Die swell and melt fracture: Effects of molecular weight distribution

1974 ◽  
Vol 13 (2) ◽  
pp. 223-227 ◽  
Author(s):  
J. Vlachopoulos
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Die Swell ◽  
Melt Fracture

Melt fracture of two broad molecular weight distribution high-density polyethylenes

2011 ◽  
Vol 52 (4) ◽  
pp. 795-804 ◽  
Author(s):  
Mahmoud Ansari ◽  
Savvas G. Hatzikiriakos ◽  
Ashish M. Sukhadia ◽  
David C. Rohlfing
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
High Density ◽  
Melt Fracture ◽  
Broad Molecular Weight Distribution

Compound Processability and Molecular Weight Distribution of SBR

1976 ◽  
Vol 49 (2) ◽  
pp. 291-302 ◽  
Author(s):  
W. Mills ◽  
F. Giurco
Keyword(s):  
Molecular Weight ◽  
Carbon Black ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Mixing Time ◽  
Die Swell ◽  
Similar Information ◽  
Unit Work ◽  
Normal Production ◽  
Mooney Viscosity

Abstract Nonuniformities in the mixing and extrusion behavior of nominally standard grades of emulsion- and solution-polymerized oil-extended SBR are associated with variations in molecular weight distribution but are not reflected by Mooney viscosity. The variations in the samples studied were representative of normal production material. The solution-polymerized polymers characteristically exhibit wider variations in compound die swell and have generally more rapid dispersion of carbon black than comparable emulsion-polymerized polymers. This is true, regardless of whether BIT or t′ point is considered as a measure of carbon black dispersibility. Generally, increasing polydispersity increases compound die swell and retards the rate of carbon-black dispersion. Utilization of unit work instead of mixing time as a measure for torque rheometer processability gives similar information on carbon-black dispersibility. However, unit work is preferred because of the promise it holds for scaleup and interlaboratory correlation. Delta Mooney values, and to a lesser extent peak Mooney torque, provide a useful basis for predicting the mixing and extrusion behavior of oil-extended SBR. The torque rheometer t′ point recently proposed as an index for carbonblack dispersibility is also useful for predicting compound die swell.

Measurement of Molecular Weight Distribution of SBR and Prediction of Rubber Processability

1976 ◽  
Vol 49 (2) ◽  
pp. 278-290 ◽  
Author(s):  
B. R. Smith
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Preparation Method ◽  
Peak Height ◽  
Peak Height Ratio ◽  
Die Swell ◽  
Simple Relationship ◽  
Height Ratio ◽  
Carbon Gel

Abstract This investigation on the origins of variable processability of emulsion SBR as measured by the BIT test established that no simple relationship exists between Mooney viscosity and processability, and that molecular weight distribution must be considered when producing to a BIT specification. By devising a sample preparation method directly from latex and the peak-height-ratio technique, a rapid method of estimating BIT from GPC chromatograms was developed. The method is suitable for process control. The mixing studies showed a general trend of increasing die swell with increasing BIT. The soluble rubber phase was found to have the same molecular weight distribution irrespective of the distribution at the commencement of mixing. It appears that die swell is influenced by variations in carbon-gel.

Extraction and Partial Purification of Protease from Bilimbi (Averrhoa bilimbi L.)

2013 ◽  
Vol 10 (2) ◽  
pp. 29
Author(s):  
Normah Ismail ◽  
Nur' Ain Mohamad Kharoe
Keyword(s):  
Molecular Weight ◽  
Protein Content ◽  
Ammonium Sulfate ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Protease Activity ◽  
Protein Concentration ◽  
Temperature Stability ◽  
Partial Purification ◽  
Ammonium Sulfate Precipitation

Unripe and ripe bilimbi (Averrhoa bilimbi L.) were ground and the extracted juices were partially purified by ammonium sulfate precipitation at the concentrations of 40 and 60% (w/v). The collected proteases were analysed for pH, temperature stability, storage stability, molecular weight distribution, protein concentration and protein content. Protein content of bilimbi fruit was 0.89 g. Protease activity of both the unripe and ripe fruit were optimum at pH 4 and 40°C when the juice were purified at 40 and 60% ammonium sulfate precipitation. A decreased in protease activity was observed during the seven days of storage at 4°C. Molecular weight distribution indicated that the proteases protein bands fall between IO to 220 kDa. Protein bands were observed at 25, 50 and 160 kDa in both the unripe and ripe bilimbi proteases purified with 40% ammonium sulfate, however, the bands were more intense in those from unripe bilimbi. No protein bands were seen in proteases purified with 60% ammonium sulfate. Protein concentration was higher for proteases extracted with 40% ammonium sulfate at both ripening stages. Thus, purification using 40% ammonium sulfate precipitation could be a successful method to partially purify proteases from bilimbi especially from the unripe stage. 

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