Iranian Polymer Journal / Volume 5 Number 4 (1996) 225230                                                                                               ISSN: 1026-1265/1996

 

 

Surface Modification of Ethylene‑Propylene Rubber by Laser

 

Grafting of Acrylic Acid

 

H. Mirzadeh, A.R. Ekbatani and A.A. Katbab

Amir Kabir University of Technology, Tehran, I.R. Iran

 

ABSTRACT

 

In spite of the good bulk mechanical properties of ethylene‑propylene rubber the low surface water compatibility is the main difficulty with this polymer to be used as a biomaterial. Peroxides formed on the surface by CO2‑pulsed laser treatment through peroxidation mechanism has been found as a successful technique to initiate the graft copolymerization of hydrophilic acrylic acid onto the surface of this rubber. The fractal type of morphology formed by the grafted chains enables us to control the hydrophobic to hydrophilic site ratio which is the main key in determining the extent of biocompatibility of polymer surfaces. Grafting occurs successfully and is found to be dependent upon laser pulse number. Energy dispersive X‑ray analysis (EDXA) and attenuated total reflectance infrared (ATR‑IR) have been employed to characterize the surface chemical compositions. Modified surfaces show significant improved water compatibility, the degree of which depends upon the surface morphology and the grafting level.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 231235                                                                                               ISSN: 1026-1265/1996

 

 

Thermoplastic Polyurethane Elastomers: Synthesis, and Study of

 

Effective Structural Parameters

 

M. Barikani and M. Barmar

Polymer Research Center of Iran, P.O. Box: 14185/458, Tehran, I.R. Iran

 

ABSTRACT

 

In this study two classes of polyols, a polyether and a polyester, are used for synthesizing thermoplastic polyurethane elastomers. These elastomers are prepared by chain extension of polyol/toluene diisocyanate by prepolymer method and a variety of chain extenders. The effect of polyester and polyether polyols and chain extenders on thermal stability have been investigated by studying their morphology using dynamic mechanical thermal analysis (DMTA), and thermogravimetric analysis (TGA). The physical and mechanical properties of prepared polyurethane elastomers are measured. The obtained results are investigated and discussed.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 237241                                                                                               ISSN: 1026-1265/1996

 

 

Studies on Rheological Behaviour of LDPE/EPDM Blends,

 

Using a Torque Rheometer

 

M. Razavi Nouri and M. Mehrabzadeh

Polymer Research Center of Iran, P.O. Box: 14185/485, Tehran, I.R. Iran

 

ABSTRACT

 

In this work, selected grades of LDPE and EPDM have been melt‑mixed over the complete range of compositions. The effect of compositions on the rheological behaviour, dynamic elastic properties and flow activation energy was studied by a torque rheometer. The results show that the more LDPE in the blend, the lower melt viscosity and the total work energy but higher flow activation energy and dynamic elastic properties.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 243249                                                                                               ISSN: 1026-1265/1996

 

 

Synthesis of Diclofenac Polymeric Prodrugs

 

and Their Hydrolysis Reactivity

 

M.H. Nasir Tabrizi, S. Davaran and A.A. Entezami

Polymer Laboratory, Faculty of Chemistry, Universty of Tabriz, Tabriz, I.R. Iran

 

ABSTRACT

 

In order to minimize the sodium diclofenac side effects and to increase its therapeutic efficiency, polymeric prodrugs of the diclofenac are prepared. Diclofenac is attached to polychloromethylstyrene, polyvinyl chloroacetate and polyethylene glycol through the hydrolyzable ester bonds, and assessed in vitro for usefulness as diclofenac prodrugs. Specially designed spacer groups are introduced between the drug and polymer backbone. The polymers are characterized by FTIR, 1H NMR and 13C NMR spectroscopy. The hydrolysis of polymer‑drug conjugates is carried out in cellophane membrane dialysis bags containing aqueous buffer solutions (pH=8, 37 ºC). The hydrolysis solution was detected by UV spectrophotometry at selected intervals. The results have shown that these polymers are potentially useful as polymeric prodrugs. It is found that polyvinyl chloroacetate is an appropriate carrier for release of the drug in human conditions.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 251257                                                                                               ISSN: 1026-1265/1996

 

 

Thermal Non‑oxidative Degradation of PVC and Stabilizing

 

Action of Various Surfactants Salts of Fatty Acids

 

M. Ashraf Khan, S. Sakhawat Shah, and Zahoor Ahmad

Department of Chemistry, Quaid-Azam University, Islamabad 45320, Pakistan

 

ABSTRACT

 

Surfactant salts of 3 different fatty acids (i.e., stearic, palmitic and lauric acids) with lead and metals of group IIB were prepared, and the effect of the size of cations and the nature of anions on dehydrochlorination process involved during degradation of polyvinyl chloride, using conductivity and thermogravimetric techniques, have been studied. The effectiveness of these salts depends upon the electronegativity of the metal ion and even more on the hard acid character. The size of the cation also plays an important part, and metal stearates are found to be more effective in blocking the zip elimination of hydrochloric acid as compared to the corresponding palmitates and laurates due to their relatively large sizes.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 259266                                                                                               ISSN: 1026-1265/1996

 

 

Effect of Surface Chemistry on Protein Interaction with

 

Hydrogel Contact Lenses

 

R. Sariri and B. Tighe

Department of Chemical Engineering and Applied Chemistry, Aston University, Birmingham, UK

 

ABSTRACT

 

Protein is one of major classes of contaminations for hydrophilic contact lenses. The absorption of individual proteins from single protein solutions in vitro on different materials has been measured. The effect of water content and surface chemistry of the lens in terms of ionic characteristics on the interaction of different proteins have also been studied. A series of contact lenses with different surface and structural properties have been used to study the effect of hydrogel material on the quantity of charged or uncharged protein absorbed. The early stages of interaction and the leaching of protein from the contact lens into storage solution have been studied for proteins deposited in vitro and in vivo.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 267270                                                                                               ISSN: 1026-1265/1996

 

 

Solution Properties of Poly(2‑ethylhexyl acrylate) in

 

Theta‑Solvents

 

E. Lathova and D. Lath

Polymer Institute, Slovak Academy of Science, 842 36 Bratislava, Slovak Republic

 

ABSTRACT

 

Unperturbed dimensions of poly(2‑ethylhexyl acrylate) using direct measurements in theta‑solvents and graphical procedures for viscosity data in good solvents are determined. Calculated conformational parameters confirmed the flexible character of poly(2‑ethylhexyl acrylate), having increased stiffness due to its long side chain.

 


Iranian Polymer Journal / Volume 5 Number 4 (1996) 271278                                                                                               ISSN: 1026-1265/1996

 

 

Isothermal Axial Laminar Flow of Non‑Newtonian Fluids in

 

Concentric Annuli (Power‑Law and Sisko Fluids)

 

A. Bahrami, S. Azizmohammadi, M.R. Golkar Narenji and V. Taghikhani

Department of Chemical Engineering, Amir Kabir University of Technology, Tehran I.R. Iran

 

ABSTRACT

 

In attention to industrial significance of non‑Newtonian fluids, determination of flow behaviour under various operational conditions is desirable. In this paper the isothermal and axial laminar flow of non‑Newtonian fluids (power-law and Sisko) in annuli have been analyzed. In the first step the governing equations (equation of motion and rheological model) are solved with using a numerical method for power‑law fluid, and the volumetric flow rate values are obtained. Then by comparing with a semi‑analytical method and the methods proposed by the other workers, the accuracy of results is confirmed. Finally this numerical method is applied to Sisko fluids and the results are presented.