5.8. Renewable Acrylics
(See also Chapter 6 for PMMA/PLA alloys)
Renewable or fossil PMMAs are thermoplastic resins.
5.8.1. Biosourced Polymers
Altuglas®/Plexiglas Rnew biopolymer resins incorporate at least 25% biopolymers produced from plant sugar leading to a lower carbon footprint. They are claimed having properties and characteristics of the same order as homologous fossil acrylics. For example, Altuglas®/Plexiglas Rnew B514 is a transparent resin for injection with high impact-resistance and good chemical resistance. Altuglas®/Plexiglas Rnew B522 transparent resin for injection is slightly less impact resistant but is higher resistant to chemicals than B514.
Altuglas®/Plexiglas Rnew are claimed offering excellent optical properties without the need for coating for suitable applications, high melt flow allowing lower temperature converting, therefore resulting in a lower carbon footprint thanks to a lower energy consumption and a good chemical resistance.
Targeted applications of Altuglas® Rnew include electronics, consumer goods, optics, and automotive, for example,
• Automotive and transportation: Windshields, glazing
• Building and construction: Urban visual communication, door canopies and balustrades, doors, windows
• Consumer goods: Household equipment, appliances, cosmetics, furniture, gift, and tableware
• Electronics and electrical: lighting, lamps
• General industry
• Medical
• Signage
• Toys.
Table 5.43 displays examples of renewable acrylic properties (Altuglas). Data cannot be used for design purposes. These general indications should be verified by consultation with the producer of the selected grades and by tests under operating conditions.
Other producers are investigating other ways. For example, Mitsubishi Rayon (https://www.mrc.co.jp/english/) studies two approaches to improve the sustainability of MMA production:
• Use of renewable feedstock resources as raw materials for existing processes;
• Development of novel routes to achieve sustainable production directly from renewable resources.
5.8.2. Reminder of Fossil-Sourced Acrylic General Properties
Partially renewable acrylics are claimed having properties and characteristics of the same order as fossil acrylics and could be processed by clients’ equipment without the need for any drastic adjustments. The following information deals with general properties of fossil acrylics and, of course, some properties of renewable acrylics can be different. So, keeping equal all the other parameters, do not make a short-sighted replacement of fossil polymer by the same weight of biosourced material without preliminary feasibility studies. Often, the recipe or/and processing conditions must be adjusted.
PMMA is the basic, main, and most representative member of the acrylics but there are also
• copolymers with styrenics: SMMA (styrene-methyl methacrylate) and MBS (terpolymer of methyl methacrylate–butadiene–styrene)
• a copolymer with imides: PMI or poly(methacrylimide), which is more heat resistant.
Table 5.43
Examples of Renewable Acrylic Properties (Altuglas)
| B514 | B522 | ||
| Melt flow index, MFI, 230°C, 3.8 kg | g/10 min | 5.5 | 6.5 |
| Yield stress | MPa | 36 | 47 |
| Yield strain | % | 3 | 3 |
| Stress at break | MPa | 36 | 33 |
| Strain at break | % | 23 | 5 |
| Charpy impact strength (+23°C) | kJ/m2 | 124 | 75 |
| Charpy notched impact strength (+23°C) | kJ/m2 | 4.7 | 3.2 |
| Flexural modulus (23°C) | GPa | 1.7 | 2.4 |
| Izod impact notched, 23°C | kJ/m2 | 5 | 4 |
| HDT A (1.8 MPa) | °C | 58 | 57 |
| Vicat softening temperature A | °C | 71 | 69 |
| Vicat softening temperature, 50°C/h 50N | °C | 62 | 62 |
| UL 94 Flame rating, 3.2 mm | – | HB | HB |
| Density | g/cm³ | 1.18 | 1.18 |
| Haze | % | 4.4 | 3 |
| Light transmittance | % | 86 | 85 |
PMMA is an amorphous and highly transparent thermoplastic copolymerized from methyl methacrylate according to two possible methods:
• In suspension: The polymer is then injected or extruded as with the other thermoplastics.
• By direct casting of the monomer or a mix of the monomer and a prepolymer. Cast goods are isotropic, free from orientation, and have excellent optical properties.
Molecular weights can be as high as 1,000,000 g/mol.
PMMA has a polar character.
Unless otherwise indicated, the following facts and figures relate to the engineering applications of fossil PMMA.
