Acrylic glass mold performs as the mold for Cell Casting Process in order to produce acrylic sheet. How does Acrylic Glass Mold work?
Cell Casting Process is performed by the water bath technique and Acrylic liquid (MMA) is poured into a mold, typically constructed from two tempered glass sheets separated to produce the desired thickness of the sheet.
Sheet is produced by three techniques, each method influencing
the sheet’s properties, pricing and end use application.
1. Cell casting is the polymerization of catalyzed monomer between glass plates and has the highest molecular weight and the best overall properties.
2. Continuous cast is the polymerization of catalyzed monomer between moving steel belts. It has a lower molecular weight
3. Extruded sheet is resin or polymer extruded into sheets. This has the lowest molecular weight but also the lowest cost.
Methyl Methacrylate and Specialty Methacrylates; MMA and SpMAs
MMA is the abbreviation of substance of methyl methacrylate, is a monomer for polymers.
SpMAs is the abbreviation of substance methacrylates, specialty monomers for offering the polymer some unusual properties. For example: methacrylic acid, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, hydroxy methacrylate, ethylhexyl methacrylate.
The Application of MMA and SpMAs
MMA and SpMAs can be polymerized into polymers and copolymers, in forms of sheet, pellet, powder, solution, and latex. The middle product then can be processed into miscellaneous final products, such as: advertisement board, decorative panel, optical lense, optical fiber, paint, lacquer,adhesive, etc.
The Characteristics of PMMA/ PspMAs
Very high transparent, Excellent weather resistance, Very good UV resistance
The Production of PMMA
PMMA sheet can be easily produced by cell cast or in a reactor and then a extruder. For example, when a PMMA sheet is produced by cell casting process, a syrup comprised of MMA and oligomer and polymer, was filled into the sealed cell, and then cured and post-cured following a pre-setted thermal procedure.
After cooling the cured sheet, the PMMA was obtained in sheet form. Another way to have a PMMA sheet is via the extrusion technique. PMMA pellet is conveyed into a extruder, then compounded, and pulled out in sheet form
Definition of Monomer and Polymer
A monomer is any substance that has low molecular weight and can be converted into a polymer. For example, methyl methacrylate (MMA) is a monomer that can be polymerized into poly(methyl methacrylate), PMMA.
A polymer is any substance that has high-molecule-weight. For example, the PMMA formed from cell cast process has a molecular weight about 1000K, and which from extrusion has molecular weight less than 1000K.
What Is Acrylics
By chemical definition, Acrylics represent all the chemicals of acrylate/methacrylate monomers and their derivatives. Among many monomers in the methacrylate family, the most commonly heard is methyl methacrylate. It is the prime element that is used through polymerization to produce acrylic sheets, pellets, bead and resin, which are all referred to as "Acrylics" in the current plastic market and are suitable for various applications.
Organic Glass and Acrylic Sheet
In some countries, organic glass represents any kind of transparent plastic product including acrylic sheet. To differentiate from other transparent polymers, the term, "Acrylic Sheet", is specifically used to describe Polymeric Methyl Methacrylate (PMMA) sheet.
Features of Acrylic Sheet
Acrylic sheet, including those of high thickness, has distinguishing characteristics of high light transmittance (up to 92%) and superior outdoor weatherability. It possesses high gloss and surface hardness and is easy to fabricate and thermoform. The sheet is also chemical resistant and is available in many attractive colors including translucent ones.
It was during the mid 1920 that the German firm, Rohm & Haas, first uncovered a means to polymerize the water-like methyl methacrylate (MMA) monomer to solid PMMA sheet in laboratory.
It was during the mid 1920 that the German firm, Rohm & Haas, first uncovered a means to polymerize the water-like methyl methacrylate (MMA) monomer to solid PMMA sheet in laboratory.
In 1931, an ICI chemist called John Crawford, who discovered an economic process route to MMA based on acetone, hydrogen cyanide, sulfuric acid and methanol with some modifications, ICI scaled up process in 1937 and it remains to this day one of the main routes to the large scale manufacture of MMA (ACH route).
In 1936, ICI in Darwen, UK started to make cell cast acrylic sheet and the sheet was used for canopy of fighter plane.
Chi Mei in Taiwan had its cast sheet production in 1957 by introducing Japanese technology and bloom the Taiwan acrylic industries including downstream. Its PMMA pellets production was on line in 1989 with capacity of 60 ktpa.
Joined venture by ICI and CPDC ( China Petroleum Development Company ), KMC ( Kaohsiung Monomer Company ) was established on 1976 for manufacturing MMA in Taiwan and play as a major supplier in Asia pacific region.
In 1982, Nippon Shokubai of Japan start new process of making MMA by C4 route rather than ACH route.
Light transmission and low haze are some of the best assets of acrylic, and it exceeds the optical clarity of any thermoplastic competitor. Equally distinguishing for acrylic in the competitive arena is its excellent weathering properties. Acrylic easily outperforms the competition in end-use environments which include out-door exposure to sunlight, humidity, and temperature changes. Outstanding resistance to ultra-violet light and resistance to crazing after thermal cycling sets acrylic apart for lighting applications.
Mechanical properties:
Higher impact resistance - breakage resistance 6-17 times greater than window glass.
Optical Properties:
Excellent optical clarity and complete transparency of 92% which is equivalent to the best optical glass.
Thermal properties:
Good low temperature characteristics.
Environmental properties:
Excellent long-term resistance to weathering and sunlight. Resistant to weak acids and alkalis, aliphatic hydrocarbons and most detergents and cleaning fluids. Low water absorption.
Processing and finishing:
Can be cast as sheet and thermoformed; injection moulding, extrusion. Excellent dimensional and tolerance stability. Able to accept decorative paints, lacquers and metallic deposits. Can be solvent cemented.
PMMA compared with other materials
Property
Units
PS
PC
PMMA
t-PMMA (Impact)
PETG
Tensile
GPa
3.2
2.78
3.2
2.4
1.96
Tensile Strength
MPa
72
72
75-85
58
48
Unnotched Impact
kJ/m2
10
---
18-26
60
---
Notched Impact
kJ/m2
3.3
176
1.7-2.2
7.7-25
33
Thermal
Property
Units
PS
PC
PMMA
t-PMMA (Impact)
PETG
Glass Transition Temperature
Degree
80-90
149
108
108
81
Melting Temperature
Degree
240
270
230
235
180
Processing Temperature
Degree
204
290
245
245
280
Continuous Service
Degree
82
132
85
80
65
Thermal Degradation Temperature
Degree
290
>300
310
310
Optical
Property
PS
PC
PMMA
t-PMMA(Impact)
PETG
Transmission (%)
90
90
92.5
91
90
Haze
2
0.5
2
2
Yellowness
2
0.7
2
2
Weatherability
Property
PS
PC
PMMA
t-PMMA(Impact)
PETG
Yesslowness Index
2
0.7
2
2
Yellowness Index
(2000 hours UV)
Very Poor
9.2
1
1.2
Poor
Weathering
Poor
Poor
Very Good
Good
Poor
UV Resistance
Impact Resistance
Processability
Chemical Resistance
Scratch Resistance
Optical Properties
PMMA
Excellent
Fair
Good
Good
Excellent
Excellent
PC
Fair
Excellent
Poor
Poor
Moderate
Good
PS
Poor
Good
Poor
Excellent
Fair
Fair
PETG
Fair
Good
Poor
Excellent
Fair
Fair
ABS
Poor
V.Good
Mpderate
Fair
Poor
N/A
PVC
Poor
Good
Good
Moderate
Poor
Fair
Tolerance of Thickness
Thickness
%
Tolerance
Thickness
%
Tolerance
2.0m/m
15
1.7~2.3
13.0m/m
8
12.0~14.0
2.5m/m
12
2.2~2.8
15.0m/m
8
13.8~16.2
3.0m/m
12
2.6~3.4
16.0m/m
8
14.7~17.3
4.0m/m
10
3.6~4.4
18.0m/m
7
16.7~19.3
4.5m/m
10
4.0~5.0
20.0m/m
7
18.6~21.4
5.0m/m
10
4.5~5.5
25.0m/m
6
23.5~26.5
6.0m/m
10
5.4~6.6
30.0m/m
6
28.2~31.8
8.0m/m
10
7.2~8.8
38.0m/m
6
35.7~40.2
10.0m/m
10
9.0~11.0
44.0m/m
6
41.3~46.6
12.0m/m
8
11.0~13.0
50.0m/m
7
46.5~53.5
Acrylic sheet standards and testing in related countries
US, ASTM D-4802, Standards specification for acrylic sheet
Taiwan, CNS 2228, Methylacrylate Sheet for General Purpose
Taiwan, CNS 2229, Test methods of Methylacrylate Sheet for General Purpose
MMA monomer can be polymerized by free radical polymerization by route of bulk,suspension, solution and emulsion polymerizatin. Acrylic sheet can be by cell cast and extruded.
