Effects of molecular weight and molecular weight distribution on creep properties of polypropylene homopolymer

Abstract

The molecular weights of the industrial‐grade isotactic polypropylene (i‐PP) homopolymers samples were determined by the melt‐state rheological method and effects of molecular weight and molecular weight distribution on solid and melt state creep properties were investigated in detail. The melt‐state creep test results showed that the creep resistance of the samples increased by Mw due to the increased chain entanglements, while variations in the polydispersity index (PDI) values did not cause a considerable change in the creep strain values. Moreover, the solid‐state creep test results showed that creep strain values increased by Mw and PDI due to the decreasing amount of crystalline structure in the polymer. The results also showed that the amount of crystalline segment was more effective than chain entanglements that were caused by long polymer chains on the creep resistance of the polymers. Modeling the solid‐state viscoelastic structure of the samples by the Burger model revealed that the weight of the viscous strain in the total creep strain increased with Mw and PDI, which meant that the differences in the creep strain values of the samples would be more pronounced at extended periods of time.

Tailoring compatibilization potential of maleic anhydride‐grafted polypropylene by sequential rheochemical processing of polypropylene and polyamide 66 blends

“…The M n and M w of PP and PP-g-MAH are provided by the manufacturer. Kurt and Kasgoz [48] have experimentally measured the molecular weight of PP, which is the same material used in this study, using melt rheology, and reported that the molecular weight agreed with that provided by the manufacturer. Detailed characterization of grafted polymer is beyond our current research scope; therefore, we accept and report the manufacturer's value of PP-g-MAH molecular weight without further verification.…”

Effects of Different Concentrations of Arsine on the Synthesis and Final Properties of Polypropylene

“…In Figure 5 , the effect of this complex of radicals O-O-AsH-TiCl 4 -MgCl 2 is shown on the beginning of the degradation of PP, which consists of the abstraction of hydrogen in the PP-virgin, generating a stable tertiary radical, which, when reacting with a molecule O 2 , will produce a Peroxy-PP-virgin radical, which extracts hydrogen from a neighboring virgin-PP chain, thereby forming the virgin-PP-Hydroperoxide. The latter, after a homolytic rupture, will give rise to the Alkoxy-PP-Virgin radical [ 53 , 54 , 55 , 56 ]. The radical complex of O-O-ash-tiCl 4 -MgCl 2, after the abstraction of hydrogen, forms the peroxy complex H-O-O-AsH-TiCl 4 -MgCl 2 that, by hemolysis, forms the radical O-AsH-TiCl 4 -MgCl 2 .…”

Characterising the linear viscoelastic behaviour of an injection moulding grade polypropylene polymer

“…In order to apply the theoretical and computational methods, the creep and recovery responses should be within the linear viscoelastic regime. The linear viscoelastic creep and recovery responses of polypropylene composites have been experimentally studied in the past (Wang et al 2018;Kurt and Kasgoz 2021;Wu et al 2019;Lee et al 2004;Homkhiew et al 2013;Rosa et al 2018). However, the experimental studies vary on the testing methods, the equipment used, and the testing conditions.…”

“…Using the universal testing machines, uniaxial tension (Wu et al 2019;Lee et al 2004;Zhai et al 2018;Houshyar et al 2005;Drozdova et al 2009) and flexural (Militký and Jabbar 2015;Tiwari et al 2021) tests are made to study creep of polypropylene composites. Nano-indentation tests (Rosa et al 2018;Dian et al 2020), a dynamic oscillatory rheometer (Kurt and Kasgoz 2021) and a dynamic mechanical analyser (Wang et al 2018;Houshyar et al 2005) are used to study the effects of chemical modification on the mechanical performance of polypropylene. Similarly, the creep and recovery behaviours of the polypropylene composites are studied at different temperatures (Wang et al 2018;Banik et al 2007;Militký and Jabbar 2015).…”

“…They used the Burgers model for fitting the creep behaviour and a Weibull distribution function for the recovery. Kurt and Kasgoz (2021) have studied the effect of different molecular weight and their distributions on the creep behaviour of the same composite. They used the four parameters Burgers model to fit the creep.…”