Chapter ? Plastics Introduction

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Chapter ? Plastics Introduction
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Chapter ? Plastics Introduction
2.1 Plastics Introduction 2.2 Rheological
Properties of Polymer 2.3 Physical And Chemical
Changes in Polymer processing 2.4 Plastic
Process Performance 2.5 Commonly Used Plastics
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2.1 Plastics Introduction
2.1.1 Resin/Polymer/Macromolecular and Plastics
1. Conception of Plastics
Plastics, macromolecular organic materials ,whose
main elements are resin, polymer( macromolecular)
and auxiliary elements are Additives such as
plasticizer, filler, lubricant, colorant , will
flow to formed because of the influence of the
specific temperature and pressure in the material
processing
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2.1.1 Resin/Polymer/Macromolecular and Plastics
2. Conceptions of resin/polymer/macromolecular
Resin/polymer/macromolecular, usually refers to
organic polymer , solid ,semi-solid or liquid at
room temperature, having transformation or
melting range when heated, can flow with the
affection of external force ,which is the most
basic and most important ingredient of plastics.
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2.1.1 Resin/Polymer/Macromolecular and Plastics
3. Classification of Resin
Natural Resin
Refers to the amorphous organic matter, such as
rosin, amber, shellac ,obtained by the animal and
plant secretions in the nature.
Synthetic Resin
Refers to the resin product obtained from simple
organic compounds by chemical synthesis or
natural products by chemical reaction.
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2.1.2 Features And Structure of Polymer
1.Chemical Structure of Polymer
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2.1.2 Features And Structure of Polymer
1.Chemical Structure of Polymer
Ethylene
Polyethylene
Chemical Structure of Polymer
Number of ethylene
Polyethylene
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The whole chain Of molecular
Chain Segment
The movement of the whole chain of the molecule
is like a peristaltic snake.
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2.1.2 Features And Structure of Polymer
Structure Diagram of Molecular Chain of Polymer
Linear Polymer
Linear Polymer with Branched Chain
Three-dimensional Polymer
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2.1.2 Features And Structure of Polymer
2. Polymer synthesis methods (addition
polymerization and condensation reaction)
Homo-addition polymerization
Co-addition polymerization
Features of addition polymerization
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2.1.2 Features And Structure of Polymer
2. Polymer synthesis methods (addition
polymerization and condensation reaction)
C2H5-O-C2H5
Ether
Features of condensation reaction
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2.1.2 Features And Structure of Polymer
3. Aggregation morphology and performance of the
polymer
Solid, Liquid
Crystalline polymers
Amorphous polymers
The structure of crystalline polymers
1-Crystalline region 2-Amorphous regions
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2.1.2 Features And Structure of Polymer
4. Structure And Features of Polymer
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2.1.2 Features And Structure of Polymer
5. Thermodynamic properties of polymer
Thermodynamic curve When a constant pressure
operate on linear amorphous polymers or linear
crystalline polymer ,the curve describe the
relationship between the degree of deformation
and temperature.
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2.1.2 Features And Structure of Polymer
5. Thermodynamic properties of polymer
Glassy high elastic Viscous
Thermodynamic properties of linear amorphous
polymers
Degree of deformation
T
Thermodynamic properties of linear crystalline
polymers
Thermodynamic curves
1-Linear amorphous polymer 2-Linear crystalline
polymer
?m melting point
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2.1.2 Features And Structure of Polymer
6. Thermodynamic properties of polymer
Thermodynamic properties of three-dimensional
polymer
The change of mechanical state is very small with
temperature for the high molecular motion
resistance ,so there is no existence of viscous
flow state or high-elastic state which means
three-dimensional polymer do not melt when
exposed to heat but decompose at high temperature
.
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2.1.2 Features And Structure of Polymer
7. Polymer processing technology
Physical and technological properties of
thermoplastics in different states
State Glassy high elastic viscous
Temperature Below ?g ?g?f ?f?d
Molecule state Molecular entanglement is irregular line corporation or curly Molecular chain extend, the chain segment move Polymer chain move relatively
Physical state Hard solid High-elastic solid, rubber-like Plastic state or the state of high viscosity
Process possibility Can be used as structural materials for turning, milling, planing, filing, sawing, drilling and other machining Bending, blow molding, rolling, stamping, molding will have a greater internal stress Can be injection, extrusion, compression, injection pressure, forming stress
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2.1.3 Component of Plastics
Plastics include Polymers and Additives
1. Polymer / Resin
Adhere other component materials Grant the
plastic plasticity and flowability, lower
costing, etc..
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2.1.3 Component of Plastics
2. Additive
1) Filler
Effect
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2.1.3 Component of Plastics
2. Additive
1) Filler
Classification
By Chemical Property
By Shape
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2.1.3 Component of Plastics
2. Additive
2) Plasticizer
Able to increase the plastic workability,
scalability, and expansion of the material it is
compatible with resin, less volatile, high
boiling point organic compounds. The commonly
used plasticizer is a liquid or low melting solid
organic matter. Mainly are formic lipids,
phosphate, and chlorinated paraffin, etc.
Such as Dioctyl phthalate(DOP)

