Note: Descriptions are shown in the official language in which they were submitted.
7~3
D-5,778
GL~SS ~LAKE REINFORCED REACTION
I~J~C~l~ION MOLDED POLYME~S
Background:
This invention relates to improved reinEorced
reaction injection molded (P~IM) polymeric articles and
to a method o~ makin~ them. More particularly, the
inventlon relates to the incorporation of flaked glass
particles in liquid RIM precursor constituents. The
constituents are molded such that the glass flakes are
pre~erentially oriented to improve physical character-
istics of the polymerized article.
Reaction injection molding (RIM) i9 a process
by which highly chemically reactive liquids are in-
jected into a mold where they rapidly polymerize to
form a coherent molded article. The most common RI~
processes today involve a rapid reaction between highly
catalyzed polyether or polyester polyol and isocyanate constituents~
The constituents are stored in separate tanks prior -to
molding and are first mixed in -the mixhead upstream
of a mold. Once mixed, they react rapidly to form
solidified polyurethane polymers. While the invention
will be specifical]y described in terms of urethane
R~M systems, the invention has general application to
RIM processes based on other chemical systems.
~lth~ugh RIM urethane materials have many
desirable physical characteristics, they also have
generally high coe~ficients of thermal expansion (CTE),
poor dimens~onal stability, and considerable flexibility
at room temperature. A RI~ panel attached to rigid support
will permanently buckle and wave when exposed to elevated
temperatures~ Thus, as molded, unreinforced RIM urethanes
are not generally directly suitable for use as structural
panels. The relatively large surface area and thin
aspect of large panel structures only serve to ayyldv~Le
the inherent shortcomings of RIM urethane materials.
As a consequence, the use of reinfoxcing
fillers in RIM urethanes has been extensively e~m;ned~
Currently, automotive body panels are made from RI~
urethanes filled with short ~less than 1/8") milled glass
fiber, generally in amounts less than about 25% of the
polymer weight. For applications such as automotive
ascia where a higher coefficient of thermal expansion
and higher heat sag can be tolerated, unfilled RIM
urethanes may be used.
While filling RIM urethanes with milled glass
iber substantially improves certain physical properties,
other problems still exist. For example, while stability
and strength are increased, these improvements occur only
in the direction of flow of liquid in the mold. Physical
properties measured perpendicular to the direction of
flow may be unimproved or only slightly improved over un-
filled coun~erparts~ Moreover, the inclusion of milled
glass fibers in reinforcing amounts of more than a few
weight percentcause inherent waviness in panel-like
structu~es. This waviness is ve~y apparent in panels
which are coated with high gloss paints.
~n an e~ort to get around the adverse affects of
glass fiber fillers, and the high CTE of unfilled panelsl
I have ~xperimented with a number of other filler systems
for RIM. ~ ha~e ~ound that any significant amount of
talc, clay or other amorphous filler increases the
~iscosity of liquid precursors to the extent that they
cannot be impingement m'xed. The use of hollow or solid
glass spheres does not improve the physical properties
of RIM urethanes either ~;men~ionally or in terms of
o~erall strength. Mica flake was found to be unaccept-`
abie because it interferes with the polymerization
reaction of urethane in the mold.
Objects:
It is therefore an object of the inventlon
to pro~ide a method of reaction injection molding
articles' with substantially improve~ coefficients of
thermal expansion, strength, and less surface wavines~
th~n ~rticles made'heretofore by RIM processes.
Tt is a more particular object to improve
the physical properties of RIM articles by the in-
clusion of glass flake fillers. A more particular
object is to incorporate glass flakes in liquid RIM
precursors and to inject these constituents into a
mold in a manner to ori~nt the flakes so as to opti-
miæe the physical characteristics of the finished ~icle.
Another object is to provide a method of
~aking a paneI or paneI-like RIM article'where the
physical properties are'particularly improved in all
directions in the'plane of the paneI. More specific-
ally, it is an object to reinforce RIM panels with
glass 1akes to effect such improvement. In a panel
in accordance with the'invention, the glass flake is
incorporated in a reinforcing amount such that the
flakes are aligned with their planar surfaces sub--
stantially parallel to the planar sur~aces o~ the
p~nel. Such' reinforced panels are stronger, have
reduced coefficients of thermal expansion, and have
less wavy suraces than prior art RIM panels.
' Brief ~um~ary~
In accoxdance with a preferred embodiment
of the invantion, these'and other ob~ects may be
accomplished as ~ollo~s.
