Kinetics Study And Optimization Of Bisphenol A

Published Date: 02 Nov 2017

1.0 INTRODUCTION

With the increase in daily products of plastics, the importance of biphenols has also amplified continually with the development of plastics Industry. Bisphenol A or 4,4 - Isoproppylidene Diphenol, also abbreviated as BPA being the most frequently used Biphenols, is a vital mediator for high-grade thermosets, thermoplastics, and as a raw material in the manufacture of epoxy resins and polycarbonates resins (Rahimi et al. 2001). Bisphenol A is a solid compound with white to brownish yellow colour, based on its purity and phenol odour or hospital odour. (Uglea et. al, 1991).

Stephen et al. (1998), opine that Polycarbonate is an engineering thermoplastic which is well known for its wonderful blend of hardiness, lucidity and heat resistance. The use of Bisphenol A in plastics Companies cannot be over emphasized with its wide spread use in canned or bottled foods and drinks, baby bottles, eye glasses, medical and dental devices, CD lenses, adhesives etc. Polycarbonate plastics have several applications which include food and drink packaging, for example water bottles, impact-resistant safety equipment. Bisphenol A is also known for its use in antioxidant for brake fluids and as an additive for PVC-resins, oxo-alcohols. Brotons et al. (1995), submit that BPA has been found in the liquor from canned food packed in lacquer-coated cans. It is also used as fungicide. (Rahimi et al., 2001).

In spite of all these applications, the general demand for Bisphenol A, Polycarbonate and epoxy resin has amplified with the economy. For that reason, according to early prospect, the use of plastics has already surpassed that of metals in the 1970s, while annual growth rate reached 3% - 4%. During 1940 to 1994, the production capacity of plastics in the U.S. improved from 45,000 tons to 36 million tons per year. Universal use has reached about 110 million tons (money value of $200 billion), whereas the hope for the year 2000 is approximately 170 million tons (Fred, 1995). The general strength of the world wealth will persist to play a key role in the future demand for Bisphenol A, as its key end-user includes automotive, construction and electrical/electronic applications.

Various methods have been employed to synthesize Bisphenol A. One procedure is the production of BPA reported by (Takenaka et al., 1967) where he suggested the anionic mechanism for the reaction of phenol and acetone under a low pressure of hydrogen chloride to give BPA . Schnell (1963) has also presented mechanism for the alkaline Condensation of phenol with acetone. The use of Bisphenol A cannot be over emphasized in a developing country like Nigeria as it has been found in ATM (Automated Teller Machine) receipt paper, compact disc, can drinks and stockings, shirts, windbreakers, pyjamas, processed nylon and so on (Lauren, 1999). With revere to the statement above, there will arise more demands on the products of Bisphenol A i.e. polycarbonate plastics and epoxy resins in Nigeria and the whole Diaspora. In this paper however, we discuss the kinetics and Optimization aspects of condensation reaction of acetone with phenol in presence of Acid as catalyst.

AIM & OBJECTIVES

The aim of this work is to present a detailed description of the study of kinetics and optimization of Bisphenol A from condensation of phenol and acetone in the presence of an Hydrochloric Acid (HCL) as a catalyst. This can be achieved through:

Produce Bisphenol A at an optimum condition.

Characterize the Bisphenol A produced.

Study the kinetics of reaction and to know the order of reaction.

Scope Of Work

The approach is a laboratory study of kinetics and optimization of Bisphenol A production with a consideration of its suitability for the production of polycarbonates plastics and epoxy resins.

Significance Of The Work

Economic Justification Of The Work

Bisphenol A is a major component in the production of polycarbonates plastics and Epoxy resins. Thus, the production of Bisphenol A will make it readily available and useful for a developing country like Nigeria, thus production of Bisphenol A will be highly economical.

2.0 LITERATURE REVIEW

2.1 Background

Bisphenol A has been in use for over 50years. It was first produced by Dianin in 1891 but saw small use until the 1930s when it was used as an artificial estrogen product. BPA has mainly two large phenyl groups as well as two electron-rich hydroxyl groups and two- methyl. Balin et al. (2008), reported that BPA is high volume producing compound which defines that it is produced globally. In 1936, BPA was confirmed as an estrogenic drug relative compound by Dodds and Lawson. Chemist ignored these result and BPA was yet to be used in the 1950s as the monomer to manufacture polycarbonates plastics, epoxy resins and as a chemical additive (plasticizer) in polyvinylchloride (PVC) plastic, as well as it is used in lots of other products, such as the coating (developer) in receipt tabloid (Vom Saal et al. 2011). Haishima et al. (2001) established BPA to be a constituent of many medical products, as well as hemodalyzer and medical tubing (Kanno et al. 2007) and patient can be exposed to lofty levels of BPA for medical treatments (Calafat et al., 2009).

