Iranian Polymer Journal / Volume 8 Number 3 (1999) 143–148 ISSN: 1026-1265/1999
Effect of Post-curing on Frictional Behaviour of Non-woven
Phenolic Composite in Automobile Clutch Facing
S.H. Jafari1, F. Fallahzadeh2 and S.K. Rana1
(1) Centre for Polymer Science and Engineering, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India
(2) Department of Mechanical Engineering, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India
Phenolic friction composite (PFC) of the non-woven type clutch facing was made from whole asbestos yarn and zinc wire cored asbestos yarn, by dipping in m-phenol based formaldehyde resin. The moulding was performed at a temperature of 140 °C and was post-cured for 2 h. The coefficient of friction of the PFC showed a decrease in the 3rd to 4th cycle when testing was performed at an interface temperature of 250 °C. Gravimetric analysis showed some loss in weight when the unpost-cured PFC was exposed to 300 °C. This was attributed to the presence of moisture and the volatile materials formed from the decomposed ingredients. Similar phenomenon was expected to occur when the coefficient of friction testing performed at higher temperatures. It was shown that the moisture increases the coefficient of friction, whereas, the volatiles decrease it and even prevents the effect of moisture. Extending the post-curing time to 4 h helps in elimination of this slippage behaviour and marginally improves many desirable properties.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 149–157 ISSN: 1026-1265/1999
Studies on Isothermal Curing and Kinetics of Degradation of
M. Ashraf Khan1, D. Cheng2, A. Zhong2 and A. Tian2
(1) Department of Chemistry, Govt. College Mianwali, Pakistan
(2) Department of Chemistry, Sichuan University, Chengdu, 610064, People's Republic of China
The cure of a two component system such as: acrylate copolymer resin with blocked 2,4-toluene diisocyanate cross-linker, which react to form polyurethane network, has been investigated using a dynamic mechanical technique, torsional braid analysis (TBA). The mixture is cured, with and without catalyst, at various temperatures. The apparent activation energy, evaluated from Arrhenius plot of logarithm of gelation time vs. I/T (K–1), for the uncatalyzed reaction is found to be greater than that of the catalyzed reaction. Furthermore, the activation energy of the system is found to decrease with increasing concentration of catalyst (dibutyltin dilaurate). The results indicate that gelation time decreases when dibutyltin dilaurate is added into the system. Degradation of polyurethane (PU) networks formed by the cross-linking reaction has, also, been studied by thermogravimetry (TGA) and activation energy of degradation of PU has been determined.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 159–165 ISSN: 1026-1265/1999
Synthesis and Characterization of Ylidic and Carbenic Polymers
G. Surpateanu*, O. Pitrel, L. Delpeuch, N.C. Lungu and F. Cazier-Dennin
Laboratoire de Synthèse Organique et Environnement, Maison de la Recherche en Environnement Industriel de Dunkerque
145 Route du Pertius d’Amont, 59140 Dunkerque, France
The synthesis of two bisylides obtained in pyridinium benzoylmethylide with terephthaloyl dichloride or 1,3-bis(p-chloroformylphenyl)parabanic acid is reported in this paper. By thermal decomposition or upon microwave irradiation, these two bisylides form the corresponding two polycarbenic derivatives. Also, the synthesis of an ylidic polymer, derived from 4,4´ dipyridylium diphenylmethylide and terephthaloyl dichloride, is annonced for the first time. All obtained products have been controlled principally by 1H NMR spectra.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 167–173 ISSN: 1026-1265/1999
Melt-rheology of Natural Rubber Modified with Phosphorylated
Cashew Nut Shell Liquid Prepolymer- A Comparative
Study with Spindle Oil
Council of Scientific and Industrial Research, Regional Research Laboratory (CSIR)
Thiruvananthapuram-695 019, Kerala, India
The mixing behaviour and melt rheology of natural rubber (NR) modified with 10 phr of both phosphorylated cashew nut shell liquid (PCNSL) prepolymer and an aromatic process oil (spindle oil) have been studied on a Brabender Plasticorder at rotor speed ranging from 30 to 90 rpm and temperature ranging from 30 to 140 °C. The plasticizing effect of PCNSL and spindle oil on NR is evident from the significant reduction in melt viscosity, power consumption for mixing and activation energy of melt flow of NR with the increase in rotor speed and temperature. PCNSL showed a higher degree of plasticization as compared to spindle oil, particularly at lower rotor speed and temperature.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 175–181 ISSN: 1026-1265/1999
Synthesis of Novel Polyurethanes with Fluorescein Linkages
S.E. Mallakpour* and H. Rostamizadeh
Organic Polymer Chemistry Research Laboratory, College of Chemistry, Isfahan University of Technology,
Isfahan, 84156, I.R. Iran
