Rubber Hydrocarbon in Freshly Tapped Latex

1954 ◽  
Vol 27 (4) ◽  
pp. 1061-1067 ◽  
Author(s):  
G. F. Bloomfield
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Molecular Weight Range ◽  
Considerable Heterogeneity ◽  
Weight Range ◽  
Molecular Material ◽  
Wide Range ◽  
Soluble Fractions

Abstract Investigations carried out in Malaya have shown that rubber hydrocarbon in fresh latex is already a high molecular material but of considerable heterogeneity. Latex is separable into non-rubber constituents and rubber hydrocarbon, which is itself separable into microgel, soluble fractions covering a wide range of molecular weight, and low-molecular oxygenated fractions. The molecular weight distribution of the soluble hydrocarbon material is weighted heavily in the higher molecular weight range of half million to five million, with an average around one million. Coagulated rubber contains macrogel in addition to the microgel component of the latex. The microgel component of latex hydrocarbon has been used as a “marker” to indicate from what regions of a tree rubber is withdrawn on tapping.

Polytetramethylene Ether Glycol: Effect of Concentration, Molecular Weight, and Molecular Weight Distribution on Properties of MDI/BDO-Based Polyurethanes

1982 ◽  
Vol 55 (1) ◽  
pp. 76-87 ◽  
Author(s):  
E. Pechhold ◽  
G. Pruckmayr
Keyword(s):  
Molecular Weight ◽  
Low Temperature ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Soft Segment ◽  
Hydrolytic Stability ◽  
The Other ◽  
Molecular Weight Range ◽  
Weight Range ◽  
Other Hand

Abstract Hardness, modulus, and tear strength of PTMEG-based polyurethanes are mainly affected by the hard-segment (MDI/BDO) concentration. On the other hand, PTMEG molecular weight mainly influences low-temperature and dynamic properties. Resilience and hydrolytic stability are affected by both soft-segment concentration and chain length. PTMEG of narrow molecular weight distribution yields softer polyurethanes with considerably longer elongation at break. Broad molecular weight distribution is advantageous only at the lower molecular weight range (650 and 1000), giving rise to improved resilience and low-temperature performance. Polyurethanes made from PTMEG of low molecular weight (Mn≤1000) have inherent drawbacks due to poor phase separation (high Tg) and limits in soft segment concentration (∼63% maximum for PTMEG 1000). The only advantage they offer is easier processability (lower viscosity and melting temperature). On the other hand, PTMEG above 2100 offers little property advantages and is more difficult to handle. Optimum overall polyurethane properties can be achieved with PTMEG in the molecular weight range of 1800 to 2100. It is conceivable that PTMEG-based polyurethanes made with different diisocyanates, curatives, curative/NCO ratios, or in the presence of triols or catalysts may show similar trends as the MDI/BDO formulations described in this study.

Research on Determination for Food-Related Polystyrene Doped with Recycled Plastic by GPC

2014 ◽  
Vol 1033-1034 ◽  
pp. 954-957
Author(s):  
Xiao Lei Zhang ◽  
Lei Wang ◽  
Xiao Qi Chen ◽  
Hai Jun Zhou ◽  
Shu Lan Yang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Food Packaging ◽  
Gel Permeation Chromatography ◽  
Cumulative Distribution ◽  
Mechanical Recycling ◽  
Wide Range ◽  
Gel Permeation ◽  
Physical Degradation

Polystyrene (PS) had wide range of applications in food packaging field. Mechanical recycling of PS was simulated by multiple extrusions to assess the behavior of physical degradation. The molecular weight and the molecular weight distribution of PS with different extrusion cycles were investigated by gel permeation chromatography (GPC). Experimental results show that the differential and cumulative distribution curves of PS shift to smaller values with the number of extrusions cycled increasing. The Mn and Mw of PS decrease. However, Polydispersity index (PDI) increases obviously.

Preparation and Physicochemical Properties of Concrete Slump-Loss Resistance Agent for Small Slump

2010 ◽  
Vol 168-170 ◽  
pp. 2158-2164
Author(s):  
Guo Rong Duan ◽  
Guo Hong Huang ◽  
Xin Wang ◽  
Ying Gong
Keyword(s):  
Molecular Weight ◽  
Physicochemical Properties ◽  
Molecular Weight Distribution ◽  
Cement Paste ◽  
Weight Distribution ◽  
Synthesis Method ◽  
Retention Performance ◽  
Wide Range ◽  
Loss Resistance ◽  
Gel Permeation

By the application of esterification-polymerization two-step synthesis method, comb-shaped polycarboxylate slump-loss resistance agent XBT for small slump concrete is prepared by controlling ester ratio. The experimental results of concrete and fresh cement paste indicate that XBT has excellent function of plasticity retention in small slump concrete. The experiment of gel permeation liquid chromatogram shows that XBT has wide range of molecular weight distribution, which may be the source of fine plasticity retention performance in the small slump concrete. The combined experiment between ultraviolet and conductivity indicates that there is strong adsorptive action between XBT and Ca2+, and their adsorptive characteristics may be closely related to the plasticity retention properties.

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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