Molecular Weight Material Research Articles

Evaluation and degradation mechanism of phthalimide derivatives as anolytes for non-aqueous organic static batteries

Degrading mechanism demonstrates radical's dimerization, leading to an increase in number of OH groups and material's molecular weight. It inhibits undesirable cross-over of electrolytes and stabilises redox molecules through substantial H-bonding.

Moderately branched ultra‐high molecular weight polyethylene by using N,N′‐nickel catalysts adorned with sterically hindered dibenzocycloheptyl groups

Five examples of unsymmetrical 1,2‐bis (arylimino) acenaphthene (L1 – L5), each containing one N‐2,4‐bis (dibenzocycloheptyl)‐6‐methylphenyl group and one sterically and electronically variable N‐aryl group, have been used to prepare the N,N′‐nickel (II) halide complexes, [1‐[2,4‐{(C15H13}2–6‐MeC6H2N]‐2‐(ArN)C2C10H6]NiX2 (X = Br: Ar = 2,6‐Me2C6H3 Ni1, 2,6‐Et2C6H3 Ni2, 2,6‐i‐Pr2C6H3 Ni3, 2,4,6‐Me3C6H2 Ni4, 2,6‐Et2–4‐MeC6H2 Ni5) and (X = Cl: Ar = 2,6‐Me2C6H3 Ni6, 2,6‐Et2C6H3 Ni7, 2,6‐i‐Pr2C6H3 Ni8, 2,4,6‐Me3C6H2 Ni9, 2,6‐Et2–4‐MeC6H2 Ni10), in high yield. The molecular structures Ni3 and Ni7 highlight the extensive steric protection imparted by the ortho‐dibenzocycloheptyl group and the distorted tetrahedral geometry conferred to the nickel center. On activation with either Et2AlCl or MAO, Ni1 – Ni10 exhibited very high activities for ethylene polymerization with the least bulky Ni1 the most active (up to 1.06 × 107 g PE mol−1(Ni) h−1 with MAO). Notably, these sterically bulky catalysts have a propensity towards generating very high molecular weight polyethylene with moderate levels of branching and narrow dispersities with the most hindered Ni3 and Ni8 affording ultra‐high molecular weight material (up to 1.5 × 106 g mol−1). Indeed, both the activity and molecular weights of the resulting polyethylene are among the highest to be reported for this class of unsymmetrical 1,2‐bis (imino)acenaphthene‐nickel catalyst.

Revealing Sources and Distribution Changes of Dissolved Organic Matter (DOM) in Pore Water of Sediment from the Yangtze Estuary

Dissolved organic matter (DOM) in sediment pore waters from Yangtze estuary of China based on abundance, UV absorbance, molecular weight distribution and fluorescence were investigated using a combination of various parameters of DOM as well as 3D fluorescence excitation emission matrix spectra (F-EEMS) with the parallel factor and principal component analysis (PARAFAC-PCA). The results indicated that DOM in pore water of Yangtze estuary was very variable which mainly composed of low aromaticity and molecular weight materials. Three humic-like substances (C1, C2, C4) and one protein-like substance (C3) were identified by PARAFAC model. C1, C2 and C4 exhibited same trends and were very similar. The separation of samples on both axes of the PCA showed the difference in DOM properties. C1, C2 and C4 concurrently showed higher positive factor 1 loadings, while C3 showed highly positive factor 2 loadings. The PCA analysis showed a combination contribution of microbial DOM signal and terrestrial DOM signal in the Yangtze estuary. Higher and more variable DOM abundance, aromaticity and molecular weight of surface sediment pore water DOM can be found in the southern nearshore than the other regions primarily due to the influence of frequent and intensive human activities and tributaries inflow in this area. The DOM abundance, aromaticity, molecular weight and fluorescence intensity in core of different depth were relative constant and increased gradually with depth. DOM in core was mainly composed of humic-like material, which was due to higher release of the sedimentary organic material into the porewater during early diagenesis.

