Technical information about Material

PHYSICAL AND MECHANICAL PROPERTIES

Recently COP, which was originally developed around 1990, has been used as an optical material for parts that require high quality. COP is a polymer with an alicyclic structure synthesized using a cycloolefin as a monomer. Its main chain has a bulky cyclic structure. This polymer is amorphous and has high transparency and heat resistance. It has also outstanding environmental durability and no hygroscopic property when it is composed only of hydrocarbons. It has already been commercialized as ZEONEX® by Zeon Corporation, especially. These materials have high heat resistance and no property transformation due to moisture absorption. They are thus used in optical parts that would otherwise use poly-methyl methacrylate (PMMA). The catalyst and other impurities used in the polymer synthesis have been almost completely removed. Its transparency is outstanding even among COPs.

The major physical and mechanical characteristics are as follows:

• Low specific gravity (approximately 1.0). This is less than that of PMMA and polycarbonate (PC).
• Transparent. No absorption in the whole visible region; almost the same transmittance as PMMA.
• Low scattering. Refractive index is approximately 1.51–1.53. The wavelength dependence is relatively weak.
• Low birefringence. Outstanding birefringence performance especially to diagonal incident light compared to PC. The optoelastic constant is the same as that of PMMA.

CHEMICAL PROPERTIES

Zeonex has very low water absorption and in fact the lowest water absorption among optical plastics. Up to 60°C, it resists fairly well organic acids and diluted minerals as well as diluted alkaline solutions, and common cleaning products like acetone, methanol or iso-propanol. Its resistance to diminishing light transmission due to aging is very good. However, it must not be used with the following materials:

• Limonene
• Lipids / Fatty acids
• Oil, Hydrocarbon
• Oil, Vegetables

And it must be used with caution with Butanone and silicone oil.

ELECTRICAL PROPERTIES

Zeonex is applied to medical applications that take advantage of its high purity property, as well as to electric insulating components that require low dielectric constant and dielectric tangent.

THERMAL PROPERTIES

Zeonex has a relatively low thermal expansion coefficient, comparable as the one of PMMA. As the later, Zeonex is combustible and burns without producing an excessive amount of smoke (UL 94 HB). Depending on the particular grade, the glass transition temperature is between 123 and 156°C. This makes a much more per permissive use of Zenoex, allowing to be used in a environment with a temperature up to 100°C, even more for some grades. This is not the case for PMMA.

PRINTING AND MARKING PROPERTIES

Zeonex is suitable for both vacuum-applied metallization and silk-screening.

IMPLEMENTATION PROPERTIES 

• Injection: The peculiarity of Zeonex is that it needs a total absence of humidity and oxygen during the melting process. Thereby, a nitrogen flux system is implemented in the injection screw.
• Machining: As Zeonex very well resist to high temperature, machining is feasible on this material.

Summary by GAGGIONE SAS – April 2020

Information taken from Handbook of Plastic Optics – Editor(s): Stefan Bäumer

First published:17 February 2005

Online ISBN:9783527605125 |DOI:10.1002/3527605126 – Copyright © 2005 Wiley‐VCH Verlag GmbH & Co. KGaA

PHYSICAL AND MECHANICAL PROPERTIES

Osaka Gas Co. Ltd and Kanebo Ltd have co-developed an amorphous polyester material, OKP-4. It is now available commercially from Osaka Gas Chemical. The characteristics of OKP-4 are as follows:

• High refractive index (>1.6)
• Low birefringence

Having a slightly lower transmittance value (90 % for 3 mm thickness) than cycloolefin polymer (COP), OKP-4 is mainly used for an alternative to this latter in optical system when a higher refractive index is required. Moreover, its Abbe number, quantifying the refractive index change with the wavelength, is relatively low compared to the high value of this index (at a given wavelength). Jointly, its density is 20% more important than Zeonex, and slightly superior to PC’s and PMMA’s.

CHEMICAL PROPERTIES

OKP-4 has very low water absorption, two times less than PMMA and 30% less than PC.  Up to 60°C, it resists fairly well low concentration organic acids and diluted minerals as well as diluted alkaline solutions. Its resistance to diminishing light transmission due to aging is very good. However, as a polyester, it must not be used with the following materials at ambient temperature:

Please refer to the manufacturer or GAGGIONE for a use at a temperature superior or equal to 60 °C, in which case the chemical use is more restrictive.

ELECTRICAL PROPERTIES

Like COP, OKP-4 polyester has a low dielectric constant that makes it useable as electric insulating components.

