Chemicals resistance

Chemical resistance is also one of the unique features of SPS. APS originally had good resistance to acids, alkalis and hydrolytic environments below Tg. SPS took over these chemical resistances from APS and acquired resistance to higher temperatures above Tg and, furthermore, resistance to organic solvents 

This chemical resistance along with the excellent electrical properties open up opportunities for GFSPS in electrical parts in automotive applications, such as connectors, electrical control unit (ECU), solenoids, and so on. 

The chemical resistance of latex-modified mortar and concrete is dependent on the nature of polymers added, polymer-cement ratio and the nature of the chemicals. Most latex-modified mortars and concretes are attacked by inorganic or organic acids and sulfates since they contain hydrated cement that is non-resistant to these chemical agents, but resist alkalis and various salts except the sulfates. Their chemical resistance is generally rated as good to fats and oils, but poor to organic solvents. 

Type of Concentration Type of Mortar Type of Mortar  

Chemicals (%) Un- SBR- EVA- PAE- PVDC- Un- SBR- EVA- PAE- PVDC-Modified Modified Modified Modified Modified Modified Modified Modified Modified Modified  

Modified Modified Modified Modified Modified Modified Modified Modified Modified Modified 

From the above data of the temperature dependence and thermal resistance of latex-modified mortars, the maximum temperature limit for retaining useful strength properties is found to be about 150°C. 

A wide range of solvents and chemicals is used when processing the different layers in the display and the effect of water and solvent absorption has a very detrimental effect on dimensional stability. This becomes increasingly important as processing moves toward roll to roll manufacture. 

An inorganic layer, 500 nm RT PECVD SiN, was used to passivate the plastic substrates, protect the substrates from the fabrication process, and help maintain substrate dimensional stability by minimizing solvent or moisture uptake. Given that the Young s modulus of this inorganic layer is much higher than that of the plastic film, even the thin film helps maintain substrate dimensional stability. 

For studying chemical resistance, the dried specimens of neat UPE and its polymer composites were immersed in 100 ml of 1 and 3 N solutions of NaOH and HCl for different time periods ranging from 10 to 30 days. After this, the samples were taken out and washed twice with distilled water, dried and weighed. The percent chemical resistance (P ) was calculated in terms of weight loss by the following relationship  

Where W. = initial weight and W. = weight after a certain interval It has been observed from Tables 13.2 13.3 that chemical resistance of neat UPE and its composites reinforced with raw, mercerized and benzoylated particle fibers towards acid and base decreases with increase in normality, as well as with increase in immersion time. This behavior could be due to the propagation of microcracks which cause more and more internal penetration of acids and bases into the composite samples and hence decreased chemical resistance behavior. Among raw, mercerized and benzoylated particle fibers-reinforced composites, the benzoylated one has been found to have better chemical resistance properties towards adds, which may be due to the better interfacial adhesion between treated fibers and matrix because of the enhanced hydrophobic character of benzoylated fibers. However, the lower chemical resistance behavior of benzoylated fibers-reinforced UPE composites towards NaOH could be 

Evaluation of chemical resistance may establish the potential for extraction of plasticizer incorporated in the material as well as an effect of plasticizer on durability of tested material. The standard contains information on testing chemical resistance with 50 test liquids using two methods immersion test and test under mechanical stress. The list of test liquids includes white oil which may be regarded as the only example of plasticizer among test liquids. Samples of known dimensions and weights are immersed in selected liquids for 168 h at room temperature. Containers are stirred every 24 h. Changes in appearance are recorded and samples can be subjected to mechanical property testing. Tensile properties of immersed samples are most frequently compared with control samples but other mechanical tests may also be used. 

Special strain jigs are used for testing samples under stress. Conditions of testing of samples with and without strain are the same. At the end of the testing process, the appearance of samples is evaluated and samples are subjected to mechanical property testing. Comparison is usually made between the samples tested with and without stress. 

