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Plasticizer
Outline
Introduction Historical development Mechanism of plasticization Classification of plasticizer Performance of plasticizer Plasticizer efficiency Plasticizer market Introduction
A substance or material incorporated
in a material (usually a plastic or an elastomer) to increase its flexibility, workability, or distensibility. In 2003, the worldwide market for plasticizers was more than 4.6 million metric tonnes(10 billion pounds), with approximately 90% applied as plasticizers for PVC. Historical development
In 1868, use of camphor in nitrocellulose by the Hyatt brothers
In the early 1940s, Gresham’s patented use of DOP (di-2-ethylhexyl
phthalate) in PVC Until the late1970s, use of DOP prevailed as the preferred general-purpose
plasticizer for PVC
Recently, 70 different plasticizers available, about 80% of the worldwide
consumption is comprised of three plasticizers, di-2-ethylhexyl phthalate
(DOP),diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP).
Mechanism of plasticization
• Effect of platicizers on thermal mechnical deformation of
Rigid polymeric chains Lowering the brittle-tough transition or brittleness temperature and Tg
and extending the temperature range for their rubbery or viscoelastic
state behavior Decreasing the melting viscosity Mechanism of plasticization
Lubricating theory of plasticization
Gel theory
Free volume Lubricating Theory
the plasticizer molecules diffuse into the polymer and weaken
the polymer-polymer interactions the plasticizer molecules act as shields to reduce polymer- polymer interactive forces and prevent the formation of a rigid network.
This lowers the PVC Tg and allows the polymer chains to
move rapidly, resulting in increased flexibility, softness, and elongation. Gel Theory
Considering the plasticized polymer to be neither solid nor liquid
but an intermediate state, loosely held together by a three-
dimensional network of weak secondary bonding forces. These
bonding forces acting between plasticizer and polymer are easily
overcome by applied external stresses allowing the plasticized
polymer to flex, elongate, or compress.
Free Volume
More space or free volume is provided for molecular or polymer
chain movement. When plasticizers are added, it will lower the Tg by separating the
PVC molecules, adding free volume and making the PVC soft and
rubbery. Different plasticizers yield different plasticization effects because
of the differences in the strengths of the plasticizer-polymer and
plasticizer-plasticizer interactions. Plasticizer for PVC
For a plasticizer to be effective and useful in PVC, it must contain
two types of structural components,polar and apolar.
Polar portion bind reversibly with the PVC polymer, thus
softening the PVC
non-polar portion allows the PVC interaction to be controlled
so it is not so powerful a solvator as to destroy the PVC crystallinity; adds free volume,
Polar portion: carbonyl group of carboxylic ester
non-polar portion: aliphatic side chain of an ester Plasticizer for PVC
The balance between the polar and non-polar portions of the
molecule is critical to control its solubilizing effect; if a plasticizer is too polar, it can destroy PVC crystallites; if it is too non-polar, compatibility problems can arise.
Estimating plasticizer compatibility
solubility parameter methods
Classification
Monomeric or polymeric plasticizers
Based on chemical structure
According to the performance characteristics
General Purpose (GP)
Performance Plasticizers (PP)
Specialty Plasticizers (SP):
• General Purpose (GP) Plasticizers providing the desired flexibility to PVC along with an overall balance of optimum properties at the lowest cost. • Performance Plasticizers (PP) Contribute secondary performance properties desired in flexible PVC beyond the GP type, while imposing somewhat higher costs. Key performance criteria as “Strong solvators”, “Low temperature” and “Low volatility”. • Specialty Plasticizers (SP):
Provide properties beyond those typically associated with
flexible PVC designed for general purpose or specialty
characteristics.
Properties such as “Low diffusivity”, “Stability”, and “Flame
resistance”. General Purpose
Phthalate synthesis
molecular design rules
sample
Extender Most commonly employed with phthalates to reduce costs in general purpose flexible PVC. Naphthenic hydrocarbons Chlorinated paraffin extenders (secondary plasticizer) • Performance Purpose (PP)
“PP-SS” strong solvator
Increased polarity and/or aromaticity, Dihexyl and butyl, octyl
phthalate, benzoate ester and tri(cresyl) phosphate
“PP-LT” low temperature
Phthalates made with normal or linear alcohol
Aliphatic dibasic esters contributes exceptional low temperature
property: esterification of carboxyl acid with monohydric alcohol
“PP-LV” low volatility Low vapor pressure because of high molecular weight high molecular weight phthalate (greater than DIDP-446) Increasing the molecular weight increases the ration of apolar/polar functionality until loss of PVC compatibility occurs at molecular weight greater than DTDP-530. High molecular weight phthalates have low volatility and compatibility with PVC Trimellitates are the product of three moles of monohydric alcohols and trimellitic anhydride (TMA)
The alkyl group, compared to phthalates, contributes higher
molecular weight; the ester group contributes sufficient polarity to maintain PVC compatibility. HO
O O
O • Specialty Plasticizers (SP) “SP-LD” Low diffusion Low diffusion is contributed to the high molecular weight and high branched isomeric structure DIDP and DTDP are sometimes used with high costly diffusion-resistant plasticizer polymeric plasticizer: Polyester with molecular weight from 1000~8000, polyehtylene copolymer( EVA et al ) and terpolymer Higher molecular weight, higher branch, higher viscosity result higher diffusion resistance. Pentaerythritol esters are a type of “miscellaneous” plasticizers that impart both low volatility and diffusivity. They are esterified with a stream of straight chain fatty acids to make plasticizers. Hercoflex®600 is the pentaerythritol tetraester and 707 is a mixture of tetra and hexa esters, using a mixture of pentaerythritol and dipentaerythritol. Their molecular weights are approximately600 and 750, respectively, which contributes to both low volatility and diffusivity. “SP-Stab” for stabilizing function, Epoxy plasticizer: enhance thermal and UV stability of PVC
Epoxy soybean oil: molecular weights of approx. 1,000 causing
them to perform as low volatility plasticizers
The primary performance attributes of epoxy plasticizers are
their role in PVC stabilization
“SP-FR” fire resistance in PVC
Include halogenated (preferably brominated) phthalates and the
phosphate family Brominated phthalate esters are produced by the esterification of tetrabromophthalic anhydride with various alcohols, Phosphate plasticizers which may be considered as “inorganic esters” are prepared by the slow addition of phosphorous oxychloride to alcohol or phenol. The highly aromatic tricresyl phosphate (TCP) is the most effective fire retardant OPCl3 + 3 HOC6H4CH3 → OP(OC6H4CH3)3 + 3 HCl
