Draw the Structure of Nylon 6 6

Chemical and Biochemical Degradation of Polymers Intended to be Biostable

Arthur J. Coury , in Biomaterials Science (Third Edition), 2013

Polyamides

Nylon 6 (polycaproamide) and nylon 6,6 [poly(hexamethylene adipamide)] contain a hydrolyzable amide connecting group, as do proteins. These synthetic polymers can absorb 9–11% water, by weight, at saturation. It is predictable, then, that they degrade by ion-catalyzed surface and bulk hydrolysis ( Figure II.4.2.1). In addition, hydrolysis due to enzymatic catalysis leads to surface erosion (Zaikov, 1985). Quantitatively, nylon 6,6 lost 25% of its tensile strength after 89 days, and 83% after 726 days in dogs (Kopecek and Ulbrich, 1983). An example of polyamide degradation of particular consequence involved the in vivo fragmentation of the nylon 6 tail string of an intrauterine contraceptive device. This string consisted of a nylon 6-sheath around nylon 6 multifilaments. The combination of fluid absorption (>10%) and hydrolysis was claimed to produce environmental stress cracking. The cracked coating allegedly provided a pathway for bacteria to travel from the vagina into the uterus, resulting in significant pelvic inflammatory disease (Hudson and Crugnola, 1987).

Degradation of a polyarylamide intended for orthopedic use (the fiber-reinforced polyamide from m-xylylene diamine and adipic acid) was also shown in a rabbit implant study. Although the material provoked a foreign-body reaction comparable to a polyethylene control, surface pitting associated with resolving macrophages was noted at 4 weeks, and became more pronounced by 12 weeks. This result was not predicted, since polyarylamides are very resistant to solvents and heat (Finck et al., 1994).

Polyamides with long aliphatic hydrocarbon chain segments (e.g., polydodecanamide) are more hydrolytically stable than shorter chain nylons, and correspondingly degrade slower in vivo.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780080877808000607

