Impact-resistance

PLA impact resistance also depends on molecular weight. Charpy impact strength values of 8 and 15 kJ/m have been 

Therefore, since PLA is a material that is characterized by relatively low values of impact resistance, the effect of crystallinity and molecular weight has to be taken into consideration in practical applications. 

Fillers improve the impact strength of the filled materi-.3-4,7,14,17,20,23-4,4,43-6,50,64,69-75,81,87,89,96,97,101-119 analysis of impact Strength 

The results of experimental studies which are summarized in Table 8.2 show the potential effect of different fillers on impact properties of filled materials. The information in Table 8.2 is presented in the same format as explained in introduction to Table 8.1. 

Filler/polymer Cone, range, wt% Impact strength increase(+) decrease (-), % Refs Comments 

Magnesium hydroxide PP 10-60 -27—70 64 metal stearate coating can double IS 

muscovite PA66 PBT PEK PP 20-40 15-40 10-30 2-20 vol% -30—15 +15—35 -50—70 +5 +26 50 50 23 105 varies with particle size and amount varies with particle size and amount used in combination with CaCO  

ISO 13428 Geosynthetics Determination of the Protection Efficiency of a Geosynthetic Against Impact Damage 

A steel ball with a mass of 1 kg is used to simulate the impact damage on a lead plate protected with a GTX test specimen using a faUing head of 1 m. The result is used to determine the protection efficiency of a geosynthetic to prevent a geosynthetic barrier against impact damage (Table 7.14 and Fig. 7.19). 

DIN V 60500-1, June 1999 Geotextiles and GTX-Related Products Determination of Resistance to Damage During Installation (Pyramid Drop Test) 

Subbase 1.8-mm-thick lead plate on 40-mm-thick steel plate 

Objects other than balls or cones are used as index tests for GTXs. The pyramid drop test is similar to the cone drop test but with a different shape. The pyramid should represent the angularity of a stone but the test is not used in this industry. 

As shown in Fig. 4.56,the reinforcement of latex-modified concretes with steel fibers causes a pronounced improvement in the impact strength with increased polymer-cement ratio and steel fiber content 

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Nylon A class of synthetic fibres and plastics, polyamides. Manufactured by condensation polymerization of ct, oj-aminomonocarboxylic acids or of aliphatic diamines with aliphatic dicarboxylic acids. Also rormed specifically, e.g. from caprolactam. The different Nylons are identified by reference to the carbon numbers of the diacid and diamine (e.g. Nylon 66 is from hexamethylene diamine and adipic acid). Thermoplastic materials with high m.p., insolubility, toughness, impact resistance, low friction. Used in monofilaments, textiles, cables, insulation and in packing materials. U.S. production 1983 11 megatonnes. 

The annual production of styrene in the United States is approximately 1 2 X 10 lb with about 65% of this output used to prepare polystyrene plastics and films Styrofoam coffee cups are made from polystyrene Polystyrene can also be produced m a form that IS very strong and impact resistant and is used widely m luggage television and radio cabinets and furniture... 

Not all synthetic polymers are used as fibers Mylar for example is chemically the same as Dacron but IS prepared in the form of a thin film instead of a fiber Lexan is a polyester which because of its impact resistance is used as a shatterproof substitute for glass It IS a polycarbonate having the structure shown... 

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. 

It is characterized by high strength and good impact resistance, and retains its physical properties at temperatures up to 260°C. Its radiation (gamma) resistance is good. 

Impact properties Impact resistance Impact resistant PP IMP ATT device IMPATTs... 

Styrene—acrylonitrile (SAN) copolymers [9003-54-7] have superior properties to polystyrene in the areas of toughness, rigidity, and chemical and thermal resistance (2), and, consequendy, many commercial appHcations for them have developed. These optically clear materials containing between 15 and 35% AN can be readily processed by extmsion and injection mol ding, but they lack real impact resistance. 

Thermal Oxidative Stability. ABS undergoes autoxidation and the kinetic features of the oxygen consumption reaction are consistent with an autocatalytic free-radical chain mechanism. Comparisons of the rate of oxidation of ABS with that of polybutadiene and styrene—acrylonitrile copolymer indicate that the polybutadiene component is significantly more sensitive to oxidation than the thermoplastic component (31—33). Oxidation of polybutadiene under these conditions results in embrittlement of the mbber because of cross-linking such embrittlement of the elastomer in ABS results in the loss of impact resistance. Studies have also indicated that oxidation causes detachment of the grafted styrene—acrylonitrile copolymer from the elastomer which contributes to impact deterioration (34). 

