Tensile and tearing strengths

Combination Flame Retardant—Durable Press Performance. Systems using THPC, urea, and TMM can be formulated to give fabrics which combine both flame-retardant performance and increased wrinkle recovery values (80). Another system employs dimethylol cyanoguanidine with THPC under acidic conditions (115). Both of these systems lead to substantial losses in fabric tensile and tearing strength. 

Conventional cure systems use relatively high levels (2.5 + phr) of sulfur combkied with lower levels of accelerator(s). These typically provide high initial physical properties, tensile and tear strengths, and good initial fatigue life, but with a greater tendency to lose these properties after heat aging. 

Polymers can be modified by the introduction of ionic groups [I]. The ionic polymers, also called ionomers, offer great potential in a variety of applications. Ionic rubbers are mostly prepared by metal ion neutralization of acid functionalized rubbers, such as carboxylated styrene-butadiene rubber, carboxylated polybutadiene rubber, and carboxylated nitrile rubber 12-5]. Ionic rubbers under ambient conditions show moderate to high tensile and tear strength and high elongation. The ionic crosslinks are thermolabile and, thus, the materials can be processed just as thermoplastics are processed [6]. 

Elastomeric composition for dynamic application of cross-linked E-plastomers has been made with filer-reinforced systems which contain a metal salt (typically zinc) of an alpha, beta unsaturated acid. These additives improve the tensile and tear strength of the elastomer and are cured with a peroxide cure system. These cross-linked articles are suitable for dynamic loading applications such as belting, including power transmission and flat belting. 

The carboxylated types (XNBR) contain one, or more, acrylic type of acid as a terpolymer, the resultant chain being similar to nitrile except for the presence of carboxyl groups which occur about every 100 to 200 carbon atoms. This modification gives the polymer vastly improved abrasion resistance, higher hardness, higher tensile and tear strength, better low temperature brittleness, and better retention of physical properties after hot-oil and air ageing when compared to ordinary nitrile rubber. 

PVC/NBR polymer blends can be produced as colloidal or mechanical blends, the former generally giving superior properties. Commercially available blends have PVC contents ranging from 30-55%. The blends have reduced elasticity, which gives improved extrudability, but they also exhibit superior ozone resistance, improved oil swell resistance, and tensile and tear strength this, however, is achieved at the expense of low temperature flexibility and compression set. The ozone resistance of such blends is, however, only improved if the PVC is adequately distributed and fluxed. This is harder to achieve in mechanical blends, but if it is not achieved failure due to ozone attack can occur. 

The polyurethane formulation Involved a proprietary crossllnkable system based on poly(propylene glycol) and methylene dllsocyanate (NCO/OH ratio = 1.0). For studies of viscoelastic, energy absorption, and fatigue behavior, the weight fractions of PUMA were 0, 0.25, 0.50, 0.75, and 1.0 for studies of tensile and tear strength, the ratios were 0, 0.10, 0.20, 0.25, 0.30, and 0.40. Reactants were mixed at room temperature, degassed, poured Into a mold, and cured at 60 C for 48 hr. 

Tensile and tear strengths were determined using ASTM standards D412 and D1004, respectively, at a crosshead speed of 0.42 mm/s (1 In/mln) values reported are the average for 3 specimens. The elastic and Inelastic (plastic) components of the total elongation... 

Tensile and Tearing Behavior. As shown in Figure 4, the tensile and tear strengths increased with increasing PMMA content measurements of tear strength were not feasible at PMMA contents > 30%. In any case, the incorporation of PMMA at even relatively low levels greatly improves the rather low strengths of the unmodified PU. 

Figure 4. Tensile and tear strength of FU/FMMA SlNs as a function of composition.

Regardless of the method of cross-linking, mechanical properties of a cross-linked elastomer depend on cross-link density. Modulus and hardness increase monotonically with cross-link density, and at the same time, the network becomes more elastic. Fracture properties, i.e., tensile and tear strength, pass through a maximum as the cross-link density increases (see Figure 5.4). 

Soft segments One of the two phases which make up polyurethane. The soft segment is composed of long-chain polyether or polyester polyols. The soft segment controls many of the polyurethane properties such as tensile and tear strength, hydrolysis and chemical resistance, glass transition temperature, and flexibility. 

One of the most industrially important characteristics of papers is their chemical stability, which enables them to withstand degradation with its consequential loss of tensile and tear strength and fold endurance under normal conditions of use. However, this stability is not absolute. Cellulose is susceptible to oxidation and the glycosidic linkage is susceptible to hydrolysis. In order to protect book papers from acid degradation, they must not be exposed to acid. Acids are generated from the alum-rosin size as well as from such... 

These plastics are quite inert thus, compatibility with other substrates does not pose major problems. The terephthalates have high tensile and tear strengths, excellent chemical resistance, good electrical properties, and an operating temperature range from —55 to 200°C. These materials are generally joined with adhesives, and surface treatments are used to enhance adhesion, if required. 

Physical properties are related to ester-segment structure and concentration in thermoplastic polyether-ester elastomers prepared hy melt transesterification of poly(tetra-methylene ether) glycol with various diols and aromatic diesters. Diols used were 1,4-benzenedimethanol, 1,4-cyclo-hexanedimethanol, and the linear, aliphatic a,m-diols from ethylene glycol to 1,10-decane-diol. Esters used were terephthalate, isophthalate, 4,4 -biphenyldicarboxylate, 2,6-naphthalenedicarboxylate, and m-terphenyl-4,4"-dicarboxyl-ate. Ester-segment structure was found to affect many copolymer properties including ease of synthesis, molecular weight obtained, crystallization rate, elastic recovery, and tensile and tear strengths. 

The structure of the diol in alkylene terephthalate/PTME terephthalate copolymers has an important effect on the properties of these block copolymers, as evident from the results shown in Tables II, III, and IV. The 50% tetramethylene terephthalate/PTME terephthalate copolymer prepared from 1,4-butanediol (4G) which was previously noted in Table I serves as our reference copolymer for purposes of discussing the effects of changing the structure of the crystallizable ester segments. The outstanding properties of the 4G-based copolymer are ease of synthesis, a rapid rate of crystallization from the melt, a high melting point, and excellent tensile and tear strengths. 

Ethylene Terephthalate/PTME Terephtalate Copolymer. The ethylene glycol- or 2G-based copolymer (Table II) closely resembles the 4G-based copolymer in having a high melting point, even higher than the 4G copolymer, and excellent tensile and tear strengths. The 2G-based copolymer suffers from having a rather slow rate of crystallization (8,12). Poly (ethylene terephthalate) homopolymer suffers from similar... 

Alkylene w-Terphenyl-4,4f -dicarboxylate/PTME w-Terphenyl-4,4"-dicarboxylate Copolymers. Polyether-ester copolymers with the composition 50% alkylene rn-terphenyl-4,4"-dicarboxylate/PTME rn-ter-phenyl-4,4"-dicarboxylate were prepared using as diols 1,3-propanediol (3G) and 1,4-butanediol (4G). Both copolymers exhibit excellent tensile and tear strength as shown in Table IX. They both have very poor resistance to compression set. 

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