Abstract: The present invention is directed to an epoxy-containing polymeric material having nonlinear optical properties, particularly a glycidyl amine polymer, and a process for making the nonlinear optical (NLO) epoxy-containing polymeric material including poling the polymeric material under high voltage at elevated temperature for a period of time to bring about orientation of the nonlinear optical functionalities in the polymer. The polymers have enhanced thermal stability and good NLO properties.

Abstract: Azole rings, such as oxazole and thiazole rings, can activate an aromatic ring bonded to a leaving group such as a halogen atom so that the aromatic ring will undergo aromatic nucleophilic substitution. The reaction is useful for making ethers, thioethers and amines containing azole rings. In particular, monomers having azole rings, activated aromatic rings with leaving groups and nucleophilic moieties can react under conditions of aromatic nucleophilic displacement to form non-rigid rod PBZ polymers. The non-rigid rod PBZ polymers can be used to form molecular composites with rigid rod PBZ polymers which molecular composites are not substantially phase separated.

Abstract: An epoxy resin comprising an active hydrogen compound having at least three active hydrogen atoms capable of reacting with an epoxy group in its molecule or butadine or isoprene as a main monomer is modified with an oligomer having on average at least 1.5 equivalents of active hydrogen capable of reacting with an epoxy group in its molecule. An epoxy resin modified with a bisphenol and a compound having active hydrogen or acid anhydride groups capable of reacting with an epoxy group is also provided. A toner containing the epoxy resin as a binder is useful in electrostatography.

Abstract: The instant invention involves a process for producing continuous polybenzimidazole films. The process is comprised of the following steps:(a) preparing a solvent solution of a polybenzimidazole polymer;(b) continuously casting the solution upon a support;(c) evaporating a sufficient amount of the solvent to form a self-supporting film in an oven;(d) washing the film in a nonsolvent;(e) removing the film from the support; and(f) continuously collecting the continuous film.

Abstract: A bioelastomer containing repeating units comprising elastomeric tetrapeptide or pentapeptide units or a mixture thereof, wherein said repeating units comprise amino acid residues selected from the group consisting of hydrophobic amino acid residues and glycine residues, wherein said repeating units exist in a .beta.-turn which comprises a polypentapeptide unit of the formula:--.alpha.P.rho..OMEGA.G--.sub.nwherein P is a peptide-forming residue of L-proline; G is a peptide-forming residue of glycine; .alpha. is a peptide-forming residue of L-valine or an ionizable peptide-forming residue selected from the group consisting of residues of L-Glu, L-Asp, L-His, L-Lys and L-Tyr; .rho. is a peptide-forming residue of glycine or a peptide-forming residue of D-Glu, D-Asp, D-His, D-Lys and D-Tyr; and .OMEGA.

Abstract: A cross-linked resin as obtained by the reaction of a bis (2-oxazoline) compound with an aromatic compound having at least two amino groups shows low water-absorption, excellent in strength, and, in addition, tough and superior in heat-resistance.The resin composition comprising the cross-linked resin and reinforcements and/or fillers can be especially advantageously utilized for preparing a variety of molded articles practically usable in a broad application field, for example, space, aircraft, railway vehicles, automobiles, civil engineering, electrical and electronic appliances, cross-resistant equipment, sports and leisure equipment, medical equipment and industrial parts, as well as in the new application areas where conventional fiber-reinforced resins have hardly been utilized by the reason of insufficient strength, water-absorption, heat-resistance, etc.

Abstract: Polyamides in which amino acids are incorporated in the polymer backbone via two amino or carboxyl groups and which carry in the .alpha.-position to the amide structure a functional group which is responsible for degradation and active compound release are highly suitable for the preparation of biologically degradable active compound depot preparations having controlled release of the active compound.

Abstract: The thermoplastic aromatic polyamideimide compolymers comprising the structural units (1), (2) and (3) represented by formulae, ##STR1## respectively, (2) and (3) being at ratio of 1 mole to 1 mole of (1), (3) being at a ratio of 0.95-0.05 mole to 0.05-0.95 mole of (2), (1) and (2) or (3) being alternatively interconnected and Ar and Ar' being composed of 5 to 70 mole % of ##STR2## and 95 to 30 mole % of ##STR3## provide the moldings being superior in heat stability and fluidity at the temperatures of 300.degree. to 400.degree. C. and injection moldable and having desired characteristics.

