Composites are very versatile materials and offer advantages in many different ways, particularly if the application requires strength and stiffness, with low weight. For the Ballistic and Defence market, laminates provide effective ballistic protection at a much lower weight than metallic armour materials. Gurit has recently developed and qualified a ballistic phenolic prepreg, which is now being introduced to the market. Composite armour works by absorbing the kinetic energy of the projectile as it passes through the laminate.

There are three distinct stages involved in the stopping of a projectile: firstly, the blunting or deformation of the projectile, secondly, the slowing phase and, thirdly, the catching of the projectile. A composite laminate is made up of multiple layers of reinforcement fibers and resin. These layers are engineered to de-laminate at the impact of a projectile. This effect greatly enhances the slowing and stopping of the projectile over other materials.

The biggest advantage of composite armour over steel is the significantly lower weight. It can be up to 50% lighter, while providing equivalent protection against projectiles. Projectiles do not need to be bullets. In fact, artillery or mortar shells, aerial bombs, grenades and antipersonnel mines are all fragmentation devices whose steel casings burst into small fragments when their explosive cores go off.

The most common form of anti-ballistic composites is made from a combination of glass reinforcement and phenolic resin. The ballistic protection properties can be enhanced by altering the fibre and resin type: stronger fibres like s2 glass increase the ballistic protection of a laminate over e-Glass by 10-20%. Similarly, stronger epoxy resin can increase the anti-ballistic performance over phenolic resin. Yet, epoxy is less desirable due to its lower fire resistance.

As engineered materials, composites are designed to meet special requirements including threat levels, weight requirements and cost restrictions. Typically, solid composite armour is made from phenolic resin and reinforcement fibres showing a resin content in the region of 18-20%. Personal armour does not need to be structurally strong, so the composite plates used are made with even lower resin content laminates (<12% by weight). Ceramic composites offer a greater level of hardness, which can deflect or blunt the projectile before stopping it by under- lining composite or steel, again this application uses a different form of composite material.

Composite armour is used in the production of military vehicles, land-based shelters, ships and aircraft. It can be used as a structural material or as secondary plate armour just for protection. The need to reduce the weight of armoured vehicles has led to a large volume of composites being used in this area. Gurit’s new ballistic phenolic prepreg Pf 700 has been developed with this in mind. It meets the first requirements and conforms to the threat levels required for this market. It is also suitable for production of flat panels in a press moulding process or for moulding more complex parts by autoclaves.

PF 700 fact file :

PF 700 is a phenolic resin system, designed for defence and industrial applications with excellent FST behavior, high temperature resistance and ballistic performance.

PF 700 can be used to manufacture monolithic and sandwich structures with cure temperatures between 120 and 160⁰C (250 and 320⁰F).

PF 700 offers flexible processing methods by press or autoclave

Features :
• Available with heavy-weight woven S and R glass
• Long shelf and shop life

• Excellent FST behaviour
• Ideal for press moulding large flat components
• 10 – 30 minute cure times at 160⁰C

Gurit’s PF700 Ballistic Protection resin has been developed internally with input from industry leads specializing in defence applications. The PF700 pre-preg has also successfully been tested by Cranfield University, Impact and Armour Group. It conforms to the requirements of the US Military specification MIL-DTL-64154B.

PRODUCT INFORMATION

PF 700 phenolic resin system is available in a range of product formats to enhance the ballistic performance of the prepreg.

PREPREG PROPERTIES
TRANSPORT & STORAGE
When stored sealed & out of direct sunlight.

All prepreg materials should be stored in a freezer when not in use to maximise their useable life, since the low temperature reduces the reaction of resin and catalyst to virtually zero. However, even at -18⁰C, the temperature of most freezers, some reaction will still occur. In most cases after some years, the material will become unworkable.

PREPREG PROCESSING
Recommended press moulding cure is 30 minutes at 160⁰C using a 2-5⁰C/min ramp-rate and 1 – 6.4bar (0.1 – 0.4 MPa) of pressure. When press moulding low resin content prepreg pressures between 7 to 16 bar are required. Alternative times and temperatures are included in the table below. Panels should be pressed to stops to gain the cured thickness required.

AUTOCLAVE MOULDING
Recommended autoclave cure using a vacuum pressure of -1bar and autoclave pressure of 5bar, using 27 plies** of material (approximately 20mm thick cured laminate).

PREPREG PROPERTIES

RESIN PROPERTIES
All data presented in this datasheet is based on the testing of a single batch of material, tested at room temperature (21⁰C + 71⁰F)

LAMINATE PROPERTIES
All data presented in this datasheet is based on the testing of a single batch of material, tested at room temperature (21⁰C + 71⁰F)

BALLISTIC PROPERTIES

Product Information on Owens Corning’s Glass Fiber product

Introduction
• A New Industry Standard
• Enhanced Corrosion Performance
• Higher Heat Resistance
• Improved Environmental Friendliness

Advantex^TM glass fiber combines the electrical and mechanical properties of traditional E-glasses with the acid corrosion resistance of E-CR glass.

