Rosin
Rosin
Rosin
50
Printed in Great Britain. All rights reserved. Copyright © 1989 Pergamon Press plc
CONTENTS
I. Introduction 297
I.l. Source of rosin 299
1.2. Chemistry of rosin 299
2. Rosins as polymer chemicals 301
2.1. Rosin in paint, varnish and coatings 301
2.1.1. Antifouling paint formulations 302
2.1.2. Traffic paint 302
2.2. Rosin in printing ink formulations 304
2.3. Rosin in adhesive formulations 304
2.4. Miscellaneous uses of rosin and rosin derivatives 305
3. Rosins as polymer feedstocks 305
3.1. Polymerization of rosin 306
3.2. Copolymerization of rosin and rosin derivatives 307
3.3. Alkyd resins 308
3.4. Polyurethanes 310
3.5. Epoxy resins 311
3.6. Polyesters 313
3.7. Polyamides 316
3.8. Polyesterimides 316
3.9. Polyamideimides 318
3.10. Miscellaneous rosin polymers 323
4. Properties of polymers 323
5. Thermal behavior 324
6. Polymer modification 327
6.1. Crosslinking 327
7. Polymer blends 328
8. Rosin-maleic anhydride adduct vs trimellitic anhydride 332
9. Conclusion 334
Acknowledgements 334
References 334
I. I N T R O D U C T I O N
The energy and feedstock crisis has resulted in a serious strain on the prospects
for petrochemicals in polymers? Many petrochemicals and petroleum-derived
*To whom all correspondence should be mailed.
297
298 S. MAITI et al.
polymers have become less competitive due to the high price of oil or petroleum
fractions. As the availability of oil and petroleum fractions has become very
uncertain, this has resulted in a severe competition for oil between uses as fuel
for energy and as feedstock for petrochemicals. Although the entire petro-
chemical industry (including fertilizers and synthetic polymers) consumes less
than 10% of the supply of crude oil, the greater demand for fuel for energy
makes uncertain the future supply of feedstocks for petrochemicals at a reason-
able price. The cost advantage of polymer materials in general over the other
conventional materials has already been eroded considerably by the price rise of
crude oil. Never before have plastics been faced with such tough competition
from traditional materials like metals, alloys, glass, etc.
This scarcity and high price of crude oil has led to research and development
activities worldwide for the use of alternative, preferably renewable, resource
materials as feedstocks for polymers and petrochemicals. Trimellitic anhydride
(TMA), benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic
dianhydride (PMDA) are the key chemicals for the manufacture of a number of
industrially important chemicals and polymers such as high temperature resist-
ant polyamideimides, polyimides, polyesterimides and other copolyimides, high
temperature plasticizers, paint additives and other polymer chemicals. TMA,
BTDA, PMDA, etc. are petroleum-based compounds and are manufactured by
only a few companies in the world. Since these are strategic materials, their
availability is uncertain particularly in times of emergency. It is, therefore,
highly desirable to develop a suitable substitute material for TMA and allied
petroleum-based products.
In an attempt to find a suitable alternative and renewable substitute
for petroleum-based TMA and allied chemicals we have recently developed
Rosin-Maleic Anhydride Diels-Alder Adduct (RMA) from gum rosin, a
pine wood exudate, and maleic anhydride. 2-6 Large amounts of gum rosin
are available in India, particularly in the lower foothills of the Himalayas.
Gum rosin is made to react with maleic anhydride to form the Diels-Alder
Adduct. The Diels-Alder Adduct, RMA, is also known as maleopimaric
acid. The molecule of RMA, like TMA, contains one carboxyl group and
one anhydride group - the two reactive functionalities capable of undergoing
various chemical reactions with appropriate reagents. The hydrophenanthrene
ring system present in the rosin moiety of RMA offers thermal and oxidative
stability to the RMA molecule just as the benzene ring does to the TMA
molecule. It is expected from the above structural similarities that RMA may be
a suitable substitute for TMA in most, if not all, of its applications. Since rosin
is a cheap and renewable material, the price of RMA and its derivatives is
expected to be lower than that of TMA and TMA derivatives. The most
important point to be noted here is that the supply of rosin will be unhindered
as this is derived from a forest product abundantly available in India and many
other countries.