PA-6,66 polyamide-6,66

George Wypych , in Handbook of Polymers (Second Edition), 2016

PARAMETER	UNIT	VALUE	REFERENCES
GENERAL
Common name	−	polyamide-6,66, nylon-6,66, poly(hexamethylene adipamide-co-caprolactam)
Acronym	−	PA-6,66
CAS number	−	24993-04-2
HISTORY
Person to discover	−	Owens, J K; Scroggie, A G, 1940. Owens, J K; Scroggie, A G, 1941	Owens, J K; Scroggie, A G, US Patent 2,201,741, DuPont, May 21, 1940; Joyce, R M; Ritter, D M, US Patent 2,251,519, DuPont, Aug. 5, 1941.
Date	−	1940; 1941
Details	−	PA6,66 with improved resistance to carbon arc; catalytic conversion of monomers
SYNTHESIS
Monomer(s) structure	−
Monomer(s) CAS number(s)	−	628-94-4; 105-60-2
Monomer(s) molecular weight(s)	dalton, g/mol, amu	144.17; 113.16
Monomer ratio	−	4:1
STRUCTURE
Crystallinity	%	29
Cell type (lattice)	−	pseudohexagonal
Spacing between crystalline planes	nm	0.37-0.44	Men, Y; Rieger, J, Eur. Polym. J., 40, 2629-35, 2004.
Polymorphs	−	α, γ (also called phases); hydrogen bonds formed between antiparallel chains in α phase and parallel chains in γ phase	Men, Y; Rieger, J, Eur. Polym. J., 40, 2629-35, 2004.
COMMERCIAL POLYMERS
Some manufacturers	−	BASF, EMS
Trade names	−	Ultramid; Grilon
PHYSICAL PROPERTIES
Density at 20°C	g cm⁻³	1.12-1.15; 1.2-1.72 (15-50% glass fiber)
Bulk density at 20°C	g cm⁻³	0.7
Melting temperature, DSC	°C	189-199
Thermal expansion coefficient, 23-80°C	10⁻⁴°C⁻¹	0.6-0.8 (parallel); 0.9-1.2 (normal); 0.2 (15-50% glass fiber, parallel); 1.1 (15-50% glass fiber, normal)
Glass transition temperature	°C	42 (dry); −35 (water saturated)	Men, Y; Rieger, J, Eur. Polym. J., 40, 2629-35, 2004.
Maximum service temperature	°C	80-120; 90-130 (15-50% glass fiber)
Long term service temperature	°C	180-220; 180-200 (15-50% glass fiber)
Heat deflection temperature at 0.45 MPa	°C	200-220
Heat deflection temperature at 1.8 MPa	°C	55-85; 215-230 (15-50% glass fiber)
Dielectric constant at 100 Hz/1 MHz	−	−/3.6 (dry); -/6 (conditioned)
Relative permittivity at 100 Hz	−	3 (dry); 8 (conditioned)
Relative permittivity at 1 MHz	−	3 (dry); 4 (conditioned)
Dissipation factor at 100 Hz	E-4	50 (dry); 1,500 (conditioned)
Dissipation factor at 1 MHz	E-4	150-200 (dry); 700-3,000 (conditioned)
Volume resistivity	ohm-m	1E11 to 1E12 (dry); 1E9 to 1E11 (conditioned)
Surface resistivity	ohm	1E10 to 1E12 (conditioned)
Electric strength K20/P50, d=0.60.8 mm	kV mm⁻¹	26-32 (dry); 25-28 (conditioned); 30-34 (15-50% glass fiber, dry); 27-30 (15-50% glass fiber, conditioned)
Comparative tracking index, CTI, test liquid A	−	600 (dry); 475-600 (conditioned)
Permeability to oxygen, 25°C	cm³ m⁻² day⁻¹ bar⁻¹	14
Permeability to water vapor, 25°C	g m⁻² day⁻¹	25
MECHANICAL & RHEOLOGICAL PROPERTIES
Tensile strength	MPa	45-75 (dry); 50 (conditioned); 110-220 (15-50% glass fiber, dry); 65-155 (15-50% glass fiber, conditioned)
Tensile modulus	MPa	2,200-3,600 (dry); 600-1,600 (conditioned); 5,600-20,000 (15-50% glass fiber, dry); 2,900-13,500 (15-50% glass fiber, conditioned)
Tensile stress at yield	MPa	70-90 (dry); 40-55 (conditioned)
Elongation	%	5-25 (dry); >50 (conditioned); 2-4 (15-50% glass fiber, dry); 2.5-10 (15-50% glass fiber, conditioned)
Tensile yield strain	%	4-5 (dry); 15-18 (conditioned)
Flexural modulus	MPa	3,000 (dry)
Charpy impact strength, unnotched, 23°C	kJ m⁻²	NB to 75-80 (dry); NB to 100 (conditioned); 75-100 (15-50% glass fiber, dry); 90 (15-50% glass fiber, conditioned)
Charpy impact strength, unnotched, −30°C	kJ m⁻²	NB to 70-80 (dry); NB to 60 (conditioned); 60-80 (15-50% glass fiber, dry); 70-80 (15-50% glass fiber, conditioned)
Charpy impact strength, notched, 23°C	kJ m⁻²	4-9 (dry); 10-40 (conditioned); 12-15 (15-50% glass fiber, dry); 17-25 (15-50% glass fiber, conditioned)
Charpy impact strength, notched, −30°C	kJ m⁻²	3-6 (dry); 3-7 (conditioned); 5-12 (15-50% glass fiber, dry); 5-12 (15-50% glass fiber, conditioned)
Izod impact strength, notched, 23°C	J m⁻¹	4.5
Ball indention hardness at 358 N/30 S (ISO 2039-1)	MPa	135-145 (dry); 45-80 (conditioned); 160-180 (15-50% glass fiber, dry); 75-95 (15-50% glass fiber, conditioned)
Shrinkage	%	0.7-1.2 (parallel); 0.8-1.4 (normal); 0.1 (15-50% glass fiber, parallel); 0.3-0.7 (15-50% glass fiber, normal)
Viscosity number	ml g⁻¹	195
Melt volume flow rate (ISO 1133, procedure B), 275°C/5 kg	cm³/10 min	140
Water absorption, equilibrium in water at 23°C	%	5-10.5; 13.7 (saturated film); 5-8 (15-50% glass fiber)
Moisture absorption, equilibrium 23°C/50% RH	%	2-3.2; 1.1-3 (15-50% glass fiber)
CHEMICAL RESISTANCE
Acid dilute/concentrated	−	poor
Alcohols	−	good
Alkalis	−	good
Aliphatic hydrocarbons	−	good
Aromatic hydrocarbons	−	good
Greases & oils	−	good
FLAMMABILITY
Limiting oxygen index	% O₂	35
UL 94 rating	−	HB to V-0
TOXICITY
Carcinogenic effect	−	not listed by ACGIH, NIOSH, NTP
Skin rabbit, LD₅₀	mg kg⁻¹	moderate irritant
PROCESSING
Typical processing methods	−	blown film, cast film, injection molding
Preprocess drying: temperature/time/residual moisture	°C/h/%	80/2-4/0.15
Processing temperature	°C	240-285
Processing pressure	MPa	3.5-10.5 (injection and packing pressure)
Additives used in final products	−	flame retardant, nucleating agent
Applications		automotive (air intake systems, electrical, electronics, interior, lighting, powertrain and chassis), electrical appliances and equipment, cables & tubes, connectors, energy distribution, lighting, industry and consumer goods (housewares, mechanical engineering, power transmission, sports & leisure, tools & accessories), medical packaging
Outstanding properties	−	low friction, wear resistance
BLENDS
Suitable polymers	−	EVA, EVOH, PA6,10
ANALYSIS
x-ray diffraction peaks	degree	20.7, 22.9 (dry)	Men, Y; Rieger, J, Eur. Polym. J., 40, 2629-35, 2004.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781895198928500744

