The NETMELT PUR vary, Concentrol’s polyurethane hotmelt adhesives

The NETMELT PUR vary, Concentrol’s polyurethane hotmelt adhesives

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NETMELT is Concentrol’s vary of hotmelt adhesives used for gluing totally different substrates, porous or non-porous, akin to: paper, cardboard, wooden, cork, plastic, materials, and so on.

They are introduced in pellets, blocks or pillows, relying on the reference.

On account of their versatility, they can be utilized effectively in a variety of sectors: Meals, Graphic Arts, Instances/Packaging, Electronics, Wooden, Textile, Automotive, and so on.

The use of any such adhesive affords the patron the potential of excessive work charges and glorious efficiency. Concentrol additionally affords customized formulated merchandise to satisfy your particular wants.

Most references adjust to FDA customary 175.105.

 

NETMELT PUR

NETMELT PUR hotmelt adhesives are thermoplastic polyurethane (PU) prepolymers with a 100% solids content material, so they don’t include solvents. They are additionally known as structural, chemically hardening or curable adhesives, as they require a chemical response. On this case, polymerization attributable to water from ambient humidity, which acts as a series extender. This response is what produces the ultimate adhesion pressure between two surfaces, wherein the polyurethane hotmelt has been used for his or her union.

When the prepolymer reacts with the ambient humidity or that of the substrate itself, this prepolymer will increase its molecular weight because of the crosslinking of the chains throughout polymerization. A last thermosetting adhesive product is obtained, which doesn’t soften. Therefore, as soon as totally cured, they often have good resistance to temperature and chemical merchandise.

PUR Hotmelts are stable merchandise at room temperature, chemically terminated in reactive isocyanate teams (-N=C=O), synthesized, like all polyurethanes, from polyester or polyether polyols or their mixtures, with polyisocyanates. On account of security necessities, the ensuing prepolymers should be very low in free isocyanates, which is the fraction that continues to be unreacted on the finish of the prepolymerization course of. Monomeric isocyanates are poisonous. Even at low concentrations, they’ll harm the respiratory organs, eyes, and pores and skin, and might trigger allergic sensitization, amongst different results.

Our vary of NETMELT PUR melts by the motion of warmth and stays within the type of a kind of fluid liquid. On this state, they’re utilized to all kinds of substrates. Once they settle down, they solidify, producing an preliminary power similar to that of a standard non-reactive scorching soften adhesive. It then turns into, after chain extension with ambient humidity, a superb bond power on helps the place conventional HM, EVA-based or polyolefin, are utterly ineffective.

 

Variations between PUR scorching soften adhesive and traditional EVA or Polyolefin based mostly

Though each merchandise are utilized in the identical method utilizing melting tools:

  • the recent soften adhesive is heated till it’s in liquid type,
  • is utilized to the supplies to be joined,
  • these supplies are put in touch the place the adhesive has beforehand been deposited,
  • cools whereas the glue joint is pressed, they’re totally different, though with some related properties.

Subsequent, attribute facets of the standard adhesive and the reactive adhesive are in contrast:

Typical hotmelt Reactive hotmelt
Utility temperature >150ºC 90 – 140ºC → decrease vitality prices 
Reactivity None With humidity → last bond power could take time
Thermal resistance Restricted as a result of it all the time maintains its melting level, the environmental warmth can have an effect on the glue. Wonderful (doesn’t soften)
Adhesion to substrates Good however extra restricted Vast number of supplies
Price Not very excessive Excessive, however much less is required. Ambient warmth can have an effect on bonding
(VOC) Risky Natural Compounds Sure Sure
Normal facets Limitation in keeping with substrates, scorching soften all the time. Cheaper value. Big selection of supplies, thermosetting bond after curing.