A desired amount of glass 1ake'is mixed
~ith and dispersed in one or more'of the chemically
re~ct'~e'liquid precursor constituents ~or reaction
in~ect'ion ~olding. Generally, at least about 5 weight
percent based on the total polymer weight is desirable~
The re~n~orcing effect of the glass flake increases
proportionately to the amount incorporated.
Herein, glass flake'is defined as small
particle~ of friable amorphous material having a
generally planar surface, the area of that ~urface
being substantially greater than the particle thickness.
The flakes are'preferably no more than a few microns
thick and have aspect ratios (flake surface area to
thickness xatios) of at least about 40:1. The dia-
meters of the particles must be small enouyh to flowthrough ~IM metering, mixing and injecting equipment
~i~hbut clogging. A preferred type of flake glass is
made by melting a suitable glass composition based on
silica; extruding the molten material through a bushing
to ~orm glass film, cooling the film, and breaking it
~etween ~ooperatin~ rollers. The particles so produced
ma~ be'~urthe~ reduced in siæe in a ~uitable mill.
The'indi~idu~l particles closely resem~le minute panes
of broken window gl~ss~ Th~ymay be'coated with surface
~ct'ive'agent~ such''~s silane to improve'their dis-
pers~on and bonding ~racteristic~.
All the chemically reactive liquid constitu-
ents and the glas~ flakes dispersed therein are thor-
oughly mixed prior to delivery to the mold. However,
it is the shape of the mold and the flow of the liquid
constituents therein that ultimately determine the
orientation of t,he'flake glass in the polymerized pro-
duct. The flake orientation, in turn, determines the
direction and degree o~ improvement in physical
characteristics provided by -the flake glass filler
Generally, the glass flakes align in the
mold with their longest dimensions parallel to the
direction o~ flow of the liquid constituents in which
they are carried. In molds for making articles with
relatively thin cxoss sections, the flakes also become
oriented with their planar surfaces parallel to the
mold surfaces. Substantial rein~orcement is provided
by glass flake in all directions in the plane of the
flake~ Thus, in glass flake filled reaction injection
molded panels, substantial improvement in physical
characteristics is provided in all directions in the
panel planeO
What may be even more significant for certain
applications is the fact that glass flake filled RIM
panels have much less wavy surfaces than their glass
fiber-filled counterparts and do not develop waviness
when ~herm~lly cycled. This means that articles such
as automotive body panels can be molded, painted and
installed without special finishing procedures needed
to eliminate surface waviness in glass fiber filled
panels. Moreover, glass flake filled panels can fill
applications where unfilled panels cannot be used.
2~ Clearly significant advantages are to be
gained by incorporating glass flake as a filler in
reaction injection molded plastics~
Detailed Description
My invention will be better understood in
3U view of this more detailed description.
A molding trial was conducted using glass
flake filler in an otherwise conventional urethane
~eaction injection malding system. In the trial, flat
plaques were molded ~rom un~illed urethane, urethane
filled with short lengths of milled glass fiber and flake
glass.
The crosslinked urethane was the reaction
product of a polyether polyol with a hydroxyl function-
ality greater than two and diisocyanate terminatedprepolymer based on methylene diisocyanateO The polyol
was NIAX D337~ Resin made by Union Carbide and the
lsocyanate was ISONATE 143L~ made by Upjohn. The polyol
and isocyanate were initially retained in separate pres-
surized agitated tanks with nitrogen or dry air blankets.These urethane forming chemicals have ~een used
heretofore to make fiber glass filled structural panels.
The polyol and isocyanate were metered into the
mixer by means of a Krauss Maffei PU80~ metering machine.
The unit was capable of processing the reinforcements
only on the polyol side. Positive displacement piston
pumps were used to eject the polyol and isocyanate into
an impingement mixing chamber. The chamber itself had a
cylindrical shape, the polyol and isocyanate ports being
located at 90 intervals of a circumference of the
cylinder in alternating order. The port for the filled
polyol had a diameter of 4.2 mm and that for the unfilled
isocyanate 2.0 mm. The injection pressures of the polyol
and isocyanate were 2350 psi and 2200 psi, respectively.
The polyol was maintained at a tank temperature of
approximately 46.1C (115F) and the isocyanate at 33.9C
(93F). The output capacity of the metering equipment to
the mold cavity was approximately 3.5 pounds per secondO
The molding machine used was a Kannegeisser
Model MFT. A two-piece mold was mounted on the
stationary and movable press platens. The mold had a
,, ."