Across-the-Board Properties.
Around – the – Globe Consistency

Advantex glass fiber is a new glass formulation which provides the properties and benefits customers have come to expect from Owens Corning.
An important new advantage of Advantex glass fiber is the common technology platform it provides which enables customers to confidently specify the same product anywhere in the world.
Customers currently using an E-glass product from Owens Corning can expect Advantex glass fiber to provide comparable property and processing characteristics. Advantex glass fiber also meets the defined requirements for an E-CR glass for acid corrosion resistance.
Nomenclature designations for Advantex products are structured in the same industry­ recognized formats as traditional Owens Corning E-glass and E-CR glass products.
Longer-term, the common platform will contribute to the improvement of world­ wide product availability during times when the limits of industry capacity and supply are challenged.

The Importance of Property Based Specifications
Glass fiber composites are used in more than 40,000 end-use products. In each application, it is the composite’s properties in varied operating environments, and against a diverse set of criteria, which have determined its suitability in meeting and exceeding expectations.
Advantex glass fiber combines the electrical, mechanical and other characteristics of E-glass and E-CR glass, yet it is a new glass formulation. Its specification should be based on what it does and not just its composition.
Customers can specify Aduantex glass fiber with the confidence they are receiving today’s most advanced glass fiber technology.
That’s why Owens Corning is leading an industty-wide initiative to convert glass standards from a system that classifies glass by its composition to one that classifies glass by its properties.

How Advantex compares with traditional glass fibers

The chart below shows a comparison of Advantex glass fiber physical properties with those of traditional E-glass and E-CR glass. Advantex exhibits a higher softening point than either E-or E-CR which may be an advantage for some applications.

Mechanical Property Data

Even though the ultimate properties achieved in the laboratory with single filament measurements are not normally achieved in field applications, they provide a way to compare the properties of glass prior to field processing.
A table comparing the single filament tensile strength and modulus of Advantex glass fiber vis a vis E-glass and E-CR glass is shown in the table below

Key Property Tests
In addition to its validation as a replacement for E-glass and E-CR glass, Advantex glass fiber technology continues to undergo extensive testing and further validation to define the full extent of its capabilities

Tensile Strength
The following chart shows a comparison of Advantex glass fibers with E- and E-CR glasses for typical composites containing Type 30 degree rovings

Water Durability
One of the key features of E- and E-CR glasses is their durability in water. The chart below shows that Advantex glass fiber maintains the high standards of these types of glasses.

Mechanical Property Data

Acid Resistance
Advantex glass fiber has excellent resistance to acids. Comparisons with E-CR glass in both bulk glass and laminate data in acid environments are shown in the following charts.

Electrical Properties
Although Advantex glass fiber does not contain boron as do traditional E-glasses, it exhibits comparable electrical properties. The data below shows how the critical electric properties of volume resistivity and dielectric breakdown strength compare with currently available E-glass products.

Volume resistivity is a measure of the insulating properties of the glass

Breakdown strength is a measure of the voltage which can be withstood before arcing through the material occurs.

Summary
The preceding charts indicate that Advantex glass fiber exhibits properties which compare well with E-glass in mechanical and electrical properties. They also show comparable properties to E-CR glass in acid corrosion resistance in studies to date. As a result of this combination of E- and E-CR glass properties, Advantex glass fiber spans a much broaded band of applications than either E- and E-CR glass could do alone.

For more information
In addition to the technical information covered here, if you would like more information from Owens Corning about this product, please contact us a response@elink.co.in

An excerpt from the10th Edition of the Composites Application Guide by Cook Composites and Polymers

INTRODUCTION
‘Cast Polymer products or the countertop and bath-ware industry, are used in commercial, residential, industrial, and medical areas. The cast polymer product line has extended beyond the original kitchen and bath markets. Examples of cast polymer products are vanity tops, sinks, bathtubs, shower pans, wall panels, countertops, windowsills, flooring, bar sinks, interior and exterior facades, banisters, and furniture, with the list continuing to grow. There are three distinct product lines within cast polymers:
• Cultured Marble—gel coated surface, filled with calcium carbonate, usually pigmented and/or veined, opaque in appearance.
• Cultured Onyx—gel coated surface, filled with aluminum trihydrate, usually veined with a non- pigmented background, and translucent in appearance showing depth like natural onyx.
• Cultured Granite—gel coated surface, filled with specially designed granite filler to produce a multi-colored speckled appearance.
An unlimited variety of colors, cosmetic designs, and shapes that can be manufactured or fabricated provide cast polymer products with distinct advantages over their natural counter- parts. In addition, natural products are porous (which can become a source of bacterial growth) and can easily be stained, while cast polymer products are not porous and are stain resistant.