Effect
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2.1.3 Component of Plastics
2. Additive
3) Stabilizer
Substances known as stabilizers can block the
deterioration of materials.
Heat Stabilizer Its main role is to inhibit
or prevent resin degradation of heat in the
processing or use. Some heat stabilizers contains
heavy leads,metals, lead salts.Lead-free
stabilizer can be divided into three categories
composite stabilizer, organic tin stabilizer,
rare earth stabilizer
Its main role is to prevent resin degradation
because of the effect of light (plastic
discoloration, and mechanical properties
decrease).
Delay or inhibit the plastic oxidation
rate.
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2.1.3 Component of Plastics
2. Additive
4) Lubricant
Additives added in order to prevent the
plastic from sticking to mold in the molding
process, to reduce the friction between the
plastic and mold, and to improve the fluidity of
plastics, the plastic surface gloss.
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2.1.3 Component of Plastics
2. Additive
5) Colorant
Nicely decorate the plastic and some certain
coloring agents can also improve the light
stability, thermal stability and weather
resistance of the plastic.
Characteristics are between inorganic pigments
and dyes
Rendering capabilities, transparent, bright are
poor, but light fastness, heat resistance are
good and chemical stability make it can not be
easily faded.
Colorful, full color, and rendering capabilities,
transparent. On the contrary the performance of
inorganic pigments are on the contrary
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2.1.3 Component of Plastics
2. Additive
6) Others
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2.1.4 Classification of Plastics
1. By physical and chemical properties of
plastics
Refers to a kind of plastics ,in a specific
temperature range, can be repeatedly heated
softening and hardening cooling, and its
molecular structure is linear or branched chain
structure (reversible the process of change )
The plastics can be cured into the plastic under
heat or other conditions,which does not melt
insoluble substances.And its final structure of
the molecular is three-dimensional structure. (
Irreversible the process of change )
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2.1.4 Classification of Plastics
2.By the use of plastic
Generally refers to the high production, broad
use , good forming, cheap plastic.
Engineering Plastics
General can withstand a certain amount of
external force, with good mechanical properties
and dimensional stability, still maintain their
excellent performance at low or high
temperatures, can be used as an engineering
structural plastic
Specific Plastics
Generally refers to plastic has a special
function (such as heat-resistant,
self-lubricating, etc.)which is applied to the
special requirements of plastic.
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2.1.5 Features of Plastics
1. Light weight, high specific strength.
2. Excellent electrical insulation properties.
3. Excellent chemical stability.
4.Reduce friction, excellent wear-resisting
property
5. Transmittance and protective properties.
6. Shock absorption, excellent noise reduction.
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2.2 Rheological Properties of Polymer
2.2.1 Newtonian flow law
Center line
moving layer
Analysis of the shear strain dx/dr relative
movement distance between two adjacent liquid
layer, that is, the shear fluid under shear
stress, denoted as follows ?dx/dr
Friction
wall
Fixed layer
Laminar flow model
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2.2.2 Power Law Flow Rules And Apparent
Viscosity
In injection molding , the majority of polymer
melts are non-Newtonian fluid, and approximately
obey the flow of power law rules ,that is
Where, K is a constant depending on temperature
and polymer, reflecting the viscosity of the
polymer melt n, the index of non-Newtonian
,depends on temperature and polymer, reflecting
deviation degree of the polymer melt from the
Newtonian nature.
Flow equation
Rheological equation
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Different Types of Fluid Flow Curve
Shear stress
Shear rate
Different Types of Fluid Flow Curve
1.Hamm liquid 2.Intumescent liquid 3.Newtonian
fluid 4.pseudo-plastic liquid 5. composite fluid
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Different Types of Fluid Flow Curve
Apparent viscosity
Shear rate
Different Types of Fluid Flow Curve
1.Instumescent liquid 2. Newtonian fluid 3.
pseudo-plastic liquid
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Different Types of Fluid
nlt1,known as pseudo-plastic fluid ngt1,known as
the expansion fluid n1,Newtonian fluid ,(The
liquid which can mobile only when the shear
stress reaches or exceeds a certain value called
Binha fluid )
In injection molding, in addition to
thermosetting polymer and a small number of
thermoplastic polymers, most of the polymer melt
of pseudo-plastic fluid have approximate
rheological properties. The cases of expansion
and Binha fluid polymer are mostly the
suspensions of higher solids content ,and with
the gel structure of the polymer solution.
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Summary of Polymer Fluids
Flow types Flow Law Corresponding Fluid Comment
Newtonian fluid                                   (? constant) PC approximate Low molecular mostly belongs to this type
Binha fluid                                               (ty and ? are constants) Gel paste, a concentrated solution of good solvent Can only flow when the shear stress increases to a certain value
pseudoplastic liquids                                   nlt1 Most of the polymer melt, solution, paste Shear increases, the viscosity decreases. Reason are the molecular "unwrapping"
expansion fluid                                    ngt1 High solids content of the paste Shear increases, the viscosity increased.
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2.2.3 Influencing Factors for flowability