~9~
plaque-shaped cavity with a flat surface area of 2411 x
42" and a ~hickness of 0.1 inch. The upper platen tilted
away from the lower platen in the mold open position to
facilitate demolding.
The mold cavity walls were coated with Green
Chem MR 6023~ pa~te and sprayed with Chem Trend XMR 136~
mold release before each shot. The mold temperature was
maintained at about 170-185F. For filled plaques a
minimum mold temperature of about 180F was desirable to
prevent skinning. The gate to th~ mold had an elongated
slit shape which ran the length of the shorter side of
the ~old (approximately 16 inches).
Preparatory to molding unfilled urethane
plaques, the polyol and isocyanate outputs of the RIM
machine were calibrated to achieve a weight ratio of 100
parts polyol to 102.5 parts isocyanate. While this
produced a relatively brittle urethane, it was suitable
for comparing the properties of unfilled, glas~ fiber
filled and glass flake filled plaques molded in like
manner in the mold described above. All plaques were
post cured in a flat position for 30 minutes at 250F to
complete polymerization.
The calculation of a predet~rmined weight
fraction filler in a molded urethane plaque was made as
follows (iso refers to isocyanate):
wt polyol ~ wt iso
1.00 - weight - (wt~ polyol + wt lSO) G Wt. filler
fraction filler
Because the machine used to mold plaques could only
accommodate ill~r on the polyol side, the weight percent
filler to be dispersed was calculated as follows:
7~ 3
~t polyol ~ wt filler = wt ~raction filler in polyol
The ratio of filled polyol to isocyanate was then re
calculated on the basis of 100 parts polyol and filler
ts allow for the filler in the polyol:
wt polyol * wt ~f iller - 100 parts filled polyol
wt iso X parts llnf; 11~ iso
For example, if 15 weight percent glass fiber
was to be introduced into the urethane system described
above at a polyol to iso ratio o~ 100:102.5 then
100 poIyol 1 102~5 iso _ ~100 polyol + 102.5 iso) = 35 7 paribtsr
Then to determine the amount of glass to be mixed with
the polyol constituent
100 polyol ~ 35.7 glass fiber ~ 26-3 wt percant glass f~x~ in
Then to readjust the mix ratio to maintain the pre-
determined chemical ratio of 100 parts polyol to 102.
parts isocyanate
100 polyol ~ 37~5 glass fiber _ 100 parts polyol-& glass fi~er
102.5 isoc~ana-te ~ 75.53 iso
Thus the machine was set ~o deliver 100 parts polyol
and glass per 75.53 part~ isocyanate to achieve a
15 weight percent fiber glass filler in the molded
urethane article. O~viously, the calculations would be
the same ~or ~lass flake, glass fiber or other solid
~iller.
7~L3
Table I indicates the Sample Designation and
number of plaques that were molded during an experimental
run in accordance with ~he invention:
TABLE I
SAMPLE NUMBER
DESIGNATION MOLDED REINFORCEMENT/LEVEL
N- 10 Unfilled
G-15 ~ OCF P117B~ 1/16" milled glass fibers,
G-25 8 lS% ~ 25~ by weightr respectively.
S5-15 10 OCF P117B~ Low aspect ratio milled
SG-25 10 glass fib~rs (<1/32n), 15% and ~5%
by weight, respectively.
F-10 10 OCF Hammermilled "C"Flakeglas~-1/64"
F-15 11 10% and 15% by weight, respectively.
GF #1 10 5% Flakeglas~/5% P117B - 1/16"
GF #2 10 5% F~lakeglas~/10% P117B - 1/16"
GF #3 10 10% Flakeglas~/5% P117B - 1/16"
GF ~4 11 10% Flakeglas~/10~ P117B - 1/16"
Two types oE fiberglass were employed. The
first was OCF P117B~-1/16" milled glass fibers sold by
Owens-Corning. These samples are designated with a G,
The glass was coated with a dispersion enhancing resin.
In an effort to improve the properties of fiberglass
filled RIM plaques in directions other than the flow
direction in the mold, very short glass fibers were used
in some of the trials. These fibers were OCF P'91 17B~
~creened to include particles 1/3~19 in length and less.
These samples are designated SG f or short ~l ass .