MATERIALS
A. Gel Coat
The use of gel coat is required for cast polymer products of cultured marble, onyx, and granite, The function of gel coat is to protect the part from its environment, providing chemical resistance, water resistance, and weathering resistance (UV stability). The gel coat is also accountable for the part’s cosmetic surface and durability. It is the gel coated surface that is visible and therefore a critical aspect of the part.
Both pigmented and clear gel coats can be used to produce cast polymer products although clear gel coats are generally more popular.
Pigmented gel coats are mainly used to produce cultured marble. Clear gel coats add depth and dimension to the part. Artistic colors and designs, such as veining and granite effect of the matrix are viewed through the clear gel coat. Clear gel coat is also used to produce cultured marble where veining patterns are applied. Clear gel coat is required with onyx to accentuate the translucency and depth of the veining to more closely resemble natural onyx. Clear gel coat is also required to show off the multi-colored effect of granite filler.

Cultured granite can be manufactured using one of two methods:
1) Granite effect filler is mixed into the resin and poured behind a clear gel coat.
2) Specially designed spray granite chips are mixed with a specially designed clear gel coat, and then sprayed onto the mold. Standard marble matrix is poured behind it.
Clear gel coats used in the cast polymer industry are specifically formulated for cast polymer applications. Key differences from clear gel coats formulated for other industries are lower color and slower cure rates. Clear gel coats to be used with spray granite chips also have different viscosity and spray characteristics.
To meet performance requirements of bathware products both pigmented and clear gel coats must be based on ISO/NPG polyester resins. Please refer to Part Four Open Molding for additional information on gel coats.

B. Resin
Casting resin is mixed with fillers to make the matrix. The matrix gives the cast part its structural integrity. Resin suppliers formulate casting resins from several components including the polymer, reactive monomer, promoters, inhibitors and specialty additives. The specific components and amounts used are dictated by the end-use application, manufacturing process, required cure behavior, end-use physical properties, and requirements and manufacturing plant conditions. Plant conditions can dictate that resin gel time and/or viscosity be varied to account for seasonal temperature changes.
Unsaturated polyester polymers are the basis of casting resins. Cultured marble, onyx and granite resins are based on orthophthalic polyesters.
The monomer fulfills two roles in the polyester resin. First, it reacts and crosslinks with the unsaturation sites in the polymer to form the crosslinked thermoset material. Second, it reduces the viscosity of the polymer to workable levels. The most common monomer used in casting resins is styrene.

Promoters, also called accelerators, split the peroxide catalysts used to cure casting resins into free radicals. These free radicals attack the unsaturation sites in the polymer preparing them for reaction with the monomer. Promoters used in casting resins determine the cure behavior and also have a significant impact on finished part color. In general, the higher the promotion level the darker the cured resin color. As a result the types and amounts of promoters used in casting resins vary depending on the production speed and color require -ments for each application.
Inhibitors provide shelf life stability to casting resins as well as help control the working time or gel time. Free radicals generated in the polyester resin during storage or after addition of peroxide catalyst react preferentially with the inhibitors. Only after all the inhibitors are consumed does the crosslinking or curing process begin.
In addition to the above materials, a number of other additives can be used in casting resin formulations to affect properties. These include processing aids such as air release agents and wetting agents. Additives can also be used to affect the product’s performance such as UV absorbers and light stabilizers for weathering performance.

C. Fillers
The filler is the largest part of the cast polymer composition. The type of filler to be used depends on the cast polymer product.
1) Cultured Marble—
a) Calcium Carbonate (CaCO3)—Typical marble filler is calcium carbonate (ground limestone). CaCO3 is mined and ground into small particles; size is measured in units called mesh. Filler particles are sorted through screens with different size openings. Mesh size is designated by the number of holes per linear inch, with lower numbers indicating a coarse or large particle size, and higher numbers indicating a small or fine particle size. CaCO3 fillers are supplied as ‘all coarse’ or ‘all fine’ particles or as pre-blended bags of coarse and fine particles.
b) Dolomite—Just like CaCO3, dolomite is a mined mineral, a mixture of calcium carbonate and magnesium carbonate. It is supplied just like CaCO3. Dolomite is more abrasive than CaCO3 and therefore may require more equipment maintenance.
c) Lightweight Fillers—The use of lightweight fillers in cast polymer products has been steadily increasing. Lightweight fillers are hollow spheres made of glass (silica) or plastic. They occupy space or volume but do not add weight, which effectively reduces the weight of a given part without changing its dimensions. Lightweight fillers are used with CaCO3. They can be bought separately or pre-blended with CaCO3 to a known weight displacement. Typically, these fillers demand a higher resin percentage for wet out and to maintain a flowable viscosity. Also, because of its insulating effect, lightweight fillers cause the exotherm of the curing part to increase.
2) Cultured Onyx
a) Aluminum trihydrate (ATH)—The filler of choice for cultured onyx, ATH is a by-product resulting from the processing of bauxite minerals in the manufacturing of aluminum. Onyx grade ATH is much brighter white than CaCO3, thus eliminating the necessity of using background pigment. It is a semi-translucent granular filler which provides a visual effect like natural onyx, and has the added feature of acting as a flame retardant. At temperatures of 410°F, ATH releases its water particles, slowing combustion and reducing smoke generation.
b) Lightweight Fillers—are not recommended since this would reduce translucency.
3) Cultured Granite Granite effect fillers are also gaining in popularity. Filler suppliers have specially formulated colors and particle size distributions to achieve a multi-colored speckled granite appearance, and to give the product a cosmetic textured look. The colored granules may be coarse ground minerals or synthetically made from pigmented resins. The resin demand will vary greatly depending on the granule size(s) and distribution. There is a difference in granite effect filler mixed into the matrix versus spray granite filler mixed into the gel coat and sprayed; therefore, method of application needs to be noted when purchasing these fillers.