ROSIN 299
,CH[CH3)t
0 CH~ ~0
NOOC C HO0
TMA RMA
I. !. Source of rosin
Rosin is a thermoplastic acidic product isolated by widely different
procedures from exudates of pine trees and freshly cut and/or aged bole and
stump wood of various species of pine.
Rosin is classified, according to its source, into three main types viz. (a) gum
rosin (b) wood rosin and (c) tall rosin. 7-9 The specifications of three types-of
rosin are given in Table 1. Gum rosin is obtained as the residue from the
distillation of turpentine from crude turpentine pitch. Wood rosin is produced
by naptha extraction of waste pine wood after recovery of pine oil and turpen-
tine. Tall rosin is obtained from the distillation of tall oil. ~°Among the various
rosins the most important is common rosin or colophony obtained from various
species of pine trees.
/c.3 CH
CH3 CH C C~ ICH~cH3
CHz
C ~ cH3 CH
CH3 "CH
~CH 3
~
CH3
CH3
CH "'" CH=CH2
H3C COOH
Isopimaric acid
Rosin J)
Abiotio
acid
Heat
Acid I=
HOOC
~ CH3
CH (CH3)t
Maloi¢-anhy drido
Oiels-Alder reaction •
Levopimaric acid
CHCO\
CHtCH3)= I o
CHCO/
HOOC CH3
rosin-moleic anhydride odduct (RHA)
2. R O S I N S AS P O L Y M E R CHEMICALS
Rosin and its derivatives have been extensively used in various applications
within the chemical industry. In almost all of these applications, rosin and its
derivatives are used as industrial chemicals to modify the properties of existing
formulations or to bring forth altogether new performance characteristics of the
products. Rosin and rosin derivatives are widely used in paints, varnish and
coatings, ink formulations, adhesives, etc.
2.1.1. Antifouling paint formulations - Rosin and rosin derivatives are import-
ant chemicals in antifouling paint formulations. They may be used either as the
vehicle or as the antifouling agent. Maleated rosin bis(tributyltin) oxide was
reported to be used in antifouling paint formulations used for fishing nets. ~5A
marine antifouling paint for ship bottoms contains a reaction product of rosin
and hydrazine as the toxicant.26 Triphenyltin rosinate, obtained by reacting
triphenyltin hydroxide and rosin, was also used as an antifouling agent. 27 An
antifouling paint with good resistance to the erosive effects of water motion was
reported to contain a chlorinated rubber-rosin matrix, Cu20 and ZnO toxicant
mixtures, CaCO3 extenders, etc. 28 Acoustically transparent, camouflage anti-
fouling paints for coating rubber substrates without adversely affecting their
chemical stability or sound absorbing characteristics, have been prepared from
polyisobutylene rubber, rosin, Bu3SnF and pigment. 29A paint with a completely
seawater soluble film forming base and a long service life has been reported to
contain a resin ester prepared from rosin and a hydroxy acid such as salicylic
acid as the binder. 3° Good performance was observed for antifouling paints
based on rosin-chlorinated rubber mixtures plasticized with tricresyl phosphate
containing Cu20 and a small amount of ZnO as toxicants.3~ Cu20, ZnO,
CaCO3, chlorinated rubber, rosin, chlorinated paraffin etc. were mixed to
formulate an antifouling paint with good performance. 32
2.1.2. Traffic paint - A hot-melt traffic paint giving films resistant to abrasion,
impact and weather, was prepared from maleic acid modified rosin ester resin,
sunflower oil modified alkyd resin, talc, TiO2, glass fiber, etc. 33 Rosin or modi-
fied rosin was blended with the reaction product of an ethylenically unsaturated
carboxylic acid or derivative with a resin made by copolymerizing a linear
conjugated diene with styrene, to obtain a pavement marking composition with
