First, preparation
Cyanoacetate and formaldehyde are polycondensed in alkaline medium.
In the structure of the product, there is a strong electron-withdrawing cyano group and an ester group, and it is easy to perform anionic condensation under water absorption or alkali catalysis.
Second, the preparation
Pure alpha-cyanoacrylates are colorless, transparent, unstable liquids with very low viscosity. Alpha-cyanoacrylates are prone to anionic polymerization, and the storage stability of monomers is closely related to moisture. Monomers with a water content of more than 0.5% are very unstable. Alkaline stabilizers such as SO2, copper acetate, P2O5, CO2 must be added. In the case of p-methylsulfonic acid and the like, α-cyanoacrylate may also undergo radical polymerization, and it is necessary to add a polymerization inhibitor, hydroquinone.
The viscosity of α-cyanoacrylate is very small, and it is easy to lose as an adhesive. It is necessary to add a macromolecular compound as a thickener such as organic glass molding powder (5-10%); in order to increase the toughness of α-cyanoacrylate, A toughening agent such as tricresyl phosphate, dibutyl phthalate is added. DOP and so on.
Third, the curing reaction and performance
Curing by anionic polymerization, the polymerization of water or basic substance adsorbed on the surface of the adherend is rapidly completed at room temperature.
Alpha-cyanoacrylic acid ester (temporary adhesive) is currently the shortest adhesive at room temperature, its ester groups may be methyl ester, ethyl ester, propyl ester. The methyl ester has the fastest curing speed and heat resistance, but the adhesive layer is brittle. As the carbon chain grows, the flexibility of the adhesive layer is good. Currently, α-cyanoacrylate is mainly used.
The α-cyanoacrylates are isolated from the vapor as much as possible during storage and stored in PE containers. However, PE has good air permeability, which makes it easy for water vapor to penetrate and reduce the quality. Its storage period is only 3-6 months.
Physical properties and bonding strength of different ester-based α-cyanoacrylates
Normal align=center> R-
Normal align=center> Mn
Normal align=center> Boiling point
Normal align=center> Density
Normal align=center> Surface Tension
Normal align=center> Adhesive Strength (Steel)
Normal align=center> Stretch
Normal align=center> Shear ( MPa )
Normal align=center>
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Welcome, '+oauth_user+' | Bind account | Logout Login' : 'Welcome to function scrollx(p) { var d = document, dd = d.documentElement, db = d.body, w = window, o = d. getElementById(p.id), ie6 = /msie 6/i.test(navigator.userAgent), style, timer; if (o) { cssPub = ";position:"+(pf&&!ie6?'fixed':'absolute ')+";"+(pt!=undefined?'top:'+p.t+'px;':'bottom:0;'); if (pr != undefined && pl == undefined) { o.style .cssText += cssPub + ('right:'+p.r+'px;'); } else { o.style.cssText += cssPub + ('margin-left:'+p.l+'px;'); } if(pf&&ie6){ cssTop = ';top:expression(documentElement.scrollTop +'+(pt==undefined?dd.clientHeight-o.offsetHeight:pt)+'+ "px" );'; cssRight = '; Right:expression(documentElement.scrollright + '+(pr==undefined?dd.clientWidth-o.offsetWidth:pr)+' + "px")'; if (pr != undefined && pl == undefined) { o. style.cssText += cssRight + cssTop; } else { o.style.cssText += cssTop; } dd.style.cssText +=';background-image: url(about:blank);background-attachment:fixed;'; }else{ if(!pf){ w.onresiz e = w.onscroll = function() { clearInterval( timer); timer = setInterval(function(){ // double select dd.scrollTop is 0 in order to fix xhtml resolution in chrome var st = (dd.scrollTop||db. scrollTop),c; c = st - o.offsetTop + (pt!=undefined?pt:(w.innerHeight||dd.clientHeight)-o.offsetHeight); if(c!=0){ o.style.top = o.offsetTop + Math.ceil(Math.abs(c)/10)*(cLip balms are most often used to moisturize and protect the Lips. They often contain SPF protection.
Lip Balm or lip salve is a wax-like substance applied topically to the lips of the mouth to moisturize and relieve chapped or dry lips
The primary purpose of lip balm is to provide an occlusive layer on the lip surface to seal moisture in lips and protect them from external exposure. Dry air, cold temperatures, and wind all have a drying effect on skin by drawing moisture away from the body. Lips are particularly vulnerable because the skin is so thin, and thus they are often the first to present signs of dryness. Occlusive materials like waxes and petrolum prevent moisture loss and maintain lip comfort while flavorants, colorants, sunscreens, and various medicaments can provide additional, specific benefits.
Lip balm can be applied where a finger is used to apply it to the lips, or in a Lipstick-style tube from which it can be applied directly.
Lip balm was first marketed in the 1880s , though its origins are commonly traced to earwax which was used as lip balm prior to that.
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