Acrylonitrile—Butadiene—Styrene. Available only as sheet, ABS has good toughness and high impact resistance. It is readily therm oform able over a wide range of temperatures and can be deeply drawn. ABS has poor solvent resistance and low continuous-use temperature. It is often used in housings for office equipment (see Acrylonitrile polymers). 

ASTM E23-93, "Notched Bar Impact Testing of MetaUic Materials," Annual Book of ASTM Standards, ASTM Puhhcations, Philadelphia, 1993. ASTM D256-92, "Impact Resistance of Plastics and Electrical Materials," Annual Book of ASTM Standards, ASTM Puhhcations, Philadelphia, 1993. A. N. Atiuri and T. Nishioka, Int. / fract. 27, 245 (1985). 

The neady symmetrical composition of SBI-PC (T = 230° C) makes birefringence disappear iu homopolymers, but the material becomes very britde due to the blocking of the free rotation of the aromatic rings, which puts its technical appHcation iu question. Only a copolymerization with 80 wt BPA-PC reaches sufficient levels of impact resistance but T is lowered to 170°C and birefringence iucreases to 80% of that of BPA-PC (195,196). In contrast, TMC-PC as a homopolymer already has sufficient impact resistance at a T of 238°C and a birefringence of 83% of that of BPA-PC (195,205) (Table 7). 

Special, uv-curable epoxy resins (qv) for substrate disks for optical data storage (Sumitomo BakeHte, Toshiba) excel by means of their very low birefringence (<5 nm/mm) and high Young s modulus. Resistance to heat softening and water absorption are similar to BPA-PC, but impact resistance is as low as that of PMMA. 

The constmction of the E-111 windshield shown in Eigure 8 replaced a glass—silicone laminate previously used. The all-plastic windshield has improved impact resistance so that it is birdproof to 250 m/s (33). In this instance, the scratch resistance of glass was waived to obtain the impact performance at the allowed weight. 

Modifiers. Latices are added to bitumens, mortars, and concrete to improve impact resistance and reduce stress cracking. Key to the use of latices in these technologies is compatibiHty between the latex and the constmction materials. 

Plastic Sheet. Poly(methyl methacrylate) plastic sheet is manufactured in a wide variety of types, including cleat and colored transparent, cleat and colored translucent, and colored semiopaque. Various surface textures ate also produced. Additionally, grades with improved weatherabiUty (added uv absorbers), mat resistance, crazing resistance, impact resistance, and flame resistance ate available. Selected physical properties of poly(methyl methacrylate) sheet ate Hsted in Table 12 (102). 

Low Temperature Brittleness. Brittleness temperature is the temperature at which polyethylene becomes sufficiently brittle to break when subjected to a sudden blow. Because some polyethylene end products are used under particularly cold climates, they must be made of a polymer that has good impact resistance at low temperatures namely, polymers with high viscosity, lower density, and narrow molecular weight distribution. ASTM D746 is used for this test. 

Polypropylene polymers are typically modified with ethylene to obtain desirable properties for specific applications. Specifically, ethylene—propylene mbbers are introduced as a discrete phase in heterophasic copolymers to improve toughness and low temperature impact resistance (see Elastomers, ETHYLENE-PROPYLENE rubber). This is done by sequential polymerisation of homopolymer polypropylene and ethylene—propylene mbber in a multistage reactor process or by the extmsion compounding of ethylene—propylene mbber with a homopolymer. Addition of high density polyethylene, by polymerisation or compounding, is sometimes used to reduce stress whitening. In all cases, a superior balance of properties is obtained when the sise of the discrete mbber phase is approximately one micrometer. Examples of these polymers and their properties are shown in Table 2. Mineral fillers, such as talc or calcium carbonate, can be added to polypropylene to increase stiffness and high temperature properties, as shown in Table 3. 

Random insertion of ethylene as comonomer and, in some cases, butene as termonomer, enhances clarity and depresses the polymer melting point and stiffness. Propylene—butene copolymers are also available (47). Consequendy, these polymers are used in apphcations where clarity is essential and as a sealant layer in polypropylene films. The impact resistance of these polymers is sligbdy superior to propylene homopolymers, especially at refrigeration temperatures, but still vastiy inferior to that of heterophasic copolymers. Properties of these polymers are shown in Table 4. 

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