THERMAL PROPERTIES

OKP-4 has a relatively low thermal expansion coefficient, comparable as the one of PMMA or Zeonex. As these latter, OKP-4 is combustible and burns without producing an excessive amount of smoke (UL 94 HB). Depending on the particular grade, the glass transition temperature is between 121 and 142 °C. This makes a much more per permissive use of OKP-4 than PMMA, allowing to be used in an environment with a temperature up to 100°C, even more for some grades. This is not the case for PMMA, for which the heat deflection temperature under 1.80 MPa doesn’t go above 100°C, but goes to 123 °C for a grade of OKP-4 (OKP4HT).

PRINTING AND MARKING PROPERTIES

OKP-4 is suitable for both vacuum-applied metallization and silk-screening.

IMPLEMENTATION PROPERTIES

• Injection: The very high fluidity of OKP-4 makes it easy to obtain high performance injection-molded objects and films.
• Machining: As OKP-4 very well resist to high temperature, machining is feasible on this material (diamond turning for instance).

Summary by GAGGIONE SAS

April 2020

PHYSICAL AND MECHANICAL PROPERTIES

Silicone Rubber is an elastomer composed of silicone—itself a polymer—containing silicon together with carbon, hydrogen, and oxygen. In its uncured state, silicone rubber is a highly-adhesive gel or liquid. In order to convert to a solid, it must be cured, vulcanized, or catalyzed. The optical grade of LSR is the purest one, clear and transparent. The main mechanical and physical properties and advantages of optical LSR are:

• Lighter than glass and many other plastics, keeping the overall weight of a product down (density around 1 gr/cm3).
• More flexible than glass but stiffer than other plastics, which reduces the risk of breaking, particularly when exposed to continuous vibrations or other stresses.
• It is almost as transparent as the best glass across both visible and UV spectra. Caution should be taken in powerful UV application though (less than 3 W/cm² at 365 nm).
• It does not discolor or lose transparency with age (in recommended conditions, i.e. clean and dry environment) or with exposure to heat or UV (until a certain amount).

The refractive index can be between 1.4 and 1.6, and the Shore A hardness can be chosen between 60 and 90.

CHEMICAL PROPERTIES

Water absorption is inferior to 0.1%. However, the surface is quite sticky and can become opaque due to dust, so products should remain protected if possible.  In comparison with other rubber materials, LSR is exceptionally compatible with many diluted solutions of inorganic acids and bases (e.g., acetic acid, arsenic acid, boric acid, sulfuric acid, tartaric acid). Extending the variety of uses of LSR products, such as hosing and seals, to the medical, food manufacturing, and automotive industries, LSR can be used as a propellant in food products, as filler for vehicle airbags or for silicone prototyping. The extensive list of LSR-compatible materials also includes ammonium hydroxide, ammonium phosphate, and alcohol bases, which are common ingredients of many household products. However, it should not be used with a certain amount of common chemicals. For a complete list, please refer to the manufacturer or Gaggione. On the main lines, it concerns many solvents (Acetone), oil, concentrated acids or dilute sodium hydroxide.

ELECTRICAL PROPERTIES

Silicone-based elastomers are widely used in dielectric elastomer formulation due to their favorable electro-mechanical properties. Dielectric elastomers which consist of an elastomer film with deposited electrodes on both sides have lately gained increased interest as materials for actuators, generators, and sensors.

THERMAL PROPERTIES

The main advantage of optical LSR is its incomparable resistance to high temperature (> 150°C) whereby PC (130°C) and PMMA (90°C) breakdown. The other side of the coin is that it possesses a quite high thermal expansion coefficient (3 mm expansion for a 10 °C gradient on a 1-meter bar), 5 times higher as the one of optical thermoplastics. As these latter, LSR is combustible and burns without producing an excessive amount of smoke (UL 94 HB).

PRINTING AND MARKING PROPERTIES

Optical LSR is suitable for silk-screening, but is still under tests for vacuum metallization, the issue coming from its high deformation with temperature changes.

IMPLEMENTATION PROPERTIES

• Injection: The very high fluidity of LSR, way higher than optical thermoplastics’, makes it possible for design and injection of complex parts, than can contain undercuts or micro-structures.
• Machining: The softness of silicone makes it a complicated material to machine.
• Gluing and welding: As the surface energy of silicone is very high, it is very easy to make it adhere to other materials, by plenty of means.