improved compressive strength at low temperature, a4 Maleated rosin, alkyd
plasticizer, MgO, TiO2, and glass beads were mixed to prepare a road marking
composition with good compressive strength, abrasion, weather and chemical
resistance. 35Water thinnable traffic marking paints were prepared from maleated
rosin, drying oil, NH3, shellac, etc. and were reported to have better performance
than commercial brands. 36A reaction product of a cyciopentadiene derivative,
rosin and a fatty acid was esterified with an alcohol. This ester was used as the
ROSIN 303
3. R O S I N S AS P O L Y M E R FEEDSTOCKS
polymer with 35% dimer content and a softening point of 124°C, useful for
paints, inks, construction materials, adhesives, paper additives, etc. 99
Titanium tetrachloride ~°°and aluminium chloride '°~ were used to polymerize
rosin in organic solvents. In the case of the former catalyst, '°° the molecular
weight of the product was found to be only 364. Rosin having a molecular
weight of 317 and a softening point of 71 °C was polymerized in the presence of
40% stannic chloride ~°2 at 59°C in ligroin to yield a product with a molecular
weight of 1319. When the reaction was carried out in benzene at 80°C, the
molecular weight of the product was found to be 1346, indicating that the
product was a tetramer or pentamer) °2
Rosin polymerization in an organic solvent in the presence of a catalyst at
20-100°C was reported. '°3 Melt polymerization of rosin at 220°C in the presence
of an aluminosilicate catalyst was also reported.~°4 Rosin, on heating in an inert
atmosphere in the presence of methanesulfonic acid or a trihalomethanesulfonic
acid as the catalyst at 60-180°C, polymedzed to a product having a softening
point of 85°C and a viscosity of 285 MPas) °5 It was reported that rosin, on
heating at 60-180°C for 4-6 hr in an inert solvent in the presence of an insoluble
polymer having pendant sulfonic acid groups, gave 31.9% dimer with a soften-
ing point of 91°C. t°6
The double bond of the rosin molecule is sterically hindered. Since it
is difficult to use this unsaturation for polymerization, the molecular weight of
the product formed is generally very low. This fact is reflected in the literature
reports on rosin 'polymers'; in most of the cases the products are less than a
dimer except in one case in which the product was reported to be a tetramer or
pentamer.~°2
I IocC~H~ " HC
( CH3 ) 2[CONH(CHz)3 NH(CH2)3NH
(CH2)3-NH -OCR
R = Rosin Moiety
CH2-- CH c.2-
( ~ - OC-- R OOCRJF1
Vinyl ester of perhydrogenoted Homopolymer
Rosin
R = Rosin moiety
CH2= CH 4" CH 2 = CH
I
O-OC-R I~ I
oocR .In
RI
RI---A¢ / C L
Copolymer
O-OC-R CN
-- C H 2 - - C H - - CH 2 -- CH - - CH2 ~ CH Cat
Crosslinked polymer
O-OC-R CN
Terpolymer
3.4. Polyurethanes
Rosin can be converted to hydroxy terminated compounds which can then be
reacted with diisocyanates to obtain polyurethanes. A polyurethane was
prepared by reacting a polyisocyanate with a polyester having a viscosity of
5,000-10,000 M Pa at 25°C in the presence of a blowing agent. The polyester was
obtained by the reaction of tall oil containing 15-35% (by weight) rosin acids
with a polyhydric alcohol. '~6 The reaction product of rosin with ethylene or
propylene oxide was used tIT in the manufacture of polyurethane foam.
Hydroxymethylated derivatives of rosin acids, tolylene diisocyanate and a
polyol were reacted to obtain a polyurethane elastomer)~8 Polyols obtained by
reacting rosin acids with formaldehyde and alkoxylating the hydroxymethylated
ROSIN 311
n>l
OOC-CH
R-COOR'-(OHIn_4 -I- CH- COOH . R- COOR'< ~HCOOH
CH- COOH (OHln_ 2
or
.(OOC CH= CH COOH)2
R-COOR~(OHln_ 3
etc.
