Iranian Polymer Journal
Year:2005 | Volume:14 | Issue:9 (63)|Papers Count:9

The thermal and mechanical properties of plasticized PVC with epoxidized soya bean oil(PVC-ESBO) are studied. The repulsive interactions are used to explain the effect of epoxidization on the modulus of PVC with ESBO and plasticizer. The glass transition temperature of PVC is a linear function of the epoxidization of ESBO plasticizer. The activation energies of stabilized PVC/ESBO are also influenced by dehydrorochlorination reaction and HCl evolution. Addition of ESBO improves thermal behaviour of PVC. The higher activation energies of Ca-Zn, Ba-Zn stabilizers are responsible for the stability of PVC-ESBO. The epoxidization level of ESBO also improves the mechanical properties and thermal stability of PVC.

The resorcinol-urea-formaldehyde-casein (RSUFC) resin was synthesized by polycondensation reaction of urea, casein and formaldehyde in the presence of varying proportion of resorcinol under alkaline condition. All the prepared resins were characterized by free-formaldehyde content, free-phenol content, viscosity measurements and infrared spectroscopy (IR). The resin samples were cured isothermally at 120oC using two different curing agents, p-toluene sulphonic acid (PTS) and hexamine and also by differential scanning calorimetry on dynamic run to understand the curing behaviour of novel resin samples. The cured resins were characterized by IR and thermogravimetric analysis. The resin samples were employed for the fabrication of glass fibre and jute fibre reinforced composites, respectively by maintaining 2:3 and 3:2 proportion of resin: reinforcement. Thus prepared composites were tested for their mechanical properties and resistance towards various chemicals.

4-Aryl-2,6-bis(4-aminophenyl)pyridines (DA1-4) were prepared using the modified Chichibabin method from the reaction of 4-nitroacetophenone with substituted benzaldehydes and subsequent reduction of the intermediate nitro monomers. A model diurea compound was synthesized in high yield by the reaction of 4-phenyl-2,6-bis(4-aminophenyl)pyridine (DA1) with phenyl isocyanate via solution polymerization in Nmethyl pyrrolidone (NMP) in the presence of dibutyltin dilaurate (DBTDL) as a catalyst. Based on these conditions, novel polyureas (PU1-16) were prepared by the reaction of (DA1-4) with 4,4-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 1,4-phenylene diisocyanate, and 1,6-hexamethylenediisocyanate. The resulting polyureas had inherent viscosities in a range of 0.33-0.40 g dL-1 in DMSO at 30oC. These polyureas were characterized by IR, 1H NMR, elemental and thermal analysis. The resulting polymers were soluble in common polar aprotic solvents. The physical properties and structural characterization of these polymers were also reported.

Slurry copolymerization of ethylene and propylene (EPM) was carried out in dry nheptane using high activity catalyst system of SiO2/MgCl2/TiCl4/EB/TiBA (or TEA)/MPT/H2. The structure of four EPM samples with ethylene content of 30%, 40%, 50% and 80% were analyzed using 13C NMR method. The complex spectra taking at high field are interpreted as resulting from ethylene propylene sequence placements. A methylene sequence distribution from one to six is given for four different ethylene propylene copolymer samples distribution. Increasing ethylene content of the copolymer increased EEE triad and decreased PPP triad distributions. Due to higher activity of ethylene monomer increasing its content from 30% to 80% the EEE triad distribution increased from 4.5% to about 73%. In the sample containing 30% of ethylene the PPP triad was less than 30% which is an indication of very high relative activity of ethylene to propylene for copolymerization using the catalyst system. The catalyst system used was quite active for the copolymerization and may introduce alternative sequence distribution in the polymer chain. Higher portion of propylene in the copolymer significantly increased the sequence of single methylene units and decreased six and more consecutive units. The EPM copolymer containing 30% to 50% ethylene have amorphous properties.