The key constituent of the subject invention is
flaked glass7 (Sample designa~ion F)~ Although flaked
glass has been kn~wn since the mid '50's, it has
heretofore not been used as a filler constituent
-
for RIM~ Flaked glass is made by melting a glass of
desired chemical compositionO The molten glass is then
ex~ruded through a heated annular bushing. The ex-
trusion forms a cone-shaped glass film, generally about
2 to 10 microns thickr which is continuously pulled
away ~rom the bushiny by a pair of pinch rollers. The
~il~ cool~ rapidly a~d i9 broken by the rollers. The
broken films are h~mm~r-milled to create small particles
of "~lake1' glass. TIle individual particles resemble
broken panes of windo~ glass. Flake'glass suitable for
use in the subject i~ ention is described in greater
deta.il in 'l~lakeglas V - Filled Coatings: Past, Present
and Future" by Dr. N~ Sprecher, published by Owens-
Corning Fi~erglas European Operations. ~or the subject
invention, I preer E or C type glass par-ticles which
a~e less t~an about 8 microns thick, ~ith an average
diameter less than about 1~32l'. The'preferred aspect
r~tioof flake surface area to thickness is greater' than
a~out 25:1 and preferably grea~er than 40:1~ Larger
~0 ~lass particles may be used, howe~er, they tend to be
more abrasive and harder to handle in conventional re-
inforced RIM systems. The flake glass may be coated
wi~h silane or other dispersion enhancing coatings.
Howe~er, the'glass flake used in the molding trials
reported herein were not so coated.
Some prel;m; n~ry work has been done with silane
coated glass flake. Qualitatively, it appears that the
silane coating promotes rapid dispersion of the flake in
polyol resin. It also seems to promote bonding between
the RIM polymer matrix and the flake particles. This
in turn, enhances the effect of the flake filler on the
physical properties of the polymer matrix.
Physical property data and rheometic impact
data were taken using standard ASTM test methods fQr
ea.ch type of plaque from Table I. The re~ults are
sho~n in T~les 2 and 3~ Samples designated A were
cut ~rom the 1/2 of the test plaque closest to the
mold inlet runner ~hile those designated R were taken
~rom the half o the test plaque furthest ~rom the
inlet runner. The tests were conducted on the samples
both in the direction of flow in the mold Idesignated
parallel~ and in the direction in the plane of the plaque
perpendicular to the flo~ (designated perpendicular).
11
T~3LE 2
~hYSI~ k~ 'Y ~;~TA ~
iEL--~. æWUl.US. H:At 'i~ tENSlLlE StREti~l
~P 1) '~P~ O ' NC0~ SI ) ~ 10~ ~ERCE~I~
- ~fV~ ~1 ( Il) lH RM~L EXP~S3`~1 51~ ',11) PART
`80~1~PLI: YEll;Hr SPEtlFie HEA / KAN~ ~ /IN x lo-6/~r3 50~,HEIW/ KAN~ / SHRINKA~
~ESC~lPTlCJII ~E~EH~ ERAY11~7 TD. OE~ ~TD. DE'J. t_~ tl~ I' I) STD. DE~I. STD. DEV. SID. OE~'. St3. ~
.011.0~ 89,000/216 92,100/53~~3.8 73.9 .7~/.6G 40901?0.9 4140/1~13.8 95.~1'11.11 112/lS.,q 1.~5/1.51
.oP19~ 91,~10/2i4 gl~,300~15. 7~.6 ~3.1 .79/.6~ 3930~156~ 3900196.2 92.6~Z0.7 8~.~112.~
~:15 ~) 19O3~.11 135,000/517 18?,00U/Z9 ~53.3 34.~l .b51.Z8 4220/91.5 ~Z90/126~2 35.q/10.2 23.216.2 .rJ2/.60
Gi5 ~ . Y6.Q~.0~ IS~OU/3~8 119,0Q~/43~51.1 33.Z .651.25 ~9030/143.6 420018,5.~ t718.4 21.~/2.4
G~5 ~A~ 1 22.91.~ 150,~0013Z7 299,000/40' 52~3 l~.G .88/.20 4580/129.9 49401275.4 38.811.9 19/5.7 .~01.2
~;Z5 ~ 24.51.16 15a~000/862 Z85,0W/lOr2 53.q 1'6.0 .91/.Z3 4240/6~c4 5100J5~.2 '1917.B lq.4/3~3
~G15 6A~ I lSo7 1.30 175,0001349 179,000/25. ~16.6 5~.9 2.291Z.03 5050/102.1 4890t4q.4 39.616.2 40.2J~.2 .9~t.~1 i~
$~5 ~Ei) IS~O 1.~ a63~0001339 172,00016~a 47.~ ~.1 2.1~11.82 488q/23.9 ~7601140.3 30.816.~ 3~.2/3.
