Compatibilizers (Additive)
Compatibilizers(old)(better)
The properties of polymers can be tailored to some extent by the
copolymerization of two or more monomers simultaneously. In this way the
monomers are mixed and fixed together on a molecular level. However, for small
batches, it may be more convenient to mix homo polymers by melt blend blending.
However, a serious drawback is the lack of miscibility. This issue can be
circumvented to some extent by the use of proper compatibilizers.
Compatibilizers are a special type of additive. Whereas certain additives do
their duty simply by physical action during the whole service time, e.g.,
antiblocking agents, other types of additives start with a chemical reaction in
the case of emergency, e.g., light stabilizers. In contrast, compatibilizers
are effective by a chemical reaction already in the stage of processing.
Some of the fundamental requirements for a compatibilizer as additive
for reactive processing include:
- Optimal interfacial tension
- Sufficient and easy mixing
- Functional groups in the parent
polymers
- Fast reactivity of the additive, at
processing
- Enhanced adhesion between the phases
in the solid state.
(J. K. Fink, A Concise Introduction to Additives for Thermoplastic
Polymers, page 209, 215, 217)
Compatibilizers(new)
Environmental
threats restrict the use of nondegradable polymers and provide incentive for
the development and use of degradable plastics. To obtain a cost-effective
bioderadable plastic, starch-filled polyetylene (PE) is still the best alternative,
but starch/PE blends are incompatible at the molecular level and often give
poor performance. In order to overcome this drawback, either the PE or the
starch should be modified. This comparatively new method of producing
compatible thermoplastics blends by reactive blending extends to the formation
of copolymers or interacting polymers. This differs from other
compatibilization methods, which require the addition of seperate
compatibilizers. In reactive blends, the blend components themselves may be
chosen or modified in such a way that reactions occur during melt blending and
interfacial adhesion/compatibility of immiscible polymers becomes possible. The
small amount of graft polymer formed during the blending and reactions between
the components is enough to stabilize the morphology and to improve the blend`s
properties.
(Thermoplastic Starch: A Green Material for Various Industries,Yazar: L. P. B. M. Janssen,Leszek Mościcki, page:46)
Light Stabilizers (Stabilizer)
Light Stabilizers(old)
(Krishna Seshan, Handbook Of Thin-Film
Deposition Processes and Techniques, p. 13.14)
Light Stabilizers(new)(better)
Light Stabilizers (Stabilizer)
Light Stabilizers(old)
In general, polymers deterioratein the presence
of sunlight, which results in cracking, embrittlenement, chalkin,
discoloration, or loss of mechanical properties, such as tensile strength,
elongation, and impact strength. Photodegradation occurs as a result to
exposure to ultraviolet ligth at wavelengths 290-400nm. Different wavelengths
may produce different types of degredation, depending on the polymer. Specially
chemicals, called light stabilizers or UV stabilizers, are used to interfere
with the physical and chemical processes of light- induced polymer degradation.
Stabilization of the polymer can occur by the use of additives that absorb UV
radiation, preventing its absorption by the molecules of the polymers, by free
radical scavengers, by the additives that decompose peroxides, or by quenchers
that accept energy from the chromophore and convert it to heat.
(Krishna Seshan, Handbook Of Thin-Film
Deposition Processes and Techniques, p. 13.14)
Light Stabilizers(new)(better)
Many
polymer light stabilizers along with their relevant main functions have
additional capacity to be heat stabilizers or antioxidants. These molecules
often simultaneously bear fragments responsible for polymer protection against
the destructive effects of both light and thermal oxidations. For instance, a
number of hindered amine stabilizers (HAS) serve as both light and heat
stabilizers.
(Basics
of Troubleshooting in Plastics Processing, Yazar:
Muralisrinivasan Natamai Subramanian, page:50)
Flame Retardants (Retardant)
Flame Retardants (old) (better)
Flame
Retardants are chemical added to polymers to reduce flammability by any or a
combination of the following mechanisms: (1) interfering with flame
propagation, (2) producing large amounts of incombustible gases and/or (3)
increasing the combustion temperature of the material. The chemicals may also
function to (4) reduce the emission of noxious or toxic gases generated during
combustion. (Mikell P. Groover; Fundamentals of Modern Manufacturing Materials,
Processes, and Systems 3rd Edition; pg.156)
Flame Retardants(new)
The
amount of additives reduction maintains the mechanical standarts but nagatively
affects the flame resistance of the materials. In flame retardant compound,
addition of coupling agents or surface mdifiers reduces its flame retardancy.
The
bis(diphosphate) ester of resorcinol (RDP) provided an outstandng and improved
flame retardant and mechanical properties to high performance thermoplastic
materials such as PC, PPO, PC/ABS, PPO/HIPS and polyesters.
(Basics
of Troubleshooting in Plastics Processing, Yazar:
Muralisrinivasan Natamai Subramanian, page:49)
Heat Stabilizers (Stabilizer)
Heat Stabilizers(old)
Function:
Used to prevent oxidation of plastics by heat, especially during processing but also in application: widely used in PVC compounds. Heat stabilizers act by stopping oxidation, or by attacking the decomposed products of oxidation.
Properties affected:
Stability during processing: resistance to thermal breakdown of component under mechanical stress or loading: retention of colour transparency.
Materials:
Metallic salts: lead: combinations of barium, cadmium, zinc: organotin compounds. Hindered phenolics, secondary aromatic amines (primary anti-oxidants). Phospites/phosphonites, thioethers, soya-based epoxies (secondary anti-oxidants). Synergistic combinations of these.
(Murphy J.,Additives for plastics handbook, 2001, p.93 table 8.1)
Used to prevent oxidation of plastics by heat, especially during processing but also in application: widely used in PVC compounds. Heat stabilizers act by stopping oxidation, or by attacking the decomposed products of oxidation.
Properties affected:
Stability during processing: resistance to thermal breakdown of component under mechanical stress or loading: retention of colour transparency.
Materials:
Metallic salts: lead: combinations of barium, cadmium, zinc: organotin compounds. Hindered phenolics, secondary aromatic amines (primary anti-oxidants). Phospites/phosphonites, thioethers, soya-based epoxies (secondary anti-oxidants). Synergistic combinations of these.
(Murphy J.,Additives for plastics handbook, 2001, p.93 table 8.1)
Heat Stabilizers(new) (better)
In processing, plastics can be subjected to heat or used to
extend the life of the end products. Stablizers are used to prevent degradation
of material while processing. Heat stabiliers protect the material against
heat. During exposure to light by outdoor exposure, UV stabilizers are used to
protect against deterioration in short and long term use.
The incorporation of UV stabilizer is necessary for
protection against UV degradation. Enhanced UV light stability can affect the
color stability and mechanical properties of plastics. UV stabilizers protect
PE from damage by sunlight in outdoor environments. Similarly, carbon black in
PE mulch film protects and blocks the penetration of radiation.
(Basics
of Troubleshooting in Plastics Processing, Yazar:
Muralisrinivasan Natamai Subramanian, page:46)
Active Fillers (Filler)
Active Fillers (old)
Filler materials are classified into
two categories. Active and non - active fillers. Active fillers are composed of
chemically active materials or compounds that convert readily and permanently
from one composition to another when subjected to sufficient energy initiate
reaction. For the purposes of this discussion, the active filters to be
considered are often composed of active elements, such as titanium, aluminium,
hafnium, zirconium, vanadium, and niobium, and the energy applied to initiate
the conversion is heat. Brazing with active filler materials is a relatively
simple method and is generally preferred over brazing with inactive fillers.
(Implantable Neural Prostheses 2:
Techniques and Engineering Approaches, Zhou D., Greenbaum E., Page: 37)
Active Fillers(new)(better)
To
produce near net shape parts, active fillers are used to compensate for the
shrinkage of the precursor during pyrolysis. Reactive powders are employed,
usually elemental metals or intermetallics, which will react with the
decomposition products or reactive pyrolysis atmosphere to form a new phase
that expands in volume, i.e. the filler has an αβ>1.
The product will be a composite of the pyrolyzed polymer derived ceramic matrix
and reaction products from the filler.
The volume expansion ofthe filler
compensates, fully or partially, for the shrinkage of the matrix during the
polymer-to-ceramic transition. This has been termed
Active-Filler-Controlled-Pyrolsis (AFCOP) by Greil et al. [Greil, 1995]. As an
example, if elemental metal powder is added to a polysiloxane polymer and
pyrolyzed in air, the polysiloxane will react to form a Si-O-C ceramic,
evolving gas and densifying/shrinking in the process. The reactive metal filler
will, concurrently, interact with either the hydrocarbon pyrolsis byproducts or
reactive air atmsphere to form a carbide or oxide ceramic, both of which have
lower density than the metal, and thus, a larger volume. Some examples of
reactive fillers are: Al, B, C, Cr, Mo, Nb, Si, Ti, V, Zr, CrSi2,
MoSi2, TiSi2, TiB2. Even some
unconventional materials have been demonstrated, such as the recycling of rice
hull ash, containing 85-90% SiO2 with the
balance carbon, for the production of SiC [Siquiera, 2009].
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