Organic Chemistry, Polymers, Elastomers and Adhesives

Introduction

Mechatronic systems combine mechanical structures, electronics, sensors, actuators, control systems and software. Organic materials are important in nearly every part of such systems: polymer housings protect electronics; insulating films separate conductors; elastomers provide seals and vibration isolation; adhesives join dissimilar materials; and coatings control friction, corrosion, electrical insulation and optical performance.

Engineering chemistry provides the language needed to select these materials rationally. The selection cannot be based only on strength or cost. A polymer may have excellent stiffness but fail because its glass-transition temperature is too low. An adhesive may bond strongly in a laboratory test but fail under humidity, thermal cycling or peel loading. An elastomer may seal effectively but swell in contact with oil. Consequently, material selection requires an understanding of molecular structure, processing, mechanical response, thermal transitions, chemical resistance and failure mechanisms.

Learning Objectives

After studying this chapter, the student should be able to:

1. Recognize major organic functional groups and common organic reaction types.
2. Distinguish thermoplastics, thermosets and elastomers.
3. Explain addition, condensation and ring-opening polymerization.
4. Relate molecular weight, molecular-weight distribution, branching and cross-linking to properties.
5. Explain crystallinity, melting temperature, glass-transition temperature and viscoelasticity.
6. Describe polymer degradation and methods for improving service life.
7. Select polymers, elastomers, adhesives and coatings for mechatronic components.
8. Evaluate an engineering material choice using environmental, manufacturing, safety and sustainability criteria.

1. Organic Chemistry as a Materials Foundation

Organic chemistry is primarily the chemistry of carbon compounds. Carbon forms four covalent bonds and can create chains, branches, rings and three-dimensional networks. The properties of an organic material depend not only on its elemental composition but also on molecular architecture and intermolecular forces.

1.1 Bonding and molecular structure

Most polymeric engineering materials contain carbon–carbon, carbon–hydrogen, carbon–oxygen, carbon–nitrogen, silicon–oxygen or carbon–halogen bonds. Strong covalent bonds form the molecular backbone, whereas weaker intermolecular forces act between chains. These include dispersion forces, dipole–dipole attraction and hydrogen bonding.

Molecular flexibility is affected by bond rotation, bulky side groups and backbone geometry. A flexible chain generally produces a lower glass-transition temperature and greater ductility. Rigid aromatic rings, strong intermolecular attraction and close packing generally increase stiffness and thermal resistance.

1.2 Major functional groups

A functional group is an atom or group of atoms responsible for characteristic chemical behavior.

The symbols R and R′ denote organic groups whose detailed structures may vary.

1.3 Common organic reaction types

Addition reactions occur when atoms add across a multiple bond. In alkene polymerization, the double bond opens and connects monomer molecules without producing a small-molecule by-product.

Condensation reactions join molecules while eliminating a small molecule, commonly water, methanol or hydrogen chloride. Polyesters and polyamides are often produced by condensation reactions.

Substitution reactions replace one atom or group with another. They are important in the synthesis and modification of polymer precursors.

Oxidation and reduction change the oxidation state or bonding environment of atoms. Oxidation of polymers by heat, light or oxygen can cause chain scission, discoloration and loss of strength.

Cross-linking reactions connect polymer chains into a network. Vulcanization of rubber and curing of epoxy resins are important examples.

2. Polymer Architecture and Classification

A polymer is a substance composed of very large molecules, or macromolecules, formed from repeating structural units. A monomer is the smaller molecule from which a polymer is made. The repeat unit is the structural segment repeated along a chain.

2.1 Addition, condensation and ring-opening polymerization

In chain-growth addition polymerization, reactive centers such as free radicals, cations, anions or metal catalysts add monomers successively. A simplified representation for ethene is:

Here, n is the number of monomer units incorporated. The equation represents polyethylene formation and assumes suitable initiation and termination conditions.

In step-growth condensation polymerization, molecules bearing two or more reactive functional groups react progressively. For a polyester, a diol and a dicarboxylic acid may react while eliminating water:

The exact stoichiometric coefficient depends on how end groups and molecular chains are counted; the essential feature is ester formation with elimination of water.

Ring-opening polymerization converts cyclic monomers into linear or lightly branched chains. It is used for materials such as polycaprolactone and some polyurethanes. Because the monomer ring strain or reactive functionality drives the process, the method can produce polymers with controlled structures.

2.2 Polymer classes

Thermoplastics soften when heated and harden when cooled, usually without a chemical change during each cycle. They can often be remelted and reshaped. Examples include polyethylene, polypropylene, polyamide, polycarbonate, polyoxymethylene and polyether ether ketone.

Thermosets form permanent three-dimensional networks during curing. Once cured, they do not melt; excessive heating causes degradation. Epoxy, phenolic and many unsaturated polyester resins are thermosets.

Elastomers are lightly cross-linked polymers capable of large, mostly reversible deformation. Natural rubber, nitrile rubber, silicone rubber, EPDM and fluoroelastomers are examples.

Fibres are polymers processed into highly oriented, relatively narrow structures with high tensile strength and modulus, such as aramid and ultra-high-molecular-weight polyethylene fibres.

2.3 Molecular architecture

Polymer chains may be linear, branched, cross-linked or networked. Linear chains can pack efficiently and may crystallize. Branching usually reduces packing efficiency and density but can improve flexibility and impact resistance. Cross-linking restricts chain motion, increases dimensional stability and reduces solubility. Excessive cross-linking, however, can make a material brittle.

Copolymers contain two or more chemically different monomers. They may be random, alternating, block or graft copolymers. Copolymerization allows engineers to combine properties, for example toughness with chemical resistance or flexibility with strength.

3. Molecular Weight and Its Engineering Meaning

Polymer samples contain chains of different lengths. Therefore, a single molecular weight is usually insufficient to describe them.

The number-average molecular weight is:

where Nᵢ is the number of molecules having molecular weight Mᵢ. The weight-average molecular weight is:

The conventional symbol is often Mᵥ for weight-average molecular weight, although M_w is also widely used. In this chapter, Mᵥ denotes the weight-average value to avoid confusion with a mass symbol. Both quantities have units such as g mol⁻¹.

Polydispersity, or dispersity, is:

For an ideal sample containing chains of exactly one length, Đ = 1. Real polymer samples generally have Đ > 1. A broader distribution can affect processing, toughness, melt viscosity and crystallization.

For an ideal linear step-growth polymerization with equal stoichiometric functional-group concentrations, Carothers’ relationship is:

where Xₙ is the number-average degree of polymerization and p is the fraction of functional groups that has reacted. The equation assumes equal reactivity of functional groups, no significant cyclization, and exact stoichiometric balance. At p = 0.99, Xₙ = 100. This illustrates why very high conversion is required to obtain high molecular weight in step-growth polymerization.

Higher molecular weight generally increases toughness, entanglement and melt viscosity, but it may reduce ease of processing. The relationship is not unlimited: a polymer can become difficult to mold, and other factors such as crystallinity and cross-link density may dominate performance.

4. Thermal, Mechanical and Structural Behavior

4.1 Crystallinity

A semicrystalline polymer contains ordered crystalline regions dispersed in amorphous regions. Crystallinity is favored by regular, linear chains, small side groups, slow cooling and sufficient time for chain organization. Branching, random copolymerization and bulky substituents generally reduce crystallinity.

Crystalline regions increase density, stiffness, chemical resistance and dimensional stability. They can also reduce transparency and impact toughness. The amorphous phase contributes to ductility and energy absorption.

The degree of crystallinity by mass may be estimated from calorimetry using:

where X_c is percentage crystallinity, ∆H_m is measured melting enthalpy, ∆H_cc is cold-crystallization enthalpy, and ∆H_m^0 is the melting enthalpy of a completely crystalline reference polymer. All enthalpies must use the same units, commonly J g⁻¹. The correction for cold crystallization is necessary when crystallization occurs during heating.

4.2 Glass transition and melting

The glass-transition temperature, T_g, is the approximate temperature range at which amorphous polymer regions change from a hard, glassy state to a softer, rubbery state. It is not a first-order melting point and occurs over a range rather than at one perfectly sharp temperature.

The melting temperature, T_m, is associated with the loss of ordered crystalline domains. Amorphous polymers do not have a true equilibrium melting temperature, although they have a glass transition and may soften progressively.

A component intended to remain rigid should generally operate sufficiently below T_g. An elastomer normally operates above T_g, where its chains can move, but below temperatures at which degradation or excessive softening occurs. Actual design margins must account for frequency, time, humidity, plasticizers and thermal history.