Standard method describes determination of weight loss due to extraction by chemicals. The method is developed to determine changes in weight of materials immersed in 

When the SiH4/WF6 chemistry is used, the demands on the chemical compatibility of the adhesion layer are relaxed since this chemistry is so much milder than the hydrogen chemistry [Ellwanger et al.14]. In this way Al and Ti become acceptable adhesion layers. Unfortunately,the step coverage of the SiH4/WF6 chemistry is very poor (see section 2.3.2) and is therefore not suitable for contact fill applications. The silane reduction is, however, still applied to start the tungsten deposition especially atop of TiN (see 2.2.1) followed by the tungsten deposition based on the H2/WF6 chemistry. 

Generally speaking, higher temperatures can considerably impair resistance depending on the chemical environment. Up to 60 °C, PP is resistant to many solvents but aromatic and halogenated hydrocarbons, certain fats, oils and waxes cause swelling. At temperatures up to 30 °C, the effect is only slight. 

The higher the degree of crystallinity in a PP material, the greater its chemical resistance. Consequently, homopol5miers of PP have more chemical resistance than the random copolymer. 

In addition to moisture barrier properties, COCs exhibit good resistance to acid, alkalis and alcohols. Comparative chemical resistance properties are shown in Table 2.4. 

Important for medical applications, COC is considered as a high purity product with low amounts of low molecular weight extractable compounds. 

The failure of plastics in chemical environments may occur through dissolving, swelling, environmental stress cracking (ESC) or actual chemical attack. Dissolving, swelling or ESC can be predicted by consideration of the materials solubility parameters but there are always limitations to this approach. The chemical resistance of PAEK 

Materials suppliers produce extensive tables showing resistance to chemicals at various temperatures and stress levels. As etherketones, PARK have superb resistance to hydrolysis - in contrast to many polymers based on hydrolysable groups, such as esters, amides and imides. There are extensive data for important classes of environment. These include automotive fluids, oilfield environments, jet fuel, hydraulic fluids, refrigerants and materials used in semiconductor processing. However, these tables often provide little or no explanation of the underlying mechanisms. There are several important classes of chemical which will attack PARK. These include the following. 

High-temperature aromatics - At temperatures close to its melting point PEEK will dissolve in certain aromatic esters and ketones and materials such as benzophenone, diphenylsulfone and chloronaphthalene. Parachlorophenol dissolves PEEK at modest temperatures and solutions of chlorophenol/dichlorobenzene or phenol/trichlorobenzene have been used as solvents for gel permeation chromatography (GPC). PAEK will show some susceptibility to ESC in aromatic solvents at elevated temperatures and may even be slowly eroded by slight solubility effects. 

Amines - PAEK can be attacked by some amines - such as aniline at elevated temperatures. 

Solvents that can induce crystallisation - A large number of papers [10-16] report the solvent-induced crystallisation of amorphous PEEK. Most of these solvents operate by reducing of the PEEK to below ambient temperature which then allows crystallisation. They typically have an H-C-X fimctionality, where X is electron withdrawing. Examples include chloroform, methylene chloride, tetrahydrofuran and chlorotoluene. Such solvents tend to have an enhanced ability to cause ESC in crystalline PEEK. Solvent crystallisation is an interesting phenomenon but, so far, has limited industrial application. 

Many LCPs are virtually unaffected by most chemicals and solvents over a broad temperature range. Exposure to such aggressive chemicals as formic acid and sulphuric acid, and solvents such as methylene chloride, trichloroethane and Fluorinert FC-70 starting at room temperature and ranging, in some cases, up to 225 °C yields no significant changes in properties, dimensions or weight. Tables 7.9 and 7.10 illustrate representative chemical-resistance data. 

LCPs are also transparent to microwave energy, are virtually unaffected by radiation, and exhibit good hydrolytic stability and weathering resistance. 

6-NDA-based polyesters, the alcohol component has been varied. Ethylene glycol has been partially replaced by alcohols with aliphatic side chains, based on 1,3-propanediol (HH), such as 2,2-dimethyl-1,3-prop-anediol (CC), 2,2-diethyl-1,3-propanediol (C2C2) and 2-butyl-2-ethyl-1,3-propanediol (C2C4).  