Frequently, one hears BPA is a feeble estrogenic chemical and it has lesser strength than estradiol in some vitro assay systems (Welshons et al., 2003). The properties of BPA were investigated in 1930 and 1950s as polycarbonate and epoxy resins. As at now BPA is commonly used as a constituent in plastic bottles and the inside lining of cans. Scientists revealed that Bisphenol A, produce an apparent, hard plastic called polycarbonate when joint with the gas phosgene used in eyeglasses, baby bottles, shatter-resistant lights and lots of other applications. (bookshop.europa.eu/Bisphenol A).

The outcome of exposure of Bisphenol A can have an effect on fetus, infants, and young children, owing to the statement that there is lack of response regulating the activity, production, and removal of hormones. Even though dangerous effect of BPA on human ovum cells have not yet been recognized, the processes involved in the creation of ovum cells in humans and mice are similar, so one might for see the BPA is very dangerous for human also Groshart et al., (2001) found BPA non biodegradable. The main means by which the people are exposed to BPA is through leaching from plastic products. This however results from either the release of unpolymerized monomers or the slow decay of polymer bonds in polycarbonates leading to monomer release into proximal foods and liquids. Stephen et al., (2011).

The conclusion that BPA should not be considered to act only as an estrogen, or even as a Selective Estrogen Receptor Modulator (SERM), is supported by a number of proof, including in vitro and other types of mechanistic studies published in the peer-reviewed literature (Wetherill et al., 2007; Chapin et al., 2008), results of the United States Environmental Protection Agency’s (USEPA) high-throughput screening (HTS) programme conducted through the initiative and comparisons of gene expression

2.2 Production of Bisphenol A

Bisphenol A is produced by the condensation reaction of phenol and acetone in the presence of an acid (HCL). The reaction of acetone with phenol for the production of BPA is normally performed in the presence of a strongly acidic substance, such as hydrochloric acid, sulphuric acid. These acidic substances, however, serve to ease the production of coloured substances and impurities at a high temperature and thereby reduce the purity of the BPA product. Hence, after the conclusion of the BPA production, the acid catalyst is commonly neutralized or removed from the reaction mixture so as to avoid the presence in the subsequent phenol. Schnell et al. (1963).

The removal of the acidic substance or the remaining alkali from the reaction product can be performed in the following crystallization step in which BPA produced is crystallized as adduct with phenol. Tekenaka et al. (1967).

The condensation reaction of phenol and acetone is shown as thus below:

2C6H5OH + H3C–C–CH3 → HO – C6H4 –C - C6H4-OH + H20

Commercial production of BPA is largely by distillation, that is, solvent based extraction using additional phenol followed by distillation. (Schnell, 1963).

2.2.1 Phenol

Phenol is obtained from coal tar and is broadly used as a disinfectant for industrial and medical uses. It also serves as a chemical intermediate for manufacture of nylon and other man-made fibers and for manufacture of epoxy and other phenolic resins and as a solvent for petroleum refining. Its consumption in the United States of America is directly related to the housing and construction industries, in applications such as germicidal paints and phenol are present in the atmosphere as an emission from motor vehicles. (CARB, 1999).

The properties of phenol is given in table 2.0 below (HSDB, 1995, 1999; ATSDR, 1989)

Description Colourless to light pink solid

Molecular formula C6H5OH

Density 1.0576 g/cm3 @ 20° C

Boiling point 181.75° C

Melting point 40.9° C

Solubility 86,000 ppm in water, very soluble in

alcohol, Slightly soluble in benzene

2.2.2 Acetone

Acetone is the organic compound. This colourless mobile flammable liquid is the simplest example of the ketones. Owing to the fact that acetone is miscible with water, and almost all organic solvents this makes it appropriate for use as a solvent (Krasavage et al. 1982). Because of its ability to go through addition, oxidation/reduction, and condensation reactions, acetone is used as a raw material in the chemical synthesis of many commercial products (Nelson and Webb 1978).