An introduction to lightweight composite materials and their use in transport structures

J. Fan , J. Njuguna , in Lightweight Composite Structures in Transport, 2016

1.3.2.2 Polyamides (nylon)

The two major types of polyamides are nylon 6 and nylon 66. ¹¹ Nylon 6, or polycaprolactam, is prepared by the polymerization of caprolactam. Poly(hexamethylene adipamide), or nylon 66, is derived from the condensation polymerization of hexamethylene diamine with adipic acid. Polyamides are crystalline polymers. Their key features include a high degree of solvent resistance, toughness, and fatigue resistance. Nylons do exhibit a tendency to creep under applied load. Glass fibers or mineral fillers are often used to enhance the properties of polyamides. In addition the properties of nylon are greatly affected by moisture.

The largest application of nylons is in fibers. Molded applications include automotive components, related machine parts (gears, cams, pulleys, rollers, boat propellers, etc.), appliance parts, and electrical insulation.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781782423256000013

Polycondensation

M. Zhang , ... T.E. Long , in Polymer Science: A Comprehensive Reference, 2012

5.02.2.3 Aliphatic versus Aromatic Polymers

The selection of appropriate monomers will inherently affect the thermal, mechanical, and morphological properties of the polymer through differences in intermolecular interactions. Aromatic monomers are generally more thermally stable than aliphatic monomers, and this translates into the stability of the final polymer. In fact, aromatic polyamides are considered high-performance polymers with thermal stability greater than 500 °C. The choice of aliphatic versus aromatic also largely affects polymer morphology. The aliphatic polyamide poly(hexamethylene adipamide) (nylon-6,6) is a semicrystalline polymer with a melting temperature of 265 °C and is approximately 50% crystalline. This high melting temperature contributes to the high tensile strength and modulus desired for fiber formation. The melting temperature of fully aromatic poly(p-phenylene terephthalate) (PPPT) is higher than the degradation temperature of the polymer.