• External Factor
• Internal Factor

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External Influencing Factors To
flowabilityTemperature

• Temperature enable the thermal motion of the
  polymer macromolecules and make intermolecular
  distance increases, thereby reducing ?a. The
  greater the gravity and the rigidity of the
  polymer chains are,the greater intermolecular
  sensitivity of ?a to temperature is. Sensitivity
  of ?a to temperature in general is stronger than
  to shear stress or to shear rate.In molding
  operation, some polymer whose ?a does not change
  obviously with temperature(such as PP, PE, POM),
  its not appropriate to increase the temperature
  alone to improve their filling mold ability.
  Furthermore, greatly increasing the temperature
  is likely to cause thermal degradation,thereby
  reducing the quality of products.In addition ,it
  also cause the loss of the molding equipment and
  deterioration of working conditions.
  Relatively,increasing temperature ,in the
  molding, is feasible to reduce the viscosity of
  PMMA, PC ,PA-66 and other polymer melt, because
  ?a will fall much without obvious temperature
  increase. 
• Temperature sensitive plastics
• Polymers,such as PC, PMMA , with high molecular
  chain rigidity,whose viscosity decreased
  significantly with the increasing temperature. 

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External Influencing Factors To flowabilityShear

• Filling mold ability can be changed by adjusting
  the shear stress or shear rate. But pay attention
  to the shearing sensitive polymer melt, the Screw
  speed or pressure must be strictly controlled, or
  small changes of the shear rate will cause the
  significant viscosity changes, resulting in
  adverse surface, uneven filling, density
  unevenness, or other ills.
•  Shear sensitive plastics
• Polymer ,such as PE PP PS ,with high molecular
  chain flexibility ,whose viscosity decreases
  significantly while shear rate or shear stress
  increases .

