Heat Seal Applications

It has been found that in the development of EVA polymers for heat seal applications by emulsion polymerization that the concentration of vinyl acetate and ethylene in the polymer is not solely responsible for its use as a heat seal adhesive (2). 

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Aqueous-based EVA polymer emulsions suited for the use in heat seal applications are produced at a comparatively low pressures process, less than 14 M Pa (2). 

J.J. Rabasco, C.L. Daniels, D.W. Horwat, M.S. Vratsanos, and R.H. Bott, Semi-crystalline ethylene vinyl acetate emulsion polymers for heat seal applications, US Patent 7189461, assigned to Air Products Polymers, L.P. (Allentown, PA), March 13,2007. 

Softening is apparent over a wide range, while the melt is strong and elastic. This gradual melting is beneficial in heat-sealing applications. 

Beilstein Handbook Reference) AI3-00515 BRN 1889288 CCRIS 6190 DCHP Dicyclohexyl 1,2-benzenedicarboxylate Dicyclohexyl phthalate EINECS 201-545-9 Ergoplast FDC HF 191 Howflex CP HSDB 5246 KP 201 NSC 6101 Phthalic acid, dicyclohexyl ester Unimoll 66. A plasticizer for nitrocellulose, ethylcellulose, chlorinated rubber, PVAc, PVC, and other polymers. Used in formulation of delayed tack heat sealable coatings, it Is a heat activated plasticizer for heat seal applications such as food wrappers/labels, pharmaceutical labels and other applications where delayed heat activated adhesive is required used in manufacture of printing ink formulations for paper, vinyl, textiles, and other substrates. Solid mp = 66° d = 1.383 insoluble in H2O, soluble in EtOH, Et20, CHCI3, Bayer AG Lancaster Synthesis Co. Miles Inc. Morflex Unitex. 

Beilstein Handbook Reference) Benzoflex S-552 Benzoic acid, tetraester with pentaerythritol 2,2-Bis((benzoyloxy)methyl)-1,3-propane-diol dibenzoate BRN 3513249 CCRIS 5971 EINECS 224-079-8 NSC 166502 Pentaerythritol tetrabenzoate 1,3-Propanediol, 2,2-bis( benzoyloxy)methyl)-, dibenz-oate Uniplex 552. Plasticizer for adhesives intended for heat seal applications Solid mp = 102-104°. Unitex. 

Solvent-borne systems still in use include polyurethanes for lamination of plastic films and EVA systems for some heat-seal applications such as lidding stock for plastic food containers. 

For vacuum seal and heat seal applications The liner of a double-sided tape or vinyl stickers To act as a non-stick surface... 

Because of its lower melting point, LDPE has been preferred over LLDPE for many heat-sealing applications. mLLDPE and plastomers are more composition-ally homogeneous than LLDPE. Shorter backbone sequence lengths for crystallization results in thinner crystalline lamellae and therefore lower melting points (Fig. 11). 

Table 4 further illustrates that the PVOH-protected and the cellulosic emulsion are both excellent bases for adhesives to bond to polyvinyl chloride. The PVOH-protected emulsion is usually chosen for wet laminations and the cellulosic emulsion for heat-seal applications. 

Uniplex 250 is a beat activated plasticizer used in heat seal applications such as food wrappers, food labels, pharmaceutical labels and other applications where a delayed heat activated adhesive is required. 

Uniplex 260 is especially recommended for use in heat seal applications. It is blended into polyvinyl acetate based-adhe-slves at a temperature below the melting point. 

Uniplex S62 Pentaerythritol Tetrabenzoata CAS No. 4196-86-5 Uniplex 552 is a solid plasticizer that can be formulated into adhesives intended for heat seal applications. It is approved by FDA under 21CFR 175.105. 

Flexible laminating, packaging, and converting - These markets include heat seal applications, paper/fihn and paper/foil laminators, and flexible packaging and laminators. 

While dual bar constant heat sealers are typically specified for thick film sealing or high sealing rate applications, they are also more costly. HEATSEAL can be used to explore the effect of film thickness on seal strength development to assess the proper equipment needs for a constant heat sealing application. For example, consider the comparison of single- and dual bar... 

Applications. Preformed bags are opened by the packager, filled with food product, and closed by adhesive, heat-sealing, clipping, stitching,... 

The rubbers may be vulcanised by conventional accelerated sulphur systems and also by peroxides. The vulcanisates are widely used in petrol hose and seal applications. Two limiting factors of the materials as rubbers are the tendency to harden in the presence of sulphur-bearing oils, particularly at elevated temperatures (presumably due to a form of vulcanisation), and the rather limited heat resistance. The latter may be improved somewhat by Judicious compounding to give vulcanisates that may be used up to 150°C. When for the above reasons nitrile rubbers are unsatisfactory it may be necessary to consider acrylic rubbers (Chapter 15), epichlorohydrin rubbers (Chapter 19) and in more extreme conditions fluororubbers (Chapter 13). 

The polymers are of interest as water-soluble packaging films for a wide variety of domestic and industrial materials. (Additional advantages of the poly(ethylene oxide)s are that they remain dry to the feel at high humidities and may be heat sealed.) The materials are also of use in a number of solution application such as textile sizes and thickening agents. As a water-soluble film they are competitive with poly(vinyl alcohol) whereas in their solution applications they meet competition from many longer established natural and synthetic water-soluble polymers. 

TPEs can be bonded to other materials by adhesive, heat bonding, electromagnetic filling, radio frequency, heat-sealing lamination, friction and spin welding, and ultrasonic welding. For TPUs, the most widely used techniques are radio frequencies, and ultrasonic and hot stamping. A few typical applications include football bladders, valves, and conveyer belts. 

The coating of polymer that we put on paperboard serves two purposes when we convert it into juice and milk cartons. It prevents the contents from leaking out and it acts as an adhesive so that we can heat-seal the coated paperboard to itself to form a container. Low density polyethylene is the polymer of choice for this application it has sufficient melt strength to... 

The main use for acrylates is in sealing applications where the improved heat stability over nitrile rubber is the benefit. Automotive transmission seals are probably the major use, other automotive applications include O-rings, hose, tubing, cable covering and spark plug boots. Also used in adhesive formulations. 

The above results suggest a potential for utilizing surface fluorinated plastics for modified atmosphere and vacuum packaging applications. If needed, the barrier properties can be improved further by vacuum metalization. Excellent adhesion was found for vacuum-deposited aluminum on this new fluorinated layer, achieving an adhesion index of 10 using the classical cross-hatch method. With this treatment method it was also possible to heat-seal PP or PE onto PET. 

The alternative to using a dish is to form the material into a bag and this so-called pouch or sachet method is often used for plastics films. The advantages are that a larger surface area is exposed, leaks through the wax seal are eliminated, and the conditions are more similar to packaging applications. It is less attractive for rubbers because they are not often used in that sort of packaging application and an alternative to heat sealing the pouch would be necessary. 

Hot tack strength is the ability of a heat-seal layer to hold together while molten, before the seal cools and sets up. This is a technically important property which is difficult to measure reproducibly in the laboratory. Owing to the reinforcing effect of ionic bonding on melt strength, ionomer sealing layers provide superior performance in a wide spectrum of applications. 

Heat sealing may be defined as the joining together of thermoplastic film by the application of heat and pressure. In practice, although it is a general term (known also as thermal sealing ) usually it refers to a technique in which either one or a pair of temperature-controlled elements is employed. 

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