Aromatic polyamides such as poly(m-phenylene isophthalamide) (PMPI) and PPPT have significantly different thermal and mechanical properties simply from altering the regioisomers ( Figure 3 ). Aromatic polyamides exhibit greater melting temperatures compared to aliphatic polyamides and therefore, require higher reaction temperatures. PPPT polymer chains have rodlike extended features through the highly regular para-substitutions and often form liquid crystalline solutions. ^3,9 Solutions of PPPT are directly spun into fibers with high polymer chain orientation to produce excellent moduli values. In fact, PPPTs, commonly known under the trade name Kevlar®, are used in bullet-proof vests. However, PMPI, which is meta-substituted, have meta-linked 'kinks' within the polymer chain to disrupt the linearity of the chain conformations and does not form rodlike polymer chains. Thus, the mechanical properties of this aramid diminish compared to PPPT. PMPI, commonly called Nomex®, is often used as fire-resistant protective clothing.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978044453349400131X

Nanostructured Polymer Blends for Gas/Vapor Barrier and Dielectric Applications

Emmanuel Rotimi Sadiku , ... S.M.R. Goddeti , in Design and Applications of Nanostructured Polymer Blends and Nanocomposite Systems, 2016

12.8.3 Polyamides

Polyamides (PA) are, arguably, the most studied and reported nanostructured polymer blends due to their affinity to the polar layered silicates, hence the ease of preparation. Literature regarding PA nanostructured polymer blends is abound; studies ranging from molecular dynamics to processing and application can be found. The two major types of polyamides are nylon 6 and nylon 66. Nylon 6, or polycaprolactam, is prepared by the polymerization of caprolactam. Poly(hexamethylene adipamide), or nylon 66, is derived from the condensation polymerization of hexamethylene diamine with adipic acid. Polyamides are crystalline polymers. Their key features include a high degree of solvent resistance, toughness, and fatigue resistance. Nylons do exhibit a tendency to creep under applied load. Glass fibers or mineral fillers are often used to enhance the properties of polyamides. In addition, the properties of nylon are greatly affected by moisture. The largest area of application for nylons is in fibers. Molded applications include automotive components, related machine parts (gears, cams, pulleys, rollers, boat propellers, etc.), appliance parts, and electrical insulation. Earlier studies have illustrated that the addition of clay to PA has improved the strength, stiffness, barrier, and heat resistance properties of nylon 6. The barrier resins exhibit reduced moisture absorption and increased melt stability.

Biopolymers originate from renewable resources such as plant oils and agro-industrial waste [34–36]. Compared to equivalent petroleum-based polymers, biopolymers often feature relatively poor mechanical, physical, and processing properties. These drawbacks plus higher costs make them less competitive and limit their use in most applications [37]. The addition of inorganic fillers can significantly contribute toward improving biopolymer properties, allowing them to be used in a variety of applications [46,49]. Dimer fatty acid-based polyamides are a special class of biopolymers derived from plant oils [50,51]. Compared to other polyamides, they feature lower water uptake and ease of processing (owing to a lower melt viscosity). Composites based on these materials have been characterized, and their properties have been studied using different approaches [52].

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B978032339408600011X

Polymer Characterization

Aubrey D. Jenkins , Kurt L. Loening , in Comprehensive Polymer Science and Supplements, 1989

7 Polymers made by polycondensation or related polymerization

The nomenclature system for copolymers is also applicable to polymers made by condensation polymerization of more than one monomeric species, or, more generally, by polymerization of more than one monomeric species where molecules of all sizes (i.e. monomers, oligomers, polymers) can react with each other. One can distinguish the case of polymers made by polycondensation of homopolymerizable monomers from that of polymers made by polycondensation of complementary ingredients that do not usually separately homopolymerize.

