On increasing wet-web strength with adhesive polymers

TAPPI Journal ◽  
2020 ◽  
Vol 19 (2) ◽  
pp. 63-67
Author(s):  
ROBERT PELTON ◽  
DONG YANG ◽  
EMIL GUSTAFSSON
Keyword(s):  
Joint Strength ◽  
Critical Issue ◽  
Pulp Fiber ◽  
Paper Machine ◽  
Aqueous Processing ◽  
Tissue Engineering Scaffolds ◽  
Ongoing Research ◽  
Green Strength ◽  
Physics Literature ◽  
Web Strength

Fiber-fiber adhesion, called “bonding” in the old paper physics literature, is a critical component of the overall strength of dry paper. With freshly formed very wet pulp fiber webs, all evidence suggests there are no fiber-fiber crossings with significant adhesive joint strength. With water removal, a point will be reached where fiber-fiber adhesion starts to contribute to the overall wet-web strength. The literature reveals very few examples of polymers that increase fiber-fiber joint strength in freshly formed webs. Here, we summarize the literature and explain why it is so difficult to promote fiber-fiber wet adhesion with polymers. Nevertheless, ongoing research in areas as diverse as tissue engineering scaffolds and biomimetic adhe-sives gives clues to future developments. Advances in paper machine engineering have lessened the importance of wet-web strength. By contrast, a critical issue in many of the evolving nanocellulose technologies is the strength of objects first formed by aqueous processing, the green strength—the strength of wet bodies before drying. For exam-ple, 3-D printed nanocellulose objects and ultralow density cellulosic aerogels can be destroyed by capillary forces during drying. There is a need for adhesives that strengthen freshly formed, wet lignocellulosic joints.

Technical Challenges for Commercial Supersonic Propulsion

2010 ◽  
Author(s):  
Louis A. Povinelli
Keyword(s):  
Critical Issue ◽  
Light Weight ◽  
Ongoing Research ◽  
Research Activities ◽  
Time Period ◽  
Main Emphasis ◽  
Exhaust Plumes ◽  
Technical Issues ◽  
Specific Thrust ◽  
Technical Challenges

The NASA Supersonics Project is focused on overcoming the major technical challenges associated with the development of commercial supersonic flight. The NASA Project has identified a number of technical issues that must be overcome in order for this mode of flight to become practical. In particular, the propulsion technologies must meet all of the current subsonic engine noise and emissions regulations at takeoff and landing, as well as acceptable particulate and water emissions at high altitude. High specific thrust will be required, and the effect of shocks associated with the engine inlets, nacelles and exhaust plumes must be minimized in order to achieve a low boom signature. High temperature, light weight materials are vital to achieving acceptable long range durability and efficiency. The main emphasis of this paper will be concerned with the improvements required for the propulsion system in order to achieve the goals established over the 2015 to 2030 time period. The need to successfully integrate the engine with the vehicle remains a critical issue that needs to be accomplished. This presentation presents the ongoing research activities toward achieving these goals.

scholarly journals Small Pilot System for the Manufacture of in Situ Precipitated Calcium Carbonate in the Presence of Pulp Fibers

2021 ◽  
pp. 118-123
Author(s):  
Klaus Dölle ◽  
Bardhyl Bajrami
Keyword(s):  
Calcium Carbonate ◽  
Calcium Hydroxide ◽  
Pilot Scale ◽  
Production Costs ◽  
Pulp Fiber ◽  
Paper Machine ◽  
Precipitated Calcium Carbonate ◽  
Paper Properties ◽  
Eucalyptus Pulp

Paper fillers materials are less expensive than fiber, allowing reduced production costs and improvement of paper properties. A small pilot scale in-situ laboratory calcium carbonate filler precipitation unit was developed and designed with the objective to provide enough pulp fiber containing in-situ precipitated calcium carbonate for a small 12-inch (304 mm) wide laboratory paper machine. The in-situ precipitation system requires the reactants calcium hydroxide and carbon dioxide and was tested with a eucalyptus pulp fiber pulp suspension. The final precipitated in-situ filler content achieved was 38.2%, 55.5% and 66.6% based on initial eucalyptus pulp fiber content. The precipitation time from an initial pH of 12.77, 12.76 and 11.98 to an final pH of 7.29, 7.55, and 7.28 for the 3 kg, 6kg, and 9 kg of calcium hydroxide reactant addition was 45 minutes for the 3 kg and 9 kg calcium hydroxide addition and 40 min. for the 6 kg calcium hydroxide addition.

