Elastomer processability

Elastomeric state Elastomer modifiers Elastomer process Elastomers... 

The elastomer process is very similar to the Dennis process. It involves a number of steps in which a gas, formerly carbon dioxide and now fluorocarbon, is mixed with a plastisol under pressure. When released to atmospheric pressure, the gas expands the vinyl compounds into a low density, open-ceUed foam which is then fused with heat. 

As to the first route, we started in 1969 (1) in investigating unconventional transition metal complexes of the 5 and 4f block elements of periodic table, e.g., actinides and lanthanides as catalysts for the polymerization of dienes (butadiene and isoprene) with an extremely high cis content. Even a small increase of cistacticity in the vicinity of 100% has an important effect on crystallization and consequently on elastomer processability and properties (2). The f-block elements have unique electronic and stereochemical characteristics and give the possibility of a participation of the f-electrons in the metal ligand bond. 

Prior to 1941, Germany had a major technical and industrial lead over the USA, having already established an industrial styrene monomer production process, a styrene-butadiene elastomer process and a mass styrene polymerization process [6]. Figure 1.2 shows the polymerization vessels at I. G. Farben in 1940. Figure 1.3 shows a bank of polymerization kettles. The Germans began the first technical production of polystyrene in 1930 while the first production of polystyrene in the USA was some 8 years later by Dow in 1938. 

Siloxane Elastomer Processing From Aqueous Dispersion... 

Novel process on the base of compact tubular reactors is principally fitted for production of bromobutyl rubber and also others chlorinated elastomers. Process is accepted at OAO "Nizhne-kamskneftekhim". In 2001-2002 pilot plant worked at which chlorobutyl rubber of required quality was received without any problems. Technical schedule was made. At present experimental-industrial plant is projected. 

Elastomer processing covers the three (essential) process steps... 

Features Flexible transparent hydrophobic coprocessable with oletinic plastics, hydrocarbon elastomers processes at relatively low temps. exc. chem. resist. bondable to itself and other substrates Properties Pellets or agglomerate melt flow index 15 (265 C, 5 kg) sp.gr. 

In some individual cases of molding thermoplastics, but more frequently with elastomer processing, the finished article cannot be ejected automatically. The part must then be removed manually, because with elastomers, complex articles (as well as those with undercuts) are often produced from comparably simple molds, due to the material s stretchability and flexural properties. The removal of such parts is often so comphcated, that-if at all-only the most highly specialized handling devices ean be employed for automatic demolding. Therefore, manual removal still continues to be carried out in the elastomer processing industry even today. 

CAS 13189-00-9 EINECS/ELINCS 236-144-8 Synonyms Methacrylic acid, zinc salt 2-Methylacrylic acid zinc salt 2-Propenoic acid, 2-methyl-, zinc salt ZDMA Zinc dimethacrylate Zinc 2-methyl-2-propenoate Classification Nonaromatic acid salt Empirical CsHio04Zn Properties M.w. 235.54 m.p. 229-232 C Toxicology Irritating to eyes, skin, respiratory system sensitizer TSCA listed Uses Coagent, scorch retarder, crosslinking agent for elastomer processing and cure polymer modifier... 

Kleemann W Weber K, Elastomer Processing. Formnlas and Tables. Hanser Verlag, Munich, 1998. Struktol Plasticizers. 

In this chapter, the dramatic effect that monol content or polyol functionality has on processability and properties of polyurethane cast elastomers is discussed. This effect is shown for elastomers prepared by both the prepolymer and one-shot processes. Further improvements in elastomer processability and formulating latitude can be achieved by incorporating oxyethylene moieties into the polyol backbone. For one-shot elastomer processes, ultra-low monol PPG polyols capped with ethylene oxide have been commercialised. 

The importance of monol content in 4,T-MDI/BDO cured elastomer systems was determined by comparing 4000-MW PPG diols prepared via ultra-low monol technology, DMC and potassium hydroxide. They are designated as ultra-low monol, low monol and conventional and have monol contents of 0.005,0.016 and 0.085 meq/g, respectively. This corresponds to functionalities of 1.98, 1.94 and 1.71. We prepared 6% NCO 4,4"-MDI prepolymers and chain extended with BDO at an isocyanate to hydroxyl ratio (NCO OH) of 1.03 [15]. Table 9.3 summarises the monol effect on elastomer processing characteristics (pot life and demould time), and physical properties. 

The monol content has a major effect on elastomer processability. Lower monol content results in a faster molecular weight build, which reduces demould time. Elastomers based on the 4000-MW, ultra-low monol PPG had demould times as short as 20 minutes, whereas, the low monol PPG gave demould times of over one hour. The elastomer based on conventional polyol had a demould time greater than three hours. 

A review of the elastomer processability and physical property data indicates that there is an optimum hardness range for each polyol MW. Based on the demould time and the percent compression set, the following elastomer Shore hardness ranges are recommended. The lower hardness limits of these ranges can be extended by addition of low levels (less than 10%) of 6000-MW, ultra-low monol triol (Acclaim Polyol 6300). 

The 8000-MW, ultra-low monol PPG is used particularly in the development of soft, plasticiser-free elastomers [16, 17]. The nse of this high MW, low polydispersity polyol allows for the preparation of low viscosity prepolymers with low isocyanate contents. Initial evalnations of these very soft elastomers showed lower than expected physical properties. The lower properties can be attributed to the very low hard-segment content of these polymers. The lack of hard segment (physical crosslinks) can be compensated for by the incorporation of low levels of chemical crosslinks (triol) [18]. This is accomplished by the addition of a 6000-MW, ultra-low monol triol (Acclaim Polyol 6300) into the polymer matrix. Table 9.7 shows the triol effect on prepolymer viscosities, elastomer processability and physical properties. It shonld be noted that very low levels of crosslinking are needed to improve the elastomer properties. 

Effect of Primary Hydroxyl Concentration on One-Shot Elastomer Processability... 

Effect of Monol Content on One-Shot Elastomer Processability and Properties... 

As expected, the monol content of the EO-capped PPG diols has a significant effect on the elastomer processability. The Shore hardness of the conventional elastomer was only 57A after 16 hours cure at 100 C, whereas the elastomer based on ultra-low monol PPG had a hardness of 78A. It took three weeks for the conventional... 

For a comparison of PTMEG in MDI/BDO cured elastomers the 3200-MW ultra-low monol PPG diol was chosen which contains about 20 wt% EO (Acclaim Polyol 3205) since it gives the best overall properties in this type of system. A 2000-MW PTMEG was used since it gives the best performance at an 80 Shore A hardness. Elastomers of 80 Shore A hardness were prepared using the prepolymer process. Table 9.14 summarises their prepolymer viscosities, elastomer processing characteristics and physical properties. 

C.P. Rader, J. R. Richwine, E. P. Tam, G. E. O Connor, Santoprene thermoplastic elastomer processability and product applications. International rubber and plastic exhibition and conference for Asia, Singapore, 1986 A. Seeffied, M. Fuchs, D. Drummer, Plast. Eng. 68(10), 14 (2012)... 

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