Intrinsic viscosity rubbers

In comparison with a PVC having an intrinsic viscosity close to that of the homopolymer present in the raw product, compounds based on some reaction raw products, containing 9% rubber, show quite similar thermal stability and weathering resistance they are characterized further by better resilience and better fluidity. 

According to the statistical-mechanical theory of rubber elasticity, it is possible to obtain the temperature coefficient of the unperturbed dimensions, d InsjdT, from measurements of elastic moduli as a function of temperature for lightly cross-linked amorphous networks [Volken-stein and Ptitsyn (258 ) Flory, Hoeve and Ciferri (103a)]. This possibility, which rests on the reasonable assumption that the chains in undiluted amorphous polymer have essentially their unperturbed mean dimensions [see Flory (5)j, has been realized experimentally for polyethylene, polyisobutylene, natural rubber and poly(dimethylsiloxane) [Ciferri, Hoeve and Flory (66") and Ciferri (66 )] and the results have been confirmed by observations of intrinsic viscosities in athermal (but not theta ) solvents for polyethylene and poly(dimethylsiloxane). In all these cases, the derivative d In sjdT is no greater than about 10-3 per degree, and is actually positive for natural rubber and for the siloxane polymer. 

Evaluating the Polymer. The intrinsic viscosity (IV) of the polymer was determined at 25° C. with solutions in benzene or toluene containing 0.1 gram/liter polymer and calculated with the equation IV = (In rjTei)/C. In many cases some gel formation made I V determination for the whole polymer impracticable. Hoekstra viscosities of a number of polymers were measured at 100° C. with the Hoekstra (Wallace) plastometer (42). This instrument provides bulk viscosity data for rubbers on a scale 0 (low viscosity) to 100 (high viscosity). 

A model series consisting of six ethylene-propylene block copolymers (PP/EPR) has been investigated. While the flowability of their matrix (MFR 45 dgmin x), the rubber content (about 23 wt %) and the amount of C2 in the E/P rubber have been fixed, their intrinsic viscosity (IV) has been varied systematically from 1.7 to 6 dg 1 1 (which corresponds roughly to Mw from 150 to 1000 kg mol x). A detailed description of the non-nucleated materials and their performance has been published elsewhere [168]. 

T = 65°C AIBN, 0.13% suspending agent, variable amounts depending on amount of rubber present, range 0.6-1.5% monomer conversion = 70% water/(rubber + monomer) = 1.4 and intrinsic viscosity determined in cyclohexanone at 30°C and expressed... 

With vinyl chloride, the decrease in intrinsic viscosity of the homopolymer that forms during the reaction with an increase in the initial amount of rubber was far more marked with EPDM elastomers than with saturated ethylene-propylene copolymer (Figure 1). This suggests that EPDM elastomers have a high radical activity, even with small amounts of ENB. 

Figures 2 and 3 depict the variations in the amount of rubber participating in the grafting reaction and in the intrinsic viscosity of the still free elastomer...

Silicone resins and rubbers ctre cross-linked polymers with branched polymer chains containing M (monofunctional), D (difunctional), T (trifunctional), and Q (tetrafunctional) units. Slightly branched polymers made from D, T, and Q structures have lower bulk viscosity and intrinsic viscosity than linear polymers of the same average molecular weight. 

Figure 6-1. Influence of goodness of solvent, as measured by the solubility parameter, 6i, of the solvent, on the intrinsic viscosity. [17], of dissolved natural rubber and on the volume fraction, 02, of the cross-linked natural rubber polymer in aliphatic hydrocarbons, (O), long-chain esters, ( ), and long-chain ketones, (O). After data from G. M. Bristow and W. F. Watson. The solubility parameter is given in the traditional physical units.

INTRINSIC VISCOSITIES OF NATURAL RUBBER FRACTIONS AND OF WHOLE RUBBER... 

Sample No. Intrinsic viscosity Fraction of whole rubber Xi Contribution to [n]m... 

A method to overcome this is Benoit s universal calibration plot (63) of log [ti] M against V, where [ti] is intrinsic viscosity. However, this method needs the constants from the Mark-Howink [ti]M relationships for the rubber samples to be analyzed in the SEC solvents before the SEC analyses. However, a literature survey showed that few constants for rubbers are available, as shown in Table 5. Another method is to use the Q factor (64), which is defined as the ratio of the extended chain length between polystyrene and rubber samples. This method is valid only for vinyl polymers and is empirically crude (6). 

For nitrogen dioxide (NO ), the exposure of samples was usually realised under a pressure of 15 mm Fig during 30 hours at 308 K. However, in the case of Nylon 66 and butyl rubber, NO pressure was lowered to 1 mm Hg during 30 minutes. Polyisoprene and polybutadiene were exposed to NO during 5 minutes under a pressure of 1 mm Hg. As a light source (A, > 290 nm), a mercury lamp was used. The intrinsic viscosity of polymer solutions was measured before and after exposure of samples in the chosen conditions. The high concentration of NO in these situations was used to confirm that certain effects could be observed for a reasonable time. 

Fig. 3.7 Intrinsic viscosity-molecular weight correlation for rubber after degradation in thin films (-"vw. ) and on mastication at 55 (-), 120 (-), and 140°C (----) [54].

Comparable results have also been reported for EPDM rubbers [28, 29]. The intrinsic viscosity decrease with mastication temperature (Fig. 3.9) shows three different regions the first (for 20-65°C), where the intrinsic... 

The rubber particle size of heterophasic polypropylene can be described by molecular weight. The molecular weight of an ethylene propylene copolymer can be described by its intrinsic viscosity, as measured by the XS fraction. The p of an ethylene propylene copolymer is generally determined at 135°C using decaline as a solvent, see Fig. 2.21. 

Rubber particle size characterized by intrinsic viscosity influences the flow behavior, shrinkage, and mechanics of heterophasic polypropylene. At equal rubber concentrations, a high IV yields a greater decrease in the MFI when compared to low IV materials. The influence on increased impact properties is also higher. 

Keywords Paul Flory Herman Mark Carl Marvel Gaussian chain Excluded volume Rubber Polymer solutions Molecular weight distributions Intrinsic viscosity Herman Staudinger... 

Thurston GB, Peterlin A (1967) Influence of finite number of chain segments, hydrodynamic interaction, and internal viscosity on intrinsic birefringence and viscosity of polymer solutions in an oscillating laminar flow field. J Chem Phys 46(12) 4881 4884 Treloar LRG (1958) The physics of rubber elasticity. Oxford University Press, London Tsenoglou C (2001) Non-Newtonian rheology of entangled polymer solutions and melts. Macromolecules 34 2148-2155... 

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