4.3 Viscoelasticity

Polymers exhibit both elastic and viscous behavior. Elastic deformation is recoverable and stores mechanical energy; viscous deformation is time-dependent and dissipates energy.

For a simple linear elastic response:

where σ is stress in pascals, E is Young’s modulus in pascals, and ε is dimensionless strain. This equation applies only within the approximately linear elastic range and does not describe long-term polymer creep by itself.

A useful measure of damping is the loss tangent:

where E′ is the storage modulus and E″ is the loss modulus. A high tan δ indicates greater energy dissipation. This is useful when selecting vibration isolators, actuator mounts and damping layers.

Creep is increasing strain under constant stress. Stress relaxation is decreasing stress under constant strain. Both become more rapid at higher temperature and near T_g. Time–temperature superposition is often used to estimate long-term behavior from shorter tests, but it assumes that temperature mainly shifts the rate of molecular motion without changing the deformation mechanism.

5. Degradation and Failure

Polymer degradation changes molecular structure and therefore performance. Important mechanisms include:

• Thermal degradation: chain scission, depolymerization or cross-linking caused by excessive temperature.
• Thermo-oxidative degradation: reaction with oxygen accelerated by heat; often causes embrittlement and discoloration.
• Photodegradation: ultraviolet radiation generates radicals and breaks chains.
• Hydrolysis: water attacks susceptible bonds, especially esters, amides and carbonates at elevated temperature or extreme pH.
• Chemical attack: solvents may dissolve, swell, extract additives or crack polymers.
• Mechanical fatigue: repeated stress produces cracks even when individual loads are below the short-term strength.
• Environmental stress cracking: a combination of tensile stress and a chemically aggressive environment produces brittle cracks.

Stabilizers include antioxidants, ultraviolet absorbers, hindered-amine light stabilizers, hydrolysis-resistant formulations and protective coatings. Design practices include avoiding sharp notches, controlling processing temperature, limiting residual stresses, selecting compatible cleaners and specifying appropriate storage conditions.

Recycling is complicated by contamination, additives, mixed polymers and degradation during reprocessing. Thermoplastics are generally more amenable to mechanical recycling than cross-linked thermosets and elastomers. Chemical recycling and reuse of thermoset networks are developing technologies but require energy, separation and economic justification.

6. Elastomers for Mechatronic Systems

Elastomers are selected when large reversible deformation, sealing, impact absorption or vibration isolation is required. Their behavior depends on molecular flexibility, cross-link density, fillers, plasticizers and temperature.

Sealing design must consider compression set, pressure, surface finish, temperature, fluid compatibility and movement. A material that resists oil may still fail because it takes a permanent compression set. Silicone is attractive for electrical insulation and temperature range but may be unsuitable for high-abrasion sliding contact.

7. Adhesives and Coatings

An adhesive joins surfaces through adhesion to the substrates and cohesion within the adhesive layer. Good bonding requires wetting, intimate contact and suitable interfacial chemistry. Surface contamination, weak boundary layers, excessive bond-line thickness and moisture are common causes of failure.

7.1 Adhesive families

Epoxy adhesives offer high cohesive strength, good dimensional stability and strong bonding to metals, ceramics and many composites. They are widely used for sensor mounting, electronic potting and structural joints. Many are brittle unless toughened.

Acrylic adhesives cure rapidly and bond many plastics and metals. They can tolerate some surface contamination but may have odor or shrinkage concerns.

Cyanoacrylates cure rapidly in thin layers with moisture assistance. They are useful for small fixtures but may be brittle, have limited gap filling and produce surface blooming.

Polyurethanes provide toughness and flexibility and are useful for dissimilar-material joints. Moisture sensitivity and long-term hydrolysis must be considered.

Silicone adhesives and sealants remain flexible over broad temperatures and provide weather resistance and electrical insulation, but their cohesive strength is usually lower than that of structural epoxies.

Pressure-sensitive adhesives form bonds under pressure and are used for labels, flexible circuits, films and low-load mounting. Their performance is strongly time- and temperature-dependent.

7.2 Adhesive joint design

Adhesive joints perform best when loads are distributed in shear or compression. Peel and cleavage loads concentrate stress near an edge and are generally unfavorable. A longer overlap can increase load capacity, but excessive thickness may reduce stiffness and increase creep. The optimum bond-line thickness depends on the adhesive, geometry and process capability.