Copolymers were prepared by the melt condensation method using dimethyl 2,6-naphthalate. The crystallinity and the density of annealed films decrease with increasing content of comonomer and length of alkyl side chain in the comonomer. The alkaline resistance is considerably increased by the incorporation of a comonomer having an alkyl side chain. 

All copolymers have a have higher solubility, higher glass transition 

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Key properties of alkyds are dimensional stability, colorability, and arc track resistance. Chemical resistance is generally poor. 

Tetralluoroethylene polymer has the lowest coefficient of friction of any solid. It has remarkable chemical resistance and a very low brittleness temperature ( — 100°C). Its dielectric constant and loss factor are low and stable across a broad temperature and frequency range. Its impact strength is high. 

It resembles polytetrafiuoroethylene and fiuorinated ethylene propylene in its chemical resistance, electrical properties, and coefficient of friction. Its strength, hardness, and wear resistance are about equal to the former plastic and superior to that of the latter at temperatures above 150°C. 

It possesses outstanding barrier properties to gases, especially water vapor. It is surpassed only by the fully fiuorinated polymers in chemical resistance. A few solvents dissolve it at temperatures... 

The principal monomer of nitrile resins is acrylonitrile (see Polyacrylonitrile ), which constitutes about 70% by weight of the polymer and provides the polymer with good gas barrier and chemical resistance properties. The remainder of the polymer is 20 to 30% methylacrylate (or styrene), with 0 to 10% butadiene to serve as an impact-modifying termonomer. 

Nylon 6 and 6/6 possess the maximum stiffness, strength, and heat resistance of all the types of nylon. Type 6/6 has a higher melt temperature, whereas type 6 has a higher impact resistance and better processibility. At a sacrifice in stiffness and heat resistance, the higher analogs of nylon are useful primarily for improved chemical resistance in certain environments (acids, bases, and zinc chloride solutions) and for lower moisture absorption. 

This thermoplastic shows good tensile strength, toughness, low water absorption, and good frictional properties, plus good chemical resistance and electrical properties. 

Its key properties are its excellent transparency, rigidity, and chemical resistance, plus its resistance to impact and to high temperatures. It withstands repeated autoclaving, even at 150°C. 

Polybutylene exhibits high tear, impact, and puncture resistance. It also has low creep, excellent chemical resistance, and abrasion resistance with coilability. 

The high degree of crystallization and the thermal stability of the bond between the benzene ring and sulfur are the two properties responsible for the polymer s high melting point, thermal stability, inherent flame retardance, and good chemical resistance. There are no known solvents of poIy(phenyIene sulfide) that can function below 205°C. 

Flexible foams are used in mattresses, cushions, and safety applications. Rigid and semiflexible foams are used in structural applications and to encapsulate sensitive components to protect them against shock, vibration, and moisture. Foam coatings are tough, hard, flexible, and chemically resistant. 

Polystyrene is rigid with excellent dimensional stability, has good chemical resistance to aqueous solutions, and is an extremely clear material. 

The isopropylidene linkage imparts chemical resistance, the ether linkage imparts temperature resistance, and the sulfone linkage imparts impact strength. The brittleness temperature of polysulfones is — 100°C. Polysulfones are clear, strong, nontoxic, and virtually unbreakable. They do not hydrolyze during autoclaving and are resistant to acids, bases, aqueous solutions, aliphatic hydrocarbons, and alcohols. 

PVC polymer plus special plasticizers are used to produce flexible tubing which has good chemical resistance. 

An extensive new Section 10 is devoted to polymers, rubbers, fats, oils, and waxes. A discussion of polymers and rubbers is followed by the formulas and key properties of plastic materials. Eor each member and type of the plastic families there is a tabulation of their physical, electrical, mechanical, and thermal properties and characteristics. A similar treatment is accorded the various types of rubber materials. Chemical resistance and gas permeability constants are also given for rubbers and plastics. The section concludes with various constants of fats, oils, and waxes. 

