upul Ratnayake | Rubber Research Institute of Sri Lanka (original) (raw)

Papers by upul Ratnayake

A process for producing a natural rubber nanocomposite containing exfoliated organically modified... more A process for producing a natural rubber nanocomposite containing exfoliated organically modified montmorillonite and maleic anhydride grafted elastomer in a dispersion of natural rubber and reinforcing filler/inert filler wherein the cured nanocomposite has improved mechanical properties compared to conventional rubber compound containing a mixture of the reinforcing filler, carbon black and the inert filler, CaCO3.

Chinese Journal of Polymer Science, 2011

TiCl 4 /MgCl 2 /clay compound catalyst was prepared by chemical reaction. Exfoliated polypropylen... more TiCl 4 /MgCl 2 /clay compound catalyst was prepared by chemical reaction. Exfoliated polypropylene (PP)/clay nanocomposites were synthesized by in situ polymerization with this compound catalyst. Effects of polymerization temperature, polymerization time, propylene pressure, solvent consumption and pre-treat time of catalyst on catalyst activity and catalytic stereospecificity were studied. Under optimal conditions, activity of the nano-compound catalyst is about 88.3 kg/(mol Ti·h). Isotacticity of PP obtained in the nanocomposites is in the range of 89%99%, and its melting temperature is about 159°C. The weight-average molecular weight of PP can reach 6.7 × 10 5 7.8 × 10 5 , and the molecular weight distribution is between 7.7 and 7.9.

Layered structures in inorganic minerals are not easily intercalated when combined with conventio... more Layered structures in inorganic minerals are not easily intercalated when combined with conventional non-polar polymers such as polypropylene (PP). A new co-intercalation method is reported whereby the combined influence of low molecular weight polar additives and polyolefin-based compatibilizers on PP-clay nanocomposites (PPCN) has been investigated. Our research has shown that the interlayer spacing of montmorillonite clay increases dramatically, and increased particle dispersion is achieved, when short chain, organic additives (typically amidetype, AM) are included. In this work, the migration of these additives into the clay galleries has been confirmed by surface energy data (from contact angle experiments) and by various capillary flow measurement techniques. Shear flow data have been used to interpret the mechanism of intercalation, following compound preparation using melt-state mixing processes. At relatively low concentrations, the erucamide molecules assist the intercalation process in nanocomposites; however if an excess of AM is apparent within the bulk polymer melt, unusual flow behavior is observed which can be attributed to wall slip. Modified melt elasticity is also obtained with the PPCN's leading to reduced die swell characteristics in extrusion processes. Significant differences in melt flow behavior can therefore be attributed to the presence of AM; a mechanism for co-intercalation has been proposed in terms of hydrogen bonding between the additives and the silicate layers.

The effect of short-chain amide (AM) molecules on the intercalation of montmorillonite clay has b... more The effect of short-chain amide (AM) molecules
on the intercalation of montmorillonite clay has been
investigated by the melt blending of polypropylene (PP)
with clay in the presence of AM molecules such as 13-cisdocosenamide
(erucamide). Polypropylene–clay nanocomposites
(PPCNs) were prepared by the co-intercalation of
maleic anhydride grafted polypropylene (PP–MA) and an
AM compound. The resulting nanocomposite structures
were characterized with X-ray diffraction (XRD) and
transmission electron microscopy, whereas the thermal
characterization of the PPCNs was conducted by thermogravimetric
analysis. XRD results showed that the AM molecules
intercalated into clay galleries and increased the
interlayer spacing, a result confirmed by surface energy
(contact angle) and melt flow index measurements. This
additive allowed the formation of an intercalated nanocomposite
structure, but an exfoliated PPCN structure was also
formed with the use of AM with a PP–MA-based compatibilizer.
A new preparation method for PPCNs was, therefore,
developed by the co-intercalation of AM and PP–MA;
this resulted in a significantly improved degree of intercalation
and dispersion. The enhanced thermal stability of
PPCN, relative to pure PP, further demonstrated the
improved clay dispersion in the nanocomposite structures
prepared by this method. A possible mechanism for the cointercalation
of AM and PP–MA into the clay galleries is
proposed, based on hydrogen bonding between these additives
and the silicate layers. Consideration is also given to
possible chemical reactions and physical interactions in
this rather complex system. VVC 2008 Wiley Periodicals, Inc. J
Appl Polym Sci 112: 320–334, 2009
Key words: additives; clay; compatibility; nanocomposites;
poly(propylene) (PP)
INTRODUCTION
Polymer–inorganic nanocomposites are two-phase
materials in which inorganic particles are dispersed
at the nanometer range in the polymer matrix. Polymer
nanocomposites based on montmorillonite
(MMT) clay, which belongs to the general family of
2 : 1 layered silicates, have received increased attention
1–4 because they frequently show enhanced properties
relative to the unfilled polymer and equivalent
conventional composites