Polymerization Processes
Suspension Polymerisation
-Polymerisation in water followed by recovery
Solution Polymerisation
-Polymerisation in organic solvent + recovery
Bulk Polymerisation
-"Boil in the bag technology
Sheet Manufacturing Methods
Traditional Casting
-MMA to Syrup then cast between glass sheets and cured in waterbath and air oven.
Extrusion
-PMMA pellets.
Continuous Casting
-MMA to syrup then cast onto moveable stainless steel bands.
Sheet & Polymer:
Acrylic offers a number of outstanding characteristics including optical clarity, light in weight, weather resistance, high impact resistance and high formability. Apart from other formation processing of casting, mechanical work and heat formation, projecting through molding is the most common processing to bring in mass production yet with lowest cost. As a result of continuous improvement on the equipment and technical know-how in these years, there are increasing performance of acrylic products on both quality and quantity which has widen its application in every field of industry and hence human life. One example is to use acrylic in LCD as light transmission material for monitor.
Stationery & Gifts
Office supplies, educational appliance, name card/memo case, pen holder, adhesive tape holder, general gifts, art works, designer¡¦s master piece, photo frame, trophies, laser engraving, clock, key ring and etc.
Kitchenware/Vanities/Household Supplies
Kitchenware, tableware/cup, vanity unit, bathtub, shower partition, SPA, home swimming pool, tray, candy box, wine rack, ice bucket, egg rack, vanity case, glass mat, CD rack, tissue case, tidy, mirror and designer's master piece.
Building materials/Decoration
Rolling door, window, screen, partition, handle & knob, bar, floor, hand rail & balustrade, guardrail, showcase, canopy, sun (rain) shelter, mirror sheet, shop window, landscape, landmark, noise barrier, bullet-proof protection, defensive, paints and adhesives.
Greenhouse, harvest case, medical supplies, agriculture supplies.
Other Miscellaneous
Machinery, fabrication auxiliaries and others.
General care of acrylic products
1. Cleaning
Being apt to be scraped out, acrylic products in normal case would only require gentle cleaning by duster or with fresh water and wipe dried by soft cloth materials. For oily removal, soft detergent to be applied to bring better effect.
2. Waxing
Polish with liquid wax to bring sparkling light.
3. Adhesion
Use adhesives that contain IPS Cements/Adhesives , dichloromethane or instant dry adhesives to mend the broken parts.
4. Polishing
Apply polisher that equipped with coat wheel (or car waxing machine) and proper liquid wax to improve the scraped surface of acrylic products.
After 60 years development, acrylic product had contributed on improving and diversifying the people life.
In view of future development, acrylics will play more important by
diversifying the products ranges with multifunctions and applications.
For example, thicker sheet, functional sheet of impact modified,
anti-static, scratch-resisted and colorful translucent sheet.
Optical and electronic applications will be continued to carry on playing in role of LCD industry,
optical fiber and lens.