Blends of PET and HDPE have been suggested to exploit the availabiUty of these clean recycled polymers. The blends could combine the inherent chemical resistance of HDPE with the processiag characteristics of PET. Siace the two polymers are mutually immiscible, about 5% compatihilizer must be added to the molten mixture (41). The properties of polymer blends containing 80—90% PET/20—10% HDPE have been reported (42). Use of 5—15% compatbiLizer produces polymers more suitable for extmsion blow mol ding than pure PET. 

Bisphenol A. One mole of acetone condenses with two moles of phenol to form bisphenol A [80-05-07] which is used mainly in the production of polycarbonate and epoxy resins. Polycarbonates (qv) are high strength plastics used widely in automotive appHcations and appHances, multilayer containers, and housing appHcations. Epoxy resins (qv) are used in fiber-reinforced larninates, for encapsulating electronic components, and in advanced composites for aircraft—aerospace and automotive appHcations. Bisphenol A is also used for the production of corrosion- and chemical-resistant polyester resins, polysulfone resins, polyetherimide resins, and polyarylate resins. 

Nitrile mbber finds broad application in industry because of its excellent resistance to oil and chemicals, its good flexibility at low temperatures, high abrasion and heat resistance (up to 120°C), and good mechanical properties. Nitrile mbber consists of butadiene—acrylonitrile copolymers with an acrylonitrile content ranging from 15 to 45% (see Elastomers, SYNTHETIC, NITRILE RUBBER). In addition to the traditional applications of nitrile mbber for hoses, gaskets, seals, and oil well equipment, new applications have emerged with the development of nitrile mbber blends with poly(vinyl chloride) (PVC). These blends combine the chemical resistance and low temperature flexibility characteristics of nitrile mbber with the stability and ozone resistance of PVC. This has greatly expanded the use of nitrile mbber in outdoor applications for hoses, belts, and cable jackets, where ozone resistance is necessary. 

SAN resins possess many physical properties desked for thermoplastic appHcations. They are characteristically hard, rigid, and dimensionally stable with load bearing capabiHties. They are also transparent, have high heat distortion temperatures, possess exceUent gloss and chemical resistance, and adapt easily to conventional thermoplastic fabrication techniques (7). 

Acrylonitrile copolymeri2es readily with many electron-donor monomers other than styrene. Hundreds of acrylonitrile copolymers have been reported, and a comprehensive listing of reactivity ratios for acrylonitrile copolymeri2ations is readily available (34,102). Copolymeri2ation mitigates the undesirable properties of acrylonitrile homopolymer, such as poor thermal stabiUty and poor processabiUty. At the same time, desirable attributes such as rigidity, chemical resistance, and excellent barrier properties are iacorporated iato melt-processable resias. 

With sheet or pipe, multilayer coextmsion can be used. SoHd outer-soHd core coextmsion can place an ABS grade on the outside that has special attributes such as color, dullness, chemical resistance, static dissipation, or fire-retardancy over a core ABS that is less expensive or even regtind. 

The exceUent chemical resistance of acryhc fibers may stem from its unique lateraUy bonded stmcture. Dipole bonds, formed between nitrile groups... 

Chemical Properties. The hydrolysis of PET is acid- or base-catalyzed and is highly temperature dependent and relatively rapid at polymer melt temperatures. Treatment for several weeks in 70°C water results in no significant fiber strength loss. However, at 100°C, approximately 20% of the PET tenacity is lost in one week and about 60% is lost in three weeks (47). In general, the hydrolysis and chemical resistance of copolyester materials is less than that for PET and depends on both the type and amount of comonomer. 

Chemical Resistance. Table 2 shows the chemical resistance of PVA fiber (40). The fiber exhibits markedly high resistance to organic solvents, oils, salts, and alkaU. In particular, the fiber has unique resistance to alkaU, and is hence widely used in the form of a paper principally comprising it and as reinforcing material for cement as a replacement of asbestos. 

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