Otimização da dosagem de agente de resistência a húmido na fabricação de papel tissue

Tissue papers are products used for hygienic and sanitary purposes such as toilet paper, paper towel, napkin and facial tissue. Some of these papers have the characteristic of wet strength, which is defined as the strength of the paper after receiving a certain amount of water. In the manufacture of papers that demand a high wet strength value, the use of an additive for this purpose is extremely important and must be strictly controlled, always seeking to optimize the dosage to reduce costs. This work aimed to study the wet strength resin loading in tissue paper production and how the control of ionic charge in fiber suspension can help to optimize the dosage of wet strength resin. The ionic charge of the pulp suspension was kept between -10 to -21 μEq/mL, the zeta potential obtained was between -16.6 to -22.3 mV. Tensile strength values of paper sheets formed with and without the addition of the ionic charge control additive were compared. When it was controlled the ionic charge of the pulp suspension, it was possible to achieve greater values of wet tensile strength with lower dosage of wet strength resin.Papéis tissue são produtos utilizados para fins higiênicos e sanitários, tais como papel higiênico, papel toalha, guardanapo e lenço facial. Alguns desses papéis possuem a característica de resistência a húmido, que é definida como a resistência do papel após receber uma determinada quantidade de água. Na fabricação de papéis que demandam alto valor de resistência a húmido, o uso de um aditivo para essa finalidade é extremamente importante e deve ser rigorosamente controlado, sempre tentando otimizar a dosagem para reduzir custos. Este trabalho teve como objetivo estudar a carga de resina de resistência a húmido na produção de papel tissue e como o controle da carga iônica em suspensão de fibras pode ajudar a otimizar a dosagem da resina de resistência a húmido. A carga iônica da suspensão de fibras foi mantida entre -10 a -21 μEq / mL, o potencial zeta detetado ficou entre -16,6 a -22,3 mV. Foram comparados os valores das folhas de papel formadas com e sem adição do aditivo de controle de carga iônica. Quando foi controlada a carga iônica da suspensão de fibras, foi possível obter maiores valores de resistência à tração a húmido com menor dosagem de resina.Mestrado em Químic

A search for ultra-high-energy photons at the Pierre Auger Observatory exploiting air-shower universality

The Pierre Auger Observatory is the most sensitive detector to primary photons with energies above ∼0.2 EeV. It measures extensive air showers using a hybrid technique that combines a fluorescence detector (FD) with a ground array of particle detectors (SD). The signatures of a photon-induced air shower are a larger atmospheric depth at the shower maximum (X$_{max}$) and a steeper lateral distribution function, along with a lower number of muons with respect to the bulk of hadron-induced background. Using observables measured by the FD and SD, three photon searches in different energy bands are performed. In particular, between threshold energies of 1-10 EeV, a new analysis technique has been developed by combining the FD-based measurement of X$_{max}$ with the SD signal through a parameter related to its muon content, derived from the universality of the air showers. This technique has led to a better photon/hadron separation and, consequently, to a higher search sensitivity, resulting in a tighter upper limit than before. The outcome of this new analysis is presented here, along with previous results in the energy ranges below 1 EeV and above 10 EeV. From the data collected by the Pierre Auger Observatory in about 15 years of operation, the most stringent constraints on the fraction of photons in the cosmic flux are set over almost three decades in energy

Study on multi-ELVES in the Pierre Auger Observatory

Since 2013, the four sites of the Fluorescence Detector (FD) of the Pierre Auger Observatory record ELVES with a dedicated trigger. These UV light emissions are correlated to distant lightning strikes. The length of recorded traces has been increased from 100 μs (2013), to 300 μs (2014-16), to 900 μs (2017-present), to progressively extend the observation of the light emission towards the vertical of the causative lightning and beyond. A large fraction of the observed events shows double ELVES within the time window, and, in some cases, even more complex structures are observed. The nature of the multi-ELVES is not completely understood but may be related to the different types of lightning in which they are originated. For example, it is known that Narrow Bipolar Events can produce double ELVES, and Energetic In-cloud Pulses, occurring between the main negative and upper positive charge layer of clouds, can induce double and even quadruple ELVES in the ionosphere. This report shows the seasonal and daily dependence of the time gap, amplitude ratio, and correlation between the pulse widths of the peaks in a sample of 1000+ multi-ELVES events recorded during the period 2014-20. The events have been compared with data from other satellite and ground-based sensing devices to study the correlation of their properties with lightning observables such as altitude and polarity