Polybutadienes high impact polystyrene

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-impact polystyrene (polystyrene modified with styrene-butadiene rubber (SBR) or polybutadiene rubber). 

Polystyrene (PS) The volume of expanded polystyrene produced probably exceeds the volume production of all other plastics (excluding the polyurethanes) put together. At least half the weight of polystyrene produced is in the form of high impact polystyrene (HIPS)—a complex blend containing styrene-butadiene rubber or polybutadiene. 

In a block copolymer, a long segment made from one monomer is followed by a segment formed from the other monomer. One example is the block copolymer formed from styrene and butadiene. Pure polystyrene is a transparent, brittle material that is easily broken polybutadiene is a synthetic rubber that is very resilient, but soft and opaque. A block copolymer of the two monomers produces high-impact polystyrene, a material that is a durable, strong, yet transparent plastic. A different formulation of the two polymers produces styrene-butadiene rubber (SBR), which is used mainly for automobile tires and running shoes, but also in chewing gum. 

Mixing polystyrene with an elastomer such as polybutadiene makes it tougher. This material is called high-impact polystyrene. 

SEM and transmission electron microscopy (TEM) are employed to examine materials for the presence and distribution of impact modifiers such as polybutadiene rubber in high impact polystyrene (HIPS) and methacrylate butadiene styrene terpolymer in PVC. Quantification is either by transmission IR spectroscopy against standards or nuclear magnetic resonance (NMR) spectroscopy. 

Note An example is the incorporation of soft polybutadiene domains into glassy polystyrene to produce high-impact polystyrene. 

The concept is similar to the grafting of plants in botany. To form a styrene-butadiene graft polymer, already polymerized butadiene is dissolved in monomeric styrene and an initiator is added. Because polybutadiene readily undergoes chain transfer at the allylic sites, polystyrene chains grow on the polybutadiene backbone. This forms high impact polystyrene, a low cost plastic that is otherwise too brittle without the grafting. 

Polycarbonate is blended with a number of polymers including PET, PBT, acrylonitrile-butadiene-styrene terpolymer (ABS) rubber, and styrene-maleic anhydride (SMA) copolymer. The blends have lower costs compared to polycarbonate and, in addition, show some property improvement. PET and PBT impart better chemical resistance and processability, ABS imparts improved processability, and SMA imparts better retention of properties on aging at high temperature. Poly(phenylene oxide) blended with high-impact polystyrene (HIPS) (polybutadiene-gra/f-polystyrene) has improved toughness and processability. The impact strength of polyamides is improved by blending with an ethylene copolymer or ABS rubber. 

Preparation of a Polystyrene/Polybutadiene-Blend (High Impact Polystyrene, HIPS) by Polymerization of Styrene in the Presence of Polybutadiene... 

The term graft copolymer is used to describe copolymers with long sequences of another monomer (comonomer) as branches on the main polymer chain. Most commercial varieties of high-impact polystyrene (HIP) and copolymers of acrylonitrile, butadiene, and styrene (ABS) are graft copolymen in which the main polymer chain is polybutadiene and the branches are styrene, or styrene and acrylonitrile. Figure 1.12 shows various types of copolymers. 

As of this date, there is no lithium or alkyl-lithium catalyzed polyisoprene manufactured by the leading synthetic rubber producers- in the industrial nations. However, there are several rubber producers who manufacture alkyl-lithium catalyzed synthetic polybutadiene and commercialize it under trade names like "Diene Rubber"(Firestone) "Soleprene"(Phillips Petroleum), "Tufdene"(Ashai KASA Japan). In the early stage of development of alkyl-lithium catalyzed poly-butadiene it was felt that a narrow molecular distribution was needed to give it the excellent wear properties of polybutadiene. However, it was found later that its narrow molecular distribution, coupled with the purity of the rubber, made it the choice rubber to be used in the reinforcement of plastics, such as high impact polystyrene. Till the present time, polybutadiene made by alkyl-lithium catalyst is, for many chemical and technological reasons, still the undisputed rubber in the reinforced plastics applications industries. 