Wet-peel: a tool for comparing wet-strength resins

2018 ◽  
Vol 33 (4) ◽  
pp. 632-646 ◽  
Author(s):  
Dong Yang ◽  
John-Louis DiFlavio ◽  
Emil Gustafsson ◽  
Robert Pelton
Keyword(s):  
Fiber Surface ◽  
Testing Procedure ◽  
Regenerated Cellulose ◽  
Pulp Fiber ◽  
Layer By Layer ◽  
Paper Strength ◽  
Wet Strength ◽  
Polyelectrolyte Complexes ◽  
Cellulose Membranes ◽  
Web Strength

Abstract We propose that a testing procedure we call wet-peel significantly augments conventional wet paper testing when comparing wet-strength resin efficacy or the influence wood pulp fiber surface treatments on wet paper strength. A thin layer of wet-strength resin is sandwiched between a pair of thin, wet regenerated cellulose membranes to form a laminate, which is a physical model for fiber-fiber joints in paper. In the wet-peel method, the ninety-degree wet-delamination force gives a direct measure of adhesion in the wet cellulose-cellulose joint. Wet-peel measurements offer: 1) comparisons of wet-strength polymers at the same content of polymer in the laminate joint without the influences of varying fines contents, formation or paper density; 2) measurements of both the wet-strength of cured, dried joints, and the strength of never-dried joints (i. e. analogous to wet-web strength); 3) demonstrations of the influence of fiber surface chemistry modifications including oxidation and the presence of firmly bound polymers; and, 4) the evaluation of more exotic joint structures including layer-by-layer assemblies, microgels and colloidal polyelectrolyte complexes.

The effect of microfibrillated cellulose on the wet-web strength of paper

TAPPI Journal ◽  
2021 ◽  
Vol 20 (1) ◽  
pp. 61-68
Author(s):  
JONATHAN PHIPPS ◽  
TOM LARSON ◽  
MARK PARADIS ◽  
DIANA TANASE
Keyword(s):  
Filler Content ◽  
Critical Factor ◽  
Laboratory Method ◽  
Microfibrillated Cellulose ◽  
Paper Machine ◽  
Paper Machines ◽  
The Press ◽  
Commercial Paper ◽  
Web Strength ◽  
Positive Effect

The wet-web strength of paper immediately after the press section of a paper machine is a critical factor in determining machine runnability. However, it is difficult to determine at commercial scale, because the web has to be broken and production interrupted in order to obtain a sample for measurement. The use of microfibrillated cellulose (MFC) is believed to increase wet-web strength, as it has allowed filler level increases of 10% or more on many commercial paper machines. In this paper, we describe a laboratory method for estimating the effect of MFC on wet sheet strength after pressing, as well as actual measurements of wet-web strength from a pilot paper machine trial. These experiments have demonstrated the positive effect of MFC. At solids contents in the range typically observed after pressing, sheets with MFC at fixed filler content are significantly stronger, but also wetter, than those without it. When the use of MFC is combined with a typical increase in filler content, the wet web remains slightly stronger, but also becomes drier than the reference condition. These results are compatible with the theory put forward by van de Ven that wet-web strength is mainly a result of friction between entangled fibers, and they also suggest that the presence of MFC increases this friction.

Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

1992 ◽  
Vol 50 (1) ◽  
pp. 158-159
Author(s):  
Warren J. Moberly ◽  
Daniel B. Miracle ◽  
S. Krishnamurthy
Keyword(s):  
Thermal Stresses ◽  
Load Transfer ◽  
Coefficient Of Thermal Expansion ◽  
Hot Isostatic Pressing ◽  
Matrix Composites ◽  
Ongoing Research ◽  
Aerospace Applications ◽  
Sic Fiber ◽  
The Matrix ◽  
Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

Novel tissue engineering scaffolds as wound dressings loaded with Alkannins/Shikonins as active ingredients

2019 ◽  
Author(s):  
AS Arampatzis ◽  
K Theodoridis ◽  
E Aggelidou ◽  
KN Kontogiannopoulos ◽  
I Tsivintzelis ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Wound Dressings ◽  
Active Ingredients ◽  
Tissue Engineering Scaffolds

HYDROXYAPATITE, ALGINATE, AND CHITOSAN FOR BONE SCAFFOLDS: SPECTROSCOPY STUDY

2016 ◽  
Vol 19 (2) ◽  
pp. 93-100
Author(s):  
Lalita El Milla
Keyword(s):  
Tissue Engineering ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Functional Groups ◽  
Bone Growth ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Tissue Engineering Scaffolds ◽  
Hydroxyapatite Powder ◽  
Materials Used