Summary by GAGGIONE SAS

April 2020

PHYSICAL AND MECHANICAL PROPERTIES

Polyamide 12, or also called Nylon 12, is an amorphous and transparent thermoplastic made from amino-lauric acid or laurolactam monomers that each have 12 carbons. It is manufactured and sold, among other, by the company EMS-Grivory under the name Grilamid TR. The main physical characteristics of PA-12 are as follows:

• High transparency, even with thick walled components
• Clear and light inherent color
• Very high flexural fatigue strength
• Very good toughness, even at low temperatures
• Dimensional stability and dynamic strength
• Light weight due to low density

Having a transmission equivalent to the one of PMMA and COP (Zeonex), PA-12 is a good high temperature alternative to these latter. Optically, the other link with these more classical optical plastics is the refraction index, which is around 1.50, sensitively equivalent to the one of PMMA and COP.

CHEMICAL PROPERTIES

Low water absorption and density, 1.01 g/mL, result from its relatively long hydrocarbon chain length, which also confers it dimensional stability and an almost paraffin-like structure. PA 12 is also chemical resistant and insensitive to stress cracking. However, as a polyester, it must not be used with the following materials at ambient temperature:

• Acids – Acetic / Chloroacetic / Chlorosulphonic / Chromic (80%) / Cresylic (50%) / Formic / Hydrofluoric / Nitric / Phosphoric / Sulphuric
• Aceto-acetic ester
• Antimony trichloride
• Aqua regia
• Benzaldehyde
• Bromine
• Chlorine, dry/wet
• Manganate, potassium (K)
• Phenol
• Sulphur dioxide / trioxide

Please refer to the manufacturer or Gaggione for a use at a temperature superior or equal to 60 °C, in which case the chemical use is more restrictive. Also, we do not recommend the use of alcohols, and prefer Acetone for cleaning purposes.

ELECTRICAL PROPERTIES

In the electronics field, Polyamide 12 is used for covering cables and insulating material, while in the automobile industry it is used to prepare oil and gasoline resistant tubes.

THERMAL PROPERTIES

The main and big advantage of Polyamide 12 is its high resistance in temperature. Indeed, thanks to its high glass transition temperature (155-160 °C), relatively to PMMA and even Zeonex and OKP-4, it possesses a heat deflection temperature under 0.45 MPa that can go up to 145 °C, for the TR 55 grade. PA-12 is combustible and burns without producing an excessive amount of smoke (UL 94 HB).

PRINTING AND MARKING PROPERTIES

PA-12 is suitable for both vacuum-applied metallization and silk-screening. It is for instance prepared as sheets and sintered powder for coating metals.

IMPLEMENTATION PROPERTIES

• Injection: Due to its low and mainly isotropic shrinkage, PA-12 is an easy processing material.
• Machining: As OKP-4 very well resist to high temperature, machining is feasible on this material (diamond turning for instance). Gluing: Adhesion to PA-12 is theoretically possible, in a way depending on the substrate. Ask Gaggione for more information if needed.
• Welding: Ultrasonic welding, for example, can easily weld PA-12. However, as it is hygroscopic, injected parts require drying in an oven at 60°C overnight prior to welding.

Summary by GAGGIONE SAS

April 2020

PHYSICAL AND MECHANICAL PROPERTIES

Polycarbonate is a polymer which, when uncrystallized, has excellent transparency. When thick, it has a slight yellowish tint. The index of refraction of transparent and colorless PC is very high, 1.584. The industrial grades of PC have molecular weights on the order of 20,000 to 50,000g.mol-1. The relative rigidity of the chain causes high viscosity in the liquid state.

Polycarbonate has a vitreous transition temperature of about 150°C and consequently it is to be used almost exclusively in the vitreous range (great rigidity). At ambient temperature (between Tβ= -80°C and Tg = 150°C), PC is ductile, which explains in part its very good resistance to shock. Polycarbonate has polymers.

• Little elongation relative to rupture,
• Excellent resistance to shock even when cold,
• A wide temperature range for use → sterilization possible,
• Max continuous service temperature : between 110°C and 120°C depending on the grade.
• Short term exposure : up to 135°C

CHEMICAL PROPERTIES

PC absorbs only small quantities of water (<0.6%) and its mechanical properties are not affected by it. PC can be used for making objects frequently washed with hot or sterilized water, but a long period of time in hot water (0 > 60°C) causes a decomposition resulting in a drop in shock resistance. PC is not attacked by diluted mineral and organic acids. It is insoluble in aliphatic hydrocarbons, ether and alcohol. It is partially soluble in numerous halogenous hydrocarbons.

