Comonomer Length Influence on the Structure and Mechanical Response of Metallocenic Polypropylenic Materials

Abstract

The structure and properties have been comprehensively studied for metallocene copolymers of propylene‐1‐hexene (CiPH) and propylene‐1‐octadecene (CiPOD). The comonomer content constitutes the most important factor affecting both structure and properties in these CiPH and CiPOD copolymers, although the length of the comonomer is also very important. Thus, a considerable decrease in crystallinity and an easier obtainment of mesomorphic‐like ordered entities are observed in the two kinds of copolymers as comonomer content increases. The variations in crystalline structure significantly influence the viscoelastic and mechanical behaviors of these CiPH and CiPOD copolymers. Consequently, the location and intensity of the different relaxation mechanisms as well as stiffness parameters (storage, Young's moduli, and microhardness) and deformation mechanism are strongly dependent upon composition.

Effect of Comonomer Content on the Behavior of Propylene Copolymer/Compatibilizer/Clay Nanocomposites

“…By using 1-octadecene as comonomer instead of 1-hexene, the shift in the thermal properties in the copolymer is larger due to changes in the free volume related with the larger size of the lateral chain. [6] The crystallinity drops is the main reason for changes in the mechanical properties of our samples under tensile conditions, as it is observed in Figure 2 and Table 2. Differences of two orders of magnitude were measured in the Young modulus: from 1 161 to 19 MPa, for PH and CP7.6OD, respectively.…”

“…[6] Values of 1, 0, À2, À12 and À33 8C were reported for HP, CP0.9H, CP2.9H, CP8.6H and CP7.6OD, respectively. [6] Therefore, copolymers with high comonomer content will present higher free volume and lower viscosity than the homopolymer, validating the above mentioned approach.…”

“…[6] Values of 1, 0, À2, À12 and À33 8C were reported for HP, CP0.9H, CP2.9H, CP8.6H and CP7.6OD, respectively. [6] Therefore, copolymers with high comonomer content will present higher free volume and lower viscosity than the homopolymer, validating the above mentioned approach. [54] Based on the above mentioned and despite that the three physic mechanisms (break up, peeling and diffusion) can be present simultaneously in our process, it is concluded that the diffusion mechanism represents properly our experimental findings: increasing the amount of short chain branching the viscosity decreases and the polymer diffusion toward the clay galleries is facilitated improving the intercalation state.…”

“…[1][2][3][4] In particular, the effect of lateral chains on the main properties of either polyethylenes or poly(propylene)s has been deeply studied allowing the relation between polymer topology and its final properties. [5][6][7][8][9] During the last 25 years the development of metallocene catalysts has improved this microstructural control allowing the synthesis of both polyolefins with tailored tacticities and new olefin copolymers with a random/uniform intermolecular comonomer incorporation and a narrow molecular weight distribution. [2,5,10] The effect of either lateral chains or short chain branching, on the main properties of polyolefins has been largely studied.…”

Influence of structure on the properties of polypropylene copolymers and terpolymers

“…Therefore it would be associated with the CH 2 -CH 3 branch formed by the introduction of 1-butene comonomer. This relaxation has also been observed in isotactic polypropylene copolymers [51] and on syndiotactic polypropylene [52] copolymers with long chain -olefin, also named …”