Polypropylene impact modifiers

Rubber modified polypropylene polypropylene/ethylene propylene rubber blends ethylene propylene rubber, polypropylene blends elastomer modified thermoplastic elastomer modified polypropylene impact modified polypropylene olefin thermoplastic elastomer thermoplastic polyolefc rubber. 

By employing additives to improve interfacial adhesion and the cohesive strength of the mbber phase, natural mbber can compete with ethylene—propylene mbbers as an impact modifier for polypropylene. These hard grades, containing between 15 and 25% natural mbber, have the potential for use in the automotive and domestic markets, eg, in bumpers, spoilers, grilles, electrical connectors, and floor tiles. 

Considerable amounts of EPM and EPDM are also used in blends with thermoplastics, eg, as impact modifier in quantities up to ca 25% wt/wt for polyamides, polystyrenes, and particularly polypropylene. The latter products are used in many exterior automotive appHcations such as bumpers and body panels. In blends with polypropylene, wherein the EPDM component may be increased to become the larger portion, a thermoplastic elastomer is obtained, provided the EPDM phase is vulcanked during the mixing with polypropylene (dynamic vulcani2ation) to suppress the flow of the EPDM phase and give the end product sufficient set. 

Stehling F.C., Huff T., Speed C.S., and Wissler G. Stmeture and properties of mhher modified polypropylene impact blends, J. Appl. Polym. Sci., 26, 2693, 1981. 

Figure 19.8 Two-phase structure of impact modified polypropylene...

Figure 4.35(b) displays examples of creep under relatively high stresses (7 to 14 MPa) at room temperature for impact-modified rigid PVC or PVC-HL Times are much longer than for the previous graph (20 000 h versus 400). Compared to Figure 4.35(a), the plasticization decreases the creep moduli. However, they are always higher than those of polyethylene or polypropylene (less than 1 GPa) for a same creep time. 

Improvements of clarity in transparent materials can be obtained in a variety of ways. If unplasticized poly(vinyl chloride) includes an impact modifier with refractive index matching that of the polymer it is possible to use thinner sections and so increase clarity, rates of output, and gloss. With polyolefins, similar results may be achieved by including a nucleating agent to accelerate crystallization even polypropylene, which normally is translucent, thus can be made in an almost clear form. 

On the other hand, it is not always necessary that an interfacial agent be present. Polypropylene is available in impact-modified grades which are made by simply blending polypropylene with suitable olefin-based elastomers. Most often the elastomer is a suitably chosen ethylene-propylene-based rubber. Evidently, the required adhesion develops naturally in these systems without the need for an interfacial agent. However, proper control of phase morphology during mixing is essential. 

The use of olefin rubbers [18] as good impact modifiers for sPS when used in conjunction with S-B or S-B-S block copolymers, which may be hydrogenated in the butadiene phase, has also been described. Instead of butadiene, isoprene can be used. Examples of the olefinic polymers are polyethylene, ethylene-propylene rubbers (EPR) and polypropylene-(ethylene propylene rubber) block copolymers. Here the styrene block copolymers presumably function as... 

Impact-modified polypropylenes are produced by combining the homopolymer with an ethylene-propylene copolymer rubber. Ziegler-Natta processes yield such products in cascaded reactors. The first reactor in the sequence produces a rigid polymer with a high propylene content and feeds the second reactor, where the ethylene-propylene elastomer is polymerized in intimate mixture with the first material. 

System 1 This morphology is produced when no reaction can occur between the impact modifier and the accelerator. This can be achieved by using as impact modifier a methoxylated polypropylene glycol (PPG) ("solution I ). 

In addition to zero-shear viscosity, material elasticity plays an important role in determining coalescence behavior in the rotational molding process.For rotational molding grade material, this effect was first recognized from the experimental results obtained with impact modified polypropylenes and is illustrated in Fig. In this work, the relative elasticity of resins... 

The brittleness of polyvinyl chloride and polystyrene was decreased by blending with plasticizers or impact modifying polymers. The flammability of polystyrene and polyolefins was decreased by the addition of flame retardants and the Instability of polyvinyl chloride and polypropylene was reduced by the addition of stabilizers. — The strength and heat resistance of all of the general purpose plastics were Improved by reinforcing with fiberglass or graphite fibers. 

Polybond . [BP Performance Polymers] Polypropylene or polyethylene compounds thermr lastic fa- use as chemical coupling agent, conqratibilizing agent, metal adhesive and nucleating agent impact modifier additive in polymer aUoys, for adhesion to metals and polar polymers. 

Commercial impact modified PP were developed during the early 1970 s by melt blending about 5 to 25 wt% ethylene-propylene rubbers (EP or EPDM) with the polypropylene homopolymer via extruder compounding [Holzar, 1966]. Some LDPE or HOPE is often used to assist the dispersabUity of the EP rubber and enhance the impact/modulus balance of the product [D Orazio,... 

Impact modified polypropylene is used for injection molding automotive, consumer and appliance parts. For example, the medium impact PP is widely used for automotive interior trim. High impact PP is used for battery cases, fender and truck liners. Impact PP is also used extensively in the houseware and appliance markets. 

Owing to adequate level of compatibility between polypropylene and ethylene-propylene copolymers, simple blends of these two polymers have been known for a long time. Impact modified... 

The commercial grades of polyamide/polycarbonate blend (Dexcarb ) exhibit high notched Izod impact strength comparable to that of impact modified polyamides and polycarbonate (Table 15.24). It is believed that an elastomeric impact modifier was included in these compositions. Patent claims the use of a polyetheramide and a maleated polypropylene or EPR as the compatibilizing/ impact modifying additives [Perron, 1988]. The commercial grades contain varying amounts of PC, PA-66 (or 6) and the impact modifier. 

Blends of polyolefins (e.g., HPDE/LDPE, LDPE/ ethylene copolymers, PP/EPDM, PP/HDPE/EPDM, HDPE/butyl rubber) have been commercial since the late 1960 s and early 1970 s. Specific film formulations were commonly based on polyolefin blends to achieve the proper balance of processing, environmental stress crack resistance, modulus, toughness, cling, transparency, filler acceptance, printability, tear resistance, shrinkage characteristics, and permeability. Ethylene-propylene mbber (EPR, EPDM) was commonly incorporated into polypropylene as an impact modifier at moderate levels and as a flexibilizer at high levels. One of... 

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