摘要:

AbstractThe melt flow index and oxidation induction period of low‐density polyethylene crosslinked with dicumyl peroxide (DCP) in the presence of tetrakis (methylene β‐3, 5‐di‐butyl‐4‐hydroxypheny1)‐propionate methane (Antioxidant 1010) were determined. The results suggest that there is a negative synergism between this crosslinking agent and antioxindant. Part of the antioxidant terminated the chain propagation by trapping radicals, and thus reduced the efficiency of crosslinking. The antioxidant efficiency was also reduced owing to meaningle

ISSN:0032-3888    

DOI:10.1002/pen.760321402

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe structure and properties of a preimidized photosensitive polyimide (Probimide PSPI, a copolyimide of benzophenonetetracarboxylic dianhydride with alkyl groups substituted aromatic diamines) were studied with variations of UV exposure energy and bake temperature by means of wide angle X‐ray diffraction, dynamic mechanical thermal analysis, stress‐strain analysis, and residual stress analysis. The X‐ray diffraction patterns patterns indicate that the PSPI is amorphous in the solid state. TheTgwas 378°C ∼ 410°C, depending upon the thermal history over the range of 350°C ∼ 400°C. At the glass transition region, the dynamic storage modulusE′ was very sensitive to both i‐line exposure energy and thermal history. However, the mechanical stress‐strain behavior at room temperature was primarily dependent on the thermal history. The mechanical properties were 2.6 GPa ∼ 2.9 GPa Young's modulus, 131 MPa ∼ 168 MPa tensile strength, 10% ∼ 12% yield strain, and 16% ∼ 74% elongation at break, depending upon the baking or annealing. These dynamic and static mechanical properties indicate that on the PSPI backbone, crosslinks are formed thermally as well as photochemically. The thermal crosslinks might be formed through thermal liberation of the labile alkyl groups of aromatic diamine moieties and subsequent coupling of the radicals. The thermal degradation was also evidenced in the mechanical properties degraded by baking above 375°C or annealing above 350°C. In addition, during baking and cooling, the residual stress was dynamically measured on Si wafers as a function of temperature. The stress at room temperature was 48 MPa ∼ 52 MPa for the PSPI films baked at 350°C or 400

ISSN:0032-3888    

DOI:10.1002/pen.760321403

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractSteady‐shear‐viscosity data sets for commercial‐grade acrylonitrile‐butadiene‐styrene terpolymer, nylon, polycarbonate, poly(methylmethacrylate), and polystyrence are fitted in terms of a generalized Cross/Carreau modeling for the shear‐rate dependence. Based upon extensive data sets from the open literature as well as in‐house measurements, it is shown that the shear‐rate dependence can be more accurately described in terms of the Cross rather than Carreau model. Although the resulting viscosity fits based upon these two models might differ by 20% or more for the same well‐characterized data set, the resulting effect upon simulating the injection‐molding process is found to be much smaller since such predictions reflect a range of shear stresses (varying linearly from centerline to wall of cavity) over which the two models alternate in relative magnitude. This is demonstrated by detailed representative numerical predictions which are presented for both the filling and

ISSN:0032-3888    

DOI:10.1002/pen.760321404

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effects of molecular structure on the dicumyl peroxide crosslinking of two low density polyethylenes have been studied. Peroxide efficiency was determined largely by the content of terminal vinyls in the two polymers. Differences in molecular weight distribution and branch content had comparatively little influence on the gel content but hot creep resistance of the vulcanized materials was affected. Scorching was affected, also, by the presence of vinyl unsaturations in the polymer.

ISSN:0032-3888    

DOI:10.1002/pen.760321405

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe ability to evaluate various mechanical test parameters of polymers using an instrumented impact tester is reviewed. The nature of the short chain branching (SCB) in a series of linear low density polyethylenes (LLDPE) was characterized and related to several impact test parameters for these materials. The impact strength, ductility, and impact fatigue life were observed to increase with increasing branch length. This was attributed, in fact, to an increase in the number of interlamellar tie molecules as the SCB length increased. With an increase in the SCB length the SCB distribution became broader; the number of chains rich in short chain branches increased. This component acts somewhat like the rubber particles in a rubber‐toughened blend which gives rise to the concept of a “one copolymer ble

ISSN:0032-3888    

DOI:10.1002/pen.760321406

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe influence of intracomplex metal compounds, namely, copper salicylate and cadmium anthranilate on the properties of diglycidyl bis‐phenol A ether (DGEBA) hardened with diethylene triamine and triethylene tetramine has been investigated. The dependence of hardenability of the amines modified with the salts on the content of the salts has been determined. The saturation of the amines with salts has been shown to result in formation of hardeners affording good stability of compositions. The above fact can be attributed to the blocking of the amino nitrogen atoms by the metals and neutralization of the hydrogen atoms with the anions. The properties of metal‐containing polymers has been studied; increases of their strength indices and heat stability in comparison with the initial aliphatic amines have been establis

ISSN:0032-3888    

DOI:10.1002/pen.760321407

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe relationships between the supermolecular structure of poly(ethylene terephthalate) films subjected to cold drawing and subsequent zone annealing and their mechanical properties are investigated. The effectiveness of zone annealing is compared to that of annealing with fixed ends. Microstructural changes occurring during heat treatment and zone annealing are monitored using wide angle X‐ray scattering, small angle X‐ray scattering, infrared spectroscopy, differential scanning calorimetry, and static mechanical tests. The very high modulus and strength of the zone‐annealed films are directly attributed to the large number of the molecules connecting the crystal

ISSN:0032-3888    

DOI:10.1002/pen.760321408

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effects of short carbon fibers on static and dynamic properties of thermoplastic elastomeric blends of natural rubber (NR) and high density polyethylene (HDPE) have been studied. Both mechanical and dynamic properties are dependent on fiber concentration. The fiber aspect ratio ranges from 20 to 30. Adhesion between fiber and matrix is evident from the SEM photomicrographs of the failed composites and from variation of relative damping properties. Fiber orientation occurring during processing causes anisotropy in the physical properties. In composites with longitudinally oriented fibers, tensile failure occurs by both fiber pullout and breakage, while in composites with transversely oriented fibers, matrix failure dominates. The incorporation of fibers into the matrix lowers the tan δmaxvalue, but no change in glass transition temperature is observed

ISSN:0032-3888    

DOI:10.1002/pen.760321409

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760321410

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760321401

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY