Epoxy Resin Chemistry II - American Chemical Society

7 High Performance Tris(hydroxyphenyl)methaneBased Epoxy Resins

Downloaded by NORTH CAROLINA STATE UNIV on May 6, 2015 | http://pubs.acs.org Publication Date: June 8, 1983 | doi: 10.1021/bk-1983-0221.ch007

K. L. HAWTHORNE and F. C. HENSON Dow Chemical Company, Resins TS&D, Freeport, TX 77541

Epoxy resins based on the triglycidyl ether of tris(hydroxyphenyl)methane isomers and higher oligomers are multifunctional resins with improved thermal oxidative stability over other types of epoxy resins. They will help close the gap between phenol/formaldehyde novolac epoxies and higher temperature engineering plastics. When cured, these experimental tris(hydroxyphenyl)methane-based epoxies form a three-dimensional, tightly crosslinked structure with a high aromatic content and a very high heat distortion temperature. Initially, two experimental epoxy resins have been identified using this chemistry. Experimental Semisolid Epoxy Resin XD-7342.00L is aimed at high performance composites and adhesives where requirements include toughness, hot/wet strength and long-term high temperature oxidative resistance. Experimental Solid Epoxy Resin XD-9053.00L fits into the semiconductor molding powder industry where requirements include purity, formulated stability, fast reactivity and electrical properties over a broad temperature range. Epoxy resins are versatile materials used in applications ranging from sand-filled floorings and two-part adhesives to aerospace composites and semiconductor encapsulation packages. They have gained acceptance over the past two decades by performing in many areas where other materials fail or are not cost-competitive. Properties like chemical resistance, toughness, adhesive strength, electrical insulation, heat and oxidation resistance and dimensional stability combine with a long l i s t of processing techniques which made epoxy resins a 300 M"lb/yr industry in the U.S. in 1980. Bisphenol A-based 0097-6156/83/0221-0135$06.00/0 © 1983 American Chemical Society

In Epoxy Resin Chemistry II; Bauer, R.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

EPOXY RESIN CHEMISTRY


136

epoxies account for the majority of this volume and perform well at temperatures up to slightly over 100°C. Novolacbased epoxy resins add utility at significantly higher temperatures. However, there is a considerable gap between high performance epoxy novolacs and other higher temperature materials such as silicones and polyimides which also carry much higher price premiums. The latest candidate to f i l l this need is a series of experimental epoxy resins based on the triglycidyl ether of trisihydroxyphenyl)methane (patent pending) isomers and higher oligomers (from The Dow Chemical Company U.S.A.). The tri functionality of this resin results in a three dimensional, tightly crosslinked structure with a very high heat distortion temperature and improved thermal oxidative stability over other types of epoxy resins. Initially, two experimental epoxy resins have been identified using this chemistry and are currently manufactured in semicommercial quantities. Experimental Semisolid Epoxy Resin XD-7342.00L is aimed at advanced composites and adhesives where performance requirements include toughness, hot wet strength and long-term high temperature oxidative resistance. Experimental Solid Epoxy Resin XD-9053.00L fits into the semiconductor molding powders industry where resin requirements include purity, formulated stability, fast reactivity and excellent electrical properties over a broad temperature range. This paper presents data generated to characterize the physical properties of trisihydroxyphenyl)methane-based epoxy resins. Resin and cured clear casting physical properties, electrical properties, moisture resistance, formulated stabil i t y , reactivity and retention of properties at elevated temperature are covered compared to other selected resins. Experimental Liquid Physical Properties. Table I lists typical resin physical properties for XD-7342.00L and XD-9053.00L and the lower epoxide equivalent weight of XD-7342.00L agrees with its relatively lower viscosity. This suggests that XD-9053.00L contains a considerably larger fraction of higher molecular weight oligomers and that XD-7342.00L is predominantly the lower molecular weight triglycidyl ether of trisihydroxyphenyl)methane. The lower viscosity of XD-7342.00L makes i t suitable for adhesives and advanced composites where proper adhesive flow and composite reinforcement wetting become very difficult at high viscosities. The solid XD-9053.00L handles nicely in formulating semiconductor molding compounds where a nonsintering, crushable solid resin handles best. Table I also shows the higher purity of XD-9053.00L. Purity is a must for semiconductor encapsulation where contaminants combine with moisture and corrode



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High Performance Epoxy Resins

TABLE I

TYPICAL LIQUID RESIN PROPERTIES OF EXPERIMENTAL EPOXY RESINS XD-7342.00L AND XD-9053.00L

PROPERTY EPOXIDE EQUIVALENT WEIGHT SPECIFIC GRAVITY, 25°C

XD-7342.00L

XD-9053.0QL

162

220

1.22

1.22

55

550

VISCOSITY (CENTISTOKES) 150°C 60°C

14,000

DURRAN'S SOFTENING POINT, °C

55

85

VOLATILES, WT. % MAX.

1.0

0.5

HYDROLYZABLE CHLORIDES, WT. % MAX.

0.1

0.05

IONIC CHLORIDE, PPM MAX

10

5

SODIUM, PPM MAX.

