Blending with Natural Rubber

No changes in the glass transition temperature of PLA by the addition of NR were observed, confirming the immiscible behaviour of these blends. In addition, it was demonstrated that the NR acted as a nucleating agent enhancing the crystallization ability of PLA since a cold-crystallization exothermic peak was observed in the DSC heating curves. 

Blending of PLA with different thermoplastics and elastomers is an excellent alternative to copolymerization to improve PLA mechanical properties, in particular those related with the stress-strain behaviour, i.e. elastic modulus 

Hiljanen-Vainio, T. Kaqalainen and J. Seppala,/. Appl. Polym. Set, 1996, 59, 1281. 

Lopez-Rodriguez, A. Lopez-Arraiza, E. Meaurio and J. R. Sarasua, Polym. Eng. Set, 2006, 46, 1299. 

Utracki, Polymer Blends Handbook, Kluwer Academic Publishers, Norwell, MA, USA, 2002. 

---

Emulsion polymerisation of a mixture of butadiene and styrene gives a synthetic rubber (Buna S GBS rubber), which is used either alone or blended with natural rubber for automobile tyres and a variety of other articles. 

This lower has a number of ramifications on the properties of polybutadiene. For example, at room temperature polybutadiene compounds generally have a higher resilience than similar natural rubber compounds. In turn this means that the polybutadiene rubbers have a lower heat build-up and this is important in tyre applications. On the other hand, these rubbers have poor tear resistance, poor tack and poor tensile strength. For this reason, the polybutadiene rubbers are seldom used on their own but more commonly in conjunction with other materials. For example, they are blended with natural rubber in the manufacture of truck tyres and, widely, with SBR in the manufacture of passenger car tyres. The rubbers are also widely used in the manufacture of high-impact polystyrene. 

High cis- 1,4-poly butadiene is manufactured on a large industrial scale and occupies a well-defined position in the elastomers market. It is employed mainly in the tyre industry, where it is blended with natural rubber and/or with styrene-butadiene rubber and applied in either sidewalls, threads or rims of tyres. It should be noted in this connection that natural rubber, in contrast to its synthetic counterpart, displays some physical properties that appear to be useful in the manufacture of tyres for heavy-duty machines. The fact is that some non-hydrocarbon substances appearing in natural rubber in small amounts (such as polypeptides) protect the high-dimensional tyre formed against collapsing prior to the vulcanisation process and thus enable a high-quality product to be obtained. 

As regards high Irons- 1,4-poly butadiene, it has a few applications, especially as a blend with natural rubber. Syndiotactic 1,2-polybutadiene is a unique material that combines the properties of plastic and rubber. These properties lead to applications both as a thermoplastic resin and as a rubber. As regards isotactic 1,2-polybutadiene, one may note that its properties have not excited sufficient interest for commercial development. 

Polybutadiene, CAS 9003-17-2, is a common synthetic polymer with the formula (-CH2CH=CHCH2-)n- The cis form (CAS 40022-03-5) of the polymer can be obtained by coordination or anionic polymerization. It is used mainly in tires blended with natural rubber and synthetic copolymers. The trans form is less common. 1,4-Polyisoprene in cis form, CAS 9003-31-0, is commonly found in large quantities as natural rubber, but also can be obtained synthetically, for example, using the coordination or anionic polymerization of 2-methyl-1,3-butadiene. Stereoregular synthetic cis-polyisoprene has properties practically identical to natural rubber, but this material is not highly competitive in price with natural rubber, and its industrial production is lower than that of other unsaturated polyhydrocarbons. Synthetic frans-polyisoprene, CAS 104389-31-3, also is known. Pyrolysis and the thermal decomposition of these polymers has been studied frequently [1-18]. Some reports on thermal decomposition products of polybutadiene and polyisoprene reported in literature are summarized in Table 7.1.1 [19]. 

BR is used in nearly all parts of the tire with the exception of the inner liner it is always blended with natural rubber (NR) or styrene-butadiene rubber (SBR). Apart from the extrudability, in NR blends the Nd-BR polymers exhibit advantages in all important compound and vulcanizate properties. Also, in SBR blends Nd-BR leads to the best vulcanizate properties in comparison with all other types of BR. 

These may be used for low hardness compounds in areas where impact abrasion is predominant. EPDM is at times referred as crackless rubber5 since it has high tear resistance. For producing high hardness compounds blends with natural rubber, styrene-butadiene rubber (SBR) and high styrene resins are recommended. 

Polybutadiene Higher resilience than similar natural rubber compounds, good low-temperature behavior and adhesion to metals, but poor tear resistance, poor tack, and poor tensile strength Blends with natural rubber and SBR manufacture of high-impact polystyrene... 

Properties M.w. 2,000,000 Uses Elastomer used for low hardness/damping compds., esp. for blending with natural rubber to modify damping behavior bellows profiles seals roller coverings... 

Polybutadiene Automotive tires (blended with natural rubber and styrene butadiene rubber), golf ball skin, etc. 