Surface preparation may involve degreasing, abrasion, plasma treatment, chemical priming or corona treatment. The selected method must not damage the substrate or leave harmful residues. Cure time, temperature, mix ratio and humidity must be controlled according to the manufacturer’s technical data.

Coatings protect surfaces or provide a special function. Examples include conformal coatings for printed circuit boards, anti-corrosion coatings for metal frames, low-friction coatings for mechanisms, dielectric coatings for electrical insulation and hard coatings for optical or wear surfaces.

A coating must be compatible with the substrate, sufficiently adherent, uniform in thickness and resistant to the intended environment. Conformal coating selection requires attention to dielectric strength, moisture resistance, repairability, outgassing and thermal expansion mismatch.

8. Materials Selection for Mechatronic Components

A systematic selection process begins by defining the service environment and failure consequences. Relevant questions include:

1. What loads, displacements, vibration and impact will occur?
2. What are the minimum and maximum temperatures, and how long will exposure last?
3. Will the component contact water, oils, fuels, solvents, dust or salt spray?
4. Are electrical insulation, dielectric strength, electromagnetic transparency or grounding required?
5. What tolerances, surface finish, assembly method and production volume apply?
6. Is flame behavior, toxicity, outgassing or regulatory certification important?
7. Can the material be repaired, recycled or safely disposed of?

A thermoplastic is often preferred for an injection-molded housing because it offers high production rate and integrated features. A thermoset epoxy may be preferred for rigid encapsulation or a high-strength bond. A silicone elastomer may be chosen for a flexible environmental seal, while NBR is more appropriate for petroleum-fluid exposure.

Material datasheets must be interpreted carefully. Tensile strength measured at room temperature for a short duration does not guarantee fatigue life, creep resistance or environmental durability. Values may vary with specimen geometry, moisture conditioning, molding direction, strain rate and test standard. Design validation should include representative thermal, mechanical, chemical and electrical testing.

Worked Example: Selecting a Seal Material

An actuator gearbox requires a seal exposed to mineral oil, temperatures from −20 °C to 110 °C, intermittent vibration and outdoor ozone. Candidate materials are EPDM, NBR and silicone rubber.

EPDM has excellent ozone and weather resistance but poor mineral-oil resistance, so it is rejected despite its outdoor advantage. Silicone has excellent temperature and weather resistance but may have inadequate abrasion and tear resistance for a dynamic oil seal. NBR offers good mineral-oil resistance and adequate mechanical strength, but its ozone resistance is lower than that of EPDM.

The rational preliminary choice is oil-resistant NBR, possibly with an ozone-resistant formulation or protective geometry that reduces exposure. If the seal must tolerate substantially higher temperature or aggressive fuels, a fluoroelastomer should be considered despite its greater cost. Final selection requires testing with the actual oil, pressure, speed, surface finish and duty cycle.

9. Illustrative Case Study: Polymer Housing and Bonded Sensor Mount

Background. An autonomous mobile robot uses a sealed polymer housing containing a camera, inertial sensor and control electronics. A small aluminium sensor bracket is bonded inside the housing. The robot operates outdoors, experiences vibration, and may be exposed to rain, cleaning agents and summer temperatures.

Problem. An initial design used an unfilled ABS housing and a rigid cyanoacrylate adhesive. After several months, some housings warped near the motor, while several sensor brackets detached after thermal cycling.

Analysis. ABS is easy to mold and has good impact resistance, but its dimensional stability and temperature capability may be insufficient near a heat-producing motor. The aluminium and ABS have different coefficients of thermal expansion. A rigid, brittle adhesive creates high interfacial stresses during temperature changes. Surface contamination and inadequate bond-area design further increase the risk of detachment.

Approach and solution. The housing is redesigned using a glass-fiber-reinforced polycarbonate/ABS blend or another qualified engineering thermoplastic with improved heat resistance and stiffness. Ribs are positioned to control deformation without creating severe stress concentrations. The sensor joint uses a toughened two-part epoxy or polyurethane adhesive selected for adhesion to both aluminium and the polymer. The aluminium is degreased, lightly abraded and primed where required. The joint is redesigned to carry shear rather than peel, and a controlled bond-line thickness is introduced. Thermal cycling, vibration, humidity and chemical-cleaner tests are performed on assembled units.

Outcome. The revised design is expected to reduce housing distortion and distribute thermal mismatch more effectively. The adhesive joint has greater toughness and improved resistance to peel and thermal cycling. Production instructions specify surface preparation, adhesive mixing, cure time and inspection.