5.8.2.1. Overview
Advantages
The optical properties, transparency, brightness, stability of colors, and outstanding weathering resistance are the basic motivations for the choice of PMMA for optics and transparent parts for technical and aesthetic applications. Fair mechanical properties at room temperature, rigidity, rather low water absorption, good creep resistance, excellent electric properties (notably the arc resistance), ease of machining, and possibilities of food contact for specific grades are complementary advantages. Direct casting of the monomer or its mix with prepolymer is one of the rare liquid processing possibilities for thermoplastics.
Drawbacks
PMMA is handicapped by a low impact resistance, limited heat behavior (except for the acrylic imides), inherent flammability, sensitivity to environmental stress cracking in the presence of certain chemicals, chemical attack by certain current solvents. For some grades, processing can be more difficult than for some other current thermoplastics.
Special Grades
They can be classified according to the type of processing, specific properties, or targeted applications:
• casting, extrusion, injection, for thin or thick parts, high fluidity…
• high transparency, impact modified, heat and/or detergent stabilized; high molecular weight, better resistance to stress cracking, plasticized, high rigidity, resistant to gamma rays, food contact, physiologically inert, low warpage, abrasion resistant, reinforced, antistatic…
• for optics, clocks and watches, food industry, films, sheets, electrical applications, optical fibers…
Processing
Casting, continuous sheet casting between stainless-steel belts, pouring, and several methods in the molten state are usable: extrusion, injection, compression, thermoforming, coinjection, machining, and welding. Specific grades of PMI can be foamed.
Applications
Although varying from country to country, for an industrialized nation the total PMMA consumption can be approximately divided into the following:
• 25% for casting
• 38% for extruded sheets
• 37% for molding.
This is an example and other data can be found elsewhere depending on the source and the country.
The main application areas are as follows:
• Optical components for automotive, electronics, photography, binoculars, sunglasses, watch glasses, lenses, magnifying glasses, camera lenses…
• Transparent and decorative parts for automotive and transport:
• lenses for taillights and parking lights, rear lights…
• instrument panels, dials, indicators, tachometer covers…
• nameplates, medallions…
• warning triangles…
• Lighting, lights, lighting diffusers, light-control lenses in lighting fixtures…
• Signs: internally illuminated outdoor signs, indoor and outdoor signs, diffusers, side-lit signs, very thin illuminated displays, fluorescent signs.
• Glazing applications, shatter-resistant glazing: buildings, aircraft, boats, mass transit, architectural, and protective glazing, windows and skylights, sight glasses, sight gauges…
• Transparent thermoformed products, store fixtures and displays…
• Electrical engineering: lamp covers, switch parts, dials, control buttons, embedment of components…
• Optoelectronics: covering of displays, from small LCDs in cellular phones to large rear-projection television sets or screens designed for audiovisual presentations…
• Optical fibers…
• Office equipment: writing and drawing instruments, pens, leaflet dispensers, shower cubicles, minor office or drawing equipment, squares, rulers, telephone dials…
• Transparent technical parts: indicators, dials, inspection holes, peepholes, portholes, domes, panes, caps, casings, hoods and electrical parts…
• Civil engineering: acoustic screens…
• Transparent and decorative parts for vending machines, appliance panels, knobs and housings, housewares, piano keys, medical instruments, dust covers for hi-fi equipment, microwave oven doors…
• Furniture, knobs, small furniture…
• Arts and fashion: embedment of items, sculptures, decorative inclusions, jewels, knick-knacks…
• Medicine
• packaging for tablets, pills, capsules, suppositories, urine containers, sterilizable equipment…
• implants…
• hip prostheses…
• percutaneous (through-the-skin) PMMA vertebroplasty…
• intraocular lenses…
• membranes for continuous hemodiafiltration…
• composite cements for orthopedic surgery…
• Miscellaneous: transparent pipelines, toys, molds, models, gauges, product prototypes, demonstration models; special UV-absorbing grades for document preservation in museums and for various photographic applications; aesthetic objects; hairbrushes…
• Cast and extruded sheets, cell cast sheets, stretched sheets, films down to 50 μm used in automotive, construction, electronics, leisure, protection, communications, and sports; laminated protective surfaces on ABS, PVC, or other plastic sheets that are thermoformed into parts requiring resistance to outdoor weathering: motorcycle shrouds, recreational vehicle panels, residential siding, and transformer housings.