An enhanced host–guest electro‐optical polymer system using poly(norbornene‐dicarboximides) via ROMP

AbstractHigh glass transition temperature poly(N‐cyclohexyl‐5‐norbornene‐2,3‐dicarboximide)s (NDI)s prepared by ring opening metathesis polymerization yielded polymers with a narrow polydispersity and well‐controlled molecular weight materials when using the Grubbs first generation initiator. Polymers produced using the Grubbs second generation initiator could not be controlled easily. By initiator selection it was also possible to synthesize polymers with either 98 or 52% trans microstructures. These materials were employed as electro‐optic (EO) polymer hosts for high molecular hyperpolarizability (β) phenyl vinylene thiophene vinylene bridge chromophores. This chromophore was modified by the incorporation of a tert‐butyldiphenylsilane group. The addition was able to further increase its EO coefficient (r33) to reach 93 pm/V in a trans rich poly(NDI) produced by the Grubbs first generation initiator, compared to a benchmark chromophore / polymer combination. We investigated in detail the relationship between polymer microstructure and their absolute molecular weight on forming the best host–guest with the high β chromophore. Our results indicate that by utilizing a very simple host–guest system a high r33 can be realized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Effects of electron beam irradiation of cellulose acetate cigarette filters

A method to reduce the molecular weight of cellulose acetate used in cigarette filters by using electron beam irradiation is demonstrated. Radiation levels easily obtained with commercially available electron accelerators result in a decrease in average molecular weight of about six-times with no embrittlement, or significant change in the elastic behavior of the filter. Since a first step in the biodegradation of cigarette filters is reduction in the filter material's molecular weight this invention has the potential to allow the production of significantly faster degrading filters.

Effect of Thermal Degradation of SFF-Based PLGA Scaffolds Fabricated Using a Multi-head Deposition System Followed by Change of Cell Growth Rate

Solid free-form fabrication (SFF) technology is used to fabricate scaffolds with controllable characteristics including well-defined pore size and porosity. The multi-head deposition system (MHDS), one form of SFF technology, may be more advantageous than others for fabricating scaffolds because a MHDS does not require the use of a cytotoxic solvent. This method, however, may induce the thermal degradation of raw materials and a subsequent decrease in the material's molecular weight, whereby hydrolytic degradation, resulting in acidic by-products, might be accelerated. This study investigated whether fabrication of poly(lactic-co-glycolic acid) (PLGA) scaffolds using a MHDS with various residence times in the heating step induces thermal degradation and affects the proliferation of cells seeded on the scaffold in vitro. To answer this question, we fabricated porous three-dimensional PLGA scaffolds using residence times of 1, 3, 5 and 7 days for groups 1 through 4, respectively. Degradation behavior of the scaffolds was observed for 7 weeks in phosphate-buffered saline solution (pH 7.4) at 37°C. The molecular weight, glass transition temperature and mechanical properties were compared for PLGA scaffolds fabricated with each of the four residence times at 120°C. The proliferation rate of MC3T3-E1 cells grown on each group of scaffolds was compared to investigate the effect of acidic by-products on the growth of seeded cells in vitro. The heat process applied in fabrication of SFF-based PLGA scaffolds induced considerable thermal degradation followed by a decrease in molecular weight and mechanical compressive strength of the scaffolds in groups 3 and 4, which had more than 3 days residence time. Moreover, the cell proliferation rate was significantly higher for group 1 than for groups 3 and 4.

Estimation of Main Constituents of Ananus comosus (Pineapple) Leaf Fiber and Its Photo-Oxidative Degradation

An estimation of main constituents of pineapple leaf fiber (PALF) by conventional method was attempted and the values of 74.44% α-cellulose, 13.39% hemicellulose, 7.12% lignin, 2.89% pectic matter, and 0.58% aqueous extract were obtained. So, the main constituents of PALF are α-cellulose, hemicelluloses, and lignin. The molecular weight of raw, bleached PALF and α-cellulose of PALF were 1.517 × 105, 1.303 × 105, and 1.225 × 105, respectively. Bleached PALF was dyed with two dyes, Direct Green 27 and Acid Orange 52. Maximum dye exhaustion was found to be 98.97% for Direct Green 27 under the conditions of 3% dye concentration, 5% electrolyte concentration, and 70°C temperature, and 93.27% dye exhaustion was found for Acid Orange 52, where dyeing conditions were 4% dye concentration, 6% electrolyte concentration, and 80°C temperature. Dyeing time was fixed for 60 min for both dyes. The color fastness of PALF on exposure to sunlight has also been studied. It was observed that color fastness of raw fiber is higher than bleached fiber. The degradation of PALF under sunlight was studied by tensile strength and molecular weight measurements. Bleached fiber exhibited lesser loss of tensile strength and molecular weight than raw fiber. Infrared spectra (IR) of PALF were measured for different exposure times under sunlight. The PALF containing higher α-cellulose has good characteristics, similar to materials of higher molecular weight. For this, it gives high tensile strength, more dyeability, and better color fastness properties.