Learning points. Material selection must consider the complete assembly rather than an isolated datasheet value. Joint geometry, surface preparation and process control can be as important as nominal adhesive strength. Qualification testing should reproduce the actual environment and failure modes.

10. Safety, Regulation and Sustainability

Organic materials may release volatile organic compounds, residual monomers, plasticizers or decomposition products. Safety data sheets must be consulted for handling, curing, ventilation, storage and disposal. Uncured resins and hardeners can cause sensitization or chemical burns even when the cured polymer is relatively inert.

Fire behavior is critical in electronic and transportation equipment. Flame-retardant additives can improve performance but may affect mechanical properties, processing, environmental profile and end-of-life options. Regulatory requirements may restrict certain substances, particularly in electrical and electronic equipment.

Engineers should avoid unnecessary material complexity, specify recyclable thermoplastics where feasible, design for disassembly and minimize excessive adhesive use when mechanical joining is practical. Sustainability assessment should include raw-material production, manufacturing energy, service life, repairability and disposal rather than focusing only on bio-based content. A longer-lasting component can have lower total environmental impact than a nominally renewable material that fails early.

Contemporary Developments

Current developments include recyclable thermoplastic composites, bio-based monomers, vitrimer networks that can be reprocessed through dynamic covalent bonds, electrically conductive polymer composites, self-healing coatings and additive manufacturing of functional polymer parts. Polymer nanocomposites can improve barrier, thermal or electrical properties at low filler concentrations, but dispersion, health, cost and end-of-life issues require careful evaluation.

Digital manufacturing and AI-assisted materials informatics can accelerate formulation screening and process optimization. However, predictions depend on reliable data and must be confirmed by physical testing. AI does not remove the need to understand failure mechanisms, uncertainty, standards and safety responsibilities.

Best-Practice Selection Checklist

• Define mechanical, thermal, chemical, electrical and environmental requirements.
• Identify whether the material must be thermoplastic, thermoset, elastomeric or adhesive.
• Compare data measured under relevant conditions, not only room-temperature values.
• Check T_g, T_m, creep, fatigue, moisture absorption, chemical compatibility and degradation.
• Design adhesive joints primarily for shear or compression.
• Control surface preparation, cure conditions and bond-line thickness.
• Include thermal cycling, vibration, humidity and chemical testing where relevant.
• Consider fire safety, worker exposure, regulatory compliance and end-of-life management.
• Document assumptions, test methods, acceptance criteria and supplier changes.

Chapter Summary

Organic functional groups determine the reactivity and intermolecular forces of polymer-forming molecules. Addition polymerization generally grows chains from unsaturated monomers, whereas condensation polymerization forms bonds with elimination of small molecules. Polymer properties depend strongly on molecular weight, dispersity, branching, crystallinity and cross-link density.

Thermoplastics soften reversibly on heating, thermosets form permanent networks, and elastomers are lightly cross-linked materials capable of large reversible deformation. Glass transition controls the temperature-dependent stiffness of amorphous regions, while melting describes the loss of crystalline order. Viscoelasticity produces creep, stress relaxation and damping, all of which are important in mechatronic design.

Degradation may result from heat, oxygen, ultraviolet radiation, hydrolysis, chemicals, fatigue or environmental stress cracking. Elastomers must be selected according to fluid compatibility, temperature, ozone, compression set and mechanical duty. Adhesive performance depends on both chemistry and joint design, including wetting, surface preparation, cure and load distribution. Professional material selection integrates performance, manufacturability, safety, regulation, sustainability and validation testing.

Key Terms

Functional group: An atom or group of atoms that gives an organic molecule characteristic chemical behavior.

Monomer: A relatively small molecule capable of reacting to form a polymer.

Polymer: A macromolecular substance consisting of repeated structural units.

Repeat unit: The structural segment repeated along a polymer chain.

Addition polymerization: Chain-growth polymerization involving addition across multiple bonds without eliminating a small molecule.

Condensation polymerization: Polymerization in which bond formation is commonly accompanied by elimination of a small molecule.

Thermoplastic: A polymer that can soften and be reshaped by heating.

Thermoset: A permanently cross-linked polymer network formed during curing.

Elastomer: A lightly cross-linked polymer capable of large, mostly reversible deformation.

