Structure Development in Melt Spinning Syndiotactic Polypropylene and Comparison to Isotactic Polypropylene

Abstract

A basic investigation of the development of crystallization and orientation during the melt spinning of syndiotactic and isotactic polypropylene is described. Both polymers were melt spun through ambient air or into ice water at various draw-down ratios and melt temperatures. The melt spun ®laments were characterized by wide angle x-ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). The polymorphic behavior of isotactic polypropylene during melt spinning is well known. The ®laments melt spun through ambient air exhibit the monoclinic a-form while the ®laments melt spun into ice water form a smectic structure at low draw-down ratios. Syndiotactic polypropylene also exhibited polymorphic behavior during melt spinning. Disordered Form I with (t 2 g 2 ) 2 helices was found at low spinline stresses and Form III with all trans chain conformation was found at high spinline stresses. The criterion of the spinline stress for this transition was found to be about 6±9 MPa for all samples of various molecular weights, melt temperatures and cooling rates. Syndiotactic polypropylene crystallized much more slowly than isotactic polypropylene and did not exhibit a smectic mesomorphism under ice-water quenched conditions. The melt spun ®laments of syndiotactic polypropylene exhibited lower birefringences and amorphous orientations but higher crystalline orientations than those of isotactic polypropylene, compared at the same spinline stresses.

Melt spinning of synthetic polymeric filaments

“…Structure developments in melt spinning have been researched extensively, although most work has been carried out on homopolymers (Lu and Spruiell, 1987;Jinan C, et al , 1989;Choi and White, 2000). Rwei (2000) experimented with blends of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).…”

Structure development in melt spinning of poly(ethylene‐co‐octene) filaments with various comonomer contents

“…52,53 D. Choi and White 54 found that if lower tacticity isotactic polypropylene is melt spun, the range of conditions of forming the mesomorphic structure is increased. Introducing comonomer or disordering into polyolefins clearly leads to broader regions of formation of less-ordered structures.…”

“…Many authors [52][53][54] have found that quenching isotactic polypropylene leads to a mesomorphic form in which 3/1 helices are disordered. This also happens in the melt spinning of fibers.…”

Numerical analysis of jerry can strength under static and dynamic loads

“…У сучасній промисловості широкого використання набув такий матеріал, як поліетилен високої густини [1]. Він використовується для виробництва паливних баків, резервуарів для зберігання й транспортування рідин, великої кількості тари різного призначення.…”