In the copolymer of ethylene and high-grade α-olefin, when the content of high-grade α-olefin in the copolymer is relatively high, it is a semi-crystalline, low-modulus polymer. The copolymer of ethylene and advanced & alpha;-olefin plays a role of physical cross-linking through the crystallization of the polyethylene segment, thereby exhibiting the behavior of a thermoplastic elastomer.

Ethylene-octene copolymer is a rapidly developing category among ethylene and advanced α-olefin copolymers. Among them, the ethylene-octene copolymer developed by Dow Chemical Company is very representative.

When the limited geometry metallocene catalyst developed by Dow Company is applied to the copolymerization of ethylene-octene, with the increase of the comonomer content, the typical high modulus resin with high crystallinity and layered morphology can be prepared to low crystallinity. , Thermoplastic elastomers in random bundles. Bensason et al. proposed four areas of this structural change:

Dow's ethylene-octene copolymer products include polyolefin plastomer (POP) Affinity and polyolefin elastomer (POE) Engage.

 

Polyolefin plastomer (POP) Affinity performance characteristics and uses

Affinity is a metallocene polyolefin plastomer produced by Dow using INSITE technology. It is a copolymer of ethylene and octene. The mass fraction of octene is usually less than 20% and the density ranges from 0.875 to 0.935g/cm3.

The narrow molecular weight distribution of Affinity and the controlled introduction of limited long branches into the highly regular linear short branches of the polymer enable Affinity to exhibit good physical properties and processing properties.

Affinity has certain rubber characteristics than ordinary polyolefin plastics, but still has the strength and processability of plastics. Its optical and mechanical properties are excellent. Affinity is sensitive to the shear rate. The viscosity drops quickly at high shear rates and is easy to process. At the same time, its static shear viscosity is high, the melt strength is good, and the bubble stability is good during the film blowing process. Affinity has excellent heat-sealability and good compatibility with other resins, so it has good co-extrusion properties. Compared with ULDPE or EVA (containing 9% VA), Affinity has excellent puncture resistance, impact strength, hot tack strength and transparency, and its density is lower than EVA or PVC.

Most of Affinity products have been approved by the US FDA and are directly used in food packaging. In addition, Affinity is also used as a modifier for flat extruded flower films, sealing layers, cast films, blown films, HDPE and PP for diapers and sanitary products.

 

Performance characteristics and uses of polyolefin elastomer (POE) Engage

Engage is a metallocene polyolefin elastomer introduced by Dow Company using INSITE technology in 1994. This product is also an ethylene-octene copolymer. In recent years, it has also introduced an ethylene-butene copolymer.

The octene content of the comonomer in a typical Engage elastomer is above 20%. Compared with traditional polymers, its molecular weight distribution and short chain branch distribution are very narrow, so it has excellent physical and mechanical properties (high elasticity, high strength and high elongation) and good low temperature performance. Its molecular chain is saturated and contains relatively few tertiary carbon atoms, so it has excellent heat aging and UV resistance. The narrow molecular weight distribution makes the material difficult to flex during injection and extrusion processing.

INSITE technology can effectively control the introduction of long-chain branches into the polymer linear short-chain branching structure, thereby improving the processing rheological properties of the polymer, and also improving the transparency of the material. Through the design and control of the polymer structure, a series of materials with different density, Mooney viscosity, melt flow rate, tensile strength and hardness can be synthesized.

Compared with previous traditional elastic materials, Engage elastomer has many advantages. Compared with EPDM, it has the advantages of excellent weld line strength, good dispersion, high impact strength with equal addition, and excellent molding ability; it is comparable to SBR Compared with EVA, it has the advantages of good weather resistance, high transparency, low price and low density. Compared with EVA, EMA and EEA, it has the advantages of low density, high transparency, good toughness, and good flexibility. Compared with soft PVC In comparison, it has the characteristics of not requiring special equipment, low corrosion to equipment, good thermoforming, good plasticity, low density, good low-temperature brittleness and good economy.

As a plastic toughening agent, Engage elastomer has been well applied in the toughening modification of a variety of plastics. Not only can it toughen and modify the polyolefin plastics compatible with it, but also can be initiated by peroxide to effectively undergo graft reaction with monomers such as maleic anhydride and glycidyl acrylate. The resulting grafts are widely used To toughen engineering plastics such as nylon and polyester.