Molecular-weight distribution: The distribution of polymer chain lengths in a sample.

Dispersity: The ratio of weight-average to number-average molecular weight.

Crystallinity: The fraction of polymer material arranged in ordered domains.

Glass-transition temperature: The temperature range associated with transition of amorphous polymer regions between glassy and rubbery behavior.

Viscoelasticity: Combined time-dependent viscous and recoverable elastic response.

Creep: Time-dependent strain under sustained stress.

Stress relaxation: Reduction in stress under sustained strain.

Cross-linking: Formation of covalent or strong chemical links between polymer chains.

Adhesion: Interfacial attraction between an adhesive and a substrate.

Cohesion: Internal strength holding an adhesive together.

Environmental stress cracking: Brittle cracking caused by the combined action of stress and a chemically aggressive environment.

Review Questions

Short Answer Questions

1. What is a functional group, and why is it important in polymer chemistry?
2. Distinguish a thermoplastic from a thermoset.
3. Define glass-transition temperature and explain its engineering importance.
4. What is the difference between adhesion and cohesion?
5. Name two mechanisms of polymer degradation.

Long Answer Questions

1. Explain addition and condensation polymerization, including one engineering polymer example for each.
2. Discuss how molecular weight, branching and cross-linking influence polymer properties and processing.
3. Explain crystallinity, glass transition and melting, and relate each concept to component design.
4. Compare NBR, EPDM, silicone rubber and fluoroelastomers for sealing applications.
5. Describe the principles of adhesive joint design, surface preparation and cure control.

Analytical / Application Questions

1. Select a suitable housing polymer for an outdoor mechatronic controller exposed to vibration, moisture and moderate heat. State your assumptions, selection criteria and validation tests.
2. A bonded aluminium bracket repeatedly detaches from a polymer enclosure during thermal cycling. Analyze the possible chemical, mechanical and processing causes and propose a redesign.
3. A polymer gear operates near its glass-transition temperature and develops increasing backlash over time. Explain the likely material mechanisms and recommend design or material changes.

Multiple Choice Questions with Answers

Question 1

Which functional group is characteristic of an ester linkage?

A. R−OH

B. R−COO−R′

C. R−NH₂

D. R−O−R′

Correct Answer: B. R−COO−R′

Question 2

Which statement best describes a thermoset polymer?

A. It can be repeatedly melted without chemical change.

B. It is always a lightly cross-linked elastomer.

C. It forms a permanent network during curing.

D. It contains no covalent bonds between chains.

Correct Answer: C. It forms a permanent network during curing.

Question 3

For ideal step-growth polymerization, what is Xₙ when p = 0.99?

A. 10

B. 50

C. 99

D. 100

Correct Answer: D. 100

Question 4

Which property generally increases when crystalline regions are introduced into a polymer?

A. Dimensional stability

B. Random chain mobility

C. Solubility in all solvents

D. Thermal expansion without limitation

Correct Answer: A. Dimensional stability

Question 5

A polymer operating above its glass-transition temperature is generally more likely to be:

A. Glassy and brittle

B. Rubbery and more flexible

C. Completely crystalline

D. Chemically decomposed immediately

Correct Answer: B. Rubbery and more flexible

Question 6

Which elastomer is generally a poor choice for prolonged contact with petroleum oils?

A. NBR

B. Fluoroelastomer

C. EPDM

D. Polyurethane elastomer

Correct Answer: C. EPDM

Question 7

Which loading mode is generally most favorable for a properly designed adhesive joint?

A. Peel

B. Cleavage

C. Uniform shear

D. Highly concentrated edge loading

Correct Answer: C. Uniform shear

Question 8

In the crystallinity equation, why is cold-crystallization enthalpy subtracted from melting enthalpy?

A. To account for crystallization formed during heating

B. To convert mass into volume

C. To calculate glass-transition temperature

D. To measure adhesive cohesion

Correct Answer: A. To account for crystallization formed during heating

Question 9

Which mechanism involves reaction of susceptible polymer bonds with water?

A. Photolysis only

B. Hydrolysis

C. Vulcanization

D. Plasticization only

Correct Answer: B. Hydrolysis

Question 10

A high loss tangent generally indicates that a polymer:

A. Dissipates more mechanical energy

B. Has zero viscosity

C. Cannot undergo creep

D. Is completely crystalline

Correct Answer: A. Dissipates more mechanical energy