• Deeply formed components subsequently backed with glass fiber-reinforced polyester: tub–shower units, camper tops, furniture, and recreational vehicle bodies.
Thermal Behavior
Provided the softening temperatures are higher, the continuous use temperatures in an unstressed state are generally estimated at 60°C up to 95°C for PMMA. UL temperature indices can be as low as 50°C.
Service temperatures are noticeably lower under loading because of modulus decay, strain, creep, relaxation… For example,
• the percentage of tensile strength retained at 80°C compared to the tensile strength at ambient temperature is roughly 32% for a PMMA grade
• HDTs under 1.8 MPa range from 70°C up to 100°C for PMMA
At low temperatures, the behavior can be reasonably good, allowing applications in the automotive, civil engineering, and building sectors.
Tensile strength increases by 34% when the temperature decreases from 20°C down to −20°C.
Glass transition temperatures are roughly 90°C up to 135°C for PMMA.
These results relate to some grades only and cannot be generalized.
5.8.2.2. Optical Properties
Amorphous PMMAs are transparent with light transmittance ranging from 80% up to 92%, haze of less than 3% for a 3 mm thickness, and a refractive index of about 1.49.
These results relate to some grades only and cannot be generalized.
5.8.2.3. Mechanical Properties
The mechanical properties are generally good with a fair rigidity as long as the temperature does not rise too much. However, general purpose grades have a low impact resistance and a certain propensity to crazing under loading, which can occur in a few days under loading of about 20 MPa, for some grades. Special impact-modified grades avoid this crazing.
The abrasion resistance of PMMA depends on the roughness, type, and morphology of the opposing sliding surface. Scratch resistance can be good, notably for specific grades designed for this property. PMMA are not intended for tribological applications.
Dimensional Stability
Alterations by moisture exposure are weak; shrinkage and coefficients of thermal expansion are low, as for other amorphous polymers; creep resistance is rather good at room temperature.
Poisson’s Ratio
Poisson’s ratio depends on numerous parameters concerning the grade used and its processing, the temperature, the possible reinforcements, and the direction of testing with regard to the molecular orientation. For given samples, Poisson’s ratios are evaluated at 0.35–0.40. This is an example only and cannot be generalized.
Creep
PMMAs have medium moduli that involve medium strains for moderate loading. Consequently, creep moduli are also in an intermediate range at room temperature. When the temperature rises moderately, the creep modulus decreases significantly, as we can see in Fig. 5.28: the difference is slightly more than 40% for a temperature increase from 20°C to 50°C.
These results relate to a few grades only and cannot be generalized.
5.8.2.4. Aging
Weathering
The weathering resistance is one of the most interesting features of PMMA, along with its transparency. PMMA is inherently UV resistant and this characteristic can be further improved by addition of protective agents.
Figure 5.28 PMMA [poly(methyl methacrylate)]: examples of creep modulus (GPa) versus time (h) under 3.5 or 7 MPa at 23°C or 50°C.
Optical properties are not greatly affected by long outdoor exposures. For example, after 3-year exposure in a sunny climate, the light transmittance of given grades is superior to 90%, and the yellowing and haze are slight.
For 3-mm-thick samples exposed in the same conditions, the retention of mechanical performances can be, for example,
• 70–85% for tensile strengths
• 40–70% for elongations at break
• 70–90% for impact strengths.
These results are examples only and cannot be generalized.
Chemicals
PMMA absorbs little water and shows fair resistance at ambient and moderate temperatures. Generally, PMMA has a certain propensity to stress cracking but special grades are marketed.
Suitable grades are usable in contact with food.
Chemical resistance is generally good to limited at room temperature versus weak acids and bases, oils, greases, and aliphatic hydrocarbons.
PMMAs are attacked by strong acids, strong and concentrated bases, esters, ethers, ketones, aldehydes, aromatic and halogenated hydrocarbons, certain alcohols, oxidizing agents, and phenols.
Table 5.44 displays general assessments of behavior for given grades after prolonged immersion in a range of chemicals at room temperature. The results are not necessarily representative of all the fossil and bio acrylics. These general indications should be verified by consultation with the producer of the selected grades and by tests under operating conditions.
