Iranian polymer journal
Volume:17 Issue: 4, 2008

In this study, polypropylene (PP) and polyethylene terephthalate (PET) were blended using a single screw extruder and then fibre formation was carried out through the spinneret. The effects of PET content and PP-g-GMA as a compatibilizer were also investigated. The morphology and mechanical properties of uncompatibilized and compatibilized PP/PET fibres were comprehensively assessed utilizing scanning electron microscopy (SEM) and tensile experiments. Likewise, the drawabilities of both compatibilized and uncompatibilized systems using hot and cold methods were evaluated. It was observed that the optimum fibrillar distributed morphology would be achieved at 8 wt% of PET. Furthermore, addition of compatibilizer showed no significant morphology changes and mechanical performance improvement, although applying 3.5 wt% PP-g-GMA would result in higher crystallinity in fibres due to the nucleating effect of compatibilizer in these blends. However, the total results suggest that the fibre blend system would be improved using suitable amount of compatibilizer with proper grafting of GMA onto PP. Finally, in order to investigate the effect of compatibilizer, a sample of PP/PET blend was compatibilized with PP-g-MA as well. Mechanical properties data have shown that the PP/PET blend compatibilized with PP-g-GMA has a significant performance compared to other systems.

Anovel liquid crystalline epoxy resin (PHQEP) was synthesized by phase transfer catalytic method and characterized as a nematic liquid crystalline by polarized optical microscope (POM). The cure kinetics of diglycidyl ether of bisphenol A (E- 51)/PHQEP blends using 4,4''-diaminodiphenylsulphone (DDS) as the curing agent was studied by non-isothermal differential scanning calorimetry (DSC) at four linearly programmed heating rates of 5, 10, 15, and 20 K/min. The apparent activation energy (Ea) was determined by Friedman method, and kinetic model was predicted by Málek method. In the curing process of PHQEP/DDS, the Ea values decreased slowly with the conversion in the region of 0.2~0.5 for the formation of liquid crystalline phase. The Ea value of PHQEP/DDS system is generally higher than those of PHQEP/E-51/DDS and E-51/DDS systems and the Ea of PHQEP/E-51/DDS system is generally higher than that of E-51/DDS. This may imply that PHQEP is less reactive than E-51 in the curing process, since the molecular movement was limited because of the aromatic ester structure and the hydrogen bonds which were formed between the carbonyl groups of PHQEP and hydroxyl groups produced in the curing process. Furthermore, autocatalytic model was predicted to be the kinetic model of the above mentioned three systems. The predicted curves fit well with the experimentally obtained curves.

Dynamic vulcanization is a well known technique which improves the mechanical properties such as compression set, tensile properties, fatigue, and chemical resistance of thermoplastic elastomers. In this study, three different curing systems (sulphur, peroxide, and phenolic resin) were applied on the polypropylene (PP) /ethylene propylene diene monomer (EPDM) blends. The weight ratio of the blends was PP/EPDM: 40/60. The samples were prepared in an internal mixer at rotor speed of 60 rpm and 190ºC. Dynamic rheological parameters such as storage modulus (G'') loss modulus (G"), complex viscosity (η*), real and imaginary viscosities (η'' and η") damping factor (tan δ), and linearity region were determined at 190°C. The nonlinearity region of dynamic vulcanizated samples was shorter than that of the thermoplastic elastomer without applying dynamic vulcanization. The Cole-Cole, Han, and van Gurp-Palmen plots for all samples were drawn to make correlation between rheologies and morphologies of the blends. It was found that the rheological behaviour of dynamically cured samples was different from uncured sample, because dynamic vulcanization could affect the morphology of the blends. All samples showed morphology of the EPDM rubber dispersed in the PP matrix (droplet-matrix) with different particle size.

In this study, pH-sensitive macrocapsules containing peppermint oil (PO) were prepared using a new emulsification/polymer precipitation technique. An aqueous alkaline solution of hydroxypropyl methylcellulose phthalate (HPMCP) was used to emulsify PO in water (O/W). This emulsion was then added dropwise to a solution of citric acid to result in a solid dispersion of macrocapsules. Screening studies showed that three different factors including the polymer and the acid concentrations, as well as the essential oil to water (O/W) ratio have considerable effects on the encapsulation process. Different formulations of macrocapsules were prepared and characterized in terms of PO loading, encapsulation efficiency, and release using GC-FID analysis. A 2- level factorial design with 4-centre points was then used to optimize PO loading and encapsulation efficiency against the above mentioned parameters. Optical microscopy showed a polydispersed O/W emulsion, whereas the macrocapsules were uniformly dispersed with mean diameter of 1 mm. The prepared macrocapsules could protect PO from acidic condition of stomach and release it in a simulated intestinal fluid.

Poly (ethylene terephthalate) (PET) was blended with poly (styrene-b-tertiary butyl acrylate) (P(St-b-tBA)) and poly(styrene-b-acrylic K+) (P(St-b-AK+)) ionomer with level of block copolymer varying between 2 and 10 wt% which were prepared by atom transfer radical polymerization (ATRP). All the samples were prepared by the solution blending in phenol/tetrachloroethane (60/40 percent by weight) as solvent at 50ºC. The crystallization and melting behaviour of the sample were then studied by differential scanning calorimetry (DSC). The result showed that crystallization rate of PET was accelerated by the block copolymer as well as by its ionomer which was similar to that of a nucleating agent. The acceleration of PET crystallization rate was more pronounced by the increasing level of block copolymer. The melting temperature observed from the DSC analysis showed perturbation of crystal growth as reflected by the broadening of the melting endotherm and lowering of melting temperatures due to the presence of the specific interactions.

Metallothioneins (MTs) are a super-family of low molecular weight cysteine-rich proteins. Although many research works have been reported on their structure, application, etc., there is not any article reported on imprinted mechanism of MT-imprinted polymers, yet. These polymers are prepared by using acrylic acid (AA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, 2,2''-azobis(2-methylpropionitrile) (AIBN) as an initiator, and chloroform as a solvent. The imprinted mechanism is first studied by infrared spectroscopy analysis, Scatchard analysis, and TEM technique. Infrared spectrograms indicate the functional groups of SH in thiolate sulphurs have lone pair electrons which can form π-π bond with C=O in AA. Scatchard plot shows at least three kinds of binding sites exist in MTimprinted polymer and TEM technique indicates that most terminal thiolate sulphurs in MT are polymerized mostly as binding sites during the polymerization. The study will offer experimental foundation for further research and application of MT-imprinted polymers.

The non-isothermal crystallization kinetics of isotactic polypropylene (iPP) and iPP/microcrystalline cellulose 1 (MCC1) (hydrolyzed by HCl) and iPP/ microcrystalline cellulose 2 (MCC2) (hydrolyzed by H2SO4) composites were investigated by differential scanning calorimetry techniqye (DSC) with various cooling rates. The Avrami, Ozawa, and Mo equations were applied to describe the non-isothermal crystallization kinetics and to determine the crystallization parameters of the composites. The results show that the values of t1/2 for iPP/MCCs composites are lower than that for iPP. The value of F(T) systematically increases with increasing relative degree of crystallinity. Non-isothermal crystallizations of iPP/MCCs composites correspond to tridimensional growth with heterogeneous nucleation and MCCs acted as nucleating agent in iPP matrix. The addition of microcrystalline cellulose has greatly reduced the spherulitic size of iPP.