 

Excellent properties of NETMELT PUR reactive polyurethane hotmelt adhesives

  • 100% solids, don’t include solvents.
  • It affords a extremely versatile chemistry, since it may be adjusted amongst others: viscosity, chemical affinity, open time, hardness, flexibility, preliminary adhesion, last adhesion, and so on.
  • Relevant on a variety of substrates (very diversified properties for very particular functions). Graphic arts, Instances/Packaging, Electronics, Wooden, Textile, Automotive, and so on.
  • It permits the becoming a member of of all kinds of merchandise which can be usually troublesome to hitch, together with non-porous supplies, plastics, and metals.
  • Achieves a high-quality bond with supplies which can be totally different from one another.
  • Wonderful properties at excessive and low temperatures.
  • Good resistance to chemical compounds as soon as totally cured.
  • Efficient for indoor and outside functions.

 

Composition 

Hotmelt PURs are made by reacting polyol blends with extra diisocyanate. The response of the alcohol group (-OH) with the isocyanate group (-NCO) produces an urethane group, as could be seen within the following determine.

The prepolymer obtained is packaged scorching and sealed beneath an inert and vacuum environment, to keep away from any contact with ambient humidity.

Containing an extra of diisocyanate, the product can’t totally react to polyurethane and stays a hot-melt product. In distinction, totally polymerized polyurethanes (after software and curing) are stable merchandise and are labeled as plastics.

When formulating an HMPUR, the selection of parts is necessary and governs the ultimate properties. Every of the uncooked supplies could be adjusted appropriately to acquire the required shelf life, open time, and early and late strengths.

The essential properties are obtained with using a wide range of correctly formulated polyols, isocyanates and components. Polyols are used to fluctuate the open time, the setting time or preliminary adhesion, the viscosity and the power to moist uniformly on the assist.

Typical polyols used are polyesters, which could be crystalline or amorphous; and polyethers based mostly on ethylene and propylene oxides; though the latter are much less used within the adhesive sector. One or one other sort of polyol (polyether or polyester) or mixtures of those is chosen to generate last results and properties of the fabric to be formulated.

Under is a desk with these traits: 

Properties Affect of polyester Affect of polyether
Hydrolysis resistance +
Resistance to microorganisms +
Solvent resistance +
R-UV resistance +
Conduct at low temperatures +
Conduct at excessive temperatures +
Simple processed +
Resilience +

The most generally used polyisocyanate for the manufacture of HMPUR is diphenylmethane diisocyanate, generally abbreviated MDI. It exists in three totally different isomeric varieties, 2,2′-MDI, 2,4′-MDI and 4,4′-MDI, the latter being, nevertheless, essentially the most used and certified as “pure MDI” or just MDI. Commercially, we don’t discover the pure product, mixtures of two isomers and even modified (liquid and polymeric).

Components could be added to those formulations to change and enhance sure properties. These could be catalysts or hardeners to speed up curing, moisture scavengers to increase shelf life, thickeners and thixotropic brokers to change viscosity, or fillers to regulate bodily properties, plasticizers, tackifying brokers, flame retardants, UV markers, antioxidants. , UV stabilizers and pigments, amongst others.

 

Polymerization mechanism – curing 

As soon as the HMPUR is utilized and cooled to solidity, the curing response with ambient moisture begins. Absorption of water from the environment ends in the formation of carbamic acid which, being unstable, decomposes, varieties an amine, and releases carbon dioxide (CO₂) as a gasoline. This amine can react with a free isocyanate group, and in flip type an urea group.

The response ends when all of the out there isocyanate teams are consumed, acquiring a really steady compound.

One consequence of the polymerization response is that the urethane prepolymer, which was initially linear, crosslinks in a three-dimensional style because of crosslinking of the polymer chains. As well as, because of these reactions, the polymer will increase significantly in weight throughout curing, bettering the adhesion pressure. Therefore, if the adhesive is formulated appropriately for a particular software, it can present a transparent improve in last resistance; kind of flexibility, each at high and low temperatures; and nice resistance to hydrolysis, warmth, and solvents.

Though there are lots of benefits to moisture curing scorching soften adhesives, the moisture content material of the substrates should be excessive sufficient to attain full polymerization.