Table 5.44
PMMA [Poly(Methyl Methacrylate)]: Examples of Chemical Behavior at Room Temperature
| Chemical | Concentration (%) | Estimated Behavior |
| Acetic acid | 10 | S |
| Acetic acid | >96 | n |
| Acetic aldehyde | 40–100 | n |
| Acetic anhydride | 100 | l |
| Acetone | 100 | n |
| Acetonitrile | 100 | n |
| Acetophenone | 100 | n |
| Acetyl chloride | 100 | n |
| Alcohols | Unknown | n to l |
| Allyl alcohol | 96 | n |
| Alum | Solution | S |
| Aluminum chloride | Solution | S |
| Aluminum sulfate | Unknown | S |
| Ammonia liquid | 100 | n |
| Ammonium chloride | Solution | S |
| Ammonium hydroxide | 30 | S |
| Ammonium nitrate | Unknown | S |
| Ammonium sulfate | 50 | S |
| Amyl acetate | 100 | n |
| Table Continued | ||
| Chemical | Concentration (%) | Estimated Behavior |
| Amyl alcohol | 100 | n |
| Aniline | 100 | n |
| Antimony chloride | 10 | S |
| Aqua regia | Unknown | n |
| Aromatic hydrocarbons | 100 | n |
| ASTM1 oil | 100 | S |
| ASTM2 oil | 100 | S |
| ASTM3 oil | 100 | S |
| Barium chloride | Saturated | S |
| Barium hydroxide | Saturated | S |
| Beer | Unknown | S |
| Benzaldehyde | 100 | n |
| Benzene | 100 | n |
| Benzyl chloride | 100 | n |
| Benzyl alcohol | 100 | n |
| Boric acid | Unknown | S |
| Bromine (liquid) | 100 | n |
| Bromine water | Solution | l |
| Butanol | 100 | n |
| Butanone | 100 | n |
| Butyl acetate | 100 | n |
| Butylamine | Unknown | n |
| Butyl chloride | 100 | n |
| Butyraldehyde | 100 | n |
| Butyric acid | 5 | l |
| Butyric acid | 100 | n |
| Butyryl chloride | 100 | n |
| Calcium chloride | Unknown | S |
| Calcium hypochlorite | Solution | S |
| Carbon dioxide | 100 | S |
| Carbon oxide | Unknown | S |
| Carbon sulfide | 100 | n |
| Carbon tetrachloride | 100 | l to n |
| Castor oil | 100 | S |
| Cellosolve | 100 | n |
| Chlorinated hydrocarbons | 100 | n |
| Chlorinated solvents | 100 | n |
| Chlorine (dry gas) | 100 | l |
| Chlorine (wet) | Unknown | l |
| Chlorine water | Unknown | l |
| Chloroacetic acid | Unknown | n |
| Chlorobenzene | 100 | n |
| Chloroform | 100 | n |
| Chlorosulfonic acid | 100 | n |
| Chromic acid | 10–20 | S |
| Chromic acid | Saturated | n |
| Citric acid | 10 | S |
| Coffee | Unknown | S |
| Colza oil | 100 | S |
| Copper sulfate | Unknown | S |
| Cresol | 100 | n |
| Cyclohexane | 100 | n |
| Cyclohexanol | 100 | n |
| Cyclohexanone | 100 | n |
| DDT | Unknown | S |
| Decalin | 100 | n |
| Diacetone alcohol | 100 | n |
| Dibutylphthalate | 100 | n |
| Table Continued | ||
| Chemical | Concentration (%) | Estimated Behavior |
| Dibutylsebacate | 100 | l |
| Dichloroethane | 100 | n |
| Dichloroethylene | 100 | n |
| Dichloromethylene | 100 | n |
| Diethylamine | 100 | n |
| Diethylene glycol | 100 | S |
| Diethylether | 100 | n |
| Diisopropylbenzene | 100 | n |
| Dimethylformamide | 100 | n |
| Dioctylphthalate | 100 | l |
| Dioctylsebacate | 100 | l |
| Dioxan | 100 | n |
| Epichlorohydrin | Unknown | n |
| Esters | 100 | n |
| Ethanol | 30–96 | l |
| Ethyl acetate | 100 | n |
| Ethyl chloride | 100 | n |
| Ethylene dibromide | 100 | n |
| Ethylene glycol | 100 | l to S |
| Ethylene oxide | 100 | l |
| Ethylene bromide | 100 | n |
| Fluorine | 100 | n |
| Fluosilicic acid | Unknown | S |
| Formaldehyde | 37 | S |
| Formic acid | 10 | S |
| Formic acid | 85–100 | n |
