Adhesive-strengthening Additives

Additives to improve heat and/or moisture resistance are also known for epoxy adhesives. In a unique metal-ceramic bonding application, 100-150 mesh glass powder has been used to impart heat (arc) resistance to epoxy adhesives.Heat resistance is improved when the glass melts ( 448°C), flows, and adheres to the two substrates. Uretidinedione compounds, e.g., l,3-bis(3-isocyanato-4-methylphenyl)-2,4-uretidinedione (83), have been used in room temperature curing compositions to impart excellent heat and moisture resistance. Adhesive strength was not found to be affected even after heating in steam at 120°C and 2 atm. 

---

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. 

Additionally, some properties unique to both systems may result. The majority of homopolymer blends are immiscible with one another and often experience poor interfacial adhesion between the separate phases. Since block copolymers are covalently linked together, macroscopic incompatibility at the interface is minimized. The macroscopic incompatibility of a two-polymer blend may be eliminated by the addition of a block copolymer derived from the two systems. Hence, copolymers can be used to strengthen blends of immiscible polymers by serving as emulsifiers (7-9). 

Industrial separation membranes and ion-exchange resins can be made from chitin, especially for water purification. Chitin is also used industrially as an additive to thicken and stabilize foods and pharmaceuticals. Since it can be shaped into fibres, the textile industry has used chitin, especially for socks, as it is claimed that chitin fabrics are naturally antibacterial and antiodour (www.solstitch.net). Chitin also acts as a binder in dyes, fabrics and adhesives. Some processes to size and strengthen paper employ chitin. 

PVA adhesive is much more effective than other types because it has quick tack, has a remarkably good hold, and also somewhat strengthens paper to which it has been applied. An additional advantage is that it remains flexible. Spots of PVA inadvertently dabbed on to the wrong places should be wiped off immediately with a damp cloth because they are not readily soluble when dry. 

At 1200 °C and 1300 °C, incorporation of a reactive element in Fe3Al as an oxide dispersion is more effective in improving scale adhesion than a comparable elemental addition. It is proposed that this is due to strengthening of the substrate. 

Fibres of the above types (3 mm in length) and polypropylene fibres are introduced into the paste with the aim to provide mechanical stability to the structure of NAM. Because of the poor adhesion between lead and fibre particles, the role of mechanical strengthener of the NAM structure is not always very pronounced. Beyond any douht, however, fibre additions reduce substantially the waste during the pasting process and throughout the technological process of negative plate manufacture, which provides very important economical effect. 

---