Polyolefin degradation
Sara Zarei; Gholam-Reza Nejabat; Mohammad-Mahdi Mortazavi; Soheyl KhajehPour-Tadavani
Abstract
Varying amounts of an amorphous poly(1-hexene) (PH, Mv 1.7×106 Da) were added to an LLDPE matrix containing 3% w/w Addiflex oxo-biodegradable additive (HES-W) and extruded and converted into films. Then the effect of presence of PH was investigated on microstructure, thermal and tensile behavior ...
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Varying amounts of an amorphous poly(1-hexene) (PH, Mv 1.7×106 Da) were added to an LLDPE matrix containing 3% w/w Addiflex oxo-biodegradable additive (HES-W) and extruded and converted into films. Then the effect of presence of PH was investigated on microstructure, thermal and tensile behavior of polymer films before and after 6 weeks of ultra violet irradiation (UVR). Due to UVR, viscosity average molecular weight (Mv) of the sample without PH decreased from 9.6×104 to 4.6×103 Da and for the sample containing 3% w/w PH from 11.3×104 to 3.0×104 Da, also carbonyl index (CI) of the sample without PH increased from 0 to 28.7 while for the sample containing 3% w/w PH increased from 1.8 to 30.4. Moreover, differential scanning calorimetry (DSC) showed that crystallinity of the sample without PH increased from 34.4% to 36.9% and from 28.7% to 32.1% for the sample containing 3% w/w PH. Thermal gravimetric analysis (TGA) showed lower decomposition temperature for the samples containing PH. The elongation-at-break decreased from 723.0% to 88% for the sample without PH and from 410% to 10% for the sample containing PH. Atomic force microscopy (AFM) indicated smoother surfaces for samples containing 3% w/w PH before and after UVR. Although, the aforementioned results showed that the presence of limited amounts of PH in the LLDPE matrix deteriorated thermal and mechanical properties of the matrix, it hindered the oxo-biodegradablity of the matrix by opposing assimilation process perhaps due to high Mv and/or gelation.
Structure and property relationship
Jalil Morshedian; Yousef Jahani; Farshad Sharbafian; Foroogh Sadat Zarei
Abstract
HDPE monofilaments were obtained using different extruders and drawn by post-extruder equipments. After solidification, drawn and undrawn monofilaments (draw ratio 7:1) were irradiated with 10 MeV electron beams in air at room temperature at 25, 50, 75, 100 and 125 kGy dose ranges to induce a network ...
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HDPE monofilaments were obtained using different extruders and drawn by post-extruder equipments. After solidification, drawn and undrawn monofilaments (draw ratio 7:1) were irradiated with 10 MeV electron beams in air at room temperature at 25, 50, 75, 100 and 125 kGy dose ranges to induce a network structure. HDPE crosslinking was studied on the basis of gel content measurements. The fibers were examined by differential scanning calorimetry (DSC) and measurements of mechanical properties.It was noted that gel fraction increased with irradiation dose up to 75 kGy and showed a significant increase with draw ratio, but at higher doses remained without considerable change. Melting temperature of drawn fiber increased with raising irradiation dose but decreased in undrawn sample. Also a bimodal endotherm peak was observed for drawn polyethylene irradiated in air.The changes in melting temperature and appearance of bimodal endotherm were related to the radiation chemistry of polyethylene in the presence of oxygen and interlamellar interactions. Heat of fusion and degree of crystallinity slightly increased for undrawn and drawn samples but, heat of crystallization was reduced by increasing irradiation dose due to increase the degree of crosslinking. Results of mechanical properties reveal that no significant changes seen in Young’s modulus by increasing irradiation dose. As a result of oxidative degradation happened by presence the oxygen molecules during the irradiation process, tensile properties of irradiated fibers decreased but elongation at yield for undrawn and elongation at break for drawn fibers boosted by increasing irradiation dose up to 125 kGy.
