SU865873A1 - Transparent sheet material based on polymetylmetacrylate - Google Patents

Description

(54) TRANSPARENT SHEET MATERIAL ON THE BASIS OF PURSENT HATTES

This invention relates to polymeric materials used to make optically transparent products and. can be used in the chemical industry and other areas of technology where a number of parts and whole units require a combination of good optical properties, impact strength and high resistance. o8an1 {1F1, aggressive media. Polymeric materials consisting of fluoroplastics and possessing the highest resistance to aggressive XO environments, are known. However, due to their crystallinity, they have poor optical properties. Polymethyl methacrylate and its modification (organic glass) 23 is the closest to the proposed material by its technical nature. 23. A disadvantage of this material is its low resistance to aggressive media, in particular, to strong acids, alkalis and oxidizers. It is a significant part of its transparency and strength due to the appearance of surface cracks. The purpose of the invention is to preserve the translucency of the product in the visible region of the spectrum when exposed to aggressive media. The goal is achieved by the fact that a transparent sheet material, based on polymethyl methacrylate, contains a surface layer 5-100 µm thick, made of polyvinylidene fluoride I or a copolymer of vinylidene fluoride with a fluorinated fatty hydrocarbon, having 2-3 carbon atoms containing 50-98 mol% links vinylidene fluoride. At this thickness, the polymer film of vinylidene fluoride and its copolymers, being duplicated with polymethyl methacrylate at 200-250 ° C, loses its ability to crystallize and remains

at room temperature in the amorphous state, thereby ensuring a high transparency of the product in the visible part of the spectrum.

The required optical properties are provided by similar refractive indices of polymethyl methacrylate and polyvinylidene fluoride (1.48-1.49 and 1.46-1.47). For etrm, the chemical resistance of the fluoroplastic is enhanced by reducing the permeability. In turn, the growth of cracks in the base layer of polymethyl methacrylate is sharply slowed down due to the presence of a fluoroplastic on the surface of the elastic layer, which together increases the strength of the material and its products.

The proposed material is processed into articles by the method of pneumatic vacuum molding according to the processing modes of poly (methyl methacrylate).

 Example 1. A sheet of polymethyl methacrylate with a thickness of 5 mm (about 650 kgf / cm; D1 3%) was duplicated at 250 ° C on both sides with a film of polyvinylidene fluoride (about 530 kgf / cm 4 180%) with a thickness of 5 μm. Destructive stress of the initial material during stretching is 670 kgf / cm2. The relative elongation at break 4.0% j after exposure to 65% nitric acid for 30 days, respectively 610 kgf / cm and 6.0%. The light transmission in both cases is at least 90%.

POLYMETHYLMETACRYLATE (PMML) plasticized with dibutyl phthalate

The same after exposure to aggressive environment

PMMA coated with polyvinylidene fluoride

The same after exposure to aggressive environment

Example 2. A sheet of polymethyl methacrylate, plasticized with dibutyl phthalate (650 kgf / cm; AJ 3.7%) with a thickness of 1 mm was duplicated at

250 C on both sides with a film of vinshshden fluoride copolymer (97-98 mol.% And tetrafluoroethylene (o 510 kgf / cm, U 250%) with a thickness of 20 µm. Breaking stress of the starting material

when stretched to not less than 650 kgf / cm, the relative elongation at break is 5%, after losing 65% nitric acid for 30 days, respectively, 600 kgf / cm and 10%. The light transmission in both cases is at least 90%. The permeability of 30 g mm / m day.

Example 3. A sheet of polymethyl methacrylate, plasticized with dibutyl phthalate, (6,630 kgf / cm-; 41 3.7%) with a thickness of 1 mm was duplicated at 200 ° C with a film of vinylidene fluoride copolymer (85 mol.% And hexafluoropropylene (d 310 kgf / cm; D1 650 %) with a thickness of 100 µm, has in the initial state about 610 kgf / cm D1 6.0%, after losing 657, - and nitric acid for 30 days, respectively

570 kgf / cm and 12%. The light transmission in both cases is not less than 9.0%.

The table presents the comparative data of testing of polymethyl methacrylate and the proposed material in the 65th nitric acid (physicomechanical characteristics of materials after environmental impact).

92

630

1.2

12

40

90

680

90

690

PMMA coated with vinylidene fluoride copolymer with tetrafluoroethylene in a molar ratio of 98: 2

The same after exposure to aggressive environment

PMMA coated with a copolymer of vinylidene fluoride with tetrafluoroethylene at an equimolar ratio

The same after exposure to aggressive PMMA coated with vinylidene fluoride copolymer with hexafluoropropylene in a molar ratio of 85 s15

The same after exposure to aggressive environment

PMMA coated with a copolymer of vinylidene fluoride with trifluoroethylene at an equimolar ratio

Also ,. eleven

PMMA coated with copolymer of vinylidene fluoride with trifluoroethylene at an immunological ratio after exposure to an aggressive environment

Also

-.- P

PMMA coated from viilidene fluoride with trifluoroethylene copolymer at a molar ratio of 25:75

The same after exposure to aggressive environment

 The coating was peeled off from PMMA.

, Table continuation

92

660

ten

92

ten

660

ten

640 6 92

i5

630 10 91

92

630

ten

88

14

600

ten

From the presented ones it is clear that the proposed material practically did not change its properties (in that translucency b} after exposure to an aggressive environment, while polymethyl methacrylate almost completely lost translucency and reduced strength by 90%.

Claims (2)

Invention Formula Transparent polymethylmethacrylate-based sheet material, characterized in that, in order to maintain translucency in the visible region of the spectrum when exposed aggressive media, it contains a surface layer of 5-100 microns thick, made of polyvinylidene fluoride or a copolymer of vinylidene fluoride with a fluorinated fatty hydrocarbon having 2-3 carbon atoms containing 50-98 mol% of vinylidene fluoride units. Sources of information taken into account in the examination . Handbook of plastic materials. Ed. V.M. Kataev and others, vol. 2, M., Khimi, 1975, p. 175 2. Handbook of plastics. Under-ed. V / M. Kataeva et al., Vol. 1, M., Himi, 1975, p. 205 (PROTOF1Sh)