Certain normal alpha olefins can be used to prepare homopolymers and copolymers other than polyethylene. Normal alpha olefin 1-butene can be polymerized to 1-polybutene (PB), a homopolymer that is ideal for many engineering applications because of its excellent long-term mechanical properties.

PB is extremely creep resistant and behaves similarly to a crosslinked plastic. It features a unique combination of unusually high tensile strength and good tear properties. PB shows no signs of cracking, crazing or fracturing when stressed below its short-time failure stress value for long periods of time. In addition, its tear strength increases rapidly as the tear rate escalates. PB’s benefits broaden the commercial applications for polymers.

Normal alpha olefins C₆, C₈, C₁₀, C₁₆, C₁₈, C_20-24 and C_24-28 are used for the production of copolymers. Using peresters as initiators, copolymers of maleic anhydride and normal alpha olefins can be formed.

The maleic copolymer made from normal alpha olefin C₁₈ is a product known as PA-18, which has been used successfully as a release agent in tapes and paper templates for PVC curtains, and in water-resistant sunscreen formulas.

The copolymers produced from other normal alpha olefin fractions are normally converted to acid amides, half esters or diesters for use as lube-oil additives and pour-point depressants. They are also effective curing agents for epoxy resins and act as unique thermoset resin compositions in liquid monoepoxides. In addition, normal alpha olefins C₆, C₈ and C₁₀ have been co- and terpolymerized with vinyl acetate and vinyl chloride.

Polyethylene Copolymers

With the evolution of increasingly sophisticated polyethylene technology, alpha olefins 4, 6 and 8 have become even more valuable comonomers for the production of a wide range of polyethylene resins.

High-density polyethylene (HDPE) is principally used for the manufacture of high-performance pipe, blow-molded household and industrial bottles, oil bottles, injection-molded food containers, consumer durables and disposable goods and film goods such as grocery sacks and merchandise bags. HDPE possesses high flex stiffness (flexural modulus) but low environmental stress cracking resistance (ESCR). Lowering the melt index (high melt viscosity) can help to alleviate the low ESCR, but the processibility of the polymer suffers, due to lower flow rates. The addition of Chevron Phillips Chemical's alpha olefins 4, 6 or 8 as a comonomer increases the resulting polymer short chain branching, thereby improving the flow properties while greatly increasing the ESCR.

In addition, HDPE polymers made with alpha olefins 6 or 8 as a comonomer have much higher ESCR than those made with 1-butene. For a given polymerization process at a polymer density of 0.950 g/cc and melt index ranges of 0.2 to 0.3 g/10 minutes, 1-butene copolymers had ESCR values of 50 to 310 hours, and 1-hexene copolymers exhibited ESCR values of 800 to more than 1,000 hours. Copolymerizing with Chevron Phillips Chemical's alpha olefin 8 rather than 1-hexene produces polymers with even better ESCR values.

Linear low-density polyethylene (LLDPE) is made by incorporating an even higher level of comonomer (1-butene, 1-hexene or 1-octene) into the product to reduce the density of the resulting polyethylene. Conventional Ziegler-Natta catalysts as well as more recent metallocene technologies are being used today to produce LLDPE. LLDPE provides significantly greater stiffness than low-density polyethylene (LDPE) polymers, which are typically produced in high-pressure processes. Because the melt index of LLDPE can be raised to values much higher than that of LDPE (while maintaining equivalent or superior physical properties), processing cycle times can be reduced. In addition, many products made with LLDPE can be significantly downgauged to save on raw material costs.

For the greatest possible strength and tear resistance, the density can be reduced even further using emerging metallocene technologies to produce what is referred to as very low-density polyethylene (VLDPE). Among other benefits, VLDPE has a higher heat-seal temperature than LDPE, yet provides equivalent seal strength.

Regardless of the application, Chevron Phillips Chemical's 1-hexene performs exceptionally well under the most stringent polymerization conditions. This is particularly important with the emergence of sophisticated metallocene technology for the production of LLDPE and VLDPE where high purity comonomers are critically important to maintain high catalyst activity and resulting product performance.