Scaffolds is three dimensional structure that serves as a framework for bone growth. Natural materials are often used in synthesis of bone tissue engineering scaffolds with respect to compliance with the content of the human body. Among the materials used to make scafffold was hydroxyapatite, alginate and chitosan. Hydroxyapatite powder obtained by mixing phosphoric acid and calcium hydroxide, alginate powders extracted from brown algae and chitosan powder acetylated from crab. The purpose of this study was to examine the functional groups of hydroxyapatite, alginate and chitosan. The method used in this study was laboratory experimental using Fourier Transform Infrared (FTIR) spectroscopy for hydroxyapatite, alginate and chitosan powders. The results indicated the presence of functional groups PO43-, O-H and CO32- in hydroxyapatite. In alginate there were O-H, C=O, COOH and C-O-C functional groups, whereas in chitosan there were O-H, N-H, C=O, C-N, and C-O-C. It was concluded that the third material containing functional groups as found in humans that correspond to the scaffolds material in bone tissue engineering.

Environmental benefits of magnesium hydroxide-based peroxide bleaching of mechanical pulp – mill results

TAPPI Journal ◽  
2013 ◽  
Vol 12 (6) ◽  
pp. 9-15 ◽  
Author(s):  
TOMI HIETANEN ◽  
JUHA TAMPER ◽  
KAJ BACKFOLK
Keyword(s):  
Sodium Hydroxide ◽  
Magnesium Hydroxide ◽  
Oxygen Demand ◽  
Pulp Mill ◽  
Transition Metal Ions ◽  
Environmental Benefits ◽  
Raw Material ◽  
Paper Machine ◽  
High Brightness ◽  
Peroxide Bleaching

The use of a new, technical, high-purity magnesium hydroxide-based peroxide bleaching additive was evaluated in full mill-scale trial runs on two target brightness levels. Trial runs were conducted at a Finnish paper mill using Norwegian spruce (Picea abies) as the raw material in a conventional pressurized groundwood process, which includes a high-consistency peroxide bleaching stage. On high brightness grades, the use of sodium-based additives cause high environmental load from the peroxide bleaching stage. One proposed solution to this is to replace all or part of the sodium hydroxide with a weaker alkali, such as magnesium hydroxide. The replacement of traditional bleaching additives was carried out stepwise, ranging from 0% to 100%. Sodium silicate was dosed in proportion to sodium hydroxide, but with a minimum dose of 0.5% by weight on dry pulp. The environmental effluent load from bleaching of both low and high brightness pulps was significantly reduced. We observed a 35% to 48% reduction in total organic carbon (TOC), 37% to 40% reduction in chemical oxygen demand (COD), and 34% to 60% reduction in biological oxygen demand (BOD7) in the bleaching effluent. At the same time, the target brightness was attained with all replacement ratios. No interference from transition metal ions in the process was observed. The paper quality and paper machine runnability remained good during the trial. These benefits, in addition to the possibility of increasing production capacity, encourage the implementation of the magnesium hydroxide-based bleaching concept.

Microstructure simulation of early paper forming using immersed boundary methods

TAPPI Journal ◽  
2011 ◽  
Vol 11 (11) ◽  
pp. 23-30 ◽  
Author(s):  
ANDREAS MARK ◽  
ERIK SVENNING ◽  
ROBERT RUNDQVIST ◽  
FREDRIK EDELVIK ◽  
ERIK GLATT ◽  
...  
Keyword(s):  
Early Paper ◽  
Contact Model ◽  
Fiber Suspension ◽  
Beam Equation ◽  
Immersed Boundary ◽  
Paper Machine ◽  
Immersed Boundary Methods ◽  
Element Discretization ◽  
Microstructure Simulation ◽  
Boundary Methods

Paper forming is the first step in the paper machine where a fiber suspension leaves the headbox and flows through a forming fabric. Complex physical phenomena occur as the paper forms, during which fibers, fillers, fines, and chemicals added to the suspension interact. Understanding this process is important for the development of improved paper products because the configuration of the fibers during this step greatly influences the final paper quality. Because the effective paper properties depend on the microstructure of the fiber web, a continuum model is inadequate to explain the process and the properties of each fiber need to be accounted for in simulations. This study describes a new framework for microstructure simulation of early paper forming. The simulation framework includes a Navier-Stokes solver and immersed boundary methods to resolve the flow around the fibers. The fibers were modeled with a finite element discretization of the Euler-Bernoulli beam equation in a co-rotational formulation. The contact model is based on a penalty method and includes friction and elastic and inelastic collisions. We validated the fiber model and the contact model against demanding test cases from the literature, with excellent results. The fluid-structure interaction in the model was examined by simulating an elastic beam oscillating in a cross flow. We also simulated early paper formation to demonstrate the potential of the proposed framework.

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