An experimental evaluation of the behaviour of mono and polydisperse polystyrenes in Cross-Slot flow

The behaviour of a number of mono and polydisperse polystyrenes are probed experimentally in complex extensional flow within a Cross-Slot geometry using flow-induced birefringence. Polystyrenes with similar molecular weight (M w) and increasing polydispersity (PD) illustrated the effect of PD on the principal stress difference (PSD) pattern in extensional flow. Monodisperse materials exhibited only slight asymmetry at moderate flowrates, although increased asymmetry and cusping was observed at high flowrates. The response of monodisperse materials of different M w at various flowrates is presented and characterised by Weissenberg numbers for both chain stretch and orientation using a theory for linear entangled polymers. The comparison of stress profiles against Weissenberg number for each process is used to determine whether the PSD pattern observed is independent of M w and elucidate which relaxation mechanism is dominant in the flow regimes probed. For monodisperse materials, at equivalent chain orientation Weissenberg number (We τd), different molecular weight materials were seen to exhibit similar steady state PSD patterns independent of We τR (chain stretch We). Whilst no obvious critical Weissenberg number (We) was found for the onset of increased asymmetry and cusping, it was found to occur in the “orientating flow without chain stretch” regime.

Crystallization of Poly(l-lactic acid) Probed with Dielectric Relaxation Spectroscopy

The properties of the amorphous component in poly(l-lactic acid), PLLA, depend on its crystalline structure, where the nanoconfinement effects may be monitored using dielectric relaxation spectroscopy. In this work this technique is used to monitor isothermal crystallization in PLLA by probing the evolution of the loss peak with crystallization time. It was found, for two different molecular weight materials and by crystallization from either the glassy or melt states, that the data could be given by a linear combination of three loss processes, where just their intensities vary: the α-process of the amorphous material, the constrained α-process present in the fully crystallized material, corresponding to the segmental motions of the amorphous phase confined by the crystalline lamellae, and the sub-glass β-relaxation. The appearance of the confined process was detected in the earlier stages of the crystallization, suggesting that the confinement effects are effective during primary crystallization. In this case, the cooperative segmental motions are restricted by the primary lamellae, leading to a dynamics characterized by a broader relaxation time distribution shifted to higher values. It was observed that the crystallization, as investigated by monitoring the evolution of the amorphous phase, is quicker for lower molecular weight PLLA and is slower for the material crystallized from the melt with respect to the cold crystallization. It was found that the confined dynamics is not very dependent on the thermal history prior to the crystallization step. The features of the β-relaxation were found to be similar for amorphous and semicrystalline systems, indicating that the sub-glass process in PLLA is not influenced by the crystalline confinement.

Processability of a metallocene‐catalyzed linear PE improved by blending with a small amount of UHMWPE

AbstractThe processability of a metallocene‐catalyzed polyethylene blended in the melt with low amounts of ultra‐high molecular weight polyethylene was evaluated. Our morphological and thermal studies revealed that the blends were structurally heterogeneous, formed by a matrix of metallocene polyethylene and homogeneously distributed particles of ultra‐high molecular weight material. The visible particles were smaller than those of the reactor powder. Also observed was some degree of interaction between both phases. Rheological data indicated an intense effect of morphology on viscoelastic functions, beyond that expected for a system composed of noninteractive phases. Collectively, our findings suggest the existence, to some extent, of a homogeneous phase at the molecular level composed of a fraction of ultra‐high molecular weight species and metallocene polyethylene. This gives rise to a striking behavior during processing in that the blends show improved extrusion performance the higher their ultra‐high molecular weight polyethylene content. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2963–2971, 2005

Investigation of foam‐active polypeptides during beer fermentation

AbstractDuring ale fermentation there was an accumulation of total and hydrophobic polypeptides in the foam relative to the wort. Comparisons were made not only of the total and hydrophobic polypeptide contents but also of the molecular weights of these polypeptides present in wort, partially fermented wort and its concomitant foam. Wort, fermented wort and foam fractions had very similar polypeptide compositions with a major group having molecular weights of 40–43 kDa. Material of molecular weight in the range of 5–17 kDa and at 66 kDa was also detected. The polypeptides accumulated in foam displayed both hydrophobic and non‐hydrophobic character. The presence of yeast polypeptides in foam was confirmed. Comparison was also made between the fermentations of 10°Plato and 15°Plato wort. The results of the work may contribute to a better understanding of the mechanism of foam formation during beer fermentation, leading to reduced foaming and enabling an increase in the working capacities of fermenters. Copyright © 2004 Society of Chemical Industry

