Vibration welding of thermoplastics. Part IV: Strengths of poly(butylene terephthalate), polyetherimide,and modified polyphenylene oxide butt welds

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration.; The effects of these parameters on weld quality were systematically studied by first butt welding thermoplastic specimens under controlled conditions, over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests. The three thermoplastics investigated are poly (butylene terephthalate), polyetherimide, and modified polyphenylene oxide. Changes in the weld pressure are shown to have opposite effects on the strengths of polyetherimide and modified polyphenylene oxide welds; Also, the weld frequency is shown to have a significant effect on the weldability of polyetherimide. The weldability data for these three thermoplastics are compared with data for polycarbonate. Under the right conditions, the strengths of butt welds in these materials are shown to equal the strength of the virgin polymer.     

The vibration welding of poly(methyl methacrylate) to itself and to polycarbonate,poly(butylene terephthalate), and modified poly(phenylene oxide)

The weldability of poly(methyl methacrylate) (PMMA) to itself and to polycarbonate (PC), poly(butylene terephthalate) (PBT), and modified poly(phenylene oxide) (M-PPO) is assessed through 120 and 250 Hz vibration welds. Weld strengths equal to those of the base resin have been demonstrated in welds of PMMA and M-PPO to themselves. In welds of PMMA to PC and to M-PPO, weld strengths equal to those of PC and M-PPO, respectively, have been demonstrated. PMMA does not weld well to PBT; the highest weld strength obtained was 21% of the strength of PBT resin.     

PTFE改性玻纤增强MPPO材料力学性能及耐摩擦磨损性能的研究

采用直径为3.0μm的短玻纤(GF)(GF质量分数为20％)增强改性聚苯醚(MPPO),将其与粒径为5～7 μm的聚四氟乙烯(PTFE)微粉和甲基苯基硅油构成摩擦因数较低的耐磨体系.通过熔融共混法制备PTFE改性GF增强MPPO材料(简称MPPO/20％GF复合材料).对MPPO/20％GF复合材料的力学性能、热变形温...     

The vibration welding of polycarbonate/acrylonitrile‐butadiene‐styrene blends to themselves and to other resins and blends

The weldabilities of two commercial blends of polycarbonate (PC) and acrylonitrile‐butadiene‐styrene (ABS) to themselves and to several other resins and blends are assessed through 120 Hz vibration welds of 6.35‐ and 3.2‐mm‐thick specimens. While the thicker specimens of both blends have relative weld strengths of 83%, the thinner specimens in one of the grades have a lower relative weld strength of 73%. Welds of thicker specimens of both grades to PC have relative strengths of 85%. Again, welds of thinner specimens of one of the grades to PC have a lower relative strengths of 68%. Welds of the thinner specimens of this grade with ABS have relative strengths of 85%. Welds of this material with poly(butylene terephthalate) (PBT), a PC/PBT blend, modified poly(phenylene oxide), and a poly(phenylene oxide)/polyamide blend, have relative weld strengths of 45%, 26%, 76%, and 20%, respectively.     

The vibration welding of poly(phenylene oxide)/poly(phenylene sulfide) blends

The weldability of three blends of poly(phenylene oxide) and poly(phenylene sulfide), each with a different level or type of impact modifier, is assessed through 120 and 240 Hz vibration welds. The type of impact modifier is shown to have a large effect on the strength and ductility of welds. Weld strength in these blends is shown to be sensitive to the weld frequency; higher weld strengths are attained at the higher weld frequency. In these three blends, maximum relative weld strengths of about 70%, 85%, and 87% have been demonstrated at a weld frequency of 240 Hz. The highest weld strength in each of these three blends is achieved at different weld pressures.     