The properties of acetone is given in table 2.1 below (HSDB 1992 and Riddick et al. 1986).

Chemical formula C3H6O

Colour colourless

Boiling point 56.2°C

Density 0.78998g/ml at 20°C

Solubility completely soluble

2.2.3 Derivative of Bisphenol

Two derivatives of BPA, bisphenol diglycide ether (BADGE) and bisphenol F diglycide ether (BFDGE), both are of high industrial importance. BADGE is the major compound used in the production of epoxy resins that is used for inner coating of food-product covering. It has been estimated that approximately 75% of the epoxy resins at present have been produced using BADGE. This compound is also used as a glaze to coat the inside walls of cans and other containers used to store food products. Their most threatening effect is initiation of genetic diseases in children of humans exposed to their activity. (Wasaik et al., 2006).

2.2.4 Properties of Bisphenol

Structure of Bisphenol A is shown below:

(Wasaik et al., 2006).

The table below shows the properties of Bisphenol A:

Table 2.2: Properties of Bisphenol A (ASTM)

Properties

Molecular formula

C15H16O2

Density

1.20 g/cm3

Appearance

White to light brown flakes

Melting point

158 to 159 0C

Boiling point

220 0C

Solubility in water

120-300 ppm (21.5 0C)

Flash point

227°C(441°F)

2.2.5 Kinetics Study and Optimization of Bisphenol A

Kinetics and optimization of Bisphenol A is the study of reaction rate and to vary parameters such as temperature, concentration, and time to have an optimum yield of Bisphenol A and good quality. The effect of temperature, concentration, and catalyst on bisphenol A production has been carried out by (Azam Rahimi et al., 1998) where a sequence of experiments were carried out at different temperature, while concentration of reactants (phenol and acetone) were reserved stable. The reaction mixture was stopped by immersing it in cold water after exact period of time. The results of the first sequence of experiments were carried out in the presence of a promoter. The BPA yield shows positive temperature dependence in the range of 40-60 ° C, and above 60° C, the conversion product is white at 60° C, which is an indication of its high quality and turns yellow above this temperature which needs further treatment. In the absence of promoter, the BPA yield increases with temperature within the range of 40-70° C but the colour turns yellowish with increasing temperature. At temperature of 60° C, with promoter, the BPA yield reached about 87% in 8h, the BPA is only 72% in the absence of a promoter. Rahimi (1998) also reported that at 70°C the yield of BPA in the presence of a promoter is higher, but because of the by-products traces the quality of BPA is not so good and it turns yellow, which is an indication that the temperature should not be so high when using a promoter.

Rahimi et al., (2001), further discussed the effect of concentrations of reactants, phenol: acetone which has significant effect on the BPA yield and a 90% yield has been obtained by reaction of 3 moles of phenol with 1 mole of acetone with the aid of a promoter. When phenol acetone yield is reduced, the yield also dropped and the colour of the product changed from white to dirty yellow. The concentration of acid catalyst used for a highest yield of BPA is found to be at ratio of 1 for each mole of acetone. For an optimum yield of BPA with good quality, a reaction time of 6h, at 60° C viz:

A plots of yield (R%) in the form of:

-log (100-R)/100 = kt (1)

This relation gives straight lines in the range of 60-90% conversion in which the phenol concentration is constant, and in this condition a simple kinetics expression for the reaction rate (v) of BPA formation is derived and reduced to observed first order reaction in acetone.

V = k'{A} {C + C’ {T}} (2)

Where A and T are the concentration of acetone and Hydrochloric acid and k', C, C' are constants. These results confirm the picture of bisphenol A formation. The operating conditions of variables and expressed the yield-time relationship for all variables fixed at the maximum yield level as the following equation which is in better agreement with experimental data:

X = 1- (1+0/03t)-2/0

Where X is the fraction conversion of the limiting component (mol/mol).

The plot of the yield (R %) in the form of equation (1) give a straight line in the range of 60–90% which conform to a first order reaction (De jong et al., 2008). From the literature review, a first order reaction has been obtained from the kinetics study of BPA production. This is a plot of yield against time.