While inexpensive initially, if not chosen and checked properly, fillers can become extremely costly. For example, if too much coarse filler is used and subsequently settles, a resin rich area will result on the back side which could cause warpage. If too much fine filler is used, the viscosity will be very high resulting in air entrapment. If the fillers contain too much moisture or become damp, they will affect the gel and cure.

D. Catalyst/ Initiator
Catalyst is the component needed to ‘harden’ the polyester resin mix into a solid mass. Technically, catalyst causes the reaction but does not participate in the reaction. In the composites industry, the correct term is initiator, which starts the reaction and is consumed by the reaction. There are three common types of room temperature initiators used in cast polymers:
1) Methyl Ethyl Ketone Peroxide (MEKP)—The most widely used initiator, MEKP is a clear liquid that easily mixes into the resin. It is the most cost effective choice, and is available in different ‘strengths’ to give a variety of curing characteristics. Recommended range is 0.5 percent to three percent catalyst level based on resin amount.

2) 2,4-Pentadione Peroxide (2,4-PDO)—Also known as acetylacetone peroxide (AAP), this initiator offers fast cure time and high peak exotherm. Although it does lengthen gel time, Barcol hardness builds quickly. Typically, 2,4-PDO is used during the colder temperatures It is avail- able separately or pre-blended with MEKP; however, pre-blends are the most popular. In pre-blends, the MEKP controls the rate of the gel time and the 2,4-PDO provides the faster cure rate and higher peak exotherm. Recommended range is one percent to two percent catalyst level based on resin amount. Above two percent, 2,4-PDO peroxide may inhibit cure. The only disadvantage with this initiator is that with some resins, cured casting color may have a yellowish tint.
(3) Cumene Hydroperoxide (CHP)—CHP lowers peak exotherm and lengthens gel and cure times. Lower peak exotherm reduces cracking, crazing, and shrinkage but also slows down Barcol development. CHP is most popularly used during hotter temperatures and/or on thick parts like shower pans and tubs. It is available separately or pre-blended with MEKP; however, pre-blends are the most popular. Some control over gel and cure rates can be achieved by changing initiator levels and blending the above mentioned initiators.

The importance of curing new and green moulds
It is impossible to accurately measure the amount of un-reacted styrene remaining in the gel-coat or laminates of a new mould. Therefore, there is no way of knowing if the residual styrene in the mould will affect the first release. In light of this, it is ideal to post-cure a new and green mould to minimize the free styrene, which comes through the gel-coat surface during the cure of a mould. New moulds can be simply placed outside to bake in the hot sun for two to three days. This allows the majority of the free styrene in the laminates and gel-coat surface to evaporate, giving better release properties to the first few parts during the break-in period of a new mould. However, new moulds that have rested inside for two weeks can potentially have residua l styrene remaining, leading to an array of problems.
And, even a new mould that has had ten coats of wax applied to it can still experience some form of sticking because of styrene monomer burn-through if the mould is not fully cured. Considering that we do not yet have the technology to conclusively determine whether or not a mould has been built under ideal conditions, we always advise using PVA for releasing the first few parts. PVA is generally resistant to the residual styrene, which is driven up through the mould surface during the first exposure to the curing part. PVA should be applied over the mould release, which has already been applied on the surface. After the first de-moulding, the PYA should be removed with a damp cloth and reapplied along with the mould release. This procedure should be continued until all of the PVA releases cleanly from the mould and sticks on the moulded part.