Fatigue strength of vibration welded thermoplastic butt joints

Fatigue data are presented for the strengths of 120-Hz vibration-welded butt joints of four resins: the three amorphous polymers polycarbonate (PC), polyetherimide (PEI), and modified polyphenylene oxide; and the semicrystalline polymer poly(butylene terephthalate). Data are also presented for the fatigue strength of 250-Hz vibration welds of the high-temperature polymer PEI. For all the welds, fatigue strength was evaluated through 10-Hz, tension-tension, load-controlled tests at an R value (ratio of minimum stress) of 0.1. Surprisingly, for all the stress levels studied, none of the PC test specimens failed at the welds, indicating that the fatigue strength of PC welds equals that of the base resin. This is not true of the other three resins, except at relatively low stress levels. For each of the four resins, macrographs are used to highlight the differences between the failure surfaces of monolithic specimens and specimens that failed at the welds.     

Preparation of high performance adhesives matrix based on epoxy resin modified by bis-hydroxy terminated polyphenylene oxide

A bis-hydroxy terminated polyphenylene oxide (MPPO) modification was tried for the purpose of simultaneously enhancing the processability and heat resistance of epoxy resin. The thermal stability, chemorheology, morphology and mechanical properties of epoxy-polyphenylene oxide blends were investigated, respectively. The structure of MPPO was characterized by nuclear magnetic resonance and fourier transform infrared spectroscopy which indicated that MPPO was successfully synthesized. Epoxy-polyphenylene oxide blends exhibited a wide range of processing temperature mainly owing to the existence of bis-hydroxy in MPPO. Mechanical properties results revealed that the impact strength, tensile strength and elongation at break of MPPO/EP systems were performed satisfactorily. Scanning electron microscopy studies revealed the two-phase morphology and modification mechanism of the epoxy-polyphenylene oxide. Dynamic mechanical analysis and thermal gravimetric analyzer results showed that the introduction of MPPO leading to an enhancement to the thermal stability of epoxy matrix. Therefore, epoxy-polyphenylene oxide blends meet the requirements for the prepreg and high performance adhesives matrix.     

Vibration welding of nylon 6 to nylon 66

Vibration welding of dissimilar nylons is a promising technique for assembling complex components made of different polymers. The effects of pressure and meltdown on the tensile strength of nylon 6 (PA 6) to nylon 66 (PA 66) vibration welds were determined in this study using an experimental design and three weld geometries. Weld strengths were generally improved by increasing meltdown and decreasing weld pressure. The weld strength was also shown to vary with the position of the lower melting material for T‐welds. Using differential scanning calorimentry and fracture surface analyses, it is concluded that for all geometries, higher weld strengths can be achieved when both materials are melted. Polym. Eng. Sci. 44:760–771, 2004. © 2004 Society of Plastics Engineers.     

Vibration welding of glass-filled poly(styrene-co-maleic anhydride)

Vibration welding is used to assess the weldability of 16 wt% glass-filled poly(styrene-comaleic anhydride) (16-GF-SMA). Data are presented on the strengths of butt welds for two specimen thicknesses and T-welds for one specimen thickness. The maximum weld strength of butt joints is shown to be only 35% of the tensile strength of the material. T-joints are shown to have only 61% of the strength of butt joints. The relative butt-weld strengths of 16-GF-SMA are much lower than those measured in other glass filled resins: 71% in a 20-wt% glass-filled modified poly(phenylene oxide); 68 and 60%, respectively, in 15- and 30-wt% glass-filled grades of poly(butylene terephthalate); and 58% in a 40-wt% glass-filled polyamide 6,6.     

Flame retardancy and toughening of high impact polystyrene

Flame retardant high impact polystyrene (HIPS) was prepared by melt blending HIPS, nano‐modified aluminum trihydrate (nano‐CG‐ATH), red phosphorus masterbatch (RPM), and modified polyphenylene oxide (MPPO). Styrene‐butadiene‐styrene (SBS) was used as a toughener in this research. The effects of nano‐CG‐ATH, RPM, MPPO, and SBS on properties of HIPS composites were studied by combustion test, mechanical tests, and thermogravimetric analysis. The morphologies of fracture surfaces and char layers were characterized through scanning electron microscopy (SEM). The HIPS/nano‐CG‐ATH/RPM/MPPO (60/6/9/25) composite and its combustion residues at various temperatures were characterized by Fourier transform infrared (FTIR) spectra analysis. The results showed that the UL‐94 rating of the HIPS/nano‐CG‐ATH/RPM/MPPO (60/6/9/25) composite reached V‐0 and its char layer after flame test was integrated, but its impact strength was low. Addition of SBS improved its impact property and did not influence its thermal and flame retardant properties but lowered its tensile strength and flexural modulus to some extent. The FTIR spectra confirmed that the P O C group was present in the charred substance. POLYM. COMPOS., 28:551–559, 2007. © 2007 Society of Plastics Engineers     