2.2.6 Identification in plastics

There are seven classes of plastics. Presently there are no BPA labeling needs for plastics. In general, plastics that are marked with resin identification codes 1, 2, 3, 4, 5, and 6 are very unlikely to contain BPA. Some, but not all plastics that are marked with the resin identification code 7 may be made with BPA. Type 7 such as polycarbonate (sometimes recognized with the letters ‘PC’ and epoxy resins, are made from bisphenol A monomer. Type 3 PVC also may include bisphenol A as an antioxidant in plasticizers. This refers to flexible PVC, but not for rigid such as pipe, windows, and sliding. (bookshop.europa.eu/Bisphenol A).

2.2.7 Application of Bisphenol A

Bisphenol A is used mostly to make plastics and products containing bisphenol based plastics.

It is a key monomer in manufacture of epoxy resins and generally in polycarbonate plastic. Polycarbonate plastic, which is clear and nearly shatter-proof, used to make a variety of common products.

BPA is also used in the synthesis of polysulfones and polyether ketones, as an antioxidant in some plasticizers, and as a polymerization inhibitor in PVC.

Epoxy resins containing bisphenol A are used as coatings on the inside of almost all food and beverage cans.

Bisphenol A is also a precursor to the flame retardant tetrabromobisphenolHYPERLINK "http://en.wikipedia.org/wiki/Tetrabromobisphenol_A" A, and was formerly used as a fungicide.

Bisphenol A is a preferred color developer in carbonless copy paper and thermal paper, with the most common public exposure coming from some thermal point of sale receipt paper. (bookshop.europa.eu/Bisphenol A.)

2.3 Environmental Impact of Bisphenol A

Bisphenol A is formed by the condensation of phenol with acetone; which tends to have low vapour pressure, high melting point and moderate solubility (Cousins et al., 2002; Howard, 1989; Shareef et al., 2006). It is thus expected to have low volatility. Cousins et al., 2002; Howard, 1989 reported that less than 1% of environmental BPA is thought to occur in the atmosphere, and it is believed to photo-oxidize and breakdown in a faster way.

In general, studies have shown that BPA can affect growth, reproduction and development in aquatic organisms. The first studies were conducted in 1930s which was studied by ( Dodds and Lawson 1936) and confirmed the estrogenecity of bisphenol A.

Endocrine societies as well as other medical societies also identify the need for a change in the assumptions used in traditional chemical risk assessments (Diamanti-Kandarakis et al., 2009: Hunt 2011). In particular, the endocrine society recommended advised that 21st approaches and knowledge about endocrine active compounds should be taken into consideration when assessing the hazards as a result of endocrine disrupting chemical such as BPA (Vom Saal et. al., 2011). In contrast, for endocrine active chemicals, such as BPA, that can alter critical cell signalling pathways, virtually there is no dose that does not pose some risk (Myers et al., 2009a; Myers et al., 2009b; Vom Saal and Sheehan 1998).

Evidence have shown effects on fish, aquatic invertebrates, amphibians and reptiles which has been reported at environmentally relevant exposure levels lower than those required for acute toxicity.

Richter et al., 2007 also reported that there are many studies showing effects of exposure to BPA in adults. Adult exposures to BPA is an environmental contaminant, with the results showing BPA is detected on 93% of adults in the United States of America based on the National Health and Nutrition Examination Survey and Prevention (Calafat et al., 2008). However, a recent study reported by Alonso-Magdalena et al., (2010) that even with a short-term exposure to very low doses of BPA in adult mice led to subsequent metabolic abnormalities, including increased body weight, higher plasma insulin, leptin, triglyceride, and glycerol levels and greater insulin resistance. While human exposure is said to occur when exposure to BPA is due to its use in food packaging (Munckle 2011), non-food sources also contribute to BPA in the general population (Stahlhut et al., 2009), which may be as result of other sources. One of the most vulnerable problems resulting from BPA exposure is pregnant mothers and newborns. Ramakrish and Wayne, (2007) discuss how BPA has been detected in various amniotic fluid, material, fetal plasma placenta, and breast milk.

