Much of a label’s effectiveness is due to its adhesive. An artful label designed to encourage a purchase or a heat-resistant label made for track and trace applications will fail miserably if it doesn’t stay where it belongs. Quality graphics and print, scratch or fade resistant coatings, and sturdy substrate materials are all important features that make up a good label. Just as important is the quality of the adhesive. The pressure sensitive labels that you see on products and cartons are made of several layers of specialized materials sandwiched together to create a label that looks good, identifies something, and lasts as long as it is needed. The components of a label are the Liner, Release Coat, Adhesive, Face Stock, and Topcoat. The release liner is the backing paper that makes up the web of a roll of labels. The release coat is a coating applied to the top surface of the liner which resists the adhesive so that the facestock and adhesive can be peeled away from the liner during label application. On top of the adhesive is the facestock, the paper, film, or other type of material on which printing is done. The facestock can be covered with a topcoat to provide physical protection from abrasion or to enhance some other property of the label. Pressure sensitive labels stick to a surface with light or moderate pressure from a label applicator, or by hand during manual application. Some factors to consider when selecting an adhesive include: Permanence of the label. Residue left on a product surface if the label is removed. Surface type label is applied to – paper, plastic, glass, metal. Texture of the surface the label is applied to – rough or smooth. Temperature when the label is applied and when it is stored. Environment in which the label must function. Labels can be permanent, removable or repositionable depending on the type of adhesive. Permanent label adhesives mean labels are difficult to remove without damage to the label and can leave residue on the surface of the product. Permanent label adhesives are usually the most cost-efficient and create the strongest bond. Labels with permanent adhesive are found on products that exist in difficult, wet, or harsh environments, or on labels that are used as a tamper-evident device. Removeable adhesives allow labels to be taken off the surface of a product and shouldn’t be used on products exposed to extreme temperatures or humidity. Removeable adhesives work well on items like coupon labels or promotional stickers because consumers can easily remove these labels without any damage or sticky residue. Repositional adhesives allow you to remove and reapply a label without ruining the lable, but there is a time constraint. Repositional adhesives can become more permanent after a while. Labels with this type of adhesive are useful if applying manually because the label can be removed if applied incorrectly and repositioned. Adhesives have varying properties that are suited to different applications. Important properties include the following: Tack – The immediate holding strength of the adhesive when it comes in contact with a surface. Low tack allows the label to be removed easily. High tack has stronger bonding to the container. Ultimate Adhesion – The maximum strength of bonding the label can achieve once fully adhered to a surface. The time it takes to achieve ultimate adhesion depends upon variables such as environmental conditions, the smoothness of the surface the label is applied to, and the viscousness of the adhesive. Resistance to Solvents – Adhesives have varying resistance to solvents such as to water, alcohol, petrochemicals, etc., so the environment must be considered. U.V. Resistance – Labels exposed to U.V. light for long periods might change color or weaken the bonding power of the adhesive. U.V. laminates or other coatings added to labels can improve U.V. resistance. Adherence to Curved Surfaces – This characteristic is called Mandrel. Adhesives with good Mandrel hold won’t lift at the edges. Cold Flow – An adhesive’s ability to bond to a container below normal temperatures is referred to as its cold flow. Some adhesives perform better when the label is applied to a surface in a cold environment. Application Temperature – Labels can lose adhesive properties if not applied at the correct temperature range. Adhesives lose their fluidity and can crystallize, losing effectiveness, so knowing the temperature range at which labels will be applied is important. Adhesives are made of either acrylic or rubber. Acrylic adhesives adhere to a wide spectrum of surfaces, including glass and metal and work well on surfaces that can become wet or be exposed to extreme termperatures. Rubber-based adhesives do not adhere to the wide variety of surfaces that acrylic adhesives can, but are a cost-effective type of adhesive that has some water resistance. Rubber adhesives are not recommended for use above 160F (70C) and can bond to substrates such as rubber, Teflon, silicone and plastics like polyethylene and polypropylene. Source:http://www.labelingnews.com/2018/01/pressure-sensitive-label-adhesives/