Abstract: A novel class of heterocyclic polymers and copolymers containing the 2-imidazolin-5-one ring structure is described. These polymers are prepared by reaction of bisazlactones and diamines, with or without suitable condensation monomers; the resultant polyamides are then thermally cyclodehydrated in the presence of a catalyst to produce the imidazolinone-containing polymers. Many of the poly(imidazolinones) are water soluble and therefore find utility in various aspects of water treatment, or in paper or fabric sizing.

Abstract: Novel liquid crystalline extended chain polymer compositions comprising a high concentration of one or more extended chain homopolymer(s), copolymer(s), or block polymer(s) and certain strong acids are prepared by admixing a high concentration of one or more selected homo- or hetero-bifunctional monomer(s) with or without oxidation protecting atoms or groups and one or more of a substantially non-oxidizing strong acid(s) having a high or low P.sub.2 O.sub.5 content. Such compositions are capable of exhibiting excellent cohesive strength, and are especially suited to the production of high molecular weight ordered polymer fibers by dry-jet wet spinning. These liquid crystalline compositions are capable of being drawn through long air gap distances and spun at exceptionally high spin draw ratios. Fibers, films and other articles formed from these liquid crystalline compositions exhibit exceptionally high physical and heat resistant properties.

Abstract: A pigment dispersant is derived from a compound of molecular weight less than 600 which contains at least three functional groups, at least one of which is an epoxy group. Preferably the compound contains at least three epoxy groups, for example triglycidyl isocyanurate. The core radical derived from the said compound is bonded to more than one solvent-compatible organic radical of molecular weight at least 200, the average molecular weight of the solvent-compatible radicals being at least 500, and to a pigment-compatible radical containing a polar group.

Abstract: Novel compositions comprising a high concentration of one or more extended chain homopolymer, copolymer, or block polymer and certain polyphosphoric acids are prepared under conditions to exercise control of molecular weight as characterized by intrinsic visoscity. Such compositions are optically anisotropic (liquid crystlaline), capable of exhibiting excellent cohesive strength, and are especially suited to the production of high molecular weight ordered polymer fibers by dry-jet wet spinning. These liquid crystalline compositions are capable of being drawn through long air gap distances and spun at excptionally high spin draw ratios. Fibers, films and other articles formed from these liquid crystalline compositions exhibit exceptionally high physical and heat resistant properties.

Abstract: Solventless polymeric compositions suitable for coatings and moldings are formed by the addition reaction product of a first component comprising mono, di or polyamines, or an adduct of mono, di or polyamines with mono, di or polyfunctional acrylates and/or epoxides and a second component comprising mono, di or polyacrylates or mixtures with mono, di or polyepoxides.

Abstract: A novel class of heterocyclic polymers and copolymers containing the 2-imidazolin-5-one ring structure is described. These polymers are prepared by reaction of bisazlactones and diamines, with or without suitable condensation monomers; the resultant polyamides are then thermally cyclodehydrated in the presence of a catalyst to produce the imidazolinone-containing polymers. Many of the poly(imidazolinones) are water soluble and therefore find utility in various aspects of water treatment, or in paper or fabric sizing.

Abstract: A C.sub.21 amino acid is disclosed as a useful reactant for preparing polyamide resins.

Abstract: Imide-linked bisphthalonitrile compounds are prepared by combining a dicyano aromatic diamine and an organic dianhydride to produce an amic acid linked bisphthalonitrile copound. The amic acid linked bisphthalonitrile compound is dehydrocyclized to produce the imide-linked bisphthalonitrile compounds. The imide-linked bisphthalonitrile compounds may be polymerized to produce a phthalocyanine polymer by heating the imide-linked bisphthalonitrile compound, either alone or in the presence of a metal powder or a metal salt. These compounds are useful in the coating, laminating and molding arts. The polymers are useful in composite matrix resins where increased fire resistance, toughness and resistance to moisture are required, particularly as secondary structures in aircraft and spacecraft.

