Plastic Injection Moulding Specialists. Est 1948.

HIPS – High Impact Polystyrene

Thermoplastic , Tougher than polystyrene. High Impact Polystyrene is particularly suitable for thermoforming, it is a tough, rigid material and its high impact strength means it can be guillotined, punched, routered or sawn without difficulty.

HDPE – High Density Polystyrene

LDPE – Low Density Polyethylene

ABS – Acrylonnitrile Butadiene Styrene.

S.B.Weston produce a considerable amount of moulded parts in this material due to its suitability for producing light ridgid mouldings which are often required in industries such as the automotive and electrical industry. While the cost of ABS is roughly twice the cost of producing propylene it is considered superior for its hardness, gloss, toughness and electrical insulation properties.

ABS/PC – Acrylonnitrile Butadiene Styrene Polycarbonate

An acetal is a molecule with two single bonded oxygens attached to the same carbon atom.

Traditional usages distinguish ketal from acetal (whereas the ketal has two carbon-bonded R groups, the acetal has one carbon-bonded R group as H-). Current accepted terminology classifies ketals as a subset of acetals.

The plastic known as acetal is a polyacetal.

Formation of an acetal occurs when the hydroxyl group of a hemiacetal becomes protonated and is lost as water. The carbocation ion that is produced is then rapidly attacked by a molecule of alcohol. Loss of the proton from the attached alcohol gives the acetal. Acetals are stable compared to hemiacetals but their formation is reversible as with esters. As a reaction to create an acetal proceeds, water must be removed from the reaction mixture or it will hydrolyse the product. The formation of acetals reduces the total number of molecules present and therefore is not favourable with regards to entropy. A way to improve this is to use an orthoester as a source of alcohol. Aldehydes and ketones undergo a process called acetal exchange with orthoesters to give acetals. Water produced along with the acetal product is used up in hydrolysing the orthoester and producing more alcohol to be used in the reaction.

Acetals are important in nature, for example in solution the most stable form of glucose is its cyclic hemiacetal and maltose is an acetal made from two glucose units. Acetaldehyde diethyl acetal is an important flavouring compound in distilled beverages.^[1]

Acetals are sometimes used as protecting groups for carbonyl groups in organic synthesis as they are stable with respect to hydrolysis by bases.

- Wikepedia

We are experienced in the way Polypropylene behaves when injection moulded and are able to design in features that will maximise the properties strengths and eliminate its weaknesses.

The shrinkage of Polypropylene is largely influenced by processing conditions, hence, ultra close dimensional tolerances on mouldings are difficult to achieve. On the other hand, for assembly purposes, the resilience and resistance to stress cracking of polypropylene diminish the need for close tolerances.

Polypropylene –S.B.Weston’s packaging and storage box production occurs in Polypropylene due to the materials resistance to fatigue, its light weight toughness, rigidity and excellent resistance to chemical attack or ‘leeching’ all of which which make it very suitable for our range of storage boxes.

Live plastic hinges are often made in polypropylene. The material is selected due to its resistance to corrosion and chemical leeching and its resilience towards most forms of physical damage such as impact and freezing.

S.B.Weston use three main grades in the production of our boxes: A Polypropylene Homopolymer for our Regular Boxes which while strong, is not impact resistant and becomes brittle in very low temperatures. A toughened Copolymer – our TOUGH Boxes – which is impact resistant even at low temperatures, but is a whitish semi-opaque color in its natural state. And a Random Copolymer which combines the improved toughness of the toughened copolymer with the transparency of the regular homopolymer.