The influence of low molecular weight additives containing polar groups and modified polyolefin-b... more The influence of low molecular weight additives containing polar groups and modified polyolefin-based compatibilizers on polypropylene (PP)-clay nanocomposites (PPCN) has been studied, in terms of intercalation and degree of exfoliation achievable by melt-state mixing processes. PPCN were prepared by melt mixing two PP homopolymers with organically-modified montmorillonite type clay, in the presence of maleic anhydride-grafted polypropylene (PP-MA) compatibilizer. XRD analysis shows that interlayer spacing of clay has been increased dramatically, while TEM results show a significant improvement of clay dispersion in the PP matrix, when nanocomposites are prepared with commercial PP containing short-chain organic additives with polar end groups. Subsequent studies based upon customized PP formulations, with amide-type slip additive, confirm the intercalation of this additive into the clay galleries and its positive and significant impact on clay dispersion. Contact angle measurements suggest that these additives diffuse into the clay gallery space rather than migrating away from the bulk of the PPCN matrix. The interaction between polar group (NH 2 ) of this additive and the polar sites on the filler surface appears to be the driving force for the intercalation. POLYM. ENG. SCI., 46:1008 -1015, 2006.

A process for producing a natural rubber nanocomposite containing exfoliated organically modified... more A process for producing a natural rubber nanocomposite containing exfoliated organically modified montmorillonite and maleic anhydride grafted elastomer in a dispersion of natural rubber and reinforcing filler/inert filler wherein the cured nanocomposite has improved mechanical properties compared to conventional rubber compound containing a mixture of the reinforcing filler, carbon black and the inert filler, CaCO3.

Chinese Journal of Polymer Science, 2011

TiCl 4 /MgCl 2 /clay compound catalyst was prepared by chemical reaction. Exfoliated polypropylen... more TiCl 4 /MgCl 2 /clay compound catalyst was prepared by chemical reaction. Exfoliated polypropylene (PP)/clay nanocomposites were synthesized by in situ polymerization with this compound catalyst. Effects of polymerization temperature, polymerization time, propylene pressure, solvent consumption and pre-treat time of catalyst on catalyst activity and catalytic stereospecificity were studied. Under optimal conditions, activity of the nano-compound catalyst is about 88.3 kg/(mol Ti·h). Isotacticity of PP obtained in the nanocomposites is in the range of 89%99%, and its melting temperature is about 159°C. The weight-average molecular weight of PP can reach 6.7 × 10 5 7.8 × 10 5 , and the molecular weight distribution is between 7.7 and 7.9.

