Análise crítica do processo de auditoria de sistema de gestão da qualidade no setor aeroespacial

A auditoria de sistema de gestão da qualidade é utilizada pelas organizações para melhorar o seu desempenho por meio de avaliações sistemáticas dos processos. Ao mesmo tempo, a atividade de auditoria vem sendo questionada quanto à sua capacidade de promover essa melhoria. Diante deste cenário, este artigo objetiva analisar fatores que afetam o processo de auditoria de certificação do sistema de gestão da qualidade, de modo a indicar oportunidades de melhoria das auditorias. A pesquisa é delimitada a auditorias no setor aeroespacial, que são orientadas pela NBR 15100. Foi realizada uma survey com auditores experientes nos anos de 2009 e 2010. São identificados fatores como comunicação, seleção da equipe, conhecimento do setor e os resultados mostram a existência de discrepâncias consideráveis entre o nível de importância e de aplicação desses fatores nas organizações auditadas.

导电炭黑在NBR中的应用研究

对导电炭黑（ＣＳＦ）作为ＮＢＲ的填料时，其填充量、硫化时间和增塑剂用量等因素对ＮＢＲ／ＣＳＦ混炼胶加工性能和硫化特性及硫化胶物理性能和电性能的影响进行了研究，并与乙炔炭黑（ＡＣＥＴ）进行了对比。结果表明，随着ＣＳＦ用量的增大，混炼胶的炭黑结合ＮＢＲ量、门尼粘度［ＭＬ（１＋４）１００℃］、屈服强度和拉伸强度均增大，扯断伸长率和挤出膨胀率降低，挤出物外观变优，焦烧时间和正硫化时间延长，硫化速度放慢，硫化胶的物理性能有所降低，导电性能提高；硫化胶体积电阻率随硫化时间延长和施加负荷的增大而降低，随温度升高和增塑剂

导电炭黑在NBR中的应用

用导电炭黑（ＣＳＦ）作填充剂，研究了它对ＮＢＲ混炼胶加工行为、硫化特性、硫化胶性能及导电性能的影响，并与填充乙炔炭黑（ＡＣＥＴ）的ＮＢＲ胶料性能进行了对比。结果表明，随着ＣＳＦ用量增加，炭黑结合ＮＢＲ含量、门尼粘度、屈服强度和拉伸强度均增加，而扯断伸长率及挤出物出口膨胀比降低，挤出物外观变优；随着ＣＳＦ用量增加，焦烧和正硫化延长，硫化速度及硫化胶强度有所下降，而导电性能变优。硫化胶体积电阻率随硫化时间延长及施加负荷增加而降低，随温度升高和增塑剂邻苯二甲酸二辛酯用量增加而升高。同时表明，ＮＢＲ／ＣＳＦ体系的结合ＮＢＲ含量、门尼粘度、混炼胶应力－应变性能及硫化胶导电性能等均高于ＮＢＲ／ＡＣＥＴ体系。

PE-MAH的合成及其对PE/NBR的增容作用

聚乙烯(PE)、马来酸酐(MAH)和过氧化二异丙苯(DCP)在溶液中反应,其产物经多次纯化和红外光谱分析证明,MAH以化学键连接到PE分子链上,接枝率达0.5MAH/100E,即相当于平均每个PE上接枝有10个MAH。用不同接枝率的聚乙烯接枝马来酸酐共聚物(PE-MAH)作为极性差别较大的PE和丁腈橡胶(NBR)的相容剂,分别研究其接枝率和用量对共混物的拉伸强度和低温冲击强度的影响,结果发现:PE-MAH增加了PE/NBR的相容性。低温脆断面的扫描电子显微镜观察清楚地反映出PE-MAH的增容作用。本文还提出了增容模型。

Enhancement of the properties of EPDM/NBR elastomers using nanoclay for seal applications

In this research, we have investigated the effects of addition of different percentages of nanoclay to the ethylene propylene diene monomer (EPDM) and nitrile butadiene rubber (NBR) on the characteristics of these rubbers as seal material. Properties such as tensile strength, modulus at different extensions, elongation at break, compressive set, hardness, and permeability and abrasion resistance are tested to assess the effect of addition of the nanoclay. Results indicate that addition of nanoclay at certain compositions could slightly reduce the strength of the rubber. However more stable modulus at different strains are provided, the hardness of the rubber is preserved and slightly enhanced, the permeability is reduced in both rubbers especially considerable decrease in EPDM is observed which is desirable in diminishing the effect of explosive decompression. At the same time the compression test shows that the nanoclay improves the performance of the rubbers under compression which is essential in seal application. The X-ray diffraction tests clarify that the dispersion of the nanoclay in the NBR samples is of high quality. In the EPDM samples, the dispersion is in need of improvement. POLYM. COMPOS., 30:1657-1667, 2009. © 2008 Society of Plastics Engineers.

Mapeamento de áreas queimadas usando séries temporais normalizadas derivadas de dados NBR-MODIS durante o período 2001-2014 no Parque Nacional das Emas

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Humanas, Departamento de Geografia, Programa de Pós-Graduação em Geografia, 2015.

A Novel Accelerator Combination for the Low Temperature Curing of Silica-Filled NBR Compounds

Zinc salts of ethyl, isopropyl, and butyl xanthates were prepared in the laboratory. The effect of these xanthates in combination with zinc diethyldithiocarbamate (ZDC) on the vulcanization of silica-filled NBR compounds has been studied at different temperatures. The cure times of these compounds were compared with that of NBR compounds containing tetramethylthiuram disulphide/dibenzthiazyl disulphide. The rubber compounds with the xanthates and ZDC were cured at various temperatures from 60 to 150°C. The sheets were molded and properties such as tensile strength, tear strength, crosslink density, elongation at break, compression set, abrasion resistance, flex resistance, heat buildup, etc. were evaluated. The properties showed that zinc salt of xanthate/ZDC combination has a positive synergistic effect on the cure rate and mechanical properties of NBR compounds.