4,4'-Oxydiphthalic anhydride (1) was reacted with L-isoleucine (2) in acetic acid and the resulting imide-acid (3) was obtained in high yield. The diacid chloride 4 was obtained from diacid derivative (3) by reaction with excess thionyl chloride. The polycondensation reaction of diacid chloride 4 with several aromatic diamines such as 4,4"-sulphonyldianiline (5a), 4,4'-diaminodiphenyl methane (5b), 4,4'-diaminodiphenylether (5c), p-phenylenediamine (5d), m-phenylenediamine (5e), and 4,4'-diaminobiphenyl (5f) was accomplished by two conventional methods: low temperature solution polycondensation and short period reflux conditions. In order to evaluate conventional solution polycondensation reaction methods with microwave-assisted polycondensation, the reactions were also carried out under microwave conditions in the presence of small amount of o-cresol that acts as a primary microwave absorber. The reaction mixture was irradiated for 6 min with 100% of radiation power. A series of new optically active poly(amide-imide)s (PAIs) with inherent viscosity ranging from 0.22-0.44 dL/g has been prepared with high yield. All of the above polymers were fully characterized by FTIR, elemental analyses and specific rotation techniques.

The present paper studies the effect of chitosan, cationic starch and polyvinyl alcohol (PVA) as sizing agents to enhance surface properties of kenaf paper. The polymers were incorporated into the sheets by spray application. The results clearly showed that the addition of chitosan to a sheet formed from beaten fibres had excellent improvement in surface properties, compared to the effect of other additives. Sizing quality of cationic starch fairly matched with the sizing quality of chitosan, however, it was able to reduce the water absorption potential of paper more than chitosan at a same concentration. In most other properties, particularly the most important property for printing papers, surface smoothness, chitosan-sized papers are superior to the paper sized with cationic starch or PVA.

Poly(N-substituted urethane)s with different molecular weights of polyethylene glycol monomethyl ether side chain were synthesized form sodium hydride, chlorinated polyethylene glycol monomethyl ether (PEGMME), and polyether and poly ester urethane containing polytetrahydrofuran or polycaprolactone/toluene diisocyanate and 1,4-butanediol. The chemical structures were characterized with FTIR and FT-1H NMR. To investigate the effect of different MW of N-substituted side chain on the morphology, thermal property and particle size distribution of the final product, we used differential scanning calorimetry and laser light scattering. N-Substitution of polyurethane had significant influences on thermal properties and solubility of the resulting material. Tg of the N-substituted urethane decreases with N-substitution and gradually increases with increasing molecular weight of the substituted side chain. This is more obvious in higher molecular weight. The particle size of final water borne PU emulsion also decreases with increasing MW of PEGMME. The decreasing particle size may be due to increased chain flexibility and or hydrophilicity of N-substituted polyurethanes.

Cartilage is a tissue that has a low potential for self-repair. One of the methods for improvement of regeneration and metabolism in cartilge, is to stimulate physical factors on chondrocytes as cartilage based cells. In this research, two physical factors, oxygen tension and pH, were changed to measure the cell viability of chondrocytes on Degrapol®, as a biodegradable polyurethane (DBS), and alginate scaffolds and cell viability onto these substrates are compared. The results showed that, physical factors like oxygen and pH could change cell viability. After 3 days cell culture for both types of scaffolds, the cell viability was higher with 5% O2 and pH=7.4 and it was not dependent on the type of scaffolds. Our results showed that cell viability on alginate beads is more than DBS scaffold for different conditions.

Papers made from bagasse chemimechanical pulp were chemically modified by acetylation. A combination of sodium borohydride reduction and acetylation was also tested. Efficient inhibition of photo-yellowing of papers made from bagasse CMP was achieved by acetylation. The acetylated unbleached CMP was noticeably photo-bleached during irradiation. Sodium borohydride reduction followed by acetylation had the same effect as acetylation alone at the same degree of reaction time. The prereduced, acetylated unbleached papers were, however, not brightened during irradiation. The reductive treatment had little effect in reducing the photo-yellowing of paper made from CMP pulp; a small stabilization effect was observed in the case of bleached CMP, while unbleached CMP was slightly more prone to discolour in the later phase of photoreversion. The improved stability towards light was closely related to the decrease in the phenolic hydroxyl content as a result of blocking by acetyl groups during treatment with acetic anhydride. The results support the hypothesis that phenolic hydroxyl has an important role in the process of photo-reversion of high-yield pulps.