| Freon 11 | 100 | l |
| Freon 113 | 100 | l |
| Freon 12 | 100 | l |
| Freon 21 | 100 | n |
| Freon 22 | 100 | n |
| Freon 32 | 100 | l |
| Fruit juice | Unknown | S |
| Fuel without benzene | 100 | l |
| Furfural | 100 | n |
| Glycerol | 100 | S |
| Heptane | 100 | S |
| Hexane | 100 | S |
| Household bleach | Unknown | S |
| Hydrobromic acid | 20–48 | S |
| Hydrochloric acid | 10 | S |
| Hydrofluoric acid | 40–100 | n |
| Hydrogen peroxide | 30 | S |
| Hydrogen peroxide | 10 V | S |
| Hydrogen peroxide | 90 | n |
| Hydrogen sulfide gas | Unknown | S |
| Iron(III) chloride | Unknown | S |
| Iron sulfate | Saturated | S |
| Isobutanol | 100 | n |
| Isooctane (fuel A) | 100 | S |
| Isopropanol | 100 | S |
| Isopropanol | 10 | l |
| Kerosene | 100 | S |
| Lactic acid | 10–90 | S |
| Table Continued | ||
| Chemical | Concentration (%) | Estimated Behavior |
| Lanoline | Unknown | S |
| Lead acetate | 10 | S |
| Lead tetraethyl | Unknown | S |
| Linseed oil | 100 | S |
| Liqueurs | Unknown | S |
| Liquid paraffin | 100 | S |
| Magnesium chloride | Unknown | S |
| Magnesium hydroxide | Unknown | S |
| Magnesium sulfate | Unknown | S |
| Manganese sulfate | Unknown | S |
| Mercury | 100 | S |
| Mercury chloride | Unknown | S |
| Methane | 100 | S |
| Methanol | 5–10 | S |
| Methanol | 50 | l |
| Methanol | 100 | n |
| Methylamine | <32 | S |
| Methyl benzoate | 100 | n |
| Methyl butyl ketone | 100 | n |
| Methylene chloride | 100 | n |
| Methyl ethyl ketone | 100 | n |
| Milk | 100 | S |
| Mineral oil | 100 | S |
| Monochlorobenzene | 100 | n |
| Monoethylene glycol (MEG) | 100 | S |
| Naphtha | Unknown | n |
| Naphthalene | 100 | l |
| Nickel chloride | Unknown | S |
| Nitric acid | 10 | S |
| Nitric acid | 65–100 | n |
| Nitrobenzene | 100 | n |
| Octane | 100 | l |
| Oleic acid | Unknown | S |
| Oleum at 10% | Pure | n |
| Olive oil | 100 | S |
| Oxalic acid | Saturated | S |
| Oxygen | Unknown | S |
| Ozone | Unknown | l |
| Pentanol | 100 | n |
| Pentyl acetate | 100 | n |
| Perchloroethylene | 100 | n |
| Petrol aliphatic | 100 | l |
| Petroleum | 100 | S |
| Petroleum ether (ligroin) | Unknown | l |
| Phenol | 90 | n |
| Phosphoric acid | ≥10 | S |
| Phosphoric acid | 85–95 | n |
| Picric acid | Unknown | S |
| Picric acid | Solution | n |
| Polish | 100 | S |
| Potassium carbonate | Saturated | S |
| Potassium cyanide | Unknown | S |
| Potassium dichromate | 10 | S |
| Potassium ferrocyanide | Saturated | S |
| Table Continued | ||
| Chemical | Concentration (%) | Estimated Behavior |
| Potassium fluoride | Unknown | S |
| Potassium hydroxide | 10 | S to l |
| Potassium hydroxide | 10–45 | S |
| Potassium hydroxide | 50 | n |
| Potassium nitrate | Saturated | S |
| Potassium permanganate | 20 | S |
| Potassium sulfite | Saturated | S |
| Potassium sulfate | Unknown | S |
| Propanol | 100 | l |
| Propylene oxide | 100 | n |
| Polyvinyl chloride (PVC) plasticized | Unknown | n |
| PVC rigid | 100 | S |
| Pyridine | 100 | n |
| Silicone oil | 100 | l |
| Silver nitrate | Saturated | S |
| Sodium bisulfite | Solution | S |
| Sodium borate | Unknown | S |
| Sodium carbonate | 10 | S |
| Sodium carbonate | 50 | l |
| Sodium chlorate | Saturated | S |
| Sodium chloride | 25 | S |
| Sodium fluoride | Saturated | S |
| Sodium hydroxide | 10 | S to l |
