Rate-Dependent Deformation Behavior of POSS-Filled and Plasticized Poly(vinyl chloride)

Abstract

Polymers are known to exhibit strong time-dependent mechanical behavior. In different temperatures or frequency regimes, the rate sensitivities of polymers change as various primary and secondary molecular mobility mechanisms are accessed. The incorporation of nanoparticles can potentially alter the molecular level structure of polymer, offering the opportunity to tailor the rate-dependent mechanical deformation and failure behavior of the polymer.This study focuses on polyhedral oligomeric silsesquioxanes (POSS) enhanced polymeric systems. POSS are hybrid organic-inorganic nano-scale molecules which consist of a silica cage with functional groups attached to the cage comers. Various binary and ternary polymer blends were produced by incorporating methacryl-POSS (C 56 I 88 , 28 Si8) (mPOSS) and dioctyl phthalate (DOP) into poly(vinyl chloride) (PVC) through melt blending. mPOSS was found to be miscible with PVC up to 15 wt% added. Both mPOSS and DOP plasticize PVC and reduce the atransition temperature. While mPOSS also reduces the secondary (0) transition temperatures in PVC, DOP was found to restrict the p-relaxation motions. The rate-dependent yield and postyield behavior was characterized in compression testing over a wide range of strain rate (10-4 /s to -4000/s). Due to the geometric and size distinctions between the two molecules, mPOSS and DOP have different influences on PVC local molecular motions, resulting in dissimilar mechanical behavior. A clear rate-dependent sensitivity transition in yield was observed in the pure PVC and PVC/mPOSS blends in the intermediate strain rate regime, which is attributed to the need for stress-assisted activation of / -motions at high strain rates. A transition in rate sensitivity was also identified in high DOP content compounds; this transition is due to the atransition.The potential of using POSS as a plasticizer for PVC was evaluated. Through the use of ternary compositions, the proportion of mPOSS in PVC was increased substantially. The T 8 of appropriately formulated ternary PVC/mPOSS/DOP compounds can be reduced to near room temperature, and these materials exhibit desirable ductile behavior.A constitutive model was used to predict the large deformation behavior of the PVC compounds. The two-process model is shown to capture the rate-sensitivity transitions in yield and the large deformation stress-strain behavior at low and high strain rates.

Rate dependence of poly(vinyl chloride), the effects of plasticizer and time–temperature superposition

“…20 wt% for PPVC-2 versus 60 wt% for PPVC-6), the β-transition stays in approximately the same position at the lowest rate (0.035 s −1 or 1 Hz): the amount of plasticizer does not shift the approximate location of the β-transition, even though the α-transition shifts to a lower temperature once plasticizer is added (as expected). Thus, the addition of more phenyl rings (or DINP), which is understood to create additional free volume in the material [7,31,32], does not affect the location of the β-transition. Hence, the β-transition must include more than just the behaviour of phenyl rings (i.e.…”

“…Alternatively, the increased strength in more rubbery or elastomeric polymers is accounted for by the change in molecular mobility during the glass transition (or α-transition). These transitions are usually seen within polymers at lower temperatures, but can be shifted in temperature by changes in strain rate, as the transition increases in temperature with increasing strain rate [5][6][7][8].…”

“…In many applications in which PVC is used, it is blended with a plasticizer based on a phthalate ester compound, such as diisononyl phthalate (DINP) [9]. The plasticizer is understood to increase the free volume in the polymer [7] and is used to enhance ductility and decrease properties such as the yield stress and stiffness. By changing the amount of plasticizer, the temperature and rate dependence are potentially changed, allowing one to better analyse and compare the mechanisms that govern these dependencies.…”

Novel thermally stable poly(vinyl chloride) composites for sulfate removal

“…Due to its interesting properties, various PVC composites have been prepared by dispersing double hydroxides [10], CaCO 3 [11,12], metal oxides [12], multiwall carbon nanotubes [13], C-60 [14], polyaniline, a conducting polymer [15], and silica [16,17]. Soong et al have reported the feasibility of using copper nanoparticledispersed PVC nanocomposites toward environmental remediation techniques, such as antifungal and bacteriostatic applications [18].…”

Predictive nonlinear constitutive relations in polymers through loss history

“…Further improvements on these models used a cooperative relaxation effect for segmental relaxation to reproduce new data on a range of polymers to high strain rates, while retaining an essentially thermodynamic approach (Richeton et al, 2005(Richeton et al, , 2006(Richeton et al, , 2007. Mulliken and Boyce (2006) demonstrated that the stress-strain response of PC and PMMA and PVC (Soong et al, 2006), can be linked back to their dynamic mechanical spectra. In particular, they show that the rate dependence of the aand b-transition loss peaks and storage modulus can be used to model the shifts in modulus and yield as a function of temperature and rate.…”