Vibration welding of thermoplastics. Part III: Strength of polycarbonate butt welds

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time or weld penetration; The effects of these parameters on weld quality were systematically studied by first butt-welding polycarbonate specimens under controlled conditions over a wide range of process parameters, and by then determining the strengths and ductilities of these welds by tensile tests, A significant result is the apparent existence of a weld-penetration threshold above which high weld strengths are attained, but below which the strength drops off. Under the right conditions, the strengths of polycarbonate butt welds are shown to equal the strength of the virgin polymer.     

Experiments on the induction welding of thermoplastics

In induction welding of thermoplastics, induction heating of a gasket, made of a ferromagnetic‐powder‐filled bonding material and placed at the interface of thermoplastic parts to be joined, is used to melt the interface; subsequent solidification of the melt results in a weld. Tensile tests on induction butt‐welds of polycarbonate (PC), poly(butylene terephthalate) (PBT), and polypropylene (PP) are used to characterize achievable weld strengths, and microscopy is used to correlate weld strength with the morphology of failure surfaces. In PC, PBT, and PP relative weld strengths as high as 48%, 43%, and 55% of the respective strengths of PC, PBT, and PP have been demonstrated. Relative weld strengths on the order of 20% have been demonstrated in PC‐to‐PBT welds.     

Cross-thickness vibration welding of polycarbonate,polyetherimide, poly(butylene terephthalate), and modified polyphenylene oxide

In vibration welding of thermoplastics, frictional heat generated by vibrating two parts under pressure, along their common interface, is used to effect welds. In the normal, well-understood mode, the vibratory motion is along the weld seam, which is at right angles to the thickness direction for straight boundaries. But in many applications, such as in the welding of closed seams of box-like parts, this vibratory motion occurs in the part-thickness direction, so that a portion of the molten layer along the seam is exposed to the ambient air during each vibratory cycle. The resulting reduction in temperature can affect weld quality. The process phenomenology and the weld strengths of such cross-thickness vibration-welded butt joints are investigated for four neat resins. Weld amplitudes and weld pressures are shown to affect the strengths of 120-Hz welds differently. It is shown that strengths on the order of the strengths of the neat resins can be achieved in 250-Hz butt welds.     

玻璃纤维增强改性聚苯醚的研究

采用高抗冲聚苯乙烯(HIPS)及玻璃纤维(GF)对聚苯醚(PPO)进行共混改性,探讨了GF含量与改性PPO(MPPO)流动性能、拉伸强度、断裂伸长率、弯曲强度、冲击强度及热性能的关系;并研究了偶联剂(KH-550)对MPPO微观形态的影响及苯偶姻与MPPO力学性能的关系。     

The vibration welding of poly(butylene terephthalate) and a polycarbonate/poly(butylene terephthalate) blend to each other and to other resins and blends

Vibration welding is used to assess the weldability of poly(butylene terephthalate) (PBT) and a polycarbonate/poly(butylene terephthalate) blend (PC/PBT) to each other and to other resins and blends: PBT to PC/PBT, PBT to modified poly(phenylene oxide) (M-PPO), PBT to polyetherimide (PEI) and PEI to a 65 wt% mineral-filled polyester blend (65-PF-PEB), PBT to a poly(phenylene oxide)/polyamide blend (PPO/PA), PC/PBT to M-PPO, and PC/PBT to PPO/PA. Based on the tensile strength of the weaker of the two materials in each pair, the following relative weld strengths have been demonstrated: PBT to PC/PBT,98%; PBT to PEI, 95%; 65-PF-PEB to PEI, 92%; and PC/PBT to M-PPO, 73%. PBT neither welds to M-PPO nor to PPO/PA, and PC/PBT does not weld to PPO/PA.     

The vibration and hot‐tool welding of polyamides

The weldabilities of polyamide 6 (PA‐6), polyamide 6,6 (PA‐6,6), 33 wt% glass‐filled PA‐6,6 (33‐GF‐PA‐6,6), and amorphous polyamide (PA‐A) are assessed through 120 Hz vibration welds. Weld strengths equal to those of the base resins can easily be obtained in vibration welds of both undried and dried PA‐6 and PA‐6,6. Relative weld strengths in the range of 54–57% are demonstrated for 120 Hz welds of 33‐GF‐PA‐6.6. Relative weld strengths in the range of 90–97% are demonstrated for dried PA‐A. The highest relative weld strengths obtained in hot‐tool welds of undried and dried PA‐6,6 are only 57% and 54% respectively.     

On the Structure and Strength of Solvent-Welded Joints: The Intrinsic Joint Strength and the Effect of Dissolved Polymer in the Solvent Cement

It is proposed that the intrinsic strength of a solvent-welded joint can be represented by the magnitude of its critical principal strain. A large critical principal strain implied a high intrinsic weld strength. With poly(vinylchloride) adherends, solvent welds formed using pure tetrahydrofuran (THF) and cyclohexanone bonding solvents had high intrinsic joint strengths while solvent welds from pure methyl ethyl ketone (MEK) bonding solvent had lower intrinsic joint strength. In the THF bonding system, the introduction of dissolved polymer in the bonding agent led to significant decreases in the strength of the solvent-welded joint. Additions of up to 2% by weight of dissolved polymer in the MEK bonding agent increased the strength of the solvent weld. However, further increases in the dissolved polymer content in MEK bonding agent also led to decreases in strength.     

Vibration welding of thermoplastics. Part I: Phenomenology of the welding process

In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters in vibration welding are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time. How these parameters affect weld quality, the conditions that result in the best welds, the weldability of dissimilar plastics, and the effect of fillers such as glass are of interest. To address these issues, a research vibration welding machine in which all the parameters can be independently and accurately controlled and monitored was designed and fabricated. The phenomenology of welding, as determined by experiments on the four thermoplastics polycarbonate, poly (butylene terephthalate), polyetherimide, and modified poly (phenylene oxide), is described.     

On the Structure and Strength of Solvent-Welded Joints: The Intrinsic Joint Strength and the Effect of Dissolved Polymer in the Solvent Cement

It is proposed that the intrinsic strength of a solvent-welded joint can be represented by the magnitude of its critical principal strain. A large critical principal strain implied a high intrinsic weld strength. With poly(vinylchloride) adherends, solvent welds formed using pure tetrahydrofuran (THF) and cyclohexanone bonding solvents had high intrinsic joint strengths while solvent welds from pure methyl ethyl ketone (MEK) bonding solvent had lower intrinsic joint strength. In the THF bonding system, the introduction of dissolved polymer in the bonding agent led to significant decreases in the strength of the solvent-welded joint. Additions of up to 2% by weight of dissolved polymer in the MEK bonding agent increased the strength of the solvent weld. However, further increases in the dissolved polymer content in MEK bonding agent also led to decreases in strength.     

Influence of the Bonding Solvent on the Structure and Strength of Solvent Welded Joints

The influence of the bonding solvent on the strength of solvent welded joints has been studied. Strong solvent welds are produced with solvents having the greatest ability to dissolve the polymer and not with solvents which could diffuse most rapidly into the adherend. The formation of a gel layer of highly mobile chains (on the application of a good solvent to the mating surfaces) promotes extensive and intimate bonding across the original interface so that no plane of weakness is obtained. Such welds exhibit high strength since they do not have any preferred plane of failure and extensive deformation of the weld accompanies crack initiation and propagation. When a poorer bonding solvent is used, solvent welds with lower strengths are obtained since soft and weak interfacial layers form at the original interfaces of the weld.