Rigorous application of the source-based definition of a copolymer ¹ embraces polymers such as poly(ethylene terephthalate) or poly(hexamethylene adipamide) (which are commonly regarded as homopolymers) because two ingredients are, in each case, the usual starting materials of polymerization. If polymers of this type have constitutionally regular structures and are regular polymers, the nomenclature for regular single-strand organic polymers can also be used. ² This applies, for example, to the polymer derived from terephthalic acid and ethylene glycol, which by source-based copolymer nomenclature would be named as poly(ethylene glycol-alt-terephthalic acid) if in fact the polymer has been prepared by a condensation polymerization starting with terephthalic acid and ethylene glycol. However, if the starting material is the partial ester HOCH₂CH₂OOCC₆H₄CO₂H, the appropriate source-based name is that of a homopolymer, whereas use of the starting material bis(hydroxyethyl) terephthalate, HOCH₂CH₂-OOCC₆H₄CO₂CH₂CH₂OH (extensively employed industrially), would suggest the name poly-[bis(hydroxyethyl) terephthalate]. Regardless of the starting materials used, the structure-based name is poly(oxyethyleneoxyterephthaloyl). The trivial name poly(ethylene terephthalate) is also permitted, because it is so well established in the literature.

For all such polymers made by condensation polymerization of two complementary difunctional ingredients (or 'monomers'), which can readily be visualized as reacting on a 1:1 basis to give an 'implicit monomer', the homopolymerization of which would give the actual product, the single-strand structure-based nomenclature may be suitable insofar as such a polymer is regular and can be represented as possessing a single constitutional repeating unit. It is to be noted that this is applicable only to cases where the mole ratio of the ingredients is 1:1 and the ingredients are exclusively difunctional.

The introduction of a third component into the reaction system necessitates the use of copolymer nomenclature which can logically be developed from the foregoing rules, as the examples below illustrate. The copolymer derived from reaction of ethylene glycol with a mixture of terephthalic and isophthalic acids would be named poly[(ethylene glycol-alt-terephthalic acid)-co-(ethylene glycol)-alt-isophthalic acid)], poly(ethylene terephthalate-co-ethylene isophthalate), or poly[(ethylene glycol)-alt-(terephthalic acid; isophthalic acid)].

A copolymer formed from oligo(adipic acid-alt-1,4-butanediol) and oligo(2,4-toluenediisocyanate-co-trimethylolpropane) in the presence of trimethylolpropane is named poly[oligo(adipic acid-alt-1,4-butanediol)-co-oligo(2,4-toluenediisocyanate-co-trimethylolpropane)-co-trimethylolpropane].

A polymer derived from the condensation polymerization of a single actual monomer, the molecules of which terminate in two different complementary functional groups (e.g. 6-amino-hexanoic acid) is, by definition, a (regular) homopolymer. When two different monomers of this type react together, the product is a copolymer that can be named in appropriate fashion. For example, if 6-aminohexanoic acid is copolycondensed with 7-aminoheptanoic acid, leading to a statistical distribution of monomeric units, the product is named poly[(6-aminohexanoic acid)-stat-(7-aminoheptanoic acid)].

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780080967011000021

Materials Characterization

D.S. BallantineJr., ... E.T. Zellers , in Acoustic Wave Sensors, 1997

4.2.2.3 Non-Fickian Diffusion

The Fickian diffusion described above is relatively easy to analyze, and demonstrates the capabilities of AW devices for monitoring transient uptakes. However, Fickian diffusion in polymers is the exception rather than the rule. A wide variety of transient responses have been observed, often due to the long time constants required for relaxation of the polymer chains upon absorption of species into the film [93],[95]. A detailed discussion of these trends is beyond the scope of this book, and the reader is referred to the polymer literature for these details [93],[95].

Brace et al. [92] investigated polymer/water interactions using SAW devices coated with either polyimide or cellulose acetate butyrate (CAB). In this study thermodynamic parameters were evaluated from the absorption isotherms, and transient responses to step changes in concentration were monitored. The transient responses observed were not consistent with Fickian diffusion, but could be described using a generalized relaxation equation containing two additive terms. Results under various conditions indicated that relaxation in the polymer system is much slower than diffusion of water.

