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Priplast Polyester Oligomers
Dimerized Fatty Acid Technology for Use in Epoxy Toughening
The Basis:Pripol Dimerized Fatty Acids
C=OOH
O=C HO
Large hydrocarbon part (C36) • hydrophobic• hydrolytic resistance of derivatives• affinity for non-polar matrices and surfaces
Irregular non-crystalline structure• flexibility• low Tg• flow, wetting
Di-functional constituent for:• polyamides• polyesters• polyurethanes
Use in Epoxy resins
• Dimer technology traditionally used in epoxy resins– In polyamide curatives– In modifed epoxies
• Why?– Brings flexibility (vibration / stress absorption)– Enhances hydrophobicity, weatherability and
compatibility with organic matrices (tar, hydrocarbon resins)
Modification of Rigid Polymers With Soft Segments
1.flexibilization crystalline or high-Tg
amorphous “hard”
segments
low-Tg amorphous “soft” segments
hard domain, with melting point close to that of the rigid homopolymer
soft domain, with glass transition temperature close
to that of the soft segment
Modification of Rigid Polymers With Soft Segments
a bad try at flexibilization
hard and soft segments are small copolymer too chopped up to form decent hard and soft domains low melting point and strength, high Tg, poor elastic recovery
Modification of Rigid Polymers With Soft Segments
2. impact modification crystalline or high-Tg
amorphous “hard”
segments
low-Tg rubber balls
hard, rigid, high-melting matrix with cushions to absorb impact stability of the compound is an issue
Dimer technology for epoxy modification
the low glass transition temperature of dimer acid makes it suitable for flexibilization and impact modification
the low polarity and Tg of dimer acid is a good strating point for phase separation
dimer acid itself is rather small as a soft segment (MW 580) so optimal properties cannot be reached
Impact Modification Technology
HOOC---- ----- COOHE-E
Polyesters based on dimerized fatty acids allow incorporation of larger mol wt soft segments, potentially resulting in better toughening performance etc.
n
Advantages of Polyester Modification Technology
HOOC---- ----- COOHE-E
• Possibility to graft the soft segment on the epoxy
• Possibility to carefully control molecular weight and polarity
– To exactly establish the degree of phase separation required
n
Additional Advantages
• Soft domains based on dimerized fatty acid are extremely hydrophobic, which reduces moisture diffusion through the matrix
• Polyesters based on dimerized fatty acids do not contain volatile toxic or smelly monomers
• Polyesters based on dimerized fatty acids are not susceptible to thermal or oxidative degradation
• Polyesters based on dimerized fatty acids have very low glass transition temperatures
Existing Grafted Impact Modifiers
• CTBN-rubber (‘liquid rubber’)
– a low-MW copolymer of acrylonitrile and butadiene
– contains unreacted double bonds
– High viscosity (60000 – 500000 mPa.s at 27 ºC)
Test Epoxy Formulation
Heat curable formulation
• 72% ‘Pre-react’– dimer polyester + low mol wt BPA epoxy (‘828’
type)
• 15% high mol wt BPA epoxy (‘1001’ type)
• 4% Phenolic Novolac
• Catalyst– Imidazole
– Cured at 175 C
Effect of Polyester Polarity
Several acid-terminated polyesters of PRIPOL 1009, low-MW dioic acid and glycol prepared
Constant molecular weight
Ratio of PRIPOL 1009 to low-MW dioic acid varied
HUGE impact on reaction
Modification with pure Pripol 1009 / glycol ester (no short-chain dioic
acid)
no grafting reaction
components are too incompatible
polymer is brittle AND sticky
Modification with ester of Pripol 1009 and short dioic acid (75/25)
some grafting reaction
components are still incompatible
polymer is brittle AND sticky
Modification with ester of Pripol 1009 / short dioic acid (50/50)
full grafting reaction
good phase separation on microscale
polymer is hard AND tough
Dimer technology for epoxy
toughening, dimerate vs CTBN modifier
property
CTBN
(1300X13)
Dimerate
(DA/SD/glycol)
glass transition temperature (ºC)
29 22
essential work of fracture (kJ/m2)
6.5 10.5
T-peel at ambient temperature (Ga)
60 66
T-peel at ambient after 40 h / 60 ºC /
60 % RH (Ga)
57 87
Moisture Diffusivity (cm2/s)
3.0 x 10-4 0.8 x 10-4
Modifier viscosity (mPa.s)
500 000 15000 - 20000
Conclusions
• Epoxy modification with dimerized fatty acid technology allows– Flexibility or toughening (even at very low
temperature)– Good stability against heat, oxidation and moisture
(as seen in other polymer systems)– A toughener which is not too high viscosity
• Flexibility of chemistry allows tailoring of polyester molecular weight and polarity, to fit the base epoxy resin
– Allows desired morphology to be exactly achieved