The effect of pro‐degradant distribution in polyethylene (PE)/starch blends on ultraviolet (UV) photo‐oxidative degradation was investigated. Two kinds of pro‐degradants, Fe and Co‐based, were used in this study. The distribution of pro‐degradants in the different phases was varied by a dual step process using a side‐feed on a reactive extruder. The variation in mechanical properties and evaluation of carbonyl groups by FTIR were conducted to investigate the effect of degradation following exposure to UV photo‐oxidative degradation. It was found that the variation in mechanical properties was higher when the pro‐degradants were distributed in the PE phase. The concentration of carbonyl groups increased as a function of UV exposure, and the concentration of carbonyl groups was higher when the pro‐degradants were distributed in the PE phase. Micro‐cracking was observed on the interface between starch and PE after adding the pro‐degradants. When the pro‐degradants were distributed in high‐density polyethylene (HDPE) phase, the micro‐cracks mainly appeared in HDPE matrix, and the density of micro‐crack was higher. In general, the function of the pro‐degradants in PE/starch blends was enhanced when their distribution was varied within HDPE phase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Stability and photodegradation studies of HDPE film blended with recycled HDPE, with and without pro-oxidant, were carried out by subjecting the film to accelerated UV exposure up to 144 hours. Two types of recycled HDPE were used; one containing pro-oxidant (recycled degradable HDPE-RDH) and the other without pro-oxidant (recycled standard HDPE-RSH). The loading levels of recycled HDPE were varied from 10 to 30% by weight. The degradation behaviour of the film was then evaluated based on elongation at break, carbonyl index and oxidative induction time (OIT). The results obtained show that the degradation rate of HDPE films, with different levels and types of recycled HDPE (RSH and RDH), were directly correlated to UV exposure time. However, more pronounced changes in elongation at break and carbonyl index were observed, in particular the HDPE film blended with RDH. At 30% loading of RDH, the film degraded at a higher rate compared with film containing the same level of RSH. This suggests that HDPE blended with RDH even at a low loading of 10% could promote degradation of the film. The remaining pro-oxidants in RDH induced the formation of free radicals in the HDPE chain and accelerated the degradation process.
Offshore structure decommissioning and abandonment is a critical component in the life cycle of hydrocarbon production. In Malaysia, 11% of platforms and 8% of pipelines have been in service for more than 40 years, much exceeding their intended lifespan. Conventional methods of decommissioning offshore platform are inherently very costly with the mobilization and operation of HLV (Heavy Lift Vessel). This study developed an Offshore Flexible Buoyancy Tank (OFBT) as the buoyancy assembly to execute future small structure removal operation. This study applies the structured material selection process to determine suitable material as buoyancy assembly enclosure. According to the concept, material selection seeks to determine the lightest, pressure-sustaining, fracture-resistant and cost-effective buoyancy bags suitable for the application. This is a problem with 3 objectives: minimize weight, minimize cost, and withstand the internal pressure in above or submerged conditions. A range of material is tested based on the parameters, and it was determined that Two layers of PET membrane is proposed for OFBT with capacity not less than 380 kN/m. An additional layer is also required to protect the buoyancy bag from puncture or tear. Yard burst test testing is implemented to determine the accuracy of FEA model. A prototype OFBT is fabricated to consist of 3-layer flexible polymer sheet to create an air-containment enclosure. Overall, the FEA correlates well with the result from the burst test. Both burst tests indicate the failure to occur the flange area. The circumferential stiffeners were observed to fail first followed by Longitudinal stiffeners. Results from this work is integrated in the research towards the development of novel flexible offshore buoyancy tank assembly for the removal of jacket structure in decommissioning and abandonment suited to the application in Malaysia.
β-nucleant is used in polypropylene homopolymer (h-PP) primarily to improve its toughness as this particular property is important for piping and pipe coating application. In this work, the effect of β-nucleating agent on h-PP as topcoat material for pipe coating was investigated. The distribution of the nucleating agent in h-PP was controlled by solid-phase reactive extrusion. It was found that when subjected to second cycle of thermal exposure, the effect of β-nucleant upon h-PP crystallinity had increased significantly. This was desirable as it would enhance topcoat toughness. Several heating cycles were used to mimic the number of thermal exposures during processing. The effect of this simulated thermal history on the toughness enhancement was assessed and reported. The work has shown that, after a number of consistent thermal cycles, the percentage of β-crystals phase remained level. This will provide a much needed assurance on thermal and mechanical consistency in β-nucleated h-PP as well as enhance its viability for pipe coating applications.
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