Poly methyl methacrylate properties

Properties Poly(methyl methacrylate) Cast sheet Impact- modified Heat- resistant Alkyd, molded Acrylic poly(vinyl chloride) alloy ... 

Most of the polymer s characteristics stem from its molecular stmcture, which like POE, promotes solubiUty in a variety of solvents in addition to water. It exhibits Newtonian rheology and is mechanically stable relative to other thermoplastics. It also forms miscible blends with a variety of other polymers. The water solubiUty and hot meltable characteristics promote adhesion in a number of appHcations. PEOX has been observed to promote adhesion comparable with PVP and PVA on aluminum foil, cellophane, nylon, poly(methyl methacrylate), and poly(ethylene terephthalate), and in composite systems improved tensile strength and Izod impact properties have been noted. 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

T is the glass-transition temperature at infinite molecular weight and is the number average molecular weight. The value of k for poly(methyl methacrylate) is about 2 x 10 the value for acrylate polymers is approximately the same (9). A detailed discussion on the effect of molecular weight on the properties of a polymer may be found in Reference 17. 

Electrical Properties. Poly(methyl methacrylate) has specific electrical properties that make it unique (Table 4). The surface resistivity of poly(methyl methacrylate) is higher than that of most plastic materials. Weathering and moisture affect poly(methyl methacrylate) only to a minor degree. High resistance and nontracking characteristics have resulted in its use in high voltage appHcations, and its excellent weather resistance has promoted the use of poly(methyl methacrylates) for outdoor electrical appHcations (22). 

Table 4. Electrical Properties of 6.35-mm Thick Poly(methyl methacrylate) Sheet ...

Plastic Sheet. Poly(methyl methacrylate) plastic sheet is manufactured in a wide variety of types, including cleat and colored transparent, cleat and colored translucent, and colored semiopaque. Various surface textures ate also produced. Additionally, grades with improved weatherabiUty (added uv absorbers), mat resistance, crazing resistance, impact resistance, and flame resistance ate available. Selected physical properties of poly(methyl methacrylate) sheet ate Hsted in Table 12 (102). 

Optics. Good optical properties and low thermal resistance make poly(methyl methacrylate) polymers well suited for use as plastic optical fibers. The manufacturing methods and optical properties of the fibers have been reviewed (124) (see Fiber optics). Methods for the preparation of Fresnel lenses and a Fresnel lens film have been reported (125,126). Compositions and methods for the industrial production of cast plastic eyeglass lenses are available (127). 

Polymethacrylates. Poly(methyl methacrylate) [9011-14-7] is a thermoplastic. Itis the acryUc resin most used in building products, frequendy as a blend or copolymer with other materials to improve its properties. The monomer is polymerized either by bulk or suspension processes. Eor glazing material, its greatest use, only the bulk process is used. Sheets are prepared either by casting between glass plates or by extmsion of pellets through a sHt die. This second method is less expensive and more commonly used. Peroxide or azo initiators are used for the polymerization (see Methacrylic polymers). 

Hard lenses can be defined as plastic lenses that contain no water, have moduli in excess of 5 MPa (500 g/mm ), and have T well above the temperature of the ocular environment. Poly(methyl methacrylate) (PMMA) has excellent optical and mechanical properties and scratch resistance and was the first and only plastic used as a hard lens material before higher oxygen-permeable materials were developed. PMMA lenses also show excellent wetting in the ocular environment even though they are hydrophobic, eg, the contact angle is 66°. 

Property Poly(methyl methacrylate) Vinvl acrylic s... 

Today a very wide range of acrylic materials is available with a broad property spectrum. The word acrylic, often used as a noun as well as an adjective in everyday use, can mean quite different things to different people. In the plastics industry it is commonly taken to mean poly(methyl methacrylate) plastics, but the word has different meanings, to the fibre chemist and to those working in the paint and adhesives industries. Unless care is taken this may be a source of some confusion. 

The average molecular weight of most bulk polymerised poly(methyl methacrylates) is too high to give a material which has adequate flow properties for injection moulding and extrusion. 

The properties of three types of poly(methyl methacrylate) (sheet based on high molecular weight polymer, lower molecular weight injection moulding material and a one-time commercial copolymer) are given in Table 15.1. 

Table 15.2 Some properties of a methyl methacrylate-acrylonitrile copolymer compared with a general purpose poly(methyl methacrylate) compound at 23°C and 50% R.H (German DIN tests)...

A large number of methacrylate polymers have been prepared in addition to poly(methyl methacrylate). In many respects the properties of these materials are analogous to those of the polyolefins described in Chapter 8. 

The important features of rigidity and transparency make the material competitive with polystyrene, cellulose acetate and poly(methyl methacrylate) for a number of applications. In general the copolymer is cheaper than poly(methyl methacrylate) and cellulose acetate, tougher than poly(methyl methacrylate) and polystyrene and superior in chemical and most physical properties to polystyrene and cellulose acetate. It does not have such a high transparency or such food weathering properties as poly(methyl methacrylate). As a result of these considerations the styrene-acrylonitrile copolymers have found applications for dials, knobs and covers for domestic appliances, electrical equipment and car equipment, for picnic ware and housewares, and a number of other industrial and domestic applications with requirements somewhat more stringent than can be met by polystyrene. 

Mechanical properties are typical of a rigid plastics material and numerical values (Table 30.2) are similar to those for poly(methyl methacrylate). Although thermosetting, it has a low heat distortion temperature ( 80°C) and is not particularly useful at elevated temperatures. 

An example of this improvement in toughness can be demonstrated by the addition of Vamac B-124, an ethylene/methyl acrylate copolymer from DuPont, to ethyl cyanoacrylate [24-26]. Three model instant adhesive formulations, a control without any polymeric additive (A), a formulation with poly(methyl methacrylate) (PMMA) (B), and a formulation with Vamac B-124 (C), are shown in Table 4. The formulation with PMMA, a thermoplastic which is added to modify viscosity, was included to determine if the addition of any polymer, not only rubbers, could improve the toughness properties of an alkyl cyanoacrylate instant adhesive. To demonstrate an improvement in toughness, the three formulations were tested for impact strength, 180° peel strength, and lapshear adhesive strength on steel specimens, before and after thermal exposure at 121°C. 

J.H. Grezlak, The Preparation and Physical Properties of Polyester-Poly(Methyl Methacrylates) Triblock Copolymers , TR for Jan 1— March 1, 1975, Contract N00014-67-A-0151-0011. Princeton Univ, Princeton (1975)... 

Siloxane containing interpenetrating networks (IPN) have also been synthesized and some properties were reported 59,354 356>. However, they have not received much attention. Preparation and characterization of IPNs based on PDMS-polystyrene 354), PDMS-poly(methyl methacrylate) 354), polysiloxane-epoxy systems 355) and PDMS-polyurethane 356) were described. These materials all displayed two-phase morphologies, but only minor improvements were obtained over the physical and mechanical properties of the parent materials. This may be due to the difficulties encountered in controlling the structure and morphology of these IPN systems. Siloxane modified polyamide, polyester, polyolefin and various polyurethane based IPN materials are commercially available 59). Incorporation of siloxanes into these systems was reported to increase the hydrolytic stability, surface release, electrical properties of the base polymers and also to reduce the surface wear and friction due to the lubricating action of PDMS chains 59). 

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