Effect of silica nanoparticles on the impregnation process, foaming dynamics and cell microstructure of styrene-methyl methacrylate copolymer/n-pentane foams

In the present study, two-step foaming procedure with a designed in-situ foaming observation apparatus was used to study the foaming dynamics of styrene-methyl methacrylate (St-MMA) copolymer/nanosilica composites. For this purpose, the St-MMA copolymer was synthesized using suspension copolymerization and its nanocomposites were prepared using solution method. The foaming dynamics was studied through temperature-induced (two-step batch foaming) method. Furthermore, the effects of content, size and surface chemistry of silica nanoparticles on the impregnation process, the foaming dynamics and the final morphology of prepared foams were investigated. The impregnation data showed that the presence of silica nanoparticles in matrix prolonged the impregnation and decreased diffusion coefficient. This effect would be clearer where nanoparticle contents are high and the temperature is quite above Tg. The foaming dynamics results illustrated that the nucleation and foaming rate were enhanced with the nanoparticle addition and its size reduction. At the St-MMA copolymer foaming system, the silica nanoparticles with hydrophilic surface chemistry are more efficient in comparison to hydrophobic nanoparticles where all foaming dynamics and the final microstructure parameters were improved.

Application of a compositional rotatable plan in modeling the propylene content in a vinyl chloride/propylene copolymer

Using a fractional rotatable plan, the effect of five input parameters of the conduct of the copolymerization process on the amount of propylene built into the copolymer, obtained as a result of free radical suspension copolymerization of vinyl chloride with propylene in a batch suspension polymerization reactor, was analyzed. Using the results obtained, the analysis of variance was carried out and the influence of particular factors and their interactions on the product properties was determined. Thus, it was determined that the greatest influence on the amount of the incorporated propylene in the copolymer is exerted by the amount of propylene introduced into the system, while the effect of the initiator on the product properties analyzed was found to be negligible. A mathematical model was also made, and then it was improved through the use of stepwise regression and verification with the results of laboratory experiments. The adequacy of the achieved model was confirmed using the Fisher–Snedecor test. It was obtained the conformity of the constructed model with the analysis of the influence of particular factors on the propylene content in the copolymer.

A novel macroporous polymer–inorganic nanocomposite as a sorbent for pertechnetate ions

A novel magnetic macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (mPGME) was prepared by suspension copolymerization and functionalized with diethylenetriamine (mPGME-deta).

Polyacrylonitrile Based Carbon Fibers Obtained from a Melt Spun Route

Polyacrylonitrile (PAN) copolymers containg photocrosslinkable comonomer were obtained by the free-radical suspension copolymerization of Ultraviolet photocrosslinkable comonomer (UPC), methyl acrylate (MA) and acrylonitrile (AN) that was carried out in DMSO/H2O using redox as initiator in which have a typical composition of AN/MA/UPC in the mole ratio of 84/15/1. It was shown that MA was found to be suitable for enabling the melt processing of PAN. The ultraviolet sensitivity of UPC moiety improves the ultraviolet crosslinkability of the precursor fibers, as a result, the melt spun precursor fibers after ultraviolet irradiated can be oxidatively stabilized at 310 oC without melting and subsequently carbonized. The resultant carbon fibers with tensile strength of 602.2±151.3 MPa and modulus of 7.32±0.78 GPa were obtained.