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Because of the great economic interest in propylene‐based polymers and the possibility of designing materials with desired properties with metallocene catalyst mixtures, we investigated the characteristics of polypropylenes produced by mixtures of SiMe2Ind2ZrCl2: dimethylsilane‐bis(indenyl) zirconocene (1) and Et(Flu)(Cp)ZrCl2: ethylidene (fluorenyl cyclopentadienyl) zirconocene (2) in different proportions. The polymers were fractionated with solvents, and the fractions were characterized. We observed that the polymers produced by the different mixed systems showed lower weight‐average molecular weights and only slightly broader molecular weight distributions than polypropylenes synthesized by the individual catalysts. We concluded that catalyst 1 acted independently of catalyst 2, producing polymers with the same isotacticity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1478–1485, 2003

Cement attack by acid during matrix acidizing operations has created severezonal isolation problems in wells with multiple adjacent permeable zones, operated by PETROBRAS. This effect was observed in several wells treated with conventional HCl-HF acid mixtures, even when cement bond logs prior to the acidjob were excellent. This paper presents a series of lab experiments showing that acetic acid, alone or mixed with HF, dissolves much less cement than HCl and HCl-HF mixtures with the same carbonate dissolving power. The reaction of acetic acid with cement forms a protective skin that inhibits further acid attack. The organic formulations were tested in an acidizing simulator, before being used in the field. The paper also presents field test results which confirmed that the acetic acid mixtures did not break zonal isolation (cement consumption was restrained to the perforated interval) and were able to generate 6- to 40-fold increases in the injectivity and productivity of the wells. Introduction Cement solubility in acids has been shown to be a problem, both in the field and by laboratory testing. Ref. 1 shows that HCl, HCl-HF, and citric acid have a strong detrimental effect on the cement, resulting in weight loss and compressive strength loss. Traditional views held that due to the formation of a protective skin, acid-cement reaction would be limited. However, severe zonal isolation problems have been observed, following HCl-HF treatments. The first approach to solve the problem was the development of acid-resistant cement. These blends use liquid latex that inhibits acid attack by coating cement particles and by reducing the permeability of the cement. Refs. 2 and 3 address the use of acid-resistant cement blends for primary cement and squeeze operations. This solution may be easily applied to new wells, in which the primary cement and squeeze jobs in front of the pay zones are composed of acid-resistant slurries.

In this work, PVDF composites containing 0.2% (m/m) of carbon nanotubes (MWCNTs), PVDF with 5.0% (m/m) of zinc oxide (ZnO), and composites containing both particles in the same contents in the matrix were melt processed in a mini-extruder machine with double screws, using the counter-rotation mode. Composites were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), dynamic-mechanical analysis (DMA), and contact angle tests (CA). The samples presented the predominance of the α phase, with an increased degree of crystallinity as well as an increase in dimensional stability by incorporating both fillers, showing a synergistic effect between these particles, as shown on FTIR, DSC, and XRD results. SEM images showed a good dispersion of high aspect ratio particles. In general, DMA and TGA analysis showed that composites had not decreased their thermal and mechanical performance when compared to neat PVDF. Results of CA analysis showed an increase in the hydrophobicity of the sample containing MWCNTs. Permeability tests were also performed using a differential pressure system, combining high temperature and pressure, obtaining permeability measures and time lag. This work presents an alternative of composite materials, suggesting its application in the internal pressure sheath layers of oil and gas flexible pipes. K E Y W O R D S composites, nanoparticles, nanotubes, oil and gas, thermoplastics 1 | INTRODUCTION Flexible pipes are transportation lines used to connect the wells, in the seabed, to the production units, transporting oil and gas fluids in offshore applications. These pipes possess a multilayer structure, with polymeric layers and helically wound metallic wires, designed to withstand tensile loads, high pressure, and temperature. 1-3 Different layer combinations are possible, depending on the intended service conditions. Still, in general, flexible risers present a typical configuration, with the following layers: interlocked carcass (metal),

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