Typically the humidity is excessive sufficient within the atmosphere, however low within the assist. This makes it troublesome for moisture to penetrate the system, because of the distinction in response velocity of the floor going through the surface and the one going through the within. An outer layer of polymerized PU is shaped that doesn’t enable water vapor to enter, and, due to this fact, there are areas with out the finished response with much less adhesion pressure.

As mentioned above, carbon dioxide bubbles type, which may additionally undermine the bond power of the adhesive. Extra frequent if the adhesive layer is simply too thick.

The polymerization – curing time relies on:

  • The quantity of adhesive utilized. A skinny layer cures sooner.
  • Environmental circumstances: humid environments favor sooner curing.
  • Kind of substrate: the extra porous it’s, the higher anchorage and the shorter the curing time.
  • The use of catalysts or hardeners significantly accelerates curing.


Within the determine above you may see the 2 phases by which the HMPUR system achieves the bond power, the primary stage by a bodily mechanism (solidification) and the second stage by a chemical mechanism (polymerization). (a) signifies the preliminary resistance, (b) refers back to the open time and (c) signifies the setting time. 

 

Utility sectors

The essential software sectors are:

Binding. The benefits of binding with PUR glue is that it may be achieved on virtually any sort of paper, laborious cowl or smooth cowl, resists excessive temperatures, and affords higher flexibility and adhesion than different conventional glues, which supply a much less malleable product. This technique affords books of higher sturdiness and high quality on the lowest doable manufacturing value and with out being sewn.

Automotive. Though totally different automobile producers have totally different adhesion necessities, the fundamental content material is identical and the demand from the automobile market additionally factors within the path of utilizing PUR scorching soften adhesives. Quick, environment friendly, high-performance adhesives are wanted to match software strategies and meet the demanding necessities of contemporary car meeting. They are used within the union of various substrates: plastics akin to ABS, PC…; metallic, textile and wooden; for dashboards, armrests, flooring, ceiling, seats, door panels, gutters, carpets, upholstery, inside trim, and so on.

Joinery, carpentry and furnishings making. PUR adhesives are a superb alternative for carpentry and different wooden functions. They present the excessive power wanted to carry supplies collectively and eradicate the necessity for screws and nails to assemble wooden furnishings. This contains floor laminating, furnishings edging and profile cladding.

Casing. The use of HMPUR is particularly advisable for packaging to point out content material and completely clear plastic instances (PET, PVC, PP, PE…), in addition to hybrids, for making a union with glorious resistance and nice transparency, avoiding the formation of bubbles contained in the joint and thus bettering its visible look.

It’s also used within the electronics, textile, building and meals sectors.

 

The NETMELT PUR vary

The essential references at the moment out there and the totally different sectors of software are proven.

APPLICATION  REFERENCE
Binding  NETMELT PUR EN-2231 CER HV 

NETMELT PUR EN-2231 CER 

NETMELT PUR EN-2231 CE-1 

NETMELT PUR EN-2231 CSR 

Automotive NETMELT PUR MP-2270 C 

NETMELT PUR MP-2220 M 

NETMELT PUR MP-2231 M 

NETMELT PUR MP-2267 C 

NETMELT PUR MP-2040 C 

NETMELT PUR AA-2290 C 

Textile  NETMELT PUR PT-2216 C 

NETMELT PUR PT-3515 C NETMELT PUR TX-2512 C 

Wooden  NETMELT PUR CTF-1570 M

NETMELT PUR FP-2227 C

NETMELT PUR LM-2250 C 

Casing (PP, PVC, PET…)  NETMELT PUR PP-2210 M

NETMELT PUR PP-2260 C 

Beauty NETMELT PUR PP-2260 C 
Cork (meals business)  NETMELT PUR FS-2045 C NETMELT PUR FS-3016 C 

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L’entrada The NETMELT PUR vary, Concentrol’s polyurethane hotmelt adhesives ha aparegut primer a Concentrol.

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