PC is attacked by strong bases (ammonia). PC is fairly stable in the presence of ozone. Stability in UV light is not exceptional and PCs turn yellow fairly quickly. Suitability for contact with food and physiological innocuousness. PC is recognized as being suitable for making objects in contact with food. Certain grades are approved for medical use. PCs can be sterilized with steam.

ELECTRICAL PROPERTIES

Polycarbonate has good insulating properties little affected by variations in temperature or humidity.

THERMAL PROPERTIES

PC is practically self-extinguishable. Resistance to fire, rated per UL94, ranges from HB to V0-V2 according to type, wall thickness and stabilization.

DIMENSIONAL PROPERTIES

Polycarbonate, as all uncrystallized polymers, offers limited retraction when molded (<0.6%):

• Its low absorption of humidity gives it good dimensional stability in a humid atmosphere;
• PC has good creep resistance, especially when reinforced with fiber glass.

IMPLEMENTATION PROPERTIES

In a general way, PC should be carefully dried in a ventilated oven or dryer at 120° C(PC humidity < 0.02%); 0.1% humidity is enough to diminish the mechanical properties of the finished product. Injection: PC remains viscous even in the melted state and requires high injection pressures (800 to 1800 bars) or thicknesses in relation to the flow path.

Summary by GAGGIONE SAS

Information taken from MATIERE PLASTIQUE NATHAN – SEPTEMBER 2007.

Materials recommended by our engineering department and regularly used in production.

PHYSICAL AND MECHANICAL PROPERTIES

PMMA is especially known for its exceptional optical properties. This uncrystallized polymer shows remarkable transparency (92% light transmission) in the visible range from 380 to 780 nm. The angle of total reflection on an inner surface is 41 to 42° (which allows it to be used for making light “conductors”, fiber optic filament …). Its index of refraction (for λ= 587.6 nm helium) is 1.491, which makes it a material suitable for manufacturing optical products.

PMMA is an uncrystallized polymer whose vitreous transition temperature ranges from 110 up to 135°C, i.e. at ambient temperature it is hard, rigid, and brittle with little elongation. PMMA is hygroscopic and, under extreme conditions, the water absorbed will act as a plasticizer and will modify the properties of the material. Its creep is fairly limited. When critical stress is exceeded, PMMA is subject to crazing. This phenomenon is even accentuated in the presence of corrosive agents (alcohol, gasoline …). Resistance to shock is relatively low and the polymer is brittle. This resistance can be improved by adding an anti-shock agent. PMMA resists scratching to a good degree under normal conditions of use. However, when cleaned frequently or used in a dusty environment, it could be scratched. PMMAs are easily polished.

CHEMICAL PROPERTIES

PMMA is tasteless and odorless and can, in certain cases, be recognized as being suitable for use with food. Up to 60°C, PMMA resists fairly well organic acids and diluted minerals as well as diluted alkaline solutions, but it is attacked by the common products on the list in the table. Its resistance to diminishing light transmission due to aging is very good.

ELECTRICAL PROPERTIES

The electrical properties can be sharply affected by the absorption of humidity. Its resistance to arcing is excellent. PMMA is electrostatic which can spoil its appearance (attraction of dust). This drawback can be corrected by using ant-static products.

THERMAL PROPERTIES

PMMA is combustible and burns without producing an excessive amount of smoke (UL 94 HB). Its retraction when molded is small (0.4 to 0.7%) as for uncrystallized polymers. As its coefficient of linear expansion is very different from that of metals and its elasticity low, it is not advisable to use metal inserts in a part made of injected PMMA. The maximum operating temperature is low (< 85° C). Printing and marking properties: PMMA is suitable for both vacuum-applied metallization and silk-screening.

IMPLEMENTATION PROPERTIES

• Injection: The high viscosity of PMMA in the melted state requires high injection pressures (up to 1500 bars). Machining: The machining of PMMA is easy provided that shock and overheating is avoided.
• Gluing: As solvent glues release stresses, parts must be annealed (2 to 3 hrs at 80°C). PMMA is easily glued either with pure solvents (chloroform) or with PMMA dissolved in a solvent.
• Welding: PMMA can be readily welded but appearance and solidity are not as good as with gluing. Welding is limited to high-frequency, hot-gas and ultrasonic welding. PMMA shows good dimensional stability and limited retraction due to its uncrystallized structure.

Summary by GAGGIONE SAS

Information taken from MATIERE PLASTIQUE NATHAN – SEPTEMBER 2007.