Photomicrographs obtained on these blends with natural rubber confirm incompatibility at higher molecular weights as shown in Pigs. 11-14. Two distinct phases are clearly seen in Fig. 14 the composition containing the highest molecular weight resin (M 1,800). The dispersed phase is... 

Now dynamically vulcanized rubber-plastic blends are poised to enter the realm of automobile tires. A TPV comprising a PA thermoplastic phase with isobutylene-co-p-methylstyrene (BIMSM) rubber can be used as an innerliner, outperforming either historical butyl rubber or the more classical halobutyl and its blend with natural rubber. These and future developments are targeting down-gauging of the barrier film thickness to simultaneously reduce both tire weight and reduced air permeation. A five-to-tenfold reduction in the latter is claimed to be feasible along with improved tire performance (Tsou 2007). 

The butadiene-styrene rubber (SBR), or butadiene-acrylonitrile rubber (NBR) and elastomeric graft copolymers were found particularly valuable for impact modification of PP. The PP alloys (with 5-20 wt.% of an elastomer) were reported to have advantageous properties for blow molding of bottles free from brittleness and stress cracking. Blends with natural rubber (NR) require sulfur-curing [4]. Blending with NBR dramatically increased the modulus, but the material was brittle [5]. 

The latex is ammoniated, coagulated, and air dried or smoked to obtain gum rubber. As with most other rubbers, a tackifier must be blended with natural rubber in order to prodnce a PSA, since the rubber itself has a very low glass-transition temperature (Tg-----70°C) and a high shear storage plateau modulus. The molec-... 

Acrylate polymers are often used in many applications that require good optical properties. However, they are unsuitable for use in the automotive industry because of their brittle characteristics. Thus, when natural rubber is blended with poly(methyl methacrylate), there is a big improvement in the elasticity of the brittle acrylate polymers. It is of interest that thermoplastic natural rubbers are relatively new products in the rubber industry and are fastgrowing items in the polymer market. The acrylate polymers blended with natural rubber can improve various properties of both the natural rubber and the acrylate polymers such as elasticity, adhesion, processability properties, and transparency. These materials are known for their excellent processability, characteristic of acrylate polymers, and their elasticity property provided by natural rubber, thus they exhibit the typical properties of elastomeric materials and can be processed with thermoplastic processing equipment used to prepare acrylate polymers. Many of their interesting properties have been widely developed for several industrial applications such as in the automotive industry, household appliances, medical devices, electrical cables, and headphone cables. ... 

An alternative method of producing natural rubber based clay reinforced nanocomposites with outstanding properties is by using a spray drying technique. In this technique the siUcate layers of clay will be well dispersed in an irradiated polymer latex and this mixture will be sprayed through hot air to produce micrometre-sized liquid droplets. When the solvent is fully evaporated, micrometre-sized polymer spheres with delaminated clay silicate layers on their surface are produced. These spheres can later be melt blended with natural rubber to produce ternary nanocomposites. It is noteworthy that exfoliation of nanofillers can still be achieved without modification of the nanofiller surface, thus the expensive modification process can be eliminated. 

The extent of clay dispersion and clay-polymer interaction is crucial in determining the formation of natural rubber based nanocomposites. Due to the low polarity and high viscosity of natural rubber, direct blending of clay nanoparticles into natural rubber will only yield micro-scale composites. Thus, it is more effective to blend clay nanoparticles into another polymer component before blending with natural rubber. 

Natural rubber/chlorosulfonated polyethylene rubber blends also exhibited immiscibility. Chlorosulfonated polyethylene rubber is the synthetic rubber used for applications in electric cables, hoses for liquid chemicals, waterproof cloths, floor tiles, and oil-resistant seals. It is chosen to blend with natural rubber to improve the resistance of natural rubber to ozone, oil, heat, flame and non-polar chemicals. This is due to the effect of the polarity of the chlorine groups in the chlorosulfonated polyethylene rubber. The tensile strength, elongation at break, and tear strength of these blends decreased with the increasing chlorosulfonated polyethylene rubber contents. In addition, the compatible natural rubber/chlorosulfonated polyethylene rubber blends were improved by adding the epoxidized natural rubber (Epoxyprene 25) as a... 

Several studies are being conducted in order to improve PHBV mechanical properties and/or decrease its cost and enabling its industrial application. Among many studies it is possible to find addition of plasticizers (Choi and Park 2004), production of blends, including blends with natural polymers such as polycapro-lactone, poly(L-lactic acid), starch, and cellulose (El-Hadi et al. 2002 Ferreira et al. 2002) and also with synthetic polymers such as polyvynyl phenol (Fei et al. 2004), oxidized polyethylene, and polypropylene (Avella et al. 2002), blends with natural rubber (Han et al. 2004), among others. 

Brominated butyl rubbers are of interest for truck tyre inner tubes because of their heat resistance, in giant type inner tubes because they may be blended with natural rubber to give a useful combination of properties, and for a variety of other uses. 

---