Degradation of poly-L-lactide. Part 1: in vitro and in vivo physiological temperature degradation

Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioresorbable. The degradation of PLLA proceeds through hydrolysis of the ester linkage in the polymer's backbone and is influenced by the polymer's initial molecular weight and degree of crystallinity. To evaluate its degradation PLLA pellets were processed by compression moulding into tensile test specimens and by extrusion into 2 mm diameter lengths of rod, prior to being sterilized by ethylene oxide gas (EtO) and degraded in both in vitro and in vivo environments. On retrieval at predetermined time intervals, procedures were used to evaluate the material's molecular weight, crystallinity, mechanical strength, and thermal properties. Additionally, the in vivo host tissue's biological response was analysed. The results from this study suggest that in both the in vitro and in vivo environments, degradation proceeded at the same rate and followed the general sequence of aliphatic polyester degradation, ruling out enzymes contributing and accelerating the degradation rate in vivo. Additionally, the absence of cells marking an inflammatory response suggests that the PLLA rods investigated in vivo were biocompatible throughout the 44 weeks duration of the study, before any mass loss was observed.

Degradation of poly-L-lactide. Part 2: Increased temperature accelerated degradation

Poly-L-lactide (PLLA) is one of the most significant members of a group of polymers regarded as bioresorbable. The degradation of PLLA proceeds through hydrolysis of the ester linkages in the polymer's backbone; however, the time for the complete resorption of orthopaedic devices manufactured from PLLA is known to be in excess of five years in a normal physiological environment. To evaluate the degradation of PLLA in an accelerated time period, PLLA pellets were processed by compression moulding into tensile test specimens, prior to being sterilized by ethylene oxide gas (EtO) and degraded in a phosphate-buffered solution (PBS) at both 50 degrees C and 70 degrees C. On retrieval, at predetermined time intervals, procedures were used to evaluate the material's molecular weight, crystallinity, mechanical strength, and thermal properties. The results from this study suggest that at both 50 degrees C and 70 degrees C, degradation proceeds by a very similar mechanism to that observed at 37 degrees C in vitro and in vivo. The degradation models developed also confirmed the dependence of mass loss, melting temperature, and glass transition temperature (Tg) on the polymer's molecular weight throughout degradation. Although increased temperature appears to be a suitable method for accelerating the degradation of PLLA, relative to its physiological degradation rate, concerns still remain over the validity of testing above the polymer's Tg and the significance of autocatalysis at increased temperatures.

The Effects of Raw Material, Irradiation Dose, and Irradiation Source on Crosslinking of UHMWPE

Abstract Four Ultra-High Molecular Weight Polyethylene (UHMWPE) materials were evaluated after various irradiation crosslinking processes to determine the effects of the materials and processes on their properties for orthopaedic applications. The materials and processes included two molecular weight materials (GUR 1020 and GUR 1050), two fabricated forms (ram extruded bar and compression-molded sheet), two irradiation sources (gamma and e-beam) and multiple irradiation doses ranging from 30–120 kGy. Increasing irradiation dose led to increased crosslinking, decreased wear, and decreased toughness. The molecular weight of the starting material and the irradiation source both had effects on the final properties while the fabricated form did not. Wear testing of selected groups indicated that there was a direct correlation with irradiation dose but not with the crosslink density (as calculated from the swell ratio).

Determining the molecular weight, aggregation, structures and interactions of natural organic matter using diffusion ordered spectroscopy

AbstractDiffusion ordered spectroscopy (DOSY) was applied to examine the chemical and physical properties of soil organic matter, a complex natural mixture. Soil organic matter extracts are often termed humic substances (HS), which traditionally have been thought to be high molecular weight, cross‐linked macromolecules with undetermined structures. Separation of the components in the studied humic acid (HA) clearly indicates that the HS studied here are pseudo‐high molecular weight materials only, and associations or aggregates of molecules of smaller molecular sizes, which can be disrupted with organic acids. At high concentration, these aggregates display diffusivities that are consistent with those observed in large proteins (>66 kDa). After disaggregation and at low concentration, DOSY NMR reveals components that have chemical shifts that are consistent with lignins, polysaccharides and peptides, and have diffusivities consistent with molecular weights of ∼2500, ∼1000 and 200–600 Da, respectively. Diffusion studies of fulvic acids (FA) indicate that little if any aggregation occurs in solution and that, on average, the components display diffusivities that are consistent with molecules that have relatively low molecular weights of ∼1000 Da. However, in addition to a range of small molecular components, DOSY NMR reveals for the first time direct evidence that larger molecular weight components also exist within the mixtures. In an FA isolated from the surface soil of an oak forest, large polysaccharides with average diffusivities similar to 6000 Da maltodextrins can be identified. In an FA from an agricultural soil, components consistent with peptides/proteins are identified that have aggregate/molecular sizes in the region of 12 000 Da. It is logical that an operationally defined extract of soils will result in a mixture of plant components at various stages of humification with a range of molecular sizes and structures rather than macromolecules with undetermined structures. In addition to advancing our structural understanding of natural organic matter (NOM), DOSY provides potential to study the interactions of these mixtures with contaminants. This paper explorers the interaction of a HA with two organic contaminants (MTBE and chlorsulfuron) and an FA with cadmium. Diffusion measurements show that MTBE has a weaker interaction with the organic materials than chlorsulfuron. Studies with cadmium suggest that the metal exhibits dynamic exchange which is fast on the NMR time‐scale. Such findings have strong implications for understanding the behavior and toxicity of cadmium in the environment. Although cadmium has an affinity for NOM, it is clear that it is not irreversibly bound and may be bioavailable under many conditions. Copyright © 2002 John Wiley & Sons, Ltd.

Synthesis and characterization of a fluorinated polyanhydride

AbstractA fluorinated aromatic polyanhydride (B) was synthesized from the melt condensation of mixed anhydrides of 4,4′‐(hexafluoroisopropylidene)bis benzoic acid. Although the mixed anhydride from acetic anhydride yielded only a mixture of oligomers (weight‐average molecular weight < 2000), higher weight‐average molecular weight materials in the range of 15,000–18,000 were obtained with trifluoroacetic anhydride. Polymer B was soluble in chloroform and tetrahydrofuran, had a relatively high glass‐transition temperature of 176 °C with no melting point detected to 310 °C, and showed excellent thermal stability (5% weight loss observed at 380 °C by thermogravimetric analysis). The hydrolytic degradation of the fluorinated polyanhydride in a 0.1 M phosphate buffer of pH 7.4 at 37 °C was initially zero‐order, with 35% degradation occurring in 10 days. Loss of film integrity following that led to accelerated degradation, and almost complete dissolution was observed by the 16th day. The stability of the fluorinated polyanhydride in the solid state and in the solvent tetrahydrofuran was also evaluated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3027–3036, 2002

An expression of IGF-binding proteins in normal and pre-eclamptic human umbilical cord serum and tissues.

Pre-eclampsia, is the most common, pregnancy-associated pathological syndrome accompanied by a significant increase in collagen and sulphated glycosaminoglycans (GAGs) contents in the umbilical cord arteries (UCAs). Insulin-like growth factor-I (IGF-I) is expressed in most foetal tissues and it is involved in anabolic effects. It stimulates protein (mainly collagen) and GAG biosynthesis, cell proliferation and differentiation. Previously, we have found that pre-eclampsia is associated with an increase of IGF-I concentration in the umbilical cord blood. A family of IGF-I-binding proteins (BPs) modulates the activity of IGF-I. We demonstrated qualitative differences between BPs of normal and pre-eclamptic human umbilical cord (UC) serum and UC-tissues (UCA-wall and Wharton's jelly) by Western immunoblot analysis. All examined sera and tissues contained BP-1 and BP-5 as well lower molecular weight materials. The BP-2 was recovered from both control and pre-eclamptic sera, while it was not detected in the UC-tissues. Instead, lower molecular weight forms of BP-2 were found as judged by the anti-BP-2 antibody. The BP-3 was detected in sera, UCA and Wharton's jelly. The most distinct expression of BP-3 was found in the UCA. The pre-eclamptic UCA and Wharton's jelly contained additional BP-3-reactive material of lower molecular weight. The BP-4 was strongly expressed in pre-eclamptic UC-serum and the expression was decreased in pre-eclamptic UC-tissues, compared to respective controls. Ligand binding assay revealed that most of IGF-I was bound to 46 kDa region (typical for BP-3) in both control and pre-eclamptic sera and tissues. However, distinctly less IGF-I was bound in pre-eclamptic serum, distinctly more in pre-eclamptic UCA and no differences were found in pre-eclamptic Wharton's jelly, compared to controls. We demonstrated that both normal and pre-eclamptic UC-sera and tissues are able to degrade 46 kDa IGF-I-BP. The degradation may result in a decrease of IGF-I binding, contributing to increase in free IGF-I that may stimulate the cells to produce extracellular matrix (ECM) components. The specific BPs and their proteolytic modification in UC tissues may be important modulators of IGF-I action during foetal development.

The linear viscoelastic behavior of highly filled polydimethylsiloxane measured in shear and compression

The frequency and time dependent moduli of up to 60% glass bead filled polydimethyl siloxane (PDMS) were studied for four different molecular weight materials with a rotational, compressional, and lubricated squeezing flow rheometer. Measurements of the storage and loss modulus taken with a conventional rotational instrument show good qualitative and quantitative agreement with those taken with a newly developed oscillatory compressional rheometer for PDMS of the lowest molecular weight studied, and show trends similar to those reported previously for similar materials. The agreement between the two instruments is better for both unfilled and 35% filled material of a higher molecular weight. Good agreement was also observed between measurements of the relaxation modulus in lubricated squeezing flow and measurements of the storage modulus with the new compressional device for a high molecular weight PDMS at all filler levels. The modulus derived from oscillatory measurements showed good quantitative agreement with that measured in lubricated squeezing flow for identical materials. The effect of polymer molecular weight on the relative behavior of the loss and storage modulus with increasing filler content was also studied. It was shown that as the polymer molecular weight increases, the ratio of the loss to storage modulus becomes nearly independent of the filler volume fraction over the frequency range studied. The effect of an increase in filler amount on the elasticity of the material was shown to depend both on the polymer molecular weight and the frequency, and is explained in terms of the influence of the filler on the Deborah number of the system.

The Combined Influence of Molecular Weight and Temperature on the Physical Aging and Creep Compliance of a Glassy Thermoplastic Polyimide

The effect of molecular weight on the viscoelastic performance of anadvanced polymer (LaRC™-SI) was investigated through the use of creepcompliance tests. Testing consisted of short-term isothermal creep andrecovery with the creep segments performed under constant load. Thetests were conducted at three temperatures below the glass transitiontemperature of five materials of different molecular weight. Through theuse of time-aging-time superposition procedures, the material constants,material master curves and aging-related parameters were evaluated ateach temperature for a given molecular weight. The time-temperaturesuperposition technique helped to describe the effect of temperature onthe timescale of the viscoelastic response of each molecular weight. Itwas shown that the low molecular weight materials have higher creepcompliance and creep rate, and are more sensitive to temperature thanthe high molecular weight materials. Furthermore, a critical molecularweight transition was observed to occur at a weight-average molecularweight of $${\bar M}$$ w ∼ 25,000 g/mol below which, the temperature sensitivity of thetime-temperature superposition shift factor increases significantly. Theshort-term creep compliance data were used in association with Struik'seffective time theory to predict the long-term creep compliance behaviorfor the different molecular weights. At long timescales, physical agingserves to significantly decrease the creep compliance and creep rate ofall the materials tested. Long-term test data verified the predictivecreep behavior. Materials with higher temperature and lower molecularweights had greater creep compliance and higher creep rates.

Modified Theory of Welding Line and Optimal Design of Material Parameter for a Thin Part in the Injection Mould

In this paper, based on thin-wall moulding under high processing pressure, we develop a theoretical model containing the pressure term by combining the Williams-Landel-Ferry(WLF) semi-experimental equation and the weld-line strength model of the molecular chains crossing the interface and self-diffusion. Then, the optimal theory is applied to find the optimal material. According to the theoretical model, high pressure would lead to a high viscosity and a low molecular diffusion to reduce the degree of bonding. The traditional weld-line theory cannot modify this fact, however. Therefore, it would be more accurate for a thin part to predict the degree of bonding by applying the theoretical model with the pressure term from the analytical result, it would be better for using a higher melt temperature in the moulding process. For thin-walled material, it is better to select a material with a lower density, lower plateau modulus, higher R 2 /M W ratio, lower molecular weight and lower glass transition temperature material with the allowable range of mechanical properties.