15

5


138



parts of the electronic device which leads to premature device failure. Extremely high purity is not so critical in composites and adhesives unless the contaminants begin to interfere with cure which typically happens at much higher levels than those reported in Table I. Clear Casting Physical Properties. Unreinforced clear casting physical property data using nadic methyl anhydride as a curing agent is in Table II. Immediately evident is the increase in heat distortion temperature (HDT) using the tris(hydroxyphenyl)methane-based resins compared to both phenol and cresol-based novolac epoxies. XD-9053.00L and XD-7342.00L also maintain a higher percentage of their room temperature strength at elevated temperature. Electrical properties at ambient and elevated temperatures measured according to ASTM-D257 and ASTM-D150 are also reported in Table II. As one can see, tri s(hydroxyphenyl)methane-based epoxy resins maintain electrical insulation properties over a wide range of temperatures. Table III lists clear casting data for XD-9053.00L compared to solid cresol epoxy novolac resin using a solid phenolic curing agent. A trend similar to the anhydride-cured systems in the preceding table is evident. XD-9053.00L has a higher HDT and a correspondingly greater percent retention of physical properties at elevated temperature. Electrical properties of both systems are comparably good over the temperature range tested; however, the greater strength retention of XD-9053.00L should allow its use at considerably higher service temperatures. Thermal Resistance. Additional technical data was gathered using several Du Pont instruments including: Thermogravimetric Analyzer (TGA), Differential Scanning Calorimeter (DSC) and Dynamic Mechanical Analyzer (DMA). The samples studied were tetraglycidyl methylenedianiline (TGMDA), XD-7342.00L and blends of XD-7342.00L and D.E.R. (Trademark of The Dow Chemical Company) 332. All the systems were cured with diami nodi phenyl sulfone (DADS) accelerated with boron tri fluoride monoethylamine (BF3*MEA) complex. The DADS was blended in at 130°C, and the BF3-MEA was added after the resin had cooled to 100-110°C. The oven temperature was then reduced to 55°C for 4 hours followed by 125°C for 2 hours and finally 175°C for 2 hours. The test samples in the DSC were heated up to 295°C at 20°C/minute for the first scan. The sharp increase in heat flow (Figure 1) from the TGMDA system beginning at about 240°C indicates this system was not as completely cured as the XD-7342.00L system, even though they both received the same cure schedule. This may indicate a problem with dimensional stability using TGMDA relative to XD-7342.00L which exhibits a much smaller exotherm. In the second scan (Figure 2) the same samples were


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High Performance Epoxy Resins

TABLE II TYPICAL CLEAR CASTING PHYSICAL PROPERTIES OF RESINS CURED WITH NADIC METHYL ANHYDRIDE (NMA)l


PROPERTY

XD-7342.00L XD-9053.00L D.E.N. 438

HEAT DISTOR TION TEMP., °C

236

223

FLEX. STRENGTH, PSI ROOM TEMP. 100°C 150°C 180°C 220°C 260°C

12,800 12,200 9,100 8,100 6,900 2,900

19,000 13,000 12,400 10,300

FLEX. MODULUS, PSI ROOM TEMP. 150°C 180°C

4.9 χ 10 -

189

183

-

5

EPOXY CRESOL NOVOLAC

15,600 14,400 8,000 5,500

-

18,300 15,200 10,600 6,000

-

780

5.1 χ 10$ 3.3 χ 1θ5 3.0 χ 105

4.8 χ 10$ -

5

5.6 χ Ι Ο 2.9 χ 10$ 1.6 χ 10$

DISSIPATION FACTOR ROOM TEMP. 150°C 180°C

0.007 0.007 0.009

0.006 0.003 0.003

0.006 -

0.006 0.004 0.007

DIELECTRIC CONSTANT ROOM TEMP. 150°C 180°C

3.8 3.9 3.9

3.7 3.8 3.8

3.4 -

3.4 3.5 3.5

VOLUME RESISTIVITY, OHM cm ROOM TEMP. 150°C 180°C

15

>10 6.8 χ 1011 3.7 χ l u l l

IS

>1Q 1.1 χ 1012 1.9 χ l u l l

>1θ15 -

>χο15 1.2 χ 10*2 4.3 χ 10^

x

85% OF STOICHIOMETRIC AMOUNT OF NMA ACCELERATED WITH 1.5 PHR (PARTS PER HUNDRED PARTS OF RESIN) BENZYLDIMETHYLAMINE


140


TABLE III


TYPICAL CLEAR CASTING DATA OF PHENOLIC-CURED XD-9053.00L COMPARED WITH EPOXY CRESOL NOVOLAC RESIN

EPOXY CRESOL PROPERTY

XD-9053.00L

NOVOLAC

HEAT DISTORTION TEMPERATURE, °C FLEXURAL STRENGTH, PSI ROOM TEMPERATURE 100°C 150°C 180°C FLEXURAL MODULUS, PSI ROOM TEMPERATURE 100°C 150°C 180°C DISSIPATION FACTOR ROOM TEMPERATURE 150°C 180°C DIELECTRIC CONSTANT ROOM TEMPERATURE 150°C 180°C VOLUME RESISTIVITY, OHM cm ROOM TEMPERATURE 150°C 180 C e

213

154

16,600 14,400 12,500 7,600

21,100 15,400 5,800 1,200

5.0 3.7 3.0 1.9

χ χ χ X

10$ 105 105 105

5.4 4.4 1.5 0.1

χ χ χ χ

0.004 0.004 0.012

0.005 0.005 0.015

4.2 4.2 4.2

3.9 3.9 4.1

15

>10 2.3 x I0 3.1 χ lOlO n

5

IQ 10 1θ5 10$ 5

>10l5 4.7 χ 1θ}^ 4.0 χ lQlO



F i g u r e 1.

Differential

scanning c a l o r i m e t e r ;

first

s c a n i s DADS/BF3·ΜΕΑ CURED.


142


Q ω PS < ω s ΓΟ


fa PQ

Q (Λ •H

C CO

υ en x) c

ο ο -Ι

Ο

ι—I

to Ο 00

C

•Η C C

CO

υ

υ) i—t CO

•Η 4J

C ω u ω

u-i

Μ-Ι •Η Q CNJ

Epoxy Resin Chemistry II - American Chemical Society

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