Layered structures in inorganic minerals are not easily intercalated when combined with conventio... more Layered structures in inorganic minerals are not easily intercalated when combined with conventional non-polar polymers such as polypropylene (PP). A new co-intercalation method is reported whereby the combined influence of low molecular weight polar additives and polyolefin-based compatibilizers on PP-clay nanocomposites (PPCN) has been investigated. Our research has shown that the interlayer spacing of montmorillonite clay increases dramatically, and increased particle dispersion is achieved, when short chain, organic additives (typically amidetype, AM) are included. In this work, the migration of these additives into the clay galleries has been confirmed by surface energy data (from contact angle experiments) and by various capillary flow measurement techniques. Shear flow data have been used to interpret the mechanism of intercalation, following compound preparation using melt-state mixing processes. At relatively low concentrations, the erucamide molecules assist the intercalation process in nanocomposites; however if an excess of AM is apparent within the bulk polymer melt, unusual flow behavior is observed which can be attributed to wall slip. Modified melt elasticity is also obtained with the PPCN's leading to reduced die swell characteristics in extrusion processes. Significant differences in melt flow behavior can therefore be attributed to the presence of AM; a mechanism for co-intercalation has been proposed in terms of hydrogen bonding between the additives and the silicate layers.

The effect of short-chain amide (AM) molecules on the intercalation of montmorillonite clay has b... more The effect of short-chain amide (AM) molecules
on the intercalation of montmorillonite clay has been
investigated by the melt blending of polypropylene (PP)
with clay in the presence of AM molecules such as 13-cisdocosenamide
(erucamide). Polypropylene–clay nanocomposites
(PPCNs) were prepared by the co-intercalation of
maleic anhydride grafted polypropylene (PP–MA) and an
AM compound. The resulting nanocomposite structures
were characterized with X-ray diffraction (XRD) and
transmission electron microscopy, whereas the thermal
characterization of the PPCNs was conducted by thermogravimetric
analysis. XRD results showed that the AM molecules
intercalated into clay galleries and increased the
interlayer spacing, a result confirmed by surface energy
(contact angle) and melt flow index measurements. This
additive allowed the formation of an intercalated nanocomposite
structure, but an exfoliated PPCN structure was also
formed with the use of AM with a PP–MA-based compatibilizer.
A new preparation method for PPCNs was, therefore,
developed by the co-intercalation of AM and PP–MA;
this resulted in a significantly improved degree of intercalation
and dispersion. The enhanced thermal stability of
PPCN, relative to pure PP, further demonstrated the
improved clay dispersion in the nanocomposite structures
prepared by this method. A possible mechanism for the cointercalation
of AM and PP–MA into the clay galleries is
proposed, based on hydrogen bonding between these additives
and the silicate layers. Consideration is also given to
possible chemical reactions and physical interactions in
this rather complex system. VVC 2008 Wiley Periodicals, Inc. J
Appl Polym Sci 112: 320–334, 2009
Key words: additives; clay; compatibility; nanocomposites;
poly(propylene) (PP)
INTRODUCTION
Polymer–inorganic nanocomposites are two-phase
materials in which inorganic particles are dispersed
at the nanometer range in the polymer matrix. Polymer
nanocomposites based on montmorillonite
(MMT) clay, which belongs to the general family of
2 : 1 layered silicates, have received increased attention
1–4 because they frequently show enhanced properties
relative to the unfilled polymer and equivalent
conventional composites

The influence of low molecular weight additives containing polar groups and modified polyolefin-b... more The influence of low molecular weight additives containing polar groups and modified polyolefin-based compatibilizers on polypropylene (PP)-clay nanocomposites (PPCN) has been studied, in terms of intercalation and degree of exfoliation achievable by melt-state mixing processes. PPCN were prepared by melt mixing two PP homopolymers with organically-modified montmorillonite type clay, in the presence of maleic anhydride-grafted polypropylene (PP-MA) compatibilizer. XRD analysis shows that interlayer spacing of clay has been increased dramatically, while TEM results show a significant improvement of clay dispersion in the PP matrix, when nanocomposites are prepared with commercial PP containing short-chain organic additives with polar end groups. Subsequent studies based upon customized PP formulations, with amide-type slip additive, confirm the intercalation of this additive into the clay galleries and its positive and significant impact on clay dispersion. Contact angle measurements suggest that these additives diffuse into the clay gallery space rather than migrating away from the bulk of the PPCN matrix. The interaction between polar group (NH 2 ) of this additive and the polar sites on the filler surface appears to be the driving force for the intercalation. POLYM. ENG. SCI., 46:1008 -1015, 2006.