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External Influencing Factors To flowability
Hard chain
Soft chain
Soft chain
Hard chain
The effect of temperature on the melt viscosity
The effect of shear stress (or rate) on the melt
viscosity  
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External Influencing Factors To
flowabilityPressure

• Generally compression of low molecular is not
  very high, increasing pressure has little effect
  on its viscosity. However, long-chain structure
  and molecular chain rotation of polymers result
  in more empty, so the compression of such
  polymers in the compression processing
  temperature are much larger than ordinary fluid
  .Under high pressure (in injection molding,
  compression increases to 35-300MPa), volume of
  polymer shrink significantly ,intermolecular
  forces increases even more than tenfold , and so
  is viscosity, thus affecting the flowability.
• The pressure sensitivity varies depending on the
  polymer structure.Under normal circumstances,
  viscosity of polymer with a bulky phenyl
  polymers, low molecular weight, low density is
  influenced apprently by pressure.But the pressure
  is very complex, and the law is not obvious, so
  pressure can be negligible at lower pressure
  while a specific treatment should be taken to
  the high pressure under specific circumstances .

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Internal Influencing Factors To flowabilityRaw
material

• 1?The polarity of the molecular chain
• The greater the polarity is, the higher the
  viscosity is , and the worse the flowability is.
  
• 2?Molecular weitht
• The bigger molecular weight is, the higher the
  viscosity is , the worse the flowability is.
• 3? Molecular weitht distribution
• The wider molecular weight distribution is, more
  obviously the shear rate increases,more
  significantly the viscosity decreases .
• 4?Additive(Rigidity additive,Flexibility
  additive)
• Rigidity additive increases vuscosity while
  flexibility additive decreases.

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Internal Influencing Factors to flowability
effect of molecular weight on polymer viscosity
effect of molecular weight on polymer viscosity
wide
narrow
effect of molecular weight distribution on
polymer viscosity
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2.3 Physical And Chemical Changes in Polymer
processing

• Viscoelasticity
• Crystallization
• Orientation
• Degradation
• Cross-linking

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Elastic Behavior of Polymer Fluid
Polymer viscous flow is accompanied of
high-elastic deformation to a certain degree, and
the high-elastic deformation is reversible. After
the disappearance of the external force, polymer
chains curl up, and thus the entire deformation
will restore sort of. This flow process can be
signaled as follows This elastic deformation
of the polymer melt and the subsequent relaxation
have an effect on the appearance of the
dimensional stability of the products.
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Recoverable Shear Deformation
The recovery process of high-elastic
deformation is a relaxation process. The speed
of recovery on the one hand is related to the
polymer flexibility of itself .High flexibility
facilitate the recovery while low flexibility
cause the slow flexibility. On the other hand,
when temperature is high, recovery is fast while
low-temperature recovery is slow.
Recoverable shear deformation
Viscous flow deformation
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Balus Effect
DefinitionThe phenomenon that the diameter of
the polymer melt extruded by extrusion machine is
larger than that of the extrusion die hole.
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Unstable Flow

• Wave-shape

• Sharkskin-shape

• Bamboo-shape

• Spiral-shape

• Irregular rupture

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Crystallization

• Crystal structure
• ?
• Polymer chain queue Regularity, neatly, tightly
  ?
  ?
• Interaction between molecular chain increases,
  Chain segment move difficultly
• 
  ?
• Affect a variety of macroscopic properties

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effect of Crystallization on polymer performance

• Mechanical Property
• Modulus?rigidity?elongation?impulse
  strength?
• tensile strength?
• Mechanical Property related to crystal structure
•   Spherulites scale ? elongation ? impulse
  strength ? modulus ?strength-
• ?other properties
• Thermal property? solvent resistance?
  solvent property? air permeability? density?
  glossiness?
• optics transparency?