The reaction of n-propylisocyanate with fluorescein (FLU) has been performed in N,N¢-dimethylacetamide (DMAc) in the presence of triethylamine and the resulting bis-adduct has been obtained in high yield and finally was used as a model compound for the polymerization reactions. The step-growth polymerization reaction of the monomer FLU with hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), and toluene-2,4-diisocyanate (TDI) was carried out in DMAc solution and in the presence of pyridine as a catalyst. The above polymerization reactions lead to the formation of novel aromatic-aliphatic polyurethanes having fluorescein moieties in the main chain. The resulting novel polyurethanes have an inherent viscosity in a range of 0.08–0.23 dLg–1 and show light-violet fluorescence property and could be used as photoactive polymers for labeling materials. These polyurethanes were characterized by IR, 1H NMR, TGA/ DTG, DSC and elemental analyses. Some physical properties of this novel polymers are reported.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 183–191 ISSN: 1026-1265/1999
Study of the Reaction Mechanism of the Copper Chelate with
DGEBA Using DSC
M. Ghaemy, A.A. Rostami and H. Khoshnam
Department of Chemistry, University of Mazandaran, Babolsar, I.R. Iran
The reaction mechanism of metal-containing and complex compound with epoxy oligomer of diglycidyl ether of bisphenol A (DGEBA) was studied using dynamic DSC technique. It is shown that cure reaction of the epoxy oligomers with copper acetate proceeds at two stages: through the coordination of the cation with the epoxy group, and through ionic polymerization at high temperatures. The mechanism of curing of DGEBA with the copper chelate depends on the equilibrium process of dissociation of the chelate which, in turn, depends not only on the temperature of curing but also on the concentration of the hardener. At the dissociation temperature of the hardener, the polymerization proceeds according to ionic mechanism. Hardening of the epoxy oligomers due to interaction of the epoxy groups with the unconnected amine group predominates at higher temperatures or at higher concentrations of the hardener. At low temperatures and small concentrations of the hardener, the polymerization proceeds according to the catalytic ionic mechanism.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 193–204 ISSN: 1026-1265/1999
Characterization of Polyethylene Terephthalate and
Functionalized Polypropylene Blends by Different Methods
A. Oromiehie1 and I.G. Meldrum2
(1) Iran Polymer Institute, P.O. Box 14965/115, Tehran, I.R. Iran
(2) Department of Chemistry, Brunel University, Uxbridge, Middlesex UB8 3PH, UK
The properties of polyethylene terephthalate (PET) and polypropylene (PP) blends and PET with functionalized PP blends were investigated. Two compatibilizers such as: polypropylene functionalized maleic anhydride (PP-MA) and polypropylene functionalized acrylic acid (PP-AA) have been used. Several combination methods were used to characterize the blends. The differences between the properties of the blends with PP and functionalized PP indicate that functionalization had some effects. The amount of functional group is the most important factor in determining the morphology and mechanical properties. An enhancement in morphology, thermal and mechanical properties were due to interaction and adhesion between the functionalized groups with PET end groups. FTIR Spectroscopy confirmed interaction of PET end groups with functionalized PP by shifts in absorption bands of OH and C=O groups to lower frequencies due to functionalization. Solubility test provided further evidence for improved affinity between the functionalized PP and PET compared with untreated compounds.
Iranian Polymer Journal / Volume 8 Number 3 (1999) 205–213 ISSN: 1026-1265/1999
Polypyrrole Based Toxic Gas Sensors by Mass and
S.H. Hosseini and A.A. Entezami
Polymer Laboratory, Faculty of Chemistry, Tabriz University, Tabriz 51664, I.R. Iran
Gas sensors, based on conducting polymers which exhibit electrical conducting properties, can be used as selective toxic gas and vapour detectors. Their electrical resistance varies upon interaction with several substances in the gas phase, with a specificity related both to the presence of functional groups and to the shape of the target samples. The response mechanism of the conducting polypyrrole to a selection of gases and vapours was investigated using two techniques: measurement of conductance and mass changes using a four probe method, and elemental analysis by X-ray fluorescence (XRF) devices, respectively. The films were exposed to hydrogen halides, hydrogen cyanide, halogenes, hexachloroacetone (HCA), 1,3,5-trichloro-methylbenzene (TCMB), methylbenzyl bromide (MBB), bromoacetone (BA) and cyanogen bromide (CB). This suggests that the changes of conductivity of polypyrrole frequently observed are partly due to one stage of the two-stage sorption most probably involving in the swelling of the polymer. Polypyrrole sensing effects tested and comparisons made with hydrogen halides, halogens and aromatic halomethyl compounds are satisfactory, however, response times of halogens are the longest and halomethyl aromatic compounds are the shortest. It was concluded that polypyrrole’s response mechanism of sensing different gases and vapours is due to a mixed response involving electronic and physical effects.