St;25 ~ Z~,71.33 187,00Q/192 20e5QOQt49 S3.~ 50.1 2.08/.76 522ûl342.6 5250tqO6.0 2B.8/7.3 2B.~18.4 .921.11
!J3~5 e,B) -24.3 1.~ g~Q001358 213,9G~/28 59.6 ~6.~ .361.52 Ç81C/133.9 497QI19.5 29.çls.0 30f6.0 r
~-lQ 6Aa 1~ lt ~~ 155jQ9Ot329 169,000/52'. 50~7 ~ ~g~6 ~5Z1~311 i 3370tl8~?` 3570t63~1 19O~1!53~1 21;/5~a .ff;.
F'-10 ~8~ ~31~12 172~1D001422 183,~t0012~ 5~3 ~17.0 .611.3~1 ~13501~.1~ ~14~0187.6 25.6~5.~1 27.~111.5
~-15 ~Al 1~ t'~l6000/~09 19G,OoO/30~ ~6~0 9~5 1~101~87 3870139~0 39tlO156~3 14~/2~ ~ 16~611~5 c90/~7k
iF-15 ~B~ 15.91.14 .~ IY4,0001q51 Z08,00G/Sq ~ 3~.1 .721.6t 3790/57.9 3880J25.~ 2~,6/6cO 15.6/3.6
~ Dg (~ 3 178,QOO/~95 216,00~5~h 58.~ 38.~ 1.6~ 1500l70.0 4670152.4 ~0~.6 20.~15.~ .ffl.78
GF ~1 ~B~ ll.Ç2.Z0 1~3,000/~04 232,0iDO/52~51.3 3S.8 l.~ql.91 4260/57.7 4500/l70.9 20f2/3~ ' 16.21i.l
5:F ~2 tA) 13.~ l.Z~ 189,000f~115 251,000/~1~ 52.~ 31.3 1.65/.75 ~40!237.0 4~'t0160.2 26.~l605 19.6f3.1 .9Q/.52
~p ~Z ~B) l~.Z1.23 1~8,0~015~3 278,000/62h 5q.a 28.t 1.37/.72 4540/lGt.3 4990J94.~ Z1.415.7 15.6/~.3
GF ~3 (A? ~3.62.13 lS~,OOG/279 l91,000~57~ SO.? 34.5 .b31.3Z 40~10~38.3 4560/46.6 23.~qf5.4 W4.q .9QI.
G~ ~3 ~ 24.31.07 16~000/195 212,00Qi'54~ 4t.2 30.7 .701.51 366Q/33.9 3900f~1.6 ~6.2~2.~ Z213.7
e;F ~ A) 10.71.1~ 166,W~/630 2270009f~8~ 27.5 I.O~t.$5 414~/63.1 4i40/17.~ l9.1S16.i }9.4/O.i .7~1.51
GF ~4 S~ ~ 20.1 l.10 l~S~WO/61~ 201,000/69 39.~ 26.3 .991.45 374013Z.7 3810/Z42.? 18.8/~7 16.6/3~3
* Test3 ~t roor~ te~?erature (~C) unle~ otIlcrwi:3e indicate~.
-
~V7~3
13
T~BLE 3
R~O~RIC IMPACr TEST DA~
Y I E L D T O T A L
Sampl~ l~dcne~ Spe~d Fo2-c~ ~ralr21 EnerBY Tra~ En~rgy
It~p~ tMM~ tMlS) ~N~ (MM) tJ)tMM) tJ)
N- 2.46 2.230 2542 12.07 13.95 13.19 15.37.
G-lS Z.63 2.Z30 888 3.97 1.52 18.16 8.11
G-Z5 2.61 2.230 825 4.4Z 1.74 19.73 11.12
Sa-15 2.4~ 2.230 1533 6.17 4.09 17.90 11.39
SC-25 2. 44 2. 230 1224 5. 72 Z. 92 19. 62 9. 99
F10 2.69 2.230 1328 6.59 3.61 17.75 10.33
PlS 2.59 2.230 7S2 3.44 1.11 18.90 7.44
GF ~1 2. 342. 230 952 4. 71 1. 83 16. 86 8. 80
CF #2 2.432.230 ?q7 3.33 1.Z0 19.22 8.93
- GF ~3 2.702.230 828 3072 1;36 18.29 8.70
C;F ~ 2.812.23b 868 4.30 1.85 1a.56 9.70
Eadl V~lue is the a~erage o~ five ~5) s~les :tested
at ro~ l~ Lc~L;~e ~23~C~
M~S = ~ters/Second
N = Newtons
~ ~ ~oules
MM- MilliTneters
13
14
The unfilled plaques as molded had
relatively low flex moduli and high coefficients of
thermal expansion (CTE). They also had poor heat sag
characteristics, tensile strengths, high elongations
and relatively large shrinkage due to cure.