R-COOR%00C CH =CH COOH + CH2=CH
I I
(OH)n-2 X
Vinyl monomer
c°t" 1
-•CH 2 -CH - ~
X
CH - CH - } ~ - - - i -
I
CO0- R- O'OCR Jn
I
(OH)n_ 2
Copotymer
product with an alkene oxide were mixed with conventional polyols and poly-
isocyanates to give rigid polyurethane foams with reduced flammability.I]9 Poly-
urethane fibres were prepared using N-(2-hydroxyethyl) maleimidopimaric acid
salts. Then, the effects of incorporation of these compounds on mechanical
properties and oxidative thermal aging properties of polyurethanes were
studied, t2°
HOOC
~ CH 3
'-CHlCI'~)2 ] COOH
COOH
CH=--CH--CHt
I
OH
I
OH OH
I
O,v~. 0,.~,
I I
CO-O-CHt--CH- CH =
, i ~ "CH [CH3)t ]
CO-O- CHt--CH -- CHz--O
0,,,~
,vv,v, O-OC CH=
Epoxy resins were also prepared from epichlorohydrin and a reaction product
of rosin with maleic anhydride, 13~'~32acrylic acid) 33'~34or methacrylic acid. 134
Methyl epichlorohydrin has also been used in place of epichlorohydrin) 34 Some
of these resins were cured by anhydrides to yield products having good process-
ability at 80-90°C and physical-mechanical properties similar to those of com-
mercial epoxy resins. 13~'t33 Epichlorohydrin-maleopimaric acid copolymers of
molecular weight 675 + 20 and 1080 + 80 respectively were synthesized and cross-
linked, and their dielectric and physical-mechanical properties were reported.~35
Unsaturated polyesters with increased heat and chemical resistance were
prepared by polymerizing maleic anhydride with propylene glycol in the
presence of the reaction product of diglycidyl acrylopimarate with methacrylic
acid.t36 Glycidyl esters of saturated, branched chain C9_. acids were reacted with
an adduct of pine rosin and maleic anhydride at 200°C to give polyester resins.137
Glycidyl esters of rosin acids were polymerized in the presence of cationic
catalysts to give film forming polyesters with increased elasticityJ 3s A nonflam-
mable polyester resin capable of being crosslinked and having a high molecular
weight was prepared by reacting epoxy resin with chlorinated rosin in the
presence of carbon dioxide. The final product (melting point 85-120°C) was
reported to be useful in coating formulations) 39 Novel rosin polyesters have
been prepared by treating a dicarboxylic acid or its anhydride with rosin glycidyl
esters. The product has a M. 4266, .~,/.~r,, 1.63, and glass transition tem-
perature 82°C. This patent also reported that glycidyl esters of gum rosin and
hydrogenated rosin had been polymerized) 4° A reaction scheme for the syn-
thesis of epoxy resins from rosin is shown in Fig. 7.
3.6. Polyesters
For one to prepare polyesters from rosin, the rosin needs to be converted to
a dicarboxylic acid by reaction with suitable reactants before polyesterification.
A method of converting rosin to a dicarboxylic acid is to react it with/~-propiol-
actone. The dicarboxylic acid thus obtained was reacted with diethylene glycol
to form a polyester) 4t (Fig. 8). In a subsequent patent, these authors have used
