γ‐Irradiation effects on the thermal and structural characteristics of modified, grafted polypropylene

Abstract

ABSTRACT:The effects of both the degree of grafting and ␥ irradiation on the thermal stability and structural characteristic of polypropylene-graft-polyvinylpyrrolidone and polypropylene-graft-polyvinylpyrrolidone modified with ␣-cyano-␦-(2-thienyl) crotononitrile were investigated. The employed techniques were thermogravimetric analysis, differential thermogravimetry, and X-ray diffraction. The thermal stability of various polymeric substrates was investigated through the determination of the degradation temperature and activation energy of degradation. The effects of different parameters on the structural characteristics of different films were investigated through the determination of possible changes in the degree of ordering of the polymeric substrates. The results revealed that the thermal stability of the trunk polymer, grafted polymer, and polymer modified by ␣-cyano-␦-(2-thienyl) crotononitrile increased progressively with an increasing degree of grafting. The increase was, however, more pronounced for the sample undergoing the lowest degree of grafting. The activation energy of the thermal degradation process remained almost unchanged, and this indicated that the degradation processes of the different films followed almost the same mechanism. The ␥ irradiation at a dose of 60 kGy of the sulfur-treated polymeric films [i.e., the polymeric films treated with ␣-cyano-␦-(2-thienyl) crotononitrile] reduced their thermal stability. This conclusion was reached by the consideration of the changes observed in the pre-exponential factor of the Arrhenius equation due to different chemical and ␥-irradiation treatments. The degree of ordering, evidenced by X-ray diffraction measurements of the trunk polymer, grafted polymer, and modified polymer, suffered a significant drop. This drop was much more pronounced for the sulfur-containing polymeric materials. The observed drop in the degree of ordering of the polymeric substrates was taken as a measure of the structure collapse due to a certain treatment (degree of grafting and sulfur inclusion). The ␥ irradiation of the sulfur-containing polymeric materials greatly increased their degree of ordering, which reached a value greater than that measured for the trunk polymer. Therefore, it was concluded that the thermal stability increased as the degree of ordering decreased.

Selectivity of Acrylic Acid Radiation Grafted Non-Woven Polypropylene Sheets towards Some Heavy Metals Ions

“…A characteristic peak around 3500 cm -1 for OH groups of poly acrylic acid is also appeared. This confirms that acrylic acid containing the carboxyl groups was fixed randomly onto the NWPP main chains as a grafting side chains [12][13][14]. Scheme 1 shows the expected structure of NWPP-g-AAc.…”

Electrical properties of modified‐grafted polypropylene

“…The effect of g-rays on the modified-grafted copolymer films exhibits the decrease in the intensity of the nitrile groups. 16 Effect of grafting yield on s and DE s Figure 1 shows the values of log s as a function of 1/T measured at temperatures within the range 303-473 K for different films undergoing various grafting yields varying between 17.5-149%. It is clearly seen from this figure that s, generally, increases as a function of the grafting yield.…”

“…15 In this work, a grafted PP with PP-g-PVP copolymer was prepared and reacted with a-cyano-b-(2-thienyl) crotononitrile. 2,3,16 The characterization was carried out by scanning electron microscope (SEM) and electrical conductivity of grafted, modified grafted, and irradiated modified-grafted films, irradiated with g-irradiation of a dose of 60 kGy. The main objective was to study the change of conductivity with activation energy and g-irradiation.…”

Effects of γ-ray radiation grafting on aramid fibers and its composites

“…The polymer materials include polypropylene [17], polyethylene terephthalate [18], polyNIMMO [poly(3-nitratomethyl-3-methyloxetane)] [19], polyurethane [20], poly(ethylene-co-tetrafluoroethylene) (ETFE) film [21], polyethylene film [22], polyethylene terephthalate (PET) film [23], the high-density polyethylene (HDPE) film [24], ramie fibers [25], carbon fibers [26], PBO fibers [27], ultra-highmodulus-polyethylene fibers (UHMPE) [28], ultra-high-molecular-weight-polyethylene fibers (UHMWPE) [29] and so on. Consequently g-ray radiation seems to be an alternative technique for the surface treatment of aramid fibers.…”