| Sodium hydroxide | 20–55 | S |
| Sodium hydroxide | 50 | n |
| Sodium hypochlorite | 5–20 | S |
| Sodium nitrate | Solution | S |
| Soft rubber | Unknown | n |
| Stearic acid | Unknown | S |
| Strong acids | Concentrated | l to n |
| Strong bases | Unknown | l to n |
| Styrene | 100 | n |
| Sulfur dioxide (gas) | Unknown | S |
| Sulfuric acid | 2–30 | S |
| Sulfuric acid | 50 | l |
| Sulfuric acid | 70 to Fuming | n |
| Sulfurous anhydride | 100 | S |
| Sulfurous anhydride (gas) | Unknown | S |
| Tartaric acid | Solution | S |
| Tetrachloroethane | 100 | n |
| Tetrachloroethylene | 100 | n |
| Tetrahydrofuran | 100 | n |
| Tin chloride | Unknown | S |
| Toluene | 100 | n |
| Town gas (benzene-free) | 100 | S |
| Transformer oil | 100 | l |
| Trichloroacetic acid | 10 | l |
| Trichloroethane | 100 | n |
| Table Continued | ||
| Chemical | Concentration (%) | Estimated Behavior |
| Trichloroethylene | 100 | n |
| Tricresylphosphate | Unknown | n |
| Triethanolamine | Unknown | l |
| Trimethylbenzene | 100 | n |
| Turpentine oil | 100 | S to l |
| Urea | Solution | S |
| Vegetable oil | 100 | S |
| Vinyl chloride | Unknown | n |
| Vinyl acetate | 100 | l |
| Water | 100 | S |
| Weak acids | Unknown | l |
| Weak bases | Unknown | l |
| White spirit | 100 | l |
| Wine | Unknown | S |
| Xylene | 100 | n |
| Zinc chloride | Unknown | S |
Fire Resistance
Fire resistance is naturally weak. Standard grades burn, generating flames, even after the ignition source is removed. Moreover, acrylics drip while burning.
Oxygen indices are roughly 18 up to 20 with a poor UL94 rating.
Electrical Properties
Acrylics are good insulators even in wet environments, with high dielectric resistivities and moderate loss factors. Special grades are marketed for electrical applications.
Joining, Decoration
PMMA is prone to stress cracking and contact with plasticized PVC, rubber seals, and silicone sealants must be avoided or carefully studied.
Welding is possible for certain grades by the thermal processes, high frequencies, induction, and ultrasound. The strength of the joints can be 10–40% of the PMMA used. Gluing generally gives better results.
Gluing is possible with pure solvents, monomer or chloroform, for example, or with PMMA dissolved in solvents. Preliminary tests are essential. The strength of joints can be 60–70% of the PMMA used.
All precautions must be taken concerning health and safety according to local laws and regulations.
PMMA can generally be decorated by painting, varnishing, metallization, printing with compatible materials, and processing.
5.8.2.5. Trade Name and Producer Examples
Trade name examples: Acrylite, Altuglas, Altulite, Cyrolite, Diakon, Hesalite, Oroglas, Perspex, Plexiglas, RTP acrylics, Vedril…
Producer examples
| A. Schulman | http://www.aschulman.com/ |
| Arkema | http://www.arkema.com/ |
| Arkema Cyrolite | http://www.cyrolite.com/ |
| Chimei corp | http://www.chimeicorp.com/ |
| Evonik | http://corporate.evonik.com/ |
| Mitsubishi Rayon Co | http://www.acrypet.com/ |
| Rohacell Evonik | http://www.rohacell.com/ |
| Sumitomo Chemicals | http://www.sumitomo-chem.co.jp/ |
5.8.2.6. Property Tables
Table 5.45 relates to fossil PMMA examples only and cannot be generalized. Special grades and copolymers are not considered. Data cannot be used for design purposes.