Mould release categories
PVA
One of the oldest release agents used by the reinforced plastics industry, PYA is still one of the safest, most efficient, and most reliable agents for breaking in new and green moulds. PYA’s advantageous quality is that it resists being dissolved by styrene monomer, which usually vaporizes in excessive amounts during the break-in period of a new and green mould. When the PVA film completely comes off on the part, it can be discontinued and subsequently replaced with another more convenient and easy to use mould release agent.
Waxes
These were the earliest mould release agents used by the composites industry. It is for this reason that many shops prefer to have a supply of cans of hard paste wax around the shop to use for release. These old fashioned release agents have been somewhat modernized for faster and easier application, by being manufactured in paste and liquid forms. While some still have low temperature resistance others are suitable for high temperature applications. Nevertheless, be aware that many waxes have silicone added to them to promote high luster and easy application, as this is usually the reason for “fish eyes” when you spray up gel-coat. Furthermore, there is the danger of pre-release.
Polymeric mould releases
Polymer mould releases are based on fluorocarbon chemistry and include polytetrafluorethylene (PTFE). Some suppliers formulate proprietary polymericbased releases, which do not contain fluorocarbons. These types generally have a strong bond to the mould, do not transfer and offer multiple releases from a single application. Parts moulded with polymeric release agents are the easiest to achieve secondary bonding or painting without adhesion problems.

Internal mould releases
These can either be based on vegetable oils or other refined types of proprietary polymer chemistry. They are used as additives mixed with resin or gel-coats in a range of0.5% to 1.0% by resin weight. In the case of vegetable oils, the release mechanism is achieved by exudation because of complete incompatibility of the oils with the resin.

Silicones
Silicones are rarely used in their pure state as mould releases. As mentioned in the discussion of waxes, liquid mould, release products containing high amounts of silicone can cause pre-release and fish eye formation

BASIC TROUBLESHOOTING

1. Problem: Poor release, and particles from moulding material remain on the mould. Cause: Microporosity in the mould. Solution: Thoroughly clean mould, apply sealer and reapply the release. Problem: Unable to achieve multiple release. Cause: Poor release in high draft areas. Solution: Apply one to two extra coats of release in high draft areas.

2. Problem: complete release failure. Cause: Poorly cleaned mould surface prevented release from adhering to the mould or release applied improperly. Solution: Strip part, thoroughly clean the mould and ensure that release is fully cured before moulding.

3. Problem: Poor release and white patches on parts Cause: poorly cleaned mould surface prevented release from adhering to the mould or excess styrene. Solution: Thoroughly clean the mould and reapply release, reduce styrene/adjust catalyst.

4. Problem: Build-up or release agent on the mould or transfer of release to the moulded part. Cause: Over application of the release agent Solution: Thoroughly clean the mould, reapply release and carefully follow application instructions.

In the future
In the fast-paced and competitive world of composites manufacturing, engineers need to use every advantage they can get on their competitors. Quality alone is no longer what customers demand, but rather higher quality along with the ability to produce in larger quantities and at great speeds. It is therefore essential to eliminate every factor than may be slowing down production, and one of the easiest ways to remove inefficiencies is by choosing the proper mould release agent.

Whether your application requires a wax, silicone or external or internal release agent, it is important to make sure that the most effective one is selected. It is for this reason that it is essential for those in the industry producing and engineering mould releases to be careful in their research and development, and in their respective manufacturing processes. Once aware of the needs of high performance composites, you can select from the many lines, types and varieties of mould release agents – especially from those manufacturers that are constantly coming up with the new and improved ways to achieve better, faster and more efficient release performance.

Composites manufacturers always have the need to produce mass quantities quickly. The cost and amount of mould release used in daily production in this industry is relatively insignificant compared with gelcoat, resin and reinforcement. Yet, mould releases are almost always ignored by even the most sophisticated manufacturers. As many composites manufacturers eventually learn, no matter how good the mould design may be or how advanced the moulding process or resin system, it is all in vain if the mould release agent does not perform its function properly.

Effective mould release :
An effective release should have the following.
• Chemical inertness to both mould surfaces. This is essential to counter the adhesion that commonly occurs between the two surfaces. It is influenced by factors such as penetration, chemical reaction and compatibility, surface tension, and the surface configuration and polarity between two materials.
• A low surface tension so that it wets out the mould forming a continuous film.
• Insolubility.
• Heat resistance to avoid being melted by the curing or processing temperature. A strong attraction or bond to the mould surface, while having a similar
• polarity with the wet resin so that it separates easily. Adhesion is often caused by the opposing polarities of the two surfaces.
• Resistance to other factors that can cause adhesion such as high static charges, vacuum formation between two smooth and glossy surfaces or if one of the surfaces remains tacky.

Comparison of labour and raw material costs for a theoretical component

What to look for
Selecting a mould release agent with the above criteria is important, but there are other elements that should be considered. It is the moulder’s natural instinct to place all the blame on the mould release if a part sticks. However, various other conditions should be investigated before automatically condemning the release agent.

Climate: In colder climates, if the mould surface is colder than the shop temperature, there may be an earlier cure on the outside surface of the resin or gel-coat. This would leave the interface surface under-cured or tacky. In effect, this phenomenon will not only cause a significant resistance to easy release, but it may also prevent free styrene monomer from vaporizing. Further, if there is residual, uncured styrene, it could act as a solvent to dissolve the mould release film.