Abstract: Aromatic polyimide compositions, precursors of copolyphthalocyanine-imides, heir manufacturing process and the resultant copolyphthalocyanine-imides, are described.These compositions may result for the reaction of 80.degree.-300.degree. C. of an aromatic tetra acid, diester-diacid, tetraester or dianhydride compound of formula: ##STR1## with an aromatic amino-dinitrile ##STR2## and optionally an aromatic diamine NH.sub.2 --Ar--NH.sub.2. A subsequent heating at 200.degree.-300.degree. C. provides, by cross-linking, copolyphthalocyanine-imides, which are hardened resins, stable at 250.degree.-300.degree. C. in continuous use.

Abstract: This invention provides 2-aminobenzothiazole-6-carbonyl chloride hydrochloride, which can be condensed under polymerization conditions to form a novel benzothiazole-polyamide polymer consisting of a recurring monomeric unit corresponding to the formula: ##STR1##

Abstract: Polypyromellitimide filaments having high strength and high modulus are obtained by dry-spinning a solution of polyamide-acid of polypyromellitic dianhydride, 3,4'-oxydianiline and paraphenylenediamine, substituted derivatives thereof or 4,4'-diaminobiphenyl or 4,4'-diaminobenzanilide, then converting the polyamide-acid to the polyimide and drawing.

Abstract: This invention provides 2-aminobenzothiazole-6-carbonyl chloride hydrochloride, which can be condensed under polymerization conditions to form a novel benzothiazole-polyamide polymer consisting of a recurring monomeric unit corresponding to the formula: ##STR1##

Abstract: This invention is directed to acid terminated azomethines formed by reacting aromatic dialdehydes or aromatic diketones with amino-carboxylic acid compounds. These oligomers may be reacted with epoxy resins to produce polymer material having high glass transition temperatures.

Abstract: A one-step process for the preparation of poly[3,6-N-substituted carbazole-1,3,4-oxadiazole-2,5-diyl] which comprises polymerizing N-substituted carbazole-3,6-dicarboxylic acid, wherein the carbazole nitrogen is substituted with lower alkyl of 1 to 6 carbon atoms or phenyl, with a 0 to 30% molar excess of hydrazine or a hydrazine salt of a non-oxidizing acid in the presence of polyphosphoric acid.

Abstract: A novel class of polymeric compounds containing piperidine radicals of the formula ##STR1## in which X is a divalent radical selected from the group comprising ##STR2## is described. The novel compounds are light stabilizers, heat stabilizers and oxidation stabilizers for synthetic polymers and are particularly effective in polyolefine films, fibres and tapes.

Abstract: Polymers of a polyfunctional epoxy compound, N,N,N',N'-tetraglycidyl-1,3-propylene bis(p-aminobenzoate), formed by reaction of such epoxy compound with aromatic polyamines. The disclosed polymers are useful as structural resins, e.g., as advanced composite matrix resins.

Abstract: Process for producing cationic epoxy resins carrying oxazolidine groups suitable as paint binders, and particularly paint binders for the formulation of cathodically depositable paints, wherein the epoxy resin is reacted with a hydroxy functional oxazolidine compound or with an oxazolidine compound carrying in the ring the structure ##STR1## in the presence of a monocarboxy compound. The presence of the monocarboxy compound permits the direct reaction or linkage of the epoxy resin with the oxazolidine compound without gelation; and, additionally, the monocarboxy compound favorably influences the film-forming characteristics of the binders.

Abstract: Solventless polymeric compositions suitable for coatings and moldings are formed by the addition reaction product of a first component comprising mono, di or polyamines, or an adduct of mono, di or polyamines with mono, di or polyfunctional acrylates and/or epoxides and a second component comprising mono, di or polyacrylates or mixtures with mono, di or polyepoxides.

Abstract: The invention includes novel dicarboxylic acids derived from alkylene or arylene diaminetetraacetec acid corresponding to the formula ##STR1## These dicarboxylic acids derived from alkylene or arylene diaminetetraacetic acid are useful in the preparation of polyamides.Another aspect of the invention is a polymer prepared from between about 1 and 100 mole percent of the diamine salt of the compound represented by formula (I) ##STR2## These polymers are useful in preparing molded articles.

Abstract: Novel compositions comprising a high concentration of one or more extended chain homopolymer, copolymer, or block polymer and certain polyphosphoric acids are prepared. Such compositions are optically anisotropic (liquid crystalline), capable of exhibiting excellent cohesive strength, and are especially suited to the production of high molecular weight ordered polymer fibers by dry-jet wet spinning. These liquid crystalline compositions are capable of being drawn through long air gap distances and spun at exceptionally high spin draw ratios. Fibers, films and other articles formed from these liquid crystalline compositions exhibit exceptionally high physical and heat resistant properties.