Laatikainen and Lindström [100 ] used TSM devices to investigate absorption in cellulose acetate and poly-(hexamethylene adipamide). In addition to measuring absorption isotherms and partition coefficients, they reported on transient responses to changes in methanol concentration for a cellulose-acetate-coated TSM device ( Figure 4.10). At low concentrations, the linear response with √t is consistent with Fickian behavior, and diffusion coefficients can be evaluated (D= 4.8×10⁻¹⁰ and 1.6×10⁻⁹ cm²/sec for steps 1 and 2, respectively). It is seen that the initial diffusion rate increases with concentration in the polymer (based on the initial slope of the curves), until, at higher concentrations, a two-stage absorption transient occurs. This behavior, which is typical of glassy polymers, is due to the fact that diffusion begins to become faster than the polymer relaxations [95].

Recent work investigating gas sensor applications using TSM devices coated with the conductive polymer poly(pyrrole) revealed in some interesting diffusional properties. In one study on absorption of various alcohols [101], methanol was found to show Fickian behavior (D= 2.2×10⁻¹² cm²/s), while larger alcohols were found to have slower diffusion rates (D= 1.3×10⁻¹², 6.4×10⁻¹³, and 2.4×10⁻¹³ cm²/s for ethanol, n-propanol, and n-butanol, respectively) and trends indicative of non-Fickian diffusion. In another study that used a TSM device combined with measurements of film conductivity [102], the trends were consistent with Fickian diffusion except for the TSM frequency response, which demonstrated non-Fickian trends for methanol. These observations were interpreted as indicating that the conductivity changes to methanol were due solely to one stage of the two-stage sorption observed with the TSM. This may be due to the conductivity only probing the swelling of the polymer and not any subsequent sorption. In this study, the TSM measurements helped in determining the mechanism of conductivity changes in poly(pyrrole) films. In a final study investigating dichloromethane absorption from aqueous solutions [103] into poly(N-methylpyrrole) and poly(N-methylpyrrole/polystyrenesulfonate), the sorption rate was found to be independent of film thickness. This was interpreted as being due to rapid diffusion through pores in the polymer, followed by slow diffusion into the bulk of the polymer. The effect of oxidation state on sorption rates was also investigated.

The preceding results show that the ability of AW devices to follow the transient uptake of a species into a thin film allows these devices to be used to probe a wide variety of diffusional processes. As described for Fickian diffusion, a significant advantage of the AW technique is the ability to use thin films, which results in the rapid evaluation of the diffusional properties even in polymers that exhibit very slow transient uptake.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780120774609500046

Introductory Concepts and Definitions

Alfred Rudin , Phillip Choi , in The Elements of Polymer Science & Engineering (Third Edition), 2013

1.14.2.5 The Equivalent Random Chains [10]

The real polymer chain may be usefully approximated for some purposes by an equivalent freely oriented (random) chain. It is obviously possible to find a randomly oriented model which will have the same end-to-end distance as a real macromolecule with given molecular weight. In fact, there will be an infinite number of such equivalent chains. There is, however, only one equivalent random chain which will fit this requirement and the additional stipulation that the real and phantom chains also have the same contour length.

If both chains have the same end-to-end distance, then

(1-33) $⟨ d^{2} ⟩ = ⟨ d_{e}^{2} ⟩ = σ_{e} l_{e}^{2}$

where the unsubscripted term refers to the real chain and the subscript e designates the equivalent random chain. Here, l _e is usually referred to as Kuhn length. Also, if both have the same contour length D, then

(1-34) $D = D_{e} = σ_{e} l_{e}$

From Eqs. (1-33) and (1-34):

(1-35) $l_{e} = ⟨ d^{2} ⟩ / D$

and

(1-36) $σ_{e} = D^{2} / ⟨ d^{2} ⟩$

Search This Blog

Understanding Tall Nikol