Iranian Polymer Journal / Volume 7 Number 4 (1998) 225–233                                                                                               ISSN: 1026-1265/1998

 

 

Free Radical Polymerization of Methyl Methacrylate:

 

Modeling and Simulation by Moment Generating Function

 

S. Curteanu, V. Bulacovschi, and C. Lisã

Technical University “Gh. Asachi”, Department of Industrial Chemistry, B-dul Mangeron 71, 6600 Jassy, Romania

 

ABSTRACT

 

The batch bulk isothermal polymerization of methyl methacrylate (MMA), in which the initiation is achieved by the decay of an initiator and termination by disproportionation is considered for modeling. According to the kinetic diagram one can make a deduction of the mathematical model in terms of the moment generating function and in terms of moments which give the distribution of the molecular weights. In order to quantify the gel and glass effects, the relations proposed by Chiu et al. are used [1]. The results given by the two solving techniques, generating function and moments, are compared and discussed. The comparison of the simulation and the experimental data represents the model validation and thus a guarantee for its use in various studies of polymer engineering.

 

Iranian Polymer Journal / Volume 7 Number 4 (1998) 235–241                                                                                               ISSN: 1026-1265/1998

 

 

Optical Properties of Polyacrylonitrile Molecules in

 

N,N-Dimethylacetamide

 

I.A. Strelina, V.A. Cherkasov, and P.N. Lavrenko

Institute of Macromolecular Compounds, RAS, Bolshoy pr., 31, Saint Petersburg 199004, Russia

 

ABSTRACT

 

The present paper deals with the investigations of hydrodynamic properties of PAN, as an engineering material with increasing technological interest.  The methods of translational diffusion, velocity sedimentation and viscometry are employed. At first time, optical anisotropy of the PAN molecule was determined with flow birefringence technique which is very sensitive to intramolecular structure. The PAN sample with molecular weight of 9´105 and low stereoregularity was studied in dilute solution in N,N-dimethylacetamide. Intrinsic viscosity was calculated according to Huggins equation from the dependence of reduced viscosity on concentration of solution. Molecular mass was determined with Svedberg's equation. The heterogeneity parameter was evaluated by the absolute method of analytical ultracentrifugation. Translation diffusion was investigated using a gradient method in a cell Teflon in the Tsvetkov's interferometric diffusometer. The flow birefringence measurements were made in titanium dynamooptimeter and the Hg-lamp was used as a light source. The sign of the effect and the stress optical coefficient were determined. The role of the micro­ and macro form effects in flow birefringence is discussed. The intrinsic optical anisotropy
(-3.3´10-25) cm3 of the chain unit of the PAN molecule is attributed to structural features of the polymer molecule and anisotropy of the cyanogroups.

 

Iranian Polymer Journal / Volume 7 Number 4 (1998) 243–253                                                                                               ISSN: 1026-1265/1998

 

 

Dibenzyl Structure on the Macromolecular Chains (VII):

 

Heterocyclic Polymers from 2,2¢,4,4¢-Dibenzyl Tetramine

 

E. Scortanu, G. Caraculacu, and A.A. Caraculacu

Institute of Macromolecular Chemistry, Romanian Academy, P.Poni, Aleea Ghica Voda 41A, 6600 Jassy, Romania

 

ABSTRACT

 

Some high molecular polymers with imide or parabanic structures were synthesized and characterized. The improvement of their film-forming ability by the addition of small quantities of 2,2¢,4,4¢-dibenzyl tetramine was studied. The synthesis of the polyfunctional monomer was conducted. The prepolymers like the polyamic acids and polyureas were obtained by using strict controlled concentrations of monomers, as well as, by carefully watching the reaction time and temperature. Heterocyclic polymers were produced by cyclodehydration of polyamic acids into polyimides or by intermolecular heterocyclization of polyurea with oxalyl chloride yielding polyparabanic acid. The polymers were characterized by solubilities, viscosities, IR spectra, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction measurements.