the rosin polyester resin thus prepared in hot-melt adhesive compositions) 42 It
was further reported that gum rosin could also be modified with acrylic acid
instead of the carcinogenic /~-propiolactone) 42 The polyester resin prepared
from rosin, /~-propiolactone and diethylene glycol was further modified with
fumaric acid or maleic anhydride and mixed with styrene. The mixture was
COOHI~ I ~ COOH
HOOC CH3 HOOC CH3
314 S.MAITIet al.
R
H3C CO-O-OC
HOOC CH3
Rosin I c.-co, II o
c H- COs
o
"o
HOOC CH 3 H3C CO-O-OC " "CH 3
RMA
LPOXYRESIN I I EPOXYRESll
= Polymer
CL-CH2-CH-CH 2 CL-CH2-CH- C H 2
\/ \ /
0 o
+ +
.,-co-o- c.2-c.-c.2 RMA
o
glycidyl e s t e r of rosin R=-CH (CH3) 2
R i = Rosin moiety
m~
HOOC CH
"-cH|CH3)tCHt-CHt - c
I o J
HOOC CH
~ CH lC~) t
~ COOH
HO(CHzCHt)zOH
..}-coo-,c,, ot
tOG CH~3 CH(CH3It ..mR
rosin molecules will be present as pendent groups on the main chain. Polyester-
based water-resistant coating compositions which hardened at room tempera-
ture were prepared by dissolving a maleopimaric acid-monoallyl glycerol
ether-allyl glycidyl ether-diethylene glycol-sebacic acid copolymer in an
isopropanol-isobutanol mixture. The copolymer was prepared by refluxing
maleopimaric acid with the other constituents at 230°C with continuous removal
of reaction water, t47 Colored polyesters were recently prepared by reacting
RTS-12 (pentaerythritol-esterified maleated rosin) with azo or anthraquinone
disperse dyes. t4s Copolyesters useful for coatings resistant to abrasion, water,
alkali, acid and solvents were prepared by esterifying glycerol simultaneously
with rosin and poly(bisphenol A maleate) or poly(bisphenol A phthalate). 149
Dimethyl terephthalate, glycerol and zinc acetate were heated for 3 hr at 210°C,
and then rosin was added and the mixture was again heated at 275°C for 3 hr
to obtain a modified polyester resin having a softening point of 113°C. ~5°In the
last two cases, rosin, being a monocarboxylic acid, will act as a chain terminat-
ing agent.
One well-known method of polyester synthesis from rosin is to react rosin
with unsaturated acids like acrylic acid or fumaric acid (Diels-Alder reaction)
followed by polyesterification with a diol. This type of polymer has a softening
point in the range of 60-100°C and is used as a hot-melt coating material for
road marking, t53 A polyester prepared by reacting fumaric acid-modified rosin
with a polyol at 220°C (softening point = 147.5°C, .O', = 1,200) was further
modified by dehydration followed by reaction with tolylene diisocyanate and
neutralization with aminoethanol to give a copolymer which was used in print-
ing ink. t54 A polyester resin was also prepared by reacting a rosin-polyhydric
alcohol melt with dicarboxylic acids or their anhydrides. '55
A new polyester was prepared from a rosin-acrylic acid adduct and hexa-
nediol, t56'~57Rosin was first reacted with acrylic acid in the presence of hydro-
quinone at or above 150°C for 5 hr. The finely powdered white product (yield
68%, m.p. 220°C) was refluxed with thionyl chloride for 10 hr to yield a diacid
316 S. MAITI et al.
CC C ~ H 3 cH(CH3]2Grit =ell
HO0
I
COOH ~ CHICH3}= ] COOH
1 HO(CH=)6
OH C tH3/~CH {CH312[
foe COG[
chloride (yield 90%, m.p. 150°C). The diacid chloride was reacted with hexa-
nediol in D M F : N M P (3:1) solution containing 4% LiC1, first at ambient
temperature and then at higher temperature (100°C), to obtain the polyester;
yield 71%, inherent viscosity 0.28dl/g (Fig. 9).
3.7. Polyamides
Polymers for printing ink were prepared by reacting fumaric acid-modified
rosin with urea or with a diamine) 5~ Rosin-maleic anhydride adduct was also
reacted with urea to obtain a polymeric product) 58 Polyamides were probably
obtained in those cases. A polyamide was also prepared by reacting a diamine
or amine alcohol with dimerized or more highly polymerized natural rosin) 59
An amber colored polyamide was prepared by heating at 140-225°C a mix-
ture of rosin-maleic anhydride adduct, polymeric fatty acid, tall oil fatty acid,
adipic acid and bis(hexamethylene) triamine. This polyamide was used as a
binder for quick drying water resistant printing inks. 16° A water soluble poly-
amide was prepared by reacting polymerized fatty acids, maleated rosin, and
aromatic or aliphatic diamines for 2 hr at 200°C/50 mm. The softening point of
the polyamide was about 129°C) 6~
Maiti and coworkers have investigated the synthesis of various polymers
using maleopimaric acid (RMA) or similar Diels-Alder adducts as the starting
material. One of the polymers, a polyamide, was synthesized from the acid
chloride of rosin-acrylic acid adduct and hexamethylene diamine in 76% yield.
