Current Study on Structural Characterization and Unique Film Formation of Hevea brasiliensis Natural Rubber Latex

2013 ◽  
Vol 844 ◽  
pp. 498-501 ◽  
Author(s):  
Jitladda Sakdapipanich

Hevea brasiliensis natural rubber (NR) latex is a very important commercial source of elastomers. It is not only a source for dry NR rubber but also the feedstock for the latex glove dipping industry. The particles of freshly tapped latex are known to be stabilized by proteins and lipids that come with the latex from the tree. These non-rubbers [, especially proteins and lipids, confer to the rubber and latex excellent properties unsurpassed by any synthetic latex [. Recent structural studies of NR revealed that the NR molecules comprise of 2 trans-isoprene units connected to a long-chain cis-isoprene units. Two terminal groups, referred to as ω and α, have been postulated to link with mono-and di-phosphate groups associated with phospholipids by H-bonding at the α-terminal, whereas the ω-terminal is a dimethylallyl group links to protein by H-bonding [. Although numerous studies have been published on the surface structure of the natural rubber particle [4-, none of these offered a direct in situ visualization of the intact particle surface. This is because of any attempt to remove this surface layer of proteins and lipids results in an immediate destabilization of the latex. The second part focused on the using of Atomic Force Microscopy (AFM) and Confocal Fluorescence microscopy to visualize and delineate the structure of the proteins and lipids layer on the latex particle surface in situ.

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Teeraporn Suteewong ◽  
Pramuan Tangboriboonrat

AbstractEpoxidised natural rubber (ENR) latex could be prevulcanized by employing tert-butyl hydroperoxide/fructose system. By applying the phase transfer/bulk polymerization/ transmission electron microscopy (TEM) technique, the uniform crosslink distribution in peroxide-prevulcanized (PP) ENR particle was observed. However, the membrane layer of protein-lipid complex, originally existing at rubber particle surface, could not be detected. Results implied that the alkoxy radicals penetrated throughout the rubber phase. The diffusion rate of radicals should be equal to that of vulcanization. Under TEM, the uniform mesh-like particle and cluster of the rubber chains were observed in PP(NR/ENR) while micrographs of PP-NR/PP-ENR blends showed only the crosslinked particles whose structure correlated well with that of PP-NR.


2014 ◽  
Vol 24 (3S1) ◽  
pp. 51-56
Author(s):  
Wirach Taweepreda ◽  
Supawadee Tuaybut ◽  
Sineenart Puangmanee ◽  
Tran Dang Khoa

Film formation of natural rubber latex (NRL) blended with various concentrations of chitosan was investigated. Atomic force microscopy (AFM) images clearly showed that the NRL film covered chitosan phase. Roughness of the films which was calculated from AFM image increases with increasing chitosan concentration. Miscibility of NRL and chitosan in solution was investigated by using dynamic mechanical thermal analysis (DMTA) and found that chitosan incorporated with NRL less than 40 weight percentage (wt%) was partially miscible. Films  of the chitosan blending with higher NRL contents exhibited two peaks of glass transition temperatures. Interfacial polarization and dielectric properties of polymer films were improved with increasing NRL contents. Chemical structure of the blends was characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR).


2015 ◽  
Vol 659 ◽  
pp. 383-387 ◽  
Author(s):  
Nut Churinthorn ◽  
Adun Nimpaiboon ◽  
Jitladda Sakdapipanich ◽  
Chee Cheong Ho

Natural Rubber (NR) latex obtained from Hevea brasiliensis contains a wide particle size distribution. The aim of this study is to investigate the effect of small rubber particles (SRP) and large rubber particles (LRP) on the characteristics of film formation. The rubber particle with different mean diameters can be separated by centrifugation at various speeds to prepare SRP and LRP latex. The average size of SRP and LRP were characterized by light scattering technique to show that the size of SRP was in the range of 0.20 μm, while that of LRP was larger with the wide distribution. SRP and LRP latex were dried at room temperature to study the film formation behaviors. The results showed that the film compaction time increased with increasing the particle size of NR. Furthermore, the rubber film were aged at room temperature for 3 weeks in order to observe the surface morphology using atomic forced microscopy (AFM) by tapping mode. The AFM images showed that SRP readily formed a coalescence film, while LRP showed individual particles on the surface of film at 24 h of storage time. The surface of both SRP and LRP films was smoother after storage. However, LRP film still showed individual particles on the surface after 3 weeks of storage time.


2014 ◽  
Vol 1024 ◽  
pp. 193-196
Author(s):  
Ibrahim Suhawati ◽  
Asrul Mustafa

The molecular weight of natural rubber (NR) can be reduced via depolymerization reaction to produce liquid natural rubber (LNR) with a molecular weight less than 50 000 g/mol. In the reaction, hydrogen peroxide and sodium nitrite were added to natural rubber latex to initiate a redox type reaction which then breaks the NR chain. Low permeation of reagents into latex particles allows the degradation to occur greater at the latex particle surface relative to the inner core contributes to high molecular weight distribution (MWD) or polydispersity of the LNR obtained. In this recent works, the reaction was carried out in a biphasic medium consisting of water and toluene phases. Toluene swells latex particles as indicated by the SEM micrographs showing changes in the size of latex particles. This occurrence is suggested to increase the influx of reagents into the latex particles. Consequently, with higher permeation of reagents into the latex particles resulted in the decrease of molecular weight and lower polydispersity of the LNR obtained. Chemical structure analysize showed that the LNRs obtained were attached with hydroxyl and carbonyl groups.


Author(s):  
Kanjanee Nawamawat ◽  
Jitladda T. Sakdapipanich ◽  
Chee C. Ho ◽  
Yujie Ma ◽  
Jing Song ◽  
...  

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