Delayed cure at the interface. The same styrene monomer, which is often used as a mould stripper, slowly dissolves the mould release film. Although a good mould release agent will have some resistance to the styrene, the fact remains that the longer the residence time before gelation the better the opportunity for the styrene to adversely affect the mould release film. Many shops experience sticking, most notably during the change of seasons. At this time, it may be a result of an inadequate catalyst that results in a slower, longer cure. Or, the exact opposite may be true, i.e. too quick a reaction time, which raises the exothermic temperature. A fast, hot cure can melt the wax release film if it has a low temperature tolerance, consequently causing the part to stick to the mould.

Gel time. Gelcoat and laminating resins contain a large amount of styrene and a styrene monomer can be used to strip a mould. So, whenever a gel-coat is sprayed on a mould, a potential stripping agent is applied. Therefore, it is important that the gel time is not too long. Whereas a gel time of approximately II to 20 minutes is good, a 30 to 50 minute gel time may dissolve the mould release surface because of the presence of the styrene monomer. To our knowledge, every release on the market, with the exception of polyvinyl alcohol (PVA), is soluble in styrene.

MOLD BASICS :

Why things stick
• Mould design / construction
• Porosity
• Chemical reaction at the mould face
• Under-cured resin

How mould releases Work
• Vacuum / Static attract ion chemically inert
• Good heat resistance
• Surface tension – low enough to wet-out on mould, no
interference resin flow

Selecting a mould release

• Type of resin and catalyst Process
• Type of moulds (metal or FRP)
• Temperature conditions
• Type of Parts / Special requirements
• Current mould release
• How will the release be applied?
• Who will prepare and maintain moulds?

Case Study : New release agent means less mould maintenance for RTM parts in auto manufacturing
A maker of body components for a major automotive manufacturer has successfully tested and converted to Axel’s XTEND 19 ZAM semi-permanent release for resin transfer moulding (RTM) applications. One application utilizes a tough Modar® resin to produce FRP body and chassis components. The aluminum and epoxy tooling is heated and maintained at approximately 55°C for the female cavity and 45°C for the male plug. The previous mould releasing agent used resulted in extensive mould maintenance such as dry ice blasting and compounding and buffing to prevent resin residue build-up. This process to prepare the moulds for next day production was time consuming and labour intensive. Also, after cleaning, a minimum of three coats of sealer had to be applied, followed by a minimum of three coats of the release at the moulding temperature.
According to Axel, using XTEND 19 ZAM will mean a better release performance in both open and closed mould processes. Four applications of XTEND 19 ZAM are wiped on the clean mould, with application of XTR sealer. In general a 30 minutes dry/cure time is recommended between each coat and after the final coat. The release is applied to the moulds at the moulding temperature. The parts release cleanly and easily from the moulds with a minimum of residue and scumming. Applying a light coat of the XTEND 19W between moulding ensures an even better release and reduces build-up. ln addition, because XTEND 19W does not require a sealer there are significant time savings in mould preparation. The switch to XTEND 19 ZAM has significantly decreased the labour requirements for mould maintenance, says Axel.

Comparison of raw materials and the number of parts moulded from a particular release agent

Perhaps you have already tested, or are using XTEND® 832 semi-permanent mold release, but are you aware of all of the benefits that this product has?

If you are testing or using this mold release in open molding or hand layup of polyester parts, it is important to know that XTEND® 832 is also an excellent choice for many other resins types and different molding processes including: vacuum infusion; vinyl ester gel coats; and pre-preg and wet molding of epoxy. Let’s start with the application.

The wipe-on method
For the best gloss, XTEND® 832 is applied by wipe on and wipe off method. If the weather is especially warm, work in smaller application areas, approximately 1m square, or a size that you can go back and wipe off before the release is completely dry. I prefer paper towels for wiping on, and a lightly textured cotton cloth for the wipe off, but you can decide which works best for you. I always apply in a linear motion, as illustrated here.

Each row should overlap the previous row slightly. This is the best application method since it allows you to see the release as it goes on, so you won’t miss a spot. Depending on the conditions at the molding location, the release will vary in the time that it takes to begin to show signs of evaporation. When this occurs, take the clean cotton polishing cloth and wipe in a circular motion over the area that you have applied release to. This should be done with a light soft touch, NOT hard rubbing.

The wipe-off method
After wiping over the entire application area observe your work. If the mold is not yet super glossy, turn your rag to a fresh dry side and polish lightly. This second polish should require almost no effort to create a perfect gloss surface. If you find that your wipe off is creating a cloudy or foggy appearance on the mold, simply wait a few more minutes and you will see that the polishing is now very easy.

There are two advantages to wipe-on/wipe-off products: 1) perfect application technique is not a critical as with a wipe on/let dry release 2) wiping release on and off helps to clean minor residues from the mold surface, since the mold release contains many of the same solvents that can be used to clean.

