science

Phthalates

Phthalates is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Phthalates rather than just read about it. In short: Phthalates (US: UK: THAL-ates ), or phthalate esters, are esters of phthalic acid. They are colorless, odorless, oily compounds, although commercial samples can be yellowish with faint odors.

Key takeaways

Phthalates belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Phthalates to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Phthalates from memory before moving on to harder problems.

Reference excerpt

Phthalates (US: UK: THAL-ates ), or phthalate esters, are esters of phthalic acid. They are colorless, odorless, oily compounds, although commercial samples can be yellowish with faint odors. Being fairly chemically inert and easily produced, they are widely used as plasticizers, i.e., substances added to polymers to increase their flexibility, transparency, durability, and longevity. They are used primarily to soften polyvinyl chloride (PVC). While phthalates are commonly used as plasticizers, not all plasticizers are phthalates. The two terms are specific, unique, and not used interchangeably. The use of phthalate plasticizers has had a profound effect on the commercialization of PVC, promoting its use for major industrial and consumer applications where flexibility is required, such as for tubing, siding, packaging and wire sheathing. Phthalates are controversial because, when ingested, they pose a threat as endocrine disruptors. Consequently their use is regulated, e.g. in the United States, Canada, and European Union.

Production Phthalate esters are produced industrially by the reaction of phthalic anhydride with excess alcohol. The monoesterification occurs readily, but the second step is slow:

C6H4(CO)2O + ROH → C6H4(CO2R)(CO2H) C6H4(CO2R)(CO2H) + ROH → C6H4(CO2R)2 + H2O The conversion is conducted at high temperatures to drive off the water. Typical catalysts are tin or titanium alkoxides or carboxylates. The properties of the phthalate are affected somewhat by the alcohol. Around 30 are, or have been, commercially important. Phthalates' share of the global plasticisers market has been decreasing since around 2000, but total production has been increasing, with around 5.5 million tonnes made in 2015, up from around 2.7 million tonnes in the 1980s. This increase is due to the increasing size of the plasticiser market, largely due to increases in PVC production, which nearly doubled between 2000 and 2020. The People's Republic of China is the largest consumer of phthalates, accounting for around 45% of all use. Europe and the United States together account for around 25% of use, with the remainder widely spread around the world.

Uses

PVC plasticisers

Between 90 and 95% of all phthalates are used as plasticisers for the production of flexible PVC. The majority is used in films and cable sheathing. Flexible PVC can consist of over 85% plasticizer by mass, however unplasticized PVC (UPVC) should not contain any. Pthalates were the first commercially important compounds for this role, a historic advantage that has led to them becoming firmly embedded in flexible PVC technology. Among the common plastics, PVC is unique in its acceptance of large amounts of plasticizer with gradual changes in physical properties from a rigid solid to a soft gel. Phthalates derived from alcohols with 7–13 carbon atoms occupy a privileged position as general purpose plasticizers, suitable for almost all flexible PVC applications. Phthalates larger than this have limited compatibility in PVC, with di(isotridecyl) phthalate representing the practical upper limit. Conversely, plasticizers derived from alcohols with 4–6 carbon atoms are too volatile to be used on their own, but have been used alongside other compounds as secondary plasticizers, where they improve low-temperature flexibility. Compounds derived from alcohols with 1–3 carbon atoms are not used as plasticizers in PVC at all, due to excessive fuming at processing temperatures (typically 180–210 °C). Historically DINP, DEHP, BBP, DBP, and DIHP have been the most important phthalates, however many of these are now facing regulatory pressure and gradual phase-outs. Almost all phthalates derived from alcohols with between 3 and 8 carbons are classed as toxic by ECHA. This includes bis(2-ethylhexyl) phthalate (DEHP or DOP), which has long been the most widely used phthalate, with commercial production beginning in the 1930s. In the EU, the use of DEHP is restricted under REACH and it can only be used in specific cases if an authorisation has been granted; similar restrictions exist in many other jurisdictions. Despite this, the phase-out of DEHP is slow and it was still the most frequently used plasticizer in 2018, with an estimated global production of 3.24 million tonnes. DINP and DIDP are used as a substitutes for DEHP in many applications, as they are not classified as hazardous. Non-phthalate plasticizers are also being increasingly used.

Non-PVC plasticisers Phthalates see use as plasticisers in various other polymers, with applications centred around coatings such as lacquers, varnishes, and paints. The addition of phthalates imparts some flexibility to these materials, reducing their tendency to chip. Phthalates derived from alcohols with between 1–4 carbon atoms are used as plasticisers for cellulose-type plastics, such as cellulose acetate, nitrocellulose and cellulose acetate butyrate, with commonly encountered applications including nail polish. Most phthalates are also compatible with alkyds and acrylic resins, which are used in both oil and emulsion based paints. Other plasticised polymer systems include polyvinyl butyral (particularly the forms used to make laminated glass), PVA and its co-polymers like PVCA. They are also compatible in nylon, polystyrene, polyurethanes, and certain rubbers; but their use in these is very limited. Phthalates can plasticise ethyl cellulose, polyvinyl acetate phthalate (PVAP) and cellulose acetate phthalate (CAP), all of which are used to make enteric coatings for tablet and capsule medications. These coatings protect drugs from the acidity of the stomach, but allow their release and absorption in the intestines.

Solvent and phlegmatizer Phthalate esters are widely used as solvents for highly reactive organic peroxides. Thousands of tonnes are consumed annually for this purpose. The great advantage offered by these esters is that they are phlegmatizers, i.e. they minimize the explosive tendencies of a family of chemical compounds that otherwise are potentially dangerous to handle. Phthalates have also been used for producing plastic explosives such as Semtex.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Phthalates

Start with the simplest possible case. Write down what Phthalates claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Phthalates before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Phthalates ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Phthalates

In research: Phthalates appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Phthalates in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Phthalates is common in secondary-school and first-year university syllabi. It links to neighbouring topics Endocrine disruptors, Phthalates, Plasticizers, so understanding it makes those chapters shorter.
In everyday life: Look for Phthalates outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Phthalates in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Phthalates means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Phthalates out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Phthalates in simple terms?

Phthalates (US: UK: THAL-ates ), or phthalate esters, are esters of phthalic acid. They are colorless, odorless, oily compounds, although commercial samples can be yellowish with faint odors.

Why does Phthalates matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Phthalates?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Phthalates.