 

Iranian Polymer Journal / Volume 7 Number 4 (1998) 255–261                                                                                               ISSN: 1026-1265/1998

 

 

Partial Replacement of Silica by White Rice Husk Ash in

 

Natural Rubber Compounds: The Effects of Bonding Agents

 

H. Ismail and F.L. Chung

School of Industrial Technology, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia

 

ABSTRACT

 

The effects of bonding agents on the partial replacement of silica by white rice husk ash (WRHA) in natural rubber compounds were studied. Results showed that the optimum weight ratio of WRHA/silica to obtain maximum enhancement of tensile and tear strengths was 20/30 (phr/phr). Increasing the WRHA in weight ratio of WRHA/silica decreases the cure time, t90, scorch time, t2, hardness and elongation at break but increases the resilience of the vulcanizates. For similar vulcanizates, the incorporation of bonding agents enhanced the tensile strength, tear strength, hardness, rubber-filler interaction and resilience, whereas, the elongation at break decreased. The incorporation of bonding agents also increases the t90 and t2.

 

Iranian Polymer Journal / Volume 7 Number 4 (1998) 263–269                                                                                               ISSN: 1026-1265/1998

 

 

Synthesis and Study of Thermal Properties of New Heat Stable

 

Poly(ether-ketone)s and Poly(ether-ketone-sulphone)s

 

A. Banihashemi and B. Akhlaghinia

Chemistry Department, Faculty of Science, Shiraz University, Shiraz 71454, I.R.Iran

 

ABSTRACT

 

Benzofuro[2,3-b]benzofuran-2,9-dicarboxylic acid reacts with a number of diaryl ethers in phosphorous pentoxide/methanesulphonic acid (PPMA) media. The resulting poly(ether-ketone)s and poly(ether-ketone-sulphone)s, obtained by direct polycondensation reaction, are characterized with FT-IR spectroscopy and elemental analysis. Thermal properties of polymers are investigated by TGA and DSC methods and their heat stabilities are compared. The thermal properties can be modified by introducing an equimolar amount of a diacid or diarylether by which thermal cross-linking sites are provided.

 

Iranian Polymer Journal / Volume 7 Number 4 (1998) 271–275                                                                                               ISSN: 1026-1265/1998

 

 

Synthesis and Study of a Novel Copolymer of Acrylic/Citraconic

 

Acids for Self-cured Dental Glass Ionomer Cement

 

M. Keyanpour

Materials and Energy Research Center, P.O. Box: 14155-4777, Tehran, I.R. Iran

 

ABSTRACT

 

For comparison of acrylic-itaconic acids copolymers, the acrylic/citraconic acids copolymer is synthesized via emulsion polymerization, and then it is used as aqueous solution along with an ion-leachable glass for formulation of a self-cured glass ionomer dental cement. The presence of the methyl group in citraconic acid, and also less stereoregularity of the copolymer, compared to acrylic/maleic acids copolymer, both maintain hindered hydrogen bonding in the copolymer in aqueous solution over a long period of time and therefore gel formation does not occur. It has been found that the mechanical and physical properties of the formulated self-cured cement are in the range of those obtained for commercial sample and the S42L21 sample which is made from acrylic/itaconic acids copolymer.

 

Iranian Polymer Journal / Volume 7 Number 4 (1998) 277–287                                                                                               ISSN: 1026-1265/1998

 

 

A Three-dimensional Finite Element Analysis of a

 

Power‑law Fluid in an Extrusion Die

 

M.H.R.Ghoreishy and M. Razavi Nouri

Iran Polymer Institute, P.O. Box 14965/115, Tehran, I.R. Iran

 

ABSTRACT

 

This research work is devoted to the development of a mathematical model for the simulation of the flow of polymeric melts through the die region of extruders. The set of the governing equations are solved using the finite element method. Standard Galerkin technique is used in conjunction with the continuous penalty scheme to solve the flow equations. Due to the non-linear nature of the global equations, the Newton‑Raphson method is used. In order to show the applicability of this model, we have simulated the flow of a polypropylene (T30S®) melt in the die of a single screw extruder. The well-known power-law equation is used to describe the non-Newtonian rheological behaviour of this material. The validity of the present technique under realistic conditions is confirmed by the comparison of the model simulation results with the experimental data.