In the parts molded with l/16" glass, the
glass fibers tended to orient substantially parallel
to the flow of material into the mold. Thus, the
plaques showed improved ~lex moduli, tensile strength,
and part shrinkage only in the parallel direction.
However, these properties were not -improved to any
appreciable extent in the direction perpendicular to
mold flow. They exhibited the characteristic waviness
o~ glass fiber filled RIM paneIs.
Parts molded from the short glass showed no
appreciable improvement in some physical properties,
particularly CTE and strength.
14
)
TABLE 4
PEBPEN~lCU ~ R PARAT~T
U G-15W/o F-15W/o U -G-15 h F-15 /o
Flex M~dulus PSLX1000 A* 89 135 171 92 187 196
B 91 153 184 90 179 208
CTE (in/in Xlo-6/ ~ A 73.8 53.3
B 73.6 51.1 44.7 73.6 33.2 37.1
Heat Sag (1 Hr @ 250F) A 0.74 G.65 1.10 0.60 0.28 0~87 ~D
B 0.79 0.65 0.72 0.64 0.25 0.62
Tensile Sb~ A 4090 4220 3870 4140 4290 3900
B 3930 4030 3790 3900 420Q 3880
Percent Elonga~ion A 95.8 35.4 14.8 112 23.2 16.6
B 92.6 27 20.6 88~8 21.4 15.6
Percent Part Shrink A 1.45 .92 .90 1.51 .60 .78
* A indicabed sl~ple cut from half of plaque adjacent ~old inlet r ~er.
B indicates sa~ple cut fram half of plaque re~Dt~ frQm m~ld inlet run~er.
.3
16
Table 4 sets out data taken ~rom TaDle :2 for
unfilled, 15% glass ~iber ~illed ~G~lS~, and 15%
~lake glass filled ~F-15%~ panels ~or purposes of
comparin~ t~eir physic~l properties parallel and per-
pendicular to polymer ~low in the mold. The data show~mpro~ements in modulus, reduced coefficients of
thermal expansion and lowered elongation for hoth glass
fiber and flake fllled panels, especially in the
p~ralleI direction. Howe~er, only the glass flake
~illed sample exhibited substantial impro~ement of
these properti:es in the perpendicular direction. Thus,
~l~ke glass has been shbwn to be superior over all to
glass ~iber ~illers and to subsfantially improve the
physical properties of molded RIM panel~ in all
lS directions in the plane of the panel.
~ mi n~tion of plaques molded from flake glass
filled urethane showed that the glass ~lakes orient
~ith their planar surfaces su~stantially parallel to
the plane of: the plaques. This arrangement of filler
plates provides for improved properties in all direc~
. ~ions in th~ plane of a panel-like par~.: Although
other plate~ ~illers have ~een tried, gla~s ~lakes
: have thus ~ar ~een ~ound to ~e the only suita~le
~illers ~or makin~ ~IM panels with urfaces good enough
~X enameled automoti~e body panels.
The most remarkable and unexpected impxovement
brought about ~y the use o flake :glass filler is the
complete elimination o~ visually unappealing surface
waviness.~ This improvement is
particularly noticeable in panels coated with glossy
paint. Distinctness o~ image refers to the akility of
16
7~L,3
a smooth, glossy surface to reflec~ an image without
added distortion from irregularities in the coating
or substrate. The glass flake fllled panels (as
molded) all had dis~inctness of image properties at
least-as good as glass fiber filled panels presanded
to remove ~urface waviness. Furthermorer the glass
~lake filler eliminated any tendency for the RIM
plaques to warp, even when thexmally cycled. Even
without the improved physical properties pointed vut
above, the unexpected but great improvement in surface
waviness and warpage brought about-by flake glass
filler could warrant its use in RIM systems.
While my invention has been dPscribed in
. term~ of the speci~ic embodiment thereof, clearly other
forms may be readily adapted by one skilled in the art.
Accordingly, my invention is to be limited only by the
~ollowing claims.
17
