontaminacije metalima (kod bakra 100 a kod olova i do 400 puta), kao i kontakt polimera sa supstancama koje lakše prodiru u polimer od vode. Zapaženo je smanjenje kontaminacije teškim metalima samo kod polletllena niske gustine (PENG) i poli(etilen tereftalata) (PET) usled rasta temperature, a ne i kod polietilena visoke gustine (PEVG) i polipropilena (PP)

Packaging based on polymeric materials

In the past two years the consumption of common in the developed countries world wide (high tonnage) polymers for packaging has approached a value of 50 wt.%. In the same period more than 50% of the packaging units on the world market were made of polymeric materials despite the fact that polymeric materials present 17 wt.% of all packaging materials. The basic properties of polymeric materials and their environmental and economical advantages, providing them such a position among packaging materials, are presented in this article. Recycling methods, as well as the development trends of polymeric packaging materials are also presented

Polymerization of organized monomers

The current explanations of olefin and vinyl monomer polymerization propose that monomer molecules are successively added one by one to the growing polymer chain. This may be true if the monomer molecules exist as individual species in a polymerizing system, e.g. in dilute solutions of monomer. There are cases, however, in which monomer molecules are organized: bulk liquid monomer, solid monomer, a monomer monolayer adsorbed on a support, etc. Various supra-molecular species and particles of monomer exist in such cases. In the 1960-ties, Semenov, Kargin and Kabanov proposed a theory of organized monomer polymerization. In the last 25 years, our research group has further developed and applied that theory to various polymerizing systems: the radical polymerization of compressed ethene gas, the radical polymerization of liquid methyl methacrylate, olefin polymerization by transition metals and by Al-based catalysts. An outline of the main achievements are presented in this article