So far we have discussed XTEND® 832 primarily as it relates to the creation of high gloss gel-coated parts. However many customers use XTEND® 832 in other types of applications where good quality cosmetic parts are required, but a class “A” mirror finish is unnecessary. In these cases, XTEND® 832 can simply be wiped on and allowed to dry. These types of requirements are often present when molding epoxy, especially wet epoxy or using molds that have been polished to only 600 or 800 mesh. In these cases, save time, by just wiping on 832 and letting it dry. Large epoxy parts like wind blades or nacelle production find XTEND® 832 a product that is versatile enough to use in direct epoxy infusion and also in gel coated bagging.

Epoxy Vinyl Ester Resin – application, uses, and mechanical properties

As introduced in the previous newsletter, Derakane Momentum 411-350, an epoxy vinyl ester resin is based on bisphenol and provides resistance to a wide range of acids, alkalis, bleaches, and organic compounds for use in many chemical processing industry applications.

In this issue, let us explore the Applications and Use, Mechanical Properties, Storage and other info pertaining Derakane Momentum 411-350.

Application and Uses

This resin is suitable for fabricating FRP storage tanks, vessels, ducts, and on-site maintenance projects, particularly in chemical processing and pulp and paper operations. It is designed for ease of fabrication using hand lay-up, spray-up, filament winding, compression molding and resin transfer molding techniques, pultrusion and molded grating applications.

An alternate viscosity, optimized for some vacuum infusion processes, is available as DERAKANE MOMENTUM 411-200 resin.

Typical Mechanical Properties
The typical properties (1) of a cured casting (7) at 25⁰C (77⁰F) are detailed below

The typical properties ⁽¹⁾ of a post-cured 6 mm (1/4″) laminate (9) at 25⁰C (77⁰F) are detailed below

Storage

This resin contains ingredients which could be harmful if mishandled. Contact with skin and eyes should be avoided and necessary protective equipment and clothing should be worn.

Drums – It is highly recommended that all material is stored at stable temperatures below 25⁰C (77⁰F). Avoid exposure to heat sources such as direct sunlight or steam pipes. To avoid contamination of product with water, do not store outdoors. Keep sealed to prevent moisture pick-up and monomer loss. Rotate stock.

All things being equal, higher storage temperature will reduce product stability and lower storage temperature will extend product stability.

If you are interested in exploring more about this product, please get in touch with us at response@elink.co.in

Epoxy Vinyl Ester Resin for fabrication efficiency and product quality improvement

DERAKANE MOMENTUM 411-350 epoxy vinyl ester resin is based on bisphenol-A epoxy resin and provides resistance to a wide range of acids, alkalis, bleaches, and organic compounds for use in many chemical processing industry applications. These resins are a new generation of resins that can be used to improve fabrication efficiency and product quality.

Their lighter color makes defects easier to see and correct while the resin is still workable. The resin’s improved reactivity properties often permit an increase in the lay-up thickness per session. The longer stability provides additional flexibility to fabricators in storage and handling.

• Holds up in corrosive environments, postponing the need for equipment replacement
• Tolerates heavy design loads without causing failure due to resin damage therefore can work with large weight-bearing equipment with confidence
• Superior elongation and toughness provides FRP equipment with better impact resistance and less cracking due to cyclic temperature, pressure fluctuations, and mechanical shocks providing a safety factor against damage during process upsets or during shipping installation
• When properly formulated and cured, complies with FDA regulation 21 CFR 177.2420, covering materials intended for repeated use in contact with food.

Typical Liquid Resin Properties

Typical Curing Characteristics
The following tables provide typical

(1) geltimes for methylethylketone peroxide (MEKP).The MEKP Cure System Typical geltimes(2) using NOROX(3) MEKP-925H(4) catalyst (MEKP) and Cobalt Naphthenate-6%(5) (Co-nap6%), Diethylaniline (DEA) and 2,4-Pentanedione (2,4-P).

(2) Thoroughly test any other materials in your applications before full-scale use. Geltimes may vary due to the reactive nature of these materials. Always test a small quantity before formulating large quantities.
(3) Registered trademark of Norac Inc.
(4) Norox MEKP-925H or equivalent low hydrogen peroxide content MEKP. Use of other MEKP catalysts or additives may result in different gel times.
(5) Use of cobalt octoate, especially in combination with 2,4-P can result in 20-30% slower gel times.
(6) phr = parts per hundred resin molding compound

Note: Applications and Use, Mechanical Properties, Storage and other info pertaining to this product will be shared in the next newsletter.

A shocking number of composites manufacturers still resort to ordinary paste wax in lieu of more superior products mold release products. AXEL is a company that has manufactured high performance internal and external mold releases for more than 68 years. After great deliberation on issues with paste wax that will be highlighted in this article, Axel Plastics Research Laboratories have come up with a series of solvent based release agents for all application processes.

Let’s start with the basics. Mold preparation is serious business. It involves using a Mere paste wax will never be good enough as a replacement for these 3 functions.

Mold Cleaner : Mold preparation begins with clean molds. The requirement here is for a heavy-duty stripper that will get rid of paste wax buildup, styrene buildup and the clean build-up from non-skid coating. The image below clearly shows the difference between a dirty and clean mold surface.