It had an inherent viscosity of 0.30dl/g '56''57 (Fig. 10).
3.8. Polyesterimides
Polyesterimides are an important class of engineering plastics due to factors
such as good processability, generally high glass transition temperature, solubility
in common solvents, relatively low cost, and good thermal and outdoor stability.
ROSIN 317
1 COOH SOCtz ,~
I
cocl
_
tOC
~ CH~
"CH {CH3)z ] CONH--{CHt),--NH~
-an
-HCI
Polyomide
~ _ CHlCH3h CHCO\
I /0
CHCO
CHCO. _OCHC
~ - C H (CH~)= \
I /N-R-N
, ~
I (c~)=Hc
CHCO ~OCHC
-t" HOROH
~_~ oc c~
CHCO
[
c.co /
N-R-N
.OCHC
%c.c
(CHair HC
CH~ CO.O.
RPEI Jn
POLYMER R R"
RPEI I -CH.z--CH z - -- (CHt) s -
RPEI 2 - CHt-CH,z-
RPE= 3 - CHz-CI'.It- -.~)-- CHz-.,~)-
RPEI 4 -- (Cl'lt)~,-0 - (CI"lt}z- -'~'-C H=e--~-"
3.9. Polyamideimides
Schuller and Lawrence reported the preparation of polyamideimides from
maleopimaric acid (RMA) derivatives. ~65-~67Maleopimaric acid, on treatment
with thionyl chloride, was converted into maleopimaric acid chloride which was
reacted with diamines to form bisamides. The bisamides were fused with dia-
mines to give head-to-head and tail-to-tail linked polyamideimides.165-~67
Treatment of one mole of monoacid chloride with excess diamine in a modi-
fied Schotten-Baumann procedure followed by acidification with hydrochloric
acid gave an amide amine hydrochloride salt of maleopimaric acid. This salt was
then fused with a diamine to give a head-to-tail linked polyamideimide resin.
Fusion of maleopimaric acid chloride with one mole of diamine gave randomly
linked polyamideimides.~65-~67Treatment of maleopimaric acid chloride with
methyl alcohol gave trimethylmaleopimarate, which, when fused with various
diamines, gave polyamideimide resins t66 (Fig. 13).
Molecular weights of the polyamideimides were reported to be in the range
of 6,000 (inherent viscosity 0.10 dl/g for a 1% solution in dimethylformamide at
30°C). Films and fibres have been prepared from these polymers.
ROSIN 319
+ HIN-~ COOH
Polyomideimide
FIG. 13. Synthesis of polyamideimides.
320 S. MAlTi et al.
R ::
;“G
+
CHdO
HOOC CH, II
R = CH ICH,),
:
CHC,
I COOH
CHC’
x
HOOC CH,
RMID
I
P
COC’
8
CIOC CHS
RMIDC
POLYMER R’
HN
RPAI I H:N&
NH2
RPAI 2 H24
RPAI 3 H2N-@-NH2
RPAl 4 HzN-(CHzh-NH2
RPAI 5 &No-CHeoNH,
RMA HMDA
O
O II
~.~N-RI CH~,~/~------..-~[~ C-OH
RIAA
CH~ Amic acid
R : -CH~
CH3
RIAA RI RIAA R~
RIAA ! --(CHt)t-- RIAA 4 -~)--CHt-~'-
RIAA 2 -(CHt) . - RIAA 5 "~'-50"~-'~'-
RIAA 3, ~ RIAA 6 -Cb-cH,-C)
-
0 0
CH:~ ~0
~o~,N-RI-NHt
R= --CH[CH3)=
POLYMER RI
pat 6 - (CHub-
PAX 7 --(CHt)s -
PAI 8 ,-,@-
PAl ~ -@-c H,-@-
PAZ to -@-so,-@-
PAI It -O'c.='O-
4. PROPERTIES OF POLYMERS
Due to the steric effect of the bulky rosin moiety, it is difficult to prepare very
high molecular weight polymers from rosin, and the polymers are usually
amorphous or poorly crystalline.4'172Rosin-based polymers are generally soluble
in aprotic polar solvents like dimethylformamide, dimethylacetamide, dimethyl
sulfoxide, N-methyl 2-pyrrolidone, hexamethylphosphoric triamide, etc. They
tend to be partially soluble in tetrahydrofuran, cyclohexanone and 1,4-dioxane.
