Research of high-speed cured CFRP, storage at room temperature
It was adopted as a research project of New Energy and Industrial Technology Development Organization ( NEDO ) that the topic regarding “Application research regarding high-speed cured CFRP, storage at room temperature” is researched among DIC corporation ( Tokyo, Japan ), Seiren Co., Ltd. ( Fukui, Japan ), and Industrial Technology Center of Fukui Prefecture ( Fukui, Japan).
* DIC corporation: http://www.dic-global.com/en/
* Seiren Co., Ltd.: https://www.seiren.com/english/
The press release can be read in the page below.
I would like to write about the current trend about high-speed cured thermosetting prepregs, referring the topic.
Attracted topics regarding High-speed cured FRP prepreg with long room-temperature life
I should say that current development of new type of thermosetting resin systems are very interesting
The high-speed cured resin systems seem to have been focused for past five years.
PRF composite released RP-570, which could be cured only for 4 minutes at 140 degree C, more than five years ago. You can find the brochure in the URL below.
http://www.prfcomposites.com/wp-content/uploads/2014/08/RP-570-ed.-1.0-Jul-2014.pdf
I have mentioned about RP-570 in my column as 「４分硬化の高速硬化エポキシプリプレグRP-570」( available in Japanese ) before.
There are other examples of high-speed cured resin systems like;
– Araldite(R) LY 3585 / Aradur(R) 3475（HUNTSMAN: within 2 minutes at 115 degree C / cured Tg: 105 to 115 degree C ）
– EPIKOTE(TM) Resin TRAC 06605 / EPIKURE(TM) Curing Agent TRAC 06608（HEXION: within 3 minutes at 150 degree C / Cured-Tg: 115 to 125 degree C）
But there exists another disadvantage about high-speed cured resin systems, and it should be “very short storage life” which leads to the difficulties of material quality management.
Under such circumstances, HexPly (R) M77, applied as a pillar reinforcement material of the BMW 7 series, attracted attention because the material storage life at room temperature reached 6 weeks even though the curing condition was 90 seconds at 160 degree C.
I have written a column about the topic the title of BMW 7 series への 高速硬化CFRP の適用 ( only available in Japanese ).
You may notice that the materials, introduced at the beginning of this column, have the features as below;
– Long storage life at room temperature
– High-speed cured matrix resin system
That is to say, this topic is well matched with the current trend of thermosetting FRP ( composites ).
The release material from DIC corporation, Seiren Co., Ltd., and Industrial Technology Center of Fukui Prefecture can be cured within one minute at 150 degree C. There is no explanation regarding storage life at room temperature, but this material should have more than 3 months if it is discriminated with current available materials in the market.
Anyway, NEDO has just adopted the project, so it would take more time by the material release.
What should we think about the topic?
Thermosetting is becoming advantageous to thermoplastic from the viewpoint of molding time
We needed 4 or 5 hours to complete thermosetting composite curing by autoclave before. It took more than a half hour by press molding.
I was surprised that the new composite materials could be cured only for 15 minutes, but now curing time below 3 minutes is not amazing.
We understood that the motivation to apply thermoplastic composites was “Short Molding Time”. But now this concept tells us only one aspect of the process.
The comparison at that time was based on “ Injection Molding “.
Injection molding should be one of the fastest molding process, but in many cases it is necessary to cool the mold, the molding time of thermoplastic long fibers and continuous fibers is not so short in the first place.
At the same time, the latest thermosetting curing time is now “ a few of minutes “, so the advantage of thermoplastic composite from the molding process view point is negligible small.
Molding temperature can be kept at the same temperature if the molded material is thermosetting system. This should be additional advantage of thermosetting composite materials.
Cured state of the thermosetting FRP is necessarily evaluated using chemical analysis technique
We should pay attention to the question;
“ What is the curing status?”
If you mold thermosetting composite materials, you should say quantitative evaluation answer about the curing status.
The curing condition, released from material suppliers, just mention that;
“ Materials should be cured until you can demold it. “
It is not equal to cured condition is enough for physical and/or mechanical properties. Post curing would be necessary to conduct for example.
Curing condition should be grasped by glass transition temperature, and/or exothermic peak in DSC chart, not by visual inspection.
Process design based on the quantitative evaluation by polymer analysis technology should be important point to treat thermosetting composite materials.
Does the wording that room temperature storage is possible also apply in mass production?
You may not know that 6 weeks storage life at room temperature of HexPly(R) M77 needs additional condition. For example, room temperature is sometimes very qualitative because room temperature in Russia and one in Africa should not be same. Humidity will have some impacts on the curing status.
The storage atmosphere like temperature and humidity should be controlled under some of ranges. Such process design is must in mass production.
Even though material is within storage life but curing reaction should be progressed if the temperature is over -273.15 degree C. Material suppliers concept of material storage life is not always same as users like molding suppliers.
When I have molded CFRP parts by thermosetting composite materials in house, cured condition was drastically changed between new and 1 month storage in freezers.
It is important to properly evaluate the storage conditions and periods of suitable materials within your company using chemical analysis techniques while comparing them with the results of molding processing.
High-speed curable thermosetting FRP which is being commercialized by foreign prepregs and material manufacturers.
I personally feel that I am very happy the fact that Japanese companies, retrospective to product development of this kind, are working on it.
After all, overseas is material transportation is difficult.
They have not announced what properties this material has announced at all, but I would like to wait for the market in the near future.