AXEL CX-500
Solvent system for cleaning molds. General purpose cleaner that may be used to remove excess semi permanent release, resin residue and to prop molds before touch up with semi-permanent release.

As explained above Axel CX-500 is a solvent-based mold cleaner for use with semi permanent releases When there is a build-up of wax, styrene and impurities as shown in the above images, it results in

• Poor Release – scrapped parts damaged molds
• Poor Gloss – mold maintenance and rework or parts
• Mold Damage – downtime and repairs
• Excessive Maintenance

Mold Sealer :
Mold sealer is not the same as mold release and additional coats of release do not take the place of sealers. and a sealer is useful or recommended in most molds as tabulated below.

Axel XTEND XTR sealer is
• Solvent-based
• Wipe-On / Wipe-Off
• Easier to Polish
– greater polishing time window
– no streaking problems
• Protects Molds
• Increases Release Longevity
• Maintains Surface Gloss
• Reduces Hazing and build-up

Mold Release – Gel Coat or Gloss
Release agents are the necessary barrier between a mould and the part itself. It is so vital to the composite molding function that a mold release wax or PVA should never be preferred over a chemical release agent.

Key features of Axel Xtend 19ZAM Semi Permanent Mold Releases are in the info-pic below.

Using Axel mold release works out more economical than paste wax.

In addition to the sound technical benefits of choosing Axel over paste wax, the cost factor is also important.

• Although paste wax may appear to be more economical than a semi-permanent mold release, we must also consider how many coats of wax need to be applied before beginning to mold, and how frequently molds must be re-waxed. By comparison, a liquid semi-permanent mold release can be applied in a fraction of the time that it takes to apply wax, and a single preparation will yield many easy, perfect de-moldings.

• Other equally important factors to consider are how well mold release is performing. Have your molds lost their gloss? Do they have residue from buildup of wax or resin? Do your parts release easily, or are your molds or parts often damaged in de-molding?

If you have any of these problems these add significant costs to your business and are hardly worth the “savings” you may think you are achieving in purchasing “wax”.

For more information on Axel’s range of mold cleaners, strippers and releases,
kindly email us at response@elink.co.in

INTRODUCTION

Cores in a sandwich construction are specified by designers and architects to increase stiffness and reduce the weight of a composite structure. Gurit® is a technical leader in the development and manufacture of structural core materials. It has a range of core materials to fit any specification or manufacturing process.

As far back as 30 years ago, Gurit has made its name in the high-end race boat market. The company now supplies the full spectrum of marine projects worldwide. Production boats focusing on manufacturing efficiencies, super yachts with unique design features, small passenger boats, fishing boats and small crafts for water sports requiring robust yet low weight construction, as well as current race yacht programmes looking for cutting edge performance, are all benefiting from Gurit’s complete composite solution.

Gurit G-PET™ THERMOPLASTIC FOAM CORE
• Withstands high process temperatures
• Excellent adhesion & mechanical properties
• Excellent chemical resistance
• Recyclable
• Compatible with all types of composite manufacturing techniques
• Now benefits from ‘LITE’ surface treatment technology to reduce resin uptake
• GL and ABS certification

Gurit G-PET is used extensively in wind turbine blades, civil and marine structures. Gurit G-PET is available in sheet, grooved / perforated forms or kit-cut to customers’ desired shapes. A fire retardant version, Gurit G-PET FR, is also available.

Gurit PVCell CROSS-LINKED PVC FOAM
• Suitable for all composite sandwich applications
• Outstanding chemical resistance
• Superior strength and stiffness to weight ratio
• Excellent thermal insulation capabilities
• Self-extinguishing
• GL, DNV, RINA, BV, Lloyds and ABS certification

Gurit PVCell is an all-purpose core and can be used in decks, hull sides, bulkheads and floors.

Gurit Corecell™ THE MARINE FOAM – M FOAM
• Low resin absorption
• Good compressive strength and stiffness
• High temperature processing (prepreg compatible)
• GL, DNV, RINA, BV, Lloyds and ABS certification
• High shear strength & elongation – ideal for areas subjected to slamming loads
• Suitable for prepreg, SPRINT, infusion and wet lamination

Gurit Corecell M has been developed to deliver one product for all Marine applications. It provides a combination of high shear strength with low density, high elongation, high temperature resistance and low resin uptake. Gurit Corecell M is the perfect choice whether your application is slamming area or superstructure, hull or deck, using hand lamination, infusion or prepreg.

Gurit Balsaflex™ END GRAIN BALSA WOOD CORE
• High quality composite core material made from end grain balsa
• Highest strength to weight ratio of any structural core
• Natural, sustainable and responsibly sourced

Gurit Balsaflex is used for wind turbine blades and nacelles, marine, automotive, truck, rail and aircraft parts. Gurit Balsaflex can be supplied in sheet form or kit-cut to customer’s desired shapes.