Vivian Regina

[2011-01-25] Sao Paulo, Brazil

Vivian Regina Brasil, the South American subsidiary of Vivian Regina (Pty) Ltd, a South African based leading manufacturer of Chemical Resistant Fiberglass Tissues and Veils for composites industries, and PPG Industrial do Brasil, a leading global supplier of coatings, fiber glass, glass and chemicals, announced a strategic partnership to strengthen sales of Fiberglass Reinforced Paint Systems. Three weeks ago, Vivian Regina had also announced partnering with Australian Composites Pty Ltd (Australian based composites raw materials manufacturer) to distribute the Company's rapid UV Curing Prepregs (pre-impregnated fibreglass materials) into Brazil's massive automotive and transport parts convertors and assembly market.

Vivian Regina's flagship CRAKGON range of Reinforced Paint Systems will now incorporate its own brand of application paints manufactured by PPG under the present agreement, and will be marketed through the extensive PPG distribution network and franchise at a national scale.

"This investment is in line with Vivian Regina's long term strategy to create and market products that greatly enhance the performance, durability, and usability of existing solutions in all areas of the composites industry", said Mr. Jose Cruz, chairman and executive director of Vivian Regina (Pty) Ltd. "We expect to see the benefits of this cooperation and both companies believe the partnership will immediately provide great results since the fiberglass reinforced paint system addresses and overcomes many common building pathologies. The brazilian consumer is constantly looking for innovative solutions and materials to enhance their homes, and their lifestyle. CRAKGON reinforced paint systems provide proven, permanent, effective and economical solutions to common construction pathologies." Mr. Cruz added, "We are very pleased to partner with PPG Industrial do Brasil, a leader in providing high quality coatings in a very competitive market such as Brazil. We have always been very impressed with PPG's superior franchise, and dedication to deliver high quality products and services. Through this cooperation, we look forward to leveraging Vivian Regina's range of fiberglass tissues and veils, to provide unique and proven fiberglass reinforced coating systems to the vast Brazilian construction, marine and protective sectors."

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[2011-01-21] Sao Paulo, Brazil

Light curing resins have been used since the start of fiberglass composite fabrication. Light curing was the original method for curing these initial composites. With the advent of peroxide catalysts, light curing methods were abandoned. Thick part curing was not achievable with the earlier processes.  A new class of light-curing resins, which worked very well in curing thicker (1/2"+) composite laminates using Ultra-Violet light was developed and this newer class of resins has been refined to allow for a fast and complete cure. New development is ongoing and additional classes of light-curing and co-curing methods are currently under intense investigation. Additionally nontraditional methods of fabrication are being utilized with these resins, which were not able to be used with catalyst type curing systems. These new methods include Vacuum Assisted Resin Transfer Molding (VARTM), Cure on the Fly Fabrication, and Wet Edge. Most of us don't realize how much money and effort we spend, and the amount of waste usually generated in the process, to achieve consistently good laminates using catalys cure resin systems.

Manufacturing techniques using light cure resins' Cure on Demand properties
Light curing resins are Cure on Demand systems. These resins do not begin to cure prior to  the exposure to UV-A light. Standard indoor light will not cause them to cure. Sunlight and  tanning type lamps will cause the resin to cure. Based on resins that are available today the  properties of many epoxies can be duplicated with light curing vinyl ester resins. Speed of the  cure for parts as large as 16 square feet, in product runs of 10,000 or more parts per year, are  as economical as SMC or BMC systems. These light cured parts are processed on a 10-20  minute mold cycle time, using low-cost fiberglass molds. Expensive presses and steel molds  are not required for this type of production. 

When you think about using standard, thermal cure thermoset resins, the first thing that one  has to addressed is the necessary working life and cure times. How much catalyst and  promoter are required to achieve these cure rates? Will the ambient temperature remain  constant through the working life? How soon can the part be taken out of the mold? Is this a  summer or winter resin? The use of light curing thermoset resins changes all of those  perceptions. Light curing Vinyl ester, Polyester, Urethanes and Acrylic resins act and cure differently than a catalyst cured composites. These resins can be heated for lowering the  viscosity with no ill effects on the resin or the finished product. This allows a faster mold filling  time and better wet out. 

Background

Catalyst curing systems
In any system involving the catalyzed curing of polyester or vinyl ester resins the minute the  catalyst is added, (MEKP or BPO) the curing process begins. Once started the peroxide  systems cannot be stopped from going through their curing cycle. These types of catalyst  curing systems must complete an exothermic cycle in order to build the proper chemical  structures to attain the desired properties. They must reach a prescribed temperature in order  to achieve complete crosslinking.

 

In a normal laminate involving either a hand layup or wetout gun of one sort or another, the  catalyst is added on a batch or continuous basis and the laminate is usually gelling and moving  to cure within 1/2 hour after the catalyst has been added. This approach promotes enough  exotherm for the product to cure properly, but must not involve a laminate thickness so great  that a cube exotherm occurs. ("Cube exotherm" occurs in a laminate when the temperature of  exotherm raised to the point that the catalyst becomes a Super Catalyst and feeds on its own  exotherm heat instead of the promoters in the system.) Also, in a "normal laminate" the  demolding time is controlled by the ability of the resin to build strength through the chemical  reaction. The faster and closer to the ideal temperature reached, the faster the part reaches a  "Barcol" hardness high enough to demold the part. Controlling the reaction of the resin to not  be too hot and not be too cold is what proper catalization is all about, and the reason for the  equipment manufactures to build their equipment with adjustable ratio catalyst injectors. This  adjustable mechanism is what allows the fabricator to control the level of catalyst ratios  throughout the day based on changing shop temperatures. Shop temperature can change as  much as 40-70 degrees F in a single day, depending on location and as much as 70-100  degrees F seasonally. An important fact is that chemical reactions double their speed with  every 170 F rise in temperature.

