Transcript Mechanical Properties of Polymers

Lecture 4:
Characterizing Hybrids
First step in characterizing a hybrid:
• Use your senses (take pictures to document)
– What color? Does it fluoresce
– Transparent or opaque?
– Homogeneous in appearance?
– Solid or liquid
– Tacky or sticky or brittle or tough
• Mass – compare with theoretical yield
Describe the material below
Describe the material below
Second, try and dissolve the hybrid
in different solvents
• Water, ethanol, benzene, methylene chloride,
tetrahydrofuran, acetonitrile, hexane,
acetone, diethyl ether, dimethyl sulfoxide, Nmethyl pyrrolidone (NMP)
• Leave it at room temp overnight. Look for
swelling if not dissolved.
• Boil solvent for 4 hours.
• If it doesn’t dissolve its probably cross-linked
or really crystalline
Types of Polymers & solubility
Will dissolve
Won’t dissolve
Third, Structural Characterization
of soluble polymers
• 1H & 13C & 29Si Nuclear Magnetic Resonance
and infrared spectroscopy
• Molecular weight by gel permeation
chromatography
• Composition by combustion analyses
• X-ray diffraction on film or powder
• Viscosity of dilute solutions- shape of polymer
X-ray diffraction
amorphous
materials
shows diffuse
band
Semi-crystalline
polymer shows
diffraction rings
Or third, Structural Characterization
of insoluble polymers
• Harder to characterize
• Does it burn (many inorganics do not)
• Solid state 1H & 13C & 29Si Nuclear Magnetic
Resonance and infrared spectroscopy
• Composition by combustion analyses
• X-ray diffraction on film or powder
• X-ray fluorescence if inorganic
Literature procedure:
See how experimentals are written in good papers. Use them as model
Template for lab notebook:
Template for research labnotebook:
Morphological Characterization of
polymers
• If opaque or transluscent, SEM and optical
microscopy (bifringence)-crystalline or
amorphous & more.
• Fracture polymer and look at fracture surfaces
• Look for phase separation (like immiscible
block copolymers)
• Look for long range order
• Look for pores
Thermal characterization of
polymers
• Thermal gravimetric analyses (TGA) –
determines decomposition temperature
• Differential scanning calorimetry (DSC)–
detects phase changes (melting or glass
transition temperatures) or chemical
reactions
DSC analysis
Thermal gravimetric analysis
Mechanical characterization of
polymers
• Stress-strain curves:
– Young’s modulus (brittleness)
– Tensile strength-pull sample appart
– Flexural strength- bend until it breaks
– Compressive strength-crush sample
• Dynamic mechanical analyses (same info as above but
with cyclic application of stress or strain.
– Generate modulus temperature curves
– Fatigue studies to predict failure under cyclic stress
Stress-Strain Analysis
Not every polymer needs all of these
analyses, but structure is the most
basic and important
• Known (described in literature) polymers
need less structural characterization. Often
just IR and Mw from GPC.
• New polymers need complete structural
characterization: NMR, IR, Combustion
analysis, GPC, solubility, glass transition temp
and/or melting point.
Morphological and Mechanical studies are
dependent on research interests.
• If you are interested in strong polymers, then
morphological, mechanical & thermal studies
are important
• Other applications requiring morphological,
mechanical & thermal studies would include
preparation and testing of 1) membranes, 2)
coatings, 3) paint, 4) polymer foams, 5)
organic photovoltaics, 6) OLED’s, 7) adhesives
and 8) low friction coatings
Other polymer properties that are
important for specialty polymers
• Coatings, packaging, membranes, Photovoltaics &
OLED’s; gas and water permeability should be measured.
• Battery and fuel cell membranes: gas & water
permeability and ion conductivity
• Dielectrics, wiring insulation: dielectric and electrical
conductivity
• Fabrics & building materials: fire resistance
• Any polymer used in sunlight or radiation or in the
presence of chemicals: resistance to oxidative
degradation.