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The relationship between degree of
crystalline,molecular weight and performance of
polyethylene(PE)
Crystalline
Brittle wax
Hard plastic
Hard wax
Soft plastic
Soft wax
Resin like
molecular
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Orientation

• Polymer molecules or filler is ordered along the
  direction of the force .
• Including the preferred arrangement of the
  orientation of molecular chain, chain segment
  and crystalline polymer chip along the direction
  of the external force.
• un-oriented Polymer is isotropic, that is, the
  same performance in all directions. After
  orientation, mechanical properties has been
  strengthened in the direction of orientation. In
  the direction perpendicular to the orientation,
  mechanical properties may be weakened . That is,
  oriented polymer is anisotropy in all directions.
  
• Orientation Classification
• Flow Orientation( induced by the shear force when
  flowing )

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Fiber Filler Orientation In Molding process

• The packing arrange along the flow direction,
  once hitting the blocking force (such as the die
  wall, etc.), it flows into the direction
  vertical to the blocking force.

gate
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Polymer Molecules Orientation During
Thermoplastic Molding Process

• Once there is some melt flow in the production
  process using thermoplastic, external factors
  influencing orientation , as well as the
  consequences due to orientation in the products
  are basically is concerned , regardless of the
  change in the method of production .
• Flow orientation will result in anisotropic
  products, generally not wanted, for the internal
  stress accompanied by orientation.

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Sample of A Long Strip --- Flow Orientation

• The degree of gathering depends on the size of
  the shear force, the operating time, the degree
  of solution-oriented

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Factors Influencing Orientation

• With the increase temperature in molding ,
  product thickness ( cavity depth), and the
  temperature the plastic entrying into the mold
  with , the orientation degree weakened
• As the gate length, pressure, and the fill time
  increase, the degree of molecular orientation
  also increased
• Orientation Degree is very related to the
  position and shape the gate. In order to reduce
  orientation, the gate is preferably located in
  the very deep cavity.

Flow orient
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Tensile Orientation of Polymer

• If polymer molecules are in the temperature
  between Tg and Tm, stretched in one direction,
  the molecular chain will neatly arranged along
  the stretching direction, that is, molecules is
  directed in the stretching process .
• Due to the orientation and the increase
  attraction between the molecular chains caused
  by orientation, stretching orientation and
  rapidly cooling the products to room temperature
  will greatly improve tensile strength in the
  tensile direction, the anti-creep performance .
• for thin film, if the stretch is in one
  direction, this method is called uniaxial tension
  if it is stretched in the horizontal ,straight
  two directions, then called the two-way stretch
  (or biaxial stretch).

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Orientation State Structure of Polymer

• Amorphous Orientations without
  crystalline
• Crystallization of unoriented
  Crystallographic orientation

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Heat Treatment

• If the film having being stretched or other
  products in the tension are heated (usually a few
  seconds) within the region of a suitable
  temperature above the stretching temperature but
  below the melting point, then quenched to room
  temperature, the shrinkage lowered greatly.

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Degradation

• Degradation Under the influence of light , heat
  , oxygen and other external factors, the
  molecular weight of polymer chemical structure
  decreases, leading to the decline in appearance
  and mechanical properties.
• Degradative Classification
• Thermal Degradation
• Oxidative Degradation
• Force Degradation
• Water Degradation

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Cross-linking

• In the molding industry, the term cross-linking
  is often replaced by hardening, aging.
• The so-called "hardened well" or "hardened
  completely" does not mean that cross-linking
  operates completely, but rather refers to that
  the cross-linking operates to the one of the most
  appropriate extent. The physical - mechanical
  properties of the products reach the best realm.
  Commonly hardening greater than 100 is called
  "overripe", otherwise it is "less ripe".

