Nitrile resin

DR (Rohm and Haas) and Plex 8535-F (Rohm GmbH). Some typical properties of these materials compared with straight PMMA and with the competitive ABS and ASA polymers (discussed in Chapter 16) are given in Table 15.3. 

Over the years many attempts have been made to produce commercial acrylic polymers with a higher softening point than PMMA. The usual approach was to copolymerise MMA with a second monomer such as maleic anhydride or an N-substituted maleimide which gave homopolymers with a higher Tg than PMMA. In this way copolymers with Vicat softening points as high as 135°C could be obtained. 

In the early 1990s attention appeared to be focusing on the imidisation of acrylic polymers with primary amines. 

As might be expected from a consideration of the factors discussed in Section 4.2, the imidisation process will stiffen the polymer chain and hence enhance Tg and thus softening points. Hence Vicat softening points (by Procedure B) may be as high as 175°C. The modulus of elasticity is also about 50% greater than that of PMMa at 4300 MPa, whilst with carbon fibre reinforcement this rises to 25 000 MPa. The polymer is clear (90% transparent) and colourless. 

Such materials, known as poly(methyl methacrylimides) or PMMI, are marketed by Rohm and Haas in the USA as Kamex, and there is a small production by Rohm in Europe, where the product is marketed as Pleximid. 

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Acrylonitrile-butadiene-styrene-poly(vinyl chlo- Nitrile resins... 

The principal monomer of nitrile resins is acrylonitrile (see Polyacrylonitrile ), which constitutes about 70% by weight of the polymer and provides the polymer with good gas barrier and chemical resistance properties. The remainder of the polymer is 20 to 30% methylacrylate (or styrene), with 0 to 10% butadiene to serve as an impact-modifying termonomer. 

Substantial quantities of UPVC are also used for blow moulded containers for such diverse materials as consumable liquids such as fruit squashes, liquids for household use such as detergents and disinfectants, cosmetics and toiletries, and pharmaceuticals. For most of these applications UPVC is in competition with at least one other polymer, particularly poly(ethylene) terephthalate (Chapter 25), polyethylene (Chapter 10), polypropylene (Chapter 11) and, to a small extent, the nitrile resins (Chapter 15). The net result is that in recent years there has been some replacement of PPVC in these areas, in part because of problems of waste disposal. 

Copolymers of acrylonitrile and vinylidene chloride have been used for many years to produce films of low gas permeability, often as a coating on another material. Styrene-acrylonitrile with styrene as the predominant free monomer (SAN polymers) has also been available for a long time. In the 1970s materials were produced which aimed to provide a compromise between the very low gas permeability of poly(vinylidene chloride) and poly(acrylonitrile) with the processability of polystyrene or SAN polymers (discussed more fully in Chapter 16). These became known as nitrile resins. 

Table 15.4 illustrates that though the nitrile resins had a gas permeability much higher than has poly(acrylonitrile) the figures for oxygen and carbon dioxide are much lower than for other thermoplastics used for packaging. 

Table 15.4 Permeability (P) of nitrile resins compared with other polymers...

In 1984 the use of nitrile resins was re-approved by the Food and Drugs Administration with speeifie limits on the level of residual unreacted monomer. 

Another area of potential interest is in refrigerator liners. The move away from the ozone-layer-damaging chlorofluorocarbons (CFCs) to HCFCs in the USA and pentane/cyclopentane blends in Europe has not been without problems. These newer materials have an adverse effect on ABS whereas the nitrile resin appears satisfactory, if more expensive. 

Aortal Aery Me ABS Alkyd Alloy /Blands Barrier Resin CeliAwie Diallyl Phthalates Engineering Plastics Epoxies Fluorepdlymars Liquid Crystal Melamine Nitrile Resins Nylon Phenolic Polyamlde-lmide Polycarbonate polyester Polyethylene Polyimictes Polypropylene Polyurethanes PVC... 

Tests have been conducted with Monsanto high barrier nitrile resins using the common food simulating solvents (Table X) plus some typical beverages. Conditioning times and temperatures were based on applicable FDA regulations and guidelines (16). 

Exclusion Chromatography Analysis of Latex Solutions for Monitoring Nitrile Resin Polymerizations... 

Melamine formaldehyde Melamine phenolic Nitrile resins Phenolics Polyamides Nylon 6 Nylon 6/6 Nylon 6/9 Nylon 6/12 Nylon 11 Nylon 12 Aromatic nylons Poly(amide-imide)... 

Nitrile rubber (NBR), a copolymer of 1,3-butadiene with 20-40% acrylonitrile, is noted for its oil resistance. More than 150 million pounds are produced annually in the United States. Applications include fuel tanks, gasoline hoses, and creamery equipment. Nitrile resin is made by copolymerizing acrylonitrile with about 20-30% styrene or methyl methacrylate in the presence of NBR or SBR rubber to yield a blend of the graft terpolymer and homocopolymer. Applications include extruded and blow-molded containers for household, automotive, and other products as well as some nonbeverage foods (spices, vitamins, candy). 

Melamine formaldehyde Melamine phenolic Nitrile resins Phenolics... 

This section focuses on the modification of epoxy resins by blending with acrylonitrile butadiene (nitrile) resins. These are true alloyed blends since the nitrile rubber usually contains no groups that are normally reactive with epoxy groups. The nitrile molecules and the epoxy molecules intermingle as a blend to provide a single-phase alloy. If a large elastomer concentration is used, no phase separation will occur to form precipitates. 

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