Maiti and coworkers determined the solubility parameters of rosin-based
polyesterimides and polyamideimides from the relationship
5. T H E R M A L BEHAVIOR
r o s i n - b a s e d p o l y m e r s . A l t h o u g h the i s o p r o p y i g r o u p a t t a c h e d to the h y d r o -
p h e n a n t h r e n e ring system o f l e v o p i m a r i c acid is sterically shielded in the m a l e o -
p i m a r i c acid ( R M A ) molecule, it c a n u n d e r g o o x i d a t i o n at higher t e m p e r a t u r e s .
Nevertheless, rosin p o l y m e r s have shown satisfactory high t e m p e r a t u r e stability.
Results o f t h e r m o g r a v i m e t r i c analysis ( T G A ) o f r o s i n - b a s e d p o l y e s t e r i m i d e s
a r e s h o w n in Fig. 17. R P E I - 1 was f o u n d to be the m o s t stable o f the p o l y m e r s
tested. 4 Results o f i s o t h e r m a l a g i n g in air are s h o w n in T a b l e 5.
T h e t h e r m a l stability o f the p o l y a m i d e i m i d e s f r o m rosin a p p e a r s to be b e t t e r
t h a n t h a t o f the polyesterimides. This is expected f r o m the fact t h a t
RPEI-I A
I00
" ~ t RPEI-2
RPEX-3 •
RPEI-4 o
.~ 60
~ 4o
20
Ol
I00 200 300 400 SO0 6 0 0
Temperature, °C
FIo. 17. Thermogravimetric analysis of polyesterimides.
326 S. MAITI et al.
RPEI- 1 180 -
RPEI-2 225 12.0 10.3
RPEI-3 180 9.0 35.7
RPEI-4 210 5.2 19.7
RPEI-5 245 3.2 28.0
0 0
II II
the thermal stability of the - C - N H - linkage is higher than that of the - C - O -
linkage and the degree of intermolecular association is also higher in the former
than in the latter. TGA curves of a few polyamideimides are shown in Fig. 18.
The effect of isomerism on the thermal stability of polyamideimides synthesized
from three isomeric diamines is shown in this figure. The order of thermal
stability is para-isomer > meta-isomer > ortho-isomer. This is consistent with
the higher degree of crystallinity of the para-isomer due to chain symmetry.
I00
80
AI-2
60
.~ 40 ~ P~I~'~ PAt-5
e 20
I I I~ % '~ | I I I~ I
IO0
PA•I-11
7:
~ 80
60-- AI-8
pAI-9
40-- PAI'IO
20-
0 I I I l ~,\
tO0 300 500 700 IOO 300 500 700
Temperoture p "C
FIG. 18. Thermal stability of polyamideimides by TGA.
ROSIN 327
2 hr 12hr 36 hr 2 hr 12 hr 36 hr
6. POLYMER MODIFICATION
It has been reported earlier that the rosin moiety offers interesting possibilities
for modification of p o l y m e r s : There are at least two sites which are amenable
for polymer modification. First, the residual unsaturation in the hydrophen-
anthrene ring of the rosin molecule can be utilized for crosslinking reactions.
