Polyolefin impact modifiers

Immiscible polyolefin impact modifiers have been compatibilized with PPE/PS blends by employing polyolefin sulfonate ionomers and including PS sulfonate ionomer in the blend (Table 5.54). In these compositions, the polyolefin ionomer can crosslink with PS ionomer. The latter is miscible with PS, which in turn is miscible with PPE. Simple ionomers have been used [Golba and Seeger, 1986 Campbell et al, 1986]. In similar blends, a masked ionomer, such as a polyolefin phosphonate ester, could also be used [Brown and McFay, 1986]. The masked ionomer is melt processable but generates a polyolefin phosphonate ionomer in situ during extrusion with zinc stearate. The polyolefin phosphonate ionomer can crosslink with PS sulfonate ionomer that is miscible with PS which in turn is miscible with PPE. 

Polyolefin impact modifiers are playing an increasing role, particularly with the flexibility of tailoring molecules offered by new catalyst technology. 

Obviously, there exists severe interplastics competition, e.g. PP vs. ABS, clarified PP vs. PS, PA, PVC, HDPE and PS (Table 10.7). A wide range of cross-linked and thermoplastic elastomer applications, from footware to automotive parts and toothbrushes, are adopting new metallocene-catalysed polyolefin elastomers (POEs). These low-density copolymers of ethylene and octene were first accepted as impact modifiers for TPOs, but now displace EPDM, (foamed) EVA, flexible PVC, and olefinic thermoplastic vulcanisates (TPVs). Interpolymer competition may also result from... 

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. 

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. 

Himont (now Montell Polyolefins) introduced a family of PP-based blends under the trade name of Hivalloy . Some grades seem to be mechanical alloys of PP/PS, compatibilized and impact modified by incorporation of SEBS and EPR. Others are reactor-made — here porous grains of PP serve as reaction beds for the polymerization and grafting of PS, SMA, acryhcs, etc. 

To lower PA s sensitivity to crack propagation under impact conditions, the resins are blended with 10-25% of an elastomer or a polyolefin. The impact-modified PA s exhibit good processability. They are mostly formed by injection molding. Special compositions have been formulated for extrasion of tubings. 

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... 

The well-known examples of blends are impact modified, toughened polymers, where polymers with different glass transition temperatures are blended, such as a rubber with a thermoplastic. Many other blends are known, such as barrier polymers for packaging, where specific polar or nonpolar polymers improve the properties of polymer blends, combined to increase the resistance against transport of water and a certain gas (oxygen, carbon dioxide, etc.), such as PA (barrier to oxygen) with a polyolefin (barrier to water vapor). 

Acrylic copolymers (i.e., core-shell impact modifiers with a shell of PMMA and a core of butyl acrylate elastomer) have been developed mainly for impact modification of PVC for outdoor applications. Butadiene-styrene copolymers are used exclusively for PVC, PC or styrene-acrylonitrile (SAN). Thermoplastic elastomers in the form of styrenic copolymers, e.g., SBS, are used preferably for styrenics and PA. Polyolefins, like EVA, are used for impact modification of technical polymers. 

PP is used in impact modified forms in films, bottles and crates and in unmodified form in ropes and twines. It is frequently present in domestic and industrial waste plastics in association with the polyethylenes. Owing to its pendant methyl groups PP is more readily peroxidised than the other polyolefins and it is not normally separated from them in domestic packaging waste. 

General Description Ultra low density polyethyl-enes (ULDPEs) and very low density polyethylenes (VLDPEs) are essentially synonymous designations for linear polyethylenes with densities down to 0.880 g/cu in. ULDPEs are finding applications as impact modifiers for other polyolefins. Dow Chemicals Attane ULDPE is an Ethylene/Octene copoly-... 

Uses Antioxidant for polyolefins, polyamides, polyesters, PVC, PS, rubbers, food-grade polymers impact modifier for PVC Regulatay FDA 21CFR 178.2010 Manuf./Dlstrlb. Aldrich Ciba Spec. Chems7/tddit. GE Spec. 

Hard, glassy, brittle thermoplastics such as polystyrene (PS) and polymethylmethacrylate (PMMA) have low attenuations, of order 6-10 dB/cm at 10 MHz, and in the case of PS, a low acoustic impedance. Ductile polymers such as polycarbonate (PC), many polyolefins and impact-modified thermoplastics generally have high absorption coefficients, in the range 20-40 dB/cm. The same molecular structures and mobiUty, which contribute to ductihty, may also contribute to absorption of ultrasonic energy. Not surprisingly, rubbers and, by extension, any polymer above its... 

Uses of Ethylene-Propylene Rubbers. EPDM and EPR vulcanizates are used in extruded profiles, cable insulation and jacketing, and roofing membranes. There are many automotive uses radiator hose, door and trunk seals, insulation, jacketing, and others. These elastomers are also used in applications such as window and architectural profiles, dock fenders, and washing-machine hoses. In short, their applications are extensive and diverse. Ethylene-propylene rubbers may be the most versatile of general-purpose rubbers. In addition, EP rubbers are added to polyolefin plastics as impact modifiers and as components of certain thermoplastic elastomer compositions (e.g., thermoplastic vulcanizates, which are discussed later in this chapter). 

Polyolefin (PO = PP, HOPE, EPR, or PMP) was blended with an impact modifier, 0.1-5 wt% colorant and/or 5-50 wt% of opadfios, and a styrene-diolefin block copolymer, grafted with 1-6 mol% of acrylic acid, maleic anhydride, or snlftniale functionality (SEBS, SEPS, radial SEB, or SEP). To improve scratch resistance the blend contained 100-3,000 ppm Zn stearate and 16-22C fatty acid amide. The alloys were injection molded into parts showing impact, scratch, and abrasion resistance. They were used to manufacture interior trim for vehicles and in other applications where a scratch- and scuff-resistant plastic material is required ... 

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