Ethylene Copolymers: Techno Brief

Ethylene copolymers and terpolymers are widely used in the manufacturing of hot-melts adhesives and sealants because of their mechanical cohesion and adhesive properties. Formulators can adjust their formulation in order to fulfill technical requirements of many applications requiring long or short open time, resistance to elevated or cold temperatures and many other performances.

Learn all the key facts about copolymers and terpolymers (ethylene vinyl acetates & ethylene acrylic esters), their key features and application techniques used in the adhesives & sealants industry.

Ethylene Copolymers in Hot melt applications

Ethylene Copolymers are leading materials for formulating hot-melts (pressure sensitive and non pressure sensitive) in applications such as packaging, bookbinding, woodbinding and many other industrial applications.

Hot-melts pressure sensitive adhesives

This success is due to the high technical versatilty of Ethylene copolymer based formulations which can fullfil highly demanding technical requirements covering both long open time and fast setting time, resistance to very low temperatures (-40°C) or very high temperatures ( +80°C) with very high thermal and UV stability for water-white formulations.

Key parameters for choosing the right base polymer for your formulations are:
  1. Choice of Copolymer
  2. Content of Copolymer
  3. Melt Flow Index (MFI)

1. Choice of Copolymer

Copolymer selection will depend on final properties to be achieved.

EVA products are the right choice for general purpose hot-melts for packaging and bookbinding applications or to reach high temperature resistance in transportation or assembly. High VA content EVA would also be an interesting polymer for formulating Hot Melt Pressure Sensitive (HMPSA) in applications such as bottle labelling or sanitary.

Ethylene / acrylic ester copolymers polymers have a lower glass transition temperature than EVA (Tg) and provide a better adhesion to difficult substrates as well as better performances at very low temperatures. These polymers will help formulators to achieve very high performances in deep-freeze applications or when a high level of adhesion is required ( varnished carboard, plastic to paper bonding...). Ethylene / acrylic ester copolymers based hot-melts also provide a very high resistance to degradation and low odor when formulated with the right tackifiers and preservatives.

For the most challenging bonding (UV varnished substrates or demanding ageing test) the "Ethylene - Acrylic esters - Maleic Anhydride" or "Etylene - Vinyl Acetate - Maleic Anhydride" terpolymers will be the ultimate choice for achieving very high performances.

2. Content of Copolymer

The Copolymer content is a key parameter to adjust Adhesion / Cohesion balance in the hot-melt formulation as well as the performances at low or high temperature. This copolymer content also impacts strongly on polymer cristalinity with a high impact on the mechanical performances of the formulated hot-melt.

Crystallinity (%) = f(Comonomer % weight)
Figure 1 : Crystallinity (%) = f(Comonomer % weight)

3. Melt Flow Index (MFI)

This parameter influences the polymer's viscosity. The longer the polymer chain is, the higher the viscosity, and hence the lower the melt flow index. A lower MFI will result in greater mechanical strength, higher ring and ball softening point, and higher performances at high temperature (SAFT or PAFT tests), but will also increase hot-melt viscosity and strongly influence open time and setting time.

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