Another widely used copolymer is high impact polystyrene (PS-HI), which is formed by grafting polystyrene to polybutadiene. Again, if styrene and butadiene are randomly copolymerized, the resulting material is an elastomer called styrene-butadiene-rubber (SBR). Another classic example of copolymerization is the terpolymer acrylonitrile-butadiene-styrene (ABS). Polymer blends belong to another family of polymeric materials which are made by mixing or blending two or more polymers to enhance the physical properties of each individual component. Common polymer blends include PP-PC, PVC-ABS, PE-PTFE and PC-ABS. 

Polystyrene (PS) in its atactic and syndiotactic forms is a brittle thermoplastic, even in an orientated state [4]. To improve the toughness of aPS, impact modification has been practised for a long time, either by polymerizing the styrene in the presence of a polybutadiene rubber leading to high-impact polystyrene, commonly called HIPS, or by blending the polystyrene with multi-block copolymers, mainly of the styrene-butadiene-styrene (S-B-S) type. 

Polystyrene and ABS are the polymers that are most commonly modified with SBCs. SBS triblocks and SB diblocks with 30-40% styrene are often used in concentrations near 5% either as a toughener alone in combination with polybutadiene in high-impact polystyrene. In addition to the use of elastomeric... 

Rubber is incorporated into polystyrene primarily to impart toughness. The resulting materials consist of a polystyrene matrix with small inclusions of the rubber (usually 5-10wt% polybutadiene or copolymer rubber). They are termed high-impact polystyrene (HIPS). Grafting of the rubber to the polystyr-... 

Table 9-2 summarizes differences between polybutadiencs produced by different processes. The low c/i-content polybutadienes are branched. Tliey have lower solution viscosities than their linear counterparts and are preferred for manufacture of high impact polystyrene (HIPS) in which polymerization takes place in a solution of the elastomer in styrene. As the reaction proceeds under agitation, polystyrene becomes the continuous phase, with dispersed droplets of rubber (see Chapter 11). The high m-content, linear polybutadienes are more elastomeric... 

Bulk polymerization is the main process for making high-impact polystyrene (HIPS). Polybutadiene is dissolved in styrene at 3-10% (w/w) concentration and the styrene is polymerized with careful agitation. Phase separation occurs with polybutadiene-g-polystyrene separating out. The final product is a dispersion of polybutadiene particles, which themselves contain occluded polystyrene. Polymerization conditions are adjusted to control the size and volume of these particles, which range respectively from 0.1 to 6.0 pm and 0.1 to 0.4 volume fraction of the material. 

Styrene and butadiene also form copolymers known as high impact polystyrene, or rubber-modified polystyrene, when the content of butadiene is 10%. This type of material has excellent mechanical properties, and it is widely used in practice for the manufacturing of numerous objects, including parts for household appliances, furniture, etc. Rubber-modified polystyrene is commonly used as wood replacement and also for packaging. The synthesis of this material typically is done by dissolving polybutadiene in styrene monomer, followed by free radical polymerization achieved using a peroxide catalyst. This procedure leads to block or graft type copolymers. 

ID, 2D and 3D experiments, all H, and Sn chemical shifts for four postulated Sn species could be resolved unambiguously. Variable temperature and variable stress NMR spectroscopic and imaging studies are reported for a sample of high impact polystyrene. NMR microscopy and solid state stray field imaging studies indicated that imposed stress affects the molecular chain dynamics only of the polybutadiene region and not of the polystyrene(PS) matrix.The principal values of the chemical shift tensors and the separated-local field pattern are reported for the all-... 

Figure 2. Transmission electron micrographs of six polybutadiene/polystyrene sequential IPN s and related materials, the polybutadiene portion stained with osmium tetroxide. Upper left high-impact polystyrene, commerciaL Upper right a similar composition made quiescently. Middle left semi-I IPN, PB (only) crosslinked. Middle right semi-II IPN, PS (only) crosslinked. Lower left full IPN, both polymers crosslinked. Lower right full IPN, PB with higher crosslink level. (Reproduce from ref. 5. Copyright 1976 American Chemical Society.)...

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