Effect of consolidation on the flexural creep behaviour of all-polypropylene composite

Abstract

Abstract. The long-term viscoelastic behaviour of self-reinforced polypropylene composites (SRPPC) was studied by short-term flexural creep tests at different temperatures. As reinforcement a fabric, woven from highly stretched split PP yarns, whereas as matrix materials α and β crystal forms of isotactic PP homopolymer and random copolymer (with ethylene) were selected and used. The composite sheets were produced by film-stacking method and compression moulded at different processing temperatures (5, 20, 35°C above the melting temperatures of the matrices) keeping the holding time and pressure constant. The manufactured specimens were subjected to isothermal creep tests at different temperatures ranging from -20 to 80°C under an applied load. The time-temperature superposition principle was verified for the creep data. An Arrhenius type relationship described the shift data obtained from the creep tests. It was found, that with improving consolidation (increasing processing temperature) the creep compliance decreased and good correlation was found between creep compliance and density/peel strength.

Injection moulded all-polypropylene composites composed of polypropylene fibre and polypropylene based thermoplastic elastomer

“…Their combination opens a new horizon for the industrial production of all-polymer composites. Nowadays, all-polymer and self-reinforced materials/composites [7] can be produced with narrow processing window by hot compaction (single-component self-reinforced materials (SRM)) [8][9][10][11], consolidation of coextruded tapes [12][13][14] and filmstacking methods (multi-component SRM) [15][16][17][18][19][20][21]. In addition, all of the above processing methods yield sheet-like (pre)products which can be shaped thereafter by thermoforming.…”

Long-term creep behavior of self-reinforced PET composites

“…The addition of flame retardant increased the modulus reduction value to 65%, while its highest magnitude obtained for mPET was 85%. As compared to the modulus reductions of srPP ranging between 71.5 and 87% [31][32][33] and those of natural fiber composites (between 65 and 75%) [23][24][25][26][27][28], the studied srrPET composites exhibited superior creep resistance.…”

“…Both the William-Landel-Ferry (WLF) and Arrhenius equations were used to obtain the shift factors for polymer composites in previous studies. For srPP, the Arrhenius equation was found to generate better fitting results as compared to the data produced by the WLF equation [31][32][33]. The WLF equation was found empirically to describe the frequency dependence of glass transition temperature in amorphous polymers.…”

“…Due to the aging of the polypropylene matrix with time, TTSP successfully predicted the long-term creep response of polymer composites at ambient temperature, but was found to be unsuitable at higher temperatures [30]. The long-term creep behavior of srPP composites was studied by Izer and Bárány [31] and KargerKocsis and covorkers [32,33] using TTSP, who concluded that it could be satisfactorily described by an Arrhenius-type relationship. However, in spite of the recent progress in investigating the creep behavior of fiber-reinforced composites, limited results were obtained for srPCs (especially for srPET-based materials).…”

Estimating the creep strain to failure of PP at different load levels based on short term tests and Weibull characterization

“…Supposing the polymeric material is of linear viscoelastic nature and/or exhibits simple thermo-rheological behavior the time-temperature superposition principle can be used to construct the long term creep curve called master-curve from short term creep measurements performed at different temperatures and a given load level [1][2][3][4][5]. In general the Williams-Landel-Ferry (WLF) or the Arrhenius equation or some combination of them is applied to determining the shift factor necessary for constructing the long term master curve [6][7][8][9][10]. Power law type approximations like Nutting's or Findley's ones [6,8,11] or simple rheological models such as Standard Solid or Burgers or their generalized forms [1][2][3][4][5]12] can give a simple solution to extrapolate the measured data or to describe the master curve mathematically.…”