The other consequence of this is that molds must be kept stabilized at constant temperature.   If the process is cooled or heated (plus or minus a few degrees) at any point after the proper  amount of catalyst is mixed into the resin for a given temperature, all estimates of cure time are  off. If the part has different thicknesses, than temperature profiles of curing will change in  different areas, with possibilities of undercure or overcure in different parts of the structure.    Although all of these problems can be overcome in a climate controlled setting, the problem of  cycle times still remains. With a room temperature cure-catalyzed resins the time from gelation  to cure can run 1- 3 hours for a catalyst cured VARTM process because of the additional time  needed for a safety factor. The part will cure to sufficient demolding strength after two times  the amount of time that it took to gel the resin. Therefore a part that took one hour for the  laminate to gel will require at least an additional two hours in the mold before it is ready to be  demolded.

The Solution is CURE ON DEMAND
Light curing resins solve many of these problems. Light curing resins are not affected by  temperature, except for viscosity, in any part of the cycle. Since light cure resins are one part  systems, the resins are used right out of the drum, with no mixing needed. Light curing resins  when cured properly will reach full heat distortion temperatures upon cure. Climate control is  not necessary. The same resin will cure as well at 00 as at 1800 F. Full cures can be easily  achieved in as little as two minutes in 1/4 inch+ part. Cure speeds are dominated by light  intensity and not temperature.

New Processes Available with Light Cure Resins

A. UV-Vacuum Assisted Resin Transfer Molding
There are a number of very similar processes called by a variety of different names which  include: The Marco Method, Vacuum Assisted Resin Transfer Molding (VARTM), Seemann  Composites Resin Infusion Manufacturing Process (SCRIMPTM), Resin Infusion under Flexible  Tooling(RIFT), Vacuum Assisted Resin Infusion(VARI), Resin Injection Recycling Method  (RIRM), LS Process and a variety of others. All of these processes are very similar in actual  processing, with only minor variations.

A chief advantage of UV-VARTM is the ability to cure on demand. This ability to cure on  demand allows the parts to be fully ready prior to curing. If any problems arise, the curing  process can be delayed until the part is ready to be cured. Due to the rapid curing the part is  under less risk of failure during the cure time of a few minutes instead of hours.

A vacuum is applied to the part and resin is drawn thru the laminate toward the vacuum port(s).  When the resin has fully saturated the materials, the resin and/or the vacuum valves are closed  and the process is complete except for curing. With a two-part resin system timing is critical.  Gel must not begin prior to completion of the saturation process.

As you can well imagine, this process is very sensitive to temperature and cure times. Using  Light curing resin and clear vacuum bags or molds, allows the fabricator to fill the laminate  without fear of premature gelation. When the laminate is fully wet out, the UV -A lamps are  turned on and the product is cured in 5-20 minutes.

B. Light curing Prepregs
Because of the cure on demand properties of the light cure resins and because they are a one  part system, prepregs can now be made using styrene monomer resins which can be stored at  room temperature for up to one year. 

C. Wet edge Concept (partial part curing)
Since light curing resins cure only under the influence of UV-A light. Portions of a laminate or  prepreg can be totally cured and other portions of the same laminate can be totally uncured.  This allows the fabricator to accomplish what we call wet edge laminations. In its simplest form  a laminate is laid down and the final 6 inches of material is covered with an opaque film. The  majority of the laminate is cured. The opaque film is removed and a new laminate is  overlapped onto the 6 inches of uncured laminate. This laminate is cured and a primary bond is  formed instead of a secondary bond. This method allows the corners of a box to be cured and  sealed after being made from a flat sheet. The laminate sees no secondary bonding or joints.  This process also works at any portion of a laminate. 

D. Filament winding and cure on the fly fabricating
Light cures are used in filament winding operations as either prepreged roving or bath wetout  systems. These filament wound parts can be cured as they are wound. This allows the  operator to remove a completed part as soon as he is finished winding the material onto the  mold. Also the quick curing of light cure resins and prepregs allows a direct fiber lay down and  cure directly from tape or fiber dispensing machines.

E. Preforms for RTM
Light curing resins are now being used in fiberglass preforms to hold multiple layers of mixed  style fabrics together for use in RTM operations using RTM tooling or VARTM tooling.  Precision cutting and proper placement of these fabrics, allows the fabricator to build net size  parts. Light curing allows these preforms to be bonded together within 20 seconds. Light cure  preforms and UV-VARTM when combined, allow medium size parts (10-30 sq ft, 1-3 M sq) to  be built economically at 10,000 + parts per year. A total cycle is less than 20 minutes per part. 

Source: Low Cost Manufacturing Processes using UV Cure Resins - Presented at Composites '97 Manufacturing & Tooling Conference Advisory Committee
  Liquid molding Session: Emerging Low Cost Manufacturing Processes for UV Cure Resins. 
Tuesday Jan 21 1:30-4:30

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