Strength of paper

Starches used to increase the internal strength of paper as measured by tensile, edge cmsh resistance, Mullen burst, and Scott bond strength are added at the wet end, whereas starch used to increase surface strength as measured by pick and resistance to Hnting are added at the size press. 

Some amino resins are used as additives to modify the properties of other materials. For example, a small amount of amino resin added to textile fabric imparts the familiar wash-and-wear quaUties to shirts and dresses. Automobile tires are strengthened by amino resins which improve the adhesion of mbber to tire cord (qv). A racing sailboat may have a better chance to win because the sails of Dacron polyester have been treated with an amino resin (1). Amino resins can improve the strength of paper even when it is wet. Molding compounds based on amino resins are used for parts of electrical devices, botde and jar caps, molded plastic dinnerware, and buttons. 

These polyol-stabilized alkan olamine titanate solutions are used ia a method to improve the wet strength of paper (115,118). The addition of 1—2... 

Cox, H.L., The elasticity and strength of paper and other fibrous materials, liritish Journal of Applied Physics, 1952, 3, 52. 

In the literature, various other types of resin preparation procedures are described, e.g. yielding uron structures [20-22] or triazinone rings in the resins [23,24]. The last ones are formed by the reaction of urea and an excess of formaldehyde under basic conditions in the presence of ammonia or an amine, respectively. These resins are used to enhance the wet strength of paper. 

Virtually all epoxy resins are made with starting materials based on epichlorohydrin, principally by reaction with bisphenol A. It is also used for the preparation of resins to increase the wet strength of paper. Both epichlorohydrin and glycidol are used in the manufacture of pharmaceuticals. 

Bursting strength, of paper, 18 100-101 Burton process, 18 648 Busheling scrap, 21 408-409 Bushveld Igneous Complex, 19 604 Business form inks, 14 321 Business R D expenditures, 21 612. 

Melamine resins also are used for the production of decorative laminates. The amino resins are able to modify textiles like cotton and rayon by imparting crease resistance, stiffness, shrinkage control, fire retardance and water repellency. They are also used to improve the wet strength, rub resistance and bursting strength of paper. 

Figure 4.5 Relationship between tensile strength of paper (expressed as a breaking length) and the number of fibres which fail during the test.

Two types of models have been applied to the mechanical strength of paper. The first assumes paper to be a continuous network of hydrogen bonds with no other type of bond contributing to its mechanical properties, and the second describes its mechanical strength in terms of a combination of fibre strength and fibre-to-fibre bonds. 

Adsorption might be expected to create additional fibre-to-fibre bonds and/or to strengthen existing bonds, but there is evidence that the increase in tensile strength of paper is caused primarily by an increase in the bond strength per unit of optically bonded area, rather than by an increase in the extent of the relative bonded area itself (Figure 7.13). 

Aziridine is an intermediate and monomer in the preparation of cationic polymers, such as polyaziridine (polyethyleneimine). These polymers are used to improve wet strength of paper, in fuel-oil and lubricant refining, as flocculating agents and in protective coatings, in textile finishing and for adhesives, polymer stabilizers, and surfactants (Lewis, 1993 Scherr et al., 1995). 

The strength of paper is much less when the paper is wet because the water tends to pull the hydrophilic paper fibers apart. The width of the pores is 1-12 x. The macroscopic structure cannot be expressed in mathematically accurate figures. 

Accordingly, a complete book preservation program should consider (a) complete deacidification (b) improving fold endurance, tear and tensile strength of paper and (c) inhibiting oxidation. 

Cationic oat starch was used to improve the dry strength of paper handsheets and found to be comparable to wheat starch in functionality.14 Oat starch might possibly be a replacement for rice starch in pharmaceutical applications.19 Oat flour has been used in adhesive preparations.19... 

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