Table 5.45
Acrylics: Examples of Properties
| Cast PMMA [Poly(Methyl Methacrylate)] | Molded PMMA | Impact PMMA | ||||
| Minimum | Maximum | Minimum | Maximum | Minimum | Maximum | |
| Miscellaneous Properties | ||||||
| Density (g/cm3) | 1.17 | 1.2 | 1.17 | 1.2 | 1.1 | 1.2 |
| Shrinkage (%) | 0.2 | 0.8 | 0.2 | 0.8 | ||
| Absorption of water (%) | 0.2 | 0.4 | 0.1 | 0.4 | 0.2 | 0.8 |
| Mechanical Properties | ||||||
| Shore hardness, D | 95 | >95 | 90 | >95 | 83 | 95 |
| Rockwell hardness, M | 80 | 100 | 70 | 105 | 40 | 80 |
| Stress at yield (MPa) | 55 | 77 | 38 | 70 | ||
| Strain at yield (%) | 2 | 7 | 2 | 10 | ||
| Tensile strength (MPa) | 55 | 77 | 38 | 70 | 35 | 65 |
| Elongation at break (%) | 2 | 7 | 2 | 10 | 4 | 70 |
| Tensile modulus (GPa) | 2.5 | 5 | 2.5 | 3.5 | 1.5 | 3.5 |
| Flexural modulus (GPa) | 2.5 | 5 | 2.5 | 3.5 | 1.5 | 3.5 |
| Notched impact strength ASTM D256 (J/m) | 15 | 25 | 10 | 25 | 20 | 130 |
| Thermal Properties | ||||||
| Heat distortion temperature (HDT) B (0.46 MPa) (°C) | 75 | 115 | 80 | 110 | 75 | 100 |
| HDT A (1.8 MPa) (°C) | 70 | 100 | 70 | 100 | 70 | 95 |
| Continuous use temperature (°C) | 50 | 95 | 50 | 90 | 50 | 90 |
| Glass transition temperature (°C) | 90 | 135 | 90 | 110 | 90 | 110 |
| Thermal conductivity (W/m K) | 0.15 | 0.25 | 0.15 | 0.25 | ||
| Specific heat (cal/g/°C) | 0.35 | 0.35 | 0.35 | 0.35 | ||
| Coefficient of thermal expansion (10−5/°C) | 5 | 9 | 5 | 9 | 5 | 9 |
| Electrical Properties | ||||||
| Volume resistivity (ohm cm) | 1015 | 1016 | 1014 | 1016 | ||
| Dielectric constant | 2 | 5 | 2 | 5 | ||
| Loss factor (10−4) | 200 | 600 | 200 | 2000 | ||
| Dielectric strength (kV/mm) | 15 | 22 | 15 | 22 | ||
| Table Continued | ||||||
| Cast PMMA [Poly(Methyl Methacrylate)] | Molded PMMA | Impact PMMA | ||||
| Minimum | Maximum | Minimum | Maximum | Minimum | Maximum | |
| Fire behavior | ||||||
| Oxygen index (%) | 18 | 20 | 18 | 20 | 18 | 20 |
| UL94 fire rating | HB | HB | HB | HB | HB | HB |
| General chemical properties are subject to the compatibility of the fillers and reinforcements with the ambient conditions. If the fillers are well adapted, the chemical properties are the same for filled and neat polymers. | |
| Light | UV resistant. Special grades are marketed |
| Weak acids | Good to limited behavior |
| Strong acids | Good to unsatisfactory behavior according to the concentration |
| Weak bases | Good behavior |
| Strong bases | Good to unsatisfactory behavior according to the concentration |
| Solvents | Chemical resistance is generally good to limited at room temperature versus oils, greases, aliphatic hydrocarbons |
| PMMAs [Poly(Methyl Methacrylate)] are attacked by esters, ethers, ketones, aldehydes, aromatic and halogenated hydrocarbons, certain alcohols, oxidizing agents, phenols | |
| Food contact | Possible for special grades |
As previously said, renewable acrylics are claimed having properties and characteristics of the same order as homologous fossil acrylics and can be processed by clients’ equipment without the need for any drastic adjustments. The previous information deals with general properties of fossil acrylics and, of course, some properties of renewable grades can be different.
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