Low Temperature Curing of NBR for Property Improvement

Zinc salts of ethyl, isopropyl, and butyl xanthates are prepared in the laboratory, and the effect of these xanthates with zinc diethyl dithiocarbamate (ZDC) on the vulcanization of HAF-filled nitrile butadiene rubber (NBR) compounds has been studied at different temperatures. The cure times of these compounds have been compared with that of NBR compounds containing TMTD/MBTS. The rubber compounds with the three xanthate accelerators and ZDC are cured at various temperatures from 60 to 150°C. The sheets are molded and properties such as tensile strength, tear strength, cross-link density, elongation at break, compression set, abrasion resistance, flex resistance, etc. have been evaluated. The properties show that zinc salt of the xanthate/ZDC accelerator system has a positive synergistic effect on the cure rate and mechanical properties of NBR compounds.

Studies on NBR/PVC Blends

Studies conducted on butadiene-acrylonitrile copolymer (NBR)/poly(vinyl chloride) (PVC) blends at different temperatures indicate that an optimum temperature exists for the formation of a particular blend. The mechanical properties of the blends confirm this observation. PVC stabilizer based on, magnesium oxide , zinc oxide, and stearic acid was found to be very useful in NBR/PVC blends.

Studies on Natural Rubber Bound Para -Phenylenediamine Antioxidants in NBR

Para-phenylenediamine (PD) was chemically attached to depolymerized natural rubber by a photochemical reaction . The rubber bound PD was characterized by TLC, 1H-NMR, IR, and TGA. The efficiency and permanence of the bound PD were compared with conventional antioxidants in NBR vulcanizates . The rubber bound PD was found to be less volatile and more resistant to water and oil extraction . The vulcanizates showed improved aging resistance in comparison to vulcanizates containing conventional antioxidants. The liquid rubber bound antioxidant reduces the amount of plasticizer required for compounding

Linseed Oil as a Multipurpose Ingredient in NBR Vulcanizate

ABSTRACT: Linseed oil is used in the dual roles of the plasticizer and the fatty acid component of the activator in nitrile rubber vulcanizates. The study shows that the substitution can substantially improve the mechanical properties in addition to other advantages such as increased cure rate, reduced leachability and reduced compound cost.

Studies on in situ precipitated silica filled rubber composites with special reference to NR, NBR and SBR

Precipitated silica is the most promising alternative for carbon black in tyre tread compounds due to its improved performance in terms of rolling resistance and wet grip.But its poor processability is a serious limitation to its commercial application.This thesis suggests a novel route for the incorporation of silica in rubbers,i.e.,precipitation of silica in rubber latex followed by coagulation of the latex to get rubber-silica maseterbatch.Composites with in situ precipitated silica showed improved processability and mechanical properties,when compared to conventional silica composites.

Curing studies of elastomer blends with special reference to NR/ NBR and NR/BR blends

There are a large number of commercial examples and property advantages of immiscible elastomer blends.73 Blends of natural rubber (NR) and polybutadiene (BR) have shown various advantages including heat stability, improved elasticity and abrasion resistance. Ethylene-propylene-diene-rubber (EPDM) blended with styrene-butadiene rubber (SBR) has shown improvements in ozone and chemical resistance with better compression set properties. Blends of EPDM and nitrile rubber (NBR) have been cited as a compromise for obtaining moderate oil and ozone resistance with improved low temperature properties. Neoprene (CR)/BR blends offer improved low temperature properties and abrasion resistance with better processing characteristics etc. However, in many of the commercial two-phase elastomer blends, segregation of the crosslinking agents, carbon black or antioxidants preferentially into one phase can result in failure to attain optimum properties. Soluble and insoluble compounding ingredients are found to be preferentially concentrated in one phase. The balance of optimum curing of both phases therefore presents a difficult problem. It has been the aim of this study to improve the performance of commercially important elastomer blends such as natural rubber (NR)/styrene-butadiene rubber (SBR) and natural rubber/polybutadiene rubber (BR) by industrially viable procedures

Studies on polymer blends with special reference to NBR/PVC and CR/PVC blends

The study is undertaken on PVC blends because of their all-round importance-One of the most prominent needs of PVC in application end-use is permanent plasticizationlo. Butadiene-acrylonitrile rubber (NBR) has been utilized as permanent plasticizer for PVC since the 1940s for wire and cable insulation, food contact, and pondliners used for oil containment23'24. Also plasticized PVC has been added to vulcanizable nitrile rubber, to yield improved ozone, thermal ageing, and chemical resistance resulting in applications including fuel hose covers, gaskets, conveyor belt covers, and printing roll covers. This blend is miscible in the range of 23 to 45 per cent acrylonitrile content in the butadiene-acrylqnitrile copolymerzs. The first phase of the study was directed towards modification blends. These blends, in addition to the polymers, require a host of additives like curatives for the NBR phase and stabilizers for the PVC phase26of the existing PVC blends, especially NBR/PVC. The second phase of the study was directed towards the development of novel PVC based blends. Chloroprene rubber (polychloroprene) (CR) is structurally similar to PVC and hence is likely to form successful blends with PVC32.