Abstract: Hydrazides of the formula (I) or (II)N--CH.sub.2 CH.sub.2 CONHNH.sub.2).sub.3 (I)(NH.sub.2 NHCOCH.sub.2 CH.sub.2).sub.2 N--R--N--CH.sub.2 CH.sub.2 CONHNH.sub.2).sub.2 (II)are good latent curing agents for epoxy resin, in the formula (II) R is divalent hydrocarbon residue having 2-24 carbon atoms. The curing agents are useful in formulating novel storable one-package, heat-curable epoxy resin-based compositions.

Abstract: A selective permeable membrane comprising a polyquinazolone-based polymer including a repeating unit represented by the formula ##STR1## wherein R.sup.1 is a tetravalent aromatic group, R.sup.2a and R.sup.2b are each independently, an alkyl group or aromatic group, and R.sup.3 is a divalent organic group.

Abstract: Poly(imide)-containing polymers suitable for use in molding or casting applications are formed by polymerization of an anhydride-containing precursor of the formula ##STR1## wherein Y is a divalent hydrocarbon group or a divalent hydrocarbon group containing oxygen, sulfur, nitrogen, silicon, phosphorus or halogen atoms;R is phenyl or C.sub.1-10 alkyl; andX is an oligomer or polymer-forming reactive moiety with reactive nitrogen-containing polyfunctional comonomers.

Abstract: Polyesteramides can be prepared by copolymerizing a cyclic lactone with at least one of an ammonium salt of an alpha, beta unsaturated monocarboxylic acid, an alpha, beta unsaturated nitrile and water and beta-aminopropionic acids and their alkyl derivatives. Polymers with especially good physical properties were prepared by polymerizing caprolactone with one or more ammonium methacrylate, ammonium acrylate, acrylonitrile and beta-alanine. These polymers are useful as molding plastics.

Abstract: Metal 4, 4', 4", 4"'-tetracarboxylic phthalocyanines (MPTC) are prepared by reaction of trimellitic anhydride, a salt or hydroxide of the desired metal (or the metal in powdered form), urea and a catalyst. A purer form of MPTC is prepared than heretofore. These tetracarboxylic acids are then polymerized by heat to sheet polymers which have superior heat and oxidation resistance. The metal is preferably a divalent metal having an atomic radius close to 1.35.ANG..

Abstract: A polyfunctional epoxy compound, N,N,N',N'-tetraglycidyl-1,3-propylene bis(p-aminobenzoate) is disclosed useful as an epoxide resin. Also disclosed are polymers of such compound formed by reaction with aromatic polyamines which are useful as structural resins, e.g., as advanced composite matrix resins.

Abstract: The invention relates to metal, primarily divalent metal such as divalent copper, cobalt and nickel, 4,4',4", 4'" phthalocyanine tetracarboxylic acids and to polymers prepared by heating the same, and to a method of preparing the tetracarboxylic acids.A method is provided for preparing the aforesaid tetracarboxylic acids in purer form than heretofore. Upon heating these acids decarboxylate and produce polymers.These polymers have diphenyl (conjugated) types of linkage; they are thermally and oxidatively stable and useful as sheet polymers for various purposes such as heat shielding.The monomeric tetracarboxylic acid is shown in FIG. 1, the polymer in FIG. 2 and thermal resistance in FIG. 3.The monomeric tetracarboxylic acids are prepared in purer form than heretofore, the resulting polymers are more stable thermally and oxidatively than metal phthalocyanine polymers and monomers heretofore made.

Abstract: An improved method of preparing polyamide acid for processing of semiconductors from a diamine and a tetracarboxylic acid dianhydride optionally with a diaminocarbonamide, is provided (1) by reacting the components at below 40.degree. C. until the reduced viscosity reaches above 0.5 dl/g. at 30.degree. C. and then, (2) by adjusting the reduced viscosity to more than 0.3 dl/g, at 30.degree. C. and the solution viscosity to 500-3,000 cps at 25.degree. C. by heating at 50-100.degree. C. By applying the polyamide acid obtained by the method to semiconductor apparatus, they get sufficient heat-resistance without pin holes, and their reliability may be greatly improved.