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2.4 Plastic Process Performance
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2.4.1 Thermoplastic Plastics Process
Performance
1.Shrinkage
The performance that dimensions of all
parts of the plastic products , removed from the
mold, cooled to room temperature, is narrower
than the original size in the mold , is called
shrinkage.
Ways of Molding Shrinkage
?The line dimensions shrink of plastic parts
?Shrinking direction
?After shrinkage
?Post-processing shrinkage
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2.4.1 Thermoplastic Plastics Process
Performance
1.Shrinkage
The basic factors affecting the contraction
? Plastic varieties ? Plastic features ? Form,
size, distribution of the feed inlet ? Molding
conditions
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2.4.1 Thermoplastic Plastics Process
Performance
1.Shrinkage
Calculation of shrinkage
Where,
-- Actual shrinkage () --
Calculated shrinkage () a -- one-way size
of the plastic in the molding
temperature (mm) b - one-way size of the
plastic in the room temperature
(mm) C - one-way size of the mold for
plastic in the room temperature (mm)
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2.4.1 Thermoplastic Plastics Process
Performance
2. flowability
The ability of plastic to fill the cavity in a
certain temperature and pressure.
Good flowability, Medium flowability, Poor
flowability
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2.4.1 Thermoplastic Plastics Process
Performance
2.flowability
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
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2.4.1 Thermoplastic Plastics Process
Performance
7.Compatibility(Blending)
Means the capacity that two or more different
varieties of plastic does not produce mutual
separation in the molten state.
8. Plastic state and processing
Melt spinning molding
Injection Molding
Film blow molding
Extrusion Molding
Calendering Molding
Blow Molding
Vacuum and pressure molding
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2.4.2 Thermosetting Plastics Process Performance
1.Shrinkage
The manifestations of shrinkage, affecting
factors and methods of computation of the
thermosetting plastic are basically the same as
thermoplastic .
2.flowability
Thermosetting plastic flow is usually
expressed by the Lassig flowability (in mm), the
bigger the value is, the better flowability is.
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2.4.2 Thermosetting Plastics Process Performance
2.flowability
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2.4.2 Thermosetting Plastics Process Performance
2.flowability
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2.4.2 Thermosetting Plastics Process Performance
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2.4.2 Thermosetting Plastics Process Performance
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2.4.2 Thermosetting Plastics Process Performance
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2.4.2 Thermosetting Plastics Process Performance
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
ABS203050
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
2.5.1 Thermoplastic Plastics
12. Glass Mat Reinforced Thermorplastic (GMT)

• GMT is a Thermoplastic pre-preg, is a kind of
  rigid sheets. The pre-heated sheets are then
  molded by compression at a lower temperature.
  During the molding GMT flows inside the mold
  cavity, allowing complex features to be formed.
• offers better mechanical properties due to the
  higher residual length of the glass strands.
• GMT is widely used in automotive applications
  such as underbody shields, seat structures, and
  front-ends.

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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
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2.5 Commonly Used Plastics
2.5.2Thermosetting Plastic
SMC--Sheet Molding Compound
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2.5.3 plastic application on automobile
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Car Door

• Main part-PPTALC,ABS
• handleABS,PC/ABS,PPTALC

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dashboard
project Hard dashboard soft dashboard soft dashboard
project Hard dashboard frame surface
Processing method Injection, spray painting injection (1)Slush molding 2)Vacuum molding
material PPTALC, PC/ABS PC/ABS. PPO, (1)PVC Slush powder (2)PVC/ABS sheet
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Dashboard kit

• bag
• PP,or ABS
• Vice Dashboard
• PPEPDMTALC
• air outlet
• ABS, PC/ABS
• Decorate- Electroplating ABS, PC/ABS

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bumper
Modified PP
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Induction manifold
PA66 GF35 PA6 GF30 PA66 GF30
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car roof

• GMT or LD-GMT

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lamp
front lamp PC, Back lamp PMMA, modified PP or
ABS (LAMP SHELL)
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2.5 Commonly Used Plastics
BMC/SMC application
1.car body Bumper, fender, wheel guard, guide
plate, door, roof, etc.. 2. chassis parts Side
Skirt , splash guard, etc.. 3. engine
parts rocket cover, oil filter cover, etc..
Auto Applications