Table 2.3: show effect of BPA on mice, rats and human. (Vom Saal et al., 2011):

BPA effects in mice and rats Human health trend

Cancer

Prostate hyperplasia and cancer Prostate cancer increase

Mammary hyperplasia and cancer Breast cancer increase

Male and female reproductive system

Abnormal urethra / Obstruction Hypospadias increase

Sperm count decrease Sperm count decrease

Early puberty in females early sexual maturation increase

ovarian cysts / uterine fibroids PCOS / Uterine fibroids increase

Abnormal oocyte chromosomes Miscarriage increase

Metabolic disease

Body weight increase Obesity increase

Insulin and glucose increase Type 2 diabetes increase

Brain and behavior

2.3.1 Health Effects

Bisphenol A has been found to be an endocrine disruptor, which can mimic the Body’s own hormones and may lead to negative health effects. Virtually all people have measurable amounts of BPA, since this chemical readily leaches out of products that contain it. The alteration of BPA with the programming of the genes that is critical for the normal development and adult functioning of numerous organ systems made BPA a very dangerous chemical as reported by Von Saal et al., (2011). More specifically, Bisphenol A closely mimics the formation and purpose of the hormone estradiol with the capability to bind to and set off the same estrogen receptor as the natural hormone. (bookshop.europa.eu/Bisphenol A).

Bisphenol A (BPA) is one of the industrial compounds that have generated concerns, due to their lofty production and wide extend of use. BPA is found in the saliva collected from subjects treated with dental sealants (Olea et al., 1996). Regulatory bodies have determined safety levels for humans, but those safeties levels are currently being questioned or under review as a result of new Scientific studies.

Questions regarding the safety and side effects of BPA began to emerge in the late 1990s when BPA was found to leech out of plastics and into experimental animal subjects,

resulting in an increased incidence of chromosomal anomalies in offspring. Stephen et. al., (2011)

Table 2.4 (adapted from the national toxicology program expert panel).

Population Estimated daily bisphenol A, μg/kg/day.

Infant (0-6 months) 1-24

Formula – fed

Infant (0-6 months) 0.2-1

Breast – fed

Infant (6-12 months) 1.63-13

Child (1.5-6years) 0.043-14.7

Adult 0.008-1.5

2.3.2 Studies on Human

The first large study of health effects on humans associated with Bisphenol A exposure was in the journal of America Medical Association. The cross-sectional study of almost assessed exposure to Bisphenol A by looking at levels of the chemical in urine.

Scientist found that higher Bisphenol A levels were significantly associated with heart disease, diabetes, and abnormally high levels of certain liver enzymes (Iain Lang et. al., 2008). The level of BPA detected in urine (as part of the NHANES 2003/2004 study) was related to serum glucose, insulin, insulin resistance and type 2 diabetes (Lang et al. 2008). There is extensive evidence from experimental animal studies relating acute BPA exposure to elevated serum insulin, elevated serum glucose and glucose resistance (Alonso-Magdalena et al., 2011). The mechanistic findings identifying the molecular pathways by which BPA stimulates an increase in pancreatic beta cell insulin secretion as well as an increase in insulin resistance (Hugo et. al., 2008).

2.3.3 Sexual Difficulties

Colborn et. al., (1993); Danzo, (1998); and Rajesh, (1999) discussed the environmental effects of some chemical which tends to affect sexual life and development of laboratory animals, posing a high risk on the reproductive abnormalities in wildlife and human populations. They may have such disruptive effects by disturbing the normal function of the gonadal steroid hormones that are necessary for normal sexual development. For example, recent in vitro (Sohoni and Sumpter, 1998) and in vivo (Takahashi and Oishi, 2001), studies of endocrine disrupters suggest that environmental antiandrogens receptor may also be a source of abnormal development of the male sex. Hyun Ju Lee et. al., (2003), explained Androgens are necessary for normal male sexual development and reproduction. An analysis of Chinese employees in factories where BPA and epoxy resins are produced, for example, revealed that over 90% of exposed workers have notable levels of BPA in their serum and urine Stephen et. al., (2011).

2.4 Epoxy Resins

Epoxy resins are polyether resins containing more than one epoxy group capable of being converted into the thermoset form. These resins, on curing, do not create volatile products in spite of the presence of a volatile solvent. The epoxies may be named as oxides, such as ethylene oxides (epoxy ethane), or 1,2-epoxide. The epoxy group also known as oxirane contains an oxygen atom bonded with two carbon atoms, which in their turn are bound by separate bonds. The simplest epoxy resin is prepared by the reaction of bisphenol A (BPA) with epichlorohydrine (ECH). There are three important methods of producing epoxides. First is catalytic epoxidation. Here the oxidation of olefins is carried out by directly oxidizing them in the vapour phase in the presence of a catalyst such as silver. Second is epoxidation by organic peroxides and their esters.. (Bhatnagar 1996).