Second, the isopropyl group may be oxidized under suitable reaction conditions
to yield materials which may be further exploited for graft copolymerization
and/or crosslinking. The possibilities are schematically shown in Fig. 19. 5
6.1. Crosslinking
Rosin polymers, on heating to 150°C or above for about 10hr, do not
crosslink, presumably due to the shielding o f the residual double bond. Even
heating at 100°C for 10hr with free radical initiators like A I B N or benzoyl
peroxide failed to initiate the crosslinking reaction. However, at higher tempera-
tures crosslinking occurs with or without free radical initiators. For example,
the polymers could be fully cured by heating at 250°C for 2 hr in the presence
of dicumyl peroxide) s°'lBI
Evidence for crosslinking included the observed insolubility of the cured
material in polar solvents and 10% sodium hydroxide solution, as well as the
absence o f the olefinic double bond in the IR spectra o f the polymers after
328 S. MAIT! et aL
Graft Homopoiymer
Copolymer
M =Vinyl monomer
7. P O L Y M E R B L E N D S
PAl* 2.66
80% PAl, 20% novolac* 2.62
60% PAl, 40% novolac* 4.82
40% PAI, 60% novolac* 4.22
Pure novolac*: 1st decomposition 0.50
: 2nd decomposition 4.15
80% PAl, 20% resole** 3.32
60% PAI, 40% resole** 5.50
40% PAl, 60% resole** 4.63
Pure resole**: 1st decomposition 0.19
: 2nd decomposition 8.06
80% PAl, 20% shellact 2.90
60% PAl, 40% shellact 2.95
20% PAl, 80% shellact 0.72
Pure shellact: 1st decomposition 0.68
4 hr 8 hr 12hr 24 hr
*Polyamideimide.
**Polyamideimideblended with novolac (Ref. 182).
tPolyamideimideblended with resole (Ref. 183).
:~Polyamideimideblended with shellac (Ref. 184).
aRef. 185, bRef. 186, CRef. 187, dRef. 188, CRef. 189, fRef. 190, gat 260°C, hRef. 191, iin vacuo, Jat 3250C for 120hr, kRef. 192.
334 S. MA1TI et aL
thermal stability of these two types of polymers may emerge. It appears that the
aromatic ring of TMA possesses similar thermal stability to the hydrophenan-
threne ring of RMA.
Substitution of TMA by RMA in the synthesis of polyamideimides from
TMA and diphenylmethane diisocyanate reduces the thermal stability. The
standard sample prepared from 100% TMA and diphenylmethane diisocyanate
shows no weight loss up to 400°C (thermogravimetric analysis) in a helium
atmosphere, but those containing 10, 50 and 100% RMA in place of TMA show
5, 9 and 13% weight loss, respectivelyJ93 However, molecular weights of the
polymer samples were not reported. It may, therefore, be argued that the
replacement of TMA by RMA, which is less reactive due to steric factors, might
cause a reduction in the average molecular weight, thereby reducing the thermal
stability of the polymers.
9. C O N C L U S I O N
ACKNOWLEDGEMENTS
The authors wish to thank the Council of Scientific and Industrial Research
(CSIR), New Delhi, for partial financial assistance.
REFERENCES
i. C.E. CARRAHER,JR. and L. H. SPERLING(Eds), Polymer Application of Renewable-Resource
Materials, Plenum Press, New York (1983).
2. S. MAre and S. D ~ , Polymer Preprims 21, 190 (1980).
3. S. MAre, A. RAY, M. MAre and S. DAS, Am. Chem. Soc., Div. Org. Coat. Plast. Chem.,
Prepr. 45, 449 (1981).
4. S. D,~, S. MAre and M. MAre, J. Macromol. Sci. Chem. AI7, 1177 (1982).
5. S. MAre, S. DAS, M. M~'la and A. RAY, Polymer Application of Renewable-Resource
Materials, (C. E. C ~ ' ~ - ~ and L. H. SPERLXNGEds) p. 129, Plenum Press, New York
(1983).
ROSIN 335