Abstract: A process for producing an anionic copolymer containing urethane and carboxylic acid ester moieties with or without carbonate moieties, carbonamide moieties, or both carbonate and carbonamide moieties, having weight average molecular weights from 1,000 to 150,000, determined by light diffusion method, which comprises heating an anhydrous mixture of 20 to 80% by weight of lactam and 80 to 20% by weight of a cyclic carbonate at temperatures between 100.degree. and 250.degree. C. in the presence of 0.001 to 1% by weight, based on the quantity of monomers, of an alkaline catalyst and copolymers produced thereby which are useful as adhesives, plasticizers and lacquers.

Abstract: Novel amorphous copolyamides are provided which are the product of reaction of (A) a lactam, (B) a bisimidazoline, and (C) a dicarboxylic acid, wherein the proportions of reactants based on 100 mole percent are from about 43 to about 82 mole percent of lactam (A) and the remaining 18 to 57 mole percent divided between said (B) and said (C) in substantially equimolar proportions.The copolyamides are characterized by better resistance to elevated temperatures than 100 percent polycaprolactam polyamides but at the same time are easily molded because of their amorphous character.

Abstract: Extremely rapid ambient curing of polyepoxide resins and mixtures of polyepoxide resins and polyacrylate esters is achieved by use of a curing system composed of at least one polymercaptan and at least one catalytic co-curing agent which is the condensation product of:(a) aliphatic amine or substituted aliphatic amine containing at least one primary aliphatic amine group where the aliphatic moiety is ethylene or greater with(b) at least one amino acid, its corresponding lactam or other amide forming derivative.Optionally, known Lewis Base catalysts for the epoxy/mercaptan reaction, such as tertiary amines, may also be used.

Abstract: Anionic copolymers of lactams and aliphatic polycarbonates having urethane and carboxylic acid ester groups, preferably having recurring structural units of the formula:--NH--CO--O--Y--O--CO--(CR.sub.2).sub.n --whereinR represents hydrogen or C.sub.1 -C.sub.4 -alkyl;n represents an integer of from 2 to 13;Y represents the residue of an alcohol of the following formula:HO--X--OH,whereinX represents an open-chain, cyclic or mixed open-chain-cyclic alkylene radical having from 2 to 12 carbon atoms which is optionally substituted by C.sub.1 -C.sub.4 -alkyl and optionally interrupted by from 1 to 3 oxygen atoms, or a polyethylene glycol having a molecular weight up to 10,000 or an alkoxylation product of bifunctional phenols.

Abstract: A process for preparing a cathodic electrodepositable coating composition which comprises, in sequence,(i) epoxidizing a high-molecular-weight compound containing a carbon-carbon double bond and having a molecular weight of 500 to 10,000 and an iodine value of 100 to 500 to form an epoxidized high-molecular-weight compound containing 0.5 to 12% by weight of oxirane oxygen,(ii) reacting a part of the epoxy groups of the epoxidized high-molecular-weight compound with a basic amine compound of the general formula ##STR1## wherein R.sub.1 and R.sub.2, independently from each other, represent a hydrocarbon group having 1 to 10 carbon atoms which may be partly replaced by a hydroxyl group, and R.sub.1 and R.sub.2 together may form a cyclic structure,(iii) reacting a part or the whole of the remaining epoxy groups with an .alpha.,.beta.-unsaturated monocarboxylic acid of the general formula ##STR2## wherein R.sub.3 and R.sub.

Abstract: A composition comprising a varnish of heat-resistant resin having active hydrogen in the molecule and a bismaleimide compound or derivative thereof admixed with the varnish affords a heat-resistant resin product of improved properties. Especially when a bismaleimide compound or derivative thereof is added to a varnish of polyimide resin having active hydrogen in the molecule and the composition is applied to a metal film substrate to form a resin film, the film has improved peel strength and, in itself, also has improved strength and elongation.

Abstract: A new type of poly-2-pyrrolidone suitable for melt spinning and a process for its preparation. The new poly-2-pyrrolidone is characterized in that the polymer in the virgin state has a relative viscosity (1 gram of polymer in 100 ml of 96% sulphuric acid at 20.degree. C.) of between 2.2 and 7.0, shows a weight loss of less than 5% by weight when heated from 20.degree. C. to the onset temperature of thermal degradation at a rate 4.degree. C. per minute, the ratio between the relative viscosities after and before melt spinning ranges between 0.50:1 and 0.95:1, and the relative viscosity after melt spinning is at least 1.90. The new poly-2-pyrrolidone is prepared by polymerization of 2-pyrrolidone in the presence of an anionic catalyst and an accelerator wherein N-(2-caprolactim)-caprolactam is used as the accelerator in an amount of between 0.05 and 5.0 mole percent relative to the monomer, and the polymerization is carried out at a temperature of between about 25.degree. and 70.degree. C.

Abstract: A process for the production of polyquinazolone-based polymers by reacting bisquinazolone with a diamine or a diamine substituted with a carboxylic acid, sulfonic acid or metal salt thereof in the presence of a Lewis acid catalyst or a phosphorus-containing dehydrating agent, where the polymers are useful to produce permselective membranes.

Abstract: Non-crosslinking, water-soluble polyamines which can be obtained by reacting(A) basic polyureas which have been prepared by condensation of ureas with polyamines containing at least three amino groups, of which at least one is a tertiary amino group, or with mixtures of these polyamines with aliphatic, araliphatic, cycloaliphatic or heterocyclic polyamines containing two primary or two secondary amino groups or one primary or one secondary amino group, and optionally with .omega.-aminocarboxylic acids containing at least three carbon atoms, or lactams thereof,(B) polyalkylenepolyamines of the general formula ##STR1## in which R denotes H or CH.sub.

Abstract: Novel polyketene-aminal polyamides are disclosed which have the following recurring unit ##STR1## wherein R is a divalent hydrocarbon radical, R.sub.1, R.sub.2, R.sub.3, and R.sub.4 when taken separately are independently selected from the group consisting of lower alkyl, aralkyl, and cycloalkyl, and when taken together as R.sub.1 with R.sub.2 and R.sub.3 with R.sub.4 with the respective nitrogen atoms to which they are attached represent independently a heterocyclic group having from 5 to 7 ring atoms.The polyamides are prepared by reacting together the appropriate diisocyanate [R(NCO).sub.2 ] and appropriate ketene-aminal to form the polymer directly without the evolution of any by-products or volatiles.The novel polymers are thermoplastic and can be formed or shaped using any of the techniques known to those skilled in the thermoplastic polymer art.

Abstract: A process for the elimination of the fluorescence effect resulting from the treatment of fibrous materials with optical anionic agents is described which consists of treating the fibrous materials with a water soluble salt of a polymer containing the imidazoline ring of formula I ##STR1## wherein X is in the position meta or para with respect to the imidazoline ring and X is ##STR2## or --CO--NH-- The imidazoline-containing compounds prepared by reacting diethylenetriamine or triethylenetetramine with terephthalic or isophthalic acid followed by cyclization are reacted with dicyandiamide. The water soluble salt is an acid addition salt or a quaternary ammonium salt. The new polymers are described.

Abstract: There is described photosensitive polymer composition and a polyimide film-coated material made by applying the composition to a support, irradiating with ultraviolet and thereafter heating. The photosensitive polymer composition is prepared by adding a sensitizer to a photosensitive polyamide acid intermediate solution which is obtained by reacting in an inert solvent a first compound comprising 100 to 5% by weight of a photosensitive group-containing diamine and 0 to 95% by weight of a diamine having no photosensitive group, with a second compound comprising at least one compound selected from a tetracarboxylic acid dianhydride and a tricarboxylic acid anhydride monohalide.

Abstract: Novel addition polymers of dimorpholone compounds and diamines, which contain structural units of the general formula ##STR1## where X and Y may be various conventional organic radicals, are obtained by reacting dimorpholone compounds with diamines. The polymers may be used for modifying plastics, and for textile or paper finishing.

Abstract: Heat-curable mixtures of one or more epoxide compounds, which, on average, have more than one epoxide group in the molecule, and one or more .beta.-aminocrotonic acid derivatives, such as .beta.-aminocrotononitrile, .beta.-aminocrotonamide or .beta.-aminocrotonic acid esters, and also, if desired, a polyamine or polycarboxylic acid anhydride or a maleimide. The novel curable mixtures are distinguished by outstanding stability on storage, can be processed easily and give moulded materials with good mechanical properties.