2.4.1 Applications

The application of epoxy resins has also been studied by M. S. Bhatnagar 1996 which is as thus below:

Foams

Epoxy resins are used to form rigid, lightweight, foamy structures with good insulation properties. They are particularly used for foam-in-place applications in the "potting" process, as well as in casting. They are produced either by chemical reaction or by incorporating pre-foamed filler in the liquid system.

Adhesives

The versatile properties of epoxy resins make them valuable as adhesives. About five percent of total epoxy resin production is consumed as adhesive in a wide range of structural applications. Epoxy resin adhesives form strong bonds with almost all surfaces, with the exception of some non polar substrates. Very often special modifiers and curing agents must be used to produce specific properties. The formulation of epoxy adhesives into a serviceable adhesive binding system is a highly specialized technology. Adhesives based on epoxide resins are available as room-temperature-curing two-component liquids, heat-curing liquids, powders, hot-melt adhesives, films, and tapes. Adhesive formulation based on epoxy resins requires a wide variety of curing and modifying agents.

Construction

Epoxy resins are now used as binders in materials for construction. Generally, a two-component system containing liquid epoxy resin, diluents, fillers, thickening agents, and curing agents is used. They are used to bond concrete, and to produce industrial seamless thin-set tarrazzo floors. This use has been extended to the laying of roads, construction of buildings, and filling cracks in concrete structures.

2.5 Polycarbonate Plastics

Polycarbonates are tough, dimensionally stable, transparent thermoplastic that has many applications which demand high performance properties. They are characterized by outstanding mechanical, optical and thermal properties and have a wide range of applications. Aromatic polycarbonates derived from bisphenol A have been extensively studied and found to be interesting because of their useful properties; such as rigid molecular structure, exceptional impact resistance, chemical and dimensional stability, toughness, optical clarity, and thermal stability. They also offer good fire resistance, dimensional stability, and high optical transparency opening the door for a wide range of industrial applications. Other properties such as modulus, dielectric strength and tensile strength are comparable to other amorphous thermoplastics at similar temperatures below their respective glass transition temperatures (Bassam et. al. 2010).

Low molecular mass grades are easier to mold than higher grades, but their strength is lower as a result. The toughest grades have the highest molecular mass, but are much more difficult to process. Unlike most thermoplastics, polycarbonate can undergo large plastic deformations without cracking or breaking. As a result, it can be processed and formed at room temperature using sheet metal techniques, such as bending on a brake. Even for sharp angle bends with a tight radius, no heating is generally necessary. This makes it valuable in prototyping applications where transparent or electrically non-conductive parts are needed, which cannot be made from sheet metal. Note that PMMA/Plexiglas, which is similar in appearance to polycarbonate is brittle and cannot be bent at room temperature (Volker Serini et al., 2000).

2.5.1 Applications

Niche Application

Polycarbonate, being a very useful material, has attracted myriad smaller applications. The use of injection molded drinking bottles, glasses and food containers is common, but the use of BPA in the manufacture of polycarbonate has stirred serious controversy leading to development and use of "BPA-free" plastics in various formulations.

Polycarbonate is commonly used in eye protection, and other equipment which involves the use of glass, but requires much higher impact-resistance. Many kinds of lenses are manufactured from polycarbonate, including automotive headlamp lenses, lighting lenses, sunglass/eyeglass lenses, swimming and SCUBA goggles, and safety glasses/goggles/visors including visors in sporting helmets/masks and police riot gear.

Due to the light weight of polycarbonate, electronic display screen can be manufactured for use in mobile and portable devices. Such displays include newer e-ink and some LCD screens, though CRT, plasma screen and other LCD technologies generally still require glass for its higher melting temperature and its ability to be etched in finer detail.

Bonding

Polycarbonate can be mechanically bonded by standard methods. It can also be cemented by using a solvent such as methylene chloride or adhesives such as epoxy and silicon.

Decorating

Polycarbonate products will accept painting, printing, or vacuum metalizing as decorating methods.

Over View Applications of Polycarbonate

Lenses

Face shields

Industrial equipment and housing components

Medical equipment components

Instrument components